PLK1 and neoplasm: Most of them, including CDK1 (21), CDK4 (27), BUB1 (53), BUB1B (54), CCNA2 (55), CCNB1 (56), CCNB2 (39), CDC6 (57), MAD2L1 (58), MCM6 (59), and PLK1 (60) have been already reported to be associated with cell cycle-related proliferation and tumor differentiation.