Abstract

Purpose: Cervical cancer (CC) is one of the most general gynecological malignancies and is associated with high morbidity and mortality. We aimed to select candidate genes related to the diagnosis and prognosis of CC.

Methods: The mRNA expression profile datasets were downloaded. We also downloaded RNA-sequencing gene expression data and related clinical materials from TCGA, which included 307 CC samples and 3 normal samples. Differentially expressed genes (DEGs) were obtained by R software. GO function analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of DEGs were performed in the DAVID dataset. Using machine learning, the optimal diagnostic mRNA biomarkers for CC were identified. We used qRT-PCR and Human Protein Atlas (HPA) database to exhibit the differences in gene and protein levels of candidate genes.

Results: A total of 313 DEGs were screened from the microarray expression profile datasets. DNA methyltransferase 1 (DNMT1), Chromatin Assembly Factor 1, subunit B (CHAF1B), Chromatin Assembly Factor 1, subunit A (CHAF1A), MCM2, CDKN2A were identified as optimal diagnostic mRNA biomarkers for CC. Additionally, the GEPIA database showed that the DNMT1, CHAF1B, CHAF1A, MCM2 and CDKN2A were associated with the poor survival of CC patients. HPA database and qRT-PCR confirmed that these genes were highly expressed in CC tissues.

Conclusion: The present study identified five DEmRNAs, including DNMT1, CHAF1B, CHAF1A, MCM2 and Kinetochore-related protein 1 (KNTC1), as potential diagnostic and prognostic biomarkers of CC.

Introduction

Cervical cancer (CC) is one of the most common gynecological malignant tumors worldwide and has become a prominent public health issue [1,2]. According to reports, the incidence of CC ranks second among female malignant tumors in the world, and the mortality rate ranks first among female malignant tumors of the reproductive system. It is a serious threat to women’s health [3]. CC is difficult to diagnose at the early stage, leading to a delay in effective treatment [4]. At present, surgery, chemotherapy and radiotherapy are the most commonly used treatment methods for CC; however, due to the resistance of CC cells to therapeutic drugs, chemotherapy drugs are relatively ineffective in treating CC [5,6]. Therefore, it is of great significance to develop new diagnostic or treatment methods for CC.

Gene Expression Omnibus (GEO) was launched in response to the growing demand for public repositories of high-throughput gene expression data [7]. The Cancer Genome Atlas (TCGA) project analyzes DNA copy number, mRNA expression, promoter methylation, microRNA expression of 307 cervical SCCs, and 3 normal cervical tissue samples [8,9]. Therefore, combining the GEO and TCGA datasets may provide an important perspective for the study of new biomarkers. In fact, there are many reports that revealed a series of highly specific and sensitive markers by screening for tumor biomarkers based on GEO and TCGA data recently [10]. Compared with conventional screening methods, analyzing high-throughput data based on bioinformatics methods allows researchers to obtain stable and reliable biomarkers in a larger number of clinical samples.

In the present study, we downloaded five original mRNA microarray datasets from the GEO database, GSE7410, GSE7803, GSE9750, GSE55940 and GSE63514, a total of 176 samples containing 68 normal cervical samples and 108 CC specimens. We also downloaded RNA-sequencing gene expression data and related clinical materials from TCGA, which included 307 CC samples and 3 normal samples. The differentially expressed genes (DEGs) in normal tissues and tumor samples were obtained by R software. By evaluating the diagnostic and prognostic value of these DEGs, five DEGs associated with the diagnostic and prognosis of CC were screened out.

Materials and methods

Microarray data

Using the keywords ‘cervical cancer’ to search on the GEO database, the raw gene expression profiles of GSE7410, GSE7803, GSE9750, GSE55940 and GSE63514 were downloaded. RNA-sequencing gene expression data and related clinical materials from TCGA were retrieved on 24 March 2020, and comprised data from 307 CC samples and 3 normal samples. The inclusion criteria were pathologically confirmed CC, complete RNA expression data from the patients [11].

