We determined relative Notch3 and E-cadherin expression levels via western blotting in five human breast cancer cell lines including MCF-7, T47D, SKBR3, MDA-MB-231(two strains stored in different laboratory) and BT549, of which MCF-7 and T47D are characterized as ER-/PgR-positive luminal mammary carcinoma, MDA-MB-231 and BT549 are characterized as triple-negative/basal-B mammary carcinoma (TNBC), and SKBR3 is a human breast cancer cell line that overexpresses the Her2 (Neu/ErbB-2) gene product. This evidence concerns the gene NOTCH3 and breast cancer.