Molecular mechanism of Notch signaling with special emphasis on microRNAs: Implications for glioma

Regulation of Notch1 Signalling by Long Non-Coding RNAs in Cancers and Other Health Disorders

Notch1 signalling plays a multifaceted role in tissue development and homeostasis. Currently, due to the pivotal role of Notch1 signalling, the relationship between NOTCH1 expression and the development of health disorders is being intensively studied. Nevertheless, Notch1 signalling is not only controlled at the transcriptional level but also by a variety of post-translational events. First is the ligand-dependent mechanical activation of NOTCH receptors and then the intracellular crosstalk with other signalling molecules-among those are long non-coding RNAs (lncRNAs). In this review, we provide a detailed overview of the specific role of lncRNAs in the modulation of Notch1 signalling, from expression to activity, and their connection with the development of health disorders, especially cancers.

Irigenin inhibits glioblastoma progression through suppressing YAP/β-catenin signaling

Glioblastoma (GBM) is the most malignant glioma in brain tumors with low survival and high recurrence rate. Irigenin, as an isoflavone compound extracted from Shegan, has shown many pharmacological functions such as antioxidant, anti-inflammatory and anti-tumor. However, the effects of irigenin on GBM cells and the related molecular mechanisms remain unexplored. In this study, we found that irigenin inhibited the proliferation of GBM cells in a dose-dependent manner by several assays in vitro. Subsequently, we found that irigenin arrested cell cycle at G2/M phase and induced apoptosis of GBM cells in vitro. In addition, irigenin inhibited the migration of GBM cells. Mechanically, we found that irigenin treatment decreased the expression of YAP (yes-associated protein), suppressed β-catenin signaling. Furthermore, overexpression of YAP partially restored the anti-tumor effects of irigenin on GBM cells in vitro. Finally, we found that irigenin inhibited the growth of tumor in GBM xenograft mice model through inactivation of YAP. Taken together, these results suggest that irigenin exerts its anticancer effects on GBM via inhibiting YAP/β-catenin signaling, which may provide a new strategy for the treatment of GBM.

Natural products in suppressing glioma progression: A focus on the role of microRNAs

Glioma is one of the most common malignancies of the central nervous system. Due to inadequate response to the current treatments available, glioma has been at the center of recent cancer studies searching for novel treatment strategies. This has prompted an intensive search using linkage studies and preliminary evidence to gain efficient insight into the mechanisms involved in the alleviation of the pathogenesis of glioma mediated by miRNAs, a group of noncoding RNAs that affect gene expression posttranscriptionally. Dysregulated expression of miRNAs can exacerbate the malignant features of tumor cells in glioma and other cancers. Natural products can exert anticancer effects on glioma cells by stimulating the expression levels of tumor suppressor miRNAs and repressing the expression levels of oncogenic miRNAs. In this review, we aimed to collect and analyze the literature addressing the roles of natural products in the treatment of glioma, with an emphasis on their involvement in the regulation of miRNAs.

MicroRNA-3148 inhibits glioma by decreasing DCUN1D1 and inhibiting the NF-kB pathway

Glioma, which originates in the brain, is the most aggressive tumor of the central nervous system. It has been shown that microRNA (miRNA) controls the proliferation, migration and apoptosis of glioma cells. The objective of the present study was to measure microRNA-3148 (miR-3148) expression and investigate its impact on the pathogenetic mechanism of glioma. In the present study, reverse transcription-quantitative real-time PCR was employed to detect miR-3148 expression levels in glioma tissues and cell lines. Cell Counting Kit-8 assay, 5-ethynyl-2'-deoxyuridine assay, and Transwell migration assay were performed to assess the influence of miR-3148 on the malignant biological behavior of glioma cells. The biological functions of miR-3148 in glioma were examined via a xenograft tumor growth assay. Furthermore, the association between miR-3148 and DCUN1D1 was investigated via immunohistochemistry, dual-luciferase reporter assay and western blotting. It was observed that miR-3148 was expressed at low levels in glioma cells, and this represented a poor survival rate. In addition, an increased level of miR-3148 in cells and animal models inhibited glioma cell migration and proliferation. Moreover, miR-3148 decreased DCUN1D1 and curbed the nuclear factor κ enhancer binding protein (NF-κB) signaling pathway, thus decreasing the growth of glioma. Thus, miR-3148 is expressed within glioma tissues at low levels where it suppresses glioma by curbing the NF-κB pathway and lowering DCUN1D1.

