Epigenetic alteration of p16 and retinoic acid receptor beta genes in the development of epithelial ovarian carcinoma

Abstract

Silencing of tumor suppressor and tumor-related genes by promoter hypermethylation is one of the major events in ovarian carcinogenesis. In this study, we analyzed aberrant promoter methylation of p16 and RAR-β genes in 134 epithelial ovarian carcinomas (EOCs), 23 low malignant potential (LMP) tumors, 26 benign cystadenomas, and 15 normal ovarian tissues. Methylation was investigated by methylation-specific PCR (MSP), and the results were confirmed by bisulfite DNA sequencing. Relative gene expression of p16 and RAR-β was done using quantitative reverse transcriptase PCR (qRT-PCR) on 51 EOC cases, 9 LMP tumors, and 7 benign cystadenomas with 5 normal ovarian tissues. Aberrant methylation for p16 and RAR-β was present in 43 % (58/134) and 31 % (41/134) in carcinoma cases, 22 % (05/23) and 52 % (12/23) in LMP tumors, and 42 % (11/26) and 69 % (18/26) in benign cystadenomas. No methylation was observed in any of the normal ovarian tissues. The mRNA expression level of p16 and RAR-β was significantly downregulated in EOC and LMP tumors than the corresponding normal tissues whereas the expression level was normal in benign cystadenomas for p16 and slightly reduced for RAR-β. A significant correlation of p16 promoter methylation was observed with reduced gene expression in EOC. For RAR-β, no significant correlation was observed between promoter methylation and gene expression. Our results suggest that epigenetic alterations of p16 and RAR-β have an important role in ovarian carcinogenesis and that mechanism along with methylation plays a significant role in downregulation of RAR-β gene in ovarian cancer.

Quantitative assessment of aberrant <em>P16^INK4a</em> methylation in ovarian cancer: a meta-analysis based on literature and TCGA datasets

“…After reading titles and abstracts, 84 records were identified for further full-text assessment, which further excluded 60 more articles. Finally, 24 studies from 1997 to 2015 were included in this meta-analysis 17,20,22–30,37–49…”

“…The detection methods of methylation in 20 studies were methylation-specific PCR (MSP) and real-time quantitative MSP, while methylation-specific multiplex ligation-dependent probe amplification was used in two studies, MethyLight was used in one study, and Southern analysis was used in one study. Among the 24 articles, 20 studies17,20,22–30,37–40,42,45–47,49 addressed the risk of P16 INK4a promoter methylation in ovarian cancer, 10 studies20,25,28,29,38,41,43,44,47,48 covered clinicopathological features, and 3 studies20,42,43 discussed prognosis. To explore the relationship between P16 INK4a promoter methylation and ovarian cancer risk, three groups, that is, normal tissues, benign tissues, and low malignant potential or borderline tumor tissues (LMP), were compared.…”

“…Only two studies42,43 containing 464 patients evaluated the P16 INK4a promoter methylation on progression-free survival (PFS) and three studies20,42,43 containing 600 patients on overall survival (OS). The combined results revealed P16 INK4a promoter methylation was significantly associated with a poor PFS by univariate Cox proportional hazards regression model (HR=1.68, 95% CI=1.26–2.24; Figure 5A).…”

“…Several studies reported that P16 INK4a promoter methylation was associated with an increasing trend in ovarian cancer,20–23 while, other studies suggested that P16 INK4a promoter methylation was not related to the occurrence of ovarian cancer 24–30. Interestingly, even the conclusions in two published meta-analyses were inconsistent.…”

Development of a multiplex MethyLight assay for the detection of DAPK1 and SOX1 methylation in epithelial ovarian cancer in a north Indian population

“…Aberrant DNA methylation is a very stable repressive mark of DNA which is commonly associated with the loss of gene function (Antiquera and Bird, 1999). Numerous reports indicate that methylation at CpG islands in the promoter region is the major cause of silencing of many tumor suppressor genes, such as RASSF1A, DAPK1, p16 and GBGT1, in various cancers (Collins et al, 2006;Bammidi et al, 2012;Matoo et al, 2013;Shi et al, 2013;Bhagat et al, 2014;Jacob et al, Edited by Rimantas Kodzius2014). Its high stability and sensitivity of detection make DNA methylation an attractive clinical tool for the diagnosis of different cancers, prediction of potential malignancy progression and metastasis/recurrence of cancer.…”