RNAi for contactin 2 inhibits proliferation of U87-glioma stem cells by downregulating AICD, EGFR, and HES1

Contactin 2 homophilic adhesion structure and conformational plasticity

The cell-surface attached glycoprotein contactin 2 is ubiquitously expressed in the nervous system and mediates homotypic cell-cell interactions to organize cell guidance, differentiation, and adhesion. Contactin 2 consists of six Ig and four fibronectin type III domains (FnIII) of which the first four Ig domains form a horseshoe structure important for homodimerization and oligomerization. Here we report the crystal structure of the six-domain contactin 2Ig1-6 and show that the Ig5-Ig6 combination is oriented away from the horseshoe with flexion in interdomain connections. Two distinct dimer states, through Ig1-Ig2 and Ig3-Ig6 interactions, together allow formation of larger oligomers. Combined size exclusion chromatography with multiangle light scattering (SEC-MALS), small-angle X-ray scattering (SAXS) and native MS analysis indicates contactin 2Ig1-6 oligomerizes in a glycan dependent manner. SAXS and negative-stain electron microscopy reveals inherent plasticity of the contactin 2 full-ectodomain. The combination of intermolecular binding sites and ectodomain plasticity explains how contactin 2 can function as a homotypic adhesion molecule in diverse intercellular environments.

Molecular Docking and Molecular Dynamics Studies Reveal Secretory Proteins as Novel Targets of Temozolomide in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is a tumor of glial origin and is the most malignant, aggressive and prevalent type, with the highest mortality rate in adult brain cancer. Surgical resection of the tumor followed by Temozolomide (TMZ) therapy is currently available, but the development of resistance to TMZ is a common limiting factor in effective treatment. The present study investigated the potential interactions of TMZ with several secretory proteins involved in various molecular and cellular processes in GBM. Automated docking studies were performed using AutoDock 4.2, which showed an encouraging binding affinity of TMZ towards all targeted proteins, with the strongest interaction and binding affinity with GDF1 and SLIT1, followed by NPTX1, CREG2 and SERPINI, among the selected proteins. Molecular dynamics (MD) simulations of protein-ligand complexes were performed via CABS-flex V2.0 and the iMOD server to evaluate the root-mean-square fluctuations (RMSFs) and measure protein stability, respectively. The results showed that docked models were more flexible and stable with TMZ, suggesting that it may be able to target putative proteins implicated in gliomagenesis that may impact radioresistance. However, additional in vitro and in vivo investigations can ascertain the potential of the selected proteins to serve as novel targets for TMZ for GBM treatment.

PTPRD and CNTNAP2 as markers of tumor aggressiveness in oligodendrogliomas

Oligodendrogliomas are typically associated with the most favorable prognosis among diffuse gliomas. However, many of the tumors progress, eventually leading to patient death. To characterize the changes associated with oligodendroglioma recurrence and progression, we analyzed two recurrent oligodendroglioma tumors upon diagnosis and after tumor relapse based on whole-genome and RNA sequencing. Relapsed tumors were diagnosed as glioblastomas with an oligodendroglioma component before the World Health Organization classification update in 2016. Both patients died within 12 months after relapse. One patient carried an inactivating POLE mutation leading to a clearly hypermutated progressed tumor. Strikingly, both relapsed tumors carried focal chromosomal rearrangements in PTPRD and CNTNAP2 genes with associated decreased gene expression. TP53 mutation was also detected in both patients after tumor relapse. In The Cancer Genome Atlas (TCGA) diffuse glioma cohort, PTPRD and CNTNAP2 expression decreased by tumor grade in oligodendrogliomas and PTPRD expression also in IDH-mutant astrocytomas. Low expression of the genes was associated with poor overall survival. Our analysis provides information about aggressive oligodendrogliomas with worse prognosis and suggests that PTPRD and CNTNAP2 expression could represent an informative marker for their stratification.

miR-124 participates in the proliferation and differentiation of brain glioma stem cells through regulating Nogo/NgR expression

The effect of miR-124 on the proliferation and differentiation of brain glioma stem cells and Nogo/NgR signaling pathway were investigated. miR-124 mimic, miR-124 inhibitor and miR-control expression vector were designed and produced to transfect U87 glioma stem cells. The results of transfection were tested via RT-qPCR and the expression of protein was detected by western blot analysis. Cell proliferation was detected by MTT proliferation and the proportion of CD133⁺ cells was detected by immunomagnetic beads to determine cell differentiation. The correlation between miR-124 and Nogo-A, and NgR protein expression was analyzed by Spearman correlation analysis. The relative expression of miR-124 in cells of miR-124 mimic group was significantly higher than that of miR-124 inhibitor and miR-control groups (P<0.05). The relative expression of Nogo-A and NgR protein in cells of the miR-124 mimic group was significantly lower than that of miR-124 inhibitor and miR-control groups (P<0.05). Absorbance values of the cells in the miR-124 mimic and miR-control groups were significantly lower than those in the miR-124 inhibitor group at each time point (P<0.05), while the values of the cells in the miR-124 mimic group were significantly lower than that in miR-control group (P<0.05). The level of CD133⁺ cells in miR-124 mimic group was significantly lower than that in miR-124 inhibitor and miR-control groups (P<0.05), while the level of CD133⁺ cells in miR-124 inhibitor group was higher than that in miR-control group (P<0.05). Correlation analysis revealed that there was a negative correlation between miR-124 and the expression of Nogo-A and NgR protein (P<0.05). miR-124 may participate in the differentiation of brain glioma stem cells through the Nogo/NgR pathway, which may bring a new direction for the clinical treatment of brain glioma.