Increasing 14-3-3 sigma expression with declining estrogen receptor α and estrogen-responsive finger protein expression defines malignant progression of endometrial carcinoma

14-3-3 sigma (sigma) is a negative regulator of the cell cycle and contributes to G2 arrest. Lack of its expression due to hypermethylation of CpG islands has been reported in some carcinomas. A recent study showed that 14-3-3 sigma was down-regulated through proteolysis by estrogen-responsive finger protein (Efp). Here, we investigated the expression of 14-3-3 sigma, hormone receptors, Efp and p53 in 86 cases of endometrial adenocarcinoma and 46 cases of normal or non-neoplastic endometria by means of immunohistochemistry and methylation-specific polymerase chain reaction. In normal endometrium, 14-3-3 sigma was overexpressed in the mid- to late-secretory phase due to hypomethylation. In endometrial adenocarcinoma, 14-3-3 sigma expression was low in low grade endometrioid adenocarcinoma due to hypermethylation, and increased significantly with increasing histological grade due to hypomethylation. 14-3-3 sigma expression inversely correlated with estrogen receptor alpha, progesterone receptor and Efp, and positively correlated with myometrial invasion and lymph node metastasis. These results suggest that 14-3-3 sigma was one of the menstrual cycle-related proteins regulated by epigenetic methylation, and its expression was influenced by epigenetic methylation or hormone receptors in progression of endometrial adenocarcinoma, and therefore was more than just a cell-cycle regulator.