Loss of function of the PTEN tumour suppressor, resulting in dysregulated activation of the phosphoinositide 3-kinase (PI3K) signalling network, is recognized as one of the most common driving events in prostate cancer development. The observed mechanisms of PTEN loss are diverse, but both homozygous and heterozygous genomic deletions including PTEN are frequent, and often accompanied by loss of detectable protein as assessed by immunohistochemistry (IHC). The occurrence of PTEN loss is highest in aggressive metastatic disease and this has driven the development of PTEN as a prognostic biomarker, either alone or in combination with other factors, to distinguish indolent tumours from those likely to progress. Here, we discuss these factors and the consequences of PTEN loss, in the context of its role as a lipid phosphatase, as well as current efforts to use available inhibitors of specific components of the PI3K/PTEN/TOR signalling network in prostate cancer treatment.

THE PI3K/PTEN SIGNALLING NETWORK

Elevated and/or uncontrolled activation of the signalling networks activated by growth factors, in particular signalling through the phosphoinositide 3-kinase (PI3K) group of lipid kinases, is a characteristic of most cancers including prostate cancer [1,2]. The signalling network (Figure 1) is named after a group of lipid kinases, the class I PI3Ks that are tightly regulated, with low basal activity and that are activated by diverse cell surface receptors. These activating receptors include those for many growth factors, cytokines and chemokines, as well as extracellular matrix components acting via integrins [3]. Class I PI3Ks are heterodimeric enzymes, with four human genes encoding catalytic isoforms and five encoding regulatory subunits. Although examples of both catalytic (PIK3CA encoding the α catalytic subunit of PI3K) and regulatory (PIK3R1 and PIK3R2 encoded) subunits have been found to be frequently mutated in several forms of cancer [4,5], rates of mutation and copy number changes in genes encoding PI3K itself are generally lower in prostate cancer than in many other common carcinomas [1,6]. As part of their activation mechanism, the PI3K catalytic subunits, which are all of approximately 110 kDa, directly bind to small GTPases, which appear to be members of the RAS sub-family in the case of the p110α, p110γ and p110δ PI3K isoforms, but members of the RAC GTPase sub-family in the case of p110β [3,7]. When activated at the plasma membrane, the PI3Ks phosphorylate the relatively abundant phosphoinositide lipid, phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] on the available 3-position hydroxy group, to form small amounts of the signalling lipid phosphatidylinositol 3,4,5-trisphosphate [(PIP3)]. The role of PTEN in the pathway is to catalyse the opposing reaction, metabolizing PIP3 into PI(4,5)P2 as shown in Figure 1(A).

PI3K/PTEN pathway signalling

Figure 1
PI3K/PTEN pathway signalling

(A) The reactions catalysed by the phosphoinositide lipid kinase PI3K that is antagonized by the lipid phosphatase PTEN. (B) A hypothetical model for the working of the PI3K signalling network is represented. Lipid kinases are represented by light orange ovals; lipid phosphatases are represented by dark orange and protein kinases are shaded grey. Phosphoinositide lipids are also labelled. Orange reaction arrows indicate conversion of lipid species, and black arrows represent functional interactions. PIP3 effectors are also included representing the large PIP3-binding proteome.

Figure 1
PI3K/PTEN pathway signalling

(A) The reactions catalysed by the phosphoinositide lipid kinase PI3K that is antagonized by the lipid phosphatase PTEN. (B) A hypothetical model for the working of the PI3K signalling network is represented. Lipid kinases are represented by light orange ovals; lipid phosphatases are represented by dark orange and protein kinases are shaded grey. Phosphoinositide lipids are also labelled. Orange reaction arrows indicate conversion of lipid species, and black arrows represent functional interactions. PIP3 effectors are also included representing the large PIP3-binding proteome.

Does signalling through the β isoform of PI3K selectively drive prostate tumorigenesis?

In 2008, genetic analysis of the PI3K isoform dependence of prostate tumour formation in mice lacking PTEN function showed that deletion of Pik3ca had little effect on tumour formation, yet deletion of Pik3cb dramatically reduced tumour burden [8]. Furthermore, similar conclusions were drawn from work with prostate [9] and breast cancer cell lines [10] although a mechanistic basis for this selective link has yet to be identified. This over-reliance on signalling through PI3K β in cases of PTEN loss may partly explain the low occurrence of mutations and copy number changes in PIK3CA in prostate cancer and, although PIK3CB, the gene encoding the β catalytic subunit of PI3K, is very rarely found to be activated by mutation, rates of PIK3CB gene amplification are significant in metastatic prostate cancer (approximately 5%) and particularly high in neuroendocrine prostate cancer (21%). This has influenced some efforts to therapeutically target PI3K/PTEN/TOR signalling in the area of prostate cancer, motivated by the potential to selectively target the β isoform of PI3K and therefore perhaps has lower drug toxicity with similar efficacy compared with inhibitors of all four PI3K isoforms. On the other hand, the links between loss of PTEN, PIP3 generated by the β isoform of PI3K and tumorigenesis seem inconsistent [11,12]. Additionally, more recently data have been presented showing that when one isoform of PI3K is inhibited, feedback loops can lead to increased activation of other expressed isoforms [13,14]. Regardless, the real value of these ideas and the drug programmes they have motivated should soon be clear, as drugs specifically targeting PI3K β have entered clinical prostate cancer trials (GSK2636771 and AZD8186 that inhibit both PI3K β and δ).

Signalling downstream of PI3K/PTEN

The significance in cellular transformation of signalling through PI3K is also highlighted by the very frequent identification in tumours of genetic changes in upstream signalling components that lead to PI3K activation. The clearest examples of such upstream PI3K activating oncogenes are the RAS GTPases and several receptor tyrosine kinases (RTKs), including the epidermal growth factor receptor family (EGFR, HER2/ERBB2/NEU etc.) and the PDGF and KIT receptors. However, the list of PI3K network components that appear to be oncogenic drivers extends further to include less central components such as the E3 ubiquitin ligase CBL, which promotes RTK degradation and INPP4B that metabolizes the secondary PI3K product lipid phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2] [2]. As with other cancers, integrated genomic studies of primary and metastatic prostate cancers have consistently identified changes leading to the aberrant activation of PI3K signalling in many of these tumours [1,1517].

The PI3K product lipid, PIP3, promotes cell growth, proliferation, cellular polarization and other changes through a large and diverse group of downstream effector proteins endowed with a lipid binding domain capable of selectively binding to it. It is unclear how broad this PIP3-binding proteome is in humans, with estimates ranging from a few tens to over 100 [1820] but the best understood examples by far are the AKT protein kinases, important oncogenes in their own right. Strong genetic experiments in mice, flies and worms have demonstrated the importance of the AKT kinases in mediating the effects of PI3K activation on cell growth and proliferation [2125]. Additionally, the identification of numerous confirmed substrates for AKT has provided insight into the molecular mechanisms by which these effects are mediated [25,26]. Downstream of PI3K and AKT, a major regulator of cell growth that has been repeatedly implicated in tumorigenesis is mechanistic target of rapamycin (MTOR). MTOR is a protein kinase subject to multiple complex regulatory inputs in addition to activation downstream of AKT (e.g. nutrients and energy) and plays a key role in regulating cell growth and anabolic metabolism, as well as being involved in AKT activation [27].

On the other hand, the significance of the other regulatory mechanisms downstream of PI3K independent of AKT and MTOR remains largely unclear, particularly in cancer. Notably, gradients of PIP3 have been identified in the plasma membrane of several cell types. Particular attention has been paid to the dynamic enrichment of PIP3 seen in the leading edge of axonal growth cones, of mammalian neutrophils and fibroblasts and the slime mould Dictyostelium discoideum during directed cell migration. More relevant to the prostate, a stable enrichment of PIP3 has been seen in the basolateral membranes of some polarized epithelial cells [2832].

The significance of the disturbance of such localized and/or AKT-independent PI3K signalling in prostate, or other, cancers is a key remaining question. Many lines of evidence point to such important AKT-independent oncogenic mechanisms, both through the identification of alternative mechanisms [3335] and also the characterization of catalytically active mutants of PTEN found in human tumours that retain the ability to suppress AKT activity yet fail in other cell-based assays [36,37]. There are also numerous reports of discordance between the consequences of AKT activation and either activation of PI3K or loss of PTEN (e.g. [34,36,38,39]).

Given the significance in oncogenesis of components that activate signalling through the PI3K network, attention has also fallen on the balancing inhibitory components that act to suppress PI3K signalling. The clearest examples of these inhibitory components are the lipid phosphatases that metabolize the growth promoting signals synthesized by the PI3Ks. SHIP and SHIP2 are phosphatidylinositol 5-phosphatases (PI5Ps) that convert PIP3 into the secondary PI3K lipid product PI(3,4)P2. However, the evidence that the SHIPs represent bona fide tumour suppressors is limited, perhaps due to the existence of redundancy between these and other related enzymes, perhaps because PI(3,4)P2 also activates downstream PI3K effectors including AKT [19,40]. Related to this point, the phosphatidylinositol 4-phosphate (PI4P) encoded by INPP4B, which converts PI(3,4)P2 to phosphatidylinositol 3-phosphate (PI3P), has been shown to act as a tumour suppressor in several tissues by removing PI(3,4)P2 and suppressing AKT activity, yet also plays conflicting oncogenic roles in some tumours including melanomas, colon cancers and leukaemias possibly by promoting PI3P-dependent activation of SGK3 [41,42]. These results highlight the contrast with the best studied phosphoinositide phosphatase however, PTEN, which acts as a PIP3 3-phosphatase and has consistently been shown to act as a significant tumour suppressor in many organ systems, particularly the prostate.

Notably, multiple genetic changes leading to the activation of the broad PI3K pathway within individual prostate tumours are commonly observed. For example, there seems to be a significant association between PTEN loss and PIK3CA mutation or amplification in prostate adenocarcinoma tumour sets (www.cbioportal.org), with both changes being commonly identified in individual tumours. This is in contrast with the frequently observed mutual exclusivity of different mutational events within other specific functional networks that have been observed in previous studies [43,44].

PTEN: A HAPLOINSUFFICIENT TUMOUR SUPPRESSOR FUNCTIONALLY OPPOSING PI3K

In 1995, Gray et al. [45] showed that loss of region q23–24 on chromosome 10 was a frequent occurrence in prostate cancer (62% of tumours studied) contributing to a body of data showing loss of this region in a number of other tumours [4648]. In 1997, two groups isolated Phosphatase and Tensin homologue deleted on chromosome 10 (PTEN–also referred to as MMAC1 and TEP1) as the tumour suppressor gene on Chr10, identifying coding mutations in this gene in samples from prostate cancer patients as well as glioblastoma, breast and kidney cancer derived samples [49,50]. Steck et al. [50] screened chromosome fragments for their ability to suppress tumorigenic phenotypes and were subsequently able to clone PTEN, whereas Li et al. [49] focused on identifying PTEN mutations in cancer cell lines and tumours. This tumour suppressor status was further confirmed by the identification of PTEN mutations in patients suffering from the familial cancer-syndromes Cowden disease and Bannayan–Riley–Ruvalcaba syndrome [51,52], although notably, prostate cancers have rarely been described in sufferers of these syndromes [53], which are now often considered together under the umbrella term PTEN hamartoma tumour syndrome (PHTS).

Both groups that identified PTEN commented on its homology to the family of protein tyrosine phosphatases [49,50], and further publications showed that PTEN had weak dual specificity protein tyrosine and serine/threonine phosphatase activity, with a preference for highly acidic substrates [54,55]. However, it was demonstrated soon after that PTEN dephosphorylates the 3-position on the inositol ring of the PI3K product lipid, PIP3 [56] to regenerate PI(4,5)P2. This reaction is illustrated in Figure 1(A). Recombinant PTEN expressed in Escherichia coli also dephosphorylates the 3-position on the inositol ring of the related substrates, inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4] (which represents the soluble headgroup of PIP3) and PI3P and PI(3,4)P2, but at reduced rate [56,57]. Significantly, strong evidence that it is the lipid phosphatase activity that is critical for the tumour suppressor functions of PTEN was provided by the demonstration that a missense mutation, PTEN G129E, identified in two families suffering from Cowden disease, retains protein phosphatase activity but has greatly reduced lipid phosphatase activity towards PIP3 and was unable to suppress AKT phosphorylation or cell growth in culture [57,58]. Intense research since these early studies of PTEN has revealed many details regarding how it fulfils its roles in regulating PI3K signalling and blocking tumorigenesis in many tissues (see reviews e.g. [59,60]). However, major questions remain about the downstream mechanisms by which elevated and mislocalized PIP3 increases the chances of tumour formation (as described above) and also whether PTEN has additional unrelated functions, such as dephosphorylating protein substrates or non-catalytic functions. On this point, the consistent finding that heterozygous mice expressing the stable PTEN G129E mutant develop a worse spectrum of tumours than null allele heterozygous mice, implies that if PTEN fulfils such PIP3-independent functions, these additional functions have little effect on their own to suppress tumours in most tissues [61,62].

