CDK4 and Alzheimer disease: Cyclin Dependent Kinases (i.e.,CDK2, CDK4 and CDK5), increase APP’s phosphorylation at Thr668 which increases Aβ production and APP proteolysis by activated caspases during the cell cycle.76,77, Cyclin D-CDK4 and Cyclin E CDK2 are among the Cdks that control G1 progression, and it is generally believed that in AD, neurons are forced out of G0 quiescence to G1 reentry resulting in lethal cell cycles (Park et al., 2000; Majd et al., 2019).