Breast cancer is one of the most common types of carcinoma in humans. The aim of the present study was to identify the role of Notch 1 in the proliferation and invasion of human breast cancer cells. Firstly, the levels of Notch 1 were determined by western blot analysis in breast cancer cell lines, and the results revealed that the expression levels of Notch 1 were markedly higher in MDA-MB-231 and MCF-7 cells, and lower in MCF-10A cells, compared with human mammary epithelial cells. An MTT

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... y was used to determine the viability of breast cancer cells. The optical density (OD)490 values were significantly decreased in Notch 1 short hairpin (sh)RNA-transfected MCF-7 and MDA-MB-231 cells, compared with the OD490 values in the negative control shRNA-transfected cells. The MCF-7 cells and MDA-MB-231 cells were also treated with increasing concentrations of MRK003, a Notch 1 inhibitor, for 24, 48 and 72 h, respectively. The inhibition rate was gradually increased in the MRK003-treated cells in a time-and dose-dependent manner. The invasive ability of the cells was determined using a Transwell migration assay. The migration ability was significantly decreased in the Notch 1-transfected MCF-7 cells and MDA-MB-231 cells. The molecular mechanism was examined, and the knockdown of Notch 1 significantly decreased the expression levels of β-catenin, matrix metalloproteinase (MMP)-2 and MMP-9, and was also correlated with the downregulation of β-catenin in the nucleus. In conclusion, Notch 1 was key in the progression of breast cancer, and knocking down the expression of Notch 1 significantly suppressed the proliferation and invasion of breast cancer cells. This provides novel clues for cancer therapy in human breast cancer.