In terms of cell biology, PTEN is a relatively small 50 kDa enzyme, which associates transiently with the plasma membrane to metabolize its lipid substrate [29,59,63]. Additional functions and sites of action for PTEN, such as in the nucleus and on endomembranes, have been proposed but these remain controversial and detailed mechanisms remain to be determined [59,60,64,65]. PTEN binds to many other proteins, several through its extreme C-terminal PDZ binding sequence and it is this binding mode that seems responsible for the localization of PTEN to adherens junctions in epithelial cells and to neuronal synapses [29,6669]. The apical junctional localization of PTEN in several epithelial tissues has been described, including in the prostate although in most cases this localization appears as an enrichment, rather than a bold unique localization (described later) [67,68,70,71].

It seems significant and in contrast with some other tumour suppressors that the potential impact of even small changes in PTEN expression appears large, given the evidence from clinical data and murine models that PTEN is a haploinsufficient tumour suppressor, with function being strongly dose dependent. Mice with only a single functional Pten copy throughout the body develop tumours in a diverse range of organs [72,73]. Furthermore, elegant studies using a hypomorphic allele, which generates approximately a half dose of normal PTEN protein relative to a wild-type allele, have found that heterozygous mice carrying either a single copy of wild-type PTEN or one hypomorphic allele show prostate cancer initiation and progression that correlates closely with reducing PTEN dose [74] and even animals carrying one wild-type and one hypomorphic copy show increased rates of tumour formation in some organs, particularly the breast [75]. Conversely, overexpression of PTEN in mice leads to a tumour resistant state [76,77].

PROSTATE CANCER AND PTEN

Prostate cancer is the second most common cancer in the U.K. (Cancer Research UK, 2013), with approximately 50000 new cases diagnosed in 2013 and approximately 10000 deaths in 2012, making it the second most common cause of death from cancer in men. Age is the most significant risk factor for prostate cancer, with >50% of the cases diagnosed between 2011 and 2013 in men >70 years of age, although family history is also a risk factor [78]. Treatment of prostate cancer is challenging, because histologically similar tumours give rise to diverse clinical outcomes. At this time, there are no reliable prognostic markers to discriminate indolent tumours from those likely to cause aggressive metastatic disease, and this complicates treatment decisions. Genetically, prostate tumours show inter- and intra-tumoural heterogeneity, suggesting multiple genetic changes and environmental factors are involved. Along with surgery and radiotherapy, androgen deprivation therapy is a very common treatment for metastatic prostate cancer, but almost all such cancers eventually become resistant to this treatment and their disease will progress, at this stage being termed as castrate-resistant prostate cancer (CRPC).

Approximately half of primary prostate cancers carry driving gene fusions between androgen regulated promoters and members of the E26 transformation specific (ETS) family of transcription factors, most commonly the TMPRSS2–ERG fusion. However, primary tumours are otherwise genetically very diverse [79]. Metastatic tumours show more recurrent changes, with four dominant events each being present in approximately half of these tumours: (1) amplifications of the androgen receptor (AR) gene; (2) ETS family gene fusions, again most commonly the TMPRSS2–ERG fusion; (3) disruption of the TP53 gene and (4) as will be discussed here, disruption of PTEN [17]. The significance to pathology of these changes in PTEN has been confirmed in animal studies, with full genetic deletion of PTEN specifically from the developed prostate gland causing rapid high grade prostate intraepithelial neoplasia (PIN) and in some studies an invasive prostate carcinoma within 3–6 months of age [74,80].

PTEN MUTATIONS IN PROSTATE CANCER

Recent detailed molecular analyses using exome and genome sequencing, array comparative genomic hybridization (aCGH), in situ hybridization and immunohistochemistry (IHC) have confirmed early observations that PTEN function is frequently lost in prostate cancer. These studies found copy number alterations, structural rearrangements and/or point mutations to the PTEN gene in between 16% and 41% of tumour samples [1,16,17,79,8183]. The difference in mutation frequency is likely to reflect, at least in part, the stage of cancers analysed–studies looking at CRPC showed higher levels of mutation, with homozygous loss of PTEN being the most common alteration [16,17]. PTEN appears more frequently subject to deletion than point mutation in prostate cancer, and in all studies point mutations (nonsense, missense or insertion/deletion changes) were in the minority. For example, detailed genetic analyses of >300 primary prostate tumours, found 2.4% had missense or nonsense mutations, compared with 15% with copy number alterations [79]. Similarly, consultation of the TCGA Research Network showed an overall alteration rate of 20.6% for PTEN from nine studies, with approximately three quarters of these changes representing PTEN deletions. These data are summarized in Figures 2(A) and 2(B). In other studies, point mutations were found only combined with heterozygous gene loss [16,17]. One reason why copy number alteration may be more common is that loss of PTEN can occur through a series of ‘shuffling’ events dubbed chromoplexy, where multiple distant loci undergo concurrent rearrangement [15,81,84]. This is in keeping with the emerging theme that relative to other cancer types, prostate cancer is driven more by large-scale genomic structural rearrangements than by point mutations [84,85]. Baca et al. [81] proposed that PTEN mutations may be a ‘gating’ point for the development of aggressive prostate cancer, based on the subclonal nature of PTEN loss in their tumour set. However, data such as the detection of shared PTEN alterations in multifocal prostate cancer [86] support a role for PTEN loss in prostate cancer initiation, at least in some cases (see below).

Classes and locations of PTEN alterations in prostate cancer

Figure 2
Classes and locations of PTEN alterations in prostate cancer

(A) PTEN is primarily altered by deletion in prostate cancer. The data used to generate this figure are derived from the TCGA Research Network (http://cancergenome.nih.gov/). Nine prostate cancer studies were selected, and the total number of PTEN mutations was pooled (279 mutations, from 1355 samples, giving a PTEN alteration rate of 20.6%). These 279 alterations were classified into deletion, mutation, multiple alteration and amplification. (B) The site of PTEN mutations mapped on to the PTEN domain structure. The data used to generate this figure are derived from the TCGA Research Network (http://cancergenome.nih.gov) and COSMIC (cancer.sanger.ac.uk) [166]. Mutations are mapped on to the primary structure of PTEN, and classified according to whether they are truncating (including nonsense and frameshift mutations), missense or other (e.g. in frame deletion). In several cases, multiple mutations are present at a single amino acid in different patient samples, and this is depicted by the height of the bars.

Figure 2
Classes and locations of PTEN alterations in prostate cancer

(A) PTEN is primarily altered by deletion in prostate cancer. The data used to generate this figure are derived from the TCGA Research Network (http://cancergenome.nih.gov/). Nine prostate cancer studies were selected, and the total number of PTEN mutations was pooled (279 mutations, from 1355 samples, giving a PTEN alteration rate of 20.6%). These 279 alterations were classified into deletion, mutation, multiple alteration and amplification. (B) The site of PTEN mutations mapped on to the PTEN domain structure. The data used to generate this figure are derived from the TCGA Research Network (http://cancergenome.nih.gov) and COSMIC (cancer.sanger.ac.uk) [166]. Mutations are mapped on to the primary structure of PTEN, and classified according to whether they are truncating (including nonsense and frameshift mutations), missense or other (e.g. in frame deletion). In several cases, multiple mutations are present at a single amino acid in different patient samples, and this is depicted by the height of the bars.

DETECTING PTEN CHANGES IN PROSTATE CANCER AND ASSOCIATION WITH DISEASE SEVERITY

In a clinical setting, fluorescence in situ hybridization (FISH) and IHC are commonly used to assess patient samples for changes in the abundance of PTEN mRNA and protein respectively. Substantial effort has been expended to optimize IHC methods in particular in light of evidence that PTEN expression is regulated post-transcriptionally [87].

Fluorescence in situ hybridization

Estimates of PTEN gene loss in prostate cancer by FISH are quite variable, and likely reflect differences in sample cohorts, intra-tumoural heterogeneity, methodology and analyses. For example, two studies using the same FISH probes but different sample sets found loss of PTEN in 68% and 44% of primary prostate carcinomas [88,89]. More recent four colour FISH protocols have been developed–now incorporating probes for regions flanking the PTEN locus as well as for the centromere of ch10 and for PTEN [9092]. This provides information about the size of Ch10 deletions and allows the identification of false positive results due to sectioning artefacts. In an initial study of 330 samples, almost all from patients who had undergone radical prostatectomies, 40% showed PTEN loss by FISH [92]. This number was in good agreement with Choucair et al. [93] who showed that 41% of primary tumours had heterozygous loss of PTEN and that this was associated with a reduced time to recurrence and decreased AR signalling. Studies of more advanced disease samples have found higher rates of PTEN loss, for example 77% of CRPC samples studied by Sircar et al. [90], supporting the hypothesis that PTEN loss is associated with these more aggressive tumours. In support of this, in a later study, from 612 patient tumour samples from radical prostatectomies, approximately 20% had lost one or both copies of PTEN, this was very strongly correlated with increased Gleason score and poorer outcome [91]. Consistent with this picture, a recent meta-analysis and review using data from seven previous published studies, most discussed here, found a strong correlation of PTEN genomic deletion with both higher Gleason score and increased capsular penetration [94].

Immunohistochemistry

Although some initial analyses of PTEN by IHC suffered from problems with poor methods and antibodies limiting sensitivity and PTEN specificity, optimization of method and materials have supported the generation of strong data, much strengthened by controls demonstrating a good correlation of PTEN loss by IHC with reduced PTEN signals at the DNA and mRNA levels [9598]. By IHC analyses, both in published studies and online resources such as the Human Protein Atlas (www.proteinatlas.org), staining for the PTEN protein shows a cytoplasmic and nuclear pattern in the luminal and basal epithelial cells of the prostate, as well as being expressed in other cell types [82]. Reported rates of loss of PTEN staining in prostate cancers have been observed in a range of 15–30% in unselected primary tumours, either from biopsy samples or from radical prostatectomies [82,99102]. One common feature to come from this work has been frequently observed intra-tumoural heterogeneity, with regions positive and negative for PTEN staining [82,103,104] indicating that PTEN loss is often not an early founding event in prostate cancer formation. The lack of evidence for disturbed PTEN function in high grade PIN also argues that PTEN loss may be a later event in prostate cancer development [105].

A very important feature that has been observed is a correlation of PTEN loss as judged by IHC with higher grade tumours as judged by Gleason score [82,99,103,104] and with stage, with higher rates of PTEN loss being consistently observed in metastatic and in castration resistant cancers [1,82,101,103,106]. Accordingly, loss of PTEN assessed by IHC has also been independently associated with a variety of poor outcomes, including PSA-measured biochemical recurrence [100], poor clinical outcome [107] and tumours that scored as Gleason grade 6 at tumour biopsy but were upgraded to Gleason 7 or higher when the prostate gland was removed and analysed [71]. The confirmation of the association of PTEN with lethal progression in a recently published prospective study implies that the association of PTEN loss with aggressive disease is not simple because these tumours have a higher mutational burden and more disrupted genome, but further supports the hypothesis that loss of PTEN is not usually an initiating event in prostate cancer, but rather is most frequently a later event that worsens patient outcome [108].

Is PTEN protein expression often reduced in tumours retaining normal PTEN mRNA?