Targeting Notch to Maximize Chemotherapeutic Benefits: Rationale, Advanced Strategies, and Future Perspectives

Simple Summary

The Notch signaling pathway regulates cell proliferation, apoptosis, stem cell self-renewal, and differentiation in a context-dependent fashion both during embryonic development and in adult tissue homeostasis. Consistent with its pleiotropic physiological role, unproper activation of the signaling promotes or counteracts tumor pathogenesis and therapy response in distinct tissues. In the last twenty years, a wide number of studies have highlighted the anti-cancer potential of Notch-modulating agents as single treatment and in combination with the existent therapies. However, most of these strategies have failed in the clinical exploration due to dose-limiting toxicity and low efficacy, encouraging the development of novel agents and the design of more appropriate combinations between Notch signaling inhibitors and chemotherapeutic drugs with improved safety and effectiveness for distinct types of cancer.

Abstract

Notch signaling guides cell fate decisions by affecting proliferation, apoptosis, stem cell self-renewal, and differentiation depending on cell and tissue context. Given its multifaceted function during tissue development, both overactivation and loss of Notch signaling have been linked to tumorigenesis in ways that are either oncogenic or oncosuppressive, but always context-dependent. Notch signaling is critical for several mechanisms of chemoresistance including cancer stem cell maintenance, epithelial-mesenchymal transition, tumor-stroma interaction, and malignant neovascularization that makes its targeting an appealing strategy against tumor growth and recurrence. During the last decades, numerous Notch-interfering agents have been developed, and the abundant preclinical evidence has been transformed in orphan drug approval for few rare diseases. However, the majority of Notch-dependent malignancies remain untargeted, even if the application of Notch inhibitors alone or in combination with common chemotherapeutic drugs is being evaluated in clinical trials. The modest clinical success of current Notch-targeting strategies is mostly due to their limited efficacy and severe on-target toxicity in Notch-controlled healthy tissues. Here, we review the available preclinical and clinical evidence on combinatorial treatment between different Notch signaling inhibitors and existent chemotherapeutic drugs, providing a comprehensive picture of molecular mechanisms explaining the potential or lacking success of these combinations.

Safety and Efficacy Assessments to Take Antioxidants in Glioblastoma Therapy: From In Vitro Experiences to Animal and Clinical Studies

Glioblastoma (GBM) is considered one of the most common malignant brain tumors, occurring as over 15% of all primary central nervous system and brain neoplasms. The unique and standard treatment option towards GBM involves the combination of surgical resection followed by radiotherapy (RT) and chemotherapy (CT). However, due to the aggressive nature and heterogeneity of GBMs, they remained difficult to treat. Recent findings from preclinical studies have revealed that disruption of the redox balance via using either oxidative or anti-oxidative agents in GBM presented an effective and promising therapeutic approach. A limited number of clinical trials substantially encouraged their concomitant use with RT or CT. Thus, treatment of GBMs may benefit from natural or synthetic antioxidative compounds as novel therapeutics. Despite the presence of variegated in vitro and in vivo studies focusing on safety and efficacy issues of these promising therapeutics, nowadays their translation to clinics is far from applicability due to several challenges. In this review, we briefly introduce the enzymatic and non-enzymatic antioxidant defense systems as well as potential signaling pathways related to the pathogenesis of GBM with a special interest in antioxidant mechanisms. In addition, we describe the advantages and limitations of antioxidant supplementation in GBM cases or disease models as well as growing challenges for GBM therapies with antioxidants in the future.

