SNAP reverses temozolomide resistance in human glioblastoma multiforme cells through down-regulation of MGMT

Nitric Oxide Prevents Glioblastoma Stem Cells' Expansion and Induces Temozolomide Sensitization

Glioblastoma multiforme (GBM) has high mortality and recurrence rates. Malignancy resilience is ascribed to Glioblastoma Stem Cells (GSCs), which are resistant to Temozolomide (TMZ), the gold standard for GBM post-surgical treatment. However, Nitric Oxide (NO) has demonstrated anti-cancer efficacy in GBM cells, but its potential impact on GSCs remains unexplored. Accordingly, we investigated the effects of NO, both alone and in combination with TMZ, on patient-derived GSCs. Experimentally selected concentrations of diethylenetriamine/NO adduct and TMZ were used through a time course up to 21 days of treatment, to evaluate GSC proliferation and death, functional recovery, and apoptosis. Immunofluorescence and Western blot analyses revealed treatment-induced effects in cell cycle and DNA damage occurrence and repair. Our results showed that NO impairs self-renewal, disrupts cell-cycle progression, and expands the quiescent cells' population. Consistently, NO triggered a significant but tolerated level of DNA damage, but not apoptosis. Interestingly, NO/TMZ cotreatment further inhibited cell cycle progression, augmented G0 cells, induced cell death, but also enhanced DNA damage repair activity. These findings suggest that, although NO administration does not eliminate GSCs, it stunts their proliferation, and makes cells susceptible to TMZ. The resulting cytostatic effect may potentially allow long-term control over the GSCs' subpopulation.

Antiproliferative and apoptotic effects of telmisartan in human glioma cells

Glioblastoma is the most common primary central nervous system tumor in adults. Angiotensin II receptor blockers (ARBs) are broadly applied to treat hypertension. Moreover, research has revealed that ARBs have the capacity to suppress the growth of several cancer types. In this study, we assessed the effects of three ARBs with the ability to cross the blood brain barrier (telmisartan, valsartan and fimasartan) on cell proliferation in three glioblastoma multiforme (GBM) cell lines. Telmisartan markedly suppressed the proliferation, migration, and invasion of these three GBM cell lines. Microarray data analysis revealed that telmisartan regulates DNA replication, mismatch repair, and the cell cycle pathway in GBM cells. Furthermore, telmisartan induced G0/G1 phase arrest and apoptosis. The bioinformatic analysis and western blotting results provide evidence that SOX9 is a downstream target of telmisartan. Telmisartan also suppressed tumor growth in vivo in an orthotopic transplant mouse model. Therefore, telmisartan is a potential treatment for human GBM.

Momordicine I suppresses glioma growth by promoting apoptosis and impairing mitochondrial oxidative phosphorylation

Glioblastoma (GBM) is the most common type of primary brain tumor. Patients with GBM have poor survival outcomes. Isolated components of Momordica charantia have anticancer effects. However, the bioactivity of M. charantia extracts against GBM remains unknown. We tested four major extracts of M. charantia and found that momordicine I reduced glioma cell viability without serious cytotoxic effects on astrocytes. Momordicine I suppressed glioma cell colony formation, proliferation, migration, and invasion. Momordicine I also induced apoptosis, intracellular reactive oxygen species (ROS) production, and senescence in glioma cells. Moreover, momordicine I decreased the oxidative phosphorylation capacity of glioma cells and inhibited tumor sphere formation in temozolomide (TMZ)-resistant GBM cells. We further explored whether the antiglioma effect of momordicine I may be related to cell cycle modulation and DLGPA5 expression. Our results indicate that the cytotoxic effect of momordicine I on glioma cells suggests its potential therapeutic application to GBM treatment. See also Figure 1(Fig. 1).

