Modulatory effects of acetazolomide and dexamethasone on temozolomide-mediated apoptosis in human glioblastoma T98G and U87MG cells

Electric field-induced conformational dynamics of CA9: a potential biomarker for glioblastoma multiforme

GBM, a malignant brain tumor prevalent in adults, can be treated using Electric field (EF) therapy. However, the underlying mechanism of EF-based GBM therapy is not well understood. In this study, we used bioinformatics and MD analysis to explore CA9 in EF therapy for GBM. CA9 was identified as a differentially expressed gene (DEG) sensitive to EF stimulation in GBM using GEO and TCGA for integrated analysis. Elevated CA9 expression was associated with reduced overall survival in GBM patients, indicating that CA9 was an adverse prognostic factor. Single-cell data demonstrated that CA9 expression was significantly higher in GBM cells than in normal cells, suggesting that CA9 could be an EF-sensitive biomarker for GBM. GSVA analysis suggested that CA9 was related to hypoxia and glucose metabolism in glioblastoma. MD simulations were employed to examine the impact of EF (0 V/nm ≤ E ≤ 0.5 V/nm) on the conformation of the CA9 protein, including RMSF, RMSD, Rg, secondary structure, and dipole moment. The CA9 protein structure was altered with different EF intensities, affecting the motion of protein atoms in an EF intensity-dependent manner. The number of hydrogen bonds was significantly reduced as the EF intensity increased, indicating that EF disrupted the hydrogen bonds. Additionally, the EF intensity affected the dipole moment and characteristic time. Besides, the CA9 gene family analysis suggested that this gene family was highly conserved. Overall, CA9 showed potential as a GBM biomarker sensitive to EF, presenting a prospective target for therapeutic interventions in EF-mediated GBM treatment.

Effects of thymoquinone and the curcumin analog EF-24 on the activity of the enzyme paraoxonase-1 in human glioblastoma cells U87MG

The spices and aromatic herbs were used not only in cooking to add flavour and smell to dishes but also for medicinal use. Nigella sativa, also called black cumin, is one of the species that contains an important bioactive component, thymoquinone (TQ), which has antioxidant, anti-inflammatory, antimicrobial, and antidiabetic effects. Curcuma longa, which also includes curcumin, has numerous anti-cancer properties. However, the bioavailability of curcumin is lower than that of its analogs. An analog of curcumin (EF-24), which has better bioavailability than curcumin, is capable of exerting a high anti-cancer effect. In our study, we determined the effects of PON1 enzyme activity on the proliferation and aggressiveness of glioblastoma cancer treated with TQ and EF-24 from lysates of the glioblastoma cell line U87MG. The results were determined as increased PON1 activity after treatment with TQ and EF-24 in the U87MG cell line (p < 0.0001).

Dexamethasone in Patients with Glioblastoma: A Systematic Review and Meta-Analysis

OBJECTIVE

Glioblastomas are the most common primary central nervous system (CNS) tumors. Although modern management strategies have modestly improved overall survival, the prognosis remains dismal, with treatment side effects often impinging on the clinical course. Glioblastomas cause neurological dysfunction by infiltrating CNS tissue and via perifocal oedema formation. The administration of steroids such as dexamethasone is thought to alleviate symptoms by reducing oedema. However, despite its widespread use, the evidence for the administration of dexamethasone is limited and conflicting. Therefore, we aimed to review the current evidence concerning the use and outcomes of dexamethasone in patients with glioblastoma.

METHODS

We performed a systematic review and meta-analysis according to the PRISMA-P guidelines. We performed a restricted search using the keywords "Dexamethasone" and "Glioblastoma" on PubMed, Web of Science, Cochrane Library, and Academic Search Premier. We included studies reporting on overall survival (OS) and progression-free survival (PFS) in glioblastoma patients receiving higher or lower dexamethasone doses. The risk of bias was assessed using ROBINS-I. We performed a meta-analysis using a random effects model for OS and PFS.

RESULTS

Twenty-two retrospective studies were included. Higher doses of dexamethasone were associated with poorer OS (hazard ratio 1.62, confidence interval 1.40-1.88) and PFS (1.49, 1.23-1.81). OS remained worse even when studies corrected for clinical status (1.52, 1.38-1.67).

