Statistical analysis revealed significantly lower SLC22A1 immunoreactivity in HCC tissues compared with adjacent tissues (P < 0.0001; Figure 2a), irrespective of the presumed etiology of the HCC (for example, hepatitis B virus or hepatitis C virus; a paired comparison is shown in Figure S1 in Additional file 1). This evidence concerns the gene SLC22A1 and hepatocellular carcinoma.