Unique T cell populations define immune-inflamed Hepatocellular Carcinoma

Abstract Background & Aims The characterization of T cells infiltrating hepatocellular carcinoma (HCC) provides information on cancer immunity and also on selection of patients with precise indication of immunotherapy. The aim of the study was to characterize T-cell populations within tumor tissue and compare them with non-neoplastic liver tissue as well as circulating cells of the same patients. Methods The presence of unique cell populations was investigated in 36 HCC patients by multidimensional flow cytometry followed by tSNE analysis. Functional activity of tumor-infiltrating T cells was determined after activation by PMA and ionomycin. Results Within the tumor there were more cells expressing CD137 and ICOS, than in non-neoplastic liver tissue, possibly following recent antigenic activation. These cells contained several populations including: i) functionally impaired, proliferating CD4+ cells co-expressing ICOS and TIGIT; ii) functionally active CD8+ cells co-expressing CD38 and PD1, and iii) CD4-CD8-double negative TCR αβ and γδ cells (both non-MHC restricted T cells). When the identified clusters were compared with histological classification performed on the same samples, an accumulation of activated T cells was observed in immune-inflamed HCC. The same analyses performed in 7 patients under Nivolumab treatment showed a remarkable reduction in the functionally impaired CD4+ cells, which returned to almost normal activity over time. Conclusions Unique populations of activated T cells are present in HCC tissue, whose antigen specificity remains to be investigated. Some of these cell populations are functionally impaired and Nivolumab treatment restores their responsiveness. The finding of ongoing immune response within the tumor shows which lymphocyte populations are impaired within the HCC and identifies the patients that might take benefit from immunotherapy.