Targeting PARG induces tumor cell growth inhibition and antitumor immune response by reducing phosphorylated STAT3 in ovarian cancer.

BACKGROUND: Ovarian cancer is the most lethal gynecological malignancy, with limited treatment options after failure of standard therapies. Despite the potential of poly(ADP-ribose) polymerase inhibitors in treating DNA damage response (DDR)-deficient ovarian cancer, the development of resistance and immunosuppression limit their efficacy, necessitating alternative therapeutic strategies. Inhibitors of poly(ADP-ribose) glycohydrolase (PARG) represent a novel class of inhibitors that are currently being assessed in preclinical and clinical studies for cancer treatment. METHODS: By using a PARG small-molecule inhibitor, COH34, and a cell-penetrating antibody targeting the PARG's catalytic domain, we investigated the effects of PARG inhibition on signal transducer and activator of transcription 3 (STAT3) in OVCAR8, PEO1, and Brca1-null ID8 ovarian cancer cell lines, as well as in immune cells. We examined PARG inhibition-induced effects on STAT3 phosphorylation, nuclear localization, target gene expression, and antitumor immune responses in vitro, in patient-derived tumor organoids, and in an immunocompetent Brca1-null ID8 ovarian mouse tumor model that mirrors DDR-deficient human high-grade serous ovarian cancer. We also tested the effects of overexpressing a constitutively activated STAT3 mutant on COH34-induced tumor cell growth inhibition. RESULTS: Our findings show that PARG inhibition downregulates STAT3 activity through dephosphorylation in ovarian cancer cells. Importantly, overexpression of a constitutively activated STAT3 mutant in tumor cells attenuates PARG inhibitor-induced growth inhibition. Additionally, PARG inhibition reduces STAT3 phosphorylation in immune cells, leading to the activation of antitumor immune responses, shown in immune cells cocultured with ovarian cancer patient tumor-derived organoids and in immune-competent mice-bearing mouse ovarian tumors. CONCLUSIONS: We have identified a novel antitumor mechanism underlying PARG inhibition beyond its primary antitumor effects through blocking DDR in ovarian cancer. Furthermore, targeting PARG activates antitumor immune responses, thereby potentially increasing response rates to immunotherapy in patients with ovarian cancer.

Ovarian Cancer After Prophylactic Salpingectomy in a Patient With Germline BRCA1 Mutation.

BACKGROUND: Women with germline BRCA1 or BRCA2 mutations have a lifetime risk of ovarian cancer of up to 46%. Opportunistic salpingectomy has been advocated as a risk-reducing strategy owing to increasing recognition of tubal origin, yet evidence of efficacy in this high-risk population is limited. CASE: This is the case of a woman with a BRCA1 mutation who underwent prophylactic mastectomy and bilateral salpingectomy with ovarian retention before the age of 40 years. She did not undergo oophorectomy and subsequently developed stage IV high-grade serous ovarian cancer 4 years after her initial surgery. CONCLUSION: More research is needed to determine the role of prophylactic salpingectomy with delayed oophorectomy, optimal timing of completion oophorectomy, and the risks and benefits compared with up-front risk-reducing salpingo-oophorectomy.

Management and survival of patients with Mullerian adenosarcoma of the cervix without sarcomatous overgrowth desiring fertility preservation, a case report and review of the literature.

•Cervical Mullerian adenosarcoma is a tumor that affects reproductively aged women.•Hysterectomy had been the standard of care for these premenopausal women.•This case reports the most minimally invasive approach with no recurrence.•Accurate pathology interpretation is essential to diagnose and treat patients.•This is a rare tumor that if misdiagnosed or mischaracterized could be lethal.