CDK4 and cancer: However, epigenetic factors and genetic factors including the loss of cyclin D-CDK4/6 negative regulators, overexpression of cyclin D, amplification and/or mutation of CDK4/6, compromises the regulatory integrity of the CDKs leading to hyper complexation of the catalytic and regulatory unit and consequently un-control cell cycle progression, cancer initiation and developments [23,24,25].