Unbalanced Glutamine Partitioning between CD8T Cells and Cancer Cells Accompanied by Immune Cell Dysfunction in Hepatocellular Carcinoma

Abstract

Glutamine metabolism is critical both for the proliferation of cancer cells and the activation of CD8T cells to kill cancer cells. We aim to explore the relationship between the glutamine metabolism of CD8T cells and cancer cells and tumor immunity in the tumor microenvironment. In a TCGA cohort, we found that patients with high scores of glutamine-metabolism-related genes showed poor prognoses, and that a high score of glutamine-metabolism-related genes was an independent risk factor for HCC patients. In single-cell RNA-seq data, we found that, in some patients, the glutamine metabolism gene scores of tumor cells were significantly higher than those of CD8T cells, while decreased ratios of CD8-Tef-GZMA and suppressed tumor-killing activity of CD8-Tef-APOC2 were observed. A further genetic dynamics pseudotime analysis suggested that immune remodeling of these two subpopulations was accompanied by metabolic reprogramming. CD8-Tef-APOC2 in the dominant group tended to metabolize exogenous lipids, while the metabolic program of CD8-Tef-GZMA in the nondominant group was characterized by amino acid and endogenous lipid synthesis. In addition, we found that the glutamine metabolism inhibitor JHU083 promoted the proliferation of CD8T cells and improved the efficacy of PD-1 blockers. We proposed a new tool to quantify the glutamine partitioning between tumor cells and CD8T cells, through which the unique immune microenvironment could be identified at the transcriptome level. Furthermore, the simultaneous destruction of the glutamine metabolism in tumor cells and CD8T cells facilitated the enrichment of tumor-infiltrating CD8T cells and enhanced the efficacy of immunotherapy.