Mechanisms of chemotherapy-induced oocyte death through activation of TAp63α

Primary ovarian insufficiency is a severe side effect of classical chemotherapy and radiotherapy in treatment of female cancer patients of reproductive age. The p53-homolog TAp63α emerged as the key protein regulating apoptosis following DNA damage in oocytes of primordial follicles. In this study, we monitored the toxicity of widely used chemotherapeutic agents on oocytes of primordial follicles utilizing a GFP-c-kit transgenic mouse model, the involvement of active TAp63α and the mechanism of action leading to its activation. Our studies show that alkylating agents and topoisomerase II poisons are potent activators of TAp63α by directly inducing DNA damage. Oxidative stress and DNA intercalation were not sufficient to trigger TAp63α activation despite showing a strong general toxicity. These results are in agreement with several previous investigations that have demonstrated that DNA double-strand breaks are the most effective way to initiate apoptosis in oocytes of primordial follicles. The widely used catalytic topoisomerase II inhibitor ICRF-187 was able to prevent activation of TAp63α by the topoisomerase II poison doxorubicin but did not prevent oocyte death, suggesting an alternative mechanism of cell death induction.