To determine the role of RNF8 in breast cancer, we first examined its expression in breast cell lines with various differentiated character by western blotting, including the immortalized breast cell lines MCF-10A and MCF-10 F, the epithelial breast cancer cell lines MCF7 and T47D, and the metastatic, mesenchymal breast cancer cell lines MDA-MB-231 and BT549, as well as MDA-MB-435, a breast metastasis-derived cell line of melanoma origin. This evidence concerns the gene RNF8 and breast cancer.