Abstract B005: Tumor-derived extracellular vesicles induce intrinsic apoptosis of activated T cells by early transcriptional activation of cellular stress response genes

Abstract Tumor-derived small extracellular vesicles or TEX, circulate freely, carry and deliver signals that induce immune suppression leading to demise of activated CD8+ effector T cells in vitro and in vivo in tumor-bearing animals. The sequence of genetic/molecular changes induced by TEX in these T cells resulted in dose-dependent suppression of growth, inhibition of cytokine release and intrinsic apoptosis. Early upregulation of IRE1α, PERK, CHOP, ATF6 proteins and MAPK signaling activation in CD8(+) Jurkat cells were initially documented by immunoblots. Changes in cellular metabolism, e.g., activation of the MAPK pathway evidenced by phosphorylation of p38 MAPK (Thr180/Tyr182), SAPK/JNK (Thr183/Tyr185), and ERK1/2 (Thr202/Tyr204), as well as dephosphorylation of Raf-1 (Ser338) were noted in recipient Jurkat cells. Mitochondrial injury (leakage of cytochrome C, AIF, and Smac into cytosol and a loss of survival proteins, Bcl-2 and Mcl-1, was evident within 15min of co-incubation with TEX. RNAseq was performed with CD8(+) Jurkat T cells co-incubated with TEX for 2h or 4h. RNA seq of T cells responding to TEX showed massive transcriptional reprogramming. After 4h of TEX signaling, there were 876 DEGs among 11,871 identified genes. In silico profiling of activated genes was correlated with functional alterations. The DEGs regulated 19 major metabolic pathways in T cells, and “Cellular responses to stress” was the most significantly enriched pathway followed by “Cell Death & Autophagy”, “Cellular Metabolism”, “Immune Response.” TEX entering T cells induced DAMPs characterized by the initial upregulation of transcripts for stress responses genes followed by activation of genes regulating the major metabolic pathways, mitochondrial dysfunction, apoptosis, and/or autophagy. The fate of T cells was determined by the strength of TEX signaling. TEX inducing DAMPs on entry into T cells emerge as a major mechanism of immune evasion in cancer. Citation Format: Theresa L. Whiteside, Jie Han, Alicja Gluszko, Monika Pietrowska, Joanna Polanska. Tumor-derived extracellular vesicles induce intrinsic apoptosis of activated T cells by early transcriptional activation of cellular stress response genes [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Mechanisms of Cancer Immunity and Cancer-related Autoimmunity; 2025 Sep 24-27; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(9 Suppl):Abstract nr B005.