Insulin-like Growth Factor Binding Protein 7 Mediates Glioma Cell Growth and Migration

Insulin-like growth factor binding protein 7 (IGFBP-7) is the only member of the IGFBP superfamily that binds strongly to insulin, suggesting that IGFBP-7 may have different functions from other IGFBPs. Unlike other IGFBPs, the expression and functions of IGFBP-7 in glioma tumors have not been reported. Using cDNA microarray analysis, we found that expression of IGFBP-7 correlated with the grade of glioma tumors and the overall patient survival. This finding was further validated by real-time reverse transcription-polymerase chain reaction and Western blot analysis. We used RNAi to examine the role of IGFBP-7 in glioma cells, inhibiting IGFBP-7 expression by short interfering RNA transfection. Cell proliferation was suppressed after IGFBP-7 expression was inhibited for 5 days, and glioma cell growth was stimulated consistently by the addition of recombinant IGFBP-7 protein. Moreover, glioma cell migration was attenuated by IGFBP-7 depletion but enhanced by IGFBP-7 overexpression and addition. Overexpression of AKT1 in IGFBP-7-overxpressed cells attenuated the IGFBP-7-promoted migration and further enhanced inhibition of IGFBP-7 depletion on the migration. Phosphorylation of AKT and Erk1/2 was also inversely regulated by IGFBP-7 expression. These two factors together suggest that IGFBP-7 can regulate glioma cell migration through the AKT-ERK pathway, thereby playing an important role in glioma growth and migration

RTVP-1 regulates glioma cell migration and invasion via interaction with N-WASP and hnRNPK

Glioblastoma (GBM) are characterized by increased invasion into the surrounding normal brain tissue. RTVP-1 is highly expressed in GBM and regulates the migration and invasion of glioma cells. To further study RTVP-1 effects we performed a pull-down assay using His-tagged RTVP-1 followed by mass spectrometry and found that RTVP-1 was associated with the actin polymerization regulator, N-WASP. This association was further validated by co-immunoprecipitation and FRET analysis. We found that RTVP-1 increased cell spreading, migration and invasion and these effects were at least partly mediated by N-WASP. Another protein which was found by the pull-down assay to interact with RTVP-1 is hnRNPK. This protein has been recently reported to associate with and to inhibit the effect of N-WASP on cell spreading. hnRNPK decreased cell migration, spreading and invasion in glioma cells. Using co-immunoprecipitation we validated the interactions of hnRNPK with N-WASP and RTVP-1 in glioma cells. In addition, we found that overexpression of RTVP-1 decreased the association of N-WASP and hnRNPK. In summary, we report that RTVP-1 regulates glioma cell spreading, migration and invasion and that these effects are mediated via interaction with N-WASP and by interfering with the inhibitory effect of hnRNPK on the function of this protein

miR-504 modulates the stemness and mesenchymal transition of glioma stem cells and their interaction with microglia via delivery by extracellular vesicles

Glioblastoma (GBM) is a highly aggressive tumor with poor prognosis. A small subpopulation of glioma stem cells (GSCs) has been implicated in radiation resistance and tumor recurrence. In this study we analyzed the expression of miRNAs associated with the functions of GSCs using miRNA microarray analysis of these cells compared with human neural stem cells. These analyses identified gene clusters associated with glioma cell invasiveness, axonal guidance, and TGF-β signaling. miR-504 was significantly downregulated in GSCs compared with NSCs, its expression was lower in GBM compared with normal brain specimens and further decreased in the mesenchymal glioma subtype. Overexpression of miR-504 in GSCs inhibited their self-renewal, migration and the expression of mesenchymal markers. The inhibitory effect of miR-504 was mediated by targeting Grb10 expression which acts as an oncogene in GSCs and GBM. Overexpression of exogenous miR-504 resulted also in its delivery to cocultured microglia by GSC-secreted extracellular vesicles (EVs) and in the abrogation of the GSC-induced polarization of microglia to M2 subtype. Finally, miR-504 overexpression prolonged the survival of mice harboring GSC-derived xenografts and decreased tumor growth. In summary, we identified miRNAs and potential target networks that play a role in the stemness and mesenchymal transition of GSCs and the miR-504/Grb10 pathway as an important regulator of this process. Overexpression of miR-504 exerted antitumor effects in GSCs as well as bystander effects on the polarization of microglia via delivery by EVs

RTVP-1 promotes mesenchymal transformation of glioma via a STAT-3/IL-6-dependent positive feedback loop

