Promoter hypermethylation influences the suppressive role of maternally expressed 3, a long non-coding RNA, in the development of epithelial ovarian cancer

Abstract

Maternally expressed 3 (MEG3) is a long non-coding RNA that can activate p53 and inhibit tumorigenesis and progression of various types of cancers. However, the role of MEG3 in epithelial ovarian cancer (EOC) is still unknown. The aim of the present study was to confirm whether MEG3 is downregulated in human EOC, determine its possible mechanism of action and elucidate the role of MEG3 in EOC. Differences in the expression of MEG3 and in the methylation status of the MEG3 promoter between EOC and normal ovary were analyzed using RT-PCR and methylation-specific PCR (MSP), respectively. MTT and EdU assays and flow cytometric analysis were used to assess the growth of ovarian cancer cells after overexpression of MEG3. The target genes regulated by MEG3 were detected with the Dual Luciferase Reporter system. The expression levels of target genes were confirmed using RT-PCR and western blotting. In contrast to normal ovarian tissues, the expression of MEG3 was absent or decreased in most EOC tissues as well as in human EOC cell lines, and the promoter of the MEG3 gene was highly methylated in both cancer tissues and cell lines. Treatment with 5-aza-2-deoxycytidine reversed the promoter hypermethylation and increased MEG3 expression. In addition, ectopic expression of MEG3 suppressed the proliferation and growth of OVCAR3 cells and promoted apoptosis. Finally, MEG3 activated p53 in OVCAR3 cells. In conclusion, our data suggest that MEG3 is epigenetically silenced in EOC due to promoter hypermethylation, which may contribute to the development of EOC.

Microarray expression profiling of long non-coding RNAs in epithelial ovarian cancer

“…The MEG3 gene is located in chromosome 14q32 (25), and is expressed in numerous normal tissues, but its expression level has been reported by various previous studies to be either downregulated or absent in a variety of tumor tissues, including ovarian cancer cells and epithelial ovarian cancer tissues (26)(27)(28). In the present study, HOTAIR was upregulated and MEG3 was downregulated in epithelial ovarian cancer vs. normal tissues.…”

Epigenetic repression of long non-coding RNA MEG3 mediated by DNMT1 represses the p53 pathway in gliomas

“…MEG3 expression is under epigenetic control, and the loss of MEG3 expression due to aberrant CpG methylation of MEG3 has been observed in ovarian cancer (15). Previous studies suggest that DNA methyltransferase 1 (DNMT1) overexpression may be responsible for the aberrant DNA methylation of tumor-related genes in gliomas (16).…”

The Role of Long Non-Coding RNAs in Ovarian Cancer

“…However, its expression has been shown to be decreased or abolished in most epithelial ovarian cancer tissues and cell lines due to intensive promoter hypermethylation [27] . In addition, ectopic expression of MEG3 has inhibited the proliferation and the growth of ovarian cancer cells and enhanced their apoptosis.…”

“…In addition, ectopic expression of MEG3 has inhibited the proliferation and the growth of ovarian cancer cells and enhanced their apoptosis. Consequently, it has been deduced that MEG3 promoter hypermethylation may contribute to the development of epithelial ovarian cancer [27] .…”