Metabolic dysfunction and DNA damage of exhausted tumor-infiltrating CD8 T-cells in hepatocellular carcinoma

Introduction CD8 T-cells are the main effectors of the adaptative immune system and are characterized by cytotoxic and regulatory functions, thus constituting the most relevant line of defense against viral infections and tumors. The tumor immune microenvironment is able to release soluble factors or exert other regulatory mechanisms capable of intervening on different immunological pathways. Functional defects of CD8 T-cell response have been described in HCC showing correlation with disease stage and clinical outcome, however the molecular bases of CD8 cell dysfunction are still not completely known. Aim the aim of this study was to define the molecular profile of tumor-infiltrating CD8 T-cells, their metabolic, phenotypic and functional alterations associated with CD8 T-cell exhausted phenotype. Materials and Methods Results by comparison with CD8 cells from the non-tumorous counterpart, genomic profiling of tumor-infiltrating CD8 T-cells showed upregulation of several pathways among which hypoxic and oxidative stress response, DNA damage response and TGF-β pathway. We performed phenotypic analysis, staining tumor and liver infiltrating CD8 T-cells for CD103, CD39, PD-1, TIM-3, TIGIT, CXCR6. An enhanced expression of check point molecules such as PD-1, CD-39 and TIM-3 was evident in the tumor. Moreover, infiltrating CD8 cells showed depolarized mitochondrial membrane and higher levels of phosphorylation of the histone H2AX and ATM suggesting dysfunctional mitochondria and DNA damage, in agreement with the genomic profiling of CD8 T-cells. Conclusions the discovery of metabolic and functional alterations of tumor infiltrating CD8 T-cells, provides the basis for further investigations aimed at identifying new therapeutic strategies to restore tumor-specific CD8 T cells response in HCC patients.