Abstract 2124: ATRA mediated inhibition of myeloid-derived suppressor cells overcomes resistance to immune checkpoint inhibition in murine models of LKB1-deficient non-small cell lung cancer

Abstract

Abstract Lung cancer remains the deadliest form of cancer, claiming the lives of 1.8 million 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 patients harbor somatic mutations in both Kirsten rat sarcoma virus (KRAS) and Liver kinase 1 [LKB1, also known as serine/threonine kinase 11 (STK11)] genes. LKB1 loss has been identified as a driver of primary resistance to ICI therapy. Tumors from patients that possess these mutations are characterized by an increase in the population of myeloid derived suppressor cells (MDSCs). MDSCs are thought to play a critical role in promoting tumor progression by blocking the tumor killing function of cytotoxic T cells in the tumor microenvironment (TME). Our studies revealed all-trans retinoic acid (ATRA), a metabolite derived from vitamin A, sensitized murine models of non-small cell lung cancer (NSCLC) with LKB1 and KRAS co-mutations to PD-1 blockade. Combination therapy with anti-PD-1 and ATRA improved local and systemic T cell proliferation and generated systemic tumor-specific immunity. We observed that ATRA augmented anti-PD-1 efficacy in additional murine NSCLC models. We demonstrated that ATRA suppresses tumor growth through the inhibition of immunosuppressive MDSCs in the TME, and preliminary data indicates that ATRA increases intracellular reactive oxygen species (ROS) and IFN signaling in MDSC. Our findings implicate MDSCs as a potential mediator of immunosuppression in Lkb1-deficient NSCLC and provide a rationale for utilizing ATRA in combination with anti-PD-1 therapy in patients with Lkb1-deficient NSCLC refractory to ICIs. * B. Liu and S. M. Dubinett contributed equally to this work Citation Format: William P. Crosson, Rui Li, Ramin Salehi-Rad, Raymond J. Lim, Jensen W. Abascal, Bitta P. Kahangi, Edgar Perez Reyes, Camelia Dumitras, Zhe Jing, Kostyantyn Krysan, Linh M. Tran, Bin Liu, Steven M. Dubinett. ATRA mediated inhibition of myeloid-derived suppressor cells 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 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2124.