Several protein kinases [IKBKB, MAP2K6, TANK binding kinase 1 (TBK1), Rho-associated coiled-Coil containing protein kinase (ROCK2), TAO Kinase 3, CDK4, serine/threonine kinase (STK38), CDK5, non-receptor tyrosine kinase (ABL1), and checkpoint kinase (CHEK2)] were reportedly closely related to radioresistance in various cancers, while MAPK15, FYN, and WNK lysine-deficient protein kinase 1 (WNK1) still await further study on their functions in the radioresistance development of cancer cells. Here, CDK5 is linked to cancer.