Identification of DEGs and functional enrichment analysis

Data analysis was conducted using package limma in R language (version 3.4.0) [12]. FDR < 0.01 and |Combined.ES| > 1.5 were set up to screen DEGs. Heat maps were generated by pheatmap package in R. Through the DAVID database [13], functional enrichment analysis was conducted to identify gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG). GO terms and KEGG pathways with P<0.05 were selected.

Identification of optimal diagnostic mRNA biomarkers for CC

Modeling and machine learning algorithm were used to identify optimal diagnostic mRNA biomarkers for CC. The procedure was performed as previously described [14]. ROC curve was used to explore the differentially diagnostic capability of the five candidate genes.

Identification of survival-related DEGs and establishment of the prognostic gene signature

Using the survival and survminer package in R, Kaplan–Meier (KM) plots and log-rank tests were performed to elucidate the relationship between 5-year overall survival (OS) rates and DEGs expression levels. DEGs with P<0.01 were considered statistically significant and included in subsequent analyses. For these prognostic genes, LASSO Cox regression analysis was used to determine the gene signature prognostic model using the following formula to calculate the risk score for each sample. riskScore=i=1nexpi×βi. Patients with CC were divided into high-risk and low-risk groups based on the median risk score, and KM survival analysis was performed between the low-risk and high-risk groups. ROC curve analysis to evaluate the predictive power of the forecasting model.

Quantitative RT-PCR confirmation and validation in datasets

According to the results of GEO integrated analysis, we selected six DEGs (DNA methyltransferase 1 (DNMT1), Chromatin Assembly Factor 1, subunit B (CHAF1B), Chromatin Assembly Factor 1, subunit A (CHAF1A), MCM2, CDKN2A, Kinetochore-related protein 1 (KNTC1)) in CC versus normal control as candidate genes. A total of 13 blood samples were collected from 7 normal subjects and 6 patients diagnosed with CC. Informed written consent was obtained from all participants, and research protocols were approved by the Ethics Committee of our hospital.

To evaluate mRNA expression of candidate genes, we used GEO database and TCGA database to differentiate expression of candidate genes in CC tissues and normal tissues.

Evaluation of immunohistochemical staining

To validate the protein expression level of candidate genes in CC tissues, we used Human Protein Atlas (HPA, https://www.proteinatlas.org/) database to obtain immunohistochemical staining.

Relationship between candidate genes and clinical features in hepatocellular carcinoma patients

To further explore the relationship between candidate genes and tumor clinical features, we analyzed the TCGA clinical data using LinkedOmics (http://www.linkedomics.org/) database.

Results

Identification of DEGs in CC

After retrieving, we obtained five microarray datasets of mRNA according to the inclusion criteria from the GEO database. The characteristics of the individual database for the integrated analysis are displayed in Table 1. A total of 313 DEGs were obtained, including 200 up-regulated and 113 down-regulated genes. The cluster heatmap of top 100 DEGs in all samples are shown in Figure 1.

Hierarchical clustering analysis of top 100 DEGs in CC based on GEO (fold change > 2.0, P<0.05 in t test)

Figure 1
Hierarchical clustering analysis of top 100 DEGs in CC based on GEO (fold change > 2.0, P<0.05 in t test)
Figure 1
Hierarchical clustering analysis of top 100 DEGs in CC based on GEO (fold change > 2.0, P<0.05 in t test)
Table 1
Details for GEO CC data
GEO IDSamples (Normal:CC)TypePlatformYearAuthorType
GSE7410 5:21 mRNA GPL1708 2008 Biewenga Tissue 
GSE7803 10:21 mRNA GPL96 2007 Zhai Tissue 
GSE9750 24:33 mRNA GPL96 2008 Murty Tissue 
GSE55940 5:5 mRNA GPL16238 2014 Ye Tissue 
GSE63514 24:28 mRNA GPL570 2015 den Boon Tissue 
GEO IDSamples (Normal:CC)TypePlatformYearAuthorType
GSE7410 5:21 mRNA GPL1708 2008 Biewenga Tissue 
GSE7803 10:21 mRNA GPL96 2007 Zhai Tissue 
GSE9750 24:33 mRNA GPL96 2008 Murty Tissue 
GSE55940 5:5 mRNA GPL16238 2014 Ye Tissue 
GSE63514 24:28 mRNA GPL570 2015 den Boon Tissue 

