Aberrant methylation of PCDH8 is a potential prognostic biomarker for patients with clear cell renal cell carcinoma

A 9-gene prognostic signature for kidney renal clear cell carcinoma overall survival based on co-expression and regression analyses

This research attempted to screen potential signatures associated with KIRC progression and overall survival by weighted gene co-expression network analysis (WGCNA) and Cox regression. The KIRC-associated mRNA expression and clinical data were accessed from The Cancer Genome Atlas (TCGA) database. Differentially expressed genes (DEGs) were screened by differential analysis. A co-expression network was constructed by "WGCNA". Based on WGCNA module, GO and KEGG analyses were performed. Protein-protein interaction (PPI) network was constructed. Prognostic signatures were screened by Lasso-Cox regression. Prognostic model was evaluated by Receiver Operating Characteristic (ROC) and Kaplan-Meier (K-M) curves. Multivariate Cox and nomogram were introduced to examine whether risk score could be an independent marker. qRT-PCR was introduced to determine expression of 9 hub genes in KIRC clinical tumor tissues and adjacent tissues, respectively. Genes in the green module were highly associated with clinical status, and green module genes were significantly enriched in mitotic nuclear division, cell cycle, and p53 signaling pathway. Twenty-six candidates were subsequently screened out from the green module. Next, a 9-gene prognostic model (DLGAP5, NUF2, TOP2A, RRM2, HJURP, PLK1, AURKB, KIF18A, CCNB2) was constructed. The predicting ability of the model was optimal. Some cancer-related signaling pathways were differently activated between two risk score groups. Additionally, under-expression of some signature genes (AURKB, CCNB2, PLK1, RRM2, TOP2A) was associated with better survival rate for KIRC patients. Meanwhile, all 9 hub genes were substantially overexpressed in KIRC patients. A KIRC prognostic signature was screened in this study, contributing valuable findings to KIRC biomarker development.

DNA methylation-mediated low expression of ZNF582 promotes the proliferation, migration, and invasion of clear cell renal cell carcinoma

OBJECTIVE

The methylation of DNA promoter region mediates the low expression of many tumor suppressor genes and plays an essential part in cancer progression. We investigated methylation and expression of ZNF582 in clear cell renal cell carcinoma (ccRCC), and to study the function of ZNF582 in ccRCC cells.

METHODS

Methylation data and mRNA expression data of TCGA-KIRC were obtained from TCGA database to screen methylation-driven genes. Survival analysis and gene set enrichment analysis (GSEA) were done for the target gene. The methylation degree and mRNA level of ZNF582 in ccRCC cell line were detected by methylation-specific PCR (MSP) and qRT-PCR, respectively. Effects of overexpression of ZNF582 on ccRCC cells were assessed via CCK-8, flow cytometry, wound healing, Transwell, and cell adhesion assays.

RESULTS

Eighteen methylation-driven genes were identified via bioinformatics methods. Among them, ZNF582 was noticeably hypermethylated and lowly expressed in tumor tissue, and ZNF582 methylation and expression levels were pronouncedly associated with prognosis and clinical stage. MSP also displayed that the ZNF582 DNA promoter region was hypermethylated in ccRCC cells, and the mRNA expression of ZNF582 was dramatically elevated after demethylation. In vitro cell experiments disclosed that overexpression of ZNF582 markedly hindered cell proliferation, invasion, migration, and fostered cell apoptosis and adhesion of ccRCC.

CONCLUSION

ZNF582 was hypermethylated in ccRCC, which mediated its low level. Overexpression of ZNF582 inhibited tumor cell proliferation, migration and invasion. This study generates novel ideas for ccRCC diagnosis and treatment.