Where reported together, assessment of the PTEN gene by FISH and protein by IHC from tumour biopsies has shown good correlation in many but not all cases and this finding has been used to provide confidence in the presented data. For example, Han et al. [109] reported that all but 1 of the 21 tumours that had PTEN deletion by FISH showed reduced PTEN staining by IHC. More recently, similar results were reported by Lotan et al. [71] and Murphy et al. [110]. However, a strong correlation between gene and protein analysis should not always be expected and a clear possibility, with some support, is that PTEN protein levels are suppressed in prostate tumours retaining wild-type copies of the PTEN gene, due to changes at one or more steps in the gene expression pipeline. Accordingly, it is common for samples to show a positive FISH result and a negative/reduced PTEN IHC, and much less common to have IHC positivity reported in cells carrying PTEN gene loss as assessed by FISH [99,109,111,112].

PTEN function is known to be regulated at the transcriptional, post-transcriptional and post-translational levels through diverse mechanisms both physiologically and in disease [87]. In many cases, the significance of these regulatory mechanisms to the loss of PTEN function during carcinogenesis is still emerging. Examples of reduced PTEN transcription in prostate cancer by changes in transcription factor networks have been described [113,114] and in other cancers by promoter methylation [115,116], although there is little evidence for this in prostate cancer. However, the most recent attention in this area has fallen on changes in the miRNA networks that are able to suppress PTEN expression. Good evidence for a role of miRNA in regulating PTEN in prostate cancer exists [117120] and a number of miRNAs, representing candidate oncogenic miRNAs, or oncomiRs, were shown to bind the 3′-UTR of PTEN [117,119,121]. An added layer of complexity in the post-transcriptional regulation of PTEN has come with its use as an example in work establishing a novel mechanism controlling gene expression. Several mRNAs, including the PTEN pseudogene PTENP1, contain similar miRNA binding sites to PTEN and these have been referred to as competing endogenous RNA [122]. Depletion of PTENP1 or other competing transcripts is proposed to free-up more miRNAs, allowing it to bind to the PTEN mRNA and experimentally led to a reduction in PTEN protein levels [120,121]. Similarly and in support of this model, PTENP1 has been found to undergo genomic copy number loss in a small percentage of sporadic colon cancers [120]. A more recent study also identified a number of long non-coding RNAs from clinical data as candidate tumour suppressors in prostate cancer, which were shown to be able to act as such miRNA-competing ‘sponges’ and the knockdown of which reduced PTEN expression and increased proliferation in the DU145 prostate cell line [118]. These studies add to the great complexity found in mRNA gene expression data and leave the challenge of dissecting the relative significance of individual changes observed in tumour miRNA signatures and telling oncogenic drivers from passengers.

It seems important that in these and other studies, functional loss of PTEN would not be detected if only FISH and/or sequencing are performed, without IHC. Therefore, strong well-validated IHC seems likely to provide the best assessment of PTEN function. PTEN IHC appears reliable and is a promising way to identify patients incorrectly presumed as low risk who may be prone to disease progression, a conclusion recently strengthened by a large prospective study [108]. The fact that PTEN is regulated at many levels beyond transcription may also mean that studies that have used DNA analyses to look at PTEN loss in prostate tumours may have underestimated the frequency at which PTEN is lost in prostate cancer.

In Figure 3 and Table 1, we present a summary showing mean percentage frequencies of reported PTEN loss assessed by different technologies in a large number of independent studies that contain data addressing the frequencies of PTEN loss and reduction in prostate cancer cohorts. This diagram is clearly a simplification, as side-by-side it presents data from many studies using somewhat different methodologies and patient groups, ignoring many specific features of the studies included. However, the overall pattern of data is compelling, illustrating the higher rates of loss observed in metastatic/CRPC patients. Also, the occurrence of undetectable PTEN expression by IHC appears consistently higher than the apparent rates of homozygous loss by FISH and other genetic assessments, giving further support to the proposal (see above) that PTEN protein levels in prostate cancer are often reduced in tumour cells retaining healthy levels of wild-type PTEN mRNA [111]. This is in notable contrast with some other cancers where loss is usually at the level of mRNA, e.g. breast cancer [123].

A comparison of PTEN alteration frequencies in primary tumours and CRPC/metastatic prostate cancer

Figure 3
A comparison of PTEN alteration frequencies in primary tumours and CRPC/metastatic prostate cancer

The percentage of samples displaying loss of PTEN detected by IHC, FISH or other genetic methods (e.g. sequencing, array CGH) in individual studies of primary and CRPC/metastatic prostate cancers is shown, along with the mean percentage from these aggregated studies. Where possible, data for loss of PTEN detected by FISH have been separated to display heterozygous and homozygous loss, along with the combined number for each.

Figure 3
A comparison of PTEN alteration frequencies in primary tumours and CRPC/metastatic prostate cancer

The percentage of samples displaying loss of PTEN detected by IHC, FISH or other genetic methods (e.g. sequencing, array CGH) in individual studies of primary and CRPC/metastatic prostate cancers is shown, along with the mean percentage from these aggregated studies. Where possible, data for loss of PTEN detected by FISH have been separated to display heterozygous and homozygous loss, along with the combined number for each.

Table 1
Detailed analysis for Figure 3 

The percentage of samples with altered PTEN and total sample number (n) are shown for each study, grouped by technique used and by primary or CRPC/metastatic disease (for primary disease, PIN was not included, and tumours were not sorted according to stage in our analyses). Where the same study reported PTEN alterations in primary and CRPC/metastatic disease, the alteration frequency and sample size appear in adjacent columns. Where the same study used and compared with different methods, e.g. FISH and IHC, this is indicated by a * by the reference. The scoring criteria were as follows: FISH analysis–counted as loss initially, then sorted into heterozygous (het) or homozygous (hom) loss IHC–scored according to the paper criteria. Where possible, reduced/weak was included as loss, along with absent, but this was not always possible. Other genomic–including sequencing, PCR, microsatellite analyses and array CGH A Student's t test was used to compare the primary and CRPC/metastatic data, and the P-values are shown.

 Primary tumours Metastatic/CRPC  
Method n het/ (%) hom/ (%) Reference N het/ (%) hom/ (%) Reference P-value 
FISH 17 251 10 7 [10953.7 41 29.3 24.4 [1090.1721 (het) 
 23 57   [10652 57   [1060.0001 (hom) 
 40 330 24.8 15.2 [9262 32 38 34 [92 
 40.7 118 18.6 22.1 [14344.9 49 12.2 32.7 [143 
 43.9 107 39.3 4.6 [8890 10 60 30 [88 
 14.9 643 2.8 12.1 [99]* 40.5 37 18.9 21.6 [144]*  
 17.4 322   [14563.6 55 27.3 36.3 [146 
 18.3 612 9 9.3 [9176.8 56 33.9 42.9 [90 
 19.7 2131 8.1 12.1 [147      
 21.8 339 9.4 12.4 [148      
 22.4 3756 8 14.4 [149      
 30.9 97 17.5 13.4 [110      
 32.6 187 5.3 27.3 [112      
 41.7 134 31.3 10.4 [150      
 41.9 43 41.9 0 [93      
 68.6 35 62.9 5.7 [89      
IHC 15 282   [10145 122   [1010.0056 
 38 308   [8248 50   [82 
 55.2 58   [15168.8 15   [151 
 11.5 174   [7160.5 38   [144]*  
 17.6 675   [99]* 78.9 19   [152 
 20.2 109   [103      
 21.5 65   [153      
 25 1044   [108      
 27.2 103   [100      
 31 357   [15440 357   [154 
 33 107   [110]*       
 33.1 118   [155      
 35.1 316   [148      
 36 194   [104      
 61 57   [156      
Other genomic 16 32   [15733.3   [1570.0003 
 21 181   [142 37   [1 
 23 112   [15859.5 42   [158 
 11.8 51   [8333.3 81   [159 
 16 57   [8140 150   [17 
 16.7 60   [16044.4 18   [161 
 17 333   [7947 50   [16 
 17.5 40   [162      
 23 126   [110]*       
 24 112   [163      
 28 55   [164      
 35 40   [165      
 38.4 125   [127      
 Primary tumours Metastatic/CRPC  
Method n het/ (%) hom/ (%) Reference N het/ (%) hom/ (%) Reference P-value 
FISH 17 251 10 7 [10953.7 41 29.3 24.4 [1090.1721 (het) 
 23 57   [10652 57   [1060.0001 (hom) 
 40 330 24.8 15.2 [9262 32 38 34 [92 
 40.7 118 18.6 22.1 [14344.9 49 12.2 32.7 [143 
 43.9 107 39.3 4.6 [8890 10 60 30 [88 
 14.9 643 2.8 12.1 [99]* 40.5 37 18.9 21.6 [144]*  
 17.4 322   [14563.6 55 27.3 36.3 [146 
 18.3 612 9 9.3 [9176.8 56 33.9 42.9 [90 
 19.7 2131 8.1 12.1 [147      
 21.8 339 9.4 12.4 [148      
 22.4 3756 8 14.4 [149      
 30.9 97 17.5 13.4 [110      
 32.6 187 5.3 27.3 [112      
 41.7 134 31.3 10.4 [150      
 41.9 43 41.9 0 [93      
 68.6 35 62.9 5.7 [89      
IHC 15 282   [10145 122   [1010.0056 
 38 308   [8248 50   [82 
 55.2 58   [15168.8 15   [151 
 11.5 174   [7160.5 38   [144]*  
 17.6 675   [99]* 78.9 19   [152 
 20.2 109   [103      
 21.5 65   [153      
 25 1044   [108      
 27.2 103   [100      
 31 357   [15440 357   [154 
 33 107   [110]*       
 33.1 118   [155      
 35.1 316   [148      
 36 194   [104      
 61 57   [156      
Other genomic 16 32   [15733.3   [1570.0003 
 21 181   [142 37   [1 
 23 112   [15859.5 42   [158 
 11.8 51   [8333.3 81   [159 
 16 57   [8140 150   [17 
 16.7 60   [16044.4 18   [161 
 17 333   [7947 50   [16 
 17.5 40   [162      
 23 126   [110]*       
 24 112   [163      
 28 55   [164      
 35 40   [165      
 38.4 125   [127      

As an additional note in consideration of methods to detect genetic changes in PTEN, progress is being made in detecting tumour specific gene copy number changes and mutations in cell-free DNA in blood and urine, which is a challenge given the large background of unmutated DNA from other tissues [124,125]. The possibility for prostate cancer patients of tumour characterization and prognosis from non-invasive liquid biopsy is appealing, yet the detection sensitivities for free variant DNA must be improved before these techniques can be applied to most patients.

In addition to the studies discussed above that have selected PTEN to test its utility as a prognostic biomarker, other studies have undertaken to identify markers associated with disease severity taking a global unbiased approach and in some cases have identified PTEN loss as a component of aggressive disease signatures (e.g. [1,126,127]). Of these global studies, the majority look for signatures of aggressive disease–one notable exception was the work of Irshad et al. [128], which identified an ‘indolence signature’.

TARGETED THERAPIES TO TREAT PROSTATE CANCERS LACKING PTEN

One notable feature of the PI3K/PTEN signalling pathway is its reliance on protein and lipid kinases, which are enzyme groups with a good track record of druggability. Detailed strategies and progress of drug programmes targeting the PI3K-pathway and components downstream including TOR have been reviewed elsewhere [129]. To summarize briefly, a number of pan PI3K and allosteric or ATP competitive AKT and mTOR inhibitors are currently in phase I or II clinical trials for prostate cancer [130]. Additionally dual PI3K–mTOR inhibitors BEZ235 and GDC-0980 are in phase I/II trials. To date, clinical trials of inhibitors of PI3K and TOR in prostate cancer patients have achieved very poor response rates as monotherapy (e.g. [131]). However, a key point is the demonstration that many of these drugs successfully and relatively selectively inhibit their target in vivo. This provides hope that successful applications for them in the treatment of prostate cancer may be identified. It is also noteworthy that in most of these trials, a small minority of patients did respond to treatment, yet no rationale and predictive biomarkers have yet emerged that would allow them to be selected in advance. Efforts are now focusing on stratification of patients prior to treatment following on from high response rates observed in a phase II trial of patients treated with the PARP inhibitor olaparib, who had existing mutations in DNA repair genes [132], and the use of combination therapy. For example, since a negative feedback loop exists between the PI3K–AKT pathway and AR signalling, it may be necessary to inhibit both pathways in patients. In support of this, AR and PI3K inhibition in a preclinical model using patient xenografts showed tumour regression [133], and clinical trials are underway (reviewed in [134]).

