Glioma initiating cells (GICs), also known as glioma stem cells (GSCs), play an important role in the progression and recurrence of glioblastoma multiforme (GBM) due to their potential for self-renewal, multiple differentiation and tumor initiation. In the recent years, Notch1 has been found to be overexpressed in GICs. However, the regulatory mechanism of Notch1 in the self-renewal and invasion ability of GICs remains unclear. This study aims to explore the effect of Notch pathway on self-renewal and invasion of GICs and the underlying mechanisms. Bioinformatic analysis and immunohistochemistry (IHC) were performed to evaluate the expression of Notch1 and Hes1 in GBM samples. Immunofluorescent (IF) staining was performed to observe the distribution of Notch1 and CXCR4 in GBM and GICs. Both pharmacological intervention and RNA interference were employed to investigate the role of Notch1 in GICs self-renewal, invasion and tumor growth in vitro or in vivo. The crosstalk effect of Notch1 and CXCL12/CXCR4 system on GIC self-renewal and invasion was explored by sphere formation assay, limiting dilution assay and Transwell assay. Western blots were used to verify the activation of Notch1/CXCR4/AKT pathway in self-renewal, invasion and tumor growth of GICs. Luciferase reporter assay was used to testify the potential binding site of Notch1 signaling and CXCR4. The orthotopic GICs implantations were established to analyze the role and the mechanism of Notch1 in glioma progression in vivo. Notch1 signaling activity was elevated in GBM tissues. Notch1 and CXCR4 were both upregulated in GICs, compared to Notch1 positive glioma cells comprised a large proportion in the CD133+ glioma cell spheres, CXCR4 positive glioma cells which usually expressed Notch1 both and dispersed in the periphery of the sphere, only represent a small subset of CD133+ glioma cell spheres. Furthermore, downregulation of the Notch1 pathway by shRNA and MK0752 significantly inhibited the PI3K/AKT/mTOR signaling pathway via the decreased expression of CXCR4 in GICs, and weakened the self-renewal, invasion and tumor growth ability of GICs. These findings suggest that the cross-talk between Notch1 signaling and CXCL12/CXCR4 system could contribute to the self-renewal and invasion of GICs, and this discovery could help drive the design of more effective therapies in Notch1-targeted treatment of GBMs.

The T-helper 17 (Th17) cell and regulatory T cell (Treg) axis plays a crucial role in the development of multiple sclerosis (MS), which is regarded as an immune imbalance between pro-inflammatory cytokines and the maintenance of immune tolerance. Mesenchymal stem cell (MSC)-mediated therapies have received increasing attention in MS research. In MS and its animal model experimental autoimmune encephalomyelitis, MSC injection was shown to alter the differentiation of CD4⁺T cells. This alteration occurred by inducing anergy and reduction in the number of Th17 cells, stimulating the polarization of antigen-specific Treg to reverse the imbalance of the Th17/Treg axis, reducing the inflammatory cascade response and demyelination, and restoring an overall state of immune tolerance. In this review, we summarize the mechanisms by which MSCs regulate the balance between Th17 cells and Tregs, including extracellular vesicles, mitochondrial transfer, metabolic reprogramming, and autophagy. We aimed to identify new targets for MS treatment using cellular therapy by analyzing MSC-mediated Th17-to-Treg polarization. Graphical Abstract