Objective: To evaluate the relationships between Bcl-X expression and apoptosis in normal endometrium (NE), endometrial hyperplasia (EH) and adenocarcinoma (EA). Methods: Immunohistochemical technique was used to examine the localization and expression of Bcl-X proteins in 55 cases of NE, 18 cases of EH and 13 cases of EA. The expression form of Bcl-X protein in normal or abnormal endometrium was further characterized by Western blot analysis. Results: As assessed by immunohistochemistry, Bcl-X proteins were predominantly localized in cytoplasm and nuclear membrane of glandular epithelial cells of the basal layer during the proliferative phase, and the functional layer during the secretory phase. Level of Bcl-X protein was lower in proliferative phase and remarkably increased in the late secretory and the menstrual phase. By Western blotting, it was found the form of Bcl-X was mainly Bcl-XL in proliferative and secretory endometrium. Weak expression of Bcl-Xs was only found in secretory endometrium. Weak Bcl-X expression was also found in cytoplasm of glandular cells of nonatypical hyperplasia, but strong staining presented in atypical hyperplasia, and the only form detected by Western blotting was Bcl-XL. While in adenocarcinoma, both Bcl-XL. and Bcl-Xs existed but the amount of the long form was much higher than that of the short one. Conclusion: Our results suggest that the existance of Bcl-X, especially Bcl-XL plays a role in the regulation of apoptosis in the human endometrium, not only in cycling endometrium but also in endometrial hyperplasia and adenocarcinoma just like the other members of the Bcl-2 family.
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