Inhibition of EMMPRIN by microRNA-124 suppresses the growth, invasion and tumorigenicity of gliomas

MicroRNAs (miR) are a group of non-coding, small RNAs, 18-20 nucleotides in length, that are frequently involved in the development of a variety of different types of cancer, including glioma, which is a type of severe tumor in the brain. Previous studies reported that miR-124 levels were downregulated in glioma specimens; however, the potential role of miR-124 in glioma currently remains unclear. The present study performed experiments, including dual-luciferase reporter assay (DLRA), MTT assay, transwell assay and flow cytometry, with the aim of elucidating the molecular mechanism of miR-124 in glioma. The results indicated that miR-124 expression was decreased in glioma tissues, accompanied by the increased expression of extracellular matrix metalloproteinase inducer (EMMPRIN). The expression of EMMPRIN was inhibited by miR-124 transfection. The DLRA results revealed that EMMPRIN directly targets miR-124. Furthermore, upon overexpression of miR-124 in the U87 cells, cell proliferation was significantly inhibited, apoptosis was increased, and cell migration and invasion were decreased. Furthermore, tumor growth was blocked by miR-124 in mice. Based on these results, the present study concluded that miR-124 is critical for amelioration of glioma by targeting EMMPRIN, thereby acting as a tumor suppressor. Thus, miR-124/EMMPRIN constitutes a plausible basis for the treatment of glioma.

LncRNA LINC01410 Induced by MYC Accelerates Glioma Progression via Sponging miR-506-3p and Modulating NOTCH2 Expression to Motivate Notch Signaling Pathway

Glioma is a common invasive cancer with unfavorable prognosis in patients. Long non-coding RNAs have been reported to participate in modulating diverse cellular processes. Here, we focused on exploring the role of long intergenic non-protein coding RNA 1410 (LINC01410) in glioma and its underlying mechanism. The expression levels and protein levels of genes were analyzed by quantitative real-time PCR (RT-qPCR) analysis and western blot. Loss-of-function assays were performed to assess the function of LINC01410 in glioma cells. The interactions among MYC, LINC01410, microRNA-506-3p (miR-506-3p) and notch receptor 2 (NOTCH2) were validated through Chromatin immunoprecipitation (ChIP), RNA Binding Protein immunoprecipitation (RIP), RNA pull-down and luciferase reporter assays. Our data supported that LINC01410 was up-regulated in glioma cells. Bioinformatics predictions and the integrated experiments identified that MYC activated LINC01410 transcription and LINC01410 promoted the levels of NOTCH2 through sponging miR-506-3p and further motivated Notch signaling pathway. Rescue assays validated that LINC01410 exerted its influential functions on glioma cell proliferation and apoptosis via enhancing NOTCH2 expression. Our studies identified that LINC01410 accelerates the progression of glioma through acting as a ceRNA for miR-506-3p and elevating NOTCH2 expression to further activate the Notch signaling pathway, which indicated that LINC01410 might act as a novel regulator of glioma progression.

CircRNA circPTK2 Might Suppress Cancer Cell Invasion and Migration of Glioblastoma by Inhibiting miR-23a Maturation

BACKGROUND

CircRNA circPTK2 plays opposite roles in different cancers, while its role in glioblastoma is unknown. The aim of this study was to explore the involvement of circPTK2 in glioblastoma.

METHODS

Expression of circPTK2, mature miR-23a, and premature miR-23a in paired cancer and non-cancer tissues from glioblastoma patients (n = 60) was analyzed by RT-qPCR. Pearson's correlation coefficient was used to analyze the correlations between gene expressions. The effects of circPTK2 overexpression on miR-23a maturation were analyzed by transfecting circPTK2 expression vector into glioblastoma cells, followed by determining the expression of mature miR-23a and premature miR-23a by RT-qPCR. Transwell assays were carried out to explore the role of circPTK2 and miR-23a in regulating glioblastoma cell invasion and migration.

RESULTS

We found that circPTK2 was downregulated in GBM and was inversely correlated with mature miR-23a, but not premature miR-23a. GBM cells transfected with circPTK2 expression vector showed significantly downregulated mature miR-23a, but not premature miR-23a. Transwell assay analysis showed that circPTK2 overexpression decreased cell invasion and migration, while miR-23a increased cell invasion and migration. Moreover, miR-23a overexpression reversed the inhibitory effects of circPTK2 overexpression on cell behaviors.

CONCLUSION

CircPTK2 might suppress cancer cell invasion and migration by inhibiting the maturation of miR-23a.

