E2F4 and cancer: 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).