Clinically, the tumor-infiltrating levels of cytotoxic CD4 cell, mucosal associated invariant T (MAIT) cell, and exhausted CD8+ T cell were found to be reduced in not only primary HCC tissues with vascular invasion but also in recurrent HCC tissues, suggesting that reduced infiltrating levels of these T cells might be an indicator of poor prognosis. This evidence concerns the gene CD4 and hepatocellular carcinoma.