NR5A2 Promotes Cell Growth and Resistance to Temozolomide Through Regulating Notch Signal Pathway in Glioma

Background

Glioma is a fatal primary malignant tumor. We aimed to explore the effect of nuclear receptor subfamily 5 group A member 2 (NR5A2) on glioma.

Methods

NR5A2 expression in glioma tissues and cells was detected using qRT-PCR and immunohistochemistry (IHC)/Western blot. SPSS 22.0 was performed to explore the relationship between NR5A2 expression and glioma clinicopathologic features. The down-expressed plasmid of NR5A2 was transfected into glioma cells, and the cell viability, proliferation, apoptosis, migration, and invasion were respectively determined by MTT, EdU, flow cytometry, wound healing and transwell assays. Cell cycle was analyzed using flow cytometry. Temozolomide (TMZ)-resistant glioma cells were established to define the effect of NR5A2 on drug resistance. The expressions of Notch pathway-related proteins were assessed by Western blot. Glioma nude mice model was constructed to explore the role of NR5A2 played in vivo.

Results

NR5A2 was highly expressed in glioma tissues and cell lines. NR5A2 overexpression was related to the poor prognosis of glioma patients. NR5A2 knockdown inhibited cell viability, proliferation, migration, and invasion, induced cell cycle arrest and promoted cell apoptosis in U138 and U251 cells. In U138/TMZ and U251/TMZ cell lines, NR5A2 upregulation enhanced TMZ resistance while NR5A2 downregulation reduced it. The knockdown of NR5A2 influenced the expressions of Notch pathway-related proteins. NR5A2 knockdown suppressed tumor growth and facilitated apoptosis in glioma mice model.

Conclusion

NR5A2 affected glioma cell malignant behaviors and TMZ resistance via Notch signaling pathway and it might be a novel target in glioma therapy.

Prognostic Role of MicroRNA 222 in Patients with Glioma: A Meta-analysis

Background

Several studies have focused on the prognostic role of microRNA 222 in glioma. But different conclusions were drawn by these studies. We aimed to systematically evaluate the role of microRNA 222 in glioma by conducting a meta-analysis.

Methods

A systematic literature search until January 2020 was conducted in Web of Science, EMBASE, Cochrane Library, PubMed, and China National Knowledge Infrastructure. The general characteristics and relevant data of nine articles were extracted. Hazard ratios (HRs) with 95% confidence intervals (CIs) were applied to evaluate the prognostic role of microRNA 222 in glioma. The primary outcomes were overall survival (OS) and disease-free survival (DFS).

Results

Nine articles (11 data sets) with 1564 patients were included. We systematically evaluated the role of microRNA 222 for OS and DFS in glioma patients (HR for OS = 1.72; 95% CI, 1.31-2.26; p = 0.001; HR for DFS = 1.02; 95% CI, 0.86-1.22; p = 0.032). Subgroup analyses were performed according to the sources of patients, the types of the samples, the stages of the tumors, the methods for detecting the microRNA 222, and the sample size. No significant publication bias was found.

Conclusion

In conclusion, our study provided evidence that a high expression of microRNA 222 was related to worse overall survival in glioma patients. However, given the limited study number, more high-quality studies are warranted in the future.

Effects of the MAML2 genetic variants in glioma susceptibility and prognosis

BACKGROUND

Abnormal expression of the mastermind-like transcriptional co-activator 2 (MAML2) gene is oncogenic in several human cancers, including glioma. However, the relevance of MAML2 variants with glioma remains unknown. We aimed to investigate the role of MAML2 polymorphisms in glioma risk and prognosis among the Chinese Han population.

METHODS

Seven MAML2 single-nucleotide polymorphisms (SNPs) were genotyped using Agena MassARRAY system among 575 patients with glioma and 500 age- and gender-matched healthy controls. Logistic regression was used to estimate the association between MAML2 polymorphisms and glioma risk by calculating odds ratios (ORs) and 95% confidence intervals (CI). Kaplan-Meier survival analysis and univariate, multivariate Cox proportional hazard regression analyses for hazard ratios (HRs) and 95% CIs were performed to evaluate the contribution of MAML2 polymorphisms to glioma prognosis.

