CDK4 and neoplasm: Regarding T cells, it was shown that treatment with CDK4/6i could repress regulatory T cells (Treg) proliferation [79,106,107,108], activate CD8+ T cells [79,106,109,110,111] and increase infiltration of effector T cells (Teff) on tumor microenvironment (TME) via the upregulation of the nuclear factor of activated T cells (NFAT) signaling [104,107].