Construction and validation of a risk model based on the key SNARE proteins to predict the prognosis and immune microenvironment of gliomas.

Background: Synaptic transmission between neurons and glioma cells can promote glioma progression. The soluble N-ethylmaleimide-sensitive fusion factor attachment protein receptors (SNARE) play a key role in synaptic functions. We aimed to construct and validate a novel model based on the SNARE proteins to predict the prognosis and immune microenvironment of glioma. Methods: Differential expression analysis and COX regression analysis were used to identify key SRGs in glioma datasets, and we constructed a prognostic risk model based on the key SRGs. The prognostic value and predictive performance of the model were assessed in The Cancer Genome Atlas (TCGA) and Chinese glioma Genome Atlas (CGGA) datasets. Functional enrichment analysis and immune-related evaluation were employed to reveal the association of risk scores with tumor progression and microenvironment. A prognostic nomogram containing the risk score was established and assessed by calibration curves and time-dependent receiver operating characteristic curves. We verified the changes of the key SRGs in glioma specimens and cells by real-time quantitative PCR and Western blot analyses. Results: Vesicle-associated membrane protein 2 (VAMP2) and vesicle-associated membrane protein 5 (VAMP5) were identified as two SRGs affecting the prognoses of glioma patients. High-risk patients characterized by higher VAMP5 and lower VAMP2 expression had a worse prognosis. Higher risk scores were associated with older age, higher tumor grades, IDH wild-type, and 1p19q non-codeletion. The SRGs risk model showed an excellent predictive performance in predicting the prognosis in TCGA and CGGA datasets. Differentially expressed genes between low- and high-risk groups were mainly enriched in the pathways related to immune infiltration, tumor metastasis, and neuronal activity. Immune score, stromal score, estimate score, tumor mutational burden, and expression of checkpoint genes were positively correlated with risk scores. The nomogram containing the risk score showed good performance in predicting the prognosis of glioma. Low VAMP2 and high VAMP5 were found in different grades of glioma specimens and cell lines. Conclusion: We constructed and validated a novel risk model based on the expression of VAMP2 and VAMP5 by bioinformatics analysis and experimental confirmation. This model might be helpful for clinically predicting the prognosis and response to immunotherapy of glioma patients.

Drug repositioning: Using psychotropic drugs for the treatment of glioma.

Psychotropic drugs can penetrate the blood-brain barrier and regulate the levels of neurotransmitters and neuromodulators such as γ-aminobutyric acid, glutamate, serotonin, dopamine, and norepinephrine in the brain, and thus influence neuronal activity. Neuronal activity in the tumor microenvironment can promote the growth and expansion of glioma. There is increasing evidence that in addition to their use in the treatment of mental disorders, antipsychotic, antidepressant, and mood-stabilizing drugs have clinical potential for cancer therapy. These drugs have been shown to inhibit the malignant progression of glioma by targeting signaling pathways related to cell proliferation, apoptosis, or invasion/migration or by increasing the sensitivity of glioma cells to conventional chemotherapy or radiotherapy. In this review, we summarize findings from preclinical and clinical studies investigating the use of antipsychotics, antidepressants, and mood stabilizers in the treatment of various types of cancer, with a focus on glioma; and discuss their presumed antitumor mechanisms. The existing evidence indicates that psychotropic drugs with established pharmacologic and safety profiles can be repurposed as anticancer agents, thus providing new options for the treatment of glioma.

Autophagy Inhibition by ATG3 Knockdown Remits Oxygen-Glucose Deprivation/Reoxygenation-Induced Injury and Inflammation in Brain Microvascular Endothelial Cells.

