PDCD1 and hepatocellular carcinoma: To supplement the development of VEGF/VEGFR inhibitors for HCC therapy, new targets are currently being investigated, such as PD-1/PD-L1 [35, 36], CTLA-4 [37, 38], c-Met [39], TGF [40], PI3K/PTEN/Akt/mTOR [41], and Hedgehog [42] etc. Additionally, dysregulation of many signaling pathways has been linked to HCC development and progression, so researchers have sought to derive novel target genes and drug candidates related to these pathways.