GO and KEGG pathway analysis of DEGs

GO analysis showed that DEGs were most enriched in cell cycle, chromosome, specific DNA binding, and single-stranded DNA binding. GO functional enrichment of DEGs with a P-value <0.05 was considered statistically significant and the results are presented in Figure 2A. KEGG pathway analysis showed that integrated DEGs were mainly enriched in four pathways consisted of cell cycle, DNA replication, p53 signaling pathway and mismatch repair (Figure 2B).

Enrichment analysis of GO and KEGG pathway of DEGs in CC

Figure 2
Enrichment analysis of GO and KEGG pathway of DEGs in CC

(A) GO enrichment analysis (B) KEGG enrichment analysis.

Figure 2
Enrichment analysis of GO and KEGG pathway of DEGs in CC

(A) GO enrichment analysis (B) KEGG enrichment analysis.

Identification of the optimal diagnostic mRNA biomarkers for CC

Based on the reduced dimension of the data, comparing CC and normal tissues identified 20 DEGs using LASSO algorithm analysis (Table 2). The random forest analysis was used to rank the 20 DEGs, according to the decrease in mean accuracy (Figure 3A). A ten-fold cross-validation result demonstrated that the average accuracy rate of ten DEGs, including DNMT1, CHAF1B, CHAF1A, MCM2, CDKN2A, KNTC1, CRISP2, KRT32, SLC5A1 and CRNN exhibited the highest score (Figure 3B). Therefore, these ten DEGs were selected as the potential optimal diagnostic mRNA biomarkers for CC and were used to establish the random forests, decision tree and SVM models.

Identification of mRNA biomarkers for CC

Figure 3
Identification of mRNA biomarkers for CC

(A) Importance value of each DEGs ranked according to the mean decrease in accuracy by using the random forest analysis. (B) Variance rate of classification performance when increasing numbers of the predictive DEGs.

Figure 3
Identification of mRNA biomarkers for CC

(A) Importance value of each DEGs ranked according to the mean decrease in accuracy by using the random forest analysis. (B) Variance rate of classification performance when increasing numbers of the predictive DEGs.

Table 2
Twenty mRNAs screened by LASSO
IDSymbolCombined.ESP.ValueFDRUpDown
1029 CDKN2A 3.491349 Up 
1786 DNMT1 2.594474 Up 
2263 FGFR2 −1.54865 Down 
3882 KRT32 −1.73084 Down 
4171 MCM2 3.044853 Up 
6523 SLC5A1 −2.23921 Down 
6691 SPINK2 −1.80647 Down 
7180 CRISP2 −1.97518 Down 
8208 CHAF1B 2.189046 Up 
8424 BBOX1 −2.53337 Down 
9735 KNTC1 3.197516 Up 
9796 PHYHIP −2.30627 Down 
10036 CHAF1A 2.314881 Up 
10321 CRISP3 −3.04948 Down 
10947 AP3M2 1.72574 Up 
23225 NUP210 2.369988 Up 
49860 CRNN −3.22716 Down 
64786 TBC1D15 1.697909 Up 
65982 ZSCAN18 −2.0272 Down 
79875 THSD4 −2.47196 Down 
IDSymbolCombined.ESP.ValueFDRUpDown
1029 CDKN2A 3.491349 Up 
1786 DNMT1 2.594474 Up 
2263 FGFR2 −1.54865 Down 
3882 KRT32 −1.73084 Down 
4171 MCM2 3.044853 Up 
6523 SLC5A1 −2.23921 Down 
6691 SPINK2 −1.80647 Down 
7180 CRISP2 −1.97518 Down 
8208 CHAF1B 2.189046 Up 
8424 BBOX1 −2.53337 Down 
9735 KNTC1 3.197516 Up 
9796 PHYHIP −2.30627 Down 
10036 CHAF1A 2.314881 Up 
10321 CRISP3 −3.04948 Down 
10947 AP3M2 1.72574 Up 
23225 NUP210 2.369988 Up 
49860 CRNN −3.22716 Down 
64786 TBC1D15 1.697909 Up 
65982 ZSCAN18 −2.0272 Down 
79875 THSD4 −2.47196 Down 

