Clinical outcomes and influencing factors of PD-1/PD-L1 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has an increasing incidence worldwide, and the global 5-year survival rate ranges from 5–30%. In China, HCC seriously threatens the nation's health; the incidence of HCC ranks fourth among all theriomas, and the mortality rate is the third highest worldwide. The main therapies for HCC are surgical treatment or liver transplantation; however, most patients with HCC will experience postoperative recurrence or metastasis, eventually resulting in mortality. As for advanced or unresectable HCC, the current appropriate treatment strategy is transarterial chemoembolization; however, limited therapeutic effect and natural or acquired drug resistance affect the efficacy of this approach. Previous studies have demonstrated that PD-L1 expression on host cells and myeloid cells plays an important role in PD-L1 blocked-mediated tumor regression. Thus, further research on programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) is required. Countries including the United States, France, Britain and China have developed PD-1/PD-L1 blockers, including nivolumab, pembrolizumab, cemiplimab, atezolizumab, avelumab, durvalumab, toripalimab, sintilimab and camrelizumab. Notably, all of these blockers have therapeutic effect and influencing factors in HCC. Factors that influence the clinical outcome of PD-1 have also been discovered, such as inflammatory genes, specific receptors and signaling pathways. The discovery of these factors will help to identify novel methods, such as combination treatment, to decrease the influence of other factors on the efficacy of PD-1/PD-L1. Sorafenib and lenvatinib have been approved for first-line treatment for patients with advanced HCC. When first-line treatment frequently fails, pembrolizumab and ipilimumab plus nivolumab are used following sorafenib (but not lenvatinib) treatment in advanced HCC. Thus, tumor immunotherapy using PD-1/PD-L1 blockers exhibits promising outcomes for the treatment of HCC, and more novel PD-1/PD-L1 inhibitors are being developed to fight against this disease. The present review discusses the clinical results and influencing factors of PD-1/PD-L1 inhibitors in HCC to provide insight into the development and optimization of PD-1/PD-L1 inhibitors in the treatment of HCC.