Apoptosis, bcl-2 expression, and proliferation in benign and malignant endometrial epithelium:: An approach using multiparameter flow cytometry

Objective, Disturbances in the regulation of cell proliferation and differentiation play an important role in the formation of neoplastic lesions. Consequently, abnormalities in apoptosis regulation may contribute to this process. Expression of a neoepitope on cytokeratin 18, unmasked by an early caspase cleavage event and recognized by the novel monoclonal antibody M30, is an indicator of early epithelial cell apoptosis. The purpose of this study was to evaluate the quantitative relation among apoptosis (M30), cell persistence (bcl-2), and proliferation (S-phase fraction; SPF) in malignant and benign endometrium. Methods. Using multiparameter DNA flow cytometry on 54 formalin-fixed paraffin-embedded samples from benign (proliferative, secretory, inactive, and hyperplastic endometrium) and malignant (grades 1-3 endometrial adenocarcinoma) endometrial tissue, bcl-2 expression and M30 reactivity were assessed together with the SPF in the cytokeratin-positive epithelial cells. Results, Benign cyclic endometrium showed a relatively high bcl-2 expression and low M30 reactivity in the proliferative phase whereas in the secretory phase this relation was inverse, In endometrial hyperplasia the expression of bcl-2 was increased compared to that in secretory and postmenopausal endometrium, but still below the level of proliferative samples. The expression of M30 also increased compared to normal proliferative endometrium but did not reach the level of endometrium in the secretory phase of the menstrual cycle. In cancer the expression of bcl-2 decreased with the progression of differentiation grade. For M30 expression this relation was inverse. Overall there was a significant increase of M30 reactivity in cancerous compared to hyperplasia and normal cyclic endometrium. Conclusion. Transition of endometrial epithelium from hyperplasia to cancer seems to involve both increased apoptosis and decreased bcl-2 expression. Flow cytometric evaluation of M30 and bcl-2 expression levels, with the SPF, in currettage specimens from postmenopausal patients complaining of bleeding provides a quantitative assessment of endometrial apoptosis, anti-apoptosis, and proliferation. Further studies are needed to determine the relationship among these three processes as indicators of the biological behavior of gynecological tumors. (C) 2000 Academic Press.