The area under the ROC curve (AUC) of the random forests model was 0.996 and the specificity and sensitivity of this model were 0.941 and 0.991, respectively (Figure 4A). The AUC of the decision tree model was 0.931 and the specificity and sensitivity of this model were 0.897 and 0.972, respectively (Figure 4B). The AUC of the SVM model was 0.995, and the specificity and sensitivity of this model were 0.956 and 0.981 (Figure 4C). The AUC curves of these ten genes were shown in Figure 5, indicating strong diagnostic ability for CC.

ROC analysis of five CC-specific mRNA biomarkers

Figure 4
ROC analysis of five CC-specific mRNA biomarkers

The ROC results of these five diagnostic mRNA biomarkers (DNMT1, CHAF1B, CHAF1A, MCM2 and CDKN2A) based on (A) support random forest, (B) decision tree model and (C) support vector machine model.

Figure 4
ROC analysis of five CC-specific mRNA biomarkers

The ROC results of these five diagnostic mRNA biomarkers (DNMT1, CHAF1B, CHAF1A, MCM2 and CDKN2A) based on (A) support random forest, (B) decision tree model and (C) support vector machine model.

ROC curves of DNMT1, CHAF1B, CHAF1A, MCM2, KNTC1, CRISP2, CRNN, KRT32, SLC5A1 and CDKN2A

Figure 5
ROC curves of DNMT1, CHAF1B, CHAF1A, MCM2, KNTC1, CRISP2, CRNN, KRT32, SLC5A1 and CDKN2A

(A) CHAF1A, (B) CHAF1B, (C) DNMT1, (D) CRISP2, (E) KRT32. (F) MCM2, (G) KNTC1, (H) CDKN2A, (I) CRNN, (J) SLC5A1.

Figure 5
ROC curves of DNMT1, CHAF1B, CHAF1A, MCM2, KNTC1, CRISP2, CRNN, KRT32, SLC5A1 and CDKN2A

(A) CHAF1A, (B) CHAF1B, (C) DNMT1, (D) CRISP2, (E) KRT32. (F) MCM2, (G) KNTC1, (H) CDKN2A, (I) CRNN, (J) SLC5A1.

Identification of five DEGs associated with OS and establishment of the four-gene prognostic signature

In Figure 6, to identify the mRNAs which would be potentially associated with OS of CC patients, we evaluated the association between mRNAs expression and patients’ survival using KM curve and Log-rank test. The results showed that these five mRNAs (DNMT1, CHAF1B, CHAF1A, KNTC1, MCM2) were negatively correlated with OS. Five genes were subsequently used to construct a prognostic gene-signature. Finally, four-gene signature prognostic model was established. Time-dependent ROC and KM curve were used to assess the prognostic capacity of the four-gene signature. The AUCs for 1-, 3-, and 5-year OS were 0.617, 0.665, 0.690. Patients in the high-risk group showed significantly poorer OS than patients in the low-risk group (all P<0.001) (Figure 7A–D).

OS validation of CC patients grouped by median cutoffs of DNMT1, CHAF1B, CHAF1A, MCM2 and KNTC1

Figure 6
OS validation of CC patients grouped by median cutoffs of DNMT1, CHAF1B, CHAF1A, MCM2 and KNTC1

(A) CHAF1A, (B) CHAF1B, (C) DNMT1, (D) KNTC1, (E) MCM2.