PCDH20 inhibits esophageal squamous cell carcinoma proliferation and migration by suppression of the mitogen-activated protein kinase 9/AKT/β-catenin pathway

Aberrant protocadherins (PCDHs) expression trigger tumor invasion and metastasis. PCDH20 anti-tumor functions in various tumor have been identified. Tumor suppression is due to Wnt/β-catenin pathway antagonism and may be suppressed caused by PCDH20 downregulation through promotor methylation, whereas PCDH20 effects and regulation mechanism in esophageal squamous cell carcinoma (ESCC) remains elusive. We analyzed PCDH20 effects on ESCC and underlying action mechanisms for PCDH20. We test PCDH20 expression in ESCC tissues and cells by semi-quantitative PCR (RT-PCR) and q-PCR (real-time quantitative polymerase chain reaction). MSP (methylation-specific PCR) was carried out to assess the methylation of PCDH20 in ESCC cells and tissues. Anti-tumor effects of PCDH20 in vitro were assessed by clone formation assay, CCK8 assay, Transwell assay, and flow cytometry. Nude mice tumorigenicity was used to assess PCDH20 anti-tumor effect in vivo. Online database, qPCR, and Western blotting were used to identify the downregulation of MAP3K9 by PCDH20, associated with AKT/β-catenin signaling inactivation. We found that PCDH20 expression was dramatically attenuated in esophageal cancer tissues and cells, maybe due to promotor methylation, and ectopic PCDH20 expression suppressed ESCC malignant biological phenotypes. PCDH20 exerted anti-tumor effects by MAP3K9 downregulation, which suppressed AKT/β-catenin signaling in ESCC cells.

Conclusion

PCDH20 was a tumor suppressor gene, which antagonized AKT/β-catenin signaling pathway in ESCC by decreasing MAP3K9.

Clinical significance of novel DNA methylation biomarkers for renal clear cell carcinoma

OBJECTIVE

Clear cell renal cell carcinoma (ccRCC) is the most common type of kidney tumor characterized by the highest mortality rate of the genitourinary cancers, and, therefore, new diagnostic and/or prognostic biomarkers are urgently needed.

METHODS

Based on genome-wide DNA methylation profiling in 11 pairs of ccRCC and non-cancerous renal tissues (NRT), the methylation at regulatory regions of ZNF677, FBN2, PCDH8, TFAP2B, TAC1, and FLRT2 was analyzed in 168 renal tissues and 307 urine samples using qualitative and quantitative methylation-specific PCR (MSP).

RESULTS

Significantly higher methylation frequencies for all genes were found in ccRCC tissues compared to NRT (33-60% vs. 0-11%). The best diagnostic performance demonstrated a panel of ZNF677, FBN2, PCDH8, TFAP2B & TAC1 with 82% sensitivity and 96% specificity. Hypermethylation of ZNF677 and PCDH8 in the tissue samples was significantly related to numerous adverse clinicopathologic parameters. For the urine-based ccRCC detection, the highest diagnostic power (AUC = 0.78) was observed for a panel of ZNF677 & PCDH8 (with or without FBN2 or FLRT2) with 69-78% sensitivity and 69-80% specificity, albeit with lower values in the validation cohort. Besides, methylation of PCDH8 was significantly related to higher tumor stage and fat invasion in the study and validation cohorts. Moreover, PCDH8 was strongly predictive for OS (HR, 5.7; 95% CI 1.16-28.12), and its prognostic power considerably increased in combination with ZNF677 (HR, 12.5; 95% CI 1.47-105.58).

CONCLUSION

In summary, our study revealed novel, potentially promising DNA methylation biomarkers of ccRCC with the possibility to be applied for non-invasive urine-based ccRCC detection and follow-up.

Effect of Aberrant Long Noncoding RNA on the Prognosis of Clear Cell Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC) is a kind of lethal cancer. Although there are mature treatment methods, there is still a lack of rigorous and scientific means for cancer diagnosis. Long noncoding RNAs (lncRNAs) are a kind of noncoding RNA (ncRNA). Recent studies find that alteration of lncRNA expression is related to the occurrence of many cancers. In order to find lncRNAs which can effectively predict the prognosis of ccRCC, RNA-seq count data and clinical information were downloaded from TCGA-KIRC, and gene expression profiles from 530 patients were included. Then, K-means was used for clustering, and the number of clusters was determined to be 5. The R-package "edgeR" was used to perform differential expression analysis. Subsequently, a risk model composed of 10 lncRNA biomarkers significantly related to prognosis was identified via Cox and LASSO regression analyses. Then, patients were divided into two groups according to the model-based risk score, and then, GSEA pathway enrichment was performed. The results showed that metabolism- and mTOR-related pathways were activated while immune-related pathways were inhibited in the high-risk patients. Combined with previous studies, it is believed that these 10 lncRNAs are potential targets for the treatment of ccRCC. In addition, Cox regression analysis was used to verify the independence of the risk model, and as results revealed, the risk model can be used to independently predict the prognosis of patients. In conclusion, our study found 10 lncRNAs related to the prognosis of ccRCC and provided new ideas for clinical diagnosis and drug development.

