PLK1 and hepatocellular carcinoma: FoxM1 directly interacts with many HCC-related molecules such as cyclin B1(CNNB1), protein regulator of cytokinesis (PRC1), polo-like kinase 1 (PLK1), cyclin A2 (CCNA2), BUB mitotic checkpoint serine/threonine kinase B (BUB1B), centromere protein F (CENPF), cell division cycle associated protein 8 (CDCA8), aurora kinase A (AURKA), marker of proliferation Ki-67 (MKI67), centromere protein A (CENPA) and MMP9 (Figure 6c).