DNA methylation of SLC22A1 and RASSF1A in histologically normal liver tissue. (a,b) DNA methylation profiles of SLC22A1 (a) and RASSF1A (b) in normal liver tissue (n = 100, IKP-liverbank), in histologically normal tissues derived from patients with hepatocellular carcinoma (HCC; n = 20, adjacent to tumor) and in HCC tumor tissue (n = 22). DNA methylation (y-axis) at each individual CpG site (x-axis) is given. Methylation profiles show median levels (diamonds) at each CpG position (shaded areas are defined by 25%/75% quantiles). P-values are given for differences in methylation level for CpG sites between HCC (n = 22) and histologically normal liver tissue (n = 100). *P < 0.05, **P < 0.01.