The dual role of DNA repair protein MGMT in cancer prevention and treatment

Alkylating agents are genotoxic chemicals that can induce and treat various types of cancer. This occurs through covalent bonding with cellular macromolecules, in particular DNA, leading to the loss of functional integrity under the persistence of modifications upon replication. O⁶-alkylguanine (O⁶-AlkylG) adducts are proposed to be the most potent DNA lesions induced by alkylating agents. If not repaired correctly, these adducts can result, at the molecular level, in DNA point mutations, chromosome aberrations, recombination, crosslinking, and single- and double-strand breaks (SSB/DSBs). At the cellular level, these lesions can result in malignant transformation, senescence, or cell death. O⁶-methylguanine-DNA methyltransferase (MGMT) is a DNA repair protein capable of removing the alkyl groups from O⁶-AlkylG adducts in a damage reversal process that can prevent the adverse biological effects of DNA damage caused by guanine O⁶-alkylation. MGMT can thereby defend normal cells against tumor initiation, however it can also protect tumor cells against the beneficial effects of chemotherapy. Hence, MGMT can play an important role in both the prevention and treatment of cancer; thus, it can be considered as a double-edged sword. From a clinical perspective, MGMT is a therapeutic target, and it is important to explore the rational development of its clinical exploitation.

Progress in research and development of temozolomide brain-targeted preparations: a review

Gliomas are a heterogeneous group of brain tumours with high malignancy, for which surgical resection remains the mainstay of treatment at present. However, the overall prognosis of gliomas remains poor because of their aggressiveness and high recurrence. Temozolomide (TMZ) has anti-proliferative and cytotoxic effects and is indicated for glioblastoma multiforme and recurrent mesenchymal astrocytoma. However, TMZ is disadvantaged by low efficacy and drug resistance, and therefore it is necessary to enhance the brain drug concentration of TMZ to improve its effectiveness and reduce the toxic and adverse effects from systemic administration. There have been many nano-formulations developed for the delivery of TMZ to gliomas that overcome the limitations of TMZ penetration to tumours and increase brain targeting. In this paper, we review the research progress of TMZ nano-formulations, and also discuss challenges and opportunities in the research and development of drug delivery systems, hoping that the data and information summarised herein could provide assistance for the clinical treatment of gliomas.

Historical Perspectives of the Role of NO/NO Donors in Anti-Tumor Activities: Acknowledging Dr. Keefer's Pioneering Research

The role of nitric oxide (NO) in cancer has been a continuous challenge and particularly the contradictory findings in the literature reporting NO with either anti-cancer properties or pro-cancer properties. This dilemma was largely resolved by the level of NO/inducible nitric oxide synthase in the tumor environment as well as other cancer-associated gene activations in different cancers. The initial findings on the role of NO as an anti-cancer agent was initiated in the late 1990's in Dr. Larry Keefer's laboratory, who had been studying and synthesizing many compounds with releasing NO under different conditions. Using an experimental model with selected NO compounds they demonstrated for the first time that NO can inhibit tumor cell proliferation and sensitizes drug-resistant cancer cells to chemotherapy-induced cytotoxicity. This initial finding was the backbone and the foundation of subsequent reports by the Keefer's laboratory and followed by many others to date on NO-mediated anti-cancer activities and the clinical translation of NO donors in cancer therapy. Our laboratory initiated studies on NO-mediated anti-cancer therapy and chemo-immuno-sensitization following Keefer's findings and used one of his synthesized NO donors, namely, (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETANONOate), throughout most of our studies. Many of Keefer's collaborators and other investigators have reported on the selected compound, O2-(2,4-dinitrophenyl) 1-[(4-ethoxycarbonyl)piperazin-1-yl] diazen-1-ium-1,2-diolate (JS-K), and its therapeutic role in many tumor model systems. Several lines of evidence that investigated the treatment with NO donors in various cancer models revealed that a large number of gene products are modulated by NO, thus emphasizing the pleiotropic effects of NO on cancers and the identification of many targets of therapeutic significance. The present review reports historically of several examples reported in the literature that emanated on NO-mediated anti-cancer activities by the Keefer's laboratory and his collaborators and other investigators including my laboratory at the University of California at Los Angeles.

