Downregulation of 14-3-3σ in ovary, prostate and endometrial carcinomas is associated with CpG island methylation

The 14-3-3sigma inhibitor of cell cycle progression has been shown to be target of epigenetic deregulation in many forms of human cancers; however, its role in urological and gynecological cancers has not been studied. Here, we have analyzed the expression of 14-3-3sigma, wild-type p53 and mutated p53 in over 300 cases of the most common cancers occurring in the urological and gynecological tracts and its normal counterpart tissue by immunohistochemistry using the multiple tumor tissue microarrays. 14-3-3sigma expression was detected in normal epithelia from most organs with sporadic expression in renal tubules and absence in the testis. In contrast to normal tissue, 14-3-3sigma expression was lost in 40-60% of adenocarcinomas of the breast, ovary, endometrium and prostate. There was no association between 14-3-3sigma and wild-type/mutated p53 expression. By performing methylation-specific PCR, we showed a close association of 14-3-3sigma CpG island methylation and low protein expression levels of 14-3-3sigma. In addition, a direct link of 14-3-3sigma mRNA expression levels to CpG island methylation is demonstrated in two human cancer cell lines. Loss of 14-3-3sigma expression due to promoter hypermethylation may represent the most frequent molecular aberration in ovarian, endometrial and prostate adenocarcinomas.