REGULATORY SYSTEMS INTERACTING WITH PI3K/PTEN

At the molecular level, several proteins that directly and robustly interact with PTEN are found to be altered themselves in prostate cancer. Amplification of the recognized PTEN inhibitor and RAC1 activator, PREX2, has been observed as well as (uncommon) deletion of the PTEN scaffold PAR3 ([135,136] and www.cbioportal.org). Additionally, potential cross-talk with other regulatory systems with established roles in oncogenesis is provided in reports that PTEN can directly interact with other major tumour suppressors and oncogenes, such as p53, β-catenin and SRC [137139]. On the other hand, the significance of these regulatory influences on, or by, PTEN remains poorly understood.

At a higher level, signalling through the PI3K network influences major cellular processes such as cell-cycle entry and protein synthesis providing outputs that are integrated with those from other semi-independent functional networks. As discussed, examples of such pathways are also frequently dysregulated in prostate cancer, e.g. programmes of transcriptional regulation by the AR, TP53 and by ETS family transcription factors. The consequences of such pathway integration and cross-talk generally appear strongly context dependent and hard to study and predict. However, with strong relevance to prostate cancer development, multiple mechanisms of bidirectional negative feedback have been observed between AR and PI3K/PTEN signalling, the disruption of which is required for the strong activation of both PI3K and AR pathways observed in some aggressive tumours [14,140142].

CONCLUDING REMARKS

The role of PTEN as a suppressor of prostate cancer and the association of its loss with aggressive disease are well established and increasing numbers of drugs are available to target different points in the PTEN/PI3K/TOR signalling network. However, these agents have so far had limited success as monotherapies and progress has been slow to develop combination therapies and predictive biomarkers to match drugs with patients who will respond. The first significant impact of our understanding of signalling via PTEN/PI3K in terms of clinical impact may be the use of PTEN functional assessment as a prognostic biomarker.

FUNDING

This work was supported by the Prostate Cancer U.K. [grant number PG14-006]; the Chief Scientist Office [grant number ETM-433]; and the Brain Tumour Charity [grant number GN-000344].

Abbreviations

     
  • AR

    androgen receptor

  •  
  • CRPC

    castrate-resistant prostate cancer

  •  
  • ETS

    E26 transformation specific

  •  
  • FISH

    fluorescence in situ hybridization

  •  
  • IHC

    immunohistochemistry

  •  
  • MTOR

    mechanistic target of rapamycin

  •  
  • PI3K

    phosphoinositide 3-kinase

  •  
  • PIN

    prostate intraepithelial neoplasia

  •  
  • PI3P

    phosphatidylinositol 3-phosphate

  •  
  • PI(3

    4)P2, phosphatidylinositol 3,4-bisphosphate

  •  
  • PI(4

    5)P2, phosphatidylinositol 4,5-bisphosphate

  •  
  • PIP3

    phosphatidylinositol 3,4,5-trisphosphate

  •  
  • RTK

    receptor tyrosine kinase

References

References
1
Taylor
B.S.
Schultz
N.
Hieronymus
H.
Gopalan
A.
Xiao
Y.
Carver
B.S.
Arora
V.K.
Kaushik
P.
Cerami
E.
Reva
B.
, et al. 
Integrative genomic profiling of human prostate cancer
Cancer Cell
2010
, vol. 
18
 (pg. 
11
-
22
)
2
Yuan
T.L.
Cantley
L.C.
PI3K pathway alterations in cancer: variations on a theme
Oncogene
2008
, vol. 
27
 (pg. 
5497
-
5510
)
3
Vanhaesebroeck
B.
Stephens
L.
Hawkins
P.
PI3K signalling: the path to discovery and understanding
Nat. Rev. Mol. Cell Biol.
2012
, vol. 
13
 (pg. 
195
-
203
)
4
Liu
P.
Cheng
H.
Roberts
T.M.
Zhao
J.J.
Targeting the phosphoinositide 3-kinase pathway in cancer
Nat. Rev. Drug Discov.
2009
, vol. 
8
 (pg. 
627
-
644
)
5
Samuels
Y.
Wang
Z.
Bardelli
A.
Silliman
N.
Ptak
J.
Szabo
S.
Yan
H.
Gazdar
A.
Powell
S.M.
Riggins
G.J.
, et al. 
High frequency of mutations of the PIK3CA gene in human cancers
Science
2004
, vol. 
304
 pg. 
554
 
6
Barbieri
C.E.
Tomlins
S.A.
The prostate cancer genome: perspectives and potential
Urologic Oncol.
2014
, vol. 
32
 (pg. 
53.e15
-
53.e22
)
7
Fritsch
R.
de Krijger
I.
Fritsch
K.
George
R.
Reason
B.
Kumar
M.S.
Diefenbacher
M.
Stamp
G.
Downward
J.
RAS and RHO families of GTPases directly regulate distinct phosphoinositide 3-kinase isoforms
Cell
2013
, vol. 
153
 (pg. 
1050
-
1063
)
8
Jia
S.
Liu
Z.
Zhang
S.
Liu
P.
Zhang
L.
Lee
S.H.
Zhang
J.
Signoretti
S.
Loda
M.
Roberts
T.M.
, et al. 
Essential roles of PI(3)K-p110beta in cell growth, metabolism and tumorigenesis
Nature
2008
, vol. 
454
 (pg. 
776
-
779
)
9
Wee
S.
Wiederschain
D.
Maira
S.M.
Loo
A.
Miller
C.
deBeaumont
R.
Stegmeier
F.
Yao
Y.M.
Lengauer
C.
PTEN-deficient cancers depend on PIK3CB
Proc. Natl. Acad. Sci. U.S.A.
2008
, vol. 
105
 (pg. 
13057
-
13062
)
10
Torbett
N.E.
Luna-Moran
A.
Knight
Z.A.
Houk
A.
Moasser
M.
Weiss
W.
Shokat
K.M.
Stokoe
D.
A chemical screen in diverse breast cancer cell lines reveals genetic enhancers and suppressors of sensitivity to PI3K isoform-selective inhibition
Biochem. J.
2008
, vol. 
415
 (pg. 
97
-
110
)
11
Berenjeno
I.M.
Guillermet-Guibert
J.
Pearce
W.
Gray
A.
Fleming
S.
Vanhaesebroeck
B.
Both p110alpha and p110beta isoforms of PI3K can modulate the impact of loss-of-function of the PTEN tumour suppressor
Biochem. J.
2012
, vol. 
442
 (pg. 
151
-
159
)
12
Schmit
F.
Utermark
T.
Zhang
S.
Wang
Q.
Von
T.
Roberts
T.M.
Zhao
J.J.
PI3K isoform dependence of PTEN-deficient tumors can be altered by the genetic context
Proc. Natl. Acad. Sci. U.S.A.
2014
, vol. 
111
 (pg. 
6395
-
6400
)
13
Costa
C.
Ebi
H.
Martini
M.
Beausoleil
S.A.
Faber
A.C.
Jakubik
C.T.
Huang
A.
Wang
Y.
Nishtala
M.
Hall
B.
, et al. 
Measurement of PIP3 levels reveals an unexpected role for p110beta in early adaptive responses to p110alpha-specific inhibitors in luminal breast cancer
Cancer Cell
2015
, vol. 
27
 (pg. 
97
-
108
)
14
Schwartz
S.
Wongvipat
J.
Trigwell
C.B.
Hancox
U.
Carver
B.S.
Rodrik-Outmezguine
V.
Will
M.
Yellen
P.
de Stanchina
E.
Baselga
J.
, et al. 
Feedback suppression of PI3Kalpha signaling in PTEN-mutated tumors is relieved by selective inhibition of PI3Kbeta
Cancer Cell
2015
, vol. 
27
 (pg. 
109
-
122
)
15
Berger
M.F.
Lawrence
M.S.
Demichelis
F.
Drier
Y.
Cibulskis
K.
Sivachenko
A.Y.
Sboner
A.
Esgueva
R.
Pflueger
D.
Sougnez
C.
, et al. 
The genomic complexity of primary human prostate cancer
Nature
2011
, vol. 
470
 (pg. 
214
-
220
)
16
Grasso
C.S.
Wu
Y.M.
Robinson
D.R.
Cao
X.
Dhanasekaran
S.M.
Khan
A.P.
Quist
M.J.
Jing
X.
Lonigro
R.J.
Brenner
J.C.
, et al. 
The mutational landscape of lethal castration-resistant prostate cancer
Nature
2012
, vol. 
487
 (pg. 
239
-
243
)
17
Robinson
D.
Van Allen
E.M.
Wu
Y.M.
Schultz
N.
Lonigro
R.J.
Mosquera
J.M.
Montgomery
B.
Taplin
M.E.
Pritchard
C.C.
Attard
G.
, et al. 
Integrative clinical genomics of advanced prostate cancer
Cell
2015
, vol. 
161
 (pg. 
1215
-
1228
)
18
Jungmichel
S.
Sylvestersen
K.B.
Choudhary
C.
Nguyen
S.
Mann
M.
Nielsen
M.L.
Specificity and commonality of the phosphoinositide-binding proteome analyzed by quantitative mass spectrometry
Cell Rep.
2014
, vol. 
6
 (pg. 
578
-
591
)
19
Leslie
N.R.
Dixon
M.J.
Schenning
M.
Gray
A.
Batty
I.H.
Distinct inactivation of PI3K signalling by PTEN and 5-phosphatases
Adv. Biol. Regul.
2012
, vol. 
52
 (pg. 
205
-
213
)
20
Park
W.S.
Heo
W.D.
Whalen
J.H.
O'Rourke
N.A.
Bryan
H.M.
Meyer
T.
Teruel
M.N.
Comprehensive identification of PIP3-regulated PH domains from C. elegans to H. sapiens by model prediction and live imaging
Mol. Cell
2008
, vol. 
30
 (pg. 
381
-
392
)
21
Chen
M.L.
Xu
P.Z.
Peng
X.D.
Chen
W.S.
Guzman
G.
Yang
X.
Di Cristofano
A.
Pandolfi
P.P.
Hay
N.
The deficiency of Akt1 is sufficient to suppress tumor development in Pten+/- mice
Genes Dev.
2006
, vol. 
20
 (pg. 
1569
-
1574
)
22
Ogg
S.
Ruvkun
G.
The C. elegans PTEN homolog, DAF-18, acts in the insulin receptor-like metabolic signaling pathway
Mol. Cell
1998
, vol. 
2
 (pg. 
887
-
893
)
23
Paradis
S.
Ruvkun
G.
Caenorhabditis elegans Akt/PKB transduces insulin receptor-like signals from AGE-1 PI3 kinase to the DAF-16 transcription factor
Genes Dev.
1998
, vol. 
12
 (pg. 
2488
-
2498
)
24
Stocker
H.
Andjelkovic
M.
Oldham
S.
Laffargue
M.
Wymann
M.P.
Hemmings
B.A.
Hafen
E.
Living with lethal PIP3 levels: viability of flies lacking PTEN restored by a PH domain mutation in Akt/PKB
Science
2002
, vol. 
295
 (pg. 
2088
-
2091
)
25
Toker
A.
Marmiroli
S.
Signaling specificity in the Akt pathway in biology and disease
Adv. Biol. Regul.
2014
, vol. 
55
 (pg. 
28
-
38
)
26
Manning
B.D.
Cantley
L.C.
AKT/PKB signaling: navigating downstream
Cell
2007
, vol. 
129
 (pg. 
1261
-
1274
)
27
Dibble
C.C.
Cantley
L.C.
Regulation of mTORC1 by PI3K signaling
Trends Cell Biol.
2015
, vol. 
25
 (pg. 
545
-
555
)
28
Chadborn
N.H.
Ahmed
A.I.
Holt
M.R.
Prinjha
R.
Dunn
G.A.
Jones
G.E.
Eickholt
B.J.
PTEN couples Sema3A signalling to growth cone collapse
J. Cell Sci.
2006
, vol. 
119
 (pg. 
951
-
957
)
29
Leslie
N.R.
Batty
I.H.
Maccario
H.
Davidson
L.
Downes
C.P.
Understanding PTEN regulation: PIP2, polarity and protein stability
Oncogene
2008
, vol. 
27
 (pg. 
5464
-
5476
)
30
Parent
C.A.
Blacklock
B.J.
Froehlich
W.M.
Murphy
D.B.
Devreotes
P.N.
G protein signaling events are activated at the leading edge of chemotactic cells
Cell
1998
, vol. 
95
 (pg. 
81
-
91
)
31
Servant
G.
Weiner
O.D.
Herzmark
P.
Balla
T.
Sedat
J.W.
Bourne
H.R.
Polarization of chemoattractant receptor signaling during neutrophil chemotaxis
Science
2000
, vol. 
287
 (pg. 
1037
-
1040
)
32
Watton
S.J.
Downward
J.
Akt/PKB localisation and 3' phosphoinositide generation at sites of epithelial cell-matrix and cell-cell interaction
Curr. Biol.
1999
, vol. 
9
 (pg. 
433
-
436
)
33
Fan
Q.W.
Cheng
C.
Knight
Z.A.
Haas-Kogan
D.
Stokoe
D.
James
C.D.
McCormick
F.
Shokat
K.M.
Weiss
W.A.
EGFR signals to mTOR through PKC and independently of Akt in glioma
Sci. Signal.
2009
, vol. 
2
 pg. 
ra4
 
