Investigating RASSF1A hypermethylation and endometrial carcinoma occurrence and development using in vivo and in vitro demethylation of 5-AZA-2’-deoxy cytidine

Objective: To explore the role of RASSF1A in the occurrence and development of endometrial cancer. Methods: In vitro experiments used human endometrial cancer cells (HEC-1-B) treated with different concentrations of 5-AZA-2’-deoxy cytidine (5-Aza-CdR). In vivo experiments used HEC-1-B-treated mice that were exposed to combinations of cisplatin (DDP), medroxyprogesterone acetate (MCP), and/or 5-Aza-CdR. Analysis was then performed using immunohistochemical, MTT, methylation-specific PCR, fluorescence quantitative PCR, Western blotting, and TUNEL staining approaches. Results: When compared to both atypical hyperplasia and normal endometrial tissue, RASSF1A protein expression was significantly reduced in endometrial carcinoma tissues (P<0.01). There was no significant difference between atypical or normal endometrial tissue (P = 0.692). There were no significant differences in RASSF1A protein expression in endometrial carcinoma across age (P = 0.418), tumor grade (P = 0.433), stage (P = 0.873), or classification (P = 0.520). Furthermore, RASSF1A promoter regions were abnormally hypermethylated, leading to decreased mRNA and protein expression in HEC-1-B cells and xenograft tissues. 5-Aza-CdR application reversed the abnormal RASSF1A hypermethylation, inhibited transplanted tumor growth, and induced apoptosis in a concentration-dependent manner. Finally, 5-Aza-CdR co-application significantly strengthened the efficacy of both DDP and MPA in tumor suppression. Conclusions: Either inactivation or low expression of RASSF1A may play a role in the occurrence of endometrial cancer, but the determining factor may be the abnormal hypermethylation of RASSF1A. RASSF1A is a potential target, making demethylation a possible, effective treatment option for endometrial cancer.