To investigate the potential role of Notch3 signaling in breast cancer cells, we, respectively, established stable N3ICD- as well as TD+N3ICD-overexpressing transfectants in low Notch3-expressing MDA-MB-231 cells by transfecting pCLE/N3ICD or pCMV-(TD+N3ICD) plasmids. This evidence concerns the gene NOTCH3 and breast cancer.