CONCLUSION

Despite the widespread use of dexamethasone in glioblastoma patients, its use is correlated with worse long-term outcomes. Consequently, Dexamethasone administration should be restricted to selected symptomatic patients. Future prospective studies are crucial to confirm these findings.

Methods for studying mammalian aquaporin biology

Aquaporins (AQPs), transmembrane water-conducting channels, have earned a great deal of scrutiny for their critical physiological roles in healthy and disease cell states, especially in the biomedical field. Numerous methods have been implemented to elucidate the involvement of AQP-mediated water transport and downstream signaling activation in eliciting whole cell, tissue, and organ functional responses. To modulate these responses, other methods have been employed to investigate AQP druggability. This review discusses standard in vitro, in vivo, and in silico methods for studying AQPs, especially for biomedical and mammalian cell biology applications. We also propose some new techniques and approaches for future AQP research to address current gaps in methodology.

Inhibition of Carbonic Anhydrase 2 Overcomes Temozolomide Resistance in Glioblastoma Cells

About 95% of Glioblastoma (GBM) patients experience tumor relapse as a consequence of resistance to the first-line standard chemotherapy using temozolomide (TMZ). Recent studies reported consistently elevated expression levels of carbonic anhydrase CA2 in recurrent glioblastoma and temozolomide-resistant glioblastoma stem-like cells (GSCs). Here we show that CA2 is preferentially expressed in GSCs and upregulated by TMZ treatment. When expressed in GBM cell lines, CA2 exerts significant metabolic changes reflected by enhanced oxygen consumption and increased extracellular acidification causing higher rates of cell invasion. Notably, GBM cells expressing CA2 respond to combined treatment with TMZ and brinzolamide (BRZ), a non-toxic and potent CA2 inhibitor. Interestingly, brinzolamide was more effective than the pan-CA inhibitor Acetazolamide (ACZ) to sensitize naïve GSCs and TMZ-resistant GSCs to TMZ induced cell death. Mechanistically, we demonstrated that the combined treatment of GBM stem cells with TMZ and BRZ caused autophagy of GBM cell lines and GSCs, reflected by enhanced LC3 cleavage (LC3-II) and p62 reduction. Our findings illustrate the potential of CA2 as a chemo-sensitizing drug target in recurrent GBM and propose a combined treatment of TMZ with CA2 inhibitor to tackle GBM chemoresistance and recurrence.

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.

The Paired Siglecs in Brain Tumours Therapy: The Immunomodulatory Effect of Dexamethasone and Temozolomide in Human Glioma In Vitro Model

The paired sialic acid-binding immunoglobulin like lectins (Siglecs) are characterized by similar cellular distribution and ligand recognition but opposing signalling functions attributed to different intracellular sequences. Since sialic acid—Siglec axis are known to control immune homeostasis, the imbalance between activatory and inhibitory mechanisms of glycan-dependent immune control is considered to promote pathology. The role of sialylation in cancer is described, however, its importance in immune regulation in gliomas is not fully understood. The experimental and clinical observation suggest that dexamethasone (Dex) and temozolomide (TMZ), used in the glioma management, alter the immunity within the tumour microenvironment. Using glioma-microglia/monocytes transwell co-cultures, we investigated modulatory action of Dex/TMZ on paired Siglecs. Based on real-time PCR and flow cytometry, we found changes in SIGLEC genes and their products. These effects were accompanied by altered cytokine profile and immune cells phenotype switching measured by arginases expression. Additionally, the exposure to Dex or TMZ increased the binding of inhibitory Siglec-5 and Siglec-11 fusion proteins to glioma cells. Our study suggests that the therapy-induced modulation of the interplay between sialoglycans and paired Siglecs, dependently on patient’s phenotype, is of particular signification in the immune surveillance in the glioma management and may be useful in glioma patient’s therapy plan verification.

