CDKN1B and neoplasm: The molecular mechanisms underlying the direct anti-tumor effect of several monoclonal antibodies have been investigated; for example, the anti-HER-2 antibody (Trastuzumab) and anti-EGFR antibody (Cetuximab) result in G1/S cell cycle arrest by upregulating the CDK inhibitor p27kip1 via multiple signaling pathways [12, 13].