Accordingly, Zhang and colleagues found an inverse relationship between CDK4 activity and PD-L1 expression on cancer cells, and showed that palbociclib or ribociclib treatment increased PD-L1 expression in a variety of in vitro and in vivo models, regardless of RB status, denoting that the RB/E2F axis was not responsible for this in these models. This evidence concerns the gene CDK4 and cancer.