E2F4 and cancer: In the presence of chemotherapy with irinotecan, on the other hand, tumors engineered to express E2F4-specific shRNA constructs displayed a substantial increase in the percentage of cancer cells undergoing apoptosis, substantially higher than that observed in controls receiving the same treatment (mean percentage of apoptotic cancer cells within tissues infected with an empty lentivirus vector vs. E2F4-shRNA[#1] vs. E2F4-shRNA[#2]: 3.8% vs. 12.9% vs. 14.8%; Dunn’s test for pairwise comparisons: p<0.0001; 2-way ANOVA test for interaction between E2F4 knock-down and chemotherapy: p<0.0001).