IFNγ-IL-17+ CD8 T cells contribute to immunosuppression and tumor progression in human hepatocellular carcinoma

IL-17-producing CD8 (Tc17) T cells have been shown to play an important role in infection and chronic inflammation, however their implications in hepatocellular carcinoma (HCC) remain elusive. In this study, we performed cytometry by time-of-flight (CyTOF) and revealed the distinctive immunological phenotypes of two IFN gamma(+) and IFN gamma(-) Tc17 subsets that were preferentially enriched in human HCC. Single-cell RNA-sequencing analysis further revealed regulatory circuits governing the different phenotypes of these Tc17 subsets. In particular, we discovered that IFN gamma(-) Tc17 subset demonstrated pro-tumoral characteristics and expressed higher levels of CCL20. This corresponded to increased tumor infiltration of T regulatory cells (Treg) validated by immunohistochemistry in another independent HCC cohort, demonstrating the immunosuppressive functions of IFN gamma(-) Tc17 subset. Most importantly, higher intra-tumoral proportions of IFN gamma(-) Tc17 were associated with poorer prognosis in patients with HCC and this was further validated in The Cancer Genome Atlas (TCGA) HCC cohort. Taken together, this compendium of transcriptomic and proteomic data of Tc17 subsets sheds light on the immunosuppressive phenotypes of IFN gamma(-) Tc17 and its implications in HCC progression.

Automated summary

In this study, IL-17-producing CD8 (Tc17) T cells were found to have distinct immunological phenotypes and regulatory circuits in hepatocellular carcinoma (HCC). The IFN gamma(-) Tc17 subset demonstrated pro-tumoral characteristics and higher expression of CCL20, which was associated with increased tumor infiltration of T regulatory cells (Treg) and poorer prognosis in HCC patients.