Autophagy participates in the development of cerebral ischemia stroke. Autophagy-related 3 (ATG3), an important autophagy regulator, was reported to be upregulated in a rat model of cerebral ischemia/reperfusion (CI/R) injury and an oxygen-glucose deprivation/reoxygenation (OGD/R) cell model. However, the detailed role of ATG3 in CI/R injury remains elusive. An in vitro cellular model was established to mimic CI/R injury by exposing hBMECs and bEnd.3 cells to OGD/R. OGD/R-induced injury were evaluated by cell counting kit-8 (CCK-8), LDH release assay, caspase-3 activity assay and TUNEL assay. Inflammation was assessed by detecting mRNA expression and concentrations of interleukin-1ß (IL-1ß), IL-6 and tumor necrosis factor-α (TNF-α) using qRT-PCR and ELISA, respectively. The protein levels of ATG3, light chain 3 (LC3)-I, LC3-II, p62, protein kinase B (Akt), and phosphorylated Akt (p-Akt) were determined by western blot analysis. We successfully established an in vitro OGD/R injury model using hBMECs and bEnd.3 cells. ATG3 was time-dependently upregulated and ATG3 knockdown inhibited autophagy in OGD/R-challenged brain microvascular endothelial cells. Moreover, autophagy inhibition by ATG3 interference attenuated OGD/R-induced viability inhibition and increase of LDH release, caspase-3 activity, programmed cell death, and production of IL-1ß, IL-6 and TNF-α. Inhibition of autophagy by ATG3 silencing activated the phosphoinositide 3-kinase (PI3K)/Akt pathway in OGD/R-challenged brain microvascular endothelial cells. Furthermore, inhibition of the PI3K/Akt pathway reversed the protective effects of ATG3 silencing on OGD/R-induced injury and inflammation. In conclusion, autophagy inhibition by ATG3 knockdown remitted OGD/R-induced injury and inflammation in brain microvascular endothelial cells via activation of the PI3K/Akt pathway.

NPAS4 suppresses propofol-induced neurotoxicity by inhibiting autophagy in hippocampal neuronal cells.

Propofol, a general intravenous anesthetic, has been demonstrated to cause a profound neuroapoptosis in the developing brain followed by long-term neurocognitive impairment. Our study aimed to examine the neuroprotective effect of neuronal PAS domain protein 4 (NPAS4), an activity-dependent neuron-specific transcription factor, on propofol-induced neurotoxicity in hippocampal neuronal HT22 cells. The differentially expressed genes in HT22 cells after treatment with propofol were screened from Gene Expression Omnibus dataset GSE106799. NPAS4 expression in HT22 cells treated with different doses of propofol was investigated by qRT-PCR and Western blot analysis. Cell viability, lactate dehydrogenase (LDH) release, caspase-3 activity, and apoptosis were evaluated by MTT, a LDH-Cytotoxicity Assay Kit, a Caspase-3 Colorimetric Assay Kit, and TUNEL assay, respectively. The protein levels of LC3-I, LC3-II, Beclin 1, p62 and NPAS4 were detected using Western blot analysis. Propofol treatment concentration-dependently decreased NPAS4 expression in HT22 cells. Propofol treatment inhibited cell viability, increased LDH release and caspase-3 activity, and induced apoptosis and autophagy in HT22 cells. NPAS4 overexpression suppressed propofol-induced cell injury and autophagy in HT22 cells. Mechanistically, autophagy agonist rapamycin attenuated the neuroprotective effect of NPAS4 in propofol-treated HT22 cells. In conclusion, NAPS4 overexpression protected hippocampal neuronal HT22 cells against propofol-induced neurotoxicity by reducing autophagy.

SRY-Box 21 Antisense RNA 1 Knockdown Diminishes Amyloid Beta25-35-Induced Neuronal Damage by miR-132/PI3K/AKT Pathway.

Our study aimed to explore the function and mechanism of action of long noncoding RNA (lncRNA) SRY-Box 21 antisense RNA 1 (SOX21-AS1) in amyloid beta25-35 (Aß25-35)-induced neuronal damage. To induce neuronal damage, neuronal cells and differentiated IMR-32 neuroblastoma cells were challenged by Aß25-35. SOX21-AS1 and miR-132 quantities were detected by quantitative reverse transcription polymerase chain reaction. Cell damage was evaluated by detecting the changes of cell viability, apoptosis, and oxidative stress. Cell viability was measured using cell counting kit-8. Cell apoptosis was evaluated by flow cytometry and caspase-3 activity. The oxidative stress was analyzed by reactive oxygen species level. The expression of proteins associated with the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway was examined by western blot. SOX21-AS1 abundance was up-regulated in Aß25-35-challenged neuronal cells. Silencing of SOX21-AS1 attenuated Aß25-35-induced viability reduction and promotion of apoptosis and oxidative stress, suggesting that silencing of SOX21-AS1 repressed Aß25-35-induced neuronal damage. miR-132 quantity was reduced in Aß25-35-challenged neuronal cells, and negatively controlled by SOX21-AS1. miR-132 knockdown abolished the effect of SOX21-AS1 silencing on Aß25-35-induced neuronal damage, indicating that SOX21-AS1 controls Aß25-35-induced neuronal damage via regulating miR-132. The PI3K/AKT signaling was repressed in Aß25-35-challenged cells, but this effect was counteracted upon overexpression of miR-132. In conclusion, SOX21-AS1 knockdown mitigated Aß25-35-dependent neuronal cell damage by promoting miR-132/PI3K/AKT pathway.

