Abstract 5157: ATRA Treatment Induces an Interferon Response to Reprogram the Immunosuppressive Tumor Microenvironment and Overcomes Resistance to Immune Checkpoint Inhibition in Murine Models of LKB1 Deficient Non Small Cell Lung Cancer

Abstract Lung cancer remains the deadliest form of cancer, claiming the lives of 1.8 million individuals worldwide in 2020. While treatment options have improved with the advent of immune checkpoint inhibitors (ICI), many patients do not respond to immunotherapy or develop resistance following initial response. A significant subset of non-small cell lung cancer (NSCLC) patients harbor 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 characterized by a predominance of neutrophils and an immune suppressive 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 (Kras G12D P53−/−Lkb1−/−; KPL) 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. We further observed that ATRA augmented anti-PD-1 efficacy in additional murine NSCLC models with or without LKB1 loss. To understand ATRA-mediated anti-tumor effects, we performed single cell RNA sequencing (scRNA-seq) of KPL murine tumors with or without 6 daily ATRA treatments. scRNA-seq analysis indicated a reduction of neutrophils as well as an enrichment in T cell and natural killer (NK) cell populations in the TME. Furthermore, scRNA-seq analysis revealed elevated expression of interferon (IFN) downstream genes in multiple immune subpopulations in the TME. Preliminary ex vivo studies indicated that ATRA increases NOX2 levels, intracellular reactive oxygen species (ROS), and IFN signaling in the myeloid-derived suppressor cells (MDSC) of KPL tumors. Our findings suggest that ATRA may reshape the TME by activating IFN signaling in multiple cell subtypes to sensitize resistant tumors to ICI immunotherapy. Citation Format: William P. Crosson, Rui Li, Ramin Salehi-Rad, Raymond J. Lim, Jensen Abascal, Bitta P. Kahangi, Edgar Perez Reyes, Michael Oh, Camelia Dumitras, Nico Edgar, Ryan Chew, Rashel Jacobo, Zhe Jing, Kostyantyn Krysan, Linh M. Tran, Steven Dubinett, Bin Liu. ATRA treatment induces an interferon response to reprogram the immunosuppressive 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 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 5157.