Recycling drug screen repurposes hydroxyurea as a sensitizer of glioblastomas to temozolomide targeting de novo DNA synthesis, irrespective of molecular subtype

Ulipristal-temozolomide-hydroxyurea combination for glioblastoma: in-vitro studies

BACKGROUND

Glioblastoma multiforme (GBM) is a brain malignancy with worst survival. Low dose progesterone stimulates GBM growth, while progesterone receptor (PR)-antagonist mifepristone was shown to reduce growth and to enhance temozolomide sensitivity in GBM cells. Mifepristone is not available in all countries due to ethical reasons and may cause adrenal insufficiency and pelvic infections. Ulipristal is also a PR-antagonist used in treatment of uterine leiomyomas with higher biosafety. Ulipristal is demonstrated to suppress growth of breast cancer, yet it is not tested as yet whether it can also block growth and sensitize to temozolomide in glioblastoma as it was previously shown with mifepristone. Our first aim was to detect whether ulipristal exerts antiproliferative and chemotherapy-sensitizing effects in glioblastoma. Hydroxyurea inhibits DNA replication via blocking ribonucleotide reductase (RR) and it was demonstrated to increase temozolomide antineoplasticity in GBM. Progesterone receptor-activation in the uterus enhances RR transcription. Hence, we have hypothesized that PR-inactivation with ulipristal would further enhance hydroxyurea antineoplasticity by shutting down DNA synthesis mechanisms through further suppression of RR. Lastly, there exists no study as yet whether ulipristal, hydroxyurea and temozolomide could exert ternary antineoplastic efficacy, which was our last aim to define.

METHODS

To reveal interactions between ulipristal, hydroxyurea and temozolomide, we treated human U251 GBM cell line with these agents alone and in combination and measured cell proliferation, total antioxidant capacity (TAC) and total oxidant status (TOS) in conditioned medium and cellular cytokine gene expressions.

RESULTS

All agents significantly reduced cell proliferation significantly, yet the most significant decrease of GBM cells occurred with the triple drug combination at the 96th hour. All agents significantly decreased TAC and increased TOS in culture media, which was mostly relevant for the triple combination at the 96th hour. All these three agents tend to reduce the expression of immunosuppressive and/or GBM-growth stimulating cytokines TGF-β, IL-10 and IL-17 while increasing the expression of GBM-growth suppressing cytokine IL-23.

CONCLUSIONS

Reproposal of these agents in treatment of GBM would be a plausible approach if future studies prove their efficacy.

Biomimetic hypoxia-triggered RNAi nanomedicine for synergistically mediating chemo/radiotherapy of glioblastoma

Although RNA interference (RNAi) therapy has emerged as a potential tool in cancer therapeutics, the application of RNAi to glioblastoma (GBM) remains a hurdle. Herein, to improve the therapeutic effect of RNAi on GBM, a cancer cell membrane (CCM)-disguised hypoxia-triggered RNAi nanomedicine was developed for short interfering RNA (siRNA) delivery to sensitize cells to chemotherapy and radiotherapy. Our synthesized CCM-disguised RNAi nanomedicine showed prolonged blood circulation, high BBB transcytosis and specific accumulation in GBM sites via homotypic recognition. Disruption and effective anti-GBM agents were triggered in the hypoxic region, leading to efficient tumor suppression by using phosphoglycerate kinase 1 (PGK1) silencing to enhance paclitaxel-induced chemotherapy and sensitize hypoxic GBM cells to ionizing radiation. In summary, a biomimetic intelligent RNAi nanomedicine has been developed for siRNA delivery to synergistically mediate a combined chemo/radiotherapy that presents immune-free and hypoxia-triggered properties with high survival rates for orthotopic GBM treatment.

