Abstract 3968: Class I HLA-independent lysis of cancer cells by tumor-infiltrating CD8 T cells

Abstract T cell-based therapies have transformed cancer treatment, although intrinsic or acquired resistance develops in nearly half of the patients. Tumor-infiltrating CD8+ T lymphocytes (TILs) are key determinants of anti-tumor immunity by secretion of cytotoxic granules, such as granzymes and perforin, and effector cytokines, such as TNFa and IFNg. A deep understanding of how CD8+ TILs eliminate cancer cells will help identify resistance mechanisms and develop new therapeutic strategies. Here, we demonstrate that TILs eliminated matched melanoma cells in a time and dose-dependent manner but in a class I HLA-independent fashion. Specifically, blocking class I HLA-TCR interaction either by the deletion of B2M (resulting in loss of class I HLA surface expression) or TCR genes did not alter the activity of these TILs. We further confirmed that TIL-mediated killing is contact-dependent. After excluding the potential roles of CD1d and MR1-restrictive T cells, gamma delta T cells, and NKG2D in TIL-mediated killing, a whole-genome CRISPR/Cas9 screen was performed in cancer cells. We identified that genes involved in JAK-STAT and cell-extrinsic apoptosis pathways are necessary for TIL-mediated killing. Together, these findings demonstrate that expanded CD8 TILs from melanoma patients are capable of eliminating melanoma cells via a novel, class I MHC-independent mechanism by coactivation of both JAK-STAT and cell-extrinsic apoptosis pathways. Citation Format: Hongyan Xie, Aiping Jiang, Jonathan Perera, Aonkon Dey, Neal Smith, Moshe Sade-Feldman, Robert T. Manguso, Nir Hacohen, Russell W. Jenkins. Class I HLA-independent lysis of cancer cells by tumor-infiltrating CD8 T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3968.