Immune checkpoint blockade for the treatment of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers with a high recurrence rate. Currently, tyrosine kinase inhibitors (TKIs) are the first-line treatment for cases refractory to conventional therapies. However, the acquisition of somatic mutations can result in TKI resistance. Clinical evidence suggests that acquired immunity contributes to the suppression of tumor recurrence, indicating the potential of induced antitumor immune reaction for the treatment of HCC. Recently, immune checkpoint inhibitors have become available for the treatment of malignancies. They are effective regardless of the response to prior therapies and a durable effect can be expected, which should be attributed to an adaptive immunity to HCC components. The results of phase I/II trials of nivolumab, an anti-programmed cell death-1 antibody, showed that 20% of patients showed objective response and that nivolumab was effective regardless of prior sorafenib treatment and viral status. Nivolumab received expedited Food and Drug Administration approval in 2017 for the treatment of advanced HCC after failure or intolerance to sorafenib. However, the majority of the patients remain refractory, likely due to the solid immune suppressive status, which involves many stromal cells, humoral mediators, and suppressive checkpoint molecules. Therefore, current clinical trials are focusing on how immunosuppressive conditions in HCC might be overcome using immune checkpoint inhibitors in combination with different types of immune checkpoint blockades, TKIs, and other conventional treatments. The development of immune checkpoint inhibitors is rapidly progressing and these inhibitors are likely to be key agents for HCC treatment in the near feature.