CDKN2A and neoplasm: (Giarrè et al., 2001; Li et al., 2011) Protein p16, a tumor suppressor from the Ink4 family, encoded by CDKN2A gene (9p21.3) prevents progression into S phase of cell cycle by inhibits cyclin D dependent protein kinases (CDK4 and CDK6) therefore maintaining retinoblastoma protein (pRb) in its hypophosphorylated state which prevents its dissociation from E2F transcription factor.