Abstract 6817: Control of breast cancer via pro-resolving mediators

Abstract Tumor recurrence is the principal cause of mortality in breast cancer, yet the underlying mechanisms are not well understood. Anti-estrogen therapy, including tamoxifen, reduces tumor burden by inducing apoptosis and necrosis of cancerous tissue. The resulting cellular debris may stimulate tumor growth by disrupting inflammation resolution and creating pro-inflammatory and pro-tumorigenic microenvironments. Compared to estrogen receptor (ER) -positive breast cancer, ER-negative behaves aggressively, and patients have a poor prognosis due to the lack of treatment options. Here, we demonstrate that breast tumor cells killed by cytotoxic anti-estrogen therapy or chemotherapy (“tumor cell debris”) stimulate primary tumor growth when co-injected with a subthreshold (nontumorigenic) inoculum of tumor cells by triggering a macrophage-derived pro-inflammatory and pro-angiogenic “cytokine storm. ” Thus, tumor cell debris is a critical risk factor for aggressive breast cancer growth. To assess whether stimulating the clearance of debris would impact breast cancer progression in vivo, we utilized maresin 1 (MaR1), maresin conjugates in tissue regeneration (MCTR1, MCTR2) and protectin conjugates in tissue regeneration (PCTRs), which are specialized pro-resolving lipid autacoid mediators (SPMs). We treated established models of ER-positive (EO771) and negative (4T1) breast cancer. Each maresin sharply reduced tumor growth in debris-stimulated and spontaneous (e. g. MMTV-PyMT) breast cancer models at nanogram concentrations without toxicity. Notably, PCTR1 inhibited orthotopic triple-negative (4T1) growth and proliferation compared to chemotherapy (paclitaxel) or immunotherapy (anti-cytotoxic T-lymphocyte-associated protein 4, CTLA4). Similarly, PCTR1 alone or in combination with chemotherapy (paclitaxel) reduced gene expression and protein levels of pro-angiogenic factor CXCL12/SDF1 in the ER-negative (4T1) tumor microenvironment. In ER-positive (EO771), a triple combination of PCTR1, chemotherapy (paclitaxel), and immunotherapy (anti-CTLA4) treatment potentiated the immune checkpoint blockade. Maresins also stimulated macrophage phagocytosis of therapy-generated breast tumor cell debris, inhibited tumor angiogenesis, and dampened a therapy-induced cytokine storm, including TNF-α, MIP-2/CXCL2, CCL2/MCP-1, IL- 1ra/IL-1F3, and G-CSF. Expression of SPM receptors (e. g. resolvin D1 (RvD1) receptor ALX/FPR2, resolvin D2 (RvD2) receptor GPR18, maresin 1 (MaR1) receptor LGR6, and resolvin E1 (RvE1) receptor ChemR23) were specifically identified in breast cancer tissue. Taken together, the maresin and protectin pathway mediators may represent a new therapeutic approach to stimulate the resolution of inflammation in breast cancer. Citation Format: Sarina A. Virani, Michael Gillespie, Haixia Yang, Diane R. Bielenberg, Mark W. Kieran, Sui Huang, Charles N. Serhan, Dipak Panigrahy. Control of breast cancer via pro-resolving mediators abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 6817.