BCL3 expression promotes resistance to alkylating chemotherapy in gliomas

The response of patients with gliomas to alkylating chemotherapy is heterogeneous. However, there are currently no universally accepted predictors of patient response to these agents. We identify the nuclear factor κB (NF-κB) co-regulator B cell CLL/lymphoma 3 (BCL-3) as an independent predictor of response to temozolomide (TMZ) treatment. In glioma patients with tumors that have a methylated O⁶-methylguanine DNA methyltransferase (MGMT) promoter, high BCL-3 expression was associated with a poor response to TMZ. Mechanistically, BCL-3 promoted a more malignant phenotype by inducing an epithelial-to-mesenchymal transition in glioblastomas through promoter-specific NF-κB dimer exchange. Carbonic anhydrase II (CAII) was identified as a downstream factor promoting BCL-3-mediated resistance to chemotherapy. Experiments in glioma xenograft mouse models demonstrated that the CAII inhibitor acetazolamide enhanced survival of TMZ-treated animals. Our data suggest that BCL-3 might be a useful indicator of glioma response to alkylating chemotherapy and that acetazolamide might be repurposed as a chemosensitizer for treating TMZ-resistant gliomas.

Comparative Transcriptomic Analysis of Temozolomide Resistant Primary GBM Stem-Like Cells and Recurrent GBM Identifies Up-Regulation of the Carbonic Anhydrase CA2 Gene as Resistance Factor

About 95% of patients with Glioblastoma (GBM) show tumor relapse, leaving them with limited therapeutic options as recurrent tumors are most often resistant to the first line chemotherapy standard Temozolomide (TMZ). To identify molecular pathways involved in TMZ resistance, primary GBM Stem-like Cells (GSCs) were isolated, characterized, and selected for TMZ resistance in vitro. Subsequently, RNA sequencing analysis was performed and revealed a total of 49 differentially expressed genes (|log2-fold change| > 0.5 and adjusted p-value < 0.1) in TMZ resistant stem-like cells compared to their matched DMSO control cells. Among up-regulated genes, we identified carbonic anhydrase 2 (CA2) as a candidate gene correlated with glioma malignancy and patient survival. Notably, we describe consistent up-regulation of CA2 not only in TMZ resistant GSCs on mRNA and protein level, but also in patient-matched clinical samples of first manifest and recurrent tumors. Co-treatment with the carbonic anhydrase inhibitor Acetazolamid (ACZ) sensitized cells to TMZ induced cell death. Cumulatively, our findings illustrate the potential of CA2 as a chemosensitizing target in recurrent GBM and provide a rationale for a therapy associated inhibition of CA2 to overcome TMZ induced chemoresistance.

From epidemiology and neurometabolism to treatment: Vitamin D in pathogenesis of glioblastoma Multiforme (GBM) and a proposal for Vitamin D + all-trans retinoic acid + Temozolomide combination in treatment of GBM

Here we review tumoricidal efficacy of Vitamin D analogues in glioblastoma multiforme (GBM) and potential synergisms with retinoic acid and temozolomide based on epidemiological and cellular studies. Epidemiological data suggest that winter birth is associated with higher risk of GBM, and GBM debulking in the winter enhanced mortality, which may relate with lower exposure to sunlight essential to convert cholecalciferol to Vitamin D. Comparative studies on blood bank specimens revealed that higher prediagnosis levels of calcidiol are associated with lower risk of GBM in elderly men. Supplemental Vitamin D reduced mortality in GBM patients in comparison to nonusers. Expression of Vitamin D Receptor is associated with a good prognosis in GBM. Conversely, Vitamin D increases glial tumor synthesis of neutrophins NGF and NT-3, the low affinity neurotrophin receptor p75NTR, IL-6 and VEGF, which may enhance glioma growth. Antitumor synergisms between temozolomide and Vitamin D and Vitamin D with Vitamin A derivatives were observed. Hence, we hypothesize that Calcitriol + ATRA (All-Trans Retinoic Acid) + Temozolomide - CAT combination might be a safer approach to benefit from Vitamin D in the management of high-grade glial tumors. Adding acetazolomide to this protocol may reduce the risk of pseudotumor cerebri, as both Vitamin D and Vitamin A excess may cause intracranial hypertension; this approach may provide further benefit as acetazolomide also exhibits anticancer activity.