The Effect of Disulfiram and Copper on Cellular Viability, ER Stress and ALDH Expression of Human Meningioma Cells

(1) Background: Meningiomas are the most common intracranial tumors in adults; currently there is no effective chemotherapy for malignant meningiomas. The effect of disulfiram (DSF)/Copper (Cu) on meningiomas remains unclear; (2) Methods: The impact of DSF/Cu on cell viability of meningioma adhesion cells (MgACs) and sphere cells (MgSCs) was assessed via MTS assay. The effects of DSF/Cu on intracellular Cu levels, cell senescence, and apoptosis were analyzed using CopperGreen, C12FDG, and Annexin V assays. Intracellular ALDH isoform expression and canonical pathway expression after DSF/Cu treatment were analyzed using mRNA microarray and Ingenuity Pathway Analysis, with further verification through qRT-PCR and immunoblotting; (3) Results: The viability of MgACs and MgSCs were inhibited by DSF/Cu. DSF/Cu increased intracellular Cu levels and cellular senescence. DSF/Cu also induced ER stress in MgACs and activated the PERK/eIF2 pathway for further adaptive response, apoptosis, and autophagy. Finally, DSF/Cu inhibited the expression of different ALDH isoforms in MgACs and MgSCs; (4) Conclusions: DSF/Cu exerts cytotoxic effects against both meningioma cells and stem-like cells and has treatment potential for meningioma.

A Tumor Suppressor Gene, N-myc Downstream-Regulated Gene 1 (NDRG1), in Gliomas and Glioblastomas

The development of potent and selective therapeutic approaches to glioblastoma (GBM) requires the identification of molecular pathways that critically regulate the survival and proliferation of GBM. Glioblastoma stem-like cells (GSCs) possess stem-cell-like properties, self-renewal, and differentiation into multiple neural cell lineages. From a clinical point of view, GSCs have been reported to resist radiation and chemotherapy. GSCs are influenced by the microenvironment, especially the hypoxic condition. N-myc downstream-regulated gene 1 (NDRG1) is a tumor suppressor with the potential to suppress the proliferation, invasion, and migration of cancer cells. Previous studies have reported that deregulated expression of NDRG1 affects tumor growth and clinical outcomes of patients with GBM. This literature review aimed to clarify the critical role of NDRG1 in tumorigenesis and acquirement of resistance for anti-GBM therapies, further to discussing the possibility and efficacy of NDRG1 as a novel target of treatment for GBM. The present review was conducted by searching the PubMed and Scopus databases. The search was conducted in February 2022. We review current knowledge on the regulation and signaling of NDRG1 in neuro-oncology. Finally, the role of NDRG1 in GBM and potential clinical applications are discussed.

The link between menin and pleiotrophin in the tumor biology of pancreatic neuroendocrine neoplasms

MEN1, which encodes menin protein, is the most frequently mutated gene in pancreatic neuroendocrine neoplasms (pNEN). Pleiotrophin (PTN) was reported being a downstream factor of menin and to promote metastasis in different tumor entities. In this study, the effect of menin and its link to PTN were assessed on features of pNEN cells and outcome of pNEN patients. The expression of menin and PTN in pNEN patient tissues were examined by qRT-PCR and western blot and compared to their metastasis status. Functional assays, including transwell migration/invasion and scratch wound healing assays, were performed on specifically designed CRISPR/Cas9-mediated MEN1-knockout (MEN1-KO) pNEN cell lines (BON1^MEN1-KO and QGP1^MEN1-KO ) to study the metastasis of pNEN. Among 30 menin negative pNEN patients, 21 revealed a strong protein expression of PTN. This combination was associated with metastasis and shorter disease-free survival. Accordingly, in BON1^MEN1-KO and QGP1^MEN1-KO cells, PTN protein expression was positively associated with enhanced cell migration and invasion, which could be reversed by PTN silencing. PTN is a predicting factor of metastatic behavior of menin-deficient-pNEN. In vitro, menin is able to both promote and suppress the metastasis of pNEN by regulating PTN expression depending on the tumoral origin of pNEN cells.

