An identification of stem cell-resembling gene expression profiles in high-grade astrocytomas

Enrichment of oligodendrocyte precursor phenotypes in subsets of low-grade glioneuronal tumours

Current histological classification of low-grade glioneuronal tumours does not adequately represent their underlying biology. The neural lineage(s) and differentiation stage(s) involved and the cell state(s) affected by the recurrent genomic alterations are unclear. Here, we describe dysregulated oligodendrocyte lineage developmental programmes in three low-grade glioneuronal tumour subtypes. Ten dysembryoplastic neuroepithelial tumours, four myxoid glioneuronal tumours and five rosette-forming glioneuronal tumours were collected. Besides a comprehensive characterization of clinical features, known diagnostic markers and genomic alterations, we used comprehensive immunohistochemical stainings to characterize activation of rat sarcoma/mitogen-activated protein kinase pathway, involvement of neuronal component, resemblance to glial lineages and differentiation blockage along the stages of oligodendrocyte lineage. The findings were further complemented by gene set enrichment analysis with transcriptome data of dysembryoplastic neuroepithelial tumours from the literature. Dysembryoplastic neuroepithelial tumours, myxoid glioneuronal tumours and rosette-forming glioneuronal tumours occur at different ages, with symptoms closely related to tumour location. Dysembryoplastic neuroepithelial tumours and myxoid glioneuronal tumours contain oligodendrocyte-like cells and neuronal component. Rosette-forming glioneuronal tumours contained regions of rosette-forming neurocytic and astrocytic features. Scattered neurons, identified by neuronal nuclei antigen and microtubule-associated protein-2 staining, were consistently observed in all dysembryoplastic neuroepithelial tumours and myxoid glioneuronal tumours examined, but only in one rosette-forming glioneuronal tumour. Pervasive neurofilament-positive axons were observed only in dysembryoplastic neuroepithelial tumour and myxoid glioneuronal tumour samples. Alterations in B-Raf proto-oncogene, serine/threonine kinase, fibroblast growth factor receptor 1, fibroblast growth factor receptor 3 and platelet-derived growth factor receptor alpha occurred in a mutually exclusive manner, coinciding with strong staining of phospho-p44/42 mitogen-activated protein kinase and low apoptotic signal. All dysembryoplastic neuroepithelial tumours, myxoid glioneuronal tumours and the neurocytic regions of rosette-forming glioneuronal tumours showed strong expression of neuron-glia antigen 2, platelet-derived growth factor receptor alpha (markers of oligodendrocyte precursor cells) and neurite outgrowth inhibitor-A (a marker of developing oligodendrocytes), but lacked the expression of oligodendrocyte markers ectonucleotide pyrophosphatase/phosphodiesterase family member 6 and myelin basic protein. Notably, transcriptomes of dysembryoplastic neuroepithelial tumours were enriched in oligodendrocyte precursor cell signature, but not in signatures of neural stem cells, myelinating oligodendrocytes and astrocytes. Dysembryoplastic neuroepithelial tumour, myxoid glioneuronal tumour and rosette-forming glioneuronal tumour resemble oligodendrocyte precursor cells, and their enrichment of oligodendrocyte precursor cell phenotypes is closely associated with the recurrent mutations in rat sarcoma/mitogen-activated protein kinase pathway.

Formins in Human Disease

Almost 25 years have passed since a mutation of a formin gene, DIAPH1, was identified as being responsible for a human inherited disorder: a form of sensorineural hearing loss. Since then, our knowledge of the links between formins and disease has deepened considerably. Mutations of DIAPH1 and six other formin genes (DAAM2, DIAPH2, DIAPH3, FMN2, INF2 and FHOD3) have been identified as the genetic cause of a variety of inherited human disorders, including intellectual disability, renal disease, peripheral neuropathy, thrombocytopenia, primary ovarian insufficiency, hearing loss and cardiomyopathy. In addition, alterations in formin genes have been associated with a variety of pathological conditions, including developmental defects affecting the heart, nervous system and kidney, aging-related diseases, and cancer. This review summarizes the most recent discoveries about the involvement of formin alterations in monogenic disorders and other human pathological conditions, especially cancer, with which they have been associated. In vitro results and experiments in modified animal models are discussed. Finally, we outline the directions for future research in this field.