Dexamethasone in Glioblastoma Multiforme Therapy: Mechanisms and Controversies

Glioblastoma multiforme (GBM) is the most common and malignant of the glial tumors. The world-wide estimates of new cases and deaths annually are remarkable, making GBM a crucial public health issue. Despite the combination of radical surgery, radio and chemotherapy prognosis is extremely poor (median survival is approximately 1 year). Thus, current therapeutic interventions are highly unsatisfactory. For many years, GBM-induced brain oedema and inflammation have been widely treated with dexamethasone (DEX), a synthetic glucocorticoid (GC). A number of studies have reported that DEX also inhibits GBM cell proliferation and migration. Nevertheless, recent controversial results provided by different laboratories have challenged the widely accepted dogma concerning DEX therapy for GBM. Here, we have reviewed the main clinical features and genetic and epigenetic abnormalities underlying GBM. Finally, we analyzed current notions and concerns related to DEX effects on cerebral oedema, cancer cell proliferation and migration and clinical outcome.

Paths for Improving Bevacizumab Available in 2018: The ADZT Regimen for Better Glioblastoma Treatment

During glioblastoma treatment, the pharmaceutical monoclonal antibody to vascular endothelial growth factor A, bevacizumab, has improved the quality of life and delayed progression for several months, but has not (or only marginally) prolonged overall survival. In 2017, several dramatic research papers appeared that are crucial to our understanding of glioblastoma vis-a-vis the mode of action of bevacizumab. As a consequence of these papers, a new, potentially more effective treatment protocol can be built around bevacizumab. This is the ADZT regimen, where four old drugs are added to bevacizumab. These four drugs are apremilast, marketed to treat psoriasis, dapsone, marketed to treat Hansen’s disease, zonisamide, marketed to treat seizures, and telmisartan, marketed to treat hypertension. The ancillary attributes of each of these drugs have been shown to augment bevacizumab. This paper details the research data supporting this contention. Phase three testing of AZDT addition to bevacizumab is required to establish safety and effectiveness before general use.

Addition of carbonic anhydrase 9 inhibitor SLC-0111 to temozolomide treatment delays glioblastoma growth in vivo

Tumor microenvironments can promote stem cell maintenance, tumor growth, and therapeutic resistance, findings linked by the tumor-initiating cell hypothesis. Standard of care for glioblastoma (GBM) includes temozolomide chemotherapy, which is not curative, due, in part, to residual therapy-resistant brain tumor-initiating cells (BTICs). Temozolomide efficacy may be increased by targeting carbonic anhydrase 9 (CA9), a hypoxia-responsive gene important for maintaining the altered pH gradient of tumor cells. Using patient-derived GBM xenograft cells, we explored whether CA9 and CA12 inhibitor SLC-0111 could decrease GBM growth in combination with temozolomide or influence percentages of BTICs after chemotherapy. In multiple GBMs, SLC-0111 used concurrently with temozolomide reduced cell growth and induced cell cycle arrest via DNA damage in vitro. In addition, this treatment shifted tumor metabolism to a suppressed bioenergetic state in vivo. SLC-0111 also inhibited the enrichment of BTICs after temozolomide treatment determined via CD133 expression and neurosphere formation capacity. GBM xenografts treated with SLC-0111 in combination with temozolomide regressed significantly, and this effect was greater than that of temozolomide or SLC-0111 alone. We determined that SLC-0111 improves the efficacy of temozolomide to extend survival of GBM-bearing mice and should be explored as a treatment strategy in combination with current standard of care.

Effects of antiepileptic drugs on mitochondrial functions, morphology, kinetics, biogenesis, and survival

OBJECTIVES

Antiepileptic drugs (AEDs) exhibit adverse and beneficial effects on mitochondria, which have a strong impact on the treatment of patients with a mitochondrial disorder (MID) with epilepsy (mitochondrial epilepsy). This review aims at summarizing and discussing recent findings concerning the effect of AEDs on mitochondrial functions and the clinical consequences with regard to therapy of mitochondrial epilepsy and of MIDs in general.

METHODS

Literature review.

RESULTS

AEDs may interfere with the respiratory chain, with non-respiratory chain enzymes, carrier proteins, or mitochondrial biogenesis, with carrier proteins, membrane-bound channels or receptors and the membrane potential, with anti-oxidative defense mechanisms, with morphology, dynamics and survival of mitochondria, and with the mtDNA. There are AEDs of which adverse effects outweigh beneficial effects, such as valproic acid, carbamazepine, phenytoin, or phenobarbital and there are AEDs in which beneficial effects dominate over mitochondrial toxic effects, such as lamotrigine, levetiracetam, gabapentin, or zonisamide. However, from most AEDs only little is known about their interference with mitochondria.