The nuclear transporter importin-11 regulates the Wnt/ß-catenin pathway and acts as a tumor promoter in glioma.

Karyopherins mediate the macromolecular transport between the cytoplasm and the nucleus and participate in cancer progression. However, the role and mechanism of importin-11 (IPO11), a member of the karyopherin family, in glioma progression remain undefined. Effects of IPO11 on glioma progression were detected using CCK-8, colony formation assay, flow cytometry analysis, caspase-3 activity assay, and Transwell invasion assay. Western blot analysis was used to detect the expression of active caspase-3, active caspase-7, active caspase-9, N-cadherin, Vimentin, E-cadherin, ß-catenin, and c-Myc. The activity of Wnt/ß-catenin pathway was evaluated by the T-cell factor/lymphoid enhancer factor (TCF/LEF) transcription factor reporter assay. Results showed that IPO11 knockdown inhibited proliferation and reduced colony number in glioma cells. IPO11 silencing promoted the apoptotic rate, increased expression levels of active caspase-3, caspase-7, and caspase-9, and enhanced caspase-3 activity. Moreover, IPO11 silencing inhibited glioma cell invasion by suppressing epithelial-to-mesenchymal transition (EMT). Mechanistically, IPO11 knockdown inactivated the Wnt/ß-catenin pathway. ß-Catenin overexpression abolished the effects of IPO11 silencing on the proliferation, apoptosis, and invasion in glioma cells. Furthermore, IPO11 silencing blocked the malignant phenotypes and repressed the Wnt/ß-catenin pathway in vivo. In conclusion, IPO11 knockdown suppressed the malignant phenotypes of glioma cells by inactivating the Wnt/ß-catenin pathway.

SMAGP knockdown inhibits the malignant phenotypes of glioblastoma cells by inactivating the PI3K/Akt pathway.

Small trans-membrane and glycosylated protein (SMAGP), a novel small trans-membrane glycoprotein, is reported to be upregulated in multiple cancers and involved in tumor development. However, little is known about its role in the development of glioblastoma (GBM). GEPIA database was used to analyze SMAGP expression and evaluate the prognostic value of SMAGP in GBM. GO and KEGG pathway enrichment analyses were used to predict the biological functions and pathways of SMAGP and 948 SMAGP-correlated genes using DAVID database. Cell viability, colony formation ability, apoptosis, and invasion were evaluated by MTT, colony formation assay, flow cytometry analysis, and Transwell invasion assay, respectively. Western blot was applied to detect the expression of SMAGP, matrix metalloproteinase (MMP)-2, and MMP-9 and analyze the changes of phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling. Results showed that SMAGP was upregulated and correlated with poor prognosis in GBM. Functional annotation analysis revealed that SMAGP and 948 SMAGP-correlated genes were primarily associated with cell adhesion and PI3K/Akt pathway. SMAGP interference inhibited cell viability and colony formation ability and promoted apoptosis in GBM cells. Moreover, SMAGP interference inhibited GBM cell invasion and suppressed MMP-2 and MMP-9 expression. Additionally, SMAGP silencing inhibited the PI3K/Akt pathway in GBM cells. Overexpression of Akt abolished the effects of SMAGP knockdown on the malignant phenotypes of GBM cells. In conclusion, SMAGP silencing inhibited the malignant phenotypes of GBM cells by inactivating the PI3K/Akt pathway.

RIOK2 is negatively regulated by miR-4744 and promotes glioma cell migration/invasion through epithelial-mesenchymal transition.

