İnsanda DNA hasarına bağlı ve TAp63-aracılı oosit apoptozunun c-Abl aktivasyonu ile ilişkisi

Rates of young cancer survivors have improved in recent years owing to novel treatments. This success, however, creates an increasing problem: long-term side effects of chemotherapy such as infertility. It is controversial whether c-Abl is essential for oocyte apoptosis and its inhibition with imatinib prevents chemotherapy-induced oocyte damage in mice. As no human data is available, this thesis aimed to explore the mechanism triggered by chemotherapy and the role of c-Abl in TAp63-mediated DNA damage-induced oocytes apoptosis. Ovarian damage was induced with cisplatin in human ovaries which were either xenografted to mice or in vitro cultured. Human immature oocytes, primary granulosa cells, and two different granulosa cell lines were also included. Cisplatin caused DNA damage as evidenced by γ-H2AX, activated checkpoint sensors Chk-1 and Chk-2 and SAPK/JNK pathway, induced TAp63 phosphorylation and triggered apoptosis in human oocytes and granulosa cells whereas it did not associate with c-Abl upregulation. Moreover, imatinib exposure resulted in the formation of bizarrely shaped follicles lacking oocytes and increased follicular atresia. To better understand the actions of imatinib, ovarian tissues were incubated with anti-CD117, a c-kit antagonist drug, but not with another c-Abl inhibitor GNF-2, which lacks an inhibitory action on c-kit and similar toxic effects were observed. Intraperitoneal administration of imatinib to the xenografted animals produced similar histomorphological abnormalities in the ovarian grafts and did not prevent cisplatin-induced follicle loss. In conclusion, phosphorylation of TAp63 at Ser395 has not yet been associated with any function before, so here we define Ser395 for the first time as a site for TAp63 activation in response to DNA damage. Moreover, we provide the first molecular evidence for ovarian toxicity of imatinib in human and heighten the concerns about its gonadotoxicity on the human ovary and urge caution in its use in young female patients.