Abstract B090: ATRA reprograms neutrophils in the tumor microenvironment and overcomes resistance to immune checkpoint inhibition in murine models of LKB1-deficient non-small cell lung cancer

Abstract Lung cancer continues to be the leading cause of cancer-related deaths, projected to claim over 125,000 lives in the United States in 2024. While therapeutic options have improved with the introduction of immune checkpoint inhibitors (ICI) to the clinic, many patients do not respond to immunotherapy or develop resistance following initial response. A significant subset of non-small cell lung cancer (NSCLC) patients harbors somatic co-mutations in Kirsten rat sarcoma virus (KRAS) and Liver kinase 1 [LKB1, also known as serine/threonine kinase 11 (STK11)] genes, whose tumors are described by an immunosuppressive tumor microenvironment (TME) that are resistant to ICI. Our studies revealed that all-trans retinoic acid (ATRA), a metabolite derived from vitamin A, sensitized a murine model of NSCLC with increased tumor mutational burden (Kras G12D P53 -/- Lkb1 -/- ; KPL-3M) to PD-1 blockade. The ATRA and anti-PD-1 combination therapy improved local and systemic T cell activation and generated systemic tumor-specific immunity. To investigate ATRA-mediated anti-tumor effects, we conducted single cell RNA sequencing (scRNA-seq) of KPL-3M murine tumors with or without ATRA treatment. scRNA-seq analysis revealed a reduction of neutrophils as well as an enrichment in T cell and natural killer (NK) cell populations in the TME. Furthermore, scRNA-seq trajectory and RNA velocity analysis suggested an enrichment in neutrophil clusters associated with differentiation and effector function. ATRA increased expression of maturity markers on neutrophils isolated from KPL-3M tumors as well as neutrophils differentiated in vitro from murine bone marrow. Additionally, preliminary ex vivo studies indicate that ATRA increases NOX2 levels, intracellular reactive oxygen species (ROS), and interferon (IFN) response signaling in the neutrophils in KPL-3M tumors. Our findings suggest that ATRA may reshape the TME by altering neutrophil composition to sensitize resistant tumors to ICI immunotherapy. Citation Format: William P Crosson, Rui Li, Ramin Salehi-Rad, Bitta P Kahangi, Samantha Chin, Raymond J Lim, Jensen Abascal, Edgar Perez Reyes, Michael Oh, Camelia Dumitras, Nico Edgar, Ryan Chew, Rashel Jacobo, Adam Tfayli, Kostyantyn Krysan, Linh M Tran, Steven M Dubinett, Bin Liu. ATRA reprograms neutrophils in the tumor microenvironment and overcomes resistance to immune checkpoint inhibition in murine models of LKB1-deficient non-small cell lung cancer [abstract]. In: Proceedings of the AACR IO Conference: Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2025 Feb 23-26; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(2 Suppl):Abstract nr B090.