Abstract B088: Axl regulation of NK cell activity creates an immunosuppressive tumor immune microenvironment in head and neck cancer

Abstract Head and neck cancer (HNC), the sixth most common cancer worldwide, utilizes many strategies to evade the immune system, including manipulation of immune cell composition in the tumor immune microenvironment (TIME). Previous studies in our laboratory have demonstrated that the receptor tyrosine kinase Axl is a crucial driver of proliferation, survival, metastasis, and therapeutic resistance in HNC. This study explores the role of tumor-bound Axl in immune evasion in HNC. Using a series of Axl CRISPR knockout (AxlKO) cell lines (MOC2-398, MOC2-399, MOC2-400) from the immunologically "cold" MOC2 mouse model of HNC, we found that Axl loss significantly delayed tumor growth in immunocompetent C57BL/6 mice. Further, Axl loss led to a marked reduction of immunosuppressive cells- including MDSCs, Tregs, B cells, and neutrophils- accompanied by an enhanced infiltration of cytotoxic immune cells such as CD8+ T cells and NK cells within the TIME. To identify the immune cell population(s) responsible for the observed tumor growth delay, AxlKO tumors were implanted in immune-deficient mouse models, including NCG and athymic nude mice. While AxlKO tumor growth in athymic nude mice, which lack T-cells, was unchanged, tumor growth in NCG mice-which notably lack NK cells- was “rescued,” suggesting that NK cells may critically mediate the slowed growth of AxlKO tumors. These observations led us to hypothesize that Axl modulates NK cell recruitment and activation within the TIME. To test this, we first assessed in vitro NK cell cytotoxicity and found that Axl loss in tumor cells appeared to significantly enhance NK cell cytotoxicity. Further, NK cell depletion studies in C57BL/6 mice bearing AxlKO tumors demonstrated that the lack of NK cell "rescued" tumor growth in AxlKO models. To investigate if Axl regulates cytokines and chemokines relevant to NK cell recruitment and activation, we conducted analyses using NanoString nCounter, Luminex, and quantitative PCR. These revealed downregulation of NK modulators CD73 and CCL2, along with increased expression of CCL5 and CXCL10 in AxlKO tumor cells. These findings suggest that Axl regulates key immunomodulators to inhibit NK cell recruitment and activation, creating an immunosuppressive TIME that promotes HNC tumor growth. Citation Format: Regan L Harmon, Kourtney L Kostecki, Mari Iida, Madelyn A Harris, Bridget E Crossman, Justine Bruce, Ravi Salgia, Deric L Wheeler. Axl regulation of NK cell activity creates an immunosuppressive tumor immune microenvironment in head and neck 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 B088.