CONCLUSIONS

Mitochondrial epilepsy might be initially treated with AEDs with low mitochondrial toxic potential. Only in case mitochondrial epilepsy is refractory to these AEDs, AEDs with higher mitochondrial toxic potential might be tried. In patients carrying POLG1 mutations AEDs with high mitochondrial toxic potential are contraindicated.

Inhibition of carbonic anhydrase IX in glioblastoma multiforme

Carbonic anhydrase IX (CAIX) is a transmembrane enzyme upregulated in several types of tumors including glioblastoma multiforme (GBM). GBM is among the most aggressive tumors among gliomas. Temozolomide (TMZ) therapy combined with surgical or radiation approaches is the standard treatment but not effective in long term. In this study we tested the treatment with acetazolamide (ATZ), an inhibitor of CAIX, alone or combined with TMZ. The experiments were performed in 2D and 3D cultures (spheroids) using glioblastoma U251N and human brain tumor stem cells (BTSCs). Several proteins implicated in tumor cell death were also investigated. The key results from these studies suggest the following: (1) Cell death of human glioblastoma spheroids and BTSC is significantly increased with combined treatment after 7 days, and (2) the effectiveness of ATZ is significantly enhanced against BTSC and U251N when incorporated into nano-carriers. Collectively, these results point toward the usefulness of nano-delivery of CAIX inhibitors and their combination with chemotherapeutics for glioblastoma treatment.

The effects of antiepileptic drugs on the growth of glioblastoma cell lines

To determine the effects of antiepileptic drug compounds on glioblastoma cellular growth, we exposed glioblastoma cell lines to select antiepileptic drugs. The effects of selected antiepileptic drugs on glioblastoma cells were measured by MTT assay. For compounds showing significant inhibition, cell cycle analysis was performed. Statistical analysis was performed using SPSS. The antiepileptic compounds selected for screening included carbamazepine, ethosuximide, gabapentin, lamotrigine, levetiracetam, magnesium sulfate, oxcarbazepine, phenytoin, primidone, tiagabine, topiramate, valproic acid, and vigabatrin. Dexamethasone and temozolomide were used as a negative and positive control respectively. Our results showed temozolomide and oxcarbazepine significantly inhibited glioblastoma cell growth and reached IC50 at therapeutic concentrations. The other antiepileptic drugs screened were unable to reach IC50 at therapeutic concentrations. The metabolites of oxcarbazepine were also unable to reach IC50. Dexamethasone, ethosuximide, levetiracetam, and vigabatrin showed some growth enhancement though they did not reach statistical significance. The growth enhancement effects of ethosuximide, levetiracetam, and vigabatrin found in the study may indicate that these compounds should not be used for prophylaxis or short term treatment of epilepsy in glioblastoma. While valproic acid and oxcarbazepine were effective, the required dose of valproic acid was far above that used for the treatment of epilepsy and the metabolites of oxcarbazepine failed to reach significant growth inhibition ruling out the use of oral oxcarbazepine or valproic acid as monotherapy in glioblastoma. The possibility of using these compounds as local treatment is a future area of study.

