Down-regulation of hypoxia-inducible factor-1 suppresses malignant biological behavior of triple-negative breast cancer cells

This study is to investigate the effect and mechanism of reduced hypoxia-inducible factor (HIF)-1 alpha expression on malignant behavior of MDA-MB-231 cells. HIF-1 alpha expression was interfered by siRNA. Western blot was used to detect protein expression of HIF-1 alpha, active fragments of caspase 3 and vimentin. Cell count, flow cytometry and Hoechst staining were used to evaluate cell growth and apoptosis. Matrigel invasion and wound scratch assay were performed to measure the ability of cell invasion and migration. After MDA-MB-231 cells were transfected with HIF-1 alpha-targeted siRNA, HIF-1 alpha protein expression was successfully interrupted and cell growth was retarded. Compared with random siRNA group, reduced HIF-1 alpha protein expression in HIF-1 alpha-targeted siRNA group facilitated cell apoptosis but had no effect on cell cycle. In addition, cells treated with HIF-1 alpha-targeted siRNA expressed active fragments of caspase 3 (17 and 12 kD) after serum starvation for 0 to 60 h. Caspase 3 activity assay further confirmed the above finding. Reduced HIF-1 alpha expression impaired the migration and invasiveness with a reduction in the expression of vimentin and CK18 protein. Inhibition of HIF-1 alpha protein synthesis or enhancement of its degradation reversed its malignant phenotypes and could probably be a potential means for the treatment of triple-negative breast cancer.