RIOK2 is a member of RIO (right open reading frame) kinase family. Recent studies have revealed the involvement of RIO kinases in glioma cell growth and expansion. However, the role and mechanism of RIOK2 in glioma cell migration and invasion remain unclear. Wound healing assay, Transwell assay and real-time quantitative PCR (qRT-PCR) detection of matrix metalloproteinases (MMPs) were used to evaluate the migration/invasion of glioma cells. Western blot and qRT-PCR were employed to measure the expression of epithelial-mesenchymal transition (EMT) markers. Dual luciferase reporter assay was performed to determine the binding between RIOK2 and miR-4744. In addition, RIOK2 and miR-4744 levels were quantified by qRT-PCR and/or immunohistochemistry in glioma tissues. Transfection of RIOK2 siRNAs significantly inhibited glioma cell migration and invasion and down-regulated the expression of MMPs (MMP2 and MMP9) and mesenchymal markers (N-cadherin, ß-catenin, Twist1, fibronectin, ZEB-1) in glioma cells. Overexpression of RIOK2 showed the opposite effects. MiR-4744 directly bound to the 3'-untranslated region of RIOK2 and negatively regulated the expression of RIOK2. Up-regulation of miR-4744 inhibited the migration and invasion of glioma cells. Overexpression of RIOK2 could reverse the effects of miR-4744 up-regulation on the migration, invasion and EMT process in glioma cells. Moreover, RIOK2 was high, while miR-4744 was low in glioma tissues, and a negative correlation was found between them. These results suggest that RIOK2 is post-transcriptionally targeted by miR-4744, the low miR-4744 and high RIOK2 levels in glioma may contribute to tumour cell infiltration through promoting the EMT.

Effects of Long Form of CAPON Overexpression on Glioma Cell Proliferation are Dependent on AKT/mTOR/P53 Signaling.

Background: CAPON has two isoforms in human brain: long form of CAPON (CAPON-L) and short form of CAPON (CAPON-S). Recent studies have indicated the involvement of CAPON in tumor cell growth. We aimed to reveal the role of the two CAPON isoforms in the proliferation of glioma cells in this study. Materials and Methods: Lentivirus-mediated stable cell lines with CAPON-L or CAPON-S overexpression were established in U87 and U251 glioma cells. Cell counting kit-8 and colony formation assays were used to evaluate cell proliferation. Western blot analysis of cell cycle-related proteins and flow cytometry were performed to analyze cell cycle progression. Some important molecules of the AKT/mTOR pathway and P53 were also measured by Western blot analysis. Results: Overexpression of CAPON-L showed a significantly inhibitory role in U251 cells, while it exhibited a promoting role in U87 cells. Consistently, overexpressing CAPON-L impeded the cell cycle progression and down-regulated the expression levels of Cyclin D1, CDK4 and CDK6 in U251 cells, whereas it up-regulated the CDK6 level in U87 cells. The overexpression of CAPON-L significantly decreased the phosphorylation and/or total levels of AKT, mTOR and S6 in U251 cells, while it did not affect these signaling molecules in U87 cells, except for a significant increase in the phosphorylation of AKT at Thr-308 site. Transfecting constitutively active AKT (myr-AKT) partially reversed the decreased phosphorylation of AKT and S6 in the CAPON-L-overexpressing U251 cells. In addition, we found a significant decrease in the wild-type P53 level in the CAPON-L-overexpressing U87 cells. The overexpression of CAPON-S also inhibited cell proliferation, blocked cell cycle progression, and decreased the AKT/mTOR pathway activity in U251 cells. Conclusion: The effects of CAPON-L overexpression on glioma cell proliferation are dependent on the AKT/mTOR/P53 activity. The overexpression of CAPON inhibits U251 cell proliferation through the AKT/mTOR signaling pathway, while overexpressing CAPON-L promoted U87 cell proliferation, possibly through down-regulating the P53 level.

The atypical protein kinase RIOK3 contributes to glioma cell proliferation/survival, migration/invasion and the AKT/mTOR signaling pathway.