Figure 6
OS validation of CC patients grouped by median cutoffs of DNMT1, CHAF1B, CHAF1A, MCM2 and KNTC1

(A) CHAF1A, (B) CHAF1B, (C) DNMT1, (D) KNTC1, (E) MCM2.

Time-dependent ROC analysis, risk score analysis, and KM analysis for the four-gene signature in CC

Figure 7
Time-dependent ROC analysis, risk score analysis, and KM analysis for the four-gene signature in CC

(A) LASSO Cox analysis, (B) risk score, (C) KM curve of the four-gene signature. (D) Time-dependent ROC analysis.

Figure 7
Time-dependent ROC analysis, risk score analysis, and KM analysis for the four-gene signature in CC

(A) LASSO Cox analysis, (B) risk score, (C) KM curve of the four-gene signature. (D) Time-dependent ROC analysis.

Correlation between candidate genes and clinical features in CC patients

Downloading the TCGA clinical data in LinkedOmics online tool, we analyzed the relationship between selected genes and clinical features in CC patients. The CHAF1B and KNTC1 in CC patients were significantly correlated with tumor purity. The CHAF1B was also significantly correlated with radiation therapy and MCM2 was significantly correlated with histological type (Table 3).

Table 3
Relationship between selected candidate genes and clinical features in CC
ItemnDNMT1CHAF1BCHAF1AMCM2KNTC1
StatisticP-valueStatisticP-valueStatisticP-valueStatisticP-valueStatisticP-value
years_to_birth (Spearman Correlation) 307 −0.02 0.72 0.04 0.56 0.00 0.98 0.05 0.45 0.01 0.90 
Tumor_purity (Spearman Correlation) 307 0.05 0.37 0.22 0.00 0.04 0.55 0.10 0.10 0.19 0.00 
ethnicity (Wilcox Test) Hispanic or Latino 24 −0.01 0.12 −0.03 0.16 −0.01 0.56 −0.01 0.37 −0.02 0.42 
 not Hispanic or Latino 171           
race (Kruskal–Wallis Test) Asian 20 2.05 0.73 7.74 0.10 1.97 0.74 7.92 0.09 4.21 0.38 
 White 211           
 Black or African American 30           
radiation_therapy (Wilcox Test) Yes 129 −0.01 0.37 −0.02 0.04 −0.03 0.10 −0.02 0.19 −0.01 0.18 
 NO 55           
pathology_T_stage (Kruskal–Wallis Test) T1 141 4.04 0.40 2.43 0.66 2.17 0.70 0.90 0.93 1.68 0.79 
 T2 72           
 T3 21           
 T4 10           
pathology_N_stage (Wilcox Test) N0 135 -0.01 0.41 −0.02 0.37 0.02 0.72 0.00 0.28 −0.01 0.82 
 N1 60           
pathology_M_stage (Wilcox Test) M0 116 0.00 0.30 −0.02 0.41 −0.05 0.07 −0.03 0.74 −0.01 0.99 
 M1 10           
histological_type (Kruskal–Wallis Test) Cervical squamous cell carcinoma 254 1.68 0.89 5.32 0.38 11.32 0.05 26.49 0.00 3.52 0.62 
 Endocervical type of adenocarcinoma 21           
ItemnDNMT1CHAF1BCHAF1AMCM2KNTC1
StatisticP-valueStatisticP-valueStatisticP-valueStatisticP-valueStatisticP-value
years_to_birth (Spearman Correlation) 307 −0.02 0.72 0.04 0.56 0.00 0.98 0.05 0.45 0.01 0.90 
Tumor_purity (Spearman Correlation) 307 0.05 0.37 0.22 0.00 0.04 0.55 0.10 0.10 0.19 0.00 
ethnicity (Wilcox Test) Hispanic or Latino 24 −0.01 0.12 −0.03 0.16 −0.01 0.56 −0.01 0.37 −0.02 0.42 
 not Hispanic or Latino 171           
race (Kruskal–Wallis Test) Asian 20 2.05 0.73 7.74 0.10 1.97 0.74 7.92 0.09 4.21 0.38 
 White 211           
 Black or African American 30           
radiation_therapy (Wilcox Test) Yes 129 −0.01 0.37 −0.02 0.04 −0.03 0.10 −0.02 0.19 −0.01 0.18 
 NO 55           
pathology_T_stage (Kruskal–Wallis Test) T1 141 4.04 0.40 2.43 0.66 2.17 0.70 0.90 0.93 1.68 0.79 
 T2 72           
 T3 21           
 T4 10           
pathology_N_stage (Wilcox Test) N0 135 -0.01 0.41 −0.02 0.37 0.02 0.72 0.00 0.28 −0.01 0.82 
 N1 60           
pathology_M_stage (Wilcox Test) M0 116 0.00 0.30 −0.02 0.41 −0.05 0.07 −0.03 0.74 −0.01 0.99 
 M1 10           
histological_type (Kruskal–Wallis Test) Cervical squamous cell carcinoma 254 1.68 0.89 5.32 0.38 11.32 0.05 26.49 0.00 3.52 0.62 
 Endocervical type of adenocarcinoma 21           

