CD4 and cancer: Numerous studies have shown that TCS could directly inhibit the proliferation and apoptosis of cancer cells by regulating the expression of Bcl-2 [9], inducing S-phase cell cycle arrest in cancer cells [10], inhibiting tumor dysplasia-related signaling pathways [11], increasing the expression or activation of caspase family proteins [12,13,14], etc. In physiological conditions, TCS could regulate the immune status of the body by regulating the CD4+/CD8+ T-cell ratio and producing related immune cytokines in peripheral blood [15].