PLK1 and hepatocellular carcinoma: Seven genes (CDKN2A, HAT1, HSP90AA1, MYCN, PLK1, SQSTM1, and TNFRSF21) were upregulated in HCC tissues and were high-risk genes (HR >1), while 2 genes (KLF9, NDRG2) were downregulated in HCC tissues and were low-risk genes (HR <1).