In summary, we believe the apparent BRCA1-Notch discrepancy with our study reflects the (i) heterogeneous nature of the cancer stem cell phenotype; (ii) experimental differences such as use of different techniques and cell surface antigens to identify stem-like cells; and (iii) differences in the p53 status, which can have influence on stem cell function (as discussed earlier in the text). The gene discussed is TP53; the disease is cancer.