Abstract
Glioblastoma is the most common and malignant brain tumor in humans. It is a heterogeneous tumor harboring glioblastoma stem cells (GSC) and other glioblastoma cells that survive and sustain tumor growth in a hypoxic environment via induction of autophagy and resistance to apoptosis. So, a therapeutic strategy to inhibit autophagy and promote apoptosis could greatly help control growth of glioblastoma. We created hypoxia using sodium sulfite (SS) for induction of substantiated autophagy in human GSC and glioblastoma SNB19 cells. Induction of autophagy was confirmed by acridine orange (AO) staining and significant increase in Beclin-1 in autophagic cells. microRNA database (miRDB) search suggested that miR-30e could suppress the autophagy marker Beclin-1 and also inhibit the caspase activation inhibitors (AVEN and BIRC6). Pro-apoptotic effect of proanthocyanidin (PAC) has not yet been explored in glioblastoma cells. Combination of 50 nM miR-30e and 150 μM PAC acted synergistically for inhibition of viability in both cells. This combination therapy most effectively altered expression of molecules for inhibition of autophagy and induced extrinsic and intrinsic pathways of apoptosis through suppression of AVEN and BIRC6. Collectively, combination of miR-30e and PAC is a promising therapeutic strategy to inhibit autophagy and increase apoptosis in GSC and SNB19 cells.
Highlights
Glioblastoma is a perpetually fatal central nervous system tumor, which generally occurs in the cerebral hemispheres and brain stem
We first investigated whether the hypoxia mimetic compound sodium sulfite (SS) could induce autophagy in human glioblastoma stem cells (GSC) and SNB19 cells (Fig 1)
Exposure of the cells to different doses (0.1–2 mM) of SS for 24 h followed by staining with acridine orange (AO) showed that 2 mM SS was very effective in inducing autophagy in both GSC and SNB19 cells (Fig 1A)
Summary
Glioblastoma is a perpetually fatal central nervous system tumor, which generally occurs in the cerebral hemispheres and brain stem. Autophagy, which is an acclaimed cell survival strategy in solid tumors like glioblastoma, plays a crucial role in homeostatic removal with degradation and recycling of damaged and mis-folded proteins and organelles [2,3,4]. Recent investigations suggest that autophagy can be an important catabolic mechanism in solid tumors that can help in utilizing nutrients and providing building blocks for growth of tumor cells during starvation and hypoxia and autophagy contributes to overall survival of the tumor cells [5,6]. As a result of uncontrolled growth of tumor cells, oxygen depletion or hypoxic microenvironment could contribute to survival strategy by inducing autophagy [7]. Many earlier investigations have described that autophagy can play a dual role in cell survival as well as in cell death; crosstalk and interplay between autophagy and apoptosis appear to be complex and controversial [4,8]
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