34
Vasudevan
K.M.
Barbie
D.A.
Davies
M.A.
Rabinovsky
R.
McNear
C.J.
Kim
J.J.
Hennessy
B.T.
Tseng
H.
Pochanard
P.
Kim
S.Y.
, et al. 
AKT-independent signaling downstream of oncogenic PIK3CA mutations in human cancer
Cancer Cell
2009
, vol. 
16
 (pg. 
21
-
32
)
35
Vivanco
I.
Palaskas
N.
Tran
C.
Finn
S.P.
Getz
G.
Kennedy
N.J.
Jiao
J.
Rose
J.
Xie
W.
Loda
M.
, et al. 
Identification of the JNK signaling pathway as a functional target of the tumor suppressor PTEN
Cancer Cell
2007
, vol. 
11
 (pg. 
555
-
569
)
36
Berglund
F.M.
Weerasinghe
N.R.
Davidson
L.
Lim
J.C.
Eickholt
B.J.
Leslie
N.R.
Disruption of epithelial architecture caused by loss of PTEN or by oncogenic mutant p110alpha/PIK3CA but not by HER2 or mutant AKT1
Oncogene
2013
, vol. 
32
 (pg. 
4417
-
4426
)
37
Tibarewal
P.
Zilidis
G.
Spinelli
L.
Schurch
N.
Maccario
H.
Gray
A.
Perera
N.M.
Davidson
L.
Barton
G.J.
Leslie
N.R.
PTEN protein phosphatase activity correlates with control of gene expression and invasion, a tumor-suppressing phenotype, but not with AKT activity
Sci. Signal.
2012
, vol. 
5
 pg. 
ra18
 
38
Lauring
J.
Cosgrove
D.P.
Fontana
S.
Gustin
J.P.
Konishi
H.
Abukhdeir
A.M.
Garay
J.P.
Mohseni
M.
Wang
G.M.
Higgins
M.J.
, et al. 
Knock in of the AKT1 E17K mutation in human breast epithelial cells does not recapitulate oncogenic PIK3CA mutations
Oncogene
2010
, vol. 
29
 (pg. 
2337
-
2345
)
39
Mancini
M.L.
Lien
E.C.
Toker
A.
Oncogenic AKT1(E17K) mutation induces mammary hyperplasia but prevents HER2-driven tumorigenesis
Oncotarget
2016
, vol. 
7
 (pg. 
17301
-
17313
)
[PubMed]
40
Eramo
M.J.
Mitchell
C.A.
Regulation of PtdIns(3,4,5)P3/Akt signalling by inositol polyphosphate 5-phosphatases
Biochem. Soc. Trans.
2016
, vol. 
44
 (pg. 
240
-
252
)
41
Gewinner
C.
Wang
Z.C.
Richardson
A.
Teruya-Feldstein
J.
Etemadmoghadam
D.
Bowtell
D.
Barretina
J.
Lin
W.M.
Rameh
L.
Salmena
L.
, et al. 
Evidence that inositol polyphosphate 4-phosphatase type II is a tumor suppressor that inhibits PI3K signaling
Cancer Cell
2009
, vol. 
16
 (pg. 
115
-
125
)
42
Woolley
J.F.
Dzneladze
I.
Salmena
L.
Phosphoinositide signaling in cancer: INPP4B Akt(s) out
Trends Mol. Med.
2015
, vol. 
21
 (pg. 
530
-
532
)
43
Cancer Genome Atlas Research Network
Comprehensive genomic characterization defines human glioblastoma genes and core pathways
Nature
2008
, vol. 
455
 (pg. 
1061
-
1068
)
44
Stratton
M.R.
Campbell
P.J.
Futreal
P.A.
The cancer genome
Nature
2009
, vol. 
458
 (pg. 
719
-
724
)
45
Gray
I.C.
Phillips
S.M.
Lee
S.J.
Neoptolemos
J.P.
Weissenbach
J.
Spurr
N.K.
Loss of the chromosomal region 10q23-25 in prostate cancer
Cancer Res.
1995
, vol. 
55
 (pg. 
4800
-
4803
)
46
Herbst
R.A.
Weiss
J.
Ehnis
A.
Cavenee
W.K.
Arden
K.C.
Loss of heterozygosity for 10q22-10qter in malignant melanoma progression
Cancer Res.
1994
, vol. 
54
 (pg. 
3111
-
3114
)
47
Morita
R.
Saito
S.
Ishikawa
J.
Ogawa
O.
Yoshida
O.
Yamakawa
K.
Nakamura
Y.
Common regions of deletion on chromosomes 5q, 6q, and 10q in renal cell carcinoma
Cancer Res.
1991
, vol. 
51
 (pg. 
5817
-
5820
)
48
Peiffer
S.L.
Herzog
T.J.
Tribune
D.J.
Mutch
D.G.
Gersell
D.J.
Goodfellow
P.J.
Allelic loss of sequences from the long arm of chromosome 10 and replication errors in endometrial cancers
Cancer Res.
1995
, vol. 
55
 (pg. 
1922
-
1926
)
49
Li
J.
Yen
C.
Liaw
D.
Podsypanina
K.
Bose
S.
Wang
S.I.
Puc
J.
Miliaresis
C.
Rodgers
L.
McCombie
R.
, et al. 
PTEN, a putative protein tyrosine phosphatase gene mutated in human brain, breast, and prostate cancer
Science
1997
, vol. 
275
 (pg. 
1943
-
1947
)
50
Steck
P.A.
Pershouse
M.A.
Jasser
S.A.
Yung
W.K.
Lin
H.
Ligon
A.H.
Langford
L.A.
Baumgard
M.L.
Hattier
T.
Davis
T.
, et al. 
Identification of a candidate tumour suppressor gene, MMAC1, at chromosome 10q23.3 that is mutated in multiple advanced cancers
Nat. Genet.
1997
, vol. 
15
 (pg. 
356
-
362
)
51
Liaw
D.
Marsh
D.J.
Li
J.
Dahia
P.L.
Wang
S.I.
Zheng
Z.
Bose
S.
Call
K.M.
Tsou
H.C.
Peacocke
M.
, et al. 
Germline mutations of the PTEN gene in Cowden disease, an inherited breast and thyroid cancer syndrome
Nat. Genet.
1997
, vol. 
16
 (pg. 
64
-
67
)
52
Marsh
D.J.
Dahia
P.L.
Zheng
Z.
Liaw
D.
Parsons
R.
Gorlin
R.J.
Eng
C.
Germline mutations in PTEN are present in Bannayan-Zonana syndrome
Nat. Genet.
1997
, vol. 
16
 (pg. 
333
-
334
)
53
Barbosa
M.
Henrique
M.
Pinto-Basto
J.
Claes
K.
Soares
G.
Prostate cancer in Cowden syndrome: somatic loss and germline mutation of the PTEN gene
Cancer Genet.
2011
, vol. 
204
 (pg. 
224
-
225
)
54
Li
D.M.
Sun
H.
TEP1, encoded by a candidate tumor suppressor locus, is a novel protein tyrosine phosphatase regulated by transforming growth factor beta
Cancer Res.
1997
, vol. 
57
 (pg. 
2124
-
2129
)
55
Myers
M.P.
Stolarov
J.P.
Eng
C.
Li
J.
Wang
S.I.
Wigler
M.H.
Parsons
R.
Tonks
N.K.
P-TEN, the tumor suppressor from human chromosome 10q23, is a dual-specificity phosphatase
Proc. Natl. Acad. Sci. U.S.A.
1997
, vol. 
94
 (pg. 
9052
-
9057
)
56
Maehama
T.
Dixon
J.E.
The tumor suppressor, PTEN/MMAC1, dephosphorylates the lipid second messenger, phosphatidylinositol 3,4,5-trisphosphate
J. Biol. Chem.
1998
, vol. 
273
 (pg. 
13375
-
13378
)
57
Myers
M.P.
Pass
I.
Batty
I.H.
Van der Kaay
J.
Stolarov
J.P.
Hemmings
B.A.
Wigler
M.H.
Downes
C.P.
Tonks
N.K.
The lipid phosphatase activity of PTEN is critical for its tumor supressor function
Proc. Natl. Acad. Sci. U.S.A.
1998
, vol. 
95
 (pg. 
13513
-
13518
)
58
Furnari
F.B.
Huang
H.J.
Cavenee
W.K.
The phosphoinositol phosphatase activity of PTEN mediates a serum-sensitive G1 growth arrest in glioma cells
Cancer Res.
1998
, vol. 
58
 (pg. 
5002
-
5008
)
59
Song
M.S.
Salmena
L.
Pandolfi
P.P.
The functions and regulation of the PTEN tumour suppressor
Nat. Rev. Mol. Cell Biol.
2012
, vol. 
13
 (pg. 
283
-
296
)
60
Worby
C.A.
Dixon
J.E.
Pten
Annu. Rev. Biochem.
2014
, vol. 
83
 (pg. 
641
-
669
)
61
Papa
A.
Wan
L.
Bonora
M.
Salmena
L.
Song
M.S.
Hobbs
R.M.
Lunardi
A.
Webster
K.
Ng
C.
Newton
R.H.
, et al. 
Cancer-associated PTEN mutants act in a dominant-negative manner to suppress PTEN protein function
Cell
2014
, vol. 
157
 (pg. 
595
-
610
)
62
Wang
H.
Karikomi
M.
Naidu
S.
Rajmohan
R.
Caserta
E.
Chen
H.Z.
Rawahneh
M.
Moffitt
J.
Stephens
J.A.
Fernandez
S.A.
, et al. 
Allele-specific tumor spectrum in pten knockin mice
Proc. Natl. Acad. Sci. U.S.A.
2010
, vol. 
107
 (pg. 
5142
-
5147
)
63
Vazquez
F.
Matsuoka
S.
Sellers
W.R.
Yanagida
T.
Ueda
M.
Devreotes
P.N.
Tumor suppressor PTEN acts through dynamic interaction with the plasma membrane
Proc. Natl. Acad. Sci. U.S.A.
2006
, vol. 
103
 (pg. 
3633
-
3638
)
64
Lindsay
Y.
McCoull
D.
Davidson
L.
Leslie
N.R.
Fairservice
A.
Gray
A.
Lucocq
J.
Downes
C.P.
Localization of agonist-sensitive PtdIns(3,4,5)P3 reveals a nuclear pool that is insensitive to PTEN expression
J. Cell Sci.
2006
, vol. 
119
 (pg. 
5160
-
5168
)
65
Naguib
A.
Bencze
G.
Cho
H.
Zheng
W.
Tocilj
A.
Elkayam
E.
Faehnle
C.R.
Jaber
N.
Pratt
C.P.
Chen
M.
, et al. 
PTEN functions by recruitment to cytoplasmic vesicles
Mol. Cell
2015
, vol. 
58
 (pg. 
255
-
268
)
66
Knafo
S.
Sanchez-Puelles
C.
Palomer
E.
Delgado
I.
Draffin
J.E.
Mingo
J.
Wahle
T.
Kaleka
K.
Mou
L.
Pereda-Perez
I.
, et al. 
PTEN recruitment controls synaptic and cognitive function in Alzheimer's models
Nat. Neurosci.
2016
, vol. 
19
 (pg. 
443
-
453
)
67
Leslie
N.R.
Yang
X.
Downes
C.P.
Weijer
C.J.
PtdIns(3,4,5)P3-dependent and -independent roles for PTEN in the control of cell migration
Curr. Biol.
2007
, vol. 
17
 (pg. 
115
-
125
)
68
Martin-Belmonte
F.
Gassama
A.
Datta
A.
Yu
W.
Rescher
U.
Gerke
V.
Mostov
K.
PTEN-mediated apical segregation of phosphoinositides controls epithelial morphogenesis through Cdc42
Cell
2007
, vol. 
128
 (pg. 
383
-
397
)
69
Wu
H.
Feng
W.
Chen
J.
Chan
L.N.
Huang
S.
Zhang
M.
PDZ domains of Par-3 as potential phosphoinositide signaling integrators
Mol. Cell
2007
, vol. 
28
 (pg. 
886
-
898
)
70
Kim
J.W.
Kang
K.H.
Burrola
P.
Mak
T.W.
Lemke
G.
Retinal degeneration triggered by inactivation of PTEN in the retinal pigment epithelium
Genes Dev.
2008
, vol. 
22
 (pg. 
3147
-
3157
)
71
Lotan
T.L.
Carvalho
F.L.
Peskoe
S.B.
Hicks
J.L.
Good
J.
Fedor
H.L.
Humphreys
E.
Han
M.
Platz
E.A.
Squire
J.A.
, et al. 
PTEN loss is associated with upgrading of prostate cancer from biopsy to radical prostatectomy
Mod. Pathol.
2015
, vol. 
28
 (pg. 
128
-
137
)
72
Freeman
D.
Lesche
R.
Kertesz
N.
Wang
S.
Li
G.
Gao
J.
Groszer
M.
Martinez-Diaz
H.
Rozengurt
N.
Thomas
G.
, et al. 
Genetic background controls tumor development in PTEN-deficient mice
Cancer Res.
2006
, vol. 
66
 (pg. 
6492
-
6496
)
73
Stambolic
V.
Tsao
M.S.
Macpherson
D.
Suzuki
A.
Chapman
W.B.
Mak
T.W.
High incidence of breast and endometrial neoplasia resembling human Cowden syndrome in pten+/- mice
Cancer Res.
2000
, vol. 
60
 (pg. 
3605
-
3611
)
74
Trotman
L.C.
Niki
M.
Dotan
Z.A.
Koutcher
J.A.
Di Cristofano
A.
Xiao
A.
Khoo
A.S.
Roy-Burman
P.
Greenberg
N.M.
Van Dyke
T.
, et al. 
Pten dose dictates cancer progression in the prostate
PLoS Biol.
2003
, vol. 
1
 pg. 
E59
 
