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.

Impact of Sodium Thiosulfate on Prevention of Nephrotoxicities in HIPEC: An Ancillary Evaluation of Cisplatin-Induced Toxicities in Ovarian Cancer

PURPOSE

Hyperthermic intraperitoneal chemotherapy (HIPEC) with cisplatin confers a survival benefit in epithelial ovarian cancer (EOC) but is associated with renal toxicity. Sodium thiosulfate (ST) is used for nephroprotection for HIPEC with cisplatin, but standard HIPEC practices vary.

METHODS

A prospective, nonrandomized, clinical trial evaluated safety outcomes of HIPEC with cisplatin 75 mg/m2 during cytoreductive surgery (CRS) in patients with EOC (n = 34) and endometrial cancer (n = 6). Twenty-one patients received no ST (nST), and 19 received ST. Adverse events (AEs) were reported according to CTCAE v.5.0. Serum creatinine (Cr) was collected preoperatively and postoperatively (Days 5-8). Progression-free survival (PFS) was followed. Normal peritoneum was biopsied before and after HIPEC for whole transcriptomic sequencing to identify RNAseq signatures correlating with AEs.

RESULTS

Forty patients had HIPEC at the time of interval or secondary CRS. Renal toxicities in the nST group were 33% any grade AE and 9% grade 3 AEs. The ST group demonstrated no renal AEs. Median postoperative Cr in the nST group was 1.1 mg/dL and 0.5 mg/dL in the ST group (p = 0.0001). Median change in Cr from preoperative to postoperative levels were + 53% (nST) compared with - 9.6% (ST) (p = 0.003). PFS did not differ between the ST and nST groups in primary or recurrent EOC patients. Renal AEs were associated with downregulation of metabolic pathways and upregulation of immune pathways.

CONCLUSIONS

ST significantly reduces acute renal toxicity associated with HIPEC with cisplatin in ovarian cancer patients. As nephrotoxicity is high in HIPEC with cisplatin, nephroprotective agents should be considered.

BRCA germline mutations in multiethnic gynecologic patients: A 10-year retrospective analysis from a single cancer institute

Histologic and genetic mutation information from racially and ethnically diverse populations is warranted to better inform future cancer predisposition and promote health equity. A single institutional, retrospective capture of patients with gynecologic conditions and genetic susceptibilities to malignant neoplasms of the breast or ovaries was performed. This was achieved with manual curation of the electronic medical record (EMR) from 2010-2020 with the use of ICD-10 code searches. Among 8983 consecutive women identified with gynecologic conditions, 184 were diagnosed with pathogenic/likely pathogenic (P/LP) germline BRCA (gBRCA) mutations. Median age was 54 (22-90). Mutations included insertion/deletion (majority frameshift, 57.4%), substitution (32.4%), large structural rearrangement (5.4%), and alteration in splice site/intronic sequence (4.7%). A total of 48% were non-Hispanic White, 32% Hispanic or Latino, 13% Asian, 2% Black, and 5% Other. The most common pathology was high grade serous carcinoma (HGSC, 63%), followed by unclassified/high grade carcinoma (13%). Additional multigene panels led to the detection of 23 additional BRCA-positive patients with germline co-mutations and/or variants of uncertain significance in genes functionally involved in DNA repair mechanisms. Hispanic or Latino and Asian individuals comprised 45% of patients with concomitant gynecologic condition and gBRCA positivity in our cohort, confirming that germline mutations are represented across racial and ethnic groups. Insertion/deletion mutations, the majority of which led to a frameshift change, occurred in approximately half of our patient cohort, which may have prognostic implication for therapy resistance. Prospective studies are needed to unravel the significance of germline co-mutations in gynecologic patients.