TMEM2 Combined with IDH and 1p19q in Refining Molecular Subtypes for Predicting Survival of Patients with Glioma

Gliomas are common intracranial tumors with high morbidity and mortality in adults. Transmembrane protein 2 (TMEM2) is involved in the malignant behavior of solid tumors. TMEM2 regulates cell adhesion and metastasis as well as intercellular communication by degrading nonprotein components of the extracellular matrix. This study aimed to evaluate the relationship between TMEM2 expression levels and glioma subtypes or patient prognosis. Our findings revealed that TMEM2 expression was abnormally upregulated in high-grade glioma. Moreover, combining TMEM2, the status of isocitrate dehydrogenase (IDH) and 1p19q, we subdivided molecular subtypes with significant differences in survival. Patients in the MT-codel-low subgroup had better prognosis than those in the WT-no-codel-high subgroup, who fared the worst. Additionally, correlation analysis of TMEM2 and immune cell infiltration indicated an altered tumor microenvironment (TME) and cell redistribution in the TMEM2 high-expression subtype. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that focal adhesion and PI3K-Akt signaling pathways were enriched in the TMEM2-expressing group. In conclusion, aberrant TMEM2 expression can be used as an independent prognostic marker for refining glioma molecular subtyping and accurate prognosis. These findings will improve rational decision making to provide individualized therapy for patients with glioma.

Diosmin Inhibits Glioblastoma Growth through Inhibition of Autophagic Flux

Diosmin, a natural flavone glycoside acquired through dehydrogenation of the analogous flavanone glycoside hesperidin, is plentiful in many citrus fruits. Glioblastoma multiforme (GBM) is the most malignant primary brain tumor; the average survival time of GBM patients is less than 18 months after standard treatment. The present study demonstrated that diosmin, which is able to cross the blood-brain barrier, inhibited GBM cell growth in vitro and in vivo. Diosmin also impeded migration and invasion by GBM8401and LN229 GBM cells by suppressing epithelial-mesenchymal transition, as indicated by increased expression of E-cadherin and decreased expression of Snail and Twist. Diosmin also suppressed autophagic flux, as indicated by increased expression of LC3-II and p62, and induced cell cycle arrest at G1 phase. Importantly, diosmin did not exert serious cytotoxic effects toward control SVG-p12 astrocytes, though it did reduce astrocyte viability at high concentrations. These findings provide potentially helpful support to the development of new therapies for the treatment of GBM.

The implications of nitric oxide metabolism in the treatment of glial tumors

Glial tumors are the most common intracranial malignancies. Unfortunately, despite such a high prevalence, patients' prognosis is usually poor. It is related to the high invasiveness, tendency to relapse and the resistance of tumors to traditional methods of treatment. An important link in the aspect of these issues may be nitric oxide (NO) metabolism. It is a very complex mechanism with multidirectional effects on the neoplastic process. Depending on the concentration axis, it can both exert pro-tumor action as well as contribute to the inhibition of tumorigenesis. The latest observations show that the control of its metabolism can be very helpful in the development of new methods of treating gliomas, as well as in increasing the effectiveness of the agents currently used. The influence of nitric oxide and nitric oxide synthase (NOS) activity on glioma stem cells seem to be of particular importance. The use of specific inhibitors may allow the reduction of tumor growth and its tendency to relapse. Another important feature of GSCs is their conditioning of glioma resistance to traditional forms of treatment. Recent studies have shown that modulation of NO metabolism can suppress this effect, preventing the induction of radio and chemoresistance. Moreover, nitric oxide is involved in the regulation of a number of immune mechanisms. Adequate modulation of its metabolism may contribute to the induction of an anti-tumor response in the patients' immune system.

