Oogenic JNK in gonadotoxic chemotherapy-induced primary ovarian insufficiency

PROJECT SUMMARY The advances in cancer survival rates greatly enhance the awareness of side effects of cancer therapy and long- term life quality after cancer. Primary ovarian insufficiency (POI) and infertility are major side effects in young female cancer patients. As the female gonad, the ovary contains various stages of follicles as its functional unit. Each follicle consists of a central germ cell oocyte and surrounding somatic cells. Primordial follicles are at the earliest stage and remain quiescent for months or decades to establish ovarian reserve, a marker of female reproductive life span. Our research teams have demonstrated that commonly used chemotherapeutic drugs, including doxorubicin (DOX), cisplatin (CDDP), and cyclophosphamide (CPA), primarily induce DNA damage and apoptosis of the oocytes in primordial follicles, resulting in the entire primordial follicle death, POI, infertility, and endocrine disorders. Mechanistically, the gonadotoxic anti-cancer agents activate DNA damage response (DDR)-TAp63-related signaling to trigger oocyte apoptosis. However, the underlying mechanism remains largely unknown. Using wild type (WT) mice and a genetically modified mouse model with oocyte-specific deletion of all three c-Jun NH2-terminal kinase (JNK) genes (Jnk1/2/3), our preliminary studies demonstrated that: (1) JNK was selectively activated in primordial follicle oocytes following DOX treatment; (2) a selective JNK inhibitor, SP600125, blocked DOX-induced activation of TAp63 and follicle atresia; (3) oogenic deletion of JNK didn’t affect normal ovarian functions but prevented the induction of apoptotic genes and primordial follicle atresia following DOX treatment; and (4) pharmacological inhibition or genetic deletion of JNK blocked TAp63 activation induced by CDDP and CPA, the other two gonadotoxic anti-cancer agents. Based on these preliminary data and the fact that JNK has been found to pro-oncogenic in certain types of cancer such as leukemia, our central hypothesis is that JNK critically regulates DDR-TAp63-related apoptotic signaling in primordial follicle oocytes following treatment with gonadotoxic anti-cancer agents; and pharmacological inhibition of JNK prevents chemotherapy-induced POI and infertility without compromising anti-cancer efficacy of chemotherapy. We will use DOX as a representative gonadotoxic anti-cancer agent to test our hypothesis. In Aim 1, we will investigate the mechanism by which JNK regulates DDR-related apoptotic signaling in primordial follicle oocyte following DOX treatment. In Aim 2, we will determine the efficacy of pharmacological inhibition of JNK against DOX treatment on protecting ovarian reserve in a young leukemic female mouse model. Completion of these two Specific Aims will allow us to (1) elucidate the molecular mechanisms of oogenic JNK in contributing to DDR-TAp63-related apoptotic signaling in primordial follicle oocytes following treatment with gonadotoxic chemotherapeutic agents, and (2) capitalize on the cell type-dependent pro- or anti-apoptotic effects of JNK to identify selective JNK inhibitors that preserve ovarian reserve, fertility, and ovarian endocrine functions in young female cancer survivors without interfering with the efficacy of chemotherapy.