Effect of aberrant p53 function on temozolomide sensitivity of glioma cell lines and brain tumor initiating cells from glioblastoma

The theory of massively repeated evolution and full identifications of cancer-driving nucleotides (CDNs)

Tumorigenesis, like most complex genetic traits, is driven by the joint actions of many mutations. At the nucleotide level, such mutations are cancer-driving nucleotides (CDNs). The full sets of CDNs are necessary, and perhaps even sufficient, for the understanding and treatment of each cancer patient. Currently, only a small fraction of CDNs is known as most mutations accrued in tumors are not drivers. We now develop the theory of CDNs on the basis that cancer evolution is massively repeated in millions of individuals. Hence, any advantageous mutation should recur frequently and, conversely, any mutation that does not is either a passenger or deleterious mutation. In the TCGA cancer database (sample size n=300-1000), point mutations may recur in i out of n patients. This study explores a wide range of mutation characteristics to determine the limit of recurrences (i*) driven solely by neutral evolution. Since no neutral mutation can reach i*=3, all mutations recurring at i≥3 are CDNs. The theory shows the feasibility of identifying almost all CDNs if n increases to 100,000 for each cancer type. At present, only <10% of CDNs have been identified. When the full sets of CDNs are identified, the evolutionary mechanism of tumorigenesis in each case can be known and, importantly, gene targeted therapy will be far more effective in treatment and robust against drug resistance.

Acquired Temozolomide Resistance Instructs Patterns of Glioblastoma Behavior in Gelatin Hydrogels

Acquired drug resistance in glioblastoma (GBM) presents a major clinical challenge and is a key factor contributing to abysmal prognosis, with less than 15 months median overall survival. Aggressive chemotherapy with the frontline therapeutic, temozolomide (TMZ), ultimately fails to kill residual highly invasive tumor cells after surgical resection and radiotherapy. Here, a 3D engineered model of acquired TMZ resistance is reported using two isogenically matched sets of GBM cell lines encapsulated in gelatin methacrylol hydrogels. Response of TMZ-resistant versus TMZ-sensitive GBM cell lines within the gelatin-based extracellular matrix platform is benchmarked and drug response at physiologically relevant TMZ concentrations is further validated. The changes in drug sensitivity, cell invasion, and matrix-remodeling cytokine production are shown as the result of acquired TMZ resistance. This platform lays the foundation for future investigations targeting key elements of the GBM tumor microenvironment to combat GBM's devastating impact by advancing the understanding of GBM progression and treatment response to guide the development of novel treatment strategies.

Evidence That a Peptide-Drug/p53 Gene Complex Promotes Cognate Gene Expression and Inhibits the Viability of Glioblastoma Cells

Glioblastoma multiform (GBM) is considered the deadliest brain cancer. Conventional therapies are followed by poor patient survival outcomes, so novel and more efficacious therapeutic strategies are imperative to tackle this scourge. Gene therapy has emerged as an exciting and innovative tool in cancer therapy. Its combination with chemotherapy has significantly improved therapeutic outcomes. In line with this, our team has developed temozolomide-transferrin (Tf) peptide (WRAP5)/p53 gene nanometric complexes that were revealed to be biocompatible with non-cancerous cells and in a zebrafish model and were able to efficiently target and internalize into SNB19 and U373 glioma cell lines. The transfection of these cells, mediated by the formulated peptide-drug/gene complexes, resulted in p53 expression. The combined action of the anticancer drug with p53 supplementation in cancer cells enhances cytotoxicity, which was correlated to apoptosis activation through quantification of caspase-3 activity. In addition, increased caspase-9 levels revealed that the intrinsic or mitochondrial pathway of apoptosis was implicated. This assumption was further evidenced by the presence, in glioma cells, of Bax protein overexpression-a core regulator of this apoptotic pathway. Our findings demonstrated the great potential of peptide TMZ/p53 co-delivery complexes for cellular transfection, p53 expression, and apoptosis induction, holding promising therapeutic value toward glioblastoma.