Quantitative RT-PCR confirmation and validation in datasets

To indicate the results of integrated analysis, we selected five mRNAs (DNMT1, CHAF1B, CHAF1A, MCM2, KNTC1 and CDKN2A) in CC versus normal control. Based on the results of quantitative RT-PCR, the expression of DNMT1, CHAF1B, CHAF1A, MCM2, KNTC1 and CDKN2A were all up-regulated, which were consistent with the results of our integrated analysis (Figure 8).

qRT-PCR results of five DEGs (DNMT1, CHAF1B, CHAF1A, MCM2, KNTC1 and CDKN2A) in CC

Figure 8
qRT-PCR results of five DEGs (DNMT1, CHAF1B, CHAF1A, MCM2, KNTC1 and CDKN2A) in CC

*P<0.05, **P<0.01, ***P<0.001.

Figure 8
qRT-PCR results of five DEGs (DNMT1, CHAF1B, CHAF1A, MCM2, KNTC1 and CDKN2A) in CC

*P<0.05, **P<0.01, ***P<0.001.

Using the GEO and TCGA data, we analyzed the expression of the five selected up-regulated genes in CC tissues and normal tissues. The results showed that the DNMT1, CHAF1B, CHAF1A, MCM2 and KNTC1 were highly expressed in CC tissues, and the differences were statistically significant (Figure 9). The immunohistochemical staining is displayed in Figure 10.

Validation of the expression of candidate genes in CC tissues and normal tissues in GEO and TCGA

Figure 9
Validation of the expression of candidate genes in CC tissues and normal tissues in GEO and TCGA

(A) CHAF1A, (B) CHAF1B, (C) DNMT1, (D) KNTC1, (E) MCM2.

*P<0.05, **P<0.01, ***P<0.001.

Figure 9
Validation of the expression of candidate genes in CC tissues and normal tissues in GEO and TCGA

(A) CHAF1A, (B) CHAF1B, (C) DNMT1, (D) KNTC1, (E) MCM2.

*P<0.05, **P<0.01, ***P<0.001.

Immunohistochemical staining of candidate genes in CC tissues and normal tissues in the HPA database

Figure 10
Immunohistochemical staining of candidate genes in CC tissues and normal tissues in the HPA database
Figure 10
Immunohistochemical staining of candidate genes in CC tissues and normal tissues in the HPA database

Discussion

CC is one of the most general malignant tumors in gynecology, and it is also one of the main causes of female cancer deaths [15]. Statistically, 80 percent of patients develop aggressive cancer once diagnosed and the age of diagnosed patients is tardily decreasing [16]. Furthermore, on account of metastasis and recurrence, the incidence and mortality of CC remain high [17]. At the same time, reliable and specific biomarkers for the diagnosis and prognosis of CC are scarce and lack exploration. Thus, it is urgent to find diagnostic biomarkers and new therapeutic targets to predict the survival of CC. Gene expression microarrays have been broadly used in the study of genes related to tumors, offering broad prospects for molecular therapy of drugs [18]. A battery of biomarkers have been suggested as potential targets for the diagnosis and prognosis of CC [19,20].