Glioblastoma and the search for non-hypothesis driven combination therapeutics in academia

Glioblastoma (GBM) remains a cancer of high unmet clinical need. Current standard of care for GBM, consisting of maximal surgical resection, followed by ionisation radiation (IR) plus concomitant and adjuvant temozolomide (TMZ), provides less than 15-month survival benefit. Efforts by conventional drug discovery to improve overall survival have failed to overcome challenges presented by inherent tumor heterogeneity, therapeutic resistance attributed to GBM stem cells, and tumor niches supporting self-renewal. In this review we describe the steps academic researchers are taking to address these limitations in high throughput screening programs to identify novel GBM combinatorial targets. We detail how they are implementing more physiologically relevant phenotypic assays which better recapitulate key areas of disease biology coupled with more focussed libraries of small compounds, such as drug repurposing, target discovery, pharmacologically active and novel, more comprehensive anti-cancer target-annotated compound libraries. Herein, we discuss the rationale for current GBM combination trials and the need for more systematic and transparent strategies for identification, validation and prioritisation of combinations that lead to clinical trials. Finally, we make specific recommendations to the preclinical, small compound screening paradigm that could increase the likelihood of identifying tractable, combinatorial, small molecule inhibitors and better drug targets specific to GBM.

Heat shock protein 27 deficiency promotes ferrous ion absorption and enhances acyl-Coenzyme A synthetase long-chain family member 4 stability to promote glioblastoma cell ferroptosis

BACKGROUND

Glioblastoma is one of the malignant tumors of the central nervous system with high lethality, high disability and low survival rate. Effective induction of its death is one of the existing challenges. In recent studies, heat shock protein 27 (HSP27) has been shown to be associated with ferroptosis; therefore, targeting HSP27 may be a potential therapeutic approach for GBM.

METHODS

Immunohistochemistry and western blot analysis were used to detect the expression of HSP27 in GBM tissues. CCK8, plate clone formation assay, EdU proliferation assay for cell proliferation ability, PI, LDH release assay for cell viability. Reactive oxygen, iron levels, and mitochondrial potential for HSP27 silencing were assayed for ferrotosis in vitro. Western blotting and IP were used to verify the relationship between HSP27 and ACSL4. The effect of knockdown of HSP27 on tumor growth capacity was assessed in an intracranial xenograft model.

RESULTS

HSP27 was significantly highly expressed in GBM. In vitro experiments, knockdown of HSP27 significantly induced ferroptosis in GBM cells. IP and western blot demonstrated a sumo-ization link between HSP27 and ACSL4. In vivo experiments, HSP27 deficiency retarded tumor growth rate by promoting ferroptosis.

CONCLUSIONS

HSP27 deficiency promotes GBM ferroptosis. Targeting HSP27 may serve as a new direction for GBM treatment.

Drug Repurposing, a Fast-Track Approach to Develop Effective Treatments for Glioblastoma

Glioblastoma (GBM) remains one of the most difficult tumors to treat. The mean overall survival rate of 15 months and the 5-year survival rate of 5% have not significantly changed for almost 2 decades. Despite progress in understanding the pathophysiology of the disease, no new effective treatments to combine with radiation therapy after surgical tumor debulking have become available since the introduction of temozolomide in 1999. One of the main reasons for this is the scarcity of compounds that cross the blood-brain barrier (BBB) and reach the brain tumor tissue in therapeutically effective concentrations. In this review, we focus on the role of the BBB and its importance in developing brain tumor treatments. Moreover, we discuss drug repurposing, a drug discovery approach to identify potential effective candidates with optimal pharmacokinetic profiles for central nervous system (CNS) penetration and that allows rapid implementation in clinical trials. Additionally, we provide an overview of repurposed candidate drug currently being investigated in GBM at the preclinical and clinical levels. Finally, we highlight the importance of phase 0 trials to confirm tumor drug exposure and we discuss emerging drug delivery technologies as an alternative route to maximize therapeutic efficacy of repurposed candidate drug.

