E2F1 and cancer: Functionally, E2F1, E2F2, and E2F3a represent growth-promoting transcription factors and overexpression of E2F1 and/or 3 has been documented in various human cancers, including diffuse large cell lymphoma (DLCL), head and neck carcinoma, invasive ductal breast carcinoma, non-small cell lung carcinoma and prostate cancer [1–8].