Protein glycosylation represents a nearly ubiquitous post-translational modification, and altered glycosylation can result in clinically significant pathological consequences. Here we focus on O-glycosylation in tumor cells of mice and humans. O-glycans are those linked to serine and threonine (Ser/Thr) residues via N-acetylgalactosamine (GalNAc), which are oligosaccharides that occur widely in glycoproteins, such as those expressed on the surfaces and in secretions of all cell types. The structure and expression of O-glycans are dependent on the cell type and disease state of the cells. There is a great interest in O-glycosylation of tumor cells, as they typically express many altered types of O-glycans compared with untransformed cells. Such altered expression of glycans, quantitatively and/or qualitatively on different glycoproteins, is used as circulating tumor biomarkers, such as CA19-9 and CA-125. Other tumor-associated carbohydrate antigens (TACAs), such as the Tn antigen and sialyl-Tn antigen (STn), are truncated O-glycans commonly expressed by carcinomas on multiple glycoproteins; they contribute to tumor development and serve as potential biomarkers for tumor presence and stage, both in immunohistochemistry and in serum diagnostics. Here we discuss O-glycosylation in murine and human cells with a focus on colorectal, breast, and pancreatic cancers, centering on the structure, function and recognition of O-glycans. There are enormous opportunities to exploit our knowledge of O-glycosylation in tumor cells to develop new diagnostics and therapeutics.

Introduction to O-glycans

Glycans comprised of carbohydrates linked to proteins in glycoproteins, and lipids in glycolipids, have crucial and fundamental roles in basic biological functions, including protein folding, cell–cell adhesion, signaling, and cellular recognition events [1–14]. As a result, changes in glycan composition of cells often lead to changes in cellular functions and result in the development of disease pathology, demonstrated by blood cells in Tn syndrome, sepsis, autoimmune diseases, and cancer biology.

A key concept in glycobiology is that the plasma membrane of all cells consists of a dense, complex presentation of glycans, termed the glycocalyx, that includes glycoproteins and glycolipids [9]. In addition, glycosylation of intracellular proteins also occurs through the reversible addition of the monosaccharide N-acetylglucosamine (GlcNAc); such O-GlcNAc modifications along with protein phosphorylation regulate many intracellular signaling pathways [13]. A major component of the surface glycocalyx are O-glycans that are based on GalNAc in O-linkage to Ser/Thr residues of glycoproteins. Mucins represent the very largest membrane and secreted glycoproteins in animal cells and are a rich sources of O-glycans and Ser/Thr and proline (Pro) residues. Exciting recent studies have demonstrated that one or more O-glycans are commonly found on most glycoproteins that are secreted or surface-associated in mammalian cells [15].

An incredibly diverse array of O-glycan structures is generated by the concerted biosynthetic efforts of multiple glycosyltransferases (Figure 1). The O-GalNAc-type glycans have many critical biological functions within glycoproteins, ranging from structural to cell binding interactions, immune cell functions, and as the barrier functions of mucins. Many specific O-glycan structures have known functions, such as Lewis antigens, e.g. sialyl-Lewis x. While these glycans have known functions in normal cellular settings, some unusual O-glycans, e.g. Tn (CD175) and sialyl-Tn (STn, CD175s) antigens, have links to altered processes, including tumor development and metastasis. Specifically, altered O-glycans have been observed in multiple types of cancers.

O-Glycan biosynthesis in humans.

Figure 1.
O-Glycan biosynthesis in humans.

Typical O-GalNAc-containing O-glycans are generated by initial modification of serine or threonine residues by addition of GalNAc residues (termed the Tn antigen), then the addition of galactose (Gal) to generate common core 1 O-glycans (T antigen), which are precursors to core 2 and many other O-glycans. Alternatively, the Tn antigen may be modified in the GI tract by addition of N-acetylglucosamine to generate core 3 and core 4 O-glycans. Not all the O-glycans depicted here are generated in a single type of cell, as cell types differ in their expression of glycosyltransferases. Further enzymatic modifications can generate Lewis and sialyl-Lewis antigens [9].

Figure 1.
O-Glycan biosynthesis in humans.

Typical O-GalNAc-containing O-glycans are generated by initial modification of serine or threonine residues by addition of GalNAc residues (termed the Tn antigen), then the addition of galactose (Gal) to generate common core 1 O-glycans (T antigen), which are precursors to core 2 and many other O-glycans. Alternatively, the Tn antigen may be modified in the GI tract by addition of N-acetylglucosamine to generate core 3 and core 4 O-glycans. Not all the O-glycans depicted here are generated in a single type of cell, as cell types differ in their expression of glycosyltransferases. Further enzymatic modifications can generate Lewis and sialyl-Lewis antigens [9].

In this review, we will discuss studies on the O-glycan structures in three prevalent but distinct types of human adenocarcinomas—colorectal, breast, and pancreatic cancers—and methods used to identify O-glycans. We also compare known structures between human and mice, and we explore mouse models of these cancers relevant to O-glycans, along with the associated mucins and glycosyltransferases. We also discuss the opportunities for diagnostic and therapeutic avenues that target O-glycans.

Biosynthesis of O-glycans

O-glycans represent a major class of glycan structures and along with another major class that are linked to asparagine (Asn) residues (N-glycans), they represent the major forms of post-translational modifications of most proteins in the secretory pathway. The biosynthesis of the O-GalNAc glycans versus N-glycans are quite distinct. N-glycosylation is typically co-translational in the endoplasmic reticulum (ER) and occurs through the addition of a preformed 14-sugar lipid-linked donor to select Asn residues within the sequon -Asn-X-Ser/Thr-, where X = any amino acid except Pro. In contrast, O-glycosylation occurs via the enzymatic addition of single monosaccharides. The linking monosaccharide GalNAc is added directly to Ser/Thr/Tyr residues in glycoproteins within the Golgi apparatus from the nucleotide sugar donor uridine diphospho-GalNAc (UDP-GalNAc). This linking sugar is then commonly modified in all cells by the addition of galactose (Gal) from the donor UDP-Gal to create the disaccharide Galβ1-3GalNAcα1-O-Ser/Thr, known as core 1, which can be further modified to other glycan sequences (Figure 1). Such O-glycans and N-glycans can be further modified and extended within the Golgi apparatus to generate an incredible diversity of many tens of thousands different glycan structures, depending on the cell type or differentiation state. The resultant O-glycans on glycoproteins regulate signaling processes through direct and indirect actions, and altered O-glycan expression is invariably associated with pathology. Many tumor cells express altered N- and O-glycans as a result of the tumor microenvironment [16], mutations, or epigenetic alterations [2,4,11,17]. It should be noted there are other types of O-glycosylation, such as O-fucosylation, as found in Notch signaling pathways, and O-xylosylation as found in glycosaminoglycans/proteoglycans [9], but these are not discussed in this review.

O-GalNAc-based O-glycans are initiated by a family 20 polypeptide N-acetylgalactosaminyltransferases (ppGalNAc-Ts) located within the Golgi; residues are added to proteins, which are then further elongated, branched, and capped by many other Golgi glycosyltransferases [18]. There is no specific sequon recognized by the ppGalNAc-Ts, but Ser/Thr residues in proximity to Pro residues are typical sites for modification [18]. In normal cells, O-glycosylation proceeds to form complex, elongated, and often branched structures [19] (Figure 1). The most common first elongation step is the synthesis of the core 1 O-glycan structure. This step is catalyzed by a single enzyme, C1GalT1 (T-Synthase). This enzyme requires its chaperone, Cosmc (C1GalT1C1), for folding and activity. Acquired mutations in C1GalT1C1 in hematopoietic stem cells are the cause of Tn syndrome in patients [20]. As discussed below, mutations in or altered expression of Cosmc is associated with many human carcinomas. Other modifications, such as addition of GlcNAc to the Tn antigen can also occur to generate core 3 O-glycans, most commonly localized to the GI tract, and these can be modified to core 4 O-glycans. In all cases, the glycans from cores 1–4 may be further elongated and sulfated.

Methods of studying O-glycans

There are several strategies for identifying alterations in O-glycosylation found in human cancers, either from direct specimens or cancer cells grown in vitro. The approaches include affinity and specificity probes, physico-chemical techniques (including mass spectrometry [MS] and nuclear magnetic resonance [NMR] spectroscopy) with or without glycosidase pretreatment, metabolic-labeling with precursors, and indirect assessment by characterizing glycan recognition responses to altered glycosylation processes [21,1022]. The nature of analysis can encompass the identification of released glycans, glycopeptides, complete glycoproteins, and glycolipids [23].

Affinity probes include lectins and monoclonal antibodies to carbohydrate antigens, and these may be used separately or in concert. Historically, immunization of mice with tumor cells has resulted in the generation of many antibodies against glycan or glycopeptide epitopes including O-glycoproteins and O-glycans; examples of such epitopes include CA15-3 (MUC1), CA-125 (MUC16), B72.3/Tag-72 (STn), and CA19-9 (SLea) [24–28]. Indeed, most FDA-approved clinically useful tumor biomarkers, recognizable by specific monoclonal antibodies, are either glycans or glycoproteins, and many have been identified in this manner [29]. Importantly, monoclonal antibodies recognize glycan antigens containing between two and six monosaccharides, monosaccharide clusters, or monosaccharide peptide epitopes (including the Tn antigen), but single monosaccharides are typically not recognized, except within the context of polypeptide determinants [30].

Lectins, which are typically plant-derived and form multimeric units that can enhance the avidity of sometimes low-affinity glycan interactions, differ from monoclonal antibodies in that they are frequently polyreactive. Whereas monoclonal antibodies are often very specific, lectins tend to recognize related glycan structures or classes of glycans with graded affinity. More recently, lamprey-generated variable lymphocyte receptors (VLR)-Fcs which possess unique binding specificities have been used due to their glycan reactivity [10,31,32], and more are in development. Immunohistochemical and/or immunofluorescent staining directly on tissues represents an important application of affinity probes which permits the direct visualization of specific tumor antigens [23,33].

Binding assays including microarrays, flow cytometry, and enzyme-linked immunosorbent assay (ELISA), employ antibodies and lectins for the directed detection of glycans [23]. ELISA, an enzyme immunoassay with colorimetric detection of antigen–antibody binding, has been used in the detection of serum and tissue cancer markers; for example, ELISA has been used in colon cancer studies to detect elevated levels of serum galectin-2, -4, and -8 relative to healthy controls [34], as well as differential glycosylation of MUC1 and CEACAM5 glycoproteins in normal versus colon cancer mucosa [35,36]. ELISA has also been used in analyzing the effects of ST3 beta-galactoside alpha-2,3-sialyltransferase 3 (ST3Gal3) levels in breast cancer development [37] as well as analyzing serum levels of CA19-9 in pancreatic cancer [26]. Alternatively, flow cytometry offers a means for the investigation of antigen–antibody or antigen—lectin reactions in specific cell populations; this has been used to characterize expression patterns of glycan epitopes in colorectal cancer cells with alterations in the cellular machinery required for normal cell–cell adhesion [23,38]. MS has proven useful and sensitive in the mass profiling of glycan structures in complex tissue and serum samples which contain unknown compounds. The applications of matrix assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) in the identification of glycoconjugates are well-established. The analysis and localization of glycans within tissue specimens can be achieved using MALDI-imaging MS, and this may be enhanced by coupling to separation and purification techniques such as liquid chromatography [23,39].

Generally, the sequencing of glycans with physical methods such as MS requires a chemical or enzymatic release of glycans [40]. Unfortunately, no enzymes have been commercially available which permit the release of complex-type O-glycans from peptides, thus necessitating the use of inefficient chemical release techniques that can cause glycan degradation and an unfavorable signal-to-noise ratio in subsequent MS analysis [41]. This situation is in contrast with N-glycans, where specific endoglycosidases, such as PNGase F, permit the release of complex N-glycans directly from Asn residues to which they are linked [42]. The efficiency of N-glycan release using human and mouse materials is typically extremely high (>95%), but release by this enzyme can be inhibited if unusual modifications of the inner GlcNAc residue are present, other than typical α1,6-fucosylation [30,40,41].

The recent development of a cellular O-glycome reporter/amplification (CORA) method allows for bypass of the glycan release step and permits the amplification of the O-glycome directly from cultured cells. This technology features the addition of a peracetylated chemical O-glycan precursor (Ac3GalNAc-Benzyl[Bn]) which then crosses the plasma membrane before it is de-esterified, taken up by the Golgi apparatus, modified by glycosyltransferases, and secreted from the cell, and then subjected to purification and MS analysis [22].

CORA has been further modified for quantitative glycomics, resulting in a method termed isotopic labeling with cellular O-glycome reporter/amplification (ICORA); this technique uses a stable isotope labeled Ac3GalNAc-Bn O-glycan precursor containing a deuterated benzyl group weighing 7 Da more than its protonated equivalent [21]. Cells incubated with either Ac3GalNAc-BnH7 or Ac3GalNAc-BnD7 correspondingly secrete either light H 7 or heavy D 7 labeled Bn-O-glycans into their respective media such that following purification, permethylation, and analysis by MS, a 7 Da mass shift will permit relative quantification of the Bn-O-glycans secreted by cells incubated with the different isotope labeled O-glycan precursors. This approach has been used to define alterations in O-glycan biosynthesis and in the O-glycome itself in colorectal cancer [21], and can be applied to any type of living cell.

The results of analyzing O-glycans from multiple human and animal glycoproteins have documented the existence of hundreds of different O-GalNAc-based O-glycans [2,43,44], differing in size, sequence, degrees of sulfation, fucosylation, sialylation, and other modifications.

O-glycans in colorectal cancer (CRC)

Adenocarcinoma of the colon and rectum represents the fourth leading cause of cancer-related deaths in the world [45]. Early-stage colorectal cancer is amenable to surgical resection alone, while locally advanced rectal cancer requires neoadjuvant chemoradiation therapy prior to definitive surgery [46]. Regarding the survival of CRC if diagnosed early, while localized (Stage I) or locally advanced (Stage II) is quite high (90% at 5 years), this significantly declines if there has been progression to nodal involvement (Stage III) or widely metastatic (Stage IV) disease (14–71% at 5 years) [45]. Successful early detection and diagnosis of CRC is contingent upon patient compliance with regular colonoscopic screening; unfortunately, colonoscopic screening compliance in the U.S. is less than 65% and the frequency of Stage III and IV diagnoses among all CRC patients is 61% [45]. This highlights the high potential value of a sensitive screening biomarker for CRC, as currently one does not exist.

Given that abnormal O-linked glycosylation is presently regarded as the hallmark of a number of cancers, including colorectal cancer, and is believed to play a key role in tumorigenesis and metastasis, this represents an emerging area with excellent diagnostic and therapeutic potential [11,47]. Aberrant glycosylation in colorectal malignancy manifests as glycoproteins that demonstrate abnormal expression of aberrantly truncated O-glycans [21]. The O-glycans are thus quite abundant in the epithelial cell glycoproteins of the colorectum, which are known to be highly productive of mucins [10,48].

The profile of ppGalNAc-Ts responsible for O-glycosylation of mucins is also altered in colorectal cancer, as is the relative expression of the various mucin glycoproteins on which aberrantly truncated O-glycans are displayed [49,50]. In general, mucin O-glycans show increased expression of core 1 structures, which are often truncated, sialylated, or fucosylated, promoting tumor progression and metastasis [23].

These deranged glycosylation patterns have resulted in the establishment of various cancer-associated glycan and glycoconjugate antigens that represent clinically useful disease biomarkers for which the underlying mechanisms are still being elucidated [11,51].

Glycosyltransferase activities in CRC

Glycosyltransferases are the enzymes responsible for catalyzing glycosidic bond formation by transferring saccharide moieties from nucleotide sugars to acceptor molecules. A single glycosyltransferase, however, is often involved in a variety of glycosylation pathways [48,52] and may cross-over to function in glycosylation of N- and O-glycans and even glycosphingolipids. Frequently, altered protein glycosylation in cancer cells results from inappropriate expression levels of glycosyltransferases, altered subcellular localization of glycosyltransferases, and/or changes in bioavailability of protein substrates and/or essential enzymatic cofactors [9,11].

Eight of the ppGalNAc-Ts that initiate O-GalNAc O-glycosylation have been identified in the human colon, including GalNAcT-1, GalNAcT-2, GalNAcT-3, GalNAcT-4, GalNAcT-5, GalNAcT-7, GalNAcT-10, GalNAcT-12 [53]. The density of these ppGalNAc-Ts increases from proximal to distal along the colonic epithelium, implying a denser glycosylation pattern with higher mucin turnover distally. Based on the expression level and activity of each GalNAc-T, glycosylation may vary depending on the tissue type, and changes are noted in pathology.

Changes in the localization or in the activity of these ppGalNAc-Ts result in the synthesis of immature, aberrantly truncated core glycan structures [50,54]. For example, in healthy normal colorectal tissue, GalNAc-T6 is nearly absent; however, its expression is up-regulated in many CRCs. Transcriptional profiling in the colon adenocarcinoma cell line LS174T, and comparison to its counterpart LS174TΔT6 (which features a GALNT6 deletion and thus mimics normal colonic epithelium), demonstrates increased expression of stem cell markers and decreased expression of genes associated with differentiation and cell adhesion [55]. In the case of GalNAc-T12, DNA sequencing has detected eight functionally-inactivating germline and somatic mutations in both familial and sporadic CRC [56].

