We therefore examined SLC22A1, SLC22A2 and SLC22A3 DNA methylation in histologically normal liver tissue from patients without primary liver tumors (n = 100, IKP-liverbank; Tables S1 and S4 in Additional file 1) compared with histologically normal tissues derived from patients with HCC (n = 20; Tables S1 and S4 in Additional file 1). Here, SLC22A1 is linked to hepatocellular carcinoma.