The Role of Epigenetics in the Progression of Clear Cell Renal Cell Carcinoma and the Basis for Future Epigenetic Treatments

Simple Summary

The accumulated evidence on the role of epigenetic markers of prognosis in clear cell renal cell carcinoma (ccRCC) is reviewed, as well as state of the art on epigenetic treatments for this malignancy. Several epigenetic markers are likely candidates for clinical use, but still have not passed the test of prospective validation. Development of epigenetic therapies, either alone or in combination with tyrosine-kinase inhibitors of immune-checkpoint inhibitors, are still in their infancy.

Abstract

Clear cell renal cell carcinoma (ccRCC) is curable when diagnosed at an early stage, but when disease is non-confined it is the urologic cancer with worst prognosis. Antiangiogenic treatment and immune checkpoint inhibition therapy constitute a very promising combined therapy for advanced and metastatic disease. Many exploratory studies have identified epigenetic markers based on DNA methylation, histone modification, and ncRNA expression that epigenetically regulate gene expression in ccRCC. Additionally, epigenetic modifiers genes have been proposed as promising biomarkers for ccRCC. We review and discuss the current understanding of how epigenetic changes determine the main molecular pathways of ccRCC initiation and progression, and also its clinical implications. Despite the extensive research performed, candidate epigenetic biomarkers are not used in clinical practice for several reasons. However, the accumulated body of evidence of developing epigenetically-based biomarkers will likely allow the identification of ccRCC at a higher risk of progression. That will facilitate the establishment of firmer therapeutic decisions in a changing landscape and also monitor active surveillance in the aging population. What is more, a better knowledge of the activities of chromatin modifiers may serve to develop new therapeutic opportunities. Interesting clinical trials on epigenetic treatments for ccRCC associated with well established antiangiogenic treatments and immune checkpoint inhibitors are revisited.

Do Protocadherins Show Prognostic Value in the Carcinogenesis of Human Malignant Neoplasms? Systematic Review and Meta-Analysis

Background:

Protocadherins (PCDHs) have been reported as tumor suppressor genes, implying that these genes may be involved in tumor suppression in a variety of cancers. However, a thorough understanding of the functions and mechanisms of PCDHs remains limited. Our aim was to investigate the methylation profile of PCDHs in human malignant neoplasms.

Methods:

This systematic review has been recorded in PROSPERO (#42019117844) and conducted according to PRISMA’s checklist; search was conducted in LILACS, PubMed, Science Direct, Scopus, and Web of Science databases, manually, with search queries and without date or language restrictions.

Results:

We found 91 articles, of which 26 were used for this meta-analysis and categorized according to the origin of the neoplasia. In total, 3,377 cases were compiled, with PCDH10, PCDH17, and PCDH8 being the most studied; males were 2.22 times more affected than females. Studies have shown significant heterogeneity (p <0.001), with the odds ratio varying between cases and controls [2.20 (95% CI = 1.11– 4.35) to 209.05 (95% CI = 12.64– 2,457.18)], and the value of association between methylation and cancers studied was 26.08 (95% CI = 15.42–44.13).

Conclusion:

In this systematic review, we have demonstrated using meta-analysis that PCDHs could emerge as potential tumor suppressor genes and that a significant increase in methylation may be useful for early detection of different cancers. This work may help in the identification of new prognostic biomarkers in malignant neoplasms.

A 13-gene risk score system and a nomogram survival model for predicting the prognosis of clear cell renal cell carcinoma

BACKGROUND

Renal cell carcinoma (RCC) is the second common malignant tumor in the urinary system, and 85% of RCC cases are clear cell RCC (ccRCC). This study is designed to build a risk score system for ccRCC.

