CCND2 belongs to the highly conserved cyclin family, whose members are characterized by a dramatic periodicity in protein abundance through the cell cycle. Cyclins function as regulators of CDK kinases. CCND2 forms a complex with and functions as a regulatory subunit of CDK4 or CDK6, whose activity is required for cell cycle G1/S transition. CCND2 has been shown to interact with and be involved in the phosphorylation of tumor suppressor protein Rb. High level expression of CCND2 was observed in ovarian and testicular tumors.