Knockdown lncRNA CRNDE enhances temozolomide chemosensitivity by regulating autophagy in glioblastoma

Background

The regulatory roles of long non-coding RNA (lncRNA) CRNDE in temozolomide (TMZ) chemoresistance to glioblastoma multiforme (GBM) are still poorly understood. Therefore, the function, characteristics, and possible mechanism of CRNDE in TMZ-induced chemoresistance to GBM were explored.

Methods

Firstly, the expression level of CRNDE in 58 cases of glioma tissue specimens and 30 cases of normal brain tissues were tested by qRT-PCR. Meanwhile, the correlation between CRNDE expression level, the clinicopathological characteristics, and survival time of patients with glioma were analyzed. Then, the CRNDE expression in various glioma cell lines was detected, and CRNDE knockdown cell models were constructed. Subsequently, to explore the effect of CRNDE on chemosensitivity to TMZ, cell viability was detected by the CCK-8 assay and IC₅₀ values, and cell proliferation was detected by cell clone assay and EdU assay, as well as cell survival was detected by apoptosis with flow cytometry under TMZ treatment. Further, the expression of drug-resistance protein ABCG2, autophagy related proteins, and PI3K/Akt/mTOR pathway were measured by western blot or qRT-PCR in TMZ-treated glioma cells. Finally, the mouse tumor xenograft model was established and the tumor volume and weight were measured, and ABCG2 expression was conducted by immunohistochemistry assay.

Results

The integrated results demonstrated lncRNA CRNDE was a poor prognosis factor for GBM patient, which was upregulated in patients who were resistant to TMZ, and closely associated with chemotherapeutic response status to TMZ treatment. Further, functional assays revealed that knockdown of CRNDE could notably reduce glioma cell viability and proliferation, and elevate cell apoptosis to enhance the chemosensitivity to TMZ in vitro and in vivo. Mechanistically, the depression of CRNDE could diminish the expression of LC3 II/I, Beclin1 and Atg5 and increase the p62 expression level to inhibit autophagy due to the activation of PI3K/Akt/mTOR pathway as well as highly correlated with ABCG2 expression.

Conclusions

Overall, the study provided that lncRNA CRNDE is a reliable clinical predictor of outcome and prognosis and a potential biomarker for predicting TMZ treatment response in GBM by modulating the autophagy through PI3K/Akt/mTOR pathway and ABCG2 expression which may be a novel therapeutic target for regulating TMZ sensitivity to GBM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02153-x.

Elucidating the mechanisms of Temozolomide resistance in gliomas and the strategies to overcome the resistance

Temozolomide (TMZ) is a first-choice alkylating agent inducted as a gold standard therapy for glioblastoma multiforme (GBM) and astrocytoma. A majority of patients do not respond to TMZ during the course of their treatment. Activation of DNA repair pathways is the principal mechanism for this phenomenon that detaches TMZ-induced O-6-methylguanine adducts and restores genomic integrity. Current understanding in the domain of oncology adds several other novel mechanisms of resistance such as the involvement of miRNAs, drug efflux transporters, gap junction's activity, the advent of glioma stem cells as well as upregulation of cell survival autophagy. This review describes a multifaceted account of different mechanisms responsible for the intrinsic and acquired TMZ-resistance. Here, we summarize different strategies that intensify the TMZ effect such as MGMT inhibition, development of novel imidazotetrazine analog, and combination therapy; with an aim to incorporate a successful treatment and increased overall survival in GBM patients.

The Anti-Cancer Effect of Four Curcumin Analogues on Human Glioma Cells

Purpose

Glioblastoma multiforme (GBM) is the primary aggressive malignancy of the brain with poor outcome. Curcumin analogues are polyphenolic compounds as the bioactive substances extracted from turmeric. This study aims to investigate the anti-cancer effects of four curcumin analogues. Furthermore, the molecular mechanisms of dimethoxycurcumin in human gliomas were analyzed by Western blot.

