[Promoter hypermethylation gene patterns in gynecological tumors]

Research Progress of DNA Methylation in Endometrial Cancer

Endometrial cancer (EC)) is one of the most common malignant tumors of the female genital system, with an increasing incidence and mortality, worldwide. Although the therapeutic strategy of EC is still complicated and challenging, further understanding of carcinogenesis from a gene perspective would allow an effort to improve therapeutic precision in this complex malignancy. DNA methylation is the most widely studied epigenetic alteration in human tumors. Aberrant DNA methylation events, resulting in altered gene expression, are features of many tumor types. In this review, we provide an update on evidence about the roles of aberrant DNA methylation within some classical tumor suppressor genes and oncogenes in endometrial carcinogenesis, and report on recent advances in the understanding of the contribution of aberrant DNA methylation to EC, as well as opportunities and challenges of DNA methylation in EC management and prevention.

Aberrant promoter hypermethylation of p16 gene in endometrial carcinoma

Previous studies demonstrated that the loss of function of the p16INK4A gene is mainly caused by the hypermethylation of p16 gene promoter; however, whether or not it is associated with the incidence of endometrial carcinoma (EC) remains unclear. In the current study, we conducted a meta-analysis to investigate the effects of p16 gene promoter hypermethylation on the incidence of EC. Detailed research publications were searched from Embase, PubMed, and ISI Web of Knowledge for composition in English or Chinese. The pooled data were collected and analyzed by Review Manager 5.2. Odds ratios (ORs) were calculated and summarized respectively. Six eligible studies, including 261 patients were selected and analyzed. The pooled OR was 0.42, test for overall effect, Z = 10.19, P < 0.0001, indicating that p16 gene promoter hypermethylation was significantly correlated with the EC patients. The results of our study strongly suggest that p16 gene promoter hypermethylation is correlated with an increased risk of EC. P16 gene promoter hypermethylation plays a critical role in endometrial carcinogenesis.

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

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.