Highly Invasive Fluorescent/Bioluminescent Patient-Derived Orthotopic Model of Glioblastoma in Mice

Development of the novel diagnostic and therapeutic approaches in neuro-oncology requires tumor models that closely reproduce the biological features of patients’ tumors. Patient-derived xenografts (PDXs) are recognized as a valuable and the most “close-to-patient” tool for preclinical studies. However, their establishment is complicated by the factors related to both the surgical material and technique of the orthotopic implantation. The aim of this work was to develop a patient-derived glioblastoma multiform (GBM) model that stably co-expresses luciferase and a far-red fluorescent protein for monitoring of tumor progression in the brain and, using this model, to validate new diagnostic methods—macroscopic fluorescence lifetime imaging (macro-FLIM) and cross-polarization optical coherence tomography (CP OCT). The established model was similar to the original patient’s GBM in terms of histological and immunohistochemical features and possessed reproducible growth in nude mice, which could be observed by both fluorescence and bioluminescence imaging. Our results demonstrated the high potential of macro-FLIM and CP OCT for intraoperative differentiation of GBM from the white matter. Thus, the dual-labeled PDX model of GBM proved to be an excellent approach for observation of tumor development by optical methods.

Antiviral Effect of Polyphenolic Substances in Geranium wilfordii Maxim against HSV-2 Infection Using in vitro and in silico Approaches

Background

Herpes simplex virus type 2 (HSV-2) infestation was the most widespread STD (sexually transmitted diseases) among humans and was the leading cause of infectious recurrent genital herpes. Existing therapies against HSV-2 did incompletely restrain the comeback of activated HSV-2 infestation. Geranium wilfordii Maxim had long been used as traditional Chinese medicine for treating the diseases owing to its anti-inflammatory and antiviral effects. Herein, the study was designed to investigate the antiviral activity of G.wilfordii and its potential effect in regulating the host's immune response.

Methods

To identify the stage of infection at which the compounds inhibited HSV-2, we performed virucidal, therapeutic, and prophylactic assays. The antiviral efficacy was evaluated by the analysis of viral components HSV-2 gD and VP16. The antiviral activities of these compounds were also evaluated by phenotypic analysis, such as cell proliferation and apoptosis. Molecular docking studies on candidate compounds were done to indicate binding interactions between the compounds and adopted compound targets.

Results

Quercetin, corilagin, and geraniin inhibited the replication of HSV-2, with geraniin showing greater TI. The obtained IC₅₀ value of quercetin was 204.7 μM and TI (IC₅₀/EC₅₀) was 5.1, whereas the obtained IC₅₀ value of corilagin was 118.0 μg/ml and TI was 4.05. Geraniin exhibited prominent antiviral activity with an IC₅₀ of 212.4 μM and an EC₅₀ of 18.37 μM, resulting in a therapeutic index (TI) of 11.56. Geraniin showed important in vitro virucidal activity through blocking viral attachment. Compared with the virus group, the apoptosis rates in quercetin-, corilagin-, and geraniin-treated groups were significantly decreased (p < 0.001).The expressions at the transcription genes of virus own replication key factors (including HSV-2 gD and VP16) and cytokines (including TBK1) of infected cells treated with quercetin, corilagin, and geraniin were inhibited. The in silico approaches demonstrated a high number of potential strong intermolecular interactions as hydrogen bonds between geraniin, corilagin, and the activity site of HSV-2 gD. Molecular docking studies demonstrated the effects of corilagin by targeting TBK1.

Conclusions

Together, these results highlighted the importance of G.wilfordii treatment in HSV-2 infection and underscored its therapeutic potential. However, additional in vitro and in vivo research was required to validate our findings.

Transcriptomics-Based Phenotypic Screening Supports Drug Discovery in Human Glioblastoma Cells

Simple Summary

Glioblastoma (GBM) remains a particularly challenging cancer, with an aggressive phenotype and few promising treatment options. Future therapy will rely heavily on diagnosing and targeting aggressive GBM cellular phenotypes, both before and after drug treatment, as part of personalized therapy programs. Here, we use a genome-wide drug-induced gene expression (DIGEX) approach to define the cellular drug response phenotypes associated with two clinical drug candidates, the phosphodiesterase 10A inhibitor Mardepodect and the multi-kinase inhibitor Regorafenib. We identify genes encoding specific drug targets, some of which we validate as effective antiproliferative agents and combination therapies in human GBM cell models, including HMGCoA reductase (HMGCR), salt-inducible kinase 1 (SIK1), bradykinin receptor subtype B2 (BDKRB2), and Janus kinase isoform 2 (JAK2). Individual, personalized treatments will be essential if we are to address and overcome the pharmacological plasticity that GBM exhibits, and DIGEX will play a central role in validating future drugs, diagnostics, and possibly vaccine candidates for this challenging cancer.

