Both p21 and p27 have been identified as mediators of tumor suppression through G1 or G2 arrest, involving binding to CyclinA/cyclin-dependent kinase (CDK) 2, CyclinE/CDK2, and CyclinD/CDK4/6 complexes [35, 36, 52]. The gene discussed is CDKN1B; the disease is neoplasm.