RESULTS

MAML2 rs7938889 and rs485842 polymorphisms were associated with the reduced risk of glioma (OR = 0.69, P=0.023; and OR = 0.81, P=0.032, respectively). Rs7115578 polymorphism had a lower susceptibility to glioma in males (OR = 0.68, P=0.034), while rs4598633 variant with a higher risk in females (OR = 1.66, P=0.016). Additionally, rs7115578 AG genotype represented a poorer prognosis of glioma (HR = 1.24, P=0.033) and astrocytoma (log-rank P=0.037, HR = 1.31, P=0.036). Furthermore, rs11021499 polymorphism had lower overall survival (OS) and progression-free survival (PFS) in patients with low-grade glioma.

CONCLUSION

We provided some novel data suggesting MAML2 polymorphisms might contribute to glioma risk and prognosis. Future studies are warranted to validate these findings and characterize mechanisms underlying these associations.

MiR-920 and LSP1 co-regulate the growth and migration of glioblastoma cells by modulation of JAK2/STAT5 pathway

This study probes the function and mechanism of lymphocyte-specific protein 1 (LSP1) in glioblastoma pathogenesis. According to the data acquired from TCGA, Oncomine and GEO databases, the expression and prognostic value of LSP1 and miR-920 in glioblastoma patients were analyzed. The expression levels of LSP1 in U251 and A172 cell lines were analyzed by qRT-PCR and western blotting. CCK8, colony formation and transwell assays were utilized to test glioblastoma cell malignant abilities. Furthermore, the associations between LSP1 and miR-920 were indentified by bioinformatics analysis and rescue assays. Moreover, the protein expression levels of p-JAK2, JAK2, p-STAT5 and STAT5, as the hallmark of JAK/STAT5 signaling, were detected by western blotting. The observations showed that LSP1 was highly augmented in glioblastoma samples. Additionally, up-regulation of LSP1 was associated with a unfavorable prognosis in glioblastoma patients. Biological experiments revealed that depletion of LSP1 significantly suppressed the proliferation, invasion and migration of U251 and A172 cells. MiR-920, as an upstream regulator of LSP1, negatively modulated LSP1 expression and promoted U251 cells malignant behaviors after miR-920 inhibitor treatment. However, together knockdown LSP1 and miR-920 inhibited these effects. Moreover, the expression levels of p-JAK2 and p-STAT5 were increased or decreased in U251 cells after transfection of miR-920 inhibitor or si-LPS1. Taken together, miR-920 might blocked the malignant development of glioblastoma cells, which is possibly realized by targeting LSP1 and modulation of JAK/STAT5 pathway. These findings implied that miR-920/LSP1 was a potential therapeutic target for glioblastoma treatment.

NOTCH pathway activation in infantile hemangiomas

OBJECTIVE

The objective of this study was to characterize the role of NOTCH signaling cascade activation in the angiogenic drive of infantile hemangioma (IH) tissue.

METHODS

Both IH tissue and normal skin were collected from 55 surgical patients. Of these, 14 were proliferating hemangiomas, 14 were stationary, 14 were involuted, and 13 had been treated with propranolol. Protein and RNA were extracted from all tissues and subjected to Western blotting and reverse transcription-polymerase chain reaction, respectively, for components of the NOTCH signaling pathway.

RESULTS

Compared with normal skin from the same patients, proliferating IHs contained higher levels of messenger RNA and protein for the majority of NOTCH receptors and ligands as well as the downstream coactivator MAML1. Expression of NOTCH receptor ligand messenger RNA and protein was significantly lower in involuting and propranolol-treated IHs.

CONCLUSIONS

Perturbations in NOTCH signaling follow the natural course and treatment outcome of IHs, suggesting a critical role in their pathogenesis.

Toosendanin Suppresses Glioma Progression Property and Induces Apoptosis by Regulating miR-608/Notch Axis

Background

Glioma is one the most common and aggressive primary tumors of adult central nervous system worldwide, which tends to develop dysplasia and metastasis. Recently, toosendanin (TSN) has shown pharmacological effects in several cancers. However, little is known about the underlying mechanism of the effect of TSN on glioma and its relationship between miRNA in glioma.

