The mammalian target of rapamycin protein expression in human granulosa cell tumors

Abstract

Objective: To investigate the role of mammalian target of rapamycin (mTOR) in human granulosa cell ovarian tumors and the therapeutic effect of rapamycin in COV434 mitotic granulosa cell lines. Material and Methods: A retrospective evaluation of the medical records and pathologic sections of patients with granulosa cell ovarian carcinoma was performed. mTOR and p-mTOR expression was immunohistochemically investigated. A COV434 cell culture were treated with 0.5, 1, 2, and 5 mu M rapamycin. Real-time growth curve analysis via xCELLigence system and apoptotic cell analysis via YO-PROT-1 Iodide were performed to assess the therapeutic effect of rapamycin on cancer cells. Results: A total of twenty patients were evaluated. mTOR staining was detected in 18 (90\%) patients. Mild, moderate, intense, and very intense staining was observed in three (15\%), eight (40\%), six (30\%), and one (5\%) sample, respectively. The mean mTOR staining ratio was 59 +/- 41\%. P-mTOR staining was observed in two ( 10\%) patients. One (5\%) patient had 5\% staining, and one (5\%) patient had 100\% staining for p-mTOR. Both of the latter patients had very intense staining. Rapamycin caused a dose-dependent growth arrest and induced apoptosis in COV434 mitotic granulosa cells. The real-time growth curves of the cells treated with these drugs were distinguished by a marked reduced slope after exposure for several hours, indicating a rapid onset of apoptosis. Live/dead cell analysis with YO-PRO-1 staining showed that rapamycin induced apoptosis in 24\% of the cells when used at 1 mu M concentration, whereas the rate increased to 61\% and 72\% when the cells were treated with 2 mu M and 5 mu M rapamycin, respectively. Conclusion: mTOR expression is observed in various degrees in 90\%, and p-mTOR expression is observed in only 10\% of patients with granulosa cell ovarian carcinoma. Rapamycin caused a dose-dependent growth arrest and apoptosis in COV434 mitotic granulosa cells.