Glioma stem cells (GSCs) are a special subpopulation of glioma cells that are key to the sensitivity of tumors to treatments and to the possibility of tumor recurrence. Identifying new strategies that inhibit the growth of GSCs are therefore important for developing novel therapies for glioblastoma multiforme (GBM). In this study, CD133+ human glioma stem cells were isolated and cultured. Magnetic nanoparticles were used to mediate the expression of siRNAs targeting the HOTAIR (si-HOTAIR) sequence in human gliomas. Effect of downregulation of HOTAIR expression on proliferation, invasion and in vivo tumorigenicity of human GSCs and underlying molecular mechanisms were further evaluated. The results of the MTT assay and flow cytometric analysis showed that downregulation of HOTAIR expression inhibited cell proliferation and induced cell cycle arrest. Transwell assays demonstrated that downregulation of HOTAIR expression resulted in a decrease in the invasive capability of GSCs. Moreover, magnetic nanoparticle-mediated low expression of HOTAIR effectively reduced the tumorigenic capacity of glioma stem cells in vivo. In addition, the results of qRT-PCR and western blot analysis demonstrated that downregulation of HOTAIR expression significantly increased the expression of PDCD4 in GSCs, in addition to reducing the expression of CCND1 and CDK4. An in-depth mechanistic analysis showed that downregulation of HOTAIR expression reduced the recruitment of downstream molecules, EZH2 and LSD1, thereby activating the expression of PDCD4 at the transcriptional level. In conclusion, downregulation of HOTAIR expression effectively promoted the expression of PDCD4, thereby inhibiting the proliferation, invasion and in vivo tumorigenicity of human GSCs.
Human glioma stem cells express high levels of HOTAIR
(A) CD133+ human glioma stem cells were isolated from glioma tissues using a flow cytometry-based cell sorting technique. (B) In a serum-free culture system, CD133+ human glioma stem cells grew clonally in suspension (original magnification, x200). (C) The results of the CCK-8 assay indicated that CD133+ human glioma stem cells possessed a significantly greater proliferative capability compared with CD133- human glioma cells. (D) The results of qRT-PCR revealed that the expression of the neural stem cell-related markers CD44, CD133, nestin and Bdnf was significantly elevated in CD133+ human glioma stem cells compared with CD133- human glioma cells. (E) The results of northern blot analysis demonstrated that the intensity of the HOTAIR hybridization signal was significantly stronger in CD133+ human glioma stem cells in comparison with CD133- human glioma cells.