CDK4 and neoplasm: Besides, CDK4/6 inhibitors could markedly and selectively reduce the immunosuppressive Tregs population.111 This preference of CDK4/6 inhibitor may be attributed to the higher expression level of RB by Tregs (3.1-fold higher in Tregs than in CD8+ T cells,484) a key modulator of CDK4/6 pathway.485 The inhibition of CDK4/6 in tumor cells also increases PD-L1 protein levels,481 which could be one of the mechanisms leading to the resistance of CDK4/6 inhibitor via evasion of immune checkpoints surveillance.