E2F1 and breast cancer: In the mouse model of metastatic breast cancer, interbreeding the mouse mammary tumor virus (MMTV)-polyomavirus middle T oncoprotein (PyMT) mice with E2F1, E2F2, or E2F3 knockout mice revealed that E2F1 and E2F2 control the expression of genes critical to angiogenesis, remodeling of the extracellular matrix, tumor cell survival, and tumor cell interactions with vascular endothelial cells that facilitate metastasis to the lungs [110].