CDKN3 is a member of the dual specificity protein phosphatase family that acts as a cyclin-dependent kinase inhibitor. CDKN3 has been shown to interact with and dephosphorylate specifically the CDK2 kinase thereby preventing it’;s activation. CDKN3 has been reported to be deleted, mutated, or overexpressed in several kinds of cancers. Increased expression of CDKN3 leads to increased levels of kinase-associated phosphatase activity that inhibits the G(1)/S transition of the cell cycle by dephosphorylating the cyclin-dependent kinases.