Loss of PUMA protects the ovarian reserve during DNA-damaging chemotherapy and preserves fertility

Abstract

Female gametes are stored in the ovary in structures called primordial follicles, the supply of which is non-renewable. It is well established that DNA-damaging cancer treatments can deplete the ovarian reserve of primordial follicles, causing premature ovarian failure and infertility. The precise mechanisms underlying this chemotherapy-driven follicle loss are unclear, and this has limited the development of targeted ovarian-protective agents. To address this fundamental knowledge gap, we used gene deletion mouse models to examine the role of the DNA damage-induced pro-apoptotic protein, PUMA, and its transcriptional activator TAp63, in primordial follicle depletion caused by treatment with cyclophosphamide or cisplatin. Cyclophosphamide caused almost complete destruction of the primordial follicle pool in adult wild-type (WT) mice, and a significant destructive effect was also observed for cisplatin. In striking contrast, Puma−/− mice retained 100% of their primordial follicles following either genotoxic treatment. Furthermore, elimination of PUMA alone completely preserved fertility in cyclophosphamide-treated mice, indicating that oocytes rescued from DNA damage-induced death can repair themselves sufficiently to support reproductive function and offspring health. Primordial follicles were also protected in TAp63−/− mice following cisplatin treatment, but not cyclophosphamide, suggesting mechanistic differences in the induction of apoptosis and depletion of the ovarian reserve in response to these different chemotherapies. These studies identify PUMA as a crucial effector of apoptosis responsible for depletion of primordial follicles following exposure to cyclophosphamide or cisplatin, and this indicates that inhibition of PUMA may be an effective ovarian-protective strategy during cancer treatment in women.

Crosstalk between PTEN/PI3K/Akt Signalling and DNA Damage in the Oocyte: Implications for Primordial Follicle Activation, Oocyte Quality and Ageing

“…This condition may lead to uncoordinated oocyte and granulosa cell growth, as reported in mice [114]. Several publications utilising mouse models have provided evidence that oocytes within resting follicles may be directly targeted by chemotherapy treatments, including CP, cisplatin and doxorubicin [24,26,117,118]. It has also been proposed that primordial follicle depletion following chemotherapy may be induced by the loss of growing follicles with an increase in primordial follicle activation [119,120].…”

“…It has been reported that oocytes of PUMA and NOXA deficient mice are not affected by γ-irradiation and are capable of producing healthy offspring [24]. Primordial follicle loss is also much reduced in PUMA knockout mice treated with CP and cisplatin [26]. Alternatively, upregulation of p53 elicits p21 transcription that directly prevents Cdk2 and Cdk4 transcription and eventually induces cycle arrest (reviewed in [50,91]), thus allowing DNA repair [90].…”

“…High PI3K/Akt activity is linked to a decline in the number of primordial follicles and ovarian ageing [17,18]. Ovarian ageing is associated with impaired DDR within oocytes [19][20][21][22] and this can also be induced following exposure to DNA damaging agents [23][24][25][26][27][28]. Nevertheless, taking advantage of PI3K/Akt signalling pathway effects on follicular recruitment, PTEN inhibition, as a central negative regulator of the pathway, has been widely used to activate primordial follicles in a range of species [18,[29][30][31][32][33].…”

Fifty years of reproductive biology in Australia: highlights from the 50th Annual Meeting of the Society for Reproductive Biology (SRB)

“…The proapoptotic protein p53 upregulated modulator of apoptosis (PUMA) was identified as critical apoptotic trigger in ovarian reserve depletion following chemotherapy. In this way, Pumaknockout mice are not susceptible to chemotherapy-induced loss of ovarian reserve or fertility (Nguyen et al 2018). This suggests that pharmacological targets of apoptosis may be effective ovoprotectants during cancer treatment.…”

Oocytes mount a noncanonical DNA damage response involving APC-Cdh1–mediated proteolysis

“…This triggers primordial follicle apoptosis via Puma and Noxa, resulting in premature depletion of the follicular pool and infertility (Kerr et al, 2012). Significantly, however, knockout or inhibition of TAp63, Chk2, Puma, or Noxa rescues primordial follicle survival following exogenously induced damage (Bolcun-Filas et al, 2014;Kerr et al, 2012;Nguyen et al, 2018;Rinaldi et al, 2017;Suh et al, 2006), and knockout mice go on to have pups (Bolcun-Filas et al, 2014;Kerr et al, 2012), demonstrating that oocytes possess extensive DNA repair capacity.…”