DNMT1 is a member of the DNA methyltransferase family, responsible for the DNA methylation of cytosine-phosphoguanine (CpG) island upstream of tumor suppressor genes [21,22]. DNMT1 is the most important one. Abnormal expression of DNMT1 can lead to abnormal methylation of some tumor suppressor genes CpG islands, which in turn leads to inactivation of tumor suppressor genes and cell carcinogenesis [23]. Highly expressed DNMT1 is not only detected in a variety of tumor cells, but also appears before DNA methylation [24]. Previous studies have shown that DNMT1 is an essential substance for the maintenance of cancer stem cells (CSCs) in various cancers such as prostate cancer, pancreatic cancer and breast cancer [25–27]. For example, DNMT1 induces histone demethylation of H3K9me3 and H3K27me3 on the promoters of Zeb2 and KLF4 in prostate cancer cells [26]. More importantly, a recent study showed that DNMT1 is up-regulated in breast tumors. DNMT1 inhibition or DNMT1 induced Islet-1 (ISL1) hypermethylation/down-regulation limits the number of CSCs in breast cancer cells [25]. In our study, DNMT1 was up-regulated in CC versus normal control, and may be as an oncogene in development of CC. Furthermore, DNMT1 was significantly associated with OS time and one of the diagnostic markers. Thus, we speculated that the expression level of DNMT1 has both diagnostic and prognostic values.

MCM2 is a component of the DNA replication licensing complex (MCM2-7) that has been found to mainly localize to the nucleus in eukaryotic cells. MCM2 has been recognized as a useful marker in screening for cervical carcinoma oral squamous cell carcinoma and medulloblastoma. Overexpression of MCM2 occurs frequently in CC, especially in cases with persistent high-risk HPV infection [28]. Many studies mainly focus on the analysis of biomarkers related to precancerous lesions, but only a few studies have confirmed the prognostic influence of MCM2 expression in the progression of aggressive CC [29,30]. Wang et al. found that MCM2 was a prognostic biomarker in CC [31]. We also observed high expression levels of MCM2 in CC tissues. Aihemaiti et al. reported that cytoplasmic rather than nuclear accumulation of MCM2 is related to improved survival for patients with ovarian clear cell carcinoma, which maybe associated with MCM2-mediated DNA damage-induced apoptosis [32]. It was therefore hypothesized in the present study that MCM2 may serve an important role in CC. In addition, MCM2 was also correlated with diagnosis and prognosis for CC.

CHAF1A which is also called P150 is the subunit of Chromatin Assembly Factor-1 (CAF-1) [33–37]. CHAF1A enhances Gfi1-mediated transcriptional repression and occupies Gfi1 target gene promoters in transfected cells [38]. Recently, CHAF1A has been associated with the development and progression of solid tumors, including breast cancer, prostate squamous cell carcinoma, hepatocellular carcinoma (HCC), glioma and neuroblastoma [39–43]. A number of studies have shown that CHAF1A is also highly expressed in breast cancer, colon cancer, CC and other tumors, and can be used as a potential marker for judging the prognosis of tumor patients and a target for tumor treatment [44]. However, the expression and biological function of CHAF1A in CC remains largely unidentified.

Chromatin assembly factor 1, subunit B (CHAF1B), the p60 subunit of CAF-1, plays a vital role in DNA replication and chromatin assembly in proliferating tissues [45]. Tumor cells are usually characterized by a high proliferation rate. Therefore, it is speculated that CHAF1B plays an important role in the pathogenesis of malignant tumors. Researches have shown that up-regulated CHAF1B is significantly correlated with poor outcomes and that CHAF1B has potential in predicting the prognosis in several cancers, including CC [46–48]. These reported results were consistent with our study.