Hypoxia and Its Acid-Base Consequences: From Mountains to Malignancy

Hypoxia, depending upon its magnitude and circumstances, evokes a spectrum of mild to severe acid-base changes ranging from alkalosis to acidosis, which can alter many responses to hypoxia at both non-genomic and genomic levels, in part via altered hypoxia-inducible factor (HIF) metabolism. Healthy people at high altitude and persons hyperventilating to non-hypoxic stimuli can become alkalotic and alkalemic with arterial pH acutely rising as high as 7.7. Hypoxia-mediated respiratory alkalosis reduces sympathetic tone, blunts hypoxic pulmonary vasoconstriction and hypoxic cerebral vasodilation, and increases hemoglobin oxygen affinity. These effects and others can be salutary or counterproductive to tissue oxygen delivery and utilization, based upon magnitude of each effect and summation. With severe hypoxia either in the setting of profound arterial hemoglobin desaturation and reduced O2 content or poor perfusion (ischemia) at the global or local level, metabolic and hypercapnic acidosis develop along with considerable lactate formation and pH falling to below 6.8. Although conventionally considered to be injurious and deleterious to cell function and survival, both acidoses may be cytoprotective by various anti-inflammatory, antioxidant, and anti-apoptotic mechanisms which limit total hypoxic or ischemic-reperfusion injury. Attempts to correct acidosis by giving bicarbonate or other alkaline agents under these circumstances ahead of or concurrent with reoxygenation efforts may be ill advised. Better understanding of this so-called "pH paradox" or permissive acidosis may offer therapeutic possibilities. Rapidly growing cancers often outstrip their vascular supply compromising both oxygen and nutrient delivery and metabolic waste disposal, thus limiting their growth and metastatic potential. However, their excessive glycolysis and lactate formation may not necessarily represent oxygen insufficiency, but rather the Warburg effect-an attempt to provide a large amount of small carbon intermediates to supply the many synthetic pathways of proliferative cell growth. In either case, there is expression and upregulation of many genes involved in acid-base homeostasis, in part by HIF-1 signaling. These include a unique isoform of carbonic anhydrase (CA-IX) and numerous membrane acid-base transporters engaged to maintain an optimal intracellular and extracellular pH for maximal growth. Inhibition of these proteins or gene suppression may have important therapeutic application in cancer chemotherapy.

Broad targeting of resistance to apoptosis in cancer

Apoptosis or programmed cell death is natural way of removing aged cells from the body. Most of the anti-cancer therapies trigger apoptosis induction and related cell death networks to eliminate malignant cells. However, in cancer, de-regulated apoptotic signaling, particularly the activation of an anti-apoptotic systems, allows cancer cells to escape this program leading to uncontrolled proliferation resulting in tumor survival, therapeutic resistance and recurrence of cancer. This resistance is a complicated phenomenon that emanates from the interactions of various molecules and signaling pathways. In this comprehensive review we discuss the various factors contributing to apoptosis resistance in cancers. The key resistance targets that are discussed include (1) Bcl-2 and Mcl-1 proteins; (2) autophagy processes; (3) necrosis and necroptosis; (4) heat shock protein signaling; (5) the proteasome pathway; (6) epigenetic mechanisms; and (7) aberrant nuclear export signaling. The shortcomings of current therapeutic modalities are highlighted and a broad spectrum strategy using approaches including (a) gossypol; (b) epigallocatechin-3-gallate; (c) UMI-77 (d) triptolide and (e) selinexor that can be used to overcome cell death resistance is presented. This review provides a roadmap for the design of successful anti-cancer strategies that overcome resistance to apoptosis for better therapeutic outcome in patients with cancer.

CUSP9* treatment protocol for recurrent glioblastoma: aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, ritonavir, sertraline augmenting continuous low dose temozolomide

CUSP9 treatment protocol for recurrent glioblastoma was published one year ago. We now present a slight modification, designated CUSP9*. CUSP9* drugs--aprepitant, artesunate, auranofin, captopril, celecoxib, disulfiram, itraconazole, sertraline, ritonavir, are all widely approved by regulatory authorities, marketed for non-cancer indications. Each drug inhibits one or more important growth-enhancing pathways used by glioblastoma. By blocking survival paths, the aim is to render temozolomide, the current standard cytotoxic drug used in primary glioblastoma treatment, more effective. Although esthetically unpleasing to use so many drugs at once, the closely similar drugs of the original CUSP9 used together have been well-tolerated when given on a compassionate-use basis in the cases that have come to our attention so far. We expect similarly good tolerability for CUSP9*. The combined action of this suite of drugs blocks signaling at, or the activity of, AKT phosphorylation, aldehyde dehydrogenase, angiotensin converting enzyme, carbonic anhydrase -2,- 9, -12, cyclooxygenase-1 and -2, cathepsin B, Hedgehog, interleukin-6, 5-lipoxygenase, matrix metalloproteinase -2 and -9, mammalian target of rapamycin, neurokinin-1, p-gp efflux pump, thioredoxin reductase, tissue factor, 20 kDa translationally controlled tumor protein, and vascular endothelial growth factor. We believe that given the current prognosis after a glioblastoma has recurred, a trial of CUSP9* is warranted.

