Molecular profile of tumor-specific CD8+ T cell hypofunction in cancer

Comparison of genome-wide mRNA expresson between tumor-infiltrating CD8+ T cells from the tumor (hypofunctional T cells) and periphery (functional T cells) Mechanisms of self-tolerance often result in CD8+ tumor-infiltrating lymphocytes (TIL) with a hypofunctional phenotype incapable of tumor clearance. Using a solid tumor model in mice, we found that CD8+ T cells became tolerized in less than 24 hours in an established tumor environment. To define the collective impact of pathways suppressing TIL function, we compared genome-wide mRNA expression of tumor-specific CD8+ T cells from the tumor and periphery. Notably, gene expression induced during TIL hypofunction more closely resembled self-tolerance than viral-exhaustion. Differential gene expression was refined to identify a core set of genes that defined hypofunctional TIL; these data comprise the first “molecular profile” of tumor-specific TIL that are naturally responding and represent a polyclonal repertoire. The molecular profile of TIL was further dissected to determine the extent of overlap and distinction between pathways that collectively restrict T cell functions. As suggested by the molecular profile of TIL, protein expression of inhibitory receptor LAG-3 was differentially regulated throughout prolonged late-G1/early-S phase of the cell cycle. Our data may accelerate efficient identification of combination therapies to boost anti-tumor function of TIL specifically against tumor cells. 4 samples, 3 biological replicates per group.