CDK4 and cancer: CDK inhibitors have long been evaluated as cancer therapeutics (Asghar et al. 2015; Canavese et al. 2012; Peyressatre et al. 2015; Shen et al. 2019).Currently, the third generation CDK4/6 dual inhibitors palbociclib, ribociclib, and abemaciclib have been approved by FDA for the treatment of breast cancer (Spring et al. 2019).