The role of KDM4A-mediated histone methylation on temozolomide resistance in glioma cells through the HUWE1/ROCK2 axis

Temozolomide (TMZ) resistance presents a significant challenge in the treatment of gliomas. Although lysine demethylase 4A (KDM4A) has been implicated in various cancer-related processes, its role in TMZ resistance remains unclear. This study aims to elucidate the contribution of KDM4A to TMZ resistance in glioma cells and its potential implications for glioma prognosis. We assessed the expression of KDM4A in glioma cells (T98G and U251MG) using qRT-PCR and Western blot assays. To explore the role of KDM4A in TMZ resistance, we transfected siRNA targeting KDM4A into drug-resistant glioma cells. Cell viability was assessed using the CCK-8 assay and the TMZ IC50 value was determined. ChIP assays were conducted to investigate KDM4A, H3K9me3, and H3K36me3 enrichment on the promoters of ROCK2 and HUWE1. Co-immunoprecipitation confirmed the interaction between HUWE1 and ROCK2, and we examined the levels of ROCK2 ubiquitination following MG132 treatment. Notably, T98G cells exhibited greater resistance to TMZ than U251MG cells, and KDM4A displayed high expression in T98G cells. Inhibiting KDM4A resulted in decreased cell viability and a reduction in the TMZ IC50 value. Mechanistically, KDM4A promoted ROCK2 transcription by modulating H3K9me3 levels. Moreover, disruption of the interaction between HUWE1 and ROCK2 led to reduced ROCK2 ubiquitination. Inhibition of HUWE1 or overexpression of ROCK2 counteracted the sensitization effect of si-KDM4A on TMZ responsiveness in T98G cells. Our findings highlight KDM4A's role in enhancing TMZ resistance in glioma cells by modulating ROCK2 and HUWE1 transcription and expression through H3K9me3 and H3K36me3 removal.

Acquired temozolomide resistance instructs patterns of glioblastoma behavior in gelatin hydrogels

Acquired drug resistance in glioblastoma (GBM) presents a major clinical challenge and is a key factor contributing to abysmal prognosis, with less than 15 months median overall survival. Aggressive chemotherapy with the frontline therapeutic, temozolomide (TMZ), ultimately fails to kill residual highly invasive tumor cells after surgical resection and radiotherapy. Here, we report a three-dimensional (3D) engineered model of acquired TMZ resistance using two isogenically-matched sets of GBM cell lines encapsulated in gelatin methacrylol hydrogels. We benchmark response of TMZ-resistant vs. TMZ-sensitive GBM cell lines within the gelatin-based extracellular matrix platform and further validate drug response at physiologically relevant TMZ concentrations. We show changes in drug sensitivity, cell invasion, and matrix-remodeling cytokine production as the result of acquired TMZ resistance. This platform lays the foundation for future investigations targeting key elements of the GBM tumor microenvironment to combat GBM's devastating impact by advancing our understanding of GBM progression and treatment response to guide the development of novel treatment strategies.

Teaser

A hydrogel model to investigate the impact of acquired drug resistance on functional response in glioblastoma.

Temozolomide and Lomustine Induce Tissue Factor Expression and Procoagulant Activity in Glioblastoma Cells In Vitro

Glioblastoma (GBM) patients have one of the highest risks of venous thromboembolism (VTE), which is even further increased upon treatment with chemotherapy. Tissue factor (TF) is the initiator of the extrinsic coagulation pathway and expressed by GBM cells. In this study, we aimed to examine the effect of routinely used chemotherapeutic agents Temozolomide (TMZ) and Lomustine (LOM) on TF procoagulant activity and expression in GBM cells in vitro. Three human GBM cell lines (U-251, U-87, U-118) were exposed to 100 µM TMZ or 30 µM LOM for 72 h. TF procoagulant activity was assessed via an FXa generation assay and TF gene and protein expression through qPCR and Western blotting. The externalization of phosphatidylserine (PS) was studied using Annexin V flow cytometry. Treatment with TMZ and LOM resulted in increased procoagulant activity in all cell lines. Furthermore, both agents induced procoagulant activity in the supernatant and tumor-cell-secreted extracellular vesicles. In line, TF gene and protein expression were increased upon TMZ and LOM treatment. Additionally, PS externalization and induction of inflammatory-associated genes were observed. Overall, the chemotherapeutic modalities TMZ and LOM induced procoagulant activity and increased TF gene and protein expression in all GBM cell lines tested, which may contribute to the increased VTE risk observed in GBM patients undergoing chemotherapy.

