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Background/Aims: Jagged1 is the ligands of the Notch signaling and has been shown to promote glioma-initiating cells (GICs) in glioblastoma. The role of Jagged1 in GICs invasion and underlying molecular mechanisms remain unclear. Methods: Survival data from R2 genomics analysis, the Cancer Genome Atlas (TCGA), the Chinese Glioma Genome Atlas (CGGA) and visualization platform database were used to evaluate the effects of Jagged1 on overall patient survival. we investigated Jagged1 induced the GICs cells’ invasion by matrix degradation assays and Transwell cell invasion assays in vitro, then we further explored the underlying molecular mechanisms using Co-immunoprecipitation (co-IP) analysis. Results: High expression of Jagged1 in human glioma was associated with poor survival. Clinical data analysis showed that the Jagged1 was positively correlated with NF-κB(p65). Jagged1-induced invasion of GICs cells through activation of NF-κB(p65) pathway. In vivo, knockdown of Jagged1 could suppress the tumorigenicity of GICs cells through NF-κB(p65) signaling. Conclusion: Insights gained from these findings suggest that Jagged1 plays an important oncogenic role in GICs malignancy by activation of NF-κB(p65) signaling, and Jagged1 could be employed as an effective therapeutic target for GICs.

Glioblastoma (GBM) invasion and migration are key biological behaviors leading to refractoriness to current therapies and infiltration into the non-tumor brain parenchyma. GBM cell migration is strongly dependent on tumor architecture in vivo, which is absent in traditional two-dimensional (2D) monolayer culture. The present study applied a three-dimensional (3D) hydrogel model to rebuild the tumor architecture in vitro. Treatment with NSC23766, a specific inhibitor of Ras-related C3 botulinum toxin substrate 1 (Rac1), inhibited the mesenchymal invasiveness however triggered the amoeboid motility called mesenchymal-amoeboid transition (MAT). Notably, NSC23766 stimulated U87 GBM cell migration in the 3D hydrogel. However, this compound inhibited cell motility in 2D monolayer culture without tumor architecture for MAT, suggesting the advantage of 3D hydrogel to investigate tumor cell invasion. Due to the inverse interaction of Rac1 and Ras homolog family member A (RhoA) signaling in the transition between mesenchymal and amoeboid morphology, simultaneous treatment of NSC23766 and Y27632 (selective Rho associated coiled-coil containing protein kinase 1 inhibitor), abolished U87 GBM cell migration through inhibiting MAT and amoeboid-mesenchymal transition. In addition, Y27632 induced integrin expression which gave rise to the focal adhesion to facilitate the mesenchymal invasion. The results of the present study demonstrated that the 3D hydrogel was a preferable model in vitro to study tumor cell invasion and migration. The combined inhibition of Rac1 and RhoA signaling would be a promising strategy to suppress GBM invasion.

Glioblastoma (GBM) is the most common and lethal primary intracranial tumor. Actin cytoskeleton regulator Arp2/3 complex stimulates glioma cell motility and migration, and thus triggers tumor invasion. However, little is known regarding the role of actin cytoskeleton in maintaining the stem cell phenotype. Here, we showed that Arp2/3 complex improved stem cell phenotype maintenance through sustaining the activated Notch signaling. ShRNA targeting Notch ligand Delta-like 1 (DLL1) decreased CD133 and Nestin expression, and impaired the self-renewal ability of CD133+ U87-MG and U251-MG glioma cells, indicating DLL1/Notch1 signaling promoted stem cell phenotype maintenance. Interestingly, inhibiting Arp2/3 complex also induced the similar effect of shDLL1. Silencing DLL1 in the Arp2/3 inhibited CD133+ cells did not further abrogate the stem cell phenotype, suggesting DLL1 function requires Arp2/3 complex in glioma initiating cells (GICs). However, exogenous soluble DLL1 (sDLL1) instead of endogenous DLL1 rescued the Arp2/3 inhibition-induced stem cell phenotype suppression. The underlying mechanism was that Arp2/3 inhibition impeded DLL1 vesicular transport from cytoplasm to cell membrane, which resulted in DLL1 unable to activate Notch pathway. Furthermore, we illustrated that Arp2/3 inhibition abolished the tumorigenicity of CD133+ U87-MG neurosphere cells in the intracranial model. These findings suggested that cytoskeleton maintained the stem cell phenotype in GBM, which provide novel therapeutic strategy that anti-invasive targeted therapies may help eliminate GICs.

Numerous studies have shown that calmodulin (CaM) is a major regulator of calcium-dependent signaling, which regulates cell proliferation, programmed cell death, and autophagy in cancer. However, limited information is available on mechanisms underlying the effect of CaM on the invasive property of glioblastoma multiforme (GBM) cells, especially with respect to invadopodia formation. In this study, we find that CaM serves as a prognostic factor for GBM, and it is strongly associated with the invasive nature of this tumor. Results of preliminary experiments indicated that CaM concentration was significantly correlated with the invasive capacity of and invadopodia formation by different GBM cell lines. CaM inhibition via a small hairpin RNA or a pharmacological inhibitor significantly disrupted invadopodia formation and MMP activity and downregulated vimentin expression. Moreover, CaM knockdown exerted a strong anti-invasive effect on GBM in vivo. Interestingly, epidermal growth factor treatment promoted CaM redistribution from the nucleus to the cytoplasm, eventually activating invadopodia-associated proteins by binding to them via their cytosolic-binding sites. Moreover, CaM inhibition suppressed the activation of invadopodia-associated proteins. Thus, our findings provide a novel therapeutic strategy to impede GBM invasion by inhibiting invadopodia formation, and shed light on the spatial organization of CaM signals during GBM invasion.

Glioblastomas (GBMs) are the most prevalent and devastating primary intracranial malignancies and have extensive heterogeneity. Notch1 signaling is a more complex process in the development of numerous cell and tissue types, including gliomagenesis and progression, and is upregulated in glioma-initiating cells. However, the contradictory expression of Notch1 among lower grade gliomas and GBMs confounds our understanding of GBM biology and has made identifying effective therapies difficult. In this study, we validated that Notch1 and NF-κB(p65) are highly expressed in the classical and proneural subtypes of GBM using the data set from The Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA). DAPT and shRNA targeting Notch1 decreased NF-κB(p65) expression, suppressed cell proliferation, and induced apoptosis of GBM cells in vitro and in vivo. Furthermore, we illustrated that the intracellular Notch could bind with NF-κB(p65) in GBM cells. These findings suggest that the cross-talk between Notch1 signaling and NF-κB(p65) could contribute to the proliferation and apoptosis of glioma, and this discovery could help drive the design of more effective therapies in Notch1-targeted clinical trials.