The expression of truncated O-glycan structures as well as aberrancies in fucosylation and sialyation in CRC may be attributable to additional alterations in glycosyltransferase activity [23]. In colon cancer cell lines, the overexpression and mis-localization to all Golgi cisternae of α-GalNAc α2,6-sialyltransferase I (ST6GalNAc-I), the enzyme responsible for STn biosynthesis, may disturb normal O-glycosylation by premature addition of sialic acid to form the STn antigen [54,57,58]. An increase in global sialylation, particularly in α2,6- and α2,3-linked sialylation, has been closely associated with various gastrointestinal cancers [59].

There remain patterns of change of specific glycosyltransferases in CRC, however, which are not yet explicable. For example, the T-synthase and its chaperone Cosmc, demonstrate increased expression at both the protein and mRNA level in CRC tissue relative to non-diseased colon, yet the tissues express the Tn antigen, which denote the lack of functionality or accessibility of the T-synthase toward those glycoprotein substrates [33]. Other studies have also indicated that overexpression of Cosmc is associated with malignancy in colon cancer [60] and this may be through activation of Akt and ERK signaling pathways [61]. Given the increased expression of Tn antigen in CRC, this pattern may suggest subcellular mis-localization of T-synthase and/or Cosmc with resulting activation of yet unelucidated up-regulation mechanisms [33].

Mutations in Cosmc (C1GalT1C1) are actually rather common in human tumors and are found in 1–6% human cancers, from examination of The Cancer Genome Atlas (TCGA) database [62]. While loss of Cosmc function can lead to Tn expression, the expression of the Tn antigen is much more common than Cosmc mutations in human cancers. Thus, the mechanisms of Tn expression include not only mutations in Cosmc, but also changes in Cosmc expression due to epigenetic silencing [63,64], and changes in expression or localization of different ppGalNAc-Ts [56,65].

O-glycan antigen expression in CRC

The O-GalNAc-type O-glycans are found in most transmembrane and secreted mucin glycoproteins in the colon [10]. The O-glycans found in colonic mucins consist of modified cores 1–4 (Figure 1 and Table 1). With malignant transformation, however, colonic mucins exhibit specific alterations, such as reduced core 3 and core 4 structures [50,66]. Additionally, glycosylation changes present as aberrant expression of truncated glycans on mucin glycoproteins, including the T or TF (Thomsen–Friedenreich) antigen, the Tn antigen, and their sialylated counterparts sialyl-T antigen and STn antigen [10].

Table 1
O-GalNAc glycan cores and antigenic epitopes (Adapted from Essentials of Glycobiology [9])
Glycan coreRelated cancer and references
 Tn antigen (CD175) GalNAcαSer/Thr Breast, colorectal, pancreas [10,33,63,64,67–75
 Sialyl-Tn antigen (CD175s) Siaα2-6GalNAcαSer/Thr Breast, colorectal, pancreas [10,33,58,64,67,74,76–79
 Core 1 or T antigen Galβ1-3GalNAcαSer/Thr Breast, colorectal [10,23,33,67,80–83
 Core 2 GlcNAcβ1-6(Galβ1-3)GalNAcαSer/Thr  
 Core 3 GlcNAcβ1-3GalNAcαSer/Thr Colorectal [23
 Core 4 GlcNAcβ1-6(GlcNAcβ1-3)GalNAcαSer/Thr Colorectal [23
Glycan epitope 
 Blood group H Fucα1-2Gal-  
 Blood group A GalNAcα1-3(Fucα1-2)Gal-  
 Blood group B Galα1-3(Fucα1-2)Gal-  
 Linear blood group B Galα1-3Gal-  
 Blood group i Galβ1-4GlcNAcβ1-3Gal-  
 Blood group I Galβ1-4GlcNAcβ1-6(Galβ1-4GlcNAcβ1-3)Gal-  
 Blood group Sd(a), Cad GalNAcβ1-4(Siaα2-3)Gal- Mouse specific glycan 
 Lewis a Galβ1-3(Fucα1-4)GlcNAc- Colorectal, pancreas [26,84
 Lewis x Galβ1-4(Fucα1-3)GlcNAc- Colorectal [84
 Sialyl-Lewis x Siaα2-3Galβ1-4(Fucα1-3)GlcNAc- Breast, colorectal [37,85–91
 Lewis y Fucα1-2Galβ1-4(Fucα1-3)GlcNAc- Colorectal [92,93
 Sialyl-Lewis a Siaα2-3Galβ1-3(Fucα1-4)GlcNAc- Colorectal, pancreas [74,86,89,94,95
Glycan coreRelated cancer and references
 Tn antigen (CD175) GalNAcαSer/Thr Breast, colorectal, pancreas [10,33,63,64,67–75
 Sialyl-Tn antigen (CD175s) Siaα2-6GalNAcαSer/Thr Breast, colorectal, pancreas [10,33,58,64,67,74,76–79
 Core 1 or T antigen Galβ1-3GalNAcαSer/Thr Breast, colorectal [10,23,33,67,80–83
 Core 2 GlcNAcβ1-6(Galβ1-3)GalNAcαSer/Thr  
 Core 3 GlcNAcβ1-3GalNAcαSer/Thr Colorectal [23
 Core 4 GlcNAcβ1-6(GlcNAcβ1-3)GalNAcαSer/Thr Colorectal [23
Glycan epitope 
 Blood group H Fucα1-2Gal-  
 Blood group A GalNAcα1-3(Fucα1-2)Gal-  
 Blood group B Galα1-3(Fucα1-2)Gal-  
 Linear blood group B Galα1-3Gal-  
 Blood group i Galβ1-4GlcNAcβ1-3Gal-  
 Blood group I Galβ1-4GlcNAcβ1-6(Galβ1-4GlcNAcβ1-3)Gal-  
 Blood group Sd(a), Cad GalNAcβ1-4(Siaα2-3)Gal- Mouse specific glycan 
 Lewis a Galβ1-3(Fucα1-4)GlcNAc- Colorectal, pancreas [26,84
 Lewis x Galβ1-4(Fucα1-3)GlcNAc- Colorectal [84
 Sialyl-Lewis x Siaα2-3Galβ1-4(Fucα1-3)GlcNAc- Breast, colorectal [37,85–91
 Lewis y Fucα1-2Galβ1-4(Fucα1-3)GlcNAc- Colorectal [92,93
 Sialyl-Lewis a Siaα2-3Galβ1-3(Fucα1-4)GlcNAc- Colorectal, pancreas [74,86,89,94,95

The Tn and STn antigens have been identified in a broad spectrum of adenocarcinomas including those of the colorectum, breast, lung, ovary, and pancreas [10,96]. In colorectal adenocarcinoma, the incidence of Tn expression, assessed historically using GalNAc-binding lectins such as Vicia villosa agglutinin (VVA) and Helix pomatia agglutinin (HPA), has ranged from 47 to 90% in colorectal adenocarcinoma specimens; the expression of the STn antigen parallels that of the Tn antigen in colorectal adenocarcinoma specimens [33,67,97].

The recent development of the recombinant antibodies ReBaGs6 and Remab6, which have greater sensitivity and specificity for the Tn antigen, has permitted the identification of Tn expression in 95% of colorectal adenocarcinoma specimens versus seldom in matched normal colorectal tissue from the same patients [33,98]. Interestingly, preliminary analysis of transitional margin tissue, defined as histologically normal colorectal mucosal epithelium immediately adjacent to malignant cells, demonstrates a pattern of increased Tn expression, though the details of this finding remain to be elucidated [33].

Mucins in CRC

Mucins are a family of ∼20 high molecular mass, heavily O-glycosylated glycoproteins, rich in Ser/Thr/Pro residues, which are characterized by their ability to form gels and which are either membrane-bound or secreted by the epithelial tissues in many animals [10]. Mucin-type glycoproteins are the major secretory products of the human colon [15,21,41,67]. O-glycosylation accounts for over half of mucin structures by weight [99,100] and plays a fundamental role in mucin biologic function, as abnormalities in mucin O-glycosylation appear to cause reduced expression of mucins in vivo and increased susceptibility to bacterial degradation in vitro [101–103]. O-glycans extend from the mucin protein core and interact closely with the external environment or—in the case of intestinal mucus—with the gut microbiome. Abnormalities in mucin-type O-glycans have thus been identified as central to the development of various epithelial disease processes, particularly those in which inflammation or microorganismal interactions play a role [104]. It is therefore not surprising that changes in mucin O-glycosylation appear to be a frequent occurrence in various human malignancies, including CRC [105]. The physiologic roles of mucin include the maintenance of environmental barriers, the retention of growth factors and signaling mediators, and participation in cellular signaling; some or all of these functions may be compromised by changes in mucin O-glycosylation [10].

Colonic mucus contains two layers; the inner glycocalyx layer is only 50–100 μm thick and is fixed to the colonic epithelial cells, whereas the outer layer is 800 μm thick and is loosely attached to the inner layer [104,106,107]. Colorectal secreted mucus is composed mainly of Mucin-2 (MUC2), a polymeric mucin of which up to 80% by molecular mass consists of O-glycans [104]. The glycocalyx on the surface of intestinal epithelial cells consists of transmembrane mucins including Mucin-1 (MUC1), Mucin-3 (MUC3), Mucin-4 (MUC4), Mucin-12 (MUC12), Mucin-13 (MUC13) and Mucin-17 (MUC17), with MUC4, MUC12, MUC13, and MUC17 representing the primary constituents of the glycocalyx in the colorectum under normal physiologic circumstances [49,108,109]. Under normal physiologic circumstances, this subdivision of mucus layers plays a significant role in mediating epithelial interactions with gut microbiota; while bacteria are absent from the inner layer, the outer layer is heavily colonized by intestinal flora [106].

Alterations in mucin expression patterns have been observed in colorectal inflammatory and malignant disease processes and these changes may be contributory to disease phenotype [110]. Murine studies have demonstrated that MUC2 plays a role in retarding the development of CRC; mice with an engineered deficiency in MUC2 have completely absent colonic mucus and display dense bacterial adhesion to colonic epithelia, ultimately resulting in the development of severe spontaneous colitis and CRC [106,111,112]. This is reflective of the decrease in MUC2 described in CRC, with the notable exception of mucinous carcinoma, a histologically distinct category of CRC [113]. Not all mucins play a protective role; MUC1 and MUC4, for example, directly disrupt epithelial tight junctions via the HER2 pathway, and MUC1 disrupts adherens junctions through β-catenin binding. Because MUC1 and MUC4 play a role in the loss of epithelial cell polarity, they are probable culprits in the epithelial-mesenchymal transition (EMT) that is a defining feature of CRC progression. The increase in intestinal permeability resulting from the loss of cell–cell adhesions is the likely cause of subsequent cell surface mucin overexpression; this may explain the role of chronic inflammation—as with inflammatory bowel disease—in the progression to CRC [110].

Differences in humans versus mice in colorectal biology and glycomics

There are many commonalities between human CRC and CRC in a murine model, whether colitis-associated or secondary to genetic manipulation. As with many other human malignancies, CRC demonstrates increased incidence in the setting of chronic mucosal inflammation, particularly in cases of inflammatory bowel disease (IBD) such as ulcerative colitis (UC) and Crohn's disease (CD), most commonly [114]. There are several ways in which these conditions closely parallel chemically inducible tumorigenesis in mice, which requires the intraperitoneal administration of a single carcinogenic substance—such as dimethylhydrazine (DMH) and its metabolites azoxymethane (AOM) and methylazoxymethanol (MAM) acetate—followed by an orally-delivered inflammatory insult using dextran sodium sulfate [115,116].

Histopathologically, the spectrum of induced murine tumors varies from tubular adenomas to polypoid and sessile adenocarcinomas, including mucinous variants; this is reflective of range of lesions observed in humans, though there is evidence that the adenoma-carcinoma sequence characteristic of most human CRC is not typically observed in mice [115,117]. Colitis-associated murine carcinomas demonstrate positive immunohistochemical staining for β-catenin, COX-2, and inducible nitric oxide synthase, and—like human CRC—diminished expression of APC and p53 [118,119]. In terms of metastatic potential, over one-third of patients demonstrate lymphatic spread or metastasis at the time of initial diagnosis, whereas in murine colitis-associated CRC this is seldom the case [117].

Altered protein glycosylation in human CRC has been implicated in oncogenic transformation as well as the development of more virulent characteristics, including impairment of intercellular structures and increased lymphohematogenous metastasis [48]. CRC is particularly known to feature compromised O-glycan elongation, resulting in the overexpression of the immature, abnormally truncated O-glycans Tn, STn, T and sialyl-T antigens [64]. Additionally, O-glycans in CRC often display excessive sialylation or fucosylation, resulting in terminal antigens such as sialyl-Lewis a (SLea) and sialyl-Lewis x (SLex) [120]. The expression of these altered terminal antigens is particularly pronounced in CRC due to the prominence of the colonic mucin layer, which consists of heavily O-glycosylated mucin glycoproteins, the most abundant being MUC2 [106].

The development of CRC in the setting of IBD in humans is necessarily preceded by the disruption of the normal intestinal mucus barrier [49,108]. Similarly, murine models of induced colitis have reported a defect in mucin biosynthesis prior to disease development [121]. Spontaneously arising CRC in Muc2−/− mice is shown to be due to defects in the inflammatory barrier, and Muc2/ mice are more susceptible toward chemically-induced colitis that is known to progress to colitis-associated cancer [122]. Similarly, Muc13−/− mice demonstrate severe colitis with chemical induction, and a resultantly increased risk of progression to CRC [110]. Mouse knockout studies have also demonstrated that not all mucin types confer resistance to inflammation; both Muc1−/−and Muc4−/− mice are highly resistant to chemically induced colitis and CRC relative to wild-type mice, and Muc4−/− mice show increased expression of Mucin-2 and Mucin-3 [109].

Severe colitis progressing to cancer is also observed in mice genetically engineered to lack C1GalT1 (Cosmc) in their intestinal epithelial cells (IEC C1GalT1−/− mice) as well as mice engineered to lack both Cosmc and core 3 β1,3-N-acetylglucosaminyltransferase (C3GnT); mice resultantly deficient in core 1 or both core 1 and core 3 O-glycans express Tn antigen in IEC and secreted MUC2, and they display a drastically thinned mucus layer [102,123]. Similarly, the presence of aberrant mucin-type carbohydrate antigen structures in human cancer cells is well-described and has been linked with increased aggression and invasiveness of CRC [67,124].

O-glycans in breast cancer

According to the American Cancer Society [45], breast cancer is the most frequently diagnosed cancer and the leading cause of cancer-related death in women worldwide. In the United States, it is the most commonly diagnosed cancer with an estimated >260 000 new cases (composing 30% of new cancer cases) and the second most common cause of cancer death in women. In addition, the incidence of breast cancer has increased dramatically over the past few decades. It is reported that in the U.S. 1 in 8 women are found to have breast cancer and 1 in 38 will die from it. Moreover, the peak incidence is generally in middle-age group (45–59 years), which has become more prominent over the last few decades [125]. The increase in incidence is largely due to improved diagnostic tools and screening methods; however, there remains a need for better early diagnostics and novel therapeutics in treating the disease.

Overall, breast cancer mortality rates have been decreasing since the 1970s with improved screening and therapeutics. Looking at the 5-year relative survival rates for breast cancer in the U.S. based on the Surveillance, Epidemiology, and End Results (SEER) Stage database from the National Cancer Institute, the survival rates are the best for localized disease, and for distant disease, it is very poor (27%). Data supports that metastatic breast cancer median survival is ∼2 years [126]. Breast cancer still remains a major cause of death among women because current methods for routine screening have significant limitations. Some of these limitations include mammography detection ability as well as overuse of excisional biopsies. Mammogram is the screening standard, but it can have a false negative rate of up to 20%. This occurs more often in younger women due to denser breast tissue, which can mask underlying disease. Also, about half the women getting annual mammograms over a 10 year period will have a false-positive finding. False positive detection on mammography leads to unnecessary biopsies and surgeries performed [127]. There is a significant lack of cancer specific biomarkers for cancer tissue and a lack of detectable biomarkers in the serum available for breast cancer screening and/or targets for therapeutic treatment. The combination of current available screening methods and more sensitive and specific biomarkers will make detection of breast cancer more robust and will avoid unnecessary procedures, resulting in earlier treatment intervention.

O-glycan changes in breast cancer

Altered O-glycosylation has been observed in over 90% of breast cancers with correlation to progression, worse prognosis, and metastatic potential [128–130]. In breast cancer, there can be changes in the number of O-GalNAc glycans added to glycoproteins. Other observed changes in O-GalNAc glycosylation are changes to core structures and this aberrant process results in the expression of TACAs such as the Tn antigen [131]. Breast cancer cells have also been shown to express shorter O-glycans due to either aberrant glycosyltransferase activity, premature sialylation of the polylactosamine chain blocking addition of further glycans, or truncation of the O-glycans at the core 1 level, all of which can result in expression of TACAs, including T antigen (core 1), Tn antigen, ST antigen, and STn antigen structures [132].

Glycosyltransferases and their effects in breast cancer

Multiple mechanisms have been shown to contribute to the change in the O-glycosylation process in regards to breast cancer, such as the changes in expression and localization of ppGalNAc-Ts and altered glycosidase activity [133]. GalNAc-T1 and GalNAc-T2 are expressed in normal mammary epithelial cells and are thought to be the ‘house-keeping’ GalNAc-Ts; however, GalNAc-T6, GalNAc-T4, GalNAc-T14, and GalNAc-T9 have been demonstrated to play a role in breast cancer disease development, progression, and metastasis.

Increased expression of GalNAc-T6 was the first identified ppGalNAc-T involved in the majority of breast cancer, up to 81% [134–136], with no expression in normal breast tissue. GalNAc-T6 mRNA has been demonstrated to be a potential specific marker in the molecular diagnosis of breast cancer cells dissemination [135]. Another group also demonstrated that overexpression of GalNAc-T6 may contribute to mammary carcinogenesis through aberrant glycosylation of MUC1, which results in increased proliferation and decreased cell adhesion [137].

