DBF4 is a CDC7 kinase regulatory subunit, important in cell proliferation and DNA replication, overexpressed together with CDC7 in many primary tumors and cancer cell lines, such as diffuse large B-cell lymphoma, colorectal cancer, ovarian cancer, melanoma, breast cancer, and oral squamous cell carcinoma, and are markers of poor prognosis and of advanced tumor grade; many tumors contain extra copies of the DBF4 gene [119,133,134,135,136,137,138]. This evidence concerns the gene DBF4 and breast cancer.