The miR-27a-3p/FTO axis modifies hypoxia-induced malignant behaviors of glioma cells

<p indent="0mm">Glioblastoma multiforme (GBM) is one of the most malignant types of central nervous system (CNS) tumors. N6-methyladenine (m6A) RNA modification is a main type of RNA modification in eukaryotic cells. In this study, we find that the m6A RNA methylation eraser FTO is dramatically downregulated in glioma samples and cell lines, particularly in intermediate and core regions and hypoxia-challenged glioma cells. <italic>In vitro</italic>, FTO overexpression inhibits the hypoxia-induced capacities of glioma cells to proliferate, migrate and invade, and decreases the percentage of cells with m6A RNA methylation. <italic>In vivo</italic>, FTO overexpression inhibits tumor growth in the xenograft model and decreases the protein levels of migration markers, including Vimentin and Twist. miR-27a-3p is upregulated within glioma intermediate and core regions and hypoxia-challenged glioma cells. miR-27a-3p inhibits the expression of FTO via direct binding to FTO. miR-27a-3p overexpression promotes hypoxia-challenged glioma cell aggressiveness, whereas FTO overexpression partially diminishes the oncogenic effects of miR-27a-3p overexpression. FTO overexpression promotes the nuclear translocation of FOXO3a and upregulates the expression levels of the <sc>FOXO3a</sc> downstream targets BIM, BNIP3, BCL-6, and PUMA, possibly by interacting with FOXO3a. Conclusively, FTO serves as a tumor suppressor in glioma by suppressing hypoxia-induced malignant behaviors of glioma cells, possibly by promoting the nuclear translocation of FOXO3a and upregulating FOXO3a downstream targets. miR-27a-3p is a major contributor to FTO downregulation in glioma under hypoxia. </p>.

p53 Modulates Radiosensitivity in Head and Neck Cancers-From Classic to Future Horizons

p53, initially considered a tumor suppressor, has been the subject of research related to cancer treatment resistance in the last 30 years. The unfavorable response to multimodal therapy and the higher recurrence rate, despite an aggressive approach, make HNSCC a research topic of interest for improving therapeutic outcomes, even if it is only the sixth most common malignancy worldwide. New advances in molecular biology and genetics include the involvement of miRNA in the control of the p53 pathway, the understanding of mechanisms such as gain/loss of function, and the development of different methods to restore p53 function, especially for HPV-negative cases. The different ratio between mutant p53 status in the primary tumor and distant metastasis originating HNSCC may serve to select the best therapeutic target for activating an abscopal effect by radiotherapy as a "booster" of the immune system. P53 may also be a key player in choosing radiotherapy fractionation regimens. Targeting any pathway involving p53, including tumor metabolism, in particular the Warburg effect, could modulate the radiosensitivity and chemo-sensitivity of head and neck cancers.

ONX-0914 Induces Apoptosis and Autophagy with p53 Regulation in Human Glioblastoma Cells

Glioblastoma is believed to be one of the most aggressive brain tumors in the world. ONX-0914 (PR957) is a selective inhibitor of proteasome subunit beta type-8 (PSMB8). Previous studies have shown that inhibiting PSMB8 expression in glioblastoma reduces tumor progression. Therefore, this study aimed to determine whether ONX-0914 has antitumor effects on human glioblastoma. The results indicated that ONX-0914 treatment inhibited survival in LN229, GBM8401, and U87MG glioblastoma cells. Cell cycle analysis showed that ONX-0914 treatment caused cell cycle arrest at the G1 phase and apoptosis in glioblastoma cells. The protein expression of BCL-2 was reduced and PARP was cleaved after ONX-0914 treatment. Furthermore, the levels of p53 and phosphorylated p53 were increased by ONX-0914 treatment in glioblastoma cells. ONX-0914 also induced autophagy in glioblastoma cells. Furthermore, the p53 inhibitor pifithrin attenuated apoptosis but enhanced autophagy caused by ONX-0914. In an orthotopic mouse model, TMZ plus ONX-0914 reduced tumor progression better than the control or TMZ alone. These data suggest that ONX-0914 is a novel therapeutic drug for glioblastoma.