Up to 70% of breast cancers are considered estrogen receptor positive. It has previously been shown that GalNAc-T4 is potentially involved in the estrogen network as a trafficking gene. Further studies demonstrated that GalNAc-T4 expression is associated with the estrogen status of cells through modulation of glycosylation of FOXA1, a transcription factor that serves as a cofactor to ERα that promotes estrogen-responsive gene expression [138]. It has also been reported that microRNA-365 targets GalNAc-T4 mRNA and overexpression of microRNA-365 leads to inhibition of breast cancer cell growth [139].

GalNAc-T14 has been reported to be a potential breast cancer biomarker, as its expression is demonstrated in 80% of breast cancers by immunohistochemistry and only found in 14.6% of non-malignant breast tissue [140]; however, the mechanism and function have yet to be determined. Recent studies have suggested that GalNAc-T14-dependent O-glycosylation of EGF-containing fibulin-like extracellular matrix protein 2 (EFEMP2) increases the ability of breast cancer cell invasion both in vivo and in vitro, and knockdown expression of GalNAc-T14 suppresses this behavior, demonstrating a potential area for further investigation of underlying mechanisms of breast cancer invasion [141].

There has been limited advancement in identifying biomarkers for breast cancer metastasis. GalNAc-T9 is expressed most abundantly in the brain and shows low expression levels in the other tissue such as normal breast tissue [142]. Increased methylation of GalNAc-T9 was found to be associated with increased breast cancer metastasis to the brain [143].

O-glycans expressed by normal breast epithelial cells are composed of extended core 2 structures forming a linear polylactosamine chain, which then can be fucosylated or sialylated [144]; however, breast cancer cells have been shown to express truncated O-glycans, switching from a core 2 structure to core 1 structure. The presence of T or Tn antigen, which represents incomplete synthesis of the glycans to peptide has been demonstrated to be a result of altered glycosyltransferase activities. It has also been reported that breast cancer tissues contain more sialic acid and more sialyltransferase activity compared with normal tissue. Breast cancer cells may thus express shorter O-glycans resulting in expression of sialyl-T antigen and STn antigen due to addition of sialic acid to terminal core 1 structures [132].

Currently there is still a lack of understanding of the exact mechanism by which glycosyltransferases alter the structures of glycans associated with development of breast tumor pathology. Further studies are needed to understand these glycosyltransferases and their involved pathways. Gain or loss of glycosyltransferase expression [145] as a result of the loss of chromosomal integrity may also be present in tumor cells, but the consequences of such changes require further study.

Tumor-associated carbohydrate antigens in breast cancer

The expression of the T antigen in breast cancer was first reported in 1979, where expression was noted in breast cancer cells but not in normal breast epithelium or benign lesions [80]. The expression of T antigen is noted to be present in greater than 90% of breast cancer tissues. Over the years, detection of T antigen in breast cancer has not been thoroughly investigated, due to the lack of specific anti-T detectors. In 2013, a study demonstrated that 98% of the disseminated tumor cells found in bone barrow were positively stained with an anti-T antibody, leading to the conclusion that T antigen plays a role in the metastatic process [81]. The core 2 branch structure seen in O-glycans on the normal mammary epithelium is initiated through the action of the glycosyltransferase core 2 β1,6-N-acetylglucosaminyltransferase (C2GnT1) (Figure 1). The expression of T antigen in breast cancer is thought to be the result of decrease in C2GnT1 activity, which causes a shift from core 2 structures to core 1 [82]. It has also been reported that β-galactoside α2,3-sialyltransferase (ST3Gal1) expression also decreases as seen in altered sialylation of MUC1. Changes in the structure of O-glycans resulted in T antigen, and is found to be partially associated with MUC1 overexpression, which as a result down-regulated the expression of C2GnT1 and ST3Gal1 [146]. Galectin-3 interactions with T antigen have been evaluated in the metastatic process of breast cancer [83]. Over the past few decades, there has been evidence suggesting the presence of the T antigen and its role in breast cancer development and spread, but a more detailed understanding of the mechanisms of these interactions are needed.

The Tn antigen has been shown to be expressed in 90% of breast cancers and is generally not expressed in normal tissue [68] (Table 1). The loss of heterozygosity of the T-synthase chaperone Cosmc (C1GalT1C1) has been described in colon cancer in Tn-positive cells but has not been consistently reported in epithelial cancers such as breast cancer. Lectins such as HPA and VVA, which bind the Tn antigen, but are not highly specific to only this glycan structure, have been used widely for detection of Tn antigen. Part of the challenge of detecting carbohydrate antigens is specificity, as these lectins bind to terminal GalNAc in Tn, as well as blood group A or glycolipids. HPA and VVA have been used in studying Tn expression in breast cancer [69,70], and the presence of Tn antigen has been associated with decreased survival, increased risk of recurrence, and lymph node metastasis [71–73].

STn is formed by the α2–6 sialylation of the Tn antigen by ST6GalNAc1 [76] (Figure 1). STn is a pan-carcinoma antigen that usually is expressed in early tumor development, and like the Tn antigen, it is generally not expressed in normal tissue. STn was discovered in metastatic breast cancer cells during the generation of monoclonal antibody B72.3 [77]. STn has been reported to be expressed in 60–80% of breast cancers [78]. The expression of STn is associated with tumor progression, migration, and aggressiveness, and it has also been associated with resistance to chemotherapy in those with clinical node-positive disease [79]. As Tn antigen can be converted into STn through ST6GalNAc1 [58], ST6GalNAc1 might compete with the T-synthase for the GalNAc-peptide substrate. An increase in expression of α3-sialyltransferase ST3Gal1 has also been shown to promote breast cancer [58,147].

The overall effects of glycosyltransferases leading to aberrant glycosylation products have translated to downstream altered signaling pathways that activate cytokines and growth factors leading to changes in cellular growth, differentiation, and cell death. The exact mechanisms overall are still poorly understood, but the evidence supports that altered glycosylation is a key factor in breast cancer development and progression.

Mucins in breast cancer

MUC1 is associated with breast cancer and the antigens CA15-3 and CA27.29, which have been used as biomarkers to predict breast cancer recurrence [136]. GalNAc-T6 is involved in the addition of O-glycans to MUC1 that play a role in the proliferation of breast cancer cells by altering cell–cell adhesion, promotion of malignant transformation and metastasis, resulting in cancer cells which evade the immune response due to a different antigenic appearance. The lack of cell–cell interaction allows the cancer cells to travel to other locations and result in metastatic growth [148]. MUC1 appears to be a natural ligand for galectin-3, which has been shown to promote breast cancer metastasis by protecting against apoptosis through mediating adhesion to endothelial cells [83]. It has also been observed that galectin-3 expression is associated with chemosensitivity and chemoresistance in breast cancer. Some of the proposed mechanisms includes the response to DNA damage and repair or the inhibition of apoptosis after chemotherapy. These data suggest that the expression of galectin-3 may impact treatment response, but the exact mechanism is currently unknown [149].

MUC1 is a heavily researched and targeted mucin in breast cancer immunotherapy development. In mice, it was demonstrated that most of the immunogenicity of MUC1 lies within a 20 amino-acid peptide repeat (VNTR), which when coupled with oxidized mannan generates a fusion protein of mannan-MUC1, leading to H2 restricted cytotoxic T cells that protect mice against MUC1+ mouse tumorigenesis [150]. When this was carried into human models, however, it was met with challenges, due to the advanced disease pathology and immunocompromised conditions of breast cancer patients. In 2006, a Pilot phase III immunotherapy study using oxidized mannan-MUC1 in early-stage breast cancer patients was conducted [151]. During the 12–15 year follow up period, the group demonstrated a clinically significant decrease in recurrence rate and benefit in overall survival of early stage breast cancer patients. A larger Phase III trial is perhaps needed for more definitive conclusions [152].

Mouse models in breast cancer

Studies related to glycosylation processes and TACAs have been explored in murine models in breast cancer. Mouse models have demonstrated that deficiency in core 1-derived O-glycosylation leads to impaired localization of MUC1 on the epithelium of mammary tissue and loss of core 1-derived O-glycans decreased breast cancer development [153].

A study published in 2013 using breast cancer cell lines MCF-7 and MX-1 explored the effects of antibacterial peptides (ABPs), that have previously demonstrated some cancer-selective toxicity, in breast cancer cell growth. O-glycosylated glycoproteins were noted to have the strongest effect on binding and cytotoxicity among the ABPs tested. It was also demonstrated that sialic acid is a component of the binding sites for cationic ABP interactions with glycoproteins and gangliosides. Mouse xenograft studies demonstrated inhibition of growth by induction of apoptosis and decreased vascularization of tumor cells that were treated with ABPs [31].

The functional role of Tn antigen in breast cancer biology in lymph node metastasis was explored by demonstrating that a newly generated anti-Tn antibody blocked Tn-positive MCF-7 breast cancer cell line interaction with lymphatic endothelium of the mammary pad in mice [154]. STn has also been evaluated in rodent models of breast cancer and is found to be associated with histological and clinical disease progression. Murine models have been used to investigate the expression of STn on breast cancer on development of osteolytic lesions. Interestingly, the presence of STn impaired the adhesive capacity of β1 integrin, which is believed to be the main carrier of the STn epitope, and this process inhibited tumor cell engraftment leading to less capacity for skeletal colonization [155].

O-glycans in pancreatic ductal adenocarcinoma (PDAC)

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease, with a 5-year overall survival of 9% [156]. Surgical resection provides the only possibility for cure. However, patients often present at advanced stages when surgical resection is not possible, both due to the propensity for PDAC to metastasize early, and the absence of symptoms at early stages. There is an urgent need to identify reliable biomarkers to enable early detection and diagnosis and develop new therapeutic strategies. Glycosylation changes in PDAC present a promising opportunity to fill this need.

Truncated O-glycans in pancreatic cancer

Virtually all epithelial cancer cells are characterized by expression of the immature, truncated O-glycans, Tn and STn [74]. Tn antigen is expressed in 75–90% of PDACs and up to 67% of precursor lesions [75]. The expression of these truncated O-glycans in cancers has been proposed to be from various mechanisms: altered expression of glycosyltransferases, somatic mutations or hypermethylation of Cosmc (C1GalT1C1), and/or relocation of ppGalNAc-Ts from the Golgi to the endoplasmic reticulum [56,63,96,137,157–163]. In pancreatic cancer specifically, Radhakrishnan et al. performed exosome sequencing of 201 genes involved in glycosylation in 46 PDAC tumor and paired normal tissues and found surprisingly few somatic mutations, and notably no mutations in Cosmc [64]; however, they observed hypermethylation of the promoter of the Cosmc gene in 38% of the patient samples. Hypermethylation of the Cosmc promoter correlated with expression of Tn antigen and loss of C1GalT1 expression, suggesting that inactivation of Cosmc is a common mechanism in pancreatic cancer.

Expression of the truncated O-glycans Tn and STn is strongly correlated with pancreatic cancer cell growth and metastasis [64,75]. Knockout of Cosmc in the T3M4 pancreatic cancer cell line as well as an organotypic epidermis tissue model induced traditional oncogenic features: hyperproliferation, loss of tissue architecture, disruption of basement membrane adhesion, and invasive growth [64]. Hofmann et al. showed complementary results by inducing Tn expression with lentiviral-mediated knockdown of Cosmc in two pancreatic cell lines, Pans-1 and L3.6pl [75]. After confirming Tn expression, they showed increased migration and decreased apoptosis, suggesting a role for Tn antigen expression in metastatic behavior of PDAC cells [75]. Implantation of Cosmc-deficient HaCaT cells into nude mice was highly tumorigenic, providing support that the expression of truncated O-glycans directly induces oncogenic features, such as cell growth, invasion, and loss of cell–cell adhesion [64].

Tn antigen expression on specific proteins in PDACs has been investigated recently. Truncated O-glycans, identified using VVA, have been detected on nucleolin, EGFR, and Her2 [75,164]. Hofmann et al. identified nucleolin, GRP-78, alpha-enolase, and annexinA2 using VVA lectin-based immunoprecipitation and mass spectrometry in PANC-1 Cosmc knockdown cells. These four proteins are promising, as they are differentially expressed in PDAC [165–168], are localized to the cell membrane [169–172], and are known to promote cancer cell signaling [75]. Interestingly, strong colocalization of Tn antigen (by VVA staining) and nucleolin on immunohistochemistry of patient samples was associated with poor survival [75]. In a study mapping the O-GalNAc glycoproteome using multiple pancreatic cancer cell lines, 50% of the identified glycoproteins were expressed uniquely in one cell line, and each cell line contributed its own repertoire of glycoproteins. This suggests distinct glycoproteomes for different cancers and should be investigated further [15].

Sialyl Lewis antigens in PDAC

The human serological assay for CA19-9 is used clinically to manage pancreatic adenocarcinoma. Though not used as a screening biomarker, it is used to detect response to systemic therapy, and a decrease in CA19-9 in response to treatment is a favorable prognostic factor. CA19-9 is a cancer-associated carbohydrate antigen, sialyl-Lewis a (SLea), which represents a member of the Lewis family of blood group antigens [26,94,173–175] SLea is expressed at low levels in normal tissue, higher levels in embryonic tissue, and is highly overexpressed in epithelial-derived cancers [176,177]. In normal pancreas, SLea is expressed on the apical surfaces of ducts, whereas in PDAC, it is heavily secreted into the lumen of proliferating ducts and can also pass into the bloodstream [178].

The clinical utility of the CA19-9 assay in PDAC is unfortunately limited. CA19-9 can be elevated in patients with biliary obstruction of any cause (not necessarily malignant) and is expressed by other gastrointestinal cancers, limiting its specificity. In addition, 10–15% of the population is Lewis-negative, meaning that these individuals lack the functional fucosyltransferase 3 (FUT3) enzyme necessary to synthesize SLea and will not manifest an elevated serum CA19-9 even in the presence of late-stage PDAC [94,177,179]. The serological assay for CA19-9 appears to detect the SLea antigen regardless of its lipid or protein carrier. SLea has been found on numerous glycoproteins, including many mucin glycoproteins and apolipoproteins [74,94]. Identification of CA19-9 on specific proteins and lipids has the potential to increase the performance of the CA19-9 assay [74].

SLex, an isomer of SLea, is also up-regulated in some pancreatic cancers, and can be detected in the blood of PDAC patients [85,86,180]. SLex has been found on migrating lymphocytes in pancreatic cancer patients, and is linked to increased invasion and metastasis [87]. Interestingly, the sialyl Lewis antigens are the minimum recognition motif for selectins. Selectins are lectins expressed on the endothelial surface that facilitate leukocyte trafficking. Through a similar pathway, they may also play a role in tumor extravasation and cancer metastasis [88]. Numerous proteins implicated in PDAC (Kras, SPARC, Wnt7b, ceruloplasmin) express SLex antigens [85,89].

Identification of the glycoprotein and glycolipid carriers of SLea and SLex is imperative for biomarker discovery. In addition, elucidation of the pathogenesis of Lewis blood group antigens in facilitating PDAC metastasis has incredible therapeutic potential, as early metastasis is one of the main drivers behind the poor survival in PDAC.

Mucins in PDAC

Normal epithelial cells derived from the pancreas express a subset of over 20 mucin core proteins that are heavily O-glycosylated in a manner specific to the requirements of the pancreas. The process of malignant transformation results in expression of different mucin core proteins and distinct patterns of O-glycosylation, particularly of the tandem repeat domain. In cancer, the tandem repeat domain expresses the truncated O-glycans, Tn and STn, which apart from being tumor antigens themselves, as discussed above, also expose protein regions of the tandem repeat domain that would otherwise be blocked to recognition by antibodies.

MUC1 is expressed on the apical surfaces of simple and glandular epithelia, including pancreatic ducts, as well as on circulating cells such as activated T cells and activated dendritic cells [181–183]. In normal epithelial cells, the expression of MUC1 is limited to the apical membrane and covered with highly branched complex glycans [128]; however, in many pancreatic adenocarcinomas, the polarized expression of MUC1 is lost, and it is highly overexpressed and aberrantly O-glycosylated [105]. This exposes highly immunogenic truncated O-glycan structures. MUC1 has been shown to suppress T cell responses that are considered essential for antitumor immunity. Cancer-associated MUC1 inhibits antibody-dependent cell-mediated cytotoxicity and increases resistance to NK cell cytotoxicity [184,185]. MUC1 has been shown to interfere with cell–cell and cell–matrix interactions [186]. Though not as well studied in pancreatic cancer patients, the presence of circulating antibodies reactive with underglycosylated MUC1 in breast cancer patients was associated with a better prognosis [187–189]. Thus, MUC1 is considered a prime target for immunotherapy (see section on therapeutics).

Remmers et al. investigated expression patterns of several mucin core proteins and associated O-linked glycans in PDAC primary tumors, liver metastases, and normal pancreas using immunohistochemistry [190]. Ductal epithelial cells from normal pancreas primarily express MUC1, MUC6, CA19-9 (SLea), and what we have termed SLec, the precursor to SLea (Figure 1), consistent with prior reports [191–196]. There were high levels of T antigen on MUC1 in normal pancreas; in comparison, T antigen on MUC1 was rarely seen in PDAC and instead high levels of STn on MUC1 was observed. MUC5AC and MUC16 were observed in a significant percentage of PDAC tumors, and not observed in normal pancreas. Paired liver metastases expressed many of the same mucins and glycans as their corresponding primary tumors, including MUC4, MUC5AC, and STn [190]. However, there were consistent alterations in expression of certain mucins. MUC2 and MUC5B were absent from primary tumor, but expressed in the liver met in almost all cases. MUC4, MUC5AC, MUC16, STn, SLec, T on MUC1, and Tn on MUC4 were more highly expressed in liver metastases compared with primary tumors; in contrast, MUC6, MUC17, and MUC7 were more highly expressed by primary tumors [190].