Materials and Methods

Human LN229 and GBM8401 glioma cells were treated by four curcumin analogues with different number of methoxy groups. The cell viability, cell cycle, apoptosis, proliferation and ROS production of human gliomas were analyzed by flow cytometry. Moreover, the effects of four curcumin analogues on tumorigenesis of gliomas were conducted by wound healing assay and colony formation assay. Furthermore, the molecular mechanisms of dimethoxycurcumin in human gliomas were analyzed by Western blot.

Results

Our data showed that four different curcumin analogues including curcumin, bisdemethoxycurcumin, demethoxycurcumin, and dimethoxycurcumin promote sub-G1 phase, G2/M arrest, apoptosis, and ROS production in human glioma cells. Moreover, dimethoxycurcumin suppressed cell viability, migration, and colony formation, induction of sub-G1, G2/M arrest, apoptosis, and ROS production in glioma cells. Moreover, the mechanism of dimethoxycurcumin is ROS production to increase LC3B-II expression to induce autophagy. Furthermore, dimethoxycurcumin suppressed apoptotic marker, BCL-2 to promote apoptosis in LN229 and GBM8401 glioma cells.

Conclusion

Our study found that dimethoxycurcumin induced apoptosis, autophagy, ROS production and suppressed cell viability in human gliomas. Dimethoxycurcumin might be a potential therapeutic candidate in human glioma cells.

Knock-Down of Mucolipin 1 Channel Promotes Tumor Progression and Invasion in Human Glioblastoma Cell Lines

Among cancers that affect the central nervous system, glioblastoma is the most common. Given the negative prognostic significance of transient receptor potential mucolipin 1 (TRPML1) channel reduction in patients with glioblastoma, as discussed in previous publications, the aim of the current study was to investigate the biological advantage of TRPML1 loss for glioma cells. Human glioblastoma primary cancer cells (FSL and FCL) and glioblastoma cell lines (T98 and U251) were used for that purpose. TRPML1 silencing in T98 cells induces defective autophagy, nitric oxide (NO) production, and cathepsin B-dependent apoptosis in the first 48 h and then apoptotic-resistant cells proliferate with a high growth rate with respect to control cells. In U251 cells, knock-down of TRPML1 stimulates NO generation and protein oxidation, arrests cell cycle at G2/M phase, and induces autophagy leading to cathepsin B-dependent senescence. Finally, in both cell lines, the long-term effects of TRPML1 silencing promote survival and invasion capacity with respect to control cells. Silencing of TRPML1 also affects the phenotype of glioblastoma primary cells. FSL cells show increased proliferation ability, while FCL cells enter into senescence associated with an increased invasion ability. In conclusion, although the molecular heterogeneity among different glioblastoma cell lines mirrors the intercellular heterogeneity in cancer cells, our data support TRPML1 downregulation as a negative prognostic factor in glioblastoma.

Glioblastoma stem cell (GSC)-derived PD-L1-containing exosomes activates AMPK/ULK1 pathway mediated autophagy to increase temozolomide-resistance in glioblastoma

Temozolomide (TMZ)-resistance hampers the therapeutic efficacy of this drug for glioblastoma (GBM) treatment in clinic, and emerging evidences suggested that exosomes from GBM-derived stem cells (GSCs) contributed to this process, but the detailed mechanisms are still largely unknown. In the present study, we reported that GSCs derived programmed death-ligand 1 (PD-L1) containing exosomes activated AMPK/ULK1 pathway mediated protective autophagy enhanced TMZ-resistance in GBM in vitro and in vivo. Specifically, we noticed that continuous low-dose TMZ stimulation promoted GSCs generation and PD-L1 containing exosomes (PD-L1-ex) secretion in GBM cells, and that PD-L1-ex inhibited cell apoptosis and promoted cell autophagy to increased TMZ-resistance in GBM cells, which were reversed by co-treating cells with the autophagy inhibitor 3-methyladenine (3-MA). Consistently, upregulation of PD-L1 also increased TMZ-resistance in TS-GBM cells, and silencing of PD-L1 sensitized TR-GBM cells to TMZ. In addition, PD-L1-ex activated AMPK/ULK1 pathway to induce autophagy in TMZ treated GBM cells, and the inhibitors for AMPK (compound C) and ULK1 (SBI-0206965) promoted cell apoptosis in GBM cells co-treated with PD-L1-ex and high-dose TMZ. Finally, we evidenced that PD-L1-ex promoted tumor growth and Ki67 protein expressions to increase TMZ-resistance in GBM in vivo. Collectively, we concluded that GSCs-derived PD-L1-ex activated AMPK1/ULK1 signaling cascade mediated autophagy to increase TMZ-resistance in GBM, and this study provided potential strategies to improve the therapeutic efficacy of TMZ in GBM.

