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

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.

Methods: A retrospective evaluation of the medical records and pathological sections of patients with granulosa cell ovarian carcinoma was performed. mTOR and p-mTOR expression was immunohistochemically investigated. COV434 cell culture were treated with 0.5, 1, 2 and 5 μM rapamycin. Real-time growth curve analysis via xCELLigence system and apoptotic cell analysis via YO-PRO™-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 eighteen (90%) patients. Mild, moderate, intense, and very intense staining was observed in three (15%), eight (40%), six (30%) and one (5%) sample, respectively. 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 µM concentration, whereas the rate increased to 61% and 72% when the cells were treated with 2 µM and 5 µM rapamycin, respectively.

Conclusion: mTOR expression is observed in various degrees in 90%, and p-mTOR expression is observed in only 10% of the patients with granulosa cell ovarian carcinoma. Rapamycin caused a dose-dependent growth arrest and apoptosis in COV434 mitotic granulosa cells.