MUC6 is the secreted mucin expressed in normal pancreas [191]. Pancreatic cancers exhibit de novo expression of one or more of the secreted mucins MUC2, MUC5AC, MUC5B, and MUC7 [190]. Aberrant glycosylation of secreted mucins may directly affect immune responses and may alter the types of small molecules (growth factors, cytokines, etc.) bound to the mucous layer. Indeed, altered glycans have been shown to be present on a number of mucins found in the circulation of patients with pancreatic cancer [197,198].

Mouse studies in PDAC

Disruption of C1GALT1 (T-Synthase) leads to expression of truncated O-glycan structures shown to be prevalent and important in the pathogenesis of pancreatic cancer [199]. Chugh et al. [199] crossed C1galt1 floxed mice (C1galt1loxP/loxP) with KrasG12D/+; Trp53R172H/+; Pdx1-Cre mice (KPC mice) to create KPCC mice, an O-glycosylation deficient PDAC mouse model. The KPCC mice experienced much faster PDAC progression with low grade pancreatic intraepithelial neoplasia (PanIN) observed as early as 3 weeks. 33% of KPCC mice had high grade PanIN3 lesions at 5 weeks, which increased to 60% by 10 weeks. This is extremely fast compared with KPC mice, which start to develop PanIN lesions ∼10 weeks. Invasive PDAC tumors were apparent in 40% of KPCC mice at 5 weeks, 60% at 15 weeks, and 90% at 20 weeks. KPCC mice also had a dramatically shortened median survival of 14.6 weeks compared with 28.6 weeks in the KPC mice. Histopathologically, KPCC tumors revealed poorly differentiated or undifferentiated morphology compared with moderately-to-well differentiated tumors in KPC animals. KPCC tumors also had significant increase in ki-67 staining and increased number of mitotic figures and atypical mitotic figures. As expected, KPCC tumors had increased expression of Tn antigen as detected by lectin VVA, confirming the functional knockout of C1GALT1. Interestingly, conditional inactivation of C1GALT1 alone was not sufficient to induce PanIN and PDAC; however, together with mutations in Kras and p53, it significantly accelerates disease progression and shortens survival. In addition, early metastatic lesions (10 weeks) were observed in KPCC mice compared with the typical late metastasis of KPC mice. No distant metastatic lesions were observed in KPC mice until 20 weeks; however, KPCC mice showed gross metastatic lesions involving several organs.

This mouse model is an excellent tool to study the effects of truncated O-glycosylation on cancer progression and metastasis. Although Radhakrishnan et al. reported that somatic mutations in Cosmc (C1GALT1C1) were not observed in PDAC, and more commonly observed hypermethylation of Cosmc [64], the functional result of this mouse model is an important tool in understanding PDAC progression. A mouse resulting from crossing a mouse with inactivated COSMC confined to the pancreas with the KPC mouse would also be an interesting and useful addition to the field.

CA19-9 in engineered mice

CA19-9 (SLea) is currently the only clinically used biomarker for pancreatic cancer. In order to investigate the direct role of SLea in cancer progression and to facilitate the discovery of PDAC biomarker candidates, Engle et al. [95] created a mouse model that reflected the SLea elevation observed in human patients. FUT3 is the only described enzyme with the ability to add fucose through an α1,4 linkage to generate SLea. Mice lack this enzyme. However, transduced expression of FUT3 alone led to generation of related Lewis x isotopes, but not SLea. To address this, they co-expressed both FUT3 and β1,3-galactosyltransferase 5 (B3GALT5) in mouse cells. B3GALT5 is the enzyme required for the production of Type I chain precursors, which serve as the precursors for the SLea modification. Expression of both FUT3 and B3GALT5 led to cell surface expression of CA19-9 levels equivalent to that seen in human PDAC cell lines, and they shared, on average, 72.3% of the SLea protein carriers with human PDAC cell lines.

Engle et al. then created a mouse model with inducible SLea expression. Using PDX1-CreLox system activated by oral doxycycline (Dox), the expression of FUT3, B3GALT5, and eGFP was limited to the pancreas, duodenum, and bile duct (C;RLSL;F). C;RLSL;F mice exhibited acute pancreatitis that progressed to chronic pancreatitis by 28 days. This was confirmed histologically, biochemically (by elevations of serum amylase and lipase), and clinically (weight loss, pancreatic exocrine insufficiency). SLea was predominantly expressed in pancreatic ducts and islet cells, and rarely observed in acinar compartments. The mice also exhibited an elevated CA19-9 serum level. Interestingly, secreted SLea was also observed coating eGFP-negative endothelial cells and fibroblasts. E-selectin is an endogenous receptor of SLea expressed by endothelial cells, which may explain this interaction.

To determine whether CA19-9 expression promotes PDAC, they crossed the C;RLSL;F alleles with the conditional KrasLSL/G12D allele (K;C;RLSL;F). CA19-9 expression significantly accelerated pancreatic cancer lethality compared with untreated and control littermates. When treated with Dox, K;C;RLSL;F mice rapidly succumbed to primary and metastatic pancreatic cancer with a median survival of 202 days compared with 460 days in the control cohort and 420 days in the untreated K;C;RLSL;F cohort. After 2 weeks of Dox, CA19-9 expressing mice exhibited a high penetrance of cystic and fibroinflammatory disease with many PanIN-1B and occasional PanIN 2 precursor lesions. After 4 weeks of Dox, cystic papillary neoplasia and invasive cancer could be detected. Widespread metastases were observed in the peritoneum, diaphragm, liver, and lung in at necropsy of Dox-treated mice.

The development of a mouse model that allows the Kras mouse to express CA19-9, the only current clinically used biomarker, is a great resource to not only identify more specific carriers of CA19-9 as biomarkers, but also to investigate the direct role of SLea in the initiation, progression, and metastasis of pancreatic cancer.

Therapeutic avenues and opportunities

Whether it is colon, breast, pancreatic, or another type of adenocarcinoma, each represents a heterogenous, complex disease processes, which makes having specific, targeted therapy difficult. Many studies and trials have been in progress that target specific glycoprotein antigens in these types of cancer. The roles of TACAs have been an area of investigation into antibody development against these carbohydrate antigens. The discovery of altered O-glycan structures has led to development of many detecting reagents including glycan- or glycoprotein-targeted antibodies. There continues to be advancement of glycan-targeted diagnostics and therapeutics in various cancer types through passive immunotherapies and carbohydrate-based vaccines.

O-glycosylation changes in CRC represent an evolving source of potential targeted therapeutics. At present, there are several serological glycoprotein biomarkers utilized for prognostication and recurrence monitoring in CRC, including CEA and, to a lesser extent, CA19-9 and SLex; the applications of these known biomarkers is limited in CRC due to their relatively low sensitivity and specificity, precluding their use as screening tools or in diagnostics [48].

Additionally, cell line studies using the disaccharide decoy GlcNAcβ1,3Galβ-O-napthalenemethanol, which is the disaccharide precursor of SLex, have demonstrated that the generated SLex-deficient colorectal cancer cells show diminished interactions with selectins, thus raising the possibility of using such decoys as anti-metastatic drugs in the future [200].

In breast cancer, one aspect of therapy can be through alteration of GT expression that is involved in TACA biosynthesis. Several examples have shown that GT genes, including ST6GALI, are regulated by oncogenes. Only a limited number of promoters of GT genes have been characterized, and is in need of further data to understand the signaling pathways and membrane receptors that are involved in cancer regulation. This type of data could lead to novel mechanisms to inhibit TACA expression in breast cancer [132].

T antigen-specific therapeutic responses in humans have long been studied, and successfully immunized breast cancer patients with a T antigen-positive vaccine containing asialoglycophorin, resulting in improved survival [68]. JAA-F11, a monoclonal antibody developed to be highly specific to T antigen, has been ‘humanized’ and used as immunotherapy and drug conjugation therapy in breast cancer and resulted in better survival rate of patients [201].

Theratope, a synthetic STn epitope conjugated to a high molecular mass protein carrier, KLH (STn-KLH), was generated to target STn antigen in breast cancer. A multicenter, double blinded, randomized phase III trial of the therapeutic cancer vaccine STn-KLH in women with metastatic breast cancer who had non-progressive disease or no evidence of disease after initial chemotherapy was deemed safe and well tolerated but did not affect time to progression or overall survival duration [202].

Several clinical trials have targeted the Ley antigen and ganglioside GD2 with anti-TACA antibodies via production of a carbohydrate mimicking peptide (CMP) that mimics the receptors of Ley antigen and GD2. The initial phase I trial demonstrated positive patient tolerance and induced functional antibodies using CMP (P10s) [203].

In the field of cancer immunotherapy, there has been a focus on chimeric antigen receptor (CAR)-T cells. CAR-T cells have proven to be effective in hematological malignancies, but solid tumors continue to be difficult. Recently there has been a movement toward using CAR-T models targeting the O-glycan epitopes Tn and STn, with development of CAR-T cells recognizing the Tn antigen expressed in MUC1. This anti-Tn-MUC1 CAR-T has demonstrated target-specific cytotoxicity and limiting tumor grown in mouse models [204]. A study in 2019 reported a novel monoclonal antibody TAB004 that is highly specific for the tumor form of MUC1 (tMUC1) that does not recognize normal mammary epithelium [205]. When TAB004 was injected into triple negative breast cancer (TNBC) cell (HCC70) bearing mice, TAB004 was found to be highly specific, only localizing to the tumor and not any other organs [206]. These results led to the development of CAR-T cell with a scFv sequence derived from TAB004. Functional analysis on these CAR-T cells demonstrated high tumor antigen specificity and strong cytolytic effects in TNBC both in vitro and in vivo [205].

There is continued need to understand the mechanisms by which O-glycosylation changes are causative in breast cancer. Although glycosyltransferases and TACAs have shown a strong presence in breast cancer, it has yet to translate to clinical practice. With further investigation, this can lead to new biomarkers and potential in the development of novel and specific targeted therapeutics that is presently a challenge.

MUC1 is overexpressed and aberrantly O-glycosylated in most adenocarcinomas, including breast and pancreatic cancers, and has long been considered a promising immunotherapeutic target [207]. Many groups have attempted development of unglycosylated MUC1 peptide vaccines [208–215]. These elicited humoral responses directed mainly to unglycosylated MUC1 and not to the aberrantly glycosylated MUC1 that is typically presented by cancer cells. Others have developed MUC1 fusion proteins for immunization. A pilot phase III study in early-stage breast cancer patients using one of these fusion proteins, oxidized mannan-MUC1, demonstrated no recurrence in 16 patients compared with 4 recurrences of 15 patients who received placebo [151]. Patients who received placebo showed no response to MUC1, whereas 9 of 13 patients immunized with MUC1 had developed MUC1-specific antibodies and 4 of 10 developed MUC1-specific T cell responses. While these results are promising, the generated antibodies still react with unglycosylated MUC1 and not underglycosylated MUC1 as it is presented by cancer cells [207].

Cancer-targeting antibody drugs, including antibody-drug conjugates are attractive opportunities, but their clinical success has been limited. Proteins are the typical targets of these antibody-based therapies. As discussed previously, the glycocalyx of cancer cell surfaces displays unique patterns of aberrant glycosylation. Therefore, targeting these aberrant glycans may be more effective than targeting the underlying core proteins. Lectins, or proteins that bind to glycans, are an alternative to antibodies. However, their development and study in vivo has been limited because they often have erythrocytic agglutination activity [216]. Shimomura et al. identified a lectin that possesses specific affinity to the glycans of cancer cell surfaces using a PDAC cell line (Capan-1), called rBC2LC-N [217]. They then constructed a lectin-drug conjugate (LDC) by fusing the lectin to a bacterial toxin. They identified positive reactivity not only in Capan-1 cells, but also in tissue from 69 PDAC patients. In contrast with many other lectins, rBC2LC-N did not cause hemagglutination with human erythrocytes and was safely administered to mice. Intraperitoneal administration of their LDC reduced tumor weight from 390 to 130.8 mg, reduced number of nodules from 48 to 3, and improved survival from 62 to 105 days. The effect of the LDC was reproduced in nodules from patient-derived PDAC xenografts through IV injection. These results are a very promising proof-of-concept that glycan-binding proteins targeting cancer-specific glycan alterations can effectively be used as drug carriers with clinical therapeutic benefit.

Abnormalities in O-glycan antigen expression, mucin glycosylation, and glycosyltransferase activity and localization characterize many carcinomas and thus represent valuable prospective therapeutic targets and subjects for ongoing investigation.

Concluding thoughts

Alterations in O-glycosylation represent defining characteristics of a number of human carcinomas, including colorectal, breast, and pancreatic adenocarcinomas; these aberrancies, which in large part have been elucidated through disease-specific mouse models, likely play a key role in tumorigenesis.

Breast, colon, and pancreatic cancer, as has been highlighted in this review, show the significance of glycosylation in the development, progression, and metastatic processes of each cancer type. It is also evident that variation in aberrant glycosylation processes contributes to each cancer type.

In this review, the presence of TACAs has been emphasized and the expression of these structures is associated with the mucin-type O-glycans. Although breast, colon, and pancreatic cancer all express TACAs (Table 1), the ways in which they cause disease are different and each cancer expresses varying levels of TACAs. While the presence of T and STn have been heavily observed in breast cancer, Tn and STn are also highly expressed in colon and pancreatic carcinoma. These TACAs affect the function of mucins expressed in each cancer type, thus affecting the growth and survival of the cell, its ability to invade and metastasize, and its interactions with lectins and cell-surface receptors or cells of the immune system.

As described here, altered expression of glycosyltransferases has been noted across breast, colon, and pancreatic cancer. Among these three types of cancers, each demonstrates differing ppGalNAc-Ts relative to normal tissue. The three types of cancer also share some similar aberrant GalNAc-Ts such as GalNAc-T6, which is reported to have increased expression in breast and colon cancer and ST6GalNAcI, which contributes to development of STn antigen among all three cancer types. Of course, there are also changes that are unique to each cancer type. These include the presence of GalNAc-Ts not expressed in normal tissue, such as GalNAc-T4, 14, and 9, which are uniquely associated with breast cancer pathology. Some pathologic differences result from lack of expression, as is seen in pancreatic cancer with C1GalT1.

Several murine models have aided remarkably in the elucidation of the specific O-glycosylation changes underlying the pathogenesis in CRC, ductal adenocarcinoma of the breast, and PDAC. Murine models of CRC feature tumorigenesis in the setting of colitis, reflective of human CRC arising in a background of IBD; these models are achieved through murine exposure to an inflammatory insult after either chemical sensitization or knockout of specific genes which ordinarily participate in forming the protective colorectal mucin barrier [49,108]. These models demonstrate that while certain mucins, including MUC2, confer resistance to inflammatory tumorigenesis, the physiologic presence of other specific mucins, including MUC1 and MUC4, increases susceptibility [109,122]. Furthermore, these models support patterns of compromised O-glycan elongation, resulting in the truncated O-glycans Tn, STn, T and ST antigens, as well as patterns of excessive sialylation and fucosylation, resulting in terminal antigens such as SLea and SLex [64,120].

Murine models of breast cancer feature xenografting of immortalized breast cancer cell lines into the mammary tissue of nude mice, and these models have corroborated the overexpression of truncated O-glycan structures such as the Tn and STn antigens, and their association with tumorigenesis and disease progression [155]. Additionally, murine breast cancer models have elucidated the functional role of these aberrant O-glycans in tumor metastasis; disruption of the interaction of the Tn antigen on cancer cells with mammary lymphatic endothelium results in the prevention of lymph node metastasis [154]. There are several murine models of pancreatic cancer which feature genetic knockouts that are not reflective of somatic mutations observed in humans, but which produce functional changes that parallel those in human pancreatic cancer [95,199]. Mice with genetically knocked out C1GALT1, together with mutations in Kras and p53, display overexpression of aberrantly truncated O-glycan structures, and these mice displayed accelerated progression to pancreatic cancer, early metastasis, and a 50% decrease in median survival [199]. Mice genetically engineered to express SLea, which is not expressed in wild type mice, have demonstrated functional participation of the SLea antigen in pancreatic cancer tumorigenesis and progression [95]. Murine models have proven useful tools in the examination of O-glycosylation changes and their functional roles in breast, pancreatic, and colorectal cancer, and the variation in the types of models are reflective of the different tumor types being studied.

Competing Interests

The authors declare that there are no competing interests associated with the manuscript.

Acknowledgements

The authors acknowledge funding from: NIH, grants U01CA168930 and P41GM103694 to RDC and K12HL141953 training grant to J.C. and K.A.S.; The Cummings Resident Research Fund at BIDMC to G.E.C., J.C., and K.A.S.

