BIS-mediated STAT3 stabilization regulates glioblastoma stem cell-like phenotypes

Abstract

Glioblastoma stem cells (GSCs) are a subpopulation of highly tumorigenic and stem-like cells that are responsible for resistance to conventional therapy. Bcl-2-intreacting cell death suppressor (BIS; also known as BAG3) is an anti-apoptotic protein that is highly expressed in human cancers with various origins, including glioblastoma. In the present study, to investigate the role of BIS in GSC subpopulation, we examined the expression profile of BIS in A172 and U87-MG glioblastoma cell lines under specific in vitro culture conditions that enrich GSC-like cells in spheres. Both BIS mRNA and protein levels significantly increased under the sphere-forming condition as compared with standard culture conditions. BIS depletion resulted in notable decreases in sphere-forming activity and was accompanied with decreases in SOX-2 expression. The expression of STAT3, a master regulator of stemness, also decreased following BIS depletion concomitant with decreases in the nuclear levels of active phosphorylated STAT3, while ectopic STAT3 overexpression resulted in recovery of sphere-forming activity in BIS-knockdown glioblastoma cells. Additionally, immunoprecipitation and confocal microscopy revealed that BIS physically interacts with STAT3. Furthermore, BIS depletion increased STAT3 ubiquitination, suggesting that BIS is necessary for STAT3 stabilization in GSC-like cells. BIS depletion also affected epithelial-to-mesenchymal transition-related genes as evidenced by decrease in SNAIL and MMP-2 expression and increase in E-cadherin expression in GSC-like cells. Our findings suggest that high levels of BIS expression might confer stem-cell-like properties on cancer cells through STAT3 stabilization, indicating that BIS is a potential target in cancer therapy.

Heat Shock Factor 1 Depletion Sensitizes A172 Glioblastoma Cells to Temozolomide via Suppression of Cancer Stem Cell-Like Properties

“…However, little is known regarding the role of BIS and HSF1 in GSC-like SPs. A previous study demonstrating that BIS was involved in regulation of the GSC-like phenotype via signal transducer and activator of transcription 3 (STAT3) stabilization prompted us to investigate whether BIS depletion might affect HSF1 in SP-forming conditions [16]. In the present study, we demonstrated that BIS depletion downregulated HSF1 protein levels and altered its subcellular localization.…”

“…Previous studies, as well as increasing evidence, support this postulation as BIS has been shown to regulate several proteins, including microtubule-associated protein 1 light chain 3β (MAP1LC3B) [32], STAT3 [16], and myosin heavy chain [33]. …”

“…BIS depletion also inhibited GSC-like properties and SOX2 expression in glioblastoma cell lines under the same conditions [16]. However, little is known about the relationship between HSF1 and BIS in GSC-like SPs and the combined effect of BIS or HSF1 depletion and TMZ treatment on apoptosis.…”

Combination Treatment with PPARγLigand and Its Specific Inhibitor GW9662 Downregulates BIS and 14-3-3 Gamma, Inhibiting Stem-Like Properties in Glioblastoma Cells

“…Our recent report demonstrated that BIS is linked to glioblastoma stemness by stabilization of the signal transducer and activator of transcription 3 (STAT3) [33]. These findings provide reliable evidence that BIS is a potential target for therapy.…”

Synergistic effect of TRAIL and irradiation in elimination of glioblastoma stem-like cells

“…GSLC was the most vicious cell type in GBM cells, involving in treatment resistance and recurrence of GBMs [2,5]. In order to study the properties of GSLCs, we firstly enriched them from two GBM cell lines using serum-free medium supplemented with growth factors as the literature reported [29][30][31]. CD133 is still the most commonly used cell markers of glioma stem cells [6,32] despite some disputes [33].…”