Corticosteroid use in neuro-oncology: an update

Because of the lack of curative approaches for most patients with malignant brain tumors, supportive therapy, which aims at maintaining quality of life and functional independence, has a central role in the treatment of many patients. Steroids are particularly important in the setting of supportive therapy. They are commonly used to treat tumor-associated edema, and their administration is typically associated with rapid symptom relief, such as the resolution of headaches. Besides their antiedema activity, corticosteroids are characterized by their potent antilymphoma properties and their effects against acute or delayed emesis caused by systemic chemotherapy in cancer patients. Accordingly, steroids are among the most frequently used drugs in oncology. These desirable properties of steroids are counterbalanced by cardiovascular, muscular, and psychiatric side effects. On the cellular level, corticosteroids exert various effects that translate into the desired clinical activity, but they also evoke significant toxicity that may outweigh the beneficial effects. The mode of action and the limitations of steroid treatment are summarized in this review article. Interactions between steroids and other drugs must be considered. A particular challenge to the ongoing use of glucocorticoids is that newer therapeutic approaches are being introduced in neuro-oncology for which concomitant steroids are likely to be contraindicated. These include the emergence of various immunotherapeutic approaches including vaccination strategies and treatment with immune checkpoint inhibitors. Since the administration of steroids may interfere with the activity of these novel therapies, an even more critical evaluation of their use will be required.

Is there a common upstream link for autophagic and apoptotic cell death in human high-grade gliomas?

The prognosis of patients with human high-grade gliomas (HGGs) remains dismal despite major advances in their management, due mainly to the high resistance of these infiltrative tumor cells to programmed cell death (PCD). Most therapeutic strategies for HGGs are aimed to maximize PCD type I, apoptosis or type II, autophagy. These are predominantly distinctive processes, but many studies suggest a cross-talk between the two. A better understanding of the link between PCD types I and II might allow development of more effective therapies for HGGs. In this study, we examined whether there is a common upstream signaling event responsible for both apoptotic and autophagic PCD using 3 chemotherapeutic agents in human HGG cells. Our study shows that each agent caused a significant decrease in cell viability in each of the HGG cell lines tested. The increase rate of apoptosis and autophagy varied among cell lines and chemotherapeutic agents used. Increased expression of cytidine-cytidine-adenosine-adenosine-thymidine (C)/enhancer binding protein (EBP) homologous transcription factor C/EBP homologous protein (CHOP)/growth arrest and DNA damage-inducible gene 153 (GADD153) was documented after use of either pro-autophagic or pro-apoptotic agents. The involvement of CHOP/GADD153 in both type I and type II PCD was confirmed by overexpression and gene-silencing studies. Gene silencing by small-interfering RNA-mediated CHOP/GADD153 resulted in increased cell viability, decreased upregulation of microtubule-associated protein light-chain 3' type II (LC3II) and cleaved caspase-3, and inhibition of apoptosis and autophagy. Exogenous expression of CHOP/GADD153 triggered apoptosis and autophagy in the absence of other stimuli. The clinical significance of these findings was supported by the evidence that celecoxib, a nonsteroidal anti-inflammatory drug known to induce GADD153-mediated apoptosis, strongly increases both type I and type II PCD in HGG cells when combined with another inducer of GADD153. These data suggest that CHOP/GADD153 should be investigated as a novel targetable signaling step to improve therapies for HGGs.

Novel ways to target brain tumour metabolism

INTRODUCTION

Glioblastoma remains a highly aggressive primary brain cancer with very poor prognosis. The detection of mutations in the metabolic enzyme isocitrate dehydrogenase in gliomas, has broadened our view of tumourigenic mechanisms. Together with renewed awareness of tumour-specific energy metabolism, research is pointed towards novel ways for targeting brain cancer.

AREAS COVERED

This paper reviews recent knowledge on the possible tumourigenic mechanism of mutant isocitrate dehydrogenase, and provides a detailed overview of cancer-specific metabolic enzymes associated with glycolysis and intracellular pH regulation. It also discusses available drugs that may serve as a basis for novel drug development to target metabolic transformation in gliomas.

EXPERT OPINION

Despite the fact that energy metabolism is a very basic cellular process, tumour specific alterations in key metabolic processes represent promising targets for glioma treatment. Novel therapies against gliomas, including those that target metabolic transformation, need to consider the genetic background of the individual tumours, to allow the correlation of treatment response with the underlying biological status, both in preclinical and clinical studies.