Abbreviations

     
  • ABPs

    antibacterial peptides

  •  
  • AOM

    azoxymethane

  •  
  • Asn

    asparagine

  •  
  • B3GALT5

    β1,3-galactosyltransferase 5

  •  
  • C3GnT

    core 3 β1,3-N-acetylglucosaminyltransferase

  •  
  • CAR

    chimeric antigen receptor

  •  
  • CMP

    carbohydrate mimicking peptide

  •  
  • CORA

    cellular O-glycome reporter/amplification

  •  
  • CRC

    Colorectal cancer

  •  
  • DMH

    dimethylhydrazine

  •  
  • Dox

    doxycycline

  •  
  • ELISA

    enzyme-linked immunosorbent assay

  •  
  • ER

    endoplasmic reticulum

  •  
  • ESI

    electrospray ionization

  •  
  • FUT3

    Fucosyltransferase 3

  •  
  • Gal

    galactose

  •  
  • GalNAc

    N-acetylgalactosamine

  •  
  • HPA

    Helix pomatia agglutinin

  •  
  • ICORA

    isotopic labeling with cellular O-glycome reporter/amplification

  •  
  • IEC

    intestinal epithelial cells

  •  
  • LDC

    lectin-drug conjugate

  •  
  • MALDI

    matrix assisted laser desorption/ionization

  •  
  • MAM

    methylazoxymethanol

  •  
  • MS

    mass spectrometry

  •  
  • PanIN

    pancreatic intraepithelial neoplasia

  •  
  • PDAC

    Pancreatic ductal adenocarcinoma

  •  
  • ppGalNAc-Ts

    polypeptide N-acetylgalactosaminyltransferases

  •  
  • Pro

    proline

  •  
  • Ser

    serine

  •  
  • SLea

    sialyl-Lewis a

  •  
  • SLex

    sialyl-Lewis x

  •  
  • ST3Gal-I

    β-galactoside α2,3-sialyltransferase-I

  •  
  • ST6GalNAcI

    α2,6-sialyltransferase-I

  •  
  • STn

    sialyl-Tn antigen

  •  
  • TACAs

    tumor-associated carbohydrate antigens

  •  
  • TF

    Thomsen–Friedenreich antigen

  •  
  • Thr

    threonine

  •  
  • Tn

    Tn antigen

  •  
  • Tyr

    tyrosine

  •  
  • UDP-GalNAc

    uridine diphospho-GalNAc

  •  
  • VLR

    variable lymphocyte receptors

  •  
  • VVA

    Vicia villosa agglutinin

References

References
1
Mehta
,
A.Y.
,
Heimburg-Molinaro
,
J.
,
Cummings
,
R.D.
and
Goth
,
C.K.
(
2020
)
Emerging patterns of tyrosine sulfation and O-glycosylation cross-talk and co-localization
.
Curr. Opin. Struct. Biol.
62
,
102
111
2
Beckwith
,
D.M.
and
Cudic
,
M.
(
2020
)
Tumor-associated O-glycans of MUC1: carriers of the glyco-code and targets for cancer vaccine design
.
Semin. Immunol.
47
,
101389
3
Urata
,
Y.
and
Takeuchi
,
H.
(
2019
)
Effects of Notch glycosylation on health and diseases
.
Dev. Growth Differ.
62
,
35
48
4
Scott
,
E.
,
Elliott
,
D.J.
and
Munkley
,
J.
(
2019
)
Tumour associated glycans: a route to boost immunotherapy?
Clin. Chim. Acta
502
,
167
173
5
Girotti
,
M.R.
,
Salatino
,
M.
,
Dalotto-Moreno
,
T.
and
Rabinovich
,
G.A.
(
2020
)
Sweetening the hallmarks of cancer: galectins as multifunctional mediators of tumor progression
.
J. Exp. Med.
217
,
e20182041
6
Harada
,
Y.
,
Ohkawa
,
Y.
,
Kizuka
,
Y.
and
Taniguchi
,
N.
(
2019
)
Oligosaccharyltransferase: a gatekeeper of health and tumor progression
.
Int. J. Mol. Sci.
20
,
E6074
7
Miyoshi
,
E.
,
Kamada
,
Y.
and
Suzuki
,
T.
(
2020
)
Functional glycomics: application to medical science and hepatology
.
Hepatol Res
50
,
153
164
8
Moll
,
T.
,
Shaw
,
P.J.
and
Cooper-Knock
,
J.
(
2019
)
Disrupted glycosylation of lipids and proteins is a cause of neurodegeneration
.
Brain
, awz358,
1
9
9
Varki
,
A.
,
Cummings
,
R.D.
,
Esko
,
J.D.
,
Freeze
,
H.H.
,
Stanley
,
P.
,
Bertozzi
,
C.R.
et al (
2017
)
Essentials of Glycobiology
, 3rd edn,
Cold Spring Harbor Laboratory Press
,
New York
10
Kudelka
,
M.R.
,
Ju
,
T.
,
Heimburg-Molinaro
,
J.
and
Cummings
,
R.D.
(
2015
)
Simple sugars to complex disease–mucin-type O-glycans in cancer
.
Adv. Cancer Res.
126
,
53
135
11
Stowell
,
S.R.
,
Ju
,
T.
and
Cummings
,
R.D.
(
2015
)
Protein glycosylation in cancer
.
Annu. Rev. Pathol.
10
,
473
510
12
Yoshida-Moriguchi
,
T.
and
Campbell
,
K.P.
(
2015
)
Matriglycan: a novel polysaccharide that links dystroglycan to the basement membrane
.
Glycobiology
25
,
702
713
13
Hart
,
G.W.
(
2019
)
Nutrient regulation of signaling and transcription
.
J. Biol. Chem.
294
,
2211
2231
14
Ng
,
B.G.
and
Freeze
,
H.H.
(
2018
)
Perspectives on glycosylation and its congenital disorders
.
Trends Genet.
34
,
466
476
15
Steentoft
,
C.
,
Vakhrushev
,
S.Y.
,
Joshi
,
H.J.
,
Kong
,
Y.
,
Vester-Christensen
,
M.B.
,
Schjoldager
,
K.T.
et al (
2013
)
Precision mapping of the human O-GalNAc glycoproteome through SimpleCell technology
.
EMBO J.
32
,
1478
1488
16
Chandler
,
K.B.
,
Costello
,
C.E.
and
Rahimi
,
N.
(
2019
)
Glycosylation in the tumor microenvironment: implications for tumor angiogenesis and metastasis
.
Cells
8
,
E544
17
Laubli
,
H.
and
Borsig
,
L.
(
2019
)
Altered cell adhesion and glycosylation promote cancer immune suppression and metastasis
.
Front. Immunol.
10
,
2120
18
Bennett
,
E.P.
,
Mandel
,
U.
,
Clausen
,
H.
,
Gerken
,
T.A.
,
Fritz
,
T.A.
and
Tabak
,
L.A.
(
2012
)
Control of mucin-type O-glycosylation: a classification of the polypeptide GalNAc-transferase gene family
.
Glycobiology
22
,
736
756
19
Ju
,
T.
,
Otto
,
V.I.
and
Cummings
,
R.D.
(
2011
)
The Tn antigen-structural simplicity and biological complexity
.
Angew. Chem. Int. Ed. Engl.
50
,
1770
1791
20
Ju
,
T.
and
Cummings
,
R.D.
(
2005
)
Chaperone mutation in Tn syndrome
.
Nature
437
,
1252
21
Kudelka
,
M.R.
,
Nairn
,
A.V.
,
Sardar
,
M.Y.
,
Sun
,
X.
,
Chaikof
,
E.L.
,
Ju
,
T.
et al (
2018
)
Isotopic labeling with cellular O-glycome reporter/amplification (ICORA) for comparative O-glycomics of cultured cells
.
Glycobiology
28
,
214
222
22
Kudelka
,
M.R.
,
Antonopoulos
,
A.
,
Wang
,
Y.
,
Duong
,
D.M.
,
Song
,
X.
,
Seyfried
,
N.T.
et al (
2016
)
Cellular O-glycome reporter/amplification to explore O-glycans of living cells
.
Nat. Methods
13
,
81
86
23
Holst
,
S.
,
Wuhrer
,
M.
and
Rombouts
,
Y.
(
2015
)
Glycosylation characteristics of colorectal cancer
.
Adv. Cancer Res.
126
,
203
256
24
Yin
,
B.W.
and
Lloyd
,
K.O.
(
2001
)
Molecular cloning of the CA125 ovarian cancer antigen: identification as a new mucin, MUC16
.
J. Biol. Chem.
276
,
27371
27375
25
Nuti
,
M.
,
Teramoto
,
Y.A.
,
Mariani-Costantini
,
R.
,
Hand
,
P.H.
,
Colcher
,
D.
and
Schlom
,
J.
(
1982
)
A monoclonal antibody (B72.3) defines patterns of distribution of a novel tumor-associated antigen in human mammary carcinoma cell populations
.
Int. J. Cancer
29
,
539
545
26
Magnani
,
J.L.
,
Steplewski
,
Z.
,
Koprowski
,
H.
and
Ginsburg
,
V.
(
1983
)
Identification of the gastrointestinal and pancreatic cancer-associated antigen detected by monoclonal antibody 19-9 in the sera of patients as a mucin
.
Cancer Res.
43
,
5489
5492
PMID:
[PubMed]
27
Gendler
,
S.J.
,
Lancaster
,
C.A.
,
Taylor-Papadimitriou
,
J.
,
Duhig
,
T.
,
Peat
,
N.
,
Burchell
,
J.
et al (
1990
)
Molecular cloning and expression of human tumor-associated polymorphic epithelial mucin
.
J. Biol. Chem.
265
,
15286
15293
PMID:
[PubMed]
28
Gendler
,
S.J.
,
Cohen
,
E.P.
,
Craston
,
A.
,
Duhig
,
T.
,
Johnstone
,
G.
and
Barnes
,
D.
(
1990
)
The locus of the polymorphic epithelial mucin (PEM) tumour antigen on chromosome 1q21 shows a high frequency of alteration in primary human breast tumours
.
Int. J. Cancer
45
,
431
435
29
Ludwig
,
J.A.
and
Weinstein
,
J.N.
(
2005
)
Biomarkers in cancer staging, prognosis and treatment selection
.
Nat. Rev. Cancer
5
,
845
856
30
Cummings
,
R.D.
(
2009
)
The repertoire of glycan determinants in the human glycome
.
Mol. Biosyst.
5
,
1087
1104
31
Han
,
Y.Y.
,
Liu
,
H.-Y.
,
Han
,
D.-J.
,
Zong
,
X.-C.
,
Zhang
,
S.-Q.
and
Chen
,
Y.-Q.
(
2013
)
Role of glycosylation in the anticancer activity of antibacterial peptides against breast cancer cells
.
Biochem. Pharmacol.
86
,
1254
1262
32
Collins
,
B.C.
,
Gunn
,
R.J.
,
McKitrick
,
T.R.
,
Cummings
,
R.D.
,
Cooper
,
M.D.
,
Herrin
,
B.R.
et al (
2017
)
Structural insights into VLR fine specificity for blood group carbohydrates
.
Structure
25
,
1667
1678 e1664
33
Sun
,
X.
,
Ju
,
T.
and
Cummings
,
R.D.
(
2018
)
Differential expression of Cosmc, T-synthase and mucins in Tn-positive colorectal cancers
.
BMC Cancer
18
,
827
34
Barrow
,
H.
,
Guo
,
X.
,
Wandall
,
H.H.
,
Pedersen
,
J.W.
,
Fu
,
B.
,
Zhao
,
Q.
et al (
2011
)
Serum galectin-2, -4, and -8 are greatly increased in colon and breast cancer patients and promote cancer cell adhesion to blood vascular endothelium
.
Clin. Cancer Res.
17
,
7035
7046
35
Štefatić
,
D.
,
Riederer
,
M.
,
Balić
,
M.
,
Dandachi
,
N.
,
Stanzer
,
S.
,
Janesch
,
B.
et al (
2008
)
Optimization of diagnostic ELISA-based tests for the detection of auto-antibodies against tumor antigens in human serum
.
Bosn. J. Basic Med. Sci.
8
,
245
250
36
Saeland
,
E.
,
Belo
,
A.I.
,
Mongera
,
S.
,
van Die
,
I.
,
Meijer
,
G.A.
and
van Kooyk
,
Y.
(
2012
)
Differential glycosylation of MUC1 and CEACAM5 between normal mucosa and tumour tissue of colon cancer patients
.
Int. J. Cancer
131
,
117
128
37
Cui
,
H.-X.
,
Wang
,
H.
,
Wang
,
Y.
,
Song
,
J.
,
Tian
,
H.
,
Xia
,
C.
et al (
2016
)
ST3Gal III modulates breast cancer cell adhesion and invasion by altering the expression of invasion-related molecules
.
Oncol. Rep.
36
,
3317
3324
38
Shiozaki
,
K.
,
Yamaguchi
,
K.
,
Takahashi
,
K.
,
Moriya
,
S.
and
Miyagi
,
T.
(
2011
)
Regulation of sialyl Lewis antigen expression in colon cancer cells by sialidase NEU4
.
J Biol Chem
286
,
21052
21061
39
Kirmiz
,
C.
,
Li
,
B.
,
An
,
H.J.
,
Clowers
,
B.H.
,
Chew
,
H.K.
,
Lam
,
K.S.
et al (
2007
)
A serum glycomics approach to breast cancer biomarkers
.
Mol. Cell. Proteomics
6
,
43
55
40
Cummings
,
R.D.
and
Pierce
,
J.M.
(
2014
)
The challenge and promise of glycomics
.
Chem. Biol.
21
,
1
15
41
Furukawa
,
J.
,
Fujitani
,
N.
and
Shinohara
,
Y.
(
2013
)
Recent advances in cellular glycomic analyses
.
Biomolecules
3
,
198
225
42
Wang
,
T.
and
Voglmeir
,
J.
(
2014
)
PNGases as valuable tools in glycoprotein analysis
.
Protein Pept. Lett.
21
,
976
985
43
Xia
,
B.
,
Royall
,
J.A.
,
Damera
,
G.
,
Sachdev
,
G.P.
and
Cummings
,
R.D.
(
2005
)
Altered O-glycosylation and sulfation of airway mucins associated with cystic fibrosis
.
Glycobiology
15
,
747
775
44
Arike
,
L.
and
Hansson
,
G.C.
(
2016
)
The densely O-glycosylated MUC2 mucin protects the intestine and provides food for the commensal bacteria
.
J. Mol. Biol.
428
,
3221
3229
46
Yaffee
,
P.
,
Osipov
,
A.
,
Tan
,
C.
,
Tuli
,
R.
and
Hendifar
,
A.
(
2015
)
Review of systemic therapies for locally advanced and metastatic rectal cancer
.
J. Gastrointest. Oncol.
6
,
185
200
47
Venkitachalam
,
S.
and
Guda
,
K.
(
2017
)
Altered glycosyltransferases in colorectal cancer
.
Expert Rev. Gastroenterol. Hepatol.
11
,
5
7
48
Pinho
,
S.S.
and
Reis
,
C.A.
(
2015
)
Glycosylation in cancer: mechanisms and clinical implications
.
Nat. Rev. Cancer
15
,
540
555
49
Sheng
,
Y.H.
,
Hasnain
,
S.Z.
,
Florin
,
T.H.
and
McGuckin
,
M.A.
(
2012
)
Mucins in inflammatory bowel diseases and colorectal cancer
.
J. Gastroenterol. Hepatol.
27
,
28
38
50
Brockhausen
,
I.
(
2006
)
Mucin-type O-glycans in human colon and breast cancer: glycodynamics and functions
.
EMBO Rep.
7
,
599
604
51
Venkitachalam
,
S.
,
Revoredo
,
L.
,
Varadan
,
V.
,
Fecteau
,
R.E.
,
Ravi
,
L.
,
Lutterbaugh
,
J.
et al (
2016
)
Biochemical and functional characterization of glycosylation-associated mutational landscapes in colon cancer
.
Sci. Rep.
6
,
23642
52
Zhang
,
L.
and
Ten Hagen
,
K.G.
(
2018
)
Pleiotropic effects of O-glycosylation in colon cancer
.
J. Biol. Chem.
293
,
1315
1316
53
van der Post
,
S.
and
Hansson
,
G.C.
(
2014
)
Membrane protein profiling of human colon reveals distinct regional differences
.
Mol. Cell. Proteomics
13
,
2277
2287
54
Marcos
,
N.T.
,
Pinho
,
S.
,
Grandela
,
C.
,
Cruz
,
A.
,
Samyn-Petit
,
B.
,
Harduin-Lepers
,
A.
et al (
2004
)
Role of the human ST6GalNAc-I and ST6GalNAc-II in the synthesis of the cancer-associated sialyl-Tn antigen
.
Cancer Res.
64
,
7050
7057
55
Lavrsen
,
K.
,
Dabelsteen
,
S.
,
Vakhrushev
,
S.Y.
,
Levann
,
A.M.R.
,
Haue
,
A.D.
,
Dylander
,
A.
et al (
2018
)
De novo expression of human polypeptide N-acetylgalactosaminyltransferase 6 (GalNAc-T6) in colon adenocarcinoma inhibits the differentiation of colonic epithelium
.
J. Biol. Chem.
293
,
1298
1314
56
Guda
,
K.
,
Moinova
,
H.
,
He
,
J.
,
Jamison
,
O.
,
Ravi
,
L.
,
Natale
,
L.
et al (
2009
)
Inactivating germ-line and somatic mutations in polypeptide N-acetylgalactosaminyltransferase 12 in human colon cancers
.
Proc. Natl Acad. Sci. U.S.A.
