ABCG2 and cancer: Although we did not observe a distinct phenotype, we could show that CHM1 enhanced the expression of ABCG2 and PROM1. ABCG2 is expressed in a wide variety of stem cells (Zhou et al., 2001), while PROM1 is so in embryonic and adult as well as cancer stem cells and maintains stem cell properties by suppressing differentiation (Katoh and Katoh, 2007).