Abstract C035: Stromal AXL deficiency drives a Th1/M1-oriented immune response and promotes cell death in OSSC

Abstract The tumor microenvironment has an important role in cancer progression. AXL is the “A” in the TAM family of receptor tyrosine kinases that influences the immune response and efferocytosis. It is frequently overexpressed in cancer and considered an oncogene in various types of solid tumors. This study investigates the influence of AXL receptor expression by stromal and immune cells in the tumor microenvironment on the progression, response to cisplatin and tumor immunity in oral squamous cell carcinoma (OSCC). Experimental tumors were induced in WT and AXL KO mice in a syngeneic orthotopic model of OSCC by injecting 50,000 MOC2 cells resuspended in 100 uL of Hanks/Matrigel directly into the floor of the mouth. Half of the mice were administered an intra-peritoneal non-curative dose of cisplatin (5 mg/Kg) and mice were euthanized after two weeks (humane endpoint for early euthanasia was the loss of 20% of the initial body weight). Experimental tumors were dissected, weighted, and measured. Samples were enzymatically and mechanically dissociated for immunophenotyping by flow cytometry. Bulk RNAseq was used for transcriptome analysis and TUNEL staining was used for in situ assessment of apoptosis. AXL KO mice tended to have smaller tumors and increased TUNEL staining, indicating accumulation of apoptotic cells. Total leukocyte (CD45+ cells) infiltration was lower in AXL KO mice, with less CD8+ T cells. There was a relative increase in infiltration of CD4+ T cells, but markedly lower prevalence of Tregs (CD4+FOXP3+). Neutrophil infiltration (CD11b+Ly6g+) was markedly increased in AXL KO mice. Cisplatin treatment did not affect infiltration of CD4+ and CD8+ cells in AXL KO mice (CD8+ cells were reduced in WT mice), but further increased infiltration of neutrophils (CD11b+Ly6G+) and the relative proportion of macrophages (CD11b+F4/80+) expressing CD80. Principal component analysis of transcriptomic data indicated a significant heterogeneity in gene expression between AXL KO and WT mice (3,879 differentially expressed genes), with more pronounced changes induced by cisplatin treatment in AXL KO mice. Genes upregulated in AXL KO mice associated with activation of anti-tumoral immunity and immunogenic cell death included Ccl2, Ifng, Il33, Cd8a, Gsdmd, Casp1, Nlrp3, Cd86, Cd69, FasL. Lack of AXL in stromal cells in the tumor microenvironment skews tumor immunity towards Th1/M1-like phenotype, enhances infiltration of innate immune cells and increased the prevalence of apoptosis, suggesting an impairment of efferocytosis and increase in immunogenic cell death. Citation Format: Camyla Rodrigues Nascimento, Alvaro Formoso Pelegrin, Natalie Aparecida. Rodrigues Fernandes, Ianny Brum Reis, Keith Kirkwood, Carlos Rossa Junior. Stromal AXL deficiency drives a Th1/M1-oriented immune response and promotes cell death in OSSC [abstract]. In: Proceedings of the AACR Immuno-Oncology Conference (AACR IO): Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2026 Feb 18-21; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2026;14(2 Suppl):Abstract nr C035.