Abstract 6168: CAF-mediated cancer immunotherapy resistance can be overcome via selective inhibition of NOX 2 and 4

Abstract Cancer-associated fibroblasts (CAFs) are a functionally heterogeneous population that constitutes tumor stroma. CAFs interact with cancer cells and immune cells by secreting various chemokines/cytokines, participating in extracellular matrix (ECM) remodeling and affecting the immune invasion in the tumor microenvironment (TME). Finally, CAFs promote tumor growth and induce resistance to chemotherapy or immunotherapy, making tumors more aggressive associated with poor prognosis in various types of solid tumors. The primary function of NADPH oxidases (NOXs) is to produce reactive oxygen species (ROS). NOX enzymes, which are clinically upregulated in CAFs, have been reported to be critical effectors of tumor fibrosis and immunosuppression of the TME. It suggests that modulation of CAF-mediated immunosuppression via NOX regulation could be a potential strategy for cancer immunotherapy. In this study, NOX2 and 4 are markedly increased in human pancreatic CAFs (pCAFs) compared to human pancreatic fibroblasts (PFs) and knockdown of NOX2 or 4 effectively decreased fibrosis-related markers and immune cytokines/chemokines in pCAFs, respectively. In order to confirm the importance of NOX in CAF functions, we utilized compound-19, a selective NOX inhibitor. Com-19 treatment significantly reduced the expression of fibrosis-related factors and immune cytokines/chemokines in pCAFs. In addition, com-19 inhibited monocyte infiltration and their differentiation into M2 macrophages in CAF-rich tumor-mimicking 3D spheroids in vitro. The in vivo efficacy was evaluated using a CAF-rich colorectal cancer mouse model. Com-19 inhibited tumor fibrosis and immune cytokines in CAF-rich tumors via NOX inhibition. Importantly, com-19 increased the intratumoral infiltration of CD8+ T cells, resulting in excellent synergistic tumor growth inhibition when co-administered with immune check inhibitors (ICIs) in the model which poorly responses to ICIs. Taken together, the results support that NOXs play a crucial role in CAF-mediated ICIs resistance in cancers and NOX inhibition can be a promising strategy to overcome the resistance. Com-19 effectively regulated the fibrotic and immune-suppressive properties of CAF-rich tumors via NOX inhibition. Therefore, com-19 can potentiate cancer immunotherapy by overcoming CAF-Mediated ICIs resistance. GLP safety/toxicity studies of com-19 have been completed and phase 1 clinical studies are scheduled in 1Q, 2025. Citation Format: Jihyun Um, Heesu Kim, Hyeji Jang, Eun Sil Lee, Sung Hwan Moon, Soo Jin Lee. CAF-mediated cancer immunotherapy resistance can be overcome via selective inhibition of NOX 2 and 4 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6168.