METHODS

The gene methylation and expression data of ccRCC samples were downloaded from The Cancer Genome Atlas database (training set) and ArrayExpress database (validation set). The differentially methylated genes (DMGs) and differentially expressed genes (DEGs) were identified by limma package, and their intersecting genes with negative Pearson correlation coefficients were remained using cor.test function. Prognosis-associated genes were identified by survival package, and the optimal DMGs were obtained using penalized package. After risk score system was built, nomogram survival model was constructed using rms package. Additionally, pathways were enriched for the DEGs between high- and low-risk groups using Gene Set Enrichment Analysis.

RESULTS

There were 3,638 DMGs and 2,702 DEGs between tumor and normal samples. Among the 312 intersecting genes, 43 prognosis-associated genes were identified. A total of 13 optimal DMGs (BTBD19, ADAM8, BGLAP, TNFRSF13C, JPH4, BEST1, GNRH2, UBE2QL1, CHODL, GDF9, UPB1, KCNH3; and ADAMTSL4) were obtained for building the risk score system. After pathological M, pathological T, platelet qualitative, and RS status were revealed to be independent prognostic factors, a nomogram survival model was constructed. For the 920 DEGs between the high- and low-risk samples, 6 significant pathways were enriched.

CONCLUSION

The 13-gene risk score system and the nomogram survival model might be used for prognostic prediction of ccRCC patients.

Decreased expression of protocadherin 20 is associated with poor prognosis in hepatocellular carcinoma

Recently, protocadherin 20 has been reported as a tumor suppressor gene in hepatocellular carcinoma (HCC); however, the prognostic value of protocadherin 20 in HCC remains unclear. Hence, the purpose of this study was to investigate the clinical and prognostic values of protocadherin 20 in HCC patients. The expression of protocadherin 20 was assessed by quantitative real-time polymerase chain reaction, western blot, and immunohistochemistry. Kaplan-Meier curves were created to calculate the overall survival of the patients, and Cox regression models were used to identify the risk factors associated with prognosis. Of 317 primary HCC patients, decreased expression of protocadherin 20 was observed in 184 (58.0%) patients (P < 0.001). Reduced protocadherin 20 protein expression correlated with portal hypertension, poor tumor differentiation, advanced Okuda stage, and Cancer of the Liver Italian Program score (all P < 0.05). Low protocadherin 20 expression was an independent risk factor for mortality (P = 0.018). Furthermore, in our newly developed simple risk score based on protocadherin 20, patients with total score > 1.11 showed significantly poorer outcome; and the predictive value of the score was better than the Barcelona Clinic Liver Cancer stage, Okuda stage, and Child-Pugh classification (Harrell's concordance index = 0.614). Taken together, these findings suggest that protocadherin 20 may represent a novel prognostic biomarker for HCC patients.

Protocadherin-8 promotes invasion and metastasis via laminin subunit γ2 in gastric cancer

Growing evidence suggests that protocadherins (PCDH) play crucial roles in pathogenesis and progression of cancers, including gastric cancer (GC). Protocadherin‐8 (PCDH8) was previously reported to be involved in metastasis of GC, but functional studies yielded inconsistent results and the molecular mechanism remained unknown. The present study aimed to explore the clinical relevance, function and molecular mechanism of PCDH8 in GC. Data from the GEPIA and Kaplan–Meier plotter databases showed that high expression of PCDH8 was significantly correlated with poorer prognosis in GC. Ectopic expression of PCDH8 in GC cells promoted invasion and migration in vitro and metastasis in vivo, and knockdown of PCDH8 inhibited invasion and migration in vitro. RNA sequencing followed by gene set enrichment analysis found a remarkable enrichment in the extracellular matrix receptor interaction pathway, with the expression of laminin subunit γ2 (LAMC2) being significantly increased in the PCDH8‐overexpressing group. High expression of LAMC2 was significantly correlated to poor prognosis in GC in GEPIA database. Upregulation of LAMC2 following PCDH8 overexpression was further confirmed by immunohistochemistry in liver metastatic lesions of nude mice. To our knowledge, this is the first report of the metastasis‐enhancing property and molecular mechanism through upregulation of LAMC2 of PCDH8 in cancer. High expression of PCDH8 could be used as a biomarker for poor prognosis in clinical practice.

