Evaluation of miRNA Expression in Glioblastoma Stem-like Cells: a Comparison Between Normoxia and Hypoxia Microenvironment

Purpose: Glioblastoma is one of the most aggressive and incurable brain tumors whose progression is driven in part by a small sub population of cells termed as glioblastoma stem cells responsible for the tumor’s low therapy efficacy. Hypoxia, a common phenomenon in glioblastoma also promotes the maintenance and the expansion of the stem cell population whose survival is aided by miRNAs. Methods: GBM stem-like cells cultures were isolated and the relationship between the microenvironments and the in vitro “stemness” of the cells was investigated by evaluating the expression of miRNAs and selected genes. Results: We found miR-128a-3p, 34-5p and 181a-3p to be down-regulated while miR-17-5p and miR-221-3p to be up-regulated in the stem-like cells. When a comparison was made between the stem-like cells cultured under normoxia and hypoxia, a fold down-regulation difference of 3.5 to 5, 2 to 5 and 2 to 4 for miR-34-5p, 128a-3p and 181a-3p was observed respectively and a fold upreulation of 3.5 to 4 and 2.5 to 4 was observed for miR-221-3p and 17-5p respectively. There was an increased expression of HIF-1/2, SOX2, OCT4, VEGF, GLUT-1, BCL2 and survivin under hypoxia. Conclusion: Hypoxia enhanced the expression of several tumor stem cell signature genes, involved in the regulation of stemness, metabolism, angiogenesis and anti-apoptotic property. Most importantly, the miRNA dysregulation in the stem-like cell population adds another layer of gene expression associated with gliomagenesis and maintenance of CSC pointing to new signaling mechanisms whose disruption can be used to successfully target this crucial subpopulation.