Abstract

We have used three established human glioblastoma (GBM) cell lines—U87MG, A172, and T98G—as cellular systems to examine the plasticity of the drug-induced GBM cell phenotype, focusing on two clinical drugs, the phosphodiesterase PDE10A inhibitor Mardepodect and the multi-kinase inhibitor Regorafenib, using genome-wide drug-induced gene expression (DIGEX) to examine the drug response. Both drugs upregulate genes encoding specific growth factors, transcription factors, cellular signaling molecules, and cell surface proteins, while downregulating a broad range of targetable cell cycle and apoptosis-associated genes. A few upregulated genes encode therapeutic targets already addressed by FDA approved drugs, but the majority encode targets for which there are no approved drugs. Amongst the latter, we identify many novel druggable targets that could qualify for chemistry-led drug discovery campaigns. We also observe several highly upregulated transmembrane proteins suitable for combined drug, immunotherapy, and RNA vaccine approaches. DIGEX is a powerful way of visualizing the complex drug response networks emerging during GBM drug treatment, defining a phenotypic landscape which offers many new diagnostic and therapeutic opportunities. Nevertheless, the extreme heterogeneity we observe within drug-treated cells using this technique suggests that effective pan-GBM drug treatment will remain a significant challenge for many years to come.

The Role of the Ubiquitin Proteasome System in Glioma: Analysis Emphasizing the Main Molecular Players and Therapeutic Strategies Identified in Glioblastoma Multiforme

Gliomas constitute the most frequent tumors of the brain. High-grade gliomas are characterized by a poor prognosis caused by a set of attributes making treatment difficult, such as heterogeneity and cell infiltration. Additionally, there is a subgroup of glioma cells with properties similar to those of stem cells responsible for tumor recurrence after treatment. Since proteasomal degradation regulates multiple cellular processes, any mutation causing disturbances in the function or expression of its elements can lead to various disorders such as cancer. Several studies have focused on protein degradation modulation as a mechanism of glioma control. The ubiquitin proteasome system is the main mechanism of cellular proteolysis that regulates different events, intervening in pathological processes with exacerbating or suppressive effects on diseases. This review analyzes the role of proteasomal degradation in gliomas, emphasizing the elements of this system that modulate different cellular mechanisms in tumors and discussing the potential of distinct compounds controlling brain tumorigenesis through the proteasomal pathway.

Mitochondria-targeted hydroxyurea inhibits OXPHOS and induces antiproliferative and immunomodulatory effects

Hydroxyurea (HU), an FDA-approved drug for treating sickle cell disease, is used as an antitumor drug alone and together with conventional chemotherapeutics or radiation therapy. HU is used primarily to treat myeloproliferative diseases because it inhibits the enzyme ribonucleotide reductase involved in DNA synthesis. The hydroxyl group in HU is considered critical for its antiproliferative and chemotherapeutic effects. Here, we substituted the hydroxyl group in HU with a triphenylphosphonium cation attached to an alkyl group with different chain lengths, forming a new class of mitochondria-targeted HU (Mito-HU). Elongating the alkyl side chain length increased the hydrophobicity of Mito-HUs, inhibition of oxidative phosphorylation, and antiproliferative effects in tumor cells. Both mitochondrial complex I- and complex III-induced oxygen consumption decreased with the increasing hydrophobicity of Mito-HUs. The more hydrophobic Mito-HUs also potently inhibited the monocytic myeloid-derived suppressor cells and suppressive neutrophils, and stimulated T cell response, implicating their potential antitumor immunomodulatory mechanism.

