Abstract B033: Targeting STAT3 and NF-kappaB in ovarian cancer mediated mesothelial clearance

Abstract Ovarian cancer remains a deadly disease, in part due to metastases. Ovarian cancer metastasizes in the peritoneum by interacting with and clearing the protective mesothelial layer of cells. While several studies have determined that actin related proteins and epithelial to mesenchymal transition (EMT) related genes are involved in mesothelial clearance, the additional major signaling pathways involved in mesothelial clearance remain largely unknown. We hypothesized that the STAT3 signaling pathway could be involved in mesothelial clearance since STAT3 is known to play a role in migration. In addition, we previously found that by separating ovarian cancer patients from the Cancer Genome Atlas (TCGA) by STAT3 expression, the Hallmark EMT gene signature was enriched in ovarian cancer patients with higher levels of STAT3 expression, further supporting our hypothesis that STAT3 could play a role in mesothelial clearance. Therefore, we treated ovarian spheroids with the Jak inhibitor TG101348 to inhibit STAT3 tyrosine phosphorylation and found that this reduced mesothelial clearance. When analyzing the TCGA ovarian cancer patient data separated by STAT3 expression, we also determined that the Hallmark NF-kappaB signature was enriched suggesting a connection between STAT3 and NF-kappaB. As this was bulk tumor data, we wanted to determine if this enrichment was found in the individual cancer cells specifically. Therefore, we analyzed single-cell RNA-seq data from seven high grade serous ovarian cancer patients and found a strong correlation between a STAT3 signature and the NF-kappaB signature in the ovarian cancer cells specifically. This suggested that STAT3 and NF-kappaB may be connected in ovarian cancer and possibly in ovarian cancer mesothelial clearance. Therefore, we treated ovarian cancer spheroids with the NF-kappaB inhibitor BAY 11-7082 and found a reduction in the amount of mesothelial clearance by the ovarian cancer spheroids. Moreover, combination treatment of ovarian cancer spheroids with the STAT3 and NF-kappaB inhibitors enhanced the reduction of mesothelial clearance over each drug alone, suggesting that targeting these two pathways could be useful for ovarian cancer. Importantly, these low doses had no effect on cell viability of the ovarian cancer spheroids, suggesting that this is a mesothelial clearance specific effect. Taken together, this raises the possibility that combination treatment of low dose STAT3-NF-kappaB inhibition could be used to prevent metastasis in ovarian cancer patients. Future work includes a better understanding of the interaction between STAT3 and NF-kappaB and their target genes in the ovarian cancer spheroids during mesothelial clearance and determining how the mesothelial cells may be involved in promoting the ovarian cancer cells during clearance. Overall, our work demonstrates a connection between STAT3 and NF-kappaB that may be useful as a future treatment strategy for ovarian cancer patients. Citation Format: Brendan M. Reilly, Sarah R. Walker. Targeting STAT3 and NF-kappaB in ovarian cancer mediated mesothelial clearance abstract. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Ovarian Cancer Research; 2025 Sep 19-21; Denver, CO. Philadelphia (PA): AACR; Cancer Res 2025;85 (18Suppl): Abstract nr B033.