BCL-X(L) IS EXPRESSED IN OVARIAN-CARCINOMA AND MODULATES CHEMOTHERAPY-INDUCED APOPTOSIS

Objective. To investigate the role of Bcl-x(L) in resistance to chemot herapy-induced apoptosis in ovarian carcinoma. Methods. Two human ovar ian carcinoma cell lines were used in this study: A2780 and SKOV3. A27 80 cells were transfected with human Bcl-x(L) or control plasmid alone . Expression of Bcl-x(L) in single cell clones was analyzed by flow cy tometry and protein expression was confirmed by Western blot, For in v itro chemotherapy-induced death assays, cisplatin and Taxol were used. The percentage of apoptotic cells was determined by nuclear propidium iodide staining followed by flow cytometric analysis. Human ascites s amples were used to make tumor lysates which were then analyzed for ex pression of Bcl-x(L) protein by Western blot. Results. A2780 cells exp ress low levels of endogenous Bcl-x(L) while SKOV3 cells express high amounts as determined by Western blot. In addition, A2780 cells are se nsitive to chemotherapy-induced cell death while SKOV3 cells are resis tant. To determine if chemoresistance is mediated by expression of Bcl -x(L), A2780 cells were transfected with Bcl-x(L) or control plasmid, Cells were incubated with either cisplatin or Taxol to induce apoptosi s, Bcl-x(L) expressing cells were highly resistant to cisplatin and Ta xol compared with controls (P < 0.05). All samples of malignant ascite s analyzed expressed high levels of Bcl-x(L) on Western blot. Conclusi ons. The results of these studies indicate that Bcl-x(L) is expressed in ovarian carcinoma, and in A2780 cells functions in a manner analogo us to Bcl-2 by inhibiting chemotherapy-induced apoptosis. This may hav e prognostic significance; previous studies have demonstrated that pat ients with breast cancer that overexpress Bcl-2 have low-grade, hormon ally responsive tumors. In ovarian carcinoma, another Bcl-2 family mem ber, Bcl-x(L) may be responsible for modulating resistance to chemothe rapy-induced apoptosis, (C) 1998 Academic Press.