An Alternative Pipeline for Glioblastoma Therapeutics: A Systematic Review of Drug Repurposing in Glioblastoma

Simple Summary

Glioblastoma is a devastating malignancy that has continued to prove resistant to a variety of therapeutics. No new systemic therapy has been approved for use against glioblastoma in almost two decades. This observation is particularly disturbing given the amount of money invested in identifying novel therapies for this disease. A relatively rapid and economical pipeline for identification of novel agents is drug repurposing. Here, a comprehensive review detailing the state of drug repurposing in glioblastoma is provided. We reveal details on studies that have examined agents in vitro, in animal models and in patients. While most agents have not progressed beyond the initial stages, several drugs, from a variety of classes, have demonstrated promising results in early phase clinical trials.

Abstract

The treatment of glioblastoma (GBM) remains a significant challenge, with outcome for most pa-tients remaining poor. Although novel therapies have been developed, several obstacles restrict the incentive of drug developers to continue these efforts including the exorbitant cost, high failure rate and relatively small patient population. Repositioning drugs that have well-characterized mechanistic and safety profiles is an attractive alternative for drug development in GBM. In ad-dition, the relative ease with which repurposed agents can be transitioned to the clinic further supports their potential for examination in patients. Here, a systematic analysis of the literature and clinical trials provides a comprehensive review of primary articles and unpublished trials that use repurposed drugs for the treatment of GBM. The findings demonstrate that numerous drug classes that have a range of initial indications have efficacy against preclinical GBM models and that certain agents have shown significant potential for clinical benefit. With examination in randomized, placebo-controlled trials and the targeting of particular GBM subgroups, it is pos-sible that repurposing can be a cost-effective approach to identify agents for use in multimodal anti-GBM strategies.

Mifepristone Repurposing in Treatment of High-Grade Gliomas

Glioma is the most common and aggressive primary tumor of the central nervous system. The standard treatment for malignant gliomas is surgery followed by chemoradiotherapy. Unfortunately, this treatment has not produced an adequate patient response, resulting in a median survival time of 12–15 months and a 5-year overall survival of <5%. Although new strategies have been sought to enhance patient response, no significant increase in the global survival of glioma patients has been achieved. The option of developing new drugs implies a long and costly process, making drug repurposing a more practical alternative for improving glioma treatment. In the last few years, researchers seeking more effective cancer therapy have pursued the possibility of using anti-hormonal agents, such as mifepristone. The latter drug, an antagonist for progesterone and glucocorticoid receptors, has several attractive features: anti-tumor activity, low cytotoxicity to healthy cells, and modulation of the chemosensitivity of several cancer cell lines in vitro. Hence, the addition of mifepristone to temozolomide-based glioblastoma chemotherapy may lead to a better patient response. The mechanisms by which mifepristone enhances glioma treatment are not yet known. The current review aims to discuss the potential role of mifepristone as an adjuvant drug for the treatment of high-grade gliomas.

Glioblastoma-initiating cell heterogeneity generated by the cell-of-origin, genetic/epigenetic mutation and microenvironment

Glioblastoma (GBM) and other malignant tumours consist of heterogeneous cancer cells, including GBM-initiating cells (GICs). This heterogeneity is likely to arise from the following: different sets of genetic mutations and epigenetic modifications, which GICs gain in the transformation process; differences in cells of origin, such as stem cells, precursor cells or differentiated cells; and the cancer microenvironment, in which GICs communicate with neural cells, endothelial cells and immune cells. Furthermore, considering that various types of GICs can be generated at different time points of the transformation process, GBM very likely consists of heterogeneous GICs and their progeny. Because cancer cell heterogeneity is responsible for therapy resistance, it is crucial to develop methods of reducing such heterogeneity. Here, I summarize how GIC heterogeneity is generated in the transformation process and present how cell heterogeneity in cancer can be addressed based on recent findings.

Data-driven prioritization and preclinical evaluation of therapeutic targets in glioblastoma

Background

Patients with glioblastoma (GBM) have a dismal prognosis, and there is an unmet need for new therapeutic options. This study aims to identify new therapeutic targets in GBM.

Methods

mRNA expression data of patient-derived GBM (n = 1279) and normal brain tissue (n = 46) samples were collected from Gene Expression Omnibus and The Cancer Genome Atlas. Functional genomic mRNA profiling was applied to capture the downstream effects of genomic alterations on gene expression levels. Next, a class comparison between GBM and normal brain tissue was performed. Significantly upregulated genes in GBM were further prioritized based on (1) known interactions with antineoplastic drugs, (2) current drug development status in humans, and (3) association with biologic pathways known to be involved in GBM. Antineoplastic agents against prioritized targets were validated in vitro and in vivo.

