Effects Of Hypoxia On Proliferation Of Human Breast Cancer Cells And The Empirical Study Of The Relationship Between Hypoxia And Notch Signaling

Objective:To observe the effects of hypoxia on the proliferation of breast cancer cells, and to investigate the mechanism and the crosslink between hypoxia and Notch signaling.Methods:Breast cancer cells MDA-MB-231 and MCF-7 were transfected with Notch1 interference RNA using Lipofectamine^TM 2000 to inhibit the expression of Notch1 and then put into the hypoxic environment for 4 hours. Cell proliferation was detected by MTT method, Cell cycle was analyzed by flow cytometry. The mRNA and protein expression of Notch1 and downstream target genes were detected by Real-Time RT-PCR and Western Blot method.Results:Hypoxia can promote the proliferation of breast cancer cells, the mRNA expression of Notch1 and its downstream Hey1 and Hes1 was noticeably increased (p<0.05), cells in the (G₀ /G₁) phases were significantly reduced (p<0.05), and the mRNA expression of CyclinD and CDK2 was significantly increased (p<0.05),but the mRNA expression of P21 was decreased (p<0.05). The growth of breast cancer cells was inhibited significantly after downregulation of Notch1 gene expression mediated by RNA interference, the cell cycle was arrested at G₁ phases, mRNA and protein expression of CyclinD and CDK2 were significantly decreased (p<0.05), while the mRNA and protein expression of P21 were increased (p<0.05).Conclusion:Hypoxia has the effects to promote the proliferation of breast cancer cells, and was concerned with Notch signaling. The siRNA technique which targets Notch1 gene can efficiently inhibit these effects. Thus silencing Notch1 gene by RNA interference may be a new approach of gene therapy for human breast cancer.