The RIO (right open reading frame) protein kinases include RIOK1, RIOK2 and RIOK3. Emerging evidence has suggested an important role of RIO kinases in cancer cell proliferation, apoptosis, migration and invasion. However, the expression profile and specific roles of RIOK3 are largely unknown during glioma progression. In the current study, quantitative real-time PCR, Western blot, and immunohistochemical analysis showed that RIOK3 was upregulated in glioma tissues. Available database analysis revealed that higher levels of RIOK3 were associated with poorer survival outcome in glioma patients. Flow cytometry, CCK8 and EdU assays showed that downregulation of RIOK3 arrested cell cycle progression and inhibited glioma cell proliferation. Wound healing, transwell and gelatin zymography assays revealed that silencing RIOK3 decreased glioma cell migration and invasion. Furthermore, the downregulation of RIOK3 significantly decreased the activity of AKT/mTOR signaling and induced apoptosis in glioma cells. Overexpression of RIOK3 showed the opposite effects on glioma cell proliferation, migration, invasion and the AKT/mTOR pathway. These results indicate that high RIOK3 levels in gliomas appear to contribute to the growth and expansion of this cancer, and may thus serve as a novel therapeutic target.

Effects of ERK1/2 S-nitrosylation on ERK1/2 phosphorylation and cell survival in glioma cells.

Aberrant activation of extracellular signal­regulated kinase 1/2 (ERK1/2) by phosphorylation modification can trigger tumor cell development in glioma. S­nitrosylation, which refers to the covalent addition of a nitric oxide (NO) group to a cysteine (Cys) thiol, is an important post­translational modification that occurs on numerous cancer­associated proteins. Protein S­nitrosylation can increase or decrease protein activity and stability, and subsequent signal transduction and cellular processes. However, the association between ERK1/2 S­nitrosylation and ERK1/2 phosphorylation, and the effects of ERK1 S­nitrosylation on glioma cell survival are currently unknown. U251 glioma cells were treated with NO donors sodium nitroprusside (SNP) or S­nitrosoglutathione (GSNO). CCK8 assay was used to assess the cell viability. NO levels in the medium were detected by Griess assay. Western blot analysis and biotin switch assay were employed to detect the ERK1/2 phosphorylation and S-nitrosylation. ERK1 wild-type and mutant plasmids were constructed, and used to transfect the U251 cells. Caspase-3 western blot analysis and flow cytometry were employed to assess cell apoptosis. The present study demonstrated that treatment with the NO donors SNP or GSNO led to an increase in ERK1/2 S­nitrosylation, and a reduction in ERK1/2 phosphorylation, which was accompanied by growth inhibition of U251 glioma cells. Mutational analysis demonstrated that Cys183 was vital for S­nitrosylation of ERK1, and that preventing ERK1 S­nitrosylation by replacing Cys183 with alanine partially reversed GSNO­induced cell apoptosis, and reductions in cell viability and ERK1/2 phosphorylation. In addition, increased ERK1/2 phosphorylation was associated with decreased ERK1/2 S­nitrosylation in human glioma tissues. These findings identified the relationship between ERK1/2 S­nitrosylation and phosphorylation in vitro and in vivo, and revealed a novel mechanism of ERK1/2 underlying tumor cell development and apoptotic resistance of glioma.

Low Expression of CAPON in Glioma Contributes to Cell Proliferation via the Akt Signaling Pathway.

CAPON is an adapter protein for nitric oxide synthase 1 (NOS1). CAPON has two isoforms in the human brain: CAPON-L (long form of CAPON) and CAPON-S (short form of CAPON). Recent studies have indicated the involvement of CAPON in tumorigenesis beyond its classical role in NOS1 activity regulation. In this study, we found that the protein levels of CAPON-S, but not than CAPON-L, were significantly decreased in glioma tissues. Therefore, we established lentivirus-mediated stable cell lines with CAPON-S overexpression or down-regulation, and investigated the role of CAPON-S in the proliferation of glioma cells by using CCK8, EdU, and flow cytometry assays. Overexpression of CAPON-S reduced the cell variability and the percentage of EdU-positive cells, and arrested the cells in the G1 phase in glioma cells. Silencing of CAPON by short-hairpin RNA showed the opposite effects. Furthermore, an intracellular signaling array revealed that overexpression of CAPON-S resulted in a remarkable reduction in the phosphorylation of Akt and S6 ribosomal protein in glioma cells, which was further confirmed by Western blot. These findings suggest that CAPON may function as a tumor suppressor in human brain glioma and that the inactivation of the Akt signaling pathway caused by CAPON-S overexpression may provide insight into the underlying mechanism of CAPON in glioma cell proliferation.