RB1 and cancer: These results raise the question of whether CDK4/6-mediated phosphorylation and inactivation of pRB also suppress PD-L1 expression, a possibility that is inconsistent with observations that multiple oncogenic alterations such as MYC, RAS, PIK3CA activation, and NF1 and TP53-loss induce PD-L1 to promote immune-evasion and cancer progression [31].