Knockdown of Diaph1 expression inhibits migration and decreases the expression of MMP2 and MMP9 in human glioma cells

As the most common primary central nervous system tumor, glioma is characterized by high levels of mortality and migration. Unclear boundary with normal brain tissue results in poor treatment. The mammalian diaphanous-related formin 1 (Diaph1) which belongs to formin-homology protein family, is a target of RhoA and involved in a number of actin-related biological processes, which abnormally expressed in pathological conditions in a number of tumors. Immunohistochemical analysis showed that Diaph1 was overexpressed in glioma tissues compared with normal human brain tissue. Diaph1 gene silencing RNA interference (RNAi) significantly inhibited the migratory activity of human glioma cell lines U87 and U251. Moreover, data obtained from qRT-PCR and Western-blot analysis showed that the mRNA and protein expression of matrix metalloproteinase2 and 9 (MMP2 and MMP9) was significantly suppressed in these Diaph1 knockdown cell lines, as well as gelatin zymography analysis revealed that the activity of MMP2 and MMP9 in conditioned medium was markedly decreased. In conclusion, our data demonstrate that Diaph1 is highly expressed in human glioma, plays a significant role in glioma cell migration, and can influence the expression and activity of MMP2 and MMP9 indirectly in human glioma cell lines U87 and U251. We provide a theoretical basis for further experimental studies and Diaph1 using on glioma therapy.

Caspase-related apoptosis genes in gliomas by RNA-seq and bioinformatics analysis

Gliomas are the most common malignant tumors of the brain. The aim of this study is to identify caspase-dependent apoptotic genes and uncover their potential regulatory mechanism in glioma progression. Human glioma cell line U251 was used. Three experiment groups were set as control group, H₂O₂ group (treated with H₂O₂) and caspase inhibitor group (treated with caspase inhibitor). For samples in each group, RNA-sequencing was performed on Illumina platform and differentially expressed genes (DEGs) between any two of the three groups were selected using NOISeq package. By overlapping analysis, the caspase inhibitor-related DEGs were further screened out, followed by enrichment analyses. Drugs associating with these genes were selected by WebGestalt. Protein-protein interaction (PPI) network analysis was conducted based on SRINIG database. A set of 105 caspase inhibitor-related DEGs were identified, which were significantly enriched in cellular components related functions (for example, TUBB2A, RPSA and RPL5); and metabolism related pathways (for example, PSMC3, KHSRP, RPL5 and RPSA). In addition, KHSRP and TUBB2A were significantly associated with several drugs such as cefotaxime, cefacetrile and netilmicin. Besides, PSMC3 and RPL5 were identified as crucial nodes in the PPI network. Several crucial genes in gliomas cells such as TUBB2A, RPSA, RPL5, PSMC3 and KHSRP were identified, which might play significant roles in apoptosis in a caspase-dependent manner. These genes might also involve in the regulation of metabolism related functions and pathways. KHSRP and TUBB2A might be novel targets of three drugs, cefotaxime, cefacetrile and netilmicin.

Epigallocatechin-3-gallate induces apoptosis, inhibits proliferation and decreases invasion of glioma cell

Epigallocatechin-3-gallate (EGCG), a major polyphenol in green tea, has been considered a potential therapeutic and chemopreventive agent for cancer. Glioma is a malignant tumor with high mortality but effective therapy has not yet been developed. In this study, we found that EGCG induced apoptosis in U251 glioma cells via the laminin receptor (molecular weight 67 kDa) in a time- and dose-dependent manner, decreased their invasiveness and inhibited their proliferation. The mitogen-activated protein kinase pathway was shown to be involved in glioma cell apoptosis and proliferation. Furthermore, the mRNA levels of matrix metalloproteinase (MMP)-2 and MMP-9 were reduced after EGCG treatment. These results suggest that EGCG has important therapeutic effects with low toxicity and side-effects, and could be used in cancer chemoprevention.

Targeting Stat3 suppresses growth of U251 cell-derived tumours in nude mice

Malignant gliomas are highly invasive tumours associated with high levels of mortality, and the treatment of gliomas remains a major neurosurgical challenge. Stat3, a member of the signal transducer and activator of transcription family, has a critical role in a variety of cancer cells. We have previously shown that downregulation of Stat3 decreases invasiveness and induces apoptosis in U251 human glioma cells in vitro, but to date it has been unclear whether this treatment would be beneficial in vivo. In the present study, we found that downregulation of Stat3 via RNAi suppressed tumour growth in a xenograft mouse model by inducing apoptosis of U251 tumour cells and inhibiting tumour neo-angiogenesis. We also found that Stat3 RNAi suppresses the expression of Bcl-2 in vivo to induce apoptosis. These results indicate that Stat3 is a critical factor in the survival of patients with glioma, and that targeting Stat3 may offer a potential therapeutic approach.