CD4 and hepatocellular carcinoma: Naïve CD4+ T cells can differentiate into various subsets, such as (1) inflammatory Th1 cells, which promote anti-tumor activity through IFN-γ and TNF-α (94), (2) Th2 cells that may contribute to tumorigenesis and tumor progression (95, 96), (3) Th17 cells that have been associated with poor prognosis in hepatocellular carcinoma and thyroid cancer (97), and (4) regulatory T cells that suppress immune responses in the TME (98).