Additional experiments in IC50 measurement and tumor sphere formation indicate that knocking down both GLI1 and GLI2 has similar effect as GLI1 knockdown (Supplementary Figure 2 for IC50 value, and Supplementary Figure 3 for tumor sphere formation), suggesting that the feed-forward loop exerted by GLI1 is the major factor for regulation of putative cancer stem cells. The gene discussed is GLI2; the disease is cancer.