75
Alimonti
A.
Carracedo
A.
Clohessy
J.G.
Trotman
L.C.
Nardella
C.
Egia
A.
Salmena
L.
Sampieri
K.
Haveman
W.J.
Brogi
E.
, et al. 
Subtle variations in Pten dose determine cancer susceptibility
Nat. Genet.
2010
, vol. 
42
 (pg. 
454
-
458
)
76
Garcia-Cao
I.
Song
M.S.
Hobbs
R.M.
Laurent
G.
Giorgi
C.
de Boer
V.C.
Anastasiou
D.
Ito
K.
Sasaki
A.T.
Rameh
L.
, et al. 
Systemic elevation of PTEN induces a tumor-suppressive metabolic state
Cell
2012
, vol. 
149
 (pg. 
49
-
62
)
77
Ortega-Molina
A.
Efeyan
A.
Lopez-Guadamillas
E.
Munoz-Martin
M.
Gomez-Lopez
G.
Canamero
M.
Mulero
F.
Pastor
J.
Martinez
S.
Romanos
E.
, et al. 
Pten positively regulates brown adipose function, energy expenditure, and longevity
Cell Metab.
2012
, vol. 
15
 (pg. 
382
-
394
)
78
Boyd
L.K.
Mao
X.
Lu
Y.J.
The complexity of prostate cancer: genomic alterations and heterogeneity
Nat. Rev. Urol.
2012
, vol. 
9
 (pg. 
652
-
664
)
79
Cancer Genome Atlas Research Network
The molecular taxonomy of primary prostate cancer
Cell
2015
, vol. 
163
 (pg. 
1011
-
1025
)
80
Wang
S.
Gao
J.
Lei
Q.
Rozengurt
N.
Pritchard
C.
Jiao
J.
Thomas
G.V.
Li
G.
Roy-Burman
P.
Nelson
P.S.
, et al. 
Prostate-specific deletion of the murine Pten tumor suppressor gene leads to metastatic prostate cancer
Cancer Cell
2003
, vol. 
4
 (pg. 
209
-
221
)
81
Baca
S.C.
Prandi
D.
Lawrence
M.S.
Mosquera
J.M.
Romanel
A.
Drier
Y.
Park
K.
Kitabayashi
N.
MacDonald
T.Y.
Ghandi
M.
, et al. 
Punctuated evolution of prostate cancer genomes
Cell
2013
, vol. 
153
 (pg. 
666
-
677
)
82
Lotan
T.L.
Gurel
B.
Sutcliffe
S.
Esopi
D.
Liu
W.
Xu
J.
Hicks
J.L.
Park
B.H.
Humphreys
E.
Partin
A.W.
, et al. 
PTEN protein loss by immunostaining: analytic validation and prognostic indicator for a high risk surgical cohort of prostate cancer patients
Clin. Cancer Res.
2011
, vol. 
17
 (pg. 
6563
-
6573
)
83
Pourmand
G.
Ziaee
A.A.
Abedi
A.R.
Mehrsai
A.
Alavi
H.A.
Ahmadi
A.
Saadati
H.R.
Role of PTEN gene in progression of prostate cancer
Urol. J.
2007
, vol. 
4
 (pg. 
95
-
100
)
84
Kumar
A.
Shendure
J.
Nelson
P.S.
Genome interrupted: sequencing of prostate cancer reveals the importance of chromosomal rearrangements
Genome Med.
2011
, vol. 
3
 pg. 
23
 
85
Barbieri
C.E.
Demichelis
F.
Rubin
M.A.
Molecular genetics of prostate cancer: emerging appreciation of genetic complexity
Histopathology
2012
, vol. 
60
 (pg. 
187
-
198
)
86
Boyd
L.K.
Mao
X.
Xue
L.
Lin
D.
Chaplin
T.
Kudahetti
S.C.
Stankiewicz
E.
Yu
Y.
Beltran
L.
Shaw
G.
, et al. 
High-resolution genome-wide copy-number analysis suggests a monoclonal origin of multifocal prostate cancer
Genes Chromosomes Cancer
2012
, vol. 
51
 (pg. 
579
-
589
)
87
Leslie
N.R.
Foti
M.
Non-genomic loss of PTEN function in cancer: not in my genes
Trends Pharmacol. Sci.
2011
, vol. 
32
 (pg. 
131
-
140
)
88
Yoshimoto
M.
Cunha
I.W.
Coudry
R.A.
Fonseca
F.P.
Torres
C.H.
Soares
F.A.
Squire
J.A.
FISH analysis of 107 prostate cancers shows that PTEN genomic deletion is associated with poor clinical outcome
Br. J. Cancer
2007
, vol. 
97
 (pg. 
678
-
685
)
89
Yoshimoto
M.
Cutz
J.C.
Nuin
P.A.
Joshua
A.M.
Bayani
J.
Evans
A.J.
Zielenska
M.
Squire
J.A.
Interphase FISH analysis of PTEN in histologic sections shows genomic deletions in 68% of primary prostate cancer and 23% of high-grade prostatic intra-epithelial neoplasias
Cancer Genet. Cytogenet.
2006
, vol. 
169
 (pg. 
128
-
137
)
90
Sircar
K.
Yoshimoto
M.
Monzon
F.A.
Koumakpayi
I.H.
Katz
R.L.
Khanna
A.
Alvarez
K.
Chen
G.
Darnel
A.D.
Aprikian
A.G.
, et al. 
PTEN genomic deletion is associated with p-Akt and AR signalling in poorer outcome, hormone refractory prostate cancer
J. Pathol.
2009
, vol. 
218
 (pg. 
505
-
513
)
91
Troyer
D.A.
Jamaspishvili
T.
Wei
W.
Feng
Z.
Good
J.
Hawley
S.
Fazli
L.
McKenney
J.K.
Simko
J.
Hurtado-Coll
A.
, et al. 
A multicenter study shows PTEN deletion is strongly associated with seminal vesicle involvement and extracapsular extension in localized prostate cancer
Prostate
2015
, vol. 
75
 (pg. 
1206
-
1215
)
92
Yoshimoto
M.
Ludkovski
O.
DeGrace
D.
Williams
J.L.
Evans
A.
Sircar
K.
Bismar
T.A.
Nuin
P.
Squire
J.A.
PTEN genomic deletions that characterize aggressive prostate cancer originate close to segmental duplications
Genes Chromosomes Cancer
2012
, vol. 
51
 (pg. 
149
-
160
)
93
Choucair
K.
Ejdelman
J.
Brimo
F.
Aprikian
A.
Chevalier
S.
Lapointe
J.
PTEN genomic deletion predicts prostate cancer recurrence and is associated with low AR expression and transcriptional activity
BMC Cancer
2012
, vol. 
12
 pg. 
543
 
94
Wang
Y.
Dai
B.
PTEN genomic deletion defines favorable prognostic biomarkers in localized prostate cancer: a systematic review and meta-analysis
Int. J. Clin. Exp. Med.
2015
, vol. 
8
 (pg. 
5430
-
5437
)
95
Carvalho
K.C.
Maia
B.M.
Omae
S.V.
Rocha
A.A.
Covizzi
L.P.
Vassallo
J.
Rocha
R.M.
Soares
F.A.
Best practice for PTEN gene and protein assessment in anatomic pathology
Acta Histochem.
2014
, vol. 
116
 (pg. 
25
-
31
)
96
Hocking
C.
Hardingham
J.E.
Broadbridge
V.
Wrin
J.
Townsend
A.R.
Tebbutt
N.
Cooper
J.
Ruszkiewicz
A.
Lee
C.
Price
T.J.
Can we accurately report PTEN status in advanced colorectal cancer?
BMC Cancer
2014
, vol. 
14
 pg. 
128
 
