The regulation of MASPIN expression in epithelial ovarian cancer: Association with p53 status, and MASPIN promoter methylation: A Gynecologic Oncology Group study

Objectives: To elucidate the regulation of MASPIN expression in epithelial ovarian cancer (EOC) and associations with p53 status and MASPIN promoter methylation. Methods: Seven EOC cell lines and 110 advanced stage EOC specimens were analyzed for MASPIN promoter methylation. The cell lines were treated with 5-azacytidine (5-azaC) and evaluated for MASPIN promoter methylation, protein, and mRNA expression. Wild-type (wt) p53 was transiently transfected into the mutant p53 (m p53) SKOV3 cells which were treated with 5-azaC. Phosphor imager analysis quantified the percent methylation of the MASPIN promoter. Results: Of the 3 MASPIN-low m p53 cell lines 2 had greater than 5% MASPIN methylation whereas only 1 of 4 MASPIN-high wt p53 cell lines had greater than 5% MASPIN methylation. Despite the presence of aberrant MASPIN promoter methylation in SKOV3 cells, wt p53-transfection alone resulted in a 3.3-fold increase in MASPIN mRNA. The combination of 5-azaC and wt p53-transfection produced a 36% reduction in MASPIN promoter methylation and 4.5-fold increase in MASPIN transcription. Among the 110 ovarian cancer specimens analyzed for methylation of the MASPIN promoter, 81.8% were weakly methylated, 14.5% were heavily methylated and 3.6% were fully methylated. There was no relationship between promoter methylation and p53 status or MASPIN protein expression. However, MASPIN protein was 6 times more likely to be detected in cancer specimens that harbor a p53 mutation relative to cancer specimens with a wt p53 gene. Conclusion: The regulation of MASPIN is a complex multifactorial process that may be controlled by both p53-dependent and -independent epigenetic mechanisms.