According to the expression patterns of COL4A1 in HCC cell lines, we knocked down COL4A1 in SMMC7721, SK-Hep1, HepG2 and PLC/PRF/5 cells by two independent shRNAs (Fig. 2a and Additional file 5: Figure S2A). This evidence concerns the gene COL4A1 and hepatocellular carcinoma.