KNTC1 gene is distributed in the cytoplasm, nucleus, chromosomal centromere, centromere, cytoskeleton and in the spindle fiber. KNTC1 has been studied in a variety of human malignancies and is related to the pathological grade of tumor tissues [49]. As previously described, the expression of KNTC1 in three esophageal squamous cell carcinoma (ESCC) cell lines and established that all the tested cell lines showed that it is positively expressed [50]. Previous studies have shown that the KNTC1 transcriptional activity changes with the size of tumor in patients with oral squamous cell carcinoma [51]. Also, compared with the healthy control group, the KNTC1 expression in neuroblastoma samples increased statistically. Several bioinformatics studies have also established that the KNTC1 gene could be one of the vital genes associated with cancer development, including HCC, Pancreatic cancer (PC), and nasopharyngeal carcinoma (NPC) [52]. Chen et al. reported that KNTC1 gene is closely related to the poor prognosis of CC, which was consistent with our findings [49].

In conclusion, we obtained several DEGs in CC and found that overexpression of DNMT1, CHAF1B, CHAF1A, MCM2, KNTC1 in tumor tissues predicted poor survival in CC. These DEGs also have diagnostic value for CC at early stage. We hypothesized that DNMT1, CHAF1B, CHAF1A, MCM2 and KNTC1 may be potential therapeutic targets for CC. We analyzed these genes at the transcriptional and protein levels, validated by qRT-PCR and immunohistochemical staining.

Data Availability

The datasets used and/or analyzed during the current study are available from the corresponding authors on reasonable request.

Competing Interests

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

Funding

This work was supported by the Open Project of Key Laboratory of Clinical Laboratory Diagnostics, Ministry of Education (General Examination of Chongqing Medical University [2020] 12); The Hospital Level Project of Third Affiliated Hospital of Chongqing Medical University [grant number KY08028]; and The School Level Project of Chongqing Medical University [grant number CQMUNCP0211].

Author Contribution

H.-Y.H. and K.D. contributed to the conception of the study. J.-T.M. performed the data analyses. W.-P.J. and X.-M.Z. contributed significantly in writing the manuscript. All authors read and approved the final manuscript.

Ethics Approval

The present study has been approved by the Third Hospital Affiliated to Chongqing Medical University.

Consent for Publication

Consent for publication was obtained from all patients.

Abbreviations

     
  • AUC

    area under the ROC curve

  •  
  • CAF-1

    chromatin assembly factor-1

  •  
  • CC

    cervical cancer

  •  
  • CHAF1A

    chromatin assembly factor 1, subunit A

  •  
  • CHAF1B

    chromatin assembly factor 1, subunit B

  •  
  • CpG

    cytosine-phosphoguanine

  •  
  • CSC

    cancer stem cell

  •  
  • DEG

    differentially expressed gene

  •  
  • DNMT1

    DNA methyltransferase 1

  •  
  • FDR

    false discovery rate

  •  
  • GEO

    Gene Expression Omnibus

  •  
  • GEPIA

    Gene Expression Profiling Interactive Analysis

  •  
  • GO

    gene ontology

  •  
  • HCC

    hepatocellular carcinoma

  •  
  • HPV

    Human papillomavirus

  •  
  • KEGG

    Kyoto Encyclopedia of Genes and Genomes

  •  
  • KM

    Kaplan–Meier

  •  
  • KNTC1

    kinetochore-related protein 1

  •  
  • OS

    overall survival

  •  
  • ROC

    Receiver operating characteristic

  •  
  • SCC

    squamous cell carcinoma

  •  
  • SVM

    Support Vector Machine

  •  
  • Zeb2

    Zinc Finger E-Box Binding Homeobox 2

  •  
  • H3K27me3

    tri-methylation at lysine 27 of histone H3

  •  
  • H3K9me3

    tri-methylation of lysine 9 on histone H3

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Author notes

*

These authors contributed equally to this work and should be considered co-first authors.

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