Studies have reported many key targets associated with HCC, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) (13), programmed cell death-1 and its ligands (PD-1/PD-L1) (14), hypoxia-inducible factor (HIF) (15), and deubiquitinases (DUBs) (16). The gene discussed is PDCD1; the disease is hepatocellular carcinoma.