Methods

Cell proliferation, cell cycle, cell apoptosis and cell migration were analyzed by CCK-8 cell viability, flow cytometry, wound scratch healing, transwell and Western blotting assays, respectively, in vitro. The regulation relationships between TSN and miR-608 or between miR-608 and Notch1 (Notch2) were examined using qRT-PCR, dual-luciferase and Western blotting assays. The functional effects of TSN through regulating miR-608 and Notch1 (Notch2) were further examined using a xenograft tumor mouse model in vivo.

Results

After TSN concentration was increased from 50 nM, 100 nM to 150 nM, cell proliferation and cell cycle were gradually reduced, and the cell apoptosis rate was increased in U-138MG or U-251MG cells. Wound-healing and transwell assays results showed that cell migration was significantly inhibited in TSN treatment cells (TSN treatment, 50 nM) compared to control cells. Mechanistic studies revealed that TSN up-regulated the expression of microRNA-608 (miR-608), while down-regulated the expression of miR-608’s target, Notch1 and Notch2. Over-expression of Notch1 and Notch2 partly attenuated TSN-induced tumor suppressive function. Moreover, in vivo experiments revealed that TSN treatment led to a significant inhibition of tumor growth, suggesting that it might be a promising drug for the treatment of glioma.

Conclusion

In the present study, a novel established functional manner of TSN/miR-608/Notch1 (Notch2) axis was systematically indicated, which might provide prospective intervention ways for glioma therapy.

miR-6869-5p Inhibits Glioma Cell Proliferation and Invasion via Targeting PGK1

Accumulating studies have suggested the dysregulated microRNAs (miRNAs) play important roles in brain tumors, including glioma. miR-6869-5p has been documented to be aberrantly expressed in diverse cancers. However, the precise role of miR-6869-5p in glioma remains poorly understood. This study is aimed at evaluating its modifying effects on glioma. Significantly decreased expression of miR-6869-5p was found in glioma tissues and cells. Negative association was documented between miR-6869-5p and PGK1 in glioma cells, and PGK1 was demonstrated to be a targeted gene of this miRNA by luciferase reporter assay. miR-6869-5p regulated glioma cell proliferation and invasion via targeting PGK1. In addition, the survival analysis had suggested that low miR-6869-5p expression predicted poor prognosis of glioma patients. This study has suggested that miR-6869-5p is a useful tumor suppressor and prognostic marker in glioma.

Glioblastoma: Pathogenesis and Current Status of Chemotherapy and Other Novel Treatments

Glioblastoma is one of the most common and detrimental forms of solid brain tumor, with over 10,000 new cases reported every year in the United States. Despite aggressive multimodal treatment approaches, the overall survival period is reported to be less than 15 months after diagnosis. A widely used approach for the treatment of glioblastoma is surgical removal of the tumor, followed by radiotherapy and chemotherapy. While there are several drugs available that are approved by the Food and Drug Administration (FDA), significant efforts have been made in recent years to develop new chemotherapeutic agents for the treatment of glioblastoma. This review describes the molecular targets and pathogenesis as well as the current progress in chemotherapeutic development and other novel therapies in the clinical setting for the treatment of glioblastoma.

Knockdown of TMPRSS3 inhibits cell proliferation, migration/invasion and induces apoptosis of glioma cells

Transmembrane protease serine 3 (TMPRSS3) is a member of type II transmembrane serine proteases (TTSP) family, which play important roles in the development and progression of various cancers. However, the role of TMPRSS3 in glioma remains unclear. In the present study, we evaluated the expression patterns of TMPRSS3 in clinical tumor samples and glioma cell lines. The results showed that TMPRSS3 was highly expressed in both human glioma tissues and cell lines. Knockdown of TMPRSS3 in glioma cells by transfection with small interfering RNA targeting TMPRSS3 (si-TMPRSS3) significantly suppressed cell proliferation and migration/invasion. Moreover, knockdown of TMPRSS3 markedly elevated the apoptotic rate of glioma cells. Si-TMPRSS3 transfection also resulted in a remarkable increase in bax expression and a notable decrease in bcl-2 expression in glioma cells. Furthermore, TMPRSS3 knockdown markedly suppressed the expressions of Notch1 and Hes1. The results indicated that knockdown of TMPRSS3 exhibited antiglioma effect, which is associated with the inactivation of the Notch signaling pathway. These findings suggested that TMPRSS3 might be used as a therapeutic target for glioma treatment.