Results

We identified 712 significantly upregulated genes in GBM compared to normal brain tissue, of which 27 have a known interaction with antineoplastic agents. Seventeen of the 27 genes, including EGFR and VEGFA, have been clinically evaluated in GBM with limited efficacy. For the remaining 10 genes, RRM2, MAPK9 (JNK2, SAPK1a), and XIAP play a role in GBM development. We demonstrated for the MAPK9 inhibitor RGB-286638 a viability loss in multiple GBM cell culture models. Although no overall survival benefit was observed in vivo, there were indications that RGB-286638 may delay tumor growth.

Conclusions

The MAPK9 inhibitor RGB-286638 showed promising in vitro results. Furthermore, in vivo target engagement studies and combination therapies with this compound warrant further exploration.

Loss of COPZ1 induces NCOA4 mediated autophagy and ferroptosis in glioblastoma cell lines

Dysregulated iron metabolism is a hallmark of many cancers, including glioblastoma (GBM). However, its role in tumor progression remains unclear. Herein, we identified coatomer protein complex subunit zeta 1 (COPZ1) as a therapeutic target candidate which significantly dysregulated iron metabolism in GBM cells. Overexpression of COPZ1 was associated with increasing tumor grade and poor prognosis in glioma patients based on analysis of expression data from the publicly available database The Cancer Genome Atlas (P < 0.001). Protein levels of COPZ1 were significantly increased in GBM compared to non-neoplastic brain tissue samples in immunohistochemistry and western blot analysis. SiRNA knockdown of COPZ1 suppressed proliferation of U87MG, U251 and P3#GBM in vitro. Stable expression of a COPZ1 shRNA construct in U87MG inhibited tumor growth in vivo by ~60% relative to controls at day 21 after implantation (P < 0.001). Kaplan-Meier analysis of the survival data demonstrated that the overall survival of tumor bearing animals increased from 20.8 days (control) to 27.8 days (knockdown, P < 0.05). COPZ1 knockdown also led to the increase in nuclear receptor coactivator 4 (NCOA4), resulting in the degradation of ferritin, and a subsequent increase in the intracellular levels of ferrous iron and ultimately ferroptosis. These data demonstrate that COPZ1 is a critical mediator in iron metabolism. The COPZ1/NCOA4/FTH1 axis is therefore a novel therapeutic target for the treatment of human GBM.

Inhibiting RRM2 to enhance the anticancer activity of chemotherapy

RRM2, the small subunit of ribonucleotide reductase, is identified as a tumor promotor and therapeutic target. It is common to see the overexpression of RRM2 in chemo-resistant cancer cells and patients. RRM2 mediates the resistance of many chemotherapeutic drugs and could become the predictor for chemosensitivity and prognosis. Therefore, inhibition of RRM2 may be an effective means to enhance the anticancer activity of chemotherapy. This review tries to discuss the mechanisms of RRM2 overexpression and the role of RRM2 in resistance to chemotherapy. Additionally, we compile the studies on small interfering RNA targets RRM2, RRM2 inhibitors, kinase inhibitors, and other ways that could overcome the resistance of chemotherapy or exert synergistic anticancer activity with chemotherapy through the expression inhibition or the enzyme inactivation of RRM2.

Present and Future of Anti-Glioblastoma Therapies: A Deep Look into Molecular Dependencies/Features

Glioblastoma (GBM) is aggressive malignant tumor residing within the central nervous system. Although the standard treatment options, consisting of surgical resection followed by combined radiochemotherapy, have long been established for patients with GBM, the prognosis is still poor. Despite recent advances in diagnosis, surgical techniques, and therapeutic approaches, the increased patient survival after such interventions is still sub-optimal. The unique characteristics of GBM, including highly infiltrative nature, hard-to-access location (mainly due to the existence of the blood brain barrier), frequent and rapid recurrence, and multiple drug resistance mechanisms, pose challenges to the development of an effective treatment. To overcome current limitations on GBM therapy and devise ideal therapeutic strategies, efforts should focus on an improved molecular understanding of GBM pathogenesis. In this review, we summarize the molecular basis for the development and progression of GBM as well as some emerging therapeutic approaches.

