CD4 and neoplasm: However, recent data have shown that cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, now standard of care for the treatment of metastatic luminal-like tumors, promote antitumor immunity in preclinical models by increasing tumor antigen presentation, IFN-γ production, and CD8+ T-cell expansion, and by inhibiting CD4+ T regulatory (Treg) cell proliferation9.