In colon cancer cells, E2F1 and specific HR proteins had accumulated at higher levels (increased by 8.9/5.7-fold for E2F1, 8.7/7.6-fold for RAD51, 11.4/10.8-fold for RAD54, and 5.9/5.1-fold for RPA in HCT116/HT29 cells, respectively) than those in normal colon cells. Here, E2F1 is linked to malignant colon neoplasm.