PDCD1 and liver cancer: Next, we examined anti-PD-1 antibody therapy combined with regorafenib (like cabozantinib, a potent TKI and second-line treatment for advanced liver cancer approved by the FDA in 2017; third-line treatment for advanced colon cancer approved by the FDA in 2012) plus chidamide-k30 regimens in CT26 tumor-bearing mice model.