Emerging role of ferroptosis in glioblastoma: Therapeutic opportunities and challenges

Glioblastoma (GBM) is the most common malignant craniocerebral tumor. The treatment of this cancer is difficult due to its high heterogeneity and immunosuppressive microenvironment. Ferroptosis is a newly found non-apoptotic regulatory cell death process that plays a vital role in a variety of brain diseases, including cerebral hemorrhage, neurodegenerative diseases, and primary or metastatic brain tumors. Recent studies have shown that targeting ferroptosis can be an effective strategy to overcome resistance to tumor therapy and immune escape mechanisms. This suggests that combining ferroptosis-based therapies with other treatments may be an effective strategy to improve the treatment of GBM. Here, we critically reviewed existing studies on the effect of ferroptosis on GBM therapies such as chemotherapy, radiotherapy, immunotherapy, and targeted therapy. In particular, this review discussed the potential of ferroptosis inducers to reverse drug resistance and enhance the sensitivity of conventional cancer therapy in combination with ferroptosis. Finally, we highlighted the therapeutic opportunities and challenges facing the clinical application of ferroptosis-based therapies in GBM. The data generated here provide new insights and directions for future research on the significance of ferroptosis-based therapies in GBM.

Alterations in Molecular Profiles Affecting Glioblastoma Resistance to Radiochemotherapy: Where Does the Good Go?

Simple Summary

Glioblastoma is a type of brain cancer that remains incurable. Despite multiple past and ongoing preclinical studies and clinical trials, involving adjuvants to the conventional therapy and based on molecular targeting, no relevant benefit for patients’ survival has been achieved so far. The current first-line treatment regimen is based on ionizing radiation and the monoalkylating compound, temozolomide, and has been administered for more than 15 years. Glioblastoma is extremely resistant to most agents due to a mutational background that elicits quick response to insults and adapts to microenvironmental and metabolic changes. Here, we present the most recent evidence concerning the molecular features and their alterations governing pathways involved in GBM response to the standard radio-chemotherapy and discuss how they collaborate with acquired GBM’s resistance.

Abstract

Glioblastoma multiforme (GBM) is a brain tumor characterized by high heterogeneity, diffuse infiltration, aggressiveness, and formation of recurrences. Patients with this kind of tumor suffer from cognitive, emotional, and behavioral problems, beyond exhibiting dismal survival rates. Current treatment comprises surgery, radiotherapy, and chemotherapy with the methylating agent, temozolomide (TMZ). GBMs harbor intrinsic mutations involving major pathways that elicit the cells to evade cell death, adapt to the genotoxic stress, and regrow. Ionizing radiation and TMZ induce, for the most part, DNA damage repair, autophagy, stemness, and senescence, whereas only a small fraction of GBM cells undergoes treatment-induced apoptosis. Particularly upon TMZ exposure, most of the GBM cells undergo cellular senescence. Increased DNA repair attenuates the agent-induced cytotoxicity; autophagy functions as a pro-survival mechanism, protecting the cells from damage and facilitating the cells to have energy to grow. Stemness grants the cells capacity to repopulate the tumor, and senescence triggers an inflammatory microenvironment favorable to transformation. Here, we highlight this mutational background and its interference with the response to the standard radiochemotherapy. We discuss the most relevant and recent evidence obtained from the studies revealing the molecular mechanisms that lead these cells to be resistant and indicate some future perspectives on combating this incurable tumor.

Temozolomide is additive with cytotoxic effect of irradiation in canine glioma cell lines

BACKGROUND

Similar to human glioblastoma patients, glial tumours in dogs have high treatment resistance and a guarded prognosis. In human medicine, the addition of temozolomide to radiotherapy leads to a favourable outcome in vivo as well as a higher antiproliferative effect on tumour cells in vitro.

OBJECTIVES

The aim of the study was to determine the radio- and temozolomide-sensitivity of three canine glial tumour cell lines and to investigate a potential additive cytotoxic effect in combined treatment. Additionally, we wanted to detect the level of MGMT promoter methylation in these cell lines and to investigate a potential association between MGMT promoter methylation and treatment resistance.

METHODS

Cells were treated with various concentrations of temozolomide and/or irradiated with 4 and 8 Gy. Radiosensitization by temozolomide was evaluated using proliferation assay and clonogenic assay, and MGMT DNA methylation was investigated using bisulfite next-generation sequencing.

