To determine the function of FAM99A in HCC cell lines, qRT-PCR was performed to examine the expression level of FAM99A in six HCC cell lines, and the results are shown in Fig. 4A. Hep 3B and Huh-7 cells with relatively high expression of FAM99A were selected for gain-of-function and loss-of-function analyses. The gene discussed is FAM99A; the disease is hepatocellular carcinoma.