Direct effects of CPT-11 and SN38 on ovarian granulosa cells

This study aimed to clarify the mechanism by which apoptosis and Fas ligand (FasL) expression are induced in the ovarian granulosa cells of mice injected with irinotecan HCl (CPT-11). To this end, the direct effects of CPT-11 and its active metabolite, SN38, on granulosa cells were investigated. Normal ovarian tissue fragments obtained from 8-week-old female MCH mice were cultured in vitro with CPT-11 or SN38 and paraffin-embedded. After sectioning, the ovarian fragments were analyzed by TUNEL staining to detect apoptotic cells and by immunohistochemistry with an anti-FasL antibody to detect FasL expression. The results revealed no increase in TUNEL-positive granulosa cells in the ovarian tissue fragments cultured with CPT-11 or SN38. Furthermore, CPT-11 and SN38 did not induce FasL expression in the ovarian fragments. In conclusion, apoptosis and FasL expression induced in the ovarian granulosa cells of mice injected with CPT-11 is not caused by direct stimulation with CPT-11 or SN38. Therefore, systemic CPT-11 administration appears to induce apoptosis and FasL expression in granulosa cells via currently unknown endogenous FasL-inducing factors or by active metabolites of CPT-11 other than SN38.