Abstract 4973: Investigating the role of non-canonical NF-kappaB signaling in tumor cells and macrophages in ovarian cancer

Abstract Background: Ovarian cancer is the most lethal gynecologic malignancy, with a 5-year survival rate of less than 50%. To have a major impact on improving clinical outcomes, a better understanding of the progression of disease and identification of truly novel treatment strategies is critical. Canonical nuclear factor-kappaB (NF-κB) signaling has been extensively studied in preclinical ovarian cancer models; however, systemic NF-κB inhibitors have had disappointing results in early clinical trials. Whether the alternative, non-canonical NF-κB signaling pathway (nc-NF-κB) represents a distinct and improved target for therapy in ovarian cancer is unknown. Here, we aim to investigate the role played by nc-NF-κB signaling both in malignant epithelial cells and in macrophages, a key immune cell component in the tumor microenvironment. Repolarizing tumor-associated macrophages (TAMs) away from pro-tumor M2-like functions towards an anti-tumor M1-like phenotype is a critical priority in macrophage-directed therapies. Methods: In ovarian cancer cell lines, mouse ovarian TAMs cultured ex vivo, and immortalized bone marrow-derived macrophages (BMDMs), nuclear levels of p52 were measured by western blot as a read-out of active nc-NF-κB signaling. Effects of macrophage polarization on nc-NF-κB signaling were determined in unpolarized (M0), M1 polarized (LPS/IFNγ treated) or M2 polarized (IL-4 treated) BMDMs. Finally, effects of inhibiting nc-NF-κB using a specific peptide inhibitor of p52 nuclear import (SN52) on cancer cell growth and macrophage phenotype were determined in sulforhodamine B growth assays and by western blot analysis of PCNA (proliferation marker) and arginase-1 (M2 macrophage marker). Results: We observed high levels of p52 expression in the majority of ovarian cancer cell lines, and in our cultured macrophage models. The functional relevance of these observations was confirmed by experiments showing reduced growth in ovarian cancer cells treated with SN52 and reduced expression of arginase-1 in SN52-treated macrophages. We saw similar results in breast cancer cells and mouse mammary TAMs, showing that nc-NF-κB signaling may also have pro-tumor effects in other cancer types. Complementary studies showed that M2 polarized macrophages expressed markedly higher levels of nuclear p52 than observed in M0 or M1 cells. Based on these promising results, experiments (i) using transgenic mice to allow targeted, inducible activation of nc-NF-κB in macrophages during ovarian cancer progression and (ii) testing the therapeutic effects of SN52 in these cancer models are underway. Conclusions: Although further studies are required to establish the translational relevance of our findings, we hope to identify non-canonical NF-κB signaling as a new therapeutic target in malignant epithelium and macrophages in ovarian cancer and potentially other cancer types. Citation Format: Andrew J. Wilson, Dominique Parker, Robert Cheng, Todd Giorgio, Marta Crispens, Fiona Yull. Investigating the role of non-canonical NF-kappaB signaling in tumor cells and macrophages in ovarian cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4973.