Valproic Acid Enhanced Apoptosis by Promoting Autophagy Via Akt/mTOR Signaling in Glioma

Glioma is the most common malignant tumor in the central nervous system with a poor median survival. Valproic acid (VPA), a widely used antiepileptic drug, has been found to have antitumor effects on gliomas, but its role still has not been determined. In this study, we investigated VPA-induced apoptotic and autophagic effects on human U251 and SNB19 cells by cell counting kit-8 assay, flow cytometry, terminal deoxynucleotidyl transferase-mediated nick end labeling staining, western blots, and immunofluorescence assay in vitro, and then we further explored the role of autophagy in apoptosis by using the selective antagonist MHY1485. The data showed that VPA inhibited U251 and SNB19 glioma cells viability in a dose-dependent and time-dependent manner and induced apoptosis through the mitochondria-dependent pathway in vitro. In addition, VPA activated the Akt/mTOR pathway by decreasing their protein phosphorylation to promote cellular apoptosis. Surprisingly, the mTOR agonist MHY1485, causing a strong elevation of mTOR activity, partially reduced apoptosis ratio, which supposing that the autophagy of VPA is involved in the regulation of apoptosis. These findings suggest that VPA enhanced apoptosis by promoting autophagy via Akt/mTOR signaling in glioma, which could be further evaluated as a reliable therapy for glioma.

Disentangling the therapeutic tactics in GBM: From bench to bedside and beyond

Glioblastoma multiforme (GBM) is one of the most common and malignant form of adult brain tumor with a high mortality rate and dismal prognosis. The present standard treatment comprising surgical resection followed by radiation and chemotherapy using temozolomide can broaden patient's survival to some extent. However, the advantages are not palliative due to the development of resistance to the drug and tumor recurrence following the multimodal treatment approaches due to both intra- and intertumoral heterogeneity of GBM. One of the major contributors to temozolomide resistance is O⁶ -methylguanine-DNA methyltransferase. Furthermore, deficiency of mismatch repair, base excision repair, and cytoprotective autophagy adds to temozolomide obstruction. Rising proof additionally showed that a small population of cells displaying certain stem cell markers, known as glioma stem cells, adds on to the resistance and tumor progression. Collectively, these findings necessitate the discovery of novel therapeutic avenues for treating glioblastoma. As of late, after understanding the pathophysiology and biology of GBM, some novel therapeutic discoveries, such as drug repurposing, targeted molecules, immunotherapies, antimitotic therapies, and microRNAs, have been developed as new potential treatments for glioblastoma. To help illustrate, "what are the mechanisms of resistance to temozolomide" and "what kind of alternative therapeutics can be suggested" with this fatal disease, a detailed history of these has been discussed in this review article, all with a hope to develop an effective treatment strategy for GBM.

