To examine the role of BRCA1 in the regulation of breast cancer cell stemness, we created a genetically matched pair of human breast cancer cell lines using the HCC1937 cell line derived from a Grade 3 primary ductal carcinoma with a loss-of-function mutation in the BRCA1 gene (insertion C at nucleotide 5382). This evidence concerns the gene BRCA1 and breast ductal adenocarcinoma.