PLK1 and hepatocellular carcinoma: Ten of the 13 cell cycle genes, including SGO1 (10), HJURP (11), CENPA (12), GINS1 (13), EZH2 (14), NUF2 (15), PLK1 (16), HMMR (17), E2F2 (18, 19), and CDCA8 (20), have been confirmed by previous studies, indicating that their overexpression could increase the malignant phenotype of HCC (Figures 9A, B).