Retracted Article: Overexpression of PCDH8 inhibits proliferation and invasion, and induces apoptosis in papillary thyroid cancer cells

Protocadherin8 (PCDH8), a member of the protocadherin (PCDH) family, is involved in the progression of several types of cancers. However, the expression and biological roles of PCDH8 in papillary thyroid carcinoma (PTC) remain largely unknown. Therefore, in the present study, we detected the expression of PCDH8 in human PTC tissues and cell lines, and evaluated its role in PTC cells. Our results demonstrated that PCDH8 was lowly expressed in human PTC tissues and cell lines. In addition, ectopic expression of PCDH8 efficiently inhibited the proliferation, migration and invasion of PTC cells, as well as prevented the epithelial-mesenchymal transition (EMT) phenotype in PTC cells. Furthermore, PCDH8 efficiently induced apoptosis and autophagy in PTC cells. Mechanistically, overexpression of PCDH8 significantly prevented the activation of the Wnt/β-catenin pathway in PTC cells. Taken together, these findings showed that overexpression of PCDH8 inhibits proliferation and migration/invasion, and induces apoptosis of PTC cells through the Wnt/β-catenin signaling pathway.

Protocadherin8 (PCDH8), a member of the protocadherin (PCDH) family, is involved in the progression of several types of cancers.

Low expression of protocadherin7 (PCDH7) is a potential prognostic biomarker for primary non-muscle invasive bladder cancer

Bladder cancer is a heterogeneous disease with outcome difficult to predict, and novel predictive biomarkers are needed. PCDH7, a member of protocadherins family, functions as tumor suppressor in several human cancers. The human PCDH7 gene is localized in chromosome 4p15, which is often inactivated in human cancers, including bladder cancer. The aim of this study was to investigate the clinical significance of PCDH7 expression in non-muscle invasive bladder cancer (NMIBC). PCDH7 expression was examined using immunohistochemical staining in 199 primary NMIBC tissues and 25 normal bladder epithelial tissues. Then the relationship between PCDH7 expression and clinicopathologic features was evaluated. Kaplan-Meier survival analysis and Cox analysis was used to evaluate the correlation between PCDH7 expression and prognosis. PCDH7 expression in NMIBC tissues was significantly lower than that in normal bladder epithelial tissues (P < 0.001). Low PCDH7 expression correlated with advanced grade (P = 0.021) and larger tumor size (P = 0.044). Moreover, patients with low PCDH7 expression have shorter recurrence-free survival (P < 0.001), progression-free survival (P = 0.007) and overall survival (P = 0.011) than patients with high PCDH7 expression. Low PCDH7 expression is an independent predictor of recurrence-free survival (multivariate Cox analysis: P = 0.007), progression-free survival (multivariate Cox analysis: P = 0.014) and overall survival (multivariate Cox analysis: P = 0.004). The findings indicate that low PCDH7 expression is a potential prognostic biomarker for primary NMIBC.

Aberrant Promoter Methylation of Protocadherin8 (PCDH8) in Serum is a Potential Prognostic Marker for Low Gleason Score Prostate Cancer

Background

PCDH8 is a newly-discovered suppressor gene that is frequently inactivated by aberrant methylation in several human cancers, including prostate cancer. The identification of PCDH8 methylation can be used as a potential predictive biomarker. Prostate cancer patients with high Gleason score are considered as being at high risk for tumor recurrence and progression, and adjuvant therapy is often routinely performed in clinical practice. In the present study, we did not measure the methylation of PCDH8 in these patients. The main purpose of the present study was to evaluate the clinical significance of PCDH8 methylation in serum of prostate cancer patients with low Gleason score.

Material/Methods

PCDH8 methylation in serum samples of 117 patients and 47 controls was checked by methylation-specific PCR (MSP). Then, we correlated PCDH8 methylation status with the clinicopathological parameters of prostate cancer patients with low Gleason score and patient outcomes.

