CDK4 and cancer: CDKN1A, considered to be among the most CKIs, is an integral checkpoint of the P53 signaling pathway with respect to G1/S transition through the inhibition of the function of kinases, for instance, CyclinD/CDK4, CyclinD/CDK6, as well as CyclinE/CDK232,33, playing different kinds of function to inhibit the cell progression in typical as well as cancer cells, in addition to being downregulated in various cancers34–37.