Effect of blocking the PI3K/Akt signalling pathway on cell proliferation of the aggregated breast cancer stem cells in microspheres under hypoxia microenvironment

Objective: To investigate the effect of LY294002, a PI3K (phosphatidylinositol 3-kinase)-specific inhibitor that can block the PI3K/Akt signalling pathway, on cell proliferation of aggregated human BCSCs (breast cancer stem cells) in microspheres under hypoxic microenvironment. Methods: Stem cell microspheres were screened from human breast cancer MCF-7 cells by serum-free suspension culture. The expressions of cancer stem cell markers — CD44 and CD133 were detected by immunofluorescence staining method. The proliferative abilities of the aggregated BCSCs in microspheres exposed to different concentrations of LY294002 were detected by MTT method. The expression of HIF-2α (hypoxia-inducible factor-2α) mRNA in BCSCs in microspheres was detected by RT-PCR. The expressions of HIF-2α, PI3K and phospho-Akt proteins were detected by Western blotting. Results: The aggregated BCSCs in microspheres expressed high levels of CD44 and CD133. The cell proliferation of BCSCs in microspheres was effectively inhibited by LY294002 under hypoxic microenvironment, and this effect was most apparent at 72-96 h after treatment with LY294002 (P < 0.05). The expression levels of HIF-2α mRNA and PI3K, phospho-Akt and HIF-2α proteins in BCSCs in microspheres exposed to hypoxic conditions and LY294002 were significantly lower than those only exposed to hypoxic conditions (P < 0.05). Conclusion: PI3K-specific inhibitor LY294002 can suppress the proliferative ability of aggregated BCSCs in microspheres by blocking PI3K/Akt signalling pathway in vitro. DOI:10.3781/j.issn.1000-7431.2013.01.006