We purified EpCAM+/CD44+/CD166+ (CSC-enriched) cancer cells from two PDX lines engineered to express E2F4-shRNAs (PDX-COLON-8, PDX-COLON-60) and then tested them for quantitative reductions in their capacity to initiate the formation of either copGFP+three-dimensional (3D) organoids in vitro or solid tumors in vivo, as compared to isogenic controls engineered to express an empty lentivirus vector (Supplementary Figure 4). This evidence concerns the gene CD44 and cancer.