CDK4 and neoplasm: ARID1A is believed to function as a tumor suppressor and deletion of ARID1A can lead to tumor formation.[46] The I1485fs*5 mutation results in truncation of the protein and similar truncations have been predicted to be inactivating.[46] ARID1A mutations have been reported in HCC in the COSMIC database.[7] CCND1 encodes Cyclin D1, which interacts with the cyclin-dependent kinases CDK4 and Cdk6, resulting in inactivation of RB1 and progression of the cell cycle.