Results

We found that PCDH8 was more frequently methylated in serum samples of patients with prostate cancer than in controls. PCDH8 methylation was correlated with advanced clinical stage (P=0.021), higher level of preoperative PSA (P=0.008), and positive lymph node metastasis (P=0.010). Moreover, patients with PCDH8 methylation had worse biochemical recurrence (BCR)-free survival (P<0.001) than patients without. Independent prognostic factors for worse BCR-free survival of prostate cancer patients with low Gleason score were: PCDH8 methylation in serum (Exp (B)=3.147, 95% CI: 1.152–7.961, P=0.007), clinical stage (Exp (B)=2.53, 95% CI: 1.032–4.763, P=0.025) and lymph node status (Exp (B)=1.476, 95% CI: 1.107–4.572, P=0.042).

Conclusions

Our study indicated that PCDH8 methylation in serum occurred frequently in prostate cancer patients and was correlated with risk factors for poor outcome. The methylation of PCDH8 in serum is a potential predictive marker for prostate cancer patients with low Gleason score after surgery.

Prognostic DNA methylation markers for renal cell carcinoma: a systematic review

AIM

Despite numerous published prognostic methylation markers for renal cell carcinoma (RCC), none of these have yet changed patient management. Our aim is to systematically review and evaluate the literature on prognostic DNA methylation markers for RCC.

MATERIALS & METHODS

We conducted an exhaustive search of PubMed, EMBASE and MEDLINE up to April 2017 and identified 49 publications. Studies were reviewed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, assessed for their reporting quality using the Reporting Recommendations for Tumor Marker Prognostic Studies (REMARK) criteria, and were graded to determine the level of evidence (LOE) for each biomarker.

RESULTS

We identified promoter methylation of BNC1, SCUBE3, GATA5, SFRP1, GREM1, RASSF1A, PCDH8, LAD1 and NEFH as promising prognostic markers. Extensive methodological heterogeneity across the included studies was observed, which hampers comparability and reproducibility of results, providing a possible explanation why these biomarkers do not reach the clinic.

CONCLUSION

Potential prognostic methylation markers for RCC have been identified, but they require further validation in prospective studies to determine their true clinical value.

Protocadherin 7 inhibits cell migration and invasion through E-cadherin in gastric cancer

The protocadherin 7 is a member of the protocadherin family that expressed aberrantly in many types of human cancers. However, its expression, function, and underlying mechanisms are little known in gastric cancer. In this study, we detected protocadherin 7 expression in gastric cancer tissues and non-tumorous gastric mucosa tissues by real-time quantitative polymerase chain reaction and immunohistochemistry. The association of protocadherin 7 expression with the clinicopathological characteristics and the prognosis was subsequently analyzed. MTS ((3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium)) and transwell assays were performed to assess the effect of protocadherin 7 on proliferation, migration, and invasion in gastric cancer cell lines. Moreover, real-time quantitative polymerase chain reaction and western blot were used to detect the expression of epithelial-mesenchymal transition markers. Protocadherin 7 expression was decreased gradiently from normal tissue to gastric cancer, especially in gastric cancer tissue with lymph node metastasis. Low expression of protocadherin 7 was significantly associated with Lauren's classification ( p = 0.0005), lymph node metastases ( p = 0.0002), and tumor node metastasis stage ( p = 0.0221), as well as poor prognosis ( p < 0.05). Furthermore, down-regulation of protocadherin 7 in gastric cancer cell lines significantly increased their migration and invasion abilities (both p < 0.05), while it had no influence on the gastric cancer cell proliferation ( p > 0.05). Additionally, our results demonstrated that E-cadherin expression was down-regulated in gastric cancer cells with protocadherin 7 depletion. Our data indicated that protocadherin 7 may play important roles in the invasion and metastasis of gastric cancer, and protocadherin 7 could suppress cell migration and invasion through E-cadherin inhibition. Protocadherin 7 can serve as a novel biomarker for diagnostic and prognosis in patients with gastric cancer.

