To define the molecular changes associated with BRCA1-deficient breast cancer, we previously compared BRCA1-deficient (KB1P) mammary tumors derived from our conditional K14cre;Brca1F/F;p53F/F mouse model for hereditary breast cancer with BRCA1-proficient mammary tumors (KP) derived from K14cre;Brca1w. The gene discussed is BRCA1; the disease is breast cancer.