Evaluation of miRNA Expression in Glioblastoma Stem-Like Cells: A Comparison between Normoxia and Hypoxia Microenvironment

Abstract

Purpose: Glioblastoma is an aggressive and incurable brain tumor whose progression is driven in part by glioblastoma stem cells, which are also responsible for the tumor’s low therapy efficacy. The maintenance and expansion of the stem cell population is promoted by the hypoxic microenvironment, where miRNAs play fundamental roles in their survival. Methods: GBM stem-like cells were isolated from three GBM parental cell lines. The stem-like cells were then cultured under normoxic and hypoxic microenvironments followed by investigation of the in vitro “stemness” of the cells. Results: We found miR-128a-3p, 34-5p and 181a-3p to be downregulated and miR-17-5p and miR-221-3p to be upregulated in our stem-like cells compared to the GBMs. When a comparison was made between normoxia and hypoxia, a further fold downregulation was observed for miR-34-5p, miR-128a-3p and miR-181a-3p and a further upregulation was observed for miR-221-3p and 17-5p. There was an increased expression of HIF-1/2, SOX2, OCT4, VEGF, GLUT-1, BCL2 and survivin under hypoxia. Conclusion: Our data suggest that our GBMs were able to grow as stem-like cells and as spheroids. There was a differential expression of miRNAs between the stems and the GBMs and the hypoxia microenvironment influenced further dysregulation of the miRNAs and some selected genes.