KRAS and hepatocellular carcinoma: To setup NS3/4A stably expressing cells to visualize NS3/4A protease activity in vitro and in vivo, we constructed the NS3/4A gene (HCV JFH-1 2a strain) into a lentiviral vector, pLKO_AS3 NS3/4A, and the infected cells were selected via puromycin to directly express HCV NS3/4A protease in the human hepatocellular carcinoma HCC36 cells (NS3/4A-HCC36).