[Effect of HIF-2α on the biological characteristics of breast cancer stem cells].

Objective: To explore the effect of hypoxia inducible factor (HIF)-2α on biological characteristics of breast cancer stem cells (BCSCs). Methods: Stem cells were isolated and purified from MCF-7 cells by using the immunomagnetic microbeads. HIF-2α ORF/shRNA lentiviral vectors were transduced into MCF-7 stem cells respectively, and then the stable stem cell lines were detected and gained. Using the method of Cell Counting Kit-8 (CCK-8) and flow cytometry, the effect of HIF-2α on cell vitality and apoptosis of MCF-7 cancer stem cells (CSCs) were tested. Serum-free suspension culture was used on MCF-7 cells to get breast CSCs microspheres. The expression of CD44(+) in different groups were detected by flow cytometry. Tumor-bearing nude mice model was established to compare tumor growth rate and pulmonary metastasis probability of MCF-7 CSC HIF-2α knock up/down in vivo . Results: Compared with MCF-7 CSC group, the apoptosis rate of MCF-7 CSCs HIF-2α knockup group decreased obviously and cell proliferation activity increased significantly (all P <0.05). However, the MCF-7 CSCs HIF-2α knock down group had the opposite trend. Results of flow cytometry showed that the proportion of CD44(+) cells in HIF-2α knock up group(93.0%)was much higher than MCF-7 group(83.8%)and MCF-7 HIF-2α knock down group(51.6%). The tumor growth rate, quality and lung metastasis rate of MCF-7 CSC HIF-2α knock up group were significantly higher than those in MCF-7 CSCs group and MCF-7 CSCs HIF-2α knock down group ( P <0.01). Conclusions: In hypoxic microenvironment, up-regulation of HIF-2αpromoted the formation of MCF-7 CSCs. Over-expression of HIF-2α can promote proliferation and inhibit apoptosis of MCF-7 CSCs, and thus increase the risk of tumorigenic ablility and pulmonary metastasis.