To test whether this pluripotency reporter is active in breast cancer cell lines, cell lines MCF-7S4+ (representing the most common luminal breast cancer type), MDA-MB-231S4+ (as example of mesenchymal-like breast carcinoma), and MDA-MB-436S4+ (representing BRCA1 deficient breast cancer) were generated from parental cell lines through lentiviral gene transfer of the pL-SIN-EOS-S(4+) EGFP transcriptional reporter. The gene discussed is BRCA1; the disease is breast cancer.