Inhibition of microRNA-34a Suppresses Epileptiform Discharges Through Regulating Notch Signaling and Apoptosis in Cultured Hippocampal Neurons

Epilepsy is characterized by recurrent unprovoked seizures and some seizures can cause neuronal apoptosis, which is possible to make contributions to the epilepsy phenotype, impairments in cognitive function or even epileptogenesis. Moreover, many studies have indicated that microRNA-34a (miRNA-34a) is involved in apoptosis through regulating Notch signaling. However, whether miRNA-34a participates in neuronal apoptosis after seizures remain unclear. Therefore, we aimed to explore the expression of miRNA-34a and its effects on the epileptiform discharge in spontaneous recurrent epileptiform discharges (SREDs) rat hippocampal neuronal pattern. Mg²⁺-free medium was used to induce SREDs, quantitative reverse-transcription polymerase chain reaction was used to detect the expression of miRNA-34a, western blot was used to determine the expression of Notch pathway and apoptosis-related proteins, and whole cell current clamp recordings was used to observe the alteration of epileptiform discharge. We found obvious apoptosis, increased expression of miRNA-34a and decreased expression of Notch signaling in Mg²⁺-free-treated neurons. Treatment with miRNA-34a inhibitor decreased the frequency of action potentials, activated Notch signaling and prevented neuronal apoptosis in Mg²⁺-free-treated neurons. However, treatment with miRNA-34a mimics increased the frequency of action potentials, down-regulated Notch signaling and promoted neuronal apoptosis in Mg²⁺-free-treated neurons. Furthermore, γ-secretase inhibitor N-[N-(3,5-di-uorophenacetyl)-1-alanyl]-S-phenylglycine t-butylester (DAPT), an inhibitor of Notch signaling, could weaken anti-apoptosis effect of miRNA-34a inhibitor. These results suggest that inhibition of miRNA-34a could suppress epileptiform discharges through regulating Notch signaling and apoptosis in the rat hippocampal neuronal model of SREDs.

Dynamic expression of 11 miRNAs in 83 consecutive primary and corresponding recurrent glioblastoma: correlation to treatment, time to recurrence, overall survival and MGMT methylation status

Background

Glioblastoma (GBM) is the most common and the most malignant glioma subtype. Among numerous genetic alterations, miRNAs contribute to pathogenesis of GBM and it is suggested that also to GBM recurrence and resistance to therapy. Based on publications, we have selected 11 miRNAs and analyzed their expression in GBM. We hypothesized that selected miRNAs are differentially expressed and involved in primary as well as in recurrent GBM, that show significant expressional differences when different treatment options are in question, and that are related to certain patients and tumor characteristics.

Patients and methods

Paraffin embedded tissues, obtained from primary and corresponding recurrent tumor from 83 patients with primary GBM were used. Eleven miRNAs (miR-7, miR-9, miR-15b, miR-21, miR-26b, miR-124a, miR-199a, let-7a, let-7b, let-7d, and let-7f) were selected for qPCR expression analysis. For patients who received temozolamide (TMZ) as chemotherapeutic drug, O6-methylguanine-DNA methyltransferase (MGMT) methylation status was defined using the methyl-specific PCR.

Results

There was a significant change in expression of miR-7, miR-9, miR-21, miR-26b, mirR-124a, miR-199a and let-7f in recurrent tumor compared to the primary. In recurrent tumor, miR-15b, let-7d and let-7f significantly changed comparing both treatment options. We also observed difference in progression free survival between patients that received radiotherapy and patients that received radiotherapy and chemotherapy, and longer survival for patients who received chemotherapy after second surgery compared to not treated patients. miR-26b showed correlation to progression free survival and let-7f to overall survival. We did not find any expression difference between the tumors with and without methylated MGMT.

Conclusions

Our data suggest that analyzed miRNAs may not only contribute to pathogenesis of primary GBM, but also to tumor progression and its recurrence. Moreover, expression of certain miRNAs appears to be therapy-dependent and as such they might serve as additional biomarker for recurrence prediction and potentially predict a therapy-resistance.