97
Lotan
T.L.
Wei
W.
Ludkovski
O.
Morais
C.L.
Guedes
L.B.
Jamaspishvili
T.
Lopez
K.
Hawley
S.T.
Feng
Z.
Fazli
L.
, et al. 
Analytic validation of a clinical-grade PTEN immunohistochemistry assay in prostate cancer by comparison with PTEN FISH
Mod. Pathol.
2016
, vol. 
29
 (pg. 
904
-
914
)
98
Pallares
J.
Bussaglia
E.
Martinez-Guitarte
J.L.
Dolcet
X.
Llobet
D.
Rue
M.
Sanchez-Verde
L.
Palacios
J.
Prat
J.
Matias-Guiu
X.
Immunohistochemical analysis of PTEN in endometrial carcinoma: a tissue microarray study with a comparison of four commercial antibodies in correlation with molecular abnormalities
Mod. Pathol.
2005
, vol. 
18
 (pg. 
719
-
727
)
99
Cuzick
J.
Yang
Z.H.
Fisher
G.
Tikishvili
E.
Stone
S.
Lanchbury
J.S.
Camacho
N.
Merson
S.
Brewer
D.
Cooper
C.S.
, et al. 
Prognostic value of PTEN loss in men with conservatively managed localised prostate cancer
Br. J. Cancer
2013
, vol. 
108
 (pg. 
2582
-
2589
)
100
Halvorsen
O.J.
Haukaas
S.A.
Akslen
L.A.
Combined loss of PTEN and p27 expression is associated with tumor cell proliferation by Ki-67 and increased risk of recurrent disease in localized prostate cancer
Clin. Cancer Res.
2003
, vol. 
9
 (pg. 
1474
-
1479
)
101
Leinonen
K.A.
Saramaki
O.R.
Furusato
B.
Kimura
T.
Takahashi
H.
Egawa
S.
Suzuki
H.
Keiger
K.
Ho Hahm
S.
Isaacs
W.B.
, et al. 
Loss of PTEN is associated with aggressive behavior in ERG-positive prostate cancer
Cancer Epidemiol. Biomarkers Prev.
2013
, vol. 
22
 (pg. 
2333
-
2344
)
102
Picanco-Albuquerque
C.G.
Morais
C.L.
Carvalho
F.L.
Peskoe
S.B.
Hicks
J.L.
Ludkovski
O.
Vidotto
T.
Fedor
H.
Humphreys
E.
Han
M.
, et al. 
In prostate cancer needle biopsies, detections of PTEN loss by fluorescence in situ hybridization (FISH) and by immunohistochemistry (IHC) are concordant and show consistent association with upgrading
Virchows Archiv
2016
, vol. 
468
 (pg. 
607
-
617
)
103
McMenamin
M.E.
Soung
P.
Perera
S.
Kaplan
I.
Loda
M.
Sellers
W.R.
Loss of PTEN expression in paraffin-embedded primary prostate cancer correlates with high Gleason score and advanced stage
Cancer Res.
1999
, vol. 
59
 (pg. 
4291
-
4296
)
104
Shah
R.B.
Bentley
J.
Jeffery
Z.
DeMarzo
A.M.
Heterogeneity of PTEN and ERG expression in prostate cancer on core needle biopsies: implications for cancer risk stratification and biomarker sampling
Hum. Pathol.
2015
, vol. 
46
 (pg. 
698
-
706
)
105
Morais
C.L.
Guedes
L.B.
Hicks
J.
Baras
A.S.
De Marzo
A.M.
Lotan
T.L.
ERG and PTEN status of isolated high-grade PIN occurring in cystoprostatectomy specimens without invasive prostatic adenocarcinoma
Hum. Pathol.
2016
, vol. 
55
 (pg. 
117
-
125
)
106
McCall
P.
Witton
C.J.
Grimsley
S.
Nielsen
K.V.
Edwards
J.
Is PTEN loss associated with clinical outcome measures in human prostate cancer?
Br. J. Cancer
2008
, vol. 
99
 (pg. 
1296
-
1301
)
107
Mithal
P.
Allott
E.
Gerber
L.
Reid
J.
Welbourn
W.
Tikishvili
E.
Park
J.
Younus
A.
Sangale
Z.
Lanchbury
J.S.
, et al. 
PTEN loss in biopsy tissue predicts poor clinical outcomes in prostate cancer
Int. J. Urol.
2014
, vol. 
21
 (pg. 
1209
-
1214
)
108
Ahearn
T.U.
Pettersson
A.
Ebot
E.M.
Gerke
T.
Graff
R.E.
Morais
C.L.
Hicks
J.L.
Wilson
K.M.
Rider
J.R.
Sesso
H.D.
, et al. 
A prospective investigation of PTEN loss and ERG expression in lethal prostate cancer
J. Natl. Cancer Inst.
2016
, vol. 
108
 pg. 
djv346
 
109
Han
B.
Mehra
R.
Lonigro
R.J.
Wang
L.
Suleman
K.
Menon
A.
Palanisamy
N.
Tomlins
S.A.
Chinnaiyan
A.M.
Shah
R.B.
Fluorescence in situ hybridization study shows association of PTEN deletion with ERG rearrangement during prostate cancer progression
Mod. Pathol.
2009
, vol. 
22
 (pg. 
1083
-
1093
)
110
Murphy
S.J.
Karnes
R.J.
Kosari
F.
Castellar
B.E.
Kipp
B.R.
Johnson
S.H.
Terra
S.
Harris
F.R.
Halling
G.C.
Klein
J.L.
, et al. 
Integrated analysis of the genomic instability of PTEN in clinically insignificant and significant prostate cancer
Mod. Pathol.
2016
, vol. 
29
 (pg. 
143
-
156
)
111
Chen
M.
Pratt
C.P.
Zeeman
M.E.
Schultz
N.
Taylor
B.S.
O'Neill
A.
Castillo-Martin
M.
Nowak
D.G.
Naguib
A.
Grace
D.M.
, et al. 
Identification of PHLPP1 as a tumor suppressor reveals the role of feedback activation in PTEN-mutant prostate cancer progression
Cancer Cell
2011
, vol. 
20
 (pg. 
173
-
186
)
112
Reid
A.H.
Attard
G.
Brewer
D.
Miranda
S.
Riisnaes
R.
Clark
J.
Hylands
L.
Merson
S.
Vergis
R.
Jameson
C.
, et al. 
Novel, gross chromosomal alterations involving PTEN cooperate with allelic loss in prostate cancer
Mod. Pathol.
2012
, vol. 
25
 (pg. 
902
-
910
)
113
Uygur
B.
Abramo
K.
Leikina
E.
Vary
C.
Liaw
L.
Wu
W.S.
SLUG is a direct transcriptional repressor of PTEN tumor suppressor
Prostate
2015
, vol. 
75
 (pg. 
907
-
916
)
114
Wang
Y.
Romigh
T.
He
X.
Tan
M.H.
Orloff
M.S.
Silverman
R.H.
Heston
W.D.
Eng
C.
Differential regulation of PTEN expression by androgen receptor in prostate and breast cancers
Oncogene
2011
, vol. 
30
 (pg. 
4327
-
4338
)
115
Khan
S.
Kumagai
T.
Vora
J.
Bose
N.
Sehgal
I.
Koeffler
P.H.
Bose
S.
PTEN promoter is methylated in a proportion of invasive breast cancers
Int. J. Cancer
2004
, vol. 
112
 (pg. 
407
-
410
)
116
Mueller
S.
Phillips
J.
Onar-Thomas
A.
Romero
E.
Zheng
S.
Wiencke
J.K.
McBride
S.M.
Cowdrey
C.
Prados
M.D.
Weiss
W.A.
, et al. 
PTEN promoter methylation and activation of the PI3K/Akt/mTOR pathway in pediatric gliomas and influence on clinical outcome
Neuro Oncol.
2012
, vol. 
14
 (pg. 
1146
-
1152
)
117
Budd
W.T.
Seashols-Williams
S.J.
Clark
G.C.
Weaver
D.
Calvert
V.
Petricoin
E.
Dragoescu
E.A.
O'Hanlon
K.
Zehner
Z.E.
Dual action of miR-125b as a tumor suppressor and oncomiR-22 promotes prostate cancer tumorigenesis
PloS One
2015
, vol. 
10
 pg. 
e0142373
 
118
Du
Z.
Sun
T.
Hacisuleyman
E.
Fei
T.
Wang
X.
Brown
M.
Rinn
J.L.
Lee
M.G.
Chen
Y.
Kantoff
P.W.
, et al. 
Integrative analyses reveal a long noncoding RNA-mediated sponge regulatory network in prostate cancer
Nat. Commun.
2016
, vol. 
7
 pg. 
10982
 
119
Poliseno
L.
Salmena
L.
Riccardi
L.
Fornari
A.
Song
M.S.
Hobbs
R.M.
Sportoletti
P.
Varmeh
S.
Egia
A.
Fedele
G.
, et al. 
Identification of the miR-106b ∼25 microRNA cluster as a proto-oncogenic PTEN-targeting intron that cooperates with its host gene MCM7 in transformation
Sci. Signal.
2010
, vol. 
3
 pg. 
ra29
 
120
Poliseno
L.
Salmena
L.
Zhang
J.
Carver
B.
Haveman
W.J.
Pandolfi
P.P.
A coding-independent function of gene and pseudogene mRNAs regulates tumour biology
Nature
2010
, vol. 
465
 (pg. 
1033
-
1038
)
121
Tay
Y.
Kats
L.
Salmena
L.
Weiss
D.
Tan
S.M.
Ala
U.
Karreth
F.
Poliseno
L.
Provero
P.
Di Cunto
F.
, et al. 
Coding-independent regulation of the tumor suppressor PTEN by competing endogenous mRNAs
Cell
2011
, vol. 
147
 (pg. 
344
-
357
)
122
Salmena
L.
Poliseno
L.
Tay
Y.
Kats
L.
Pandolfi
P.P.
A ceRNA hypothesis: the Rosetta Stone of a hidden RNA language?
Cell
2011
, vol. 
146
 (pg. 
353
-
358
)
123
Saal
L.H.
Johansson
P.
Holm
K.
Gruvberger-Saal
S.K.
She
Q.B.
Maurer
M.
Koujak
S.
Ferrando
A.A.
Malmstrom
P.
Memeo
L.
, et al. 
Poor prognosis in carcinoma is associated with a gene expression signature of aberrant PTEN tumor suppressor pathway activity
Proc. Natl. Acad. Sci. U.S.A.
2007
, vol. 
104
 (pg. 
7564
-
7569
)
124
Salvi
S.
Casadio
V.
Conteduca
V.
Burgio
S.L.
Menna
C.
Bianchi
E.
Rossi
L.
Carretta
E.
Masini
C.
Amadori
D.
, et al. 
Circulating cell-free AR and CYP17A1 copy number variations may associate with outcome of metastatic castration-resistant prostate cancer patients treated with abiraterone
Br. J. Cancer
2015
, vol. 
112
 (pg. 
1717
-
1724
)
125
Xia
Y.
Huang
C.C.
Dittmar
R.
Du
M.
Wang
Y.
Liu
H.
Shenoy
N.
Wang
L.
Kohli
M.
Copy number variations in urine cell free DNA as biomarkers in advanced prostate cancer
Oncotarget
2016
, vol. 
7
 (pg. 
35818
-
35831
)
126
Hieronymus
H.
Schultz
N.
Gopalan
A.
Carver
B.S.
Chang
M.T.
Xiao
Y.
Heguy
A.
Huberman
K.
Bernstein
M.
Assel
M.
, et al. 
Copy number alteration burden predicts prostate cancer relapse
Proc. Natl. Acad. Sci. U.S.A.
2014
, vol. 
111
 (pg. 
11139
-
11144
)
127
Liu
W.
Xie
C.C.
Thomas
C.Y.
Kim
S.T.
Lindberg
J.
Egevad
L.
Wang
Z.
Zhang
Z.
Sun
J.
Sun
J.
, et al. 
Genetic markers associated with early cancer-specific mortality following prostatectomy
Cancer
2013
, vol. 
119
 (pg. 
2405
-
2412
)
128
Irshad
S.
Bansal
M.
Castillo-Martin
M.
Zheng
T.
Aytes
A.
Wenske
S.
Le Magnen
C.
Guarnieri
P.
Sumazin
P.
Benson
M.C.
, et al. 
A molecular signature predictive of indolent prostate cancer
Sci. Transl. Med.
2013
, vol. 
5
 pg. 
202ra122
 
129
Bitting
R.L.
Armstrong
A.J.
Targeting the PI3K/Akt/mTOR pathway in castration-resistant prostate cancer
Endocr.-Relat. Cancer
2013
, vol. 
20
 (pg. 
R83
-
R99
)
130
Wu
J.B.
Chung
L.W.K.
Dey
N.
De
P.
Leyland-Jones
B.
The PI3K-mTOR pathway in prostate cancer: biological significance and therapeutic opportunities
PI3K-mTOR in Cancer and Cancer Therapy
2016
Part II, New York Cham
Springer International Publishing
(pg. 
263
-
289
)
131
Templeton
A.J.
Dutoit
V.
Cathomas
R.
Rothermundt
C.
Bartschi
D.
Droge
C.
Gautschi
O.
Borner
M.
Fechter
E.
Stenner
F.
, et al. 
Phase 2 trial of single-agent everolimus in chemotherapy-naive patients with castration-resistant prostate cancer (SAKK 08/08)
Eur. Urol.
2013
, vol. 
64
 (pg. 
150
-
158
)
132
Mateo
J.
Carreira
S.
Sandhu
S.
Miranda
S.
Mossop
H.
Perez-Lopez
R.
Nava Rodrigues
D.
Robinson
D.
Omlin
A.
Tunariu
N.
, et al. 
DNA-repair defects and olaparib in metastatic prostate cancer
N. Engl. J. Med.
2015
, vol. 
373
 (pg. 
1697
-
1708
)
133
Marques
R.B.
Aghai
A.
de Ridder
C.M.
Stuurman
D.
Hoeben
S.
Boer
A.
Ellston
R.P.
Barry
S.T.
Davies
B.R.
Trapman
J.
, et al. 
High efficacy of combination therapy using PI3K/AKT inhibitors with androgen deprivation in prostate cancer preclinical models
Eur. Urol.
2015
, vol. 
67
 (pg. 
1177
-
1185
)
134
Toren
P.
Zoubeidi
A.
Targeting the PI3K/Akt pathway in prostate cancer: challenges and opportunities (review)
Int. J. Oncol.
2014
, vol. 
45
 (pg. 
1793
-
1801
)
135
Fine
B.
Hodakoski
C.
Koujak
S.
Su
T.
Saal
L.H.
Maurer
M.
Hopkins
B.
Keniry
M.
Sulis
M.L.
Mense
S.
, et al. 
Activation of the PI3K pathway in cancer through inhibition of PTEN by exchange factor P-REX2a
Science
2009
, vol. 
325
 (pg. 
1261
-
1265
)
136
Kunnev
D.
Ivanov
I.
Ionov
Y.
Par-3 partitioning defective 3 homolog (C. elegans) and androgen-induced prostate proliferative shutoff associated protein genes are mutationally inactivated in prostate cancer cells
BMC Cancer
2009
, vol. 
9
 pg. 
318
 
