Hypoxia Enhances Stemness of Cancer Stem Cells in Glioblastoma: An In Vitro Study

OBJECTIVE To investigate the relationship between hypoxia and in vitro "stemness" of cancer stem cells (CSCs). METHODS U87 cells, U251 cells and primary glioma cells (n=3) experienced hypoxia. Transmission electron microscopy was done to detect the ultrastructure of these cancer cells; MTT assay to detect the cell growth; flow cytometry to detect cell cycle and CD133 expression; Transwell chamber assay was carried out to detect the cell migration; colony-forming assay to detect the colony-forming efficiency; real-time quantitative PCR and Western blot were carried out to detect the mRNA and protein expression of markers of stem cells and their differentiation, respectively. RESULTS Hypoxia maintained the undifferentiated state of primary glioma cells, slowed down the growth of glioma cells which were in a relatively quiescent stage, increased the colony forming efficiency and migration of glioma cells, and elevated the expression of markers of stem cells, but the expression of markers for stem cell differentiation was reduced after hypoxia treatment. CONCLUSION Hypoxia may induce the "dedifferentiation" of differentiated glioma cells which then acquire the stemness.