Glioblastomas (GBMs), the most aggressive primary brain tumors, exhibit increased invasiveness and resistance to anti-tumor treatments. We explored the role of RTVP-1, a glioma-associated protein that promotes glioma cell migration, in the mesenchymal transformation of GBM. Analysis of The Cancer Genome Atlas (TCGA) demonstrated that RTVP-1 expression was higher in mesenchymal GBM and predicted tumor recurrence and poor clinical outcome. ChiP analysis revealed that the RTVP-1 promoter binds STAT3 and C/EBPβ, two master transcription factors that regulate mesenchymal transformation of GBM. In addition, IL-6 induced RTVP-1 expression in a STAT3-dependent manner. RTVP-1 increased the migration and mesenchymal transformation of glioma cells. Similarly, overexpression of RTVP-1 in human neural stem cells induced mesenchymal differentiation, whereas silencing of RTVP-1 in glioma stem cells (GSCs) decreased the mesenchymal transformation and stemness of these cells. Silencing of RTVP-1 also increased the survival of mice bearing GSC-derived xenografts. Using gene array analysis of RTVP-1 silenced glioma cells we identified IL-6 as a mediator of RTVP-1 effects on the mesenchymal transformation and migration of GSCs, therefore acting in a positive feedback loop by upregulating RTVP-1 expression via the STAT3 pathway. Collectively, these results implicate RTVP-1 as a novel prognostic marker and therapeutic target in GBM

Propofol Inhibits Glioma Stem Cell Growth and Migration and Their Interaction with Microglia via BDNF-AS and Extracellular Vesicles

Glioblastoma (GBM) is the most common and aggressive primary brain tumor. GBM contains a small subpopulation of glioma stem cells (GSCs) that are implicated in treatment resistance, tumor infiltration, and recurrence, and are thereby considered important therapeutic targets. Recent clinical studies have suggested that the choice of general anesthetic (GA), particularly propofol, during tumor resection, affects subsequent tumor response to treatments and patient prognosis. In this study, we investigated the molecular mechanisms underlying propofol\u27s anti-tumor effects on GSCs and their interaction with microglia cells. Propofol exerted a dose-dependent inhibitory effect on the self-renewal, expression of mesenchymal markers, and migration of GSCs and sensitized them to both temozolomide (TMZ) and radiation. At higher concentrations, propofol induced a large degree of cell death, as demonstrated using microfluid chip technology. Propofol increased the expression of the lncRNA BDNF-AS, which acts as a tumor suppressor in GBM, and silencing of this lncRNA partially abrogated propofol\u27s effects. Propofol also inhibited the pro-tumorigenic GSC-microglia crosstalk via extracellular vesicles (EVs) and delivery of BDNF-AS. In conclusion, propofol exerted anti-tumor effects on GSCs, sensitized these cells to radiation and TMZ, and inhibited their pro-tumorigenic interactions with microglia via transfer of BDNF-AS by EVs

Overexpression of miR-504 in glioma stem cells inhibits the oncogenic potential and the crosstalk of these cells with microglia via exosomal delivery

Background: Glioblastoma (GBM) is a highly aggressive tumour that exhibits resistance to therapy and poor prognosis. A small subpopulation of glioma stem cells (GSCs) has been implicated in radio-resistance and tumour recurrence. Mesenchymal transformation of GBM and GSCs is associated with aggressive phenotypes, radiation resistance and positive regulatory interaction with microglia. Methods: Here, we analysed miRNAs associated with the stemness and mesenchymal transformation of GSCs using miRNA microarray analysis of these cells compared with human neural stem cells (NSCs) and mesenchymal stromal cells (MSCs). Self-renewal, stemness microglia activation and exosomal delivery were studied. Data were analysed using ANOVA or a Student\u27s t-test with correction for data sets with unequal variances. Results: We identified gene clusters associated with glioma cell invasiveness, axonal guidance and TGF-beta signaling. miR-504 was significantly downregulated in GSCs; its expression was decreased in GBM compared with normal brain specimens and was further lower in the mesenchymal subtype. The effects of miR-504 on the stemness, mesenchymal transformation of GSCs and their interaction with microglial cells were studied. Overexpression of miR-504 inhibited the self-renewal, migration and the expression of mesenchymal markers in GSCs. The inhibitory effect of miR-504 was partly mediated by upregulating the tumour suppressor miR-145. In addition, miR-504 targeted Grb10 and EGFR2, which act as oncogenes in GSCs and GBM. Using novel reporters and imaging methods we demonstrated that overexpression of miR-504 in GSCs resulted in its delivery by GSC-secreted exosomes to microglia and in the abrogation of the GSC-induced polarization of microglia to M2 phenotype. Finally, miR-504 overexpression inhibited xenograft growth and prolonged the survival of mice harbouring GSC-derived xenografts. miR-504 was detected in high levels in circulating serum exosomes of xenografted mice. Summary/Conclusion: We identified the miR-504/miR145/CTGF and miR-504/Grb10/Egr1 pathways as important regulators of the mesenchymal transformation of GBM. Overexpression of miR-504 exerts antitumour effects in GSCs as well as bystander effects on the polarization of microglia, and possibly also on peripheral immune responses, via exosomal delivery