CD4 and hepatocellular carcinoma: Studies have shown that serine inhibits the growth of transplanted hepatocellular carcinoma (HCC) in mice and reduces the CD4+CD25+Foxp3+ proportion of Treg and the expression levels of Foxp3 and TGFβ mRNA, and enhanced the body’s antitumor immune response by inhibiting the TGF/SMAD signaling pathway [184].