To identify the functional consequences of co-upregulation of E2F1, E2F2, and E2F3 in breast tumors—specifically to identify drivers of CA and mitotic dysfunction in mammary epithelial cells—we engineered MCF10A mammary epithelial cells to overexpress E2F1 and E2F3a, E2F2 and E2F3a, or the three E2F activators (Figure 1A and 1B). This evidence concerns the gene E2F1 and breast neoplasm.