The natural compound obtusaquinone targets pediatric high-grade gliomas through ROS-mediated ER stress

Background

Pediatric high-grade gliomas (pHGGs) are aggressive primary brain tumors with local invasive growth and poor clinical prognosis. Treatment of pHGGs is particularly challenging given the intrinsic resistance to chemotherapy, an absence of novel therapeutics, and the difficulty of drugs to reach the tumor beds. Accumulating evidence suggests that production of reactive oxygen species (ROS) and misfolded proteins, which typically leads to endoplasmic reticulum (ER) stress, is an essential mechanism in cancer cell survival.

Methods

Several cell viability assays were used in 6 patient-derived pHGG cultures to evaluate the effect of the natural compound obtusaquinone (OBT) on cytotoxicity. Orthotopic mouse models were used to determine OBT effects in vivo. Immunoblotting, immunostaining, flow cytometry, and biochemical assays were used to investigate the OBT mechanism of action.

Results

OBT significantly inhibited cell survival of patient-derived pHGG cells in culture. OBT inhibited tumor growth and extended survival in 2 different orthotopic xenograft models. Mechanistically, OBT induced ER stress through abnormal ROS accumulation.

Conclusion

Our data demonstrate the utility and feasibility of OBT as a potential therapeutic option for improving the clinical treatment of pHGGs.

Novel Function of lncRNA ADAMTS9-AS2 in Promoting Temozolomide Resistance in Glioblastoma via Upregulating the FUS/MDM2 Ubiquitination Axis

Background

LncRNAs have been shown to play essential roles in cancer therapeutic response. However, the detailed mechanism of lncRNAs in temozolomide (TMZ) resistance in glioblastoma (GBM) remain to be elucidated.

Methods

To elucidate the mechanism maintaining TMZ resistance, we constructed two TMZ-resistant GBM cell lines (T98G-R/U118-R). LncRNAs from four public datasets were reanalyzed, and the candidate lncRNA ADAMTS9-AS2 was evaluated in TMZ-treated GBM patients and in vitro cell lines.

Results

Reanalysis of lncRNA expression profiles identified ADAMTS9-AS2 as significantly overexpressed in TMZ-resistant GBM cells and as positively associated with the IC₅₀ of TMZ in GBM cells. Overexpression of ADAMTS9-AS2 was also significantly associated with poor TMZ response and shorter progression-free survival (PFS) in TMZ-treated GBM patients. Knockdown of ADAMTS9-AS2 inhibited proliferation and attenuated the IC₅₀ of TMZ, as well as mitigating invasion and migration in TMZ-resistant GBM cells. Subsequent investigations indicated that reduced expression of ADAMTS9-AS2 significantly suppressed expression of the FUS protein, which was predicted as a direct substrate of ADAMTS9-AS2. Expression trends of FUS were directly correlated with those of ADAMTS9-AS2, as shown by increasing concentrations and prolonged treatment with TMZ. RNA pull-down and RIP assays indicated that both endogenous and exogenous ADAMTS9-AS2 directly binds to the RRM and Znf_RanBP2 domains of FUS, consequently increasing FUS protein expression. Knockdown of ADAMTS9-AS2 reduced the half-life of FUS and decreased FUS protein stability via K48 ubiquitin degradation. Moreover, the E3 ubiquitin-protein ligase MDM2 interacts with and down regulates FUS, while the RRM and Znf_RanBP2 domains of FUS facilitate its binding with MDM2. ADAMTS9-AS2 decreased the interaction between MDM2 and FUS, which mediates FUS K48 ubiquitination. Additionally, knockdown of the ADAMTS9-AS2/FUS signaling axis significantly alleviated progression and metastasis in TMZ-resistant cells.