106
,
12921
12925
57
Marcos
,
N.T.
,
Bennett
,
E.P.
,
Gomes
,
J.
,
Magalhaes
,
A.
,
Gomes
,
C.
,
David
,
L.
et al (
2011
)
ST6GalNAc-I controls expression of sialyl-Tn antigen in gastrointestinal tissues
.
Front. Biosci.
3
,
1443
1455
58
Sewell
,
R.
,
Bäckström
,
M.
,
Dalziel
,
M.
,
Gschmeissner
,
S.
,
Karlsson
,
H.
,
Noll
,
T.
et al (
2006
)
The ST6GalNAc-I sialyltransferase localizes throughout the Golgi and is responsible for the synthesis of the tumor-associated sialyl-Tn O-glycan in human breast cancer
.
J. Biol. Chem.
281
,
3586
3594
59
Lise
,
M.
,
Belluco
,
C.
,
Perera
,
S.P.
,
Patel
,
R.
,
Thomas
,
P.
and
Ganguly
,
A.
(
2000
)
Clinical correlations of alpha2,6-sialyltransferase expression in colorectal cancer patients
.
Hybridoma
19
,
281
286
60
Gao
,
T.
,
Du
,
T.
,
Hu
,
X.
,
Dong
,
X.
,
Li
,
L.
,
Wang
,
Y.
et al (
2020
)
Cosmc overexpression enhances malignancies in human colon cancer
.
J. Cell. Mol. Med.
24
,
362
370
61
Huang
,
J.
,
Che
,
M.-I.
,
Lin
,
N.-Y.
,
Hung
,
J.-S.
,
Huang
,
Y.-T.
,
Lin
,
W.-C.
et al (
2014
)
The molecular chaperone Cosmc enhances malignant behaviors of colon cancer cells via activation of Akt and ERK
.
Mol Carcinog
53
,
E62
E71
62
He
,
Y.
,
Schreiber
,
K.
,
Wolf
,
S.P.
,
Wen
,
F.
,
Steentoft
,
C.
,
Zerweck
,
J.
et al (
2019
)
Multiple cancer-specific antigens are targeted by a chimeric antigen receptor on a single cancer cell
.
JCI Insight
4
,
130416
.
63
Mi
,
R.
,
Song
,
L.
,
Wang
,
Y.
,
Ding
,
X.
,
Zeng
,
J.
,
Lehoux
,
S.
et al (
2012
)
Epigenetic silencing of the chaperone Cosmc in human leukocytes expressing tn antigen
.
J. Biol. Chem.
287
,
41523
41533
64
Radhakrishnan
,
P.
,
Dabelsteen
,
S.
,
Madsen
,
F.B.
,
Francavilla
,
C.
,
Kopp
,
K.L.
,
Steentoft
,
C.
et al (
2014
)
Immature truncated O-glycophenotype of cancer directly induces oncogenic features
.
Proc. Natl Acad. Sci. U.S.A.
111
,
E4066
E4075
65
Gill
,
D.J.
,
Clausen
,
H.
and
Bard
,
F.
(
2011
)
Location, location, location: new insights into O-GalNAc protein glycosylation
.
Trends Cell Biol.
21
,
149
158
66
Vavasseur
,
F.
,
Dole
,
K.
,
Yang
,
J.
,
Matta
,
K.L.
,
Myerscough
,
N.
,
Corfield
,
A.
et al (
1994
)
O-glycan biosynthesis in human colorectal adenoma cells during progression to cancer
.
Eur. J. Biochem.
222
,
415
424
67
Itzkowitz
,
S.H.
,
Yuan
,
M.
,
Montgomery
,
C.K.
,
Kjeldsen
,
T.
,
Takahashi
,
H.K.
,
Bigbee
,
W.L.
et al (
1989
)
Expression of Tn, sialosyl-Tn, and T antigens in human colon cancer
.
Cancer Res.
49
,
197
204
PMID:
[PubMed]
68
Springer
,
G.F.
(
1997
)
Immunoreactive T and Tn epitopes in cancer diagnosis, prognosis, and immunotherapy
.
J. Mol. Med.
75
,
594
602
69
Brooks
,
S.A.
(
2000
)
The involvement of helix pomatia lectin (HPA) binding N-acetylgalactosamine glycans in cancer progression
.
Histol. Histopathol.
15
,
143
158
70
Konska
,
G.
,
Guerry
,
M.
,
Caldefie-Chezet
,
F.
,
De Latour
,
M.
and
Guillot
,
J.
(
2006
)
Study of the expression of Tn antigen in different types of human breast cancer cells using VVA-B4 lectin
.
Oncol. Rep.
15
,
305
310
71
Brooks
,
S.A.
and
Leathem
,
A.J.
(
1991
)
Prediction of lymph node involvement in breast cancer by detection of altered glycosylation in the primary tumour
.
Lancet
338
,
71
74
72
Kawaguchi
,
T.
,
Takazawa
,
H.
,
Imai
,
S.
,
Morimoto
,
J.
,
Watanabe
,
T.
,
Kanno
,
M.
et al (
2006
)
Expression of vicia villosa agglutinin (VVA)-binding glycoprotein in primary breast cancer cells in relation to lymphatic metastasis: is atypical MUC1 bearing Tn antigen a receptor of VVA?
Breast Cancer Res. Treat.
98
,
31
43
73
Leathem
,
A.J.
and
Brooks
,
S.A.
(
1987
)
Predictive value of lectin binding on breast-cancer recurrence and survival
.
Lancet
329
,
1054
1056
74
Munkley
,
J.
and
Elliott
,
D.J.
(
2016
)
Hallmarks of glycosylation in cancer
.
Oncotarget
7
,
35478
35489
75
Hofmann
,
B.T.
,
Schlüter
,
L.
,
Lange
,
P.
,
Mercanoglu
,
B.
,
Ewald
,
F.
,
Fölster
,
A.
et al (
2015
)
COSMC knockdown mediated aberrant O-glycosylation promotes oncogenic properties in pancreatic cancer
.
Mol. Cancer
14
,
109
76
Ikehara
,
Y.
,
Kojima
,
N.
,
Kurosawa
,
N.
,
Kudo
,
T.
,
Kono
,
M.
,
Nishihara
,
S.
et al (
1999
)
Cloning and expression of a human gene encoding an N-acetylgalactosamine-α2,6-sialyltransferase (ST6GalNAc I): a candidate for synthesis of cancer-associated sialyl-Tn antigens
.
Glycobiology
9
,
1213
1224
77
Colcher
,
D.
,
Hand
,
P.H.
,
Nuti
,
M.
and
Schlom
,
J.
(
1981
)
A spectrum of monoclonal antibodies reactive with human mammary tumor cells
.
Proc. Natl Acad. Sci. U.S.A.
78
,
3199
3203
78
Thor
,
A.
,
Ohuchi
,
N.
,
Schlom
,
J.
,
Szpak
,
C.A.
and
Johnston
,
W.W.
(
1986
)
Distribution of oncofetal antigen tumor–associated glycoprotein-72 defined by monoclonal antibody B72.3
.
Cancer Res.
46
,
3118
3124
PMID:
[PubMed]
79
Miles
,
D.W.
,
Happerfield
,
L.C.
,
Smith
,
P.
,
Gillibrand
,
R.
,
Bobrow
,
L.G.
,
Gregory
,
W.M.
et al (
1994
)
Expression of sialyl-Tn predicts the effect of adjuvant chemotherapy in node-positive breast cancer
.
Br. J. Cancer
70
,
1272
1275
80
Springer
,
G.F.
,
Desai
,
P.R.
,
Murthy
,
M.S.
and
Scanlon
,
E.F.
(
1979
)
Human carcinoma-associated precursor antigens of the NM blood group system
.
J. Surg. Oncol.
11
,
95
106
81
Schindlbeck
,
C.
,
Jeschke
,
U.
,
Schulze
,
S.
,
Karsten
,
U.
,
Janni
,
W.
,
Rack
,
B.
et al (
2005
)
Characterisation of disseminated tumor cells in the bone marrow of breast cancer patients by the Thomsen-Friedenreich tumor antigen
.
Histochem. Cell Biol.
123
,
631
637
82
Brockhausen
,
I.
,
Yang
,
J.M.M.
,
Burchell
,
J.
,
Whitehouse
,
C.
and
Taylor-Papadimitriou
,
J.
(
1995
)
Mechanisms underlying aberrant glycosylation of MUC1 mucin in breast cancer cells
.
Eur. J. Biochem.
233
,
607
617
83
Yu
,
L.G.
,
Andrews
,
N.
,
Zhao
,
Q.
,
McKean
,
D.
,
Williams
,
J.F.
,
Connor
,
L.J.
et al (
2007
)
Galectin-3 interaction with Thomsen-Friedenreich disaccharide on cancer-associated MUC1 causes increased cancer cell endothelial adhesion
.
J. Biol. Chem.
282
,
773
781
84
Sakamoto
,
J.
,
Furukawa
,
K.
,
Cordon-Cardo
,
C.
,
Yin
,
B.W.
,
Rettig
,
W.J.
,
Oettgen
,
H.F.
et al (
1986
)
Expression of Lewisa, Lewisb, X, and Y blood group antigens in human colonic tumors and normal tissue and in human tumor-derived cell lines
.
Cancer Res.
46
,
1553
1561
PMID:
[PubMed]
85
Balmaña
,
M.
,
Sarrats
,
A.
,
Llop
,
E.
,
Barrabés
,
S.
,
Saldova
,
R.
,
Ferri
,
M.J.
et al (
2015
)
Identification of potential pancreatic cancer serum markers: increased sialyl-Lewis X on ceruloplasmin
.
Clin. Chim. Acta
442
,
56
62
86
Tang
,
H.
,
Singh
,
S.
,
Partyka
,
K.
,
Kletter
,
D.
,
Hsueh
,
P.
,
Yadav
,
J.
et al (
2015
)
Glycan motif profiling reveals plasma sialyl-lewis x elevations in pancreatic cancers that are negative for sialyl-lewis A
.
Mol. Cell. Proteomics
14
,
1323
1333
87
Takahashi
,
S.
,
Oda
,
T.
,
Hasebe
,
T.
,
Sasaki
,
S.
,
Kinoshita
,
T.
,
Konishi
,
M.
et al (
2001
)
Overexpression of sialyl Lewis x antigen is associated with formation of extratumoral venous invasion and predicts postoperative development of massive hepatic metastasis in cases with pancreatic ductal adenocarcinoma
.
Pathobiology
69
,
127
135
88
Natoni
,
A.
,
Macauley
,
M.S.
and
O'Dwyer
,
M.E.
(
2016
)
Targeting selectins and their ligands in cancer
.
Frontiers in Oncology
6
,
93
89
Rho
,
J.H.
,
Mead
,
J.R.
,
Wright
,
W.S.
,
Brenner
,
D.E.
,
Stave
,
J.W.
,
Gildersleeve
,
J.C.
et al (
2014
)
Discovery of sialyl Lewis A and Lewis X modified protein cancer biomarkers using high density antibody arrays
.
J. Proteomics
96
,
291
299
90
Fujita
,
T.
,
Murayama
,
K.
,
Hanamura
,
T.
,
Okada
,
T.
,
Ito
,
T.
,
Harada
,
M.
et al (
2011
)
CSLEX (Sialyl Lewis X) is a useful tumor marker for monitoring of breast cancer patients
.
Jpn. J. Clin. Oncol.
41
,
394
399
91
Cohen
,
E.N.
,
Fouad
,
T.M.
,
Lee
,
B.-N.
,
Arun
,
B.K.
,
Liu
,
D.
,
Tin
,
S.
et al (
2019
)
Elevated serum levels of sialyl Lewis X (sLe(X)) and inflammatory mediators in patients with breast cancer
.
Breast Cancer Res. Treat.
176
,
545
556
92
Ito
,
H.
,
Hiraiwa
,
N.
,
Sawada-Kasugai
,
M.
,
Akamatsu
,
S.
,
Tachikawa
,
T.
,
Kasai
,
Y.
et al (
1997
)
Altered mRNA expression of specific molecular species of fucosyl- and sialyl-transferases in human colorectal cancer tissues
.
Int. J. Cancer
71
,
556
564
93
Muinelo-Romay
,
L.
,
Gil-Martin
,
E.
and
Fernandez-Briera
,
A.
(
2010
)
Alpha(1,2)fucosylation in human colorectal carcinoma
.
Oncol. Lett.
1
,
361
366
94
Yue
,
T.
,
Maupin
,
K.A.
,
Fallon
,
B.
,
Li
,
L.
,
Partyka
,
K.
,
Anderson
,
M.A.
et al (
2011
)
Enhanced discrimination of malignant from benign pancreatic disease by measuring the CA 19-9 antigen on specific protein carriers
.
PLoS ONE
6
,
e29180
95
Engle
,
D.D.
,
Tiriac
,
H.
,
Rivera
,
K.D.
,
Pommier
,
A.
,
Whalen
,
S.
,
Oni
,
T.E.
et al (
2019
)
The glycan CA19-9 promotes pancreatitis and pancreatic cancer in mice
.
Science
364
,
1156
1162
96
Ju
,
T.
,
Lanneau
,
G.S.
,
Gautam
,
T.
,
Wang
,
Y.
,
Xia
,
B.
,
Stowell
,
S.R.
et al (
2008
)
Human tumor antigens Tn and sialyl Tn arise from mutations in Cosmc
.
Cancer Res.
68
,
1636
1646
97
Oshikiri
,
T.
,
Miyamoto
,
M.
,
Morita
,
T.
,
Fujita
,
M.
,
Miyasaka
,
Y.
,
Senmaru
,
N.
et al (
2006
)
Tumor-associated antigen recognized by the 22-1-1 monoclonal antibody encourages colorectal cancer progression under the scanty CD8+ T cells
.
Clin. Cancer Res.
12
,
411
416
98
Matsumoto
,
Y.
,
Kudelka
,
M.R.
,
Hanes
,
M.S.
,
Lehoux
,
S.
,
Dutta
,
S.
,
Jones
,
M.B.
et al (
2019
)
Identification of Tn antigen O-GalNAc-expressing glycoproteins in human carcinomas using novel anti-Tn recombinant antibodies
.
Glycobiology
,
cwz095
99
Hollingsworth
,
M.A.
and
Swanson
,
B.J.
(
2004
)
Mucins in cancer: protection and control of the cell surface
.
Nat. Rev. Cancer
4
,
45
60
100
Kufe
,
D.W.
(
2009
)
Mucins in cancer: function, prognosis and therapy
.
Nat. Rev. Cancer
9
,
874
885
101
An
,
G.
,
Wei
,
B.
,
Xia
,
B.
,
McDaniel
,
J.M.
,
Ju
,
T.
,
Cummings
,
R.D.
et al (
2007
)
Increased susceptibility to colitis and colorectal tumors in mice lacking core 3-derived O-glycans
.
J. Exp. Med.
204
,
1417
1429
102
Fu
,
J.
,
Wei
,
B.
,
Wen
,
T.
,
Johansson
,
M.E.V.
,
Liu
,
X.
,
Bradford
,
E.
et al (
2011
)
Loss of intestinal core 1-derived O-glycans causes spontaneous colitis in mice
.
J. Clin. Invest.
121
,
1657
1666
103
van der Post
,
S.
,
Subramani
,
D.B.
,
Bäckström
,
M.
,
Johansson
,
M.E.V.
,
Vester-Christensen
,
M.B.
,
Mandel
,
U.
et al (
2013
)
Site-specific O-glycosylation on the MUC2 mucin protein inhibits cleavage by the porphyromonas gingivalis secreted cysteine protease (RgpB)
.
J. Biol. Chem.
288
,
14636
14646
104
Bergstrom
,
K.S.
and
Xia
,
L.
(
2013
)
Mucin-type O-glycans and their roles in intestinal homeostasis
.
Glycobiology
23
,
1026
1037
105
Taylor-Papadimitriou
,
J.
,
Burchell
,
J.
,
Miles
,
D.W.
and
Dalziel
,
M.
(
1999
)
MUC1 and cancer
.
Biochim. Biophys. Acta
1455
,
301
313
106
Johansson
,
M.E.
,
Phillipson
,
M.
,
Petersson
,
J.
,
Velcich
,
A.
,
Holm
,
L.
and
Hansson
,
G.C.
(
2008
)
The inner of the two Muc2 mucin-dependent mucus layers in colon is devoid of bacteria
.
Proc. Natl Acad. Sci. U.S.A.
105
,
15064
15069
107
Atuma
,
C.
,
Strugala
,
V.
,
Allen
,
A.
and
Holm
,
L.
(
2001
)
The adherent gastrointestinal mucus gel layer: thickness and physical state in vivo
.
Am. J. Physiol. Gastrointest. Liver Physiol.
280
,
G922
G929
108
McGuckin
,
M.A.
,
Linden
,
S.K.
,
Sutton
,
P.
and
Florin
,
T.H.
(
2011
)
Mucin dynamics and enteric pathogens
.
Nat. Rev. Microbiol.
9
,
265
278
109
Das
,
S.
,
Rachagani
,
S.
,
Sheinin
,
Y.
,
Smith
,
L.M.
,
Gurumurthy
,
C.B.
,
Roy
,
H.K.
et al (
2016
)
Mice deficient in Muc4 are resistant to experimental colitis and colitis-associated colorectal cancer
.
Oncogene
35
,
2645
2654
110
Sheng
,
Y.H.
,
Lourie
,
R.
,
Linden
,
S.K.
,
Jeffery
,
P.L.
,
Roche
,
D.
,
Tran
,
T.V.
et al (
2011
)
The MUC13 cell-surface mucin protects against intestinal inflammation by inhibiting epithelial cell apoptosis
.
Gut
60
,
1661
1670
111
Velcich
,
A.
,
Yang
,
W.
,
Heyer
,
J.
,
Fragale
,
A.
,
Nicholas
,
C.
,
Viani
,
S.
et al (
2002
)
Colorectal cancer in mice genetically deficient in the mucin Muc2
.
Science
295
,
1726
1729
112
Kawashima
,
H.
(
2012
)
Roles of the gel-forming MUC2 mucin and its O-glycosylation in the protection against colitis and colorectal cancer
.
Biol. Pharm. Bull.
35
,
1637
1641
113
Blank
,
M.
,
Klussmann
,
E.
,
Krüger-Krasagakes
,
S.
,