Epigenome-wide analysis of DNA methylation reveals a rectal cancer-specific epigenomic signature

Aim: The aim of the present study is to address a genome-wide search for novel methylation biomarkers in the rectal cancer (RC), as only scarce information on methylation profile is available. Materials & methods: We analyzed methylation status in 25 pairs of RC and adjacent healthy mucosa using the Illumina Human Methylation 450 BeadChip. Results: We found significantly aberrant methylation in 33 genes. After validation of our results by pyrosequencing, we found a good agreement with our findings. The BPIL3 and HBBP1 genes resulted hypomethylated in RC, whereas TIFPI2, ADHFE1, FLI1 and TLX1 were hypermethylated. An external validation by TCGA datasets confirmed the results. Conclusion: Our study, with external validation, has demonstrated the feasibility of using specific methylated DNA signatures for developing biomarkers in RC.

Protocadherin17 Promoter Methylation is a Potential Predictive Biomarker in Clear Cell Renal Cell Carcinoma

Background

Protocadherin17 (PCDH17) is a tumor suppressor gene, and is frequently silenced by promoter methylation in human cancers, including clear cell renal cell carcinoma (ccRCC). However, the clinical significance of PCDH17 methylation in ccRCC remains largely unclear. The aim of the present study was to investigate the methylation status of PCDH17 in ccRCC and its potential relevance to clinicopathological parameters and prognosis.

Material/Methods

Methylation-specific PCR was used to examine the methylation status of PCDH17 in 191 ccRCC tumors and matched paired adjacent noncancerous tissues. Subsequently, the associations between PCDH17 methylation and clinicopathological parameters and prognosis of patients with ccRCC were analyzed.

Results

PCDH17 methylation occurred in 66.5% of ccRCC tumors, but in only 12.1% of adjacent noncancerous tissues. PCDH17 methylation is significantly correlated with advanced stage, higher grade, and lymph node metastasis in ccRCC. Moreover, it is an independent prognostic factor for progression-free survival and overall survival of patients with ccRCC.

Conclusions

PCDH17 methylation occurred more frequently and was associated with malignant clinicopathological characteristics and poor prognosis in ccRCC patients. Thus, PCDH17 methylation may be used as a novel biomarker to predict the prognosis of patients with ccRCC.

Hypermethylation of the 16q23.1 tumor suppressor gene ADAMTS18 in clear cell renal cell carcinoma

To identify tumor suppressor genes (TSGs) silenced by hypermethylation and discover new epigenetic biomarkers for early cancer detection. ADAMTS18, located at 16q23.1, has been reported to be a critical TSG in multiple primary tumors; however, this has not yet been verified in clear cell renal cell carcinoma (ccRCC). We explored epigenetic alterations in this gene in ccRCC and analyzed possible clinicopathological associations. We examined ADAMTS18 gene expression and methylation by semi-quantitative reverse transcription PCR (RT-PCR) and methylation-specific polymerase chain reaction (MSP) in 5 ccRCC-derived cell lines before and after treatment with 5-aza-2'-deoxycytidine (5-AzaC). MSP was further performed for 101 ccRCC primary tumors and 20 adjacent normal tissues. Some cell lines and specimens were examined by subsequent bisulfite genomic sequencing (BGS) and real-time PCR. Further, we analyzed the relationship between the ADAMTS18 gene methylation and clinicopathological features, including short-term disease-free survival (DFS), in patients with ccRCC. ADAMTS18 down-regulation and hypermethylation were detected in the ccRCC-derived cell lines using RT-PCR and MSP. Treatment with 5-AzaC reversed the hypermethylation of the ADAMTS18 gene and restored its expression. Hypermethylation was further detected in 44 of 101 (43.6%) primary tumors and 3 of 20 (15.0%) adjacent normal tissues. However, a significant difference between both groups was observed (p = 0.02). BGS analysis and real-time PCR were subsequently performed to confirm the results of RT-PCR and MSP. Furthermore, the methylation status of ADAMTS18 was not significantly associated with gender, age, location, tumor diameter, pathological stage, nuclear grade or short-term DFS in patients with ccRCC (p > 0.05). The ADAMTS18 gene is often down-regulated by hypermethylation in ccRCC-derived cell lines and primary tumors, indicating its critical role as a TSG in ccRCC. We conclude that ADAMTS18 gene hypermethylation may be involved in the tumorigenesis of ccRCC and may serve as a novel biomarker for this disease.