Antibodies to CD133 were tested in U87 MG and HT29 cells, which are known to express low and high levels, respectively, of endogenous CD133 [24]; HT29 cells also express high levels of other known CSC markers, such as Nanog, ALDH1, and pY397-FAK, compared to other tumor cell lines (S2 Fig). This evidence concerns the gene ALDH1A1 and neoplasm.