Schmitt-Gräff
,
A.
,
Stolte
,
M.
,
Bornhoeft
,
G.
et al (
1994
)
Expression of MUC2-mucin in colorectal adenomas and carcinomas of different histological types
.
Int. J. Cancer
59
,
301
306
114
Ullman
,
T.A.
and
Itzkowitz
,
S.H.
(
2011
)
Intestinal inflammation and cancer
.
Gastroenterology
140
,
1807
1816.e1
115
Tanaka
,
T.
(
2009
)
Colorectal carcinogenesis: review of human and experimental animal studies
.
J. Carcinogenesis
8
,
5
116
Snider
,
A.J.
,
Bialkowska
,
A.B.
,
Ghaleb
,
A.M.
,
Yang
,
V.W.
,
Obeid
,
L.M.
and
Hannun
,
Y.A.
(
2016
)
Murine model for colitis-associated cancer of the colon
.
Methods Mol. Biol.
1438
,
245
254
117
Rosenberg
,
D.W.
,
Giardina
,
C.
and
Tanaka
,
T.
(
2009
)
Mouse models for the study of colon carcinogenesis
.
Carcinogenesis
30
,
183
196
118
Tanaka
,
T.
(
2012
)
Development of an inflammation-associated colorectal cancer model and its application for research on carcinogenesis and chemoprevention
.
Int. J. Inflam.
2012
,
658786
119
Tanaka
,
T.
,
Suzuki
,
R.
,
Kohno
,
H.
,
Sugie
,
S.
,
Takahashi
,
M.
and
Wakabayashi
,
K.
(
2005
)
Colonic adenocarcinomas rapidly induced by the combined treatment with 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and dextran sodium sulfate in male ICR mice possess beta-catenin gene mutations and increases immunoreactivity for beta-catenin, cyclooxygenase-2 and inducible nitric oxide synthase
.
Carcinogenesis
26
,
229
238
120
Carvalho
,
A.S.
,
Harduin-Lepers
,
A.
,
Magalhães
,
A.
,
Machado
,
E.
,
Mendes
,
N.
,
Costa
,
L.T.
et al (
2010
)
Differential expression of alpha-2,3-sialyltransferases and alpha-1,3/4-fucosyltransferases regulates the levels of sialyl Lewis a and sialyl Lewis x in gastrointestinal carcinoma cells
.
Int. J. Biochem. Cell Biol.
42
,
80
89
121
Schwerbrock
,
N.M.
,
Makkink
,
M.K.
,
van der Sluis
,
M.
,
Büller
,
H.A.
,
Einerhand
,
A.W.C.
,
Sartor
,
R.B.
et al (
2004
)
Interleukin 10-deficient mice exhibit defective colonic Muc2 synthesis before and after induction of colitis by commensal bacteria
.
Inflamm. Bowel Dis.
10
,
811
823
122
Van der Sluis
,
M.
,
De Koning
,
B.A.E.
,
De Bruijn
,
A.C.J.M.
,
Velcich
,
A.
,
Meijerink
,
J.P.P.
,
Van Goudoever
,
J.B.
et al (
2006
)
Muc2-deficient mice spontaneously develop colitis, indicating that MUC2 is critical for colonic protection
.
Gastroenterology
131
,
117
129
123
Bergstrom
,
K.
,
Liu
,
X.
,
Zhao
,
Y.
,
Gao
,
N.
,
Wu
,
Q.
,
Song
,
K.
et al (
2016
)
Defective intestinal mucin-type o-glycosylation causes spontaneous colitis-associated cancer in mice
.
Gastroenterology
151
,
152
164.e111
124
Baldus
,
S.E.
and
Hanisch
,
F.G.
(
2000
)
Biochemistry and pathological importance of mucin-associated antigens in gastrointestinal neoplasia
.
Adv. Cancer Res.
79
,
201
248
125
Matsen
,
C.B.
and
Neumayer
,
L.A.
(
2013
)
Breast cancer: a review for the general surgeon
.
JAMA Surg.
148
,
971
979
126
Mariotto
,
A.B.
,
Etzioni
,
R.
,
Hurlbert
,
M.
,
Penberthy
,
L.
and
Mayer
,
M.
(
2017
)
Estimation of the number of women living with metastatic breast cancer in the United States
.
Cancer Epidemiol. Biomarkers Prev.
26
,
809
815
127
Hubbard
,
R.A.
,
Kerlikowske
,
K.
,
Flowers
,
C.I.
,
Yankaskas
,
B.C.
,
Zhu
,
W.
and
Miglioretti
,
D.L.
(
2011
)
Cumulative probability of false-positive recall or biopsy recommendation after 10 years of screening mammography: a cohort study
.
Ann. Intern. Med.
155
,
481
492
128
Burchell
,
J.M.
,
Mungul
,
A.
and
Taylor-Papadimitriou
,
J.
(
2001
)
O-linked glycosylation in the mammary gland: changes that occur during malignancy
.
J. Mammary Gland Biol. Neoplasia
6
,
355
364
129
Ju
,
T.
,
Aryal
,
R.P.
,
Kudelka
,
M.R.
,
Wang
,
Y.
and
Cummings
,
R.D.
(
2014
)
The Cosmc connection to the Tn antigen in cancer
.
Cancer Biomarkers
14
,
63
81
130
Ju
,
T.
,
Wang
,
Y.
,
Aryal
,
R.P.
,
Lehoux
,
S.D.
,
Ding
,
X.
,
Kudelka
,
M.R.
et al (
2013
)
Tn and sialyl-Tn antigens, aberrant O-glycomics as human disease markers
.
Proteomics
7
,
618
631
131
Springer
,
G.F.
(
1984
)
T and Tn, general carcinoma autoantigens
.
Science
224
,
1198
1206
132
Cazet
,
A.
,
Julien
,
S.
,
Bobowski
,
M.
,
Burchell
,
J.
and
Delannoy
,
P.
(
2010
)
Tumour-associated carbohydrate antigens in breast cancer
.
Breast Cancer Res.
12
,
1
13
133
Burchell
,
J.M.
,
Beatson
,
R.
,
Graham
,
R.
,
Taylor-Papadimitriou
,
J.
and
Tajadura-Ortega
,
V.
(
2018
)
O-linked mucin-type glycosylation in breast cancer
.
Biochem. Soc. Trans.
46
,
779
788
134
Berois
,
N.
,
Mazal
,
D.
,
Ubillos
,
L.
,
Trajtenberg
,
F.
,
Nicolas
,
A.
,
Sastre-Garau
,
X.
et al (
2006
)
UDP-N-acetyl-D-galactosamine: polypeptide N-acetylgalactosaminyltransferase-6 as a new immunohistochemical breast cancer marker
.
J. Histochem. Cytochem.
54
,
317
328
135
Freire
,
T.
,
Berois
,
N.
,
Sóñora
,
C.
,
Varangot
,
M.
,
Barrios
,
E.
and
Osinaga
,
E.
(
2006
)
UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 6 (ppGalNAc-T6) mRNA as a potential new marker for detection of bone marrow-disseminated breast cancer cells
.
Int. J. Cancer
119
,
1383
1388
136
Banford
,
S.
and
Timson
,
D.J.
(
2017
)
UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase- 6 (pp-GalNAc-T6): role in cancer and prospects as a drug target
.
Curr. Cancer Drug Targets
17
,
53
61
137
Park
,
J.H.
,
Nishidate
,
T.
,
Kijima
,
K.
,
Ohashi
,
T.
,
Takegawa
,
K.
,
Fujikane
,
T.
et al (
2010
)
Critical roles of mucin 1 glycosylation by transactivated polypeptide N-acetylgalactosaminyltransferase 6 in mammary carcinogenesis
.
Cancer Res.
70
,
2759
2769
138
Niang
,
B.
,
Jin
,
L.
,
Chen
,
X.
,
Guo
,
X.
,
Zhang
,
H.
,
Wu
,
Q.
et al (
2016
)
GalNAc-T4 putatively modulates the estrogen regulatory network through FOXA1 glycosylation in human breast cancer cells
.
Mol. Cell. Biochem.
411
,
393
402
139
Zhang
,
J.
,
Zhang
,
Z.
,
Wang
,
Q.
,
Xing
,
X.J.
and
Zhao
,
Y.
(
2016
)
Overexpression of microRNA-365 inhibits breast cancer cell growth and chemo-resistance through GALNT4
.
Eur. Rev. Med. Pharmacol. Sci.
20
,
4710
4718
PMID:
[PubMed]
140
Wu
,
C.
,
Guo
,
X.
,
Wang
,
W.
,
Wang
,
Y.
,
Shan
,
Y.
,
Zhang
,
B.
et al (
2010
)
N-Acetylgalactosaminyltransferase-14 as a potential biomarker for breast cancer by immunohistochemistry
.
BMC Cancer
10
,
123
141
Zuo
,
T.
,
Shan
,
J.
,
Liu
,
Y.
,
Xie
,
R.
,
Yu
,
X.
and
Wu
,
C.
(
2018
)
EFEMP2 mediates GALNT14-dependent breast cancer cell invasion
.
Transl. Oncol.
11
,
346
352
142
Safran
,
M.
,
Dalah
,
I.
,
Alexander
,
J.
,
Rosen
,
N.
,
Iny Stein
,
T.
,
Shmoish
,
M.
et al (
2010
)
Genecards version 3: the human gene integrator
.
Database
2010
,
baq020
16
143
Pangeni
,
R.P.
,
Channathodiyil
,
P.
,
Huen
,
D.S.
,
Eagles
,
L.W.
,
Johal
,
B.K.
,
Pasha
,
D.
et al (
2015
)
The GALNT9, BNC1 and CCDC8 genes are frequently epigenetically dysregulated in breast tumours that metastasise to the brain
.
Clin. Epigenetics
7
,
57
144
Müller
,
S.
and
Hanisch
,
F.G.
(
2002
)
Recombinant MUC1 probe authentically reflects cell-specific O-glycosylation profiles of endogenous breast cancer mucin. High density and prevalent core 2-based glycosylation
.
J. Biol. Chem.
277
,
26103
26112
145
Ashkani
,
J.
and
Naidoo
,
K.J.
(
2016
)
Glycosyltransferase gene expression profiles classify cancer types and propose prognostic subtypes
.
Sci. Rep.
6
,
1
8
146
Solatycka
,
A.
,
Owczarek
,
T.
,
Piller
,
F.
,
Piller
,
V.
,
Pula
,
B.
,
Wojciech
,
L.
et al (
2012
)
MUC1 in human and murine mammary carcinoma cells decreases the expression of core 2 β1,6-N-acetylglucosaminyltransferase and β-galactoside α2,3-sialyltransferase
.
Glycobiology
22
,
1042
1054
147
Picco
,
G.
,
Julien
,
S.
,
Brockhausen
,
I.
,
Beatson
,
R.
,
Antonopoulos
,
A.
,
Haslam
,
S.
et al (
2010
)
Over-expression of ST3Gal-I promotes mammary tumorigenesis
.
Glycobiology
20
,
1241
1250
148
Carraway
,
K.L.
,
Funes
,
M.
,
Workman
,
H.C.
and
Sweeney
,
C.
(
2007
)
Contribution of membrane mucins to tumor progression through modulation of cellular growth signaling pathways
.
Curr. Topics Dev. Biol.
78
,
1
22
149
Boutas
,
I.
,
Potiris
,
A.
,
Brenner
,
W.
,
Lebrecht
,
A.
,
Hasenburg
,
A.
,
Kalantaridou
,
S.
et al (
2019
)
The expression of galectin-3 in breast cancer and its association with chemoresistance: a systematic review of the literature
.
Arch. Gynecol. Obstetrics
300
,
1113
1120
150
Acres
,
B.
,
Apostolopoulos
,
V.
,
Balloul
,
J.-M.
,
Wreschner
,
D.
,
Xing
,
P.-X.
,
Ali-Hadji
,
D.
et al (
2000
)
MUC1-specific immune responses in human MUC1 transgenic mice immunized with various human MUC1 vaccines
.
Cancer Immunol. Immunother.
48
,
588
594
151
Apostolopoulos
,
V.
,
Pietersz
,
G.A.
,
Tsibanis
,
A.
,
Tsikkinis
,
A.
,
Drakaki
,
H.
,
Loveland
,
B.E.
et al (
2006
)
Pilot phase III immunotherapy study in early-stage breast cancer patients using oxidized mannan-MUC1 [ISRCTN71711835]
.
Breast Cancer Res
8
,
1
11
152
Vassilaros
,
S.
,
Tsibanis
,
A.
,
Tsikkinis
,
A.
,
Pietersz
,
G.A.
,
McKenzie
,
I.F.
and
Apostolopoulos
,
V.
(
2013
)
Up to 15-year clinical follow-up of a pilot phase III immunotherapy study in stage II breast cancer patients using oxidized mannan-MUC1
.
Immunotherapy
5
,
1177
1182
153
Song
,
K.
,
Herzog
,
B.H.
,
Fu
,
J.
,
Sheng
,
M.
,
Bergstrom
,
K.
,
McDaniel
,
J.M.
et al (
2015
)
Loss of core 1-derived O-glycans decreases breast cancer development in mice
.
J. Biol. Chem.
290
,
20159
20166
154
Danussi
,
C.
,
Coslovi
,
A.
,
Campa
,
C.
,
Mucignat
,
M.T.
,
Spessotto
,
P.
,
Uggeri
,
F.
et al (
2009
)
A newly generated functional antibody identifies Tn antigen as a novel determinant in the cancer cell-lymphatic endothelium interaction
.
Glycobiology
19
,
1056
1067
155
Fujita
,
R.
,
Hamano
,
H.
,
Kameda
,
Y.
,
Arai
,
R.
,
Shimizu
,
T.
,
Ota
,
M.
et al (
2019
)
Breast cancer cells expressing cancer-associated sialyl-Tn antigen have less capacity to develop osteolytic lesions in a mouse model of skeletal colonization
.
Clin. Exp. Metastasis
36
,
539
549
156
Society
,
A.C.
(
2020
)
Cancer Facts & Figures 2020
157
Gill
,
D.J.
,
Chia
,
J.
,
Senewiratne
,
J.
and
Bard
,
F.
(
2010
)
Regulation of O-glycosylation through Golgi-to-ER relocation of initiation enzymes
.
J. Cell Biol.
189
,
843
858
158
Gill
,
D.J.
,
Tham
,
K.M.
,
Chia
,
J.
,
Wang
,
S.C.
,
Steentoft
,
C.
,
Clausen
,
H.
et al (
2013
)
Initiation of GalNAc-type O-glycosylation in the endoplasmic reticulum promotes cancer cell invasiveness
.
Proc. Natl Acad. Sci. U.S.A.
110
,
E3152
E3161
159
Guo
,
J.M.
,
Zhang
,
Y.
,
Cheng
,
L.
,
Iwasaki
,
H.
,
Wang
,
H.
,
Kubota
,
T.
et al (
2002
)
Molecular cloning and characterization of a novel member of the UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase family, pp-GalNAc-T12
.
FEBS Lett.
524
,
211
218
160
Ju
,
T.
,
Aryal
,
R.P.
,
Stowell
,
C.J.
and
Cummings
,
R.D.
(
2008
)
Regulation of protein O-glycosylation by the endoplasmic reticulum-localized molecular chaperone Cosmc
.
J. Cell Biol.
182
,
531
542
161
Ju
,
T.
and
Cummings
,
R.D.
(
2002
)
A unique molecular chaperone Cosmc required for activity of the mammalian core 1 3-galactosyltransferase
.
Proc. Natl Acad. Sci. U.S.A.
99
,
16613
16618
162
Taniuchi
,
K.
,
Cerny
,
R.L.
,
Tanouchi
,
A.
,
Kohno
,
K.
,
Kotani
,
N.
,
Honke
,
K.
et al (
2011
)
Overexpression of GalNAc-transferase GalNAc-T3 promotes pancreatic cancer cell growth
.
Oncogene
30
,
4843
4854
163
Brooks
,
S.A.
,
Carter
,
T.M.
,
Bennett
,
E.P.
,
Clausen
,
H.
and
Mandel
,
U.
(
2007
)
Immunolocalisation of members of the polypeptide N-acetylgalactosaminyl transferase (ppGalNAc-T) family is consistent with biologically relevant altered cell surface glycosylation in breast cancer
.
Acta Histochem.
109
,
273
284
164
Chugh
,
S.
,
Meza
,
J.
,
Sheinin
,
Y.M.
,
Ponnusamy
,
M.P.
and
Batra
,
S.K.
(
2016
)
Loss of N-acetylgalactosaminyltransferase 3 in poorly differentiated pancreatic cancer: augmented aggressiveness and aberrant ErbB family glycosylation
.
Br. J. Cancer
114
,
1376
1386
165
Cappello
,
P.
,
Tomaino
,
B.
,
Chiarle
,
R.
,
Ceruti
,
P.
,
Novarino
,
A.
,
Castagnoli
,
C.
et al (
2009
)
An integrated humoral and cellular response is elicited in pancreatic cancer by alpha-enolase, a novel pancreatic ductal adenocarcinoma-associated antigen
.
Int. J. Cancer
125
,
639
648
166
Ortiz-Zapater
,
E.
,
Peiró
,
S.
,
Roda
,
O.
,
Corominas
,
J.M.
,
Aguilar
,
S.
,
Ampurdanés
,
C.
et al (
2007
)
Tissue plasminogen activator induces pancreatic cancer cell proliferation by a non-catalytic mechanism that requires extracellular signal-regulated kinase 1/2 activation through epidermal growth factor receptor and annexin A2