137
Freeman
D.J.
Li
A.G.
Wei
G.
Li
H.H.
Kertesz
N.
Lesche
R.
Whale
A.D.
Martinez-Diaz
H.
Rozengurt
N.
Cardiff
R.D.
, et al. 
PTEN tumor suppressor regulates p53 protein levels and activity through phosphatase-dependent and -independent mechanisms
Cancer Cell
2003
, vol. 
3
 (pg. 
117
-
130
)
138
Lu
Y.
Yu
Q.
Liu
J.H.
Zhang
J.
Wang
H.
Koul
D.
McMurray
J.S.
Fang
X.
Yung
W.K.
Siminovitch
K.A.
, et al. 
Src family protein-tyrosine kinases alter the function of PTEN to regulate phosphatidylinositol 3-kinase/AKT cascades
J. Biol. Chem.
2003
, vol. 
278
 (pg. 
40057
-
40066
)
139
Vogelmann
R.
Nguyen-Tat
M.D.
Giehl
K.
Adler
G.
Wedlich
D.
Menke
A.
TGFbeta-induced downregulation of E-cadherin-based cell-cell adhesion depends on PI3-kinase and PTEN
J. Cell Sci.
2005
, vol. 
118
 (pg. 
4901
-
4912
)
140
Hodgson
M.C.
Shao
L.J.
Frolov
A.
Li
R.
Peterson
L.E.
Ayala
G.
Ittmann
M.M.
Weigel
N.L.
Agoulnik
I.U.
Decreased expression and androgen regulation of the tumor suppressor gene INPP4B in prostate cancer
Cancer Res.
2011
, vol. 
71
 (pg. 
572
-
582
)
141
Lee
S.H.
Johnson
D.
Luong
R.
Sun
Z.
Crosstalking between androgen and PI3K/AKT signaling pathways in prostate cancer cells
J. Biol. Chem.
2015
, vol. 
290
 (pg. 
2759
-
2768
)
142
Mulholland
D.J.
Tran
L.M.
Li
Y.
Cai
H.
Morim
A.
Wang
S.
Plaisier
S.
Garraway
I.P.
Huang
J.
Graeber
T.G.
, et al. 
Cell autonomous role of PTEN in regulating castration-resistant prostate cancer growth
Cancer Cell
2011
, vol. 
19
 (pg. 
792
-
804
)
143
Krohn
A.
Freudenthaler
F.
Harasimowicz
S.
Kluth
M.
Fuchs
S.
Burkhardt
L.
Stahl
P.
M
C.T.
Bauer
M.
Tennstedt
P.
, et al. 
Heterogeneity and chronology of PTEN deletion and ERG fusion in prostate cancer
Mod. Pathol.
2014
, vol. 
27
 (pg. 
1612
-
1620
)
144
Verhagen
P.C.
van Duijn
P.W.
Hermans
K.G.
Looijenga
L.H.
van Gurp
R.J.
Stoop
H.
van der Kwast
T.H.
Trapman
J.
The PTEN gene in locally progressive prostate cancer is preferentially inactivated by bi-allelic gene deletion
J. Pathol.
2006
, vol. 
208
 (pg. 
699
-
707
)
145
Reid
A.H.
Attard
G.
Ambroisine
L.
Fisher
G.
Kovacs
G.
Brewer
D.
Clark
J.
Flohr
P.
Edwards
S.
Berney
D.M.
, et al. 
Molecular characterisation of ERG, ETV1 and PTEN gene loci identifies patients at low and high risk of death from prostate cancer
Br. J. Cancer
2010
, vol. 
102
 (pg. 
678
-
684
)
146
Bismar
T.A.
Yoshimoto
M.
Duan
Q.
Liu
S.
Sircar
K.
Squire
J.A.
Interactions and relationships of PTEN, ERG, SPINK1 and AR in castration-resistant prostate cancer
Histopathology
2012
, vol. 
60
 (pg. 
645
-
652
)
147
Krohn
A.
Diedler
T.
Burkhardt
L.
Mayer
P.S.
De Silva
C.
Meyer-Kornblum
M.
Kotschau
D.
Tennstedt
P.
Huang
J.
Gerhauser
C.
, et al. 
Genomic deletion of PTEN is associated with tumor progression and early PSA recurrence in ERG fusion-positive and fusion-negative prostate cancer
Am. J. Pathol.
2012
, vol. 
181
 (pg. 
401
-
412
)
148
Zhong
Q.
Ruschoff
J.H.
Guo
T.
Gabrani
M.
Schuffler
P.J.
Rechsteiner
M.
Liu
Y.
Fuchs
T.J.
Rupp
N.J.
Fankhauser
C.
, et al. 
Image-based computational quantification and visualization of genetic alterations and tumour heterogeneity
Sci. Rep.
2016
, vol. 
6
 pg. 
24146
 
149
Weischenfeldt
J.
Simon
R.
Feuerbach
L.
Schlangen
K.
Weichenhan
D.
Minner
S.
Wuttig
D.
Warnatz
H.J.
Stehr
H.
Rausch
T.
, et al. 
Integrative genomic analyses reveal an androgen-driven somatic alteration landscape in early-onset prostate cancer
Cancer Cell
2013
, vol. 
23
 (pg. 
159
-
170
)
150
Yoshimoto
M.
Ding
K.
Sweet
J.M.
Ludkovski
O.
Trottier
G.
Song
K.S.
Joshua
A.M.
Fleshner
N.E.
Squire
J.A.
Evans
A.J.
PTEN losses exhibit heterogeneity in multifocal prostatic adenocarcinoma and are associated with higher Gleason grade
Mod. Pathol.
2013
, vol. 
26
 (pg. 
435
-
447
)
151
Fenic
I.
Franke
F.
Failing
K.
Steger
K.
Woenckhaus
J.
Expression of PTEN in malignant and non-malignant human prostate tissues: comparison with p27 protein expression
J. Pathol.
2004
, vol. 
203
 (pg. 
559
-
566
)
152
Bertram
J.
Peacock
J.W.
Fazli
L.
Mui
A.L.
Chung
S.W.
Cox
M.E.
Monia
B.
Gleave
M.E.
Ong
C.J.
Loss of PTEN is associated with progression to androgen independence
Prostate
2006
, vol. 
66
 (pg. 
895
-
902
)
153
Bedolla
R.
Prihoda
T.J.
Kreisberg
J.I.
Malik
S.N.
Krishnegowda
N.K.
Troyer
D.A.
Ghosh
P.M.
Determining risk of biochemical recurrence in prostate cancer by immunohistochemical detection of PTEN expression and Akt activation
Clin. Cancer Res.
2007
, vol. 
13
 (pg. 
3860
-
3867
)
154
Chaux
A.
Peskoe
S.B.
Gonzalez-Roibon
N.
Schultz
L.
Albadine
R.
Hicks
J.
De Marzo
A.M.
Platz
E.A.
Netto
G.J.
Loss of PTEN expression is associated with increased risk of recurrence after prostatectomy for clinically localized prostate cancer
Mod. Pathol.
2012
, vol. 
25
 (pg. 
1543
-
1549
)
155
Dreher
T.
Zentgraf
H.
Abel
U.
Kappeler
A.
Michel
M.S.
Bleyl
U.
Grobholz
R.
Reduction of PTEN and p27kip1 expression correlates with tumor grade in prostate cancer. Analysis in radical prostatectomy specimens and needle biopsies
Virchows Archiv
2004
, vol. 
444
 (pg. 
509
-
517
)
156
Antonarakis
E.S.
Keizman
D.
Zhang
Z.
Gurel
B.
Lotan
T.L.
Hicks
J.L.
Fedor
H.L.
Carducci
M.A.
De Marzo
A.M.
Eisenberger
M.A.
An immunohistochemical signature comprising PTEN, MYC, and Ki67 predicts progression in prostate cancer patients receiving adjuvant docetaxel after prostatectomy
Cancer
2012
, vol. 
118
 (pg. 
6063
-
6071
)
157
Dong
J.T.
Li
C.L.
Sipe
T.W.
Frierson
H.F.
Jr
Mutations of PTEN/MMAC1 in primary prostate cancers from Chinese patients
Clin. Cancer Res.
2001
, vol. 
7
 (pg. 
304
-
308
)
158
Schmitz
M.
Grignard
G.
Margue
C.
Dippel
W.
Capesius
C.
Mossong
J.
Nathan
M.
Giacchi
S.
Scheiden
R.
Kieffer
N.
Complete loss of PTEN expression as a possible early prognostic marker for prostate cancer metastasis
Int. J. Cancer
2007
, vol. 
120
 (pg. 
1284
-
1292
)
159
Beltran
H.
Prandi
D.
Mosquera
J.M.
Benelli
M.
Puca
L.
Cyrta
J.
Marotz
C.
Giannopoulou
E.
Chakravarthi
B.V.
Varambally
S.
, et al. 
Divergent clonal evolution of castration-resistant neuroendocrine prostate cancer
Nat. Med.
2016
, vol. 
22
 (pg. 
298
-
305
)
160
Wang
S.I.
Parsons
R.
Ittmann
M.
Homozygous deletion of the PTEN tumor suppressor gene in a subset of prostate adenocarcinomas
Clin. Cancer Res.
1998
, vol. 
4
 (pg. 
811
-
815
)
161
Suzuki
H.
Freije
D.
Nusskern
D.R.
Okami
K.
Cairns
P.
Sidransky
D.
Isaacs
W.B.
Bova
G.S.
Interfocal heterogeneity of PTEN/MMAC1 gene alterations in multiple metastatic prostate cancer tissues
Cancer Res.
1998
, vol. 
58
 (pg. 
204
-
209
)
162
Dong
J.T.
Sipe
T.W.
Hyytinen
E.R.
Li
C.L.
Heise
C.
McClintock
D.E.
Grant
C.D.
Chung
L.W.
Frierson
H.F.
Jr
PTEN/MMAC1 is infrequently mutated in pT2 and pT3 carcinomas of the prostate
Oncogene
1998
, vol. 
17
 (pg. 
1979
-
1982
)
163
Barbieri
C.E.
Baca
S.C.
Lawrence
M.S.
Demichelis
F.
Blattner
M.
Theurillat
J.P.
White
T.A.
Stojanov
P.
Van Allen
E.
Stransky
N.
, et al. 
Exome sequencing identifies recurrent SPOP, FOXA1 and MED12 mutations in prostate cancer
Nat. Genet.
2012
, vol. 
44
 (pg. 
685
-
689
)
164
Lapointe
J.
Li
C.
Giacomini
C.P.
Salari
K.
Huang
S.
Wang
P.
Ferrari
M.
Hernandez-Boussard
T.
Brooks
J.D.
Pollack
J.R.
Genomic profiling reveals alternative genetic pathways of prostate tumorigenesis
Cancer Res.
2007
, vol. 
67
 (pg. 
8504
-
8510
)
165
Muller
M.
Rink
K.
Krause
H.
Miller
K.
PTEN/MMAC1 mutations in prostate cancer
Prostate Cancer Prostatic Dis.
2000
, vol. 
3
 pg. 
S32
 
166
Forbes
S.A.
Beare
D.
Gunasekaran
P.
Leung
K.
Bindal
N.
Boutselakis
H.
Ding
M.
Bamford
S.
Cole
C.
Ward
S.
, et al. 
COSMIC: exploring the world's knowledge of somatic mutations in human cancer
Nucleic Acids Res.
2015
, vol. 
43
 (pg. 
D805
-
D811
)