Conclusion

ADAMTS9-AS2 possessed a novel function that promotes TMZ resistance via upregulating the FUS/MDM2 axis in GBM cells. The RRM or Znf_RanBP2 domains of FUS facilitate the combination of ADAMTS9-AS2 and FUS, competitively inhibiting MDM2-dependent FUS K48 ubiquitination and resulting in enhanced FUS stability and TMZ resistance. Our results suggest that the ADAMTS9-AS2/FUS/MDM2 axis may represent a suitable prognostic biomarker and a potential target in TMZ-resistant GBM therapy.

Patient-Derived Glioma Models: From Patients to Dish to Animals

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults associated with a poor survival. Current standard of care consists of surgical resection followed by radiation and chemotherapy. GBMs are highly heterogeneous, having a complex interaction among different cells within the tumor as well as the tumor microenvironment. One of the main challenges in the neuro-oncology field in general, and GBM in particular, is to find an optimum culture condition that maintains the molecular genotype and phenotype as well as heterogeneity of the original tumor in vitro and in vivo. Established cell lines were shown to be a poor model of the disease, failing to recapitulate the phenotype and harboring non-parental genotypic mutations. Given the growing understanding of GBM biology, the discovery of glioma cancer stem-like cells (GSCs), and their role in tumor formation and therapeutic resistance, scientists are turning more towards patient-derived cells and xenografts as a more representative model. In this review, we will discuss the current state of patient-derived GSCs and their xenografts; and provide an overview of different established models to study GBM biology and to identify novel therapeutics in the pre-clinical phase.

Current promising treatment strategy for glioblastoma multiform: A review

Glioblastoma multiform (GBM) is a heterogeneous group of primary neoplasm resistant to conventional therapies. Due to their infiltrative nature it not fully isolated by aggressive surgery, radiation and chemotherapy showing poor prognosis in glioma patients. Unfortunately, diagnosed patients die within 1.5-2 year treatment schedule. Currently temozolomide (TMZ) is the first choice for the prognosis of GBM patients. TMZ metabolites methyl triazen imidazol carboxamide form complex with alkyl guanine alkyl transferase (O6 MGMT- DNA repair protein) induced DNA damage following resistance properties of TMZ and inhibit the overall survival of the patients. Last few decades different TMZ conjugated strategy is developed to overcome the resistance and enhance the chemotherapy efficacy. The main aim of this review is to introduce the new promising pharmaceutical candidates that significantly influence the therapeutic response of the TMZ in context of targeted therapy of glioblastoma patients. It is hoped that this proposed strategy are highly effective to overcome the current resistance limitations of TMZ in GBM patients and enhance the survival rate of the patients.

Hydroxyurea promotes TET1 expression and induces apoptosis in osteosarcoma cells

Ten-eleven translocation (TET) proteins are abnormally expressed in various cancers. Osteosarcoma cells were treated with hydroxyurea to investigate the expression pattern of TET proteins in these cells. The expression of TET1 was increased in U2OS cells after treatment with hydroxyurea. In addition, hydroxyurea increased cell apoptosis and altered the cell cycle. TET proteins catalyze the oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC); therefore, 5mC and 5hmC levels were evaluated. Increased 5hmC levels were observed after the hydroxyurea treatment. Experiments examining cell apoptosis and the cell cycle after knockdown and overexpression of TET1 were conducted to further investigate whether TET1 expression affected cell growth. The overexpression of TET1 increased cell apoptosis and inhibited cell growth. Taken together, TET1 expression regulated proliferation and apoptosis in U2OS cells, changes that were associated with 5hmC levels.

Therapy for glioblastoma: is it working?

Glioblastoma (GBM) remains one of the most intransigent of cancers, with a median overall survival of only 15 months after diagnosis. Drug treatments have largely proven ineffective; it is thought that this is related to the heterogeneous nature and plasticity of GBM-initiating stem cell lineages. Although many combination drug therapies are being positioned to address tumour heterogeneity, the most promising therapeutic approaches for GBM to date appear to be those targeting GBM by vaccination or antibody- and cell-based immunotherapy. We review the most recent clinical trials for GBM and discuss the role of adaptive clinical trials in developing personalised treatment strategies to address intra- and inter-tumoral heterogeneity.