.
Am. J. Pathol.
170
,
1573
1584
167
Rauschert
,
N.
,
Brändlein
,
S.
,
Holzinger
,
E.
,
Hensel
,
F.
,
Müller-Hermelink
,
H.-K.
and
Vollmers
,
H.P.
(
2008
)
A new tumor-specific variant of GRP78 as target for antibody-based therapy
.
Lab. Invest.
88
,
375
386
168
Peng
,
L.
,
Liang
,
J.
,
Wang
,
H.
,
Song
,
X.
,
Rashid
,
A.
,
Gomez
,
H.F.
et al (
2010
)
High levels of nucleolar expression of nucleolin are associated with better prognosis in patients with stage II pancreatic ductal adenocarcinoma
.
Clin. Cancer Res.
16
,
3734
3742
169
Hajjar
,
K.A.
,
Guevara
,
C.A.
,
Lev
,
E.
,
Dowling
,
K.
and
Chacko
,
J.
(
1996
)
Interaction of the fibrinolytic receptor, annexin II, with the endothelial cell surface. Essential role of endonexin repeat 2
.
J. Biol. Chem.
271
,
21652
21659
170
Hsiao
,
K.C.
,
Shih
,
N.-Y.
,
Fang
,
H.-L.
,
Huang
,
T.-S.
,
Kuo
,
C.-C.
,
Chu
,
P.-Y.
et al (
2013
)
Surface alpha-enolase promotes extracellular matrix degradation and tumor metastasis and represents a new therapeutic target
.
PLoS ONE
8
,
e69354
171
Miao
,
Y.R.
,
Eckhardt
,
B.L.
,
Cao
,
Y.
,
Pasqualini
,
R.
,
Argani
,
P.
,
Arap
,
W.
et al (
2013
)
Inhibition of established micrometastases by targeted drug delivery via cell surface-associated GRP78
.
Clin. Cancer Res.
19
,
2107
2116
172
Myrvang
,
H.K.
,
Guo
,
X.
,
Li
,
C.
and
Dekker
,
L.V.
(
2013
)
Protein interactions between surface annexin A2 and S100A10 mediate adhesion of breast cancer cells to microvascular endothelial cells
.
FEBS Lett.
587
,
3210
3215
173
Herlyn
,
M.
,
Sears
,
H.F.
,
Steplewski
,
Z.
and
Koprowski
,
H.
(
1982
)
Monoclonal antibody detection of a circulating tumor-associated antigen. I. Presence of antigen in sera of patients with colorectal, gastric, and pancreatic carcinoma
.
J. Clin. Immunol.
2
,
135
140
174
Magnani
,
J.L.
,
Brockhaus
,
M.
,
Smith
,
D.
,
Ginsburg
,
V.
,
Blaszczyk
,
M.
,
Mitchell
,
K.
et al (
1981
)
A monosialoganglioside is a monoclonal antibody-defined antigen of colon carcinoma
.
Science (New York, N.Y.)
212
,
55
56
175
Magnani
,
J.L.
,
Nilsson
,
B.
,
Brockhaus
,
M.
,
Zopf
,
D.
,
Steplewski
,
Z.
,
Koprowski
,
H.
et al (
1982
)
A monoclonal antibody-defined antigen associated with gastrointestinal cancer is a ganglioside containing sialylated lacto-N-fucopentaose II
.
J. Biol. Chem.
257
,
14365
14369
PMID:
[PubMed]
176
Lahdenne
,
P.
,
Pitkanen
,
S.
,
Rajantie
,
J.
,
Kuusela
,
P.
,
Shmes
,
M.A.
,
Lanning
,
M.
et al (
1995
)
Tumor markers CA 125 and CA 19-9 in cord blood and during infancy: developmental changes and use in pediatric germ cell tumors
.
Pediatr. Res.
38
,
797
801
177
Goonetilleke
,
K.S.
and
Siriwardena
,
A.K.
(
2007
)
Systematic review of carbohydrate antigen (CA 19-9) as a biochemical marker in the diagnosis of pancreatic cancer
.
Eur. J. Surg. Oncol.
33
,
266
270
178
Kalthoff
,
H.
,
Kreiker
,
C.
,
Schmiegel
,
W.H.
,
Greten
,
H.
and
Thiele
,
H.G.
(
1986
)
Characterization of CA 19-9 bearing mucins as physiological exocrine pancreatic secretion products
.
Cancer Res.
46
,
3605
3607
PMID:
[PubMed]
179
Tempero
,
M.A.
,
Uchida
,
E.
,
Takasaki
,
H.
,
Burnett
,
D.A.
,
Steplewski
,
Z.
and
Pour
,
P.M.
(
1987
)
Relationship of carbohydrate antigen 19-9 and Lewis antigens in pancreatic cancer
.
Cancer Res.
47
,
5501
5503
PMID:
[PubMed]
180
Pour
,
P.M.
,
Tempero
,
M.M.
,
Takasaki
,
H.
,
Uchida
,
E.
,
Takiyama
,
Y.
,
Burnett
,
D.A.
et al (
1988
)
Expression of blood group-related antigens ABH, Lewis A, Lewis B, Lewis X, Lewis Y, and CA 19-9 in pancreatic cancer cells in comparison with the patient's blood group type
.
Cancer Res.
48
,
5422
5426
PMID:
[PubMed]
181
Agrawal
,
B.
,
Krantz
,
M.J.
,
Parker
,
J.
and
Longenecker
,
B.M.
(
1998
)
Expression of MUC1 mucin on activated human T cells: implications for a role of MUC1 in normal immune regulation
.
Cancer Res.
58
,
4079
4081
PMID:
[PubMed]
182
Gendler
,
S.J.
and
Spicer
,
A.P.
(
1995
)
Epithelial mucin genes
.
Annu. Rev. Physiol.
57
,
607
634
183
Wykes
,
M.
,
MacDonald
,
K.P.
,
Tran
,
M.
,
Quin
,
R.J.
,
Xing
,
P.X.
,
Gendler
,
S.J.
et al (
2002
)
MUC1 epithelial mucin (CD227) is expressed by activated dendritic cells
.
J. Leuk. Biol.
72
,
692
701
PMID:
[PubMed]
184
Hayes
,
D.F.
,
Silberstein
,
D.S.
,
Rodrique
,
S.W.
and
Kufe
,
D.W.
(
1990
)
DF3 antigen, a human epithelial cell mucin, inhibits adhesion of eosinophils to antibody-coated targets
.
J. Immunol.
145
,
962
970
PMID:
[PubMed]
185
Zhang
,
K.
,
Sikut
,
R.
and
Hansson
,
G.C.
(
1997
)
A MUC1 mucin secreted from a colon carcinoma cell line inhibits target cell lysis by natural killer cells
.
Cell. Immunol.
176
,
158
165
186
Jentoft
,
N.
(
1990
)
Why are proteins O-glycosylated?
Trends Biochem. Sci.
15
,
291
294
187
Rughetti
,
A.
,
Turchi
,
V.
,
Ghetti
,
C.A.
,
Scambia
,
G.
,
Panici
,
P.B.
,
Roncucci
,
G.
et al (
1993
)
Human B-cell immune response to the polymorphic epithelial mucin
.
Cancer Res.
53
,
2457
2459
PMID:
[PubMed]
188
von Mensdorff-Pouilly
,
S.
,
Petrakou
,
E.
,
Kenemans
,
P.
,
van Uffelen
,
K.
,
Verstraeten
,
A.A.
,
Snijdewint
,
F.G.M.
et al (
2000
)
Reactivity of natural and induced human antibodies to MUC1 mucin with MUC1 peptides and n-acetylgalactosamine (GalNAc) peptides
.
Int. J. Cancer
86
,
702
712
189
von Mensdorff-Pouilly
,
S.
,
Verstraeten
,
A.A.
,
Kenemans
,
P.
,
Snijdewint
,
F.G.M.
,
Kok
,
A.
,
Van Kamp
,
G.J.
et al (
2000
)
Survival in early breast cancer patients is favorably influenced by a natural humoral immune response to polymorphic epithelial mucin
.
J. Clin. Oncol.
18
,
574
583
190
Remmers
,
N.
,
Anderson
,
J.M.
,
Linde
,
E.M.
,
DiMaio
,
D.J.
,
Lazenby
,
A.J.
,
Wandall
,
H.H.
et al (
2013
)
Aberrant expression of mucin core proteins and o-linked glycans associated with progression of pancreatic cancer
.
Clin Cancer Res
19
,
1981
1993
191
Giorgadze
,
T.A.
,
Peterman
,
H.
,
Baloch
,
Z.W.
,
Furth
,
E.E.
,
Pasha
,
T.
,
Shiina
,
N.
et al (
2006
)
Diagnostic utility of mucin profile in fine-needle aspiration specimens of the pancreas: an immunohistochemical study with surgical pathology correlation
.
Cancer
108
,
186
197
192
Ho
,
J.J.
and
Kim
,
Y.S.
(
1994
)
Serological pancreatic tumor markers and the MUC1 apomucin
.
Pancreas
9
,
674
691
193
Kim
,
G.E.
,
Bae
,
H.
,
Park
,
H.
,
Kuan
,
S.
,
Crawley
,
S.C.
,
Ho
,
J.J.L.
et al (
2002
)
Aberrant expression of MUC5AC and MUC6 gastric mucins and sialyl Tn antigen in intraepithelial neoplasms of the pancreas
.
Gastroenterology
123
,
1052
1060
194
Lan
,
M.S.
,
Finn
,
O.J.
,
Fernsten
,
P.D.
and
Metzgar
,
R.S.
(
1985
)
Isolation and properties of a human pancreatic adenocarcinoma-associated antigen, DU-PAN-2
.
Cancer Res.
45
,
305
310
PMID:
[PubMed]
195
Nakajima
,
K.
,
Ota
,
H.
,
Zhang
,
M.X.
,
Sano
,
K.
,
Honda
,
T.
,
Ishii
,
K.
et al (
2003
)
Expression of gastric gland mucous cell-type mucin in normal and neoplastic human tissues
.
J. Histochem. Cytochem.
51
,
1689
1698
196
Schuessler
,
M.H.
,
Pintado
,
S.
,
Welt
,
S.
,
Real
,
F.X.
,
Xu
,
M.
,
Melamed
,
M.R.
et al (
1991
)
Blood group and blood-group-related antigens in normal pancreas and pancreas cancer: enhanced expression of precursor type 1, Tn and sialyl-Tn in pancreas cancer
.
Int. J. Cancer
47
,
180
187
197
Yue
,
T.
,
Goldstein
,
I.J.
,
Hollingsworth
,
M.A.
,
Kaul
,
K.
,
Brand
,
R.E.
and
Haab
,
B.B.
(
2009
)
The prevalence and nature of glycan alterations on specific proteins in pancreatic cancer patients revealed using antibody-lectin sandwich arrays
.
Mol. Cell. Proteomics
8
,
1697
1707
198
Chen
,
S.
,
LaRoche
,
T.
,
Hamelinck
,
D.
,
Bergsma
,
D.
,
Brenner
,
D.
,
Simeone
,
D.
et al (
2007
)
Multiplexed analysis of glycan variation on native proteins captured by antibody microarrays
.
Nat. Methods
4
,
437
444
199
Chugh
,
S.
,
Barkeer
,
S.
,
Rachagani
,
S.
,
Nimmakayala
,
R.K.
,
Perumal
,
N.
,
Pothuraju
,
R.
et al (
2018
)
Disruption of C1galt1 gene promotes development and metastasis of pancreatic adenocarcinomas in mice
.
Gastroenterology
155
,
1608
1624
200
Dube
,
D.H.
and
Bertozzi
,
C.R.
(
2005
)
Glycans in cancer and inflammation–potential for therapeutics and diagnostics
.
Nat. Rev. Drug Discov.
4
,
477
488
201
Ferguson
,
K.
,
Yadav
,
A.
,
Morey
,
S.
,
Abdullah
,
J.
,
Hrysenko
,
G.
,
Eng
,
J.Y.
et al (
2014
)
Preclinical studies with JAA-F11 anti-Thomsen-Friedenreich monoclonal antibody for human breast cancer
.
Future Oncol.
10
,
385
399
202
Miles
,
D.
,
Roché
,
H.
,
Martin
,
M.
,
Perren
,
T.J.
,
Cameron
,
D.A.
,
Glaspy
,
J.
et al (
2011
)
Phase III multicenter clinical trial of the sialyl-TN (STn)-keyhole limpet hemocyanin (KLH) vaccine for metastatic breast cancer
.
Oncologist
16
,
1092
1100
203
Hutchins
,
L.
,
Makhoul
,
I.
,
Emanuel
,
P.D.
,
Siegel
,
E.R.
,
Jousheghany
,
F.
,
Monzavi-Karbassi
,
B.
et al (
2014
)
Abstract CT202: a Phase I study of a first-in-man carbohydrate mimetic-peptide vaccine in Stage IV breast cancer subjects
.
Cancer Res.
8
,
CT202
204
Blidner
,
A.G.
,
Mariño
,
K.V.
and
Rabinovich
,
G.A.
(
2016
)
Driving CARs into sweet roads: targeting glycosylated antigens in cancer
.
Immunity
44
,
1248
1250
205
Zhou
,
R.
,
Yazdanifar
,
M.
,
Roy
,
L.D.
,
Whilding
,
L.M.
,
Gavrill
,
A.
,
Maher
,
J.
et al (
2019
)
CAR t cells targeting the tumor MUC1 glycoprotein reduce triple-negative breast cancer growth
.
Front. Immunol.
10
,
1
12
206
Roy
,
L.D.
,
Dillon
,
L.M.
,
Zhou
,
R.
,
Moore
,
L.J.
,
Livasy
,
C.
,
El-Khoury
,
J.M.
et al (
2017
)
A tumor specific antibody to aid breast cancer screening in women with dense breast tissue
.
Genes Cancer
8
,
536
549
207
Tarp
,
M.A.
and
Clausen
,
H.
(
2008
)
Mucin-type O-glycosylation and its potential use in drug and vaccine development
.
Biochim. Biophys. Acta
1780
,
546
563
208
Adluri
,
S.
,
Gilewski
,
T.
,
Zhang
,
S.
,
Ramnath
,
V.
,
Ragupathi
,
G.
and
Livingston
,
P.
(
1999
)
Specificity analysis of sera from breast cancer patients vaccinated with MUC1-KLH plus QS-21
.
Br. J. Cancer
79
,
1806
1812
209
Ding
,
L.
,
Lalani
,
E.-N.
,
Reddish
,
M.
,
Koganty
,
R.
,
Wong
,
T.
,
Samuel
,
J.
et al (
1993
)
Immunogenicity of synthetic peptides related to the core peptide sequence encoded by the human MUC1 mucin gene: effect of immunization on the growth of murine mammary adenocarcinoma cells transfected with the human MUC1 gene
.
Cancer Immunol. Immunother.
36
,
9
17
210
Gilewski
,
T.
,
Adluri
,
S.
,
Ragupathi
,
G.
,
Zhang
,
S.
,
Yao
,
T.J.
,
Panageas
,
K.
et al (
2000
)
Vaccination of high-risk breast cancer patients with mucin-1 (MUC1) keyhole limpet hemocyanin conjugate plus QS-21
.
Clin. Cancer Res.
6
,
1693
1701
PMID:
[PubMed]
211
Goydos
,
J.S.
,
Elder
,
E.
,
Whiteside
,
T.L.
,
Finn
,
O.J.
and
Lotze
,
M.T.
(
1996
)
A phase I trial of a synthetic mucin peptide vaccine. induction of specific immune reactivity in patients with adenocarcinoma
.
J. Surg. Res.
63
,
298
304
212
Palmer
,
M.
,
Parker
,
J.
,
Modi
,
S.
,
Butts
,
C.
,
Smylie
,
M.
,
Meikle
,
A.
et al (
2001
)
Phase I study of the BLP25 (MUC1 peptide) liposomal vaccine for active specific immunotherapy in stage IIIB/IV non-small-cell lung cancer
.
Clin. Lung Cancer
3
,
49
57
213
Ramanathan
,
R.K.
,
Lee
,
K.M.
,
McKolanis
,
J.
,
Hitbold
,
E.
,
Schraut
,
W.
,
Moser
,
A.J.
et al (
2005
)
Phase I study of a MUC1 vaccine composed of different doses of MUC1 peptide with SB-AS2 adjuvant in resected and locally advanced pancreatic cancer
.
Cancer Immunol. Immunother.
54
,
254
264
214
Soares
,
M.M.
,
Mehta
,
V.
and
Finn
,
O.J.
(
2001
)
Three different vaccines based on the 140-amino acid MUC1 peptide with seven tandemly repeated tumor-specific epitopes elicit distinct immune effector mechanisms in wild-type versus MUC1-transgenic mice with different potential for tumor rejection
.
J. Immunol.
166
,
6555
6563
215
Zhang
,
S.
,
Graeber
,
L.A.
,
Helling
,
F.
,
Ragupathi
,
G.
,
Adluri
,
S.
,
Lloyd
,
K.O.
et al (
1996
)
Augmenting the immunogenicity of synthetic MUC1 peptide vaccines in mice
.
Cancer Res.
56
,
3315
3319
PMID:
[PubMed]
216
Sharon
,
N.
and
Lis
,
H.
(
2004
)
History of lectins: from hemagglutinins to biological recognition molecules
.
Glycobiology
14
,
53r
62r
217
Shimomura
,
O.
,
Oda
,
T.
,
Tateno
,
H.
,
Ozawa
,
Y.
,
Kimura
,
S.
,
Sakashita
,
S.
et al (
2018
)
A novel therapeutic strategy for pancreatic cancer: targeting cell surface glycan using rBC2LC-N lectin-drug conjugate (LDC)
.
Mol. Cancer Ther.
17
,
183
195

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