Abstract 1416: Resolvins enhance immunotherapy to induce Fanconi anemia tumor regression via inflammation resolution

Abstract Fanconi anemia (FA) is a disorder characterized by early-onset solid tumors unresponsive to chemotherapy and radiation. Unresolved inflammation is a hallmark of FA, the mechanisms underlying the initiation and resolution of inflammation in FA are poorly characterized. We hypothesized that FA tumor progression is controlled by dysregulated resolution metabolomes and a systemic pro-inflammatory eicosanoid storm of inflammation-initiating mediators. Using a novel transplantable murine FA tumor model, we show that Fancc-/- HNSCC (head and neck squamous cell carcinoma) progression disrupts the resolution of inflammation via an imbalance between specialized pro-resolving lipid mediators (SPMs) and eicosanoids. Fancc-/- tumor-bearing mice exhibited an increase in eicosanoids, including leukotriene B4 (LTB4) and thromboxane B2 (TXB2) in the spleen and a 113% increase in prostaglandin E metabolite (PGEM), a marker of PGE2 production, in the plasma compared to non-tumor-bearing (NT) mice. Fancc-/- tumor-bearing mice exhibited a loss in the SPM/LTB4 ratio including RvD1/LTB4, RvD2/LTB4, and MaR1/LTB4, compared to NT mice. Given the activity of immune checkpoint blockade in mismatch repair deficient tumors including head and neck cancers, immunotherapy may be relevant to FA-induced cancers. Importantly, the number of absolute T cells and CD4+ T cell function is preserved in individuals with FA. We combined stimulation of the resolution of inflammation (i.e., treatment with RvDs) with immunotherapy in a new transplantable murine FA tumor model. While treatment with RvD4, RvD5, or anti-PD1 immunotherapy alone delayed tumor growth compared to control at treatment day 20, the tumors did escape monotherapy by treatment day 30. Remarkably, RvD4 or RvD5 combined with anti-PD1 immunotherapy induced sustained Fancc-/- tumor regression. Moreover, RvD4 and/or anti-PD1 immunotherapy inhibited orthotopic Fancc-/- tumor growth compared to control. Resolvins and immune checkpoint blockade synergistically induced Fancc-/- tumor regression via macrophage phagocytosis of apoptotic debris, counter-regulation of pro-angiogenic cytokines, and inhibition of angiogenesis. Triggering Receptor Expressed on Myeloid cells-2 (TREM2)-antagonism combined with resolvins and immunotherapy restored SPM/eicosanoid ratios in Fancc−/- tumor-bearing mice to pre-cancer levels. SPMs and eicosanoids provide potential early biomarkers and biological targets in FA-induced cancer progression. Stimulating the resolution of inflammation via pro-resolution lipid mediators to enhance immunotherapy is a novel host-centric therapeutic approach to prevent FA-induced cancer progression via debris clearance and cytokine suppression. These results provide evidence for targeting the resolution of inflammation via resolvins to enhance immunotherapy to prevent and/or reverse FA-induced cancer progression. Citation Format: Katherine Quinlivan, Haixia Yang, Diane R. Bielenberg, Susanne I. Wells, Charles N. Serhan, Dipak Panigrahy. Resolvins enhance immunotherapy to induce Fanconi anemia tumor regression via inflammation resolution [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(6_Suppl):Abstract nr 1416.