It has been reported that SP cells, which are typically identified based on their ability to efflux DNA-binding dye Hoechst 33342 through overexpressed ATP-binding cassette (ABC) transporters, such as ABCG2, have CSC-like characteristics and can be applied as a marker of CSCs for HCC (Chiba et al., 2006). This evidence concerns the gene ABCG2 and hepatocellular carcinoma.