Cisplatin-induced nephrotoxicity in hyperthermic intraperitoneal chemotherapy (HIPEC) is mitigated by sodium thiosulfate: Clinical and toxicotranscriptomic results of a prospective trial

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Background: Hyperthermic intraperitoneal chemotherapy (HIPEC) with cisplatin confers a survival benefit in epithelial ovarian cancer (EOC). Unfortunately, cisplatin is associated with significant renal toxicities. Sodium thiosulfate (ST) has been suggested as a nephroprotectant for patients undergoing HIPEC with cisplatin. Methods: A feasibility trial ( ClinicalTrials.gov: NCT01970722) evaluated safety outcomes of HIPEC with cisplatin 75 mg/m2 during optimal cytoreductive surgery (CRS) in patients with EOC and endometrial cancer (n = 40), with or without ST. Twenty-one patients received no sodium-thiosulfate (nST group), and nineteen patients received sodium thiosulfate (ST group). Toxicities were reported according to CTCAE v. 5. Progression-free survival was followed. Normal tissue biopsies were collected intra-operatively immediately following HIPEC and cisplatin exposure in a subset of patients (n = 21), and profiled with transcriptomic sequencing to identify RNAseq signatures correlating with toxicities. Hierarchical cluster analyses identified distinct transcriptomic signatures in post-HIPEC normal samples of patients with renal AEs (rAEs) compared to no renal AEs (nrAEs). KEGG pathway analysis identified up- or downregulated gene sets using GSEA. Results: Forty patients had HIPEC at time of optimal CRS. Renal toxicities were higher in the nST group (no sodium thiosulfate) compared to the ST group. nST patients had 17% any grade, and 9% Grade 3 AEs for acute and chronic kidney injuries. In contrast, ST patients suffered 0% renal AEs. rAE patients demonstrated upregulation of immune signaling pathways (Toll-like receptor, Natural killer cell, Nod-like receptor); and downregulation of metabolic pathways. Top upregulated genes in rAE patients included immune (e.g. neutrophil) related genes, while downregulated genes included metabolism genes. Kaplan-Meier curves demonstrated improved PFS in primary ovarian cancer patients undergoing HIPEC who were treated with ST vs no ST (p = 0.04, NR vs 13.4 mo). Conclusions: HIPEC with cisplatin results in significant renal toxicities. The mechanisms of cisplatin-induced nephrotoxicity in HIPEC are immune-related and reflect reduced metabolism. Sodium thiosulfate abrogated renal toxicities and did not decrease PFS. Clinical trial information: NCT01970722.

Niraparib-induced STAT3 inhibition increases its antitumor effects

Recently, poly(ADP-ribosyl)ation polymerase inhibitors (PARPis), which induce synthetic lethality of tumor cells with DNA damage repair defects, have emerged as a promising therapy for ovarian, breast, and pancreatic cancer. Although the PARPi Olaparib is limited to treating cancer patients with DNA repair deficiencies, the PARPi Niraparib is FDA approved to treat ovarian cancer patients regardless of their status in DNA repair pathways. Despite differences in the affinity to PARP enzymes, the rationale behind the clinical use of Niraparib in patients without DNA repair deficiencies is still lacking. Moreover, only Olaparib has been approved for pancreatic ductal adenocarcinoma (PDAC) patients with BRCA mutations, accounting for only 5-7% of total PDACs. It remains unclear whether Niraparib could be beneficial to PDACs without BRCA mutations. We found that Niraparib inhibits ovarian and PDAC tumor cell growth, regardless of BRCA mutational status, more effectively than Olaparib. Unlike Olaparib, which is known to activate STAT3, Niraparib inhibits STAT3 activity in ovarian and PDAC cancer cell lines and patient tumors. Moreover, Niraparib regulates the expression of several STAT3 downstream genes involved in apoptosis. Overexpression of a constitutively activated STAT3 mutant rescues Niraparib-induced cancer cell apoptosis. Our results suggest that Niraparib inhibits pSTAT3 by interfering with SRC tyrosine kinase. Collectively, our studies provide a mechanism underlying Niraparib's ability to induce tumor cell apoptosis without BRCA mutations, suggesting the potential use of Niraparib for treating PDAC patients regardless of BRCA status.

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

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Cervical Mullerian adenosarcoma is a tumor that affects reproductively aged women.

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Hysterectomy had been the standard of care for these premenopausal women.

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This case reports the most minimally invasive approach with no recurrence.

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Accurate pathology interpretation is essential to diagnose and treat patients.

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This is a rare tumor that if misdiagnosed or mischaracterized could be lethal.