Tunneling Nanotubes Mediate Adaptation of Glioblastoma Cells to Temozolomide and Ionizing Radiation Treatment

Glioblastoma (GBM) is the most prevalent and aggressive tumor in the central nervous system. Surgical resection followed by concurrent radiotherapy (ionizing radiation [IR]) and temozolomide (TMZ) is the standard of care for GBM. However, a large subset of patients offer resistance or become adapted to TMZ due mainly to the DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT). Thus, alternative mechanisms of MGMT deregulation have been proposed but are heretofore unproven. We show that heterogeneous GBM cells express tunneling nanotubes (TNTs) upon oxidative stress and TMZ/IR treatment. We identified that MGMT protein diffused from resistant to sensitive cells upon exposure to TMZ/IR, resulting in protection against cytotoxic therapy in a TNT-dependent manner. In vivo analysis of resected GBM tumors support our hypothesis that the MGMT protein, but not its mRNA, was associated with TNT biomarkers. We propose that targeting TNT formation could be an innovative strategy to overcome treatment resistance in GBM.

Biological Characterization and Therapeutics for Subscalp Recurrent in Intracranial Glioblastoma

Purpose

Gliomas are common intracranial tumors, of which 70% are malignant gliomas. Glioblastoma multiforme (GBM) is the most aggressive tumor, and patients with GBM have a median survival time of only 9–12 months; extracranial recurrence of GBM is very rare. A therapeutic strategy for this kind of recurrent tumor is lacking.

Materials and Methods

We present a case of a patient with extracranial recurrence of subscalp GBM. The subscalp tumor was resected and xenotransplanted into BALB/C nude mice. Then, glioma cells were isolated from the xenograft models and passaged in vitro. HE staining, immunohistochemistry, CCK-8 assays, karyotypic analysis, short tandem repeat STR analysis and flow cytometry were used to analyze the biological characteristics and malignant phenotype of these established cells. The cells and xenografts were then used as preclinical models to evaluate the antitumor efficacy of oncolytic herpes simplex virus 1 (oHSV-1).

Results

The isolated cells, which were named BT-01, were positive for Nestin and GFAP. The main characteristics of BT-01 cells were that they harbored glioblastoma stem-like cells (GSCs) and that they possessed highly aggressive migration capacities compared with the existing cell lines U87-MG and U251-MG. Moreover, BT-01 cells tolerated the chemotherapeutic drug temozolomide. Our study showed that oHSV-1 could replicate in and repress the growth of BT-01 cells and significantly inhibit tumor growth in xenograft models.

Conclusion

Taken together, our results showed that a new recurrent glioblastoma cell line was established, which can be useful for research on recurrent glioblastoma. We provided a reliable preclinical model to evaluate the antitumor efficacy of oHSV-1 in vivo and a promising therapy for recurrent GBM.

Analyzing the lncRNA, miRNA, and mRNA-associated ceRNA networks to reveal potential prognostic biomarkers for glioblastoma multiforme

Background

Glioblastoma multiforme (GBM) is the most seriously brain tumor with extremely poor prognosis. Recent research has demonstrated that competitive endogenous RNA (ceRNA) network which long noncoding RNAs (lncRNAs) act as microRNA (miRNA) sponges to regulate mRNA expression were closely related to tumor development. However, the regulatory mechanisms and functional roles of ceRNA network in the pathogenesis of GBM are remaining poorly understood.

Methods

In this study, we systematically analyzed the expression profiles of lncRNA and mRNA (GSE51146 dataset) and miRNA (GSE65626 dataset) from GEO database. Then, we constructed a ceRNA network with the dysregulated genes by bioinformatics methods. The TCGA and GSE4290 dataset were used to confirm the expression and prognostic value of candidate mRNAs.

Results

In total, 3413 differentially expressed lncRNAs and mRNAs, 305 differentially expressed miRNAs were indentified in GBM samples. Then a ceRNA network containing 3 lncRNAs, 5 miRNAs, and 60 mRNAs was constructed. The overall survival analysis of TCGA databases indicated that two mRNAs (C1s and HSD3B7) were remarkly related with the prognosis of GBM.

Conclusion

The ceRNA network may increase our understanding to the pathogenesis of GBM. In general, the candidate mRNAs from the ceRNA network can be predicted as new therapeutic targets and prognostic biomarkers for GBM.