Expression analysis in normal and tumor tissues. (a) SLC22A1, SLC22A2, and SLC22A3 mRNA expression in different human normal and tumor tissues of the respective organs (TissueScan, Origene Technologies, Rockville, MD, USA) was quantified using TaqMan technology. (b) SLC22A1/OCT1, SLC22A2/OCT2 and SLC22A3/OCT3 protein expression (green) was analyzed by confocal laser scanning microscopy in HCC tumor tissue (n = 7) compared with histologically normal liver tissue (n = 5, IKP-liverbank) derived from patients without hepatocellular carcinoma (HCC). Specific antibodies were used to detect SLC22A1, SLC22A2 and SLC22A3 proteins. Representative images are shown.