RESULTS

In all tested canine cell lines, clonogenicity was inhibited significantly in combined treatment compared to radiation alone. All canine glial cell lines tested in this study were found to have high methylation levels of MGMT promoter.

CONCLUSIONS

Hence, an additive effect of combined treatment in MGMT negative canine glial tumour cell lines in vitro was detected. This motivates to further investigate the association between treatment resistance and MGMT, such as MGMT promoter methylation status.

TP53 Mutation Is a Prognostic Factor in Lower Grade Glioma and May Influence Chemotherapy Efficacy

BACKGROUND

Identification of prognostic biomarkers in cancers is a crucial step to improve overall survival (OS). Although mutations in tumour protein 53 (TP53) is prevalent in astrocytoma, the prognostic effects of TP53 mutation are unclear.

METHODS

In this retrospective study, we sequenced TP53 exons 1 to 10 in a cohort of 102 lower-grade glioma (LGG) subtypes and determined the prognostic effects of TP53 mutation in astrocytoma and oligodendroglioma. Publicly available datasets were analysed to confirm the findings.

RESULTS

In astrocytoma, mutations in TP53 codon 273 were associated with a significantly increased OS compared to the TP53 wild-type (HR (95% CI): 0.169 (0.036-0.766), p = 0.021). Public datasets confirmed these findings. TP53 codon 273 mutant astrocytomas were significantly more chemosensitive than TP53 wild-type astrocytomas (HR (95% CI): 0.344 (0.13-0.88), p = 0.0148). Post-chemotherapy, a significant correlation between TP53 and YAP1 mRNA was found (p = 0.01). In O (6)-methylguanine methyltransferase (MGMT) unmethylated chemotherapy-treated astrocytoma, both TP53 codon 273 and YAP1 mRNA were significant prognostic markers. In oligodendroglioma, TP53 mutations were associated with significantly decreased OS.

CONCLUSIONS

Based on these findings, we propose that certain TP53 mutant astrocytomas are chemosensitive through the involvement of YAP1, and we outline a potential mechanism. Thus, TP53 mutations may be key drivers of astrocytoma therapeutic efficacy and influence survival outcomes.

Combinatorial Effect of Temozolomide and Naringenin in Human Glioblastoma Multiforme Cell Lines

Glioblastoma multiforme (GBM) is a grade IV, lethal, and the most common type of brain tumor. GBM can acquire resistance to temozolomide (TMZ) recommended for its treatment. Naringenin (NAG), a flavonoid generally found in grapefruit, has antioxidant, anti-proliferative, and anti-inflammatory properties. It has been reported that phytochemicals can reduce resistance and improve the efficacy of a chemo-resistant drug. The combinatorial effect of TMZ and NAG on cell proliferation was evaluated using 3-4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT) assay, and the apoptosis in the U87MG and LN229 GBM cells were evaluated by change in fluorescence intensity. The effect of NAG and TMZ on anchorage-independent single-cell colony formation and cell migration was investigated. NAG and TMZ demonstrated enhanced cytotoxic effects on U87MG and LN229 cell lines. The combination index value being less than one indicated the synergistic action of the two drugs in restricting the growth of the cells. The NAG and TMZ together resulted in higher fluorescence intensity as compared to the alone drug. Further, the study showed a marked reduction in the migration of the cells and the formation of a single cell colony.Supplemental data for this article is available online at https://doi.org/10.1080/01635581.2021.1952438.

Long Noncoding RNA OR7E156P/miR-143/HIF1A Axis Modulates the Malignant Behaviors of Glioma Cell and Tumor Growth in Mice

Gliomas are characterized by high incidence, recurrence and mortality all of which are significant challenges to efficacious clinical treatment. The hypoxic microenvironment in the inner core and intermediate layer of the tumor mass of gliomas is a critical contributor to glioma pathogenesis. In this study, we identified an upregulated lncRNA, OR7E156P, in glioma was identified. The silencing of OR7E156P inhibited cell invasion and DNA synthesis in vitro and tumor growth in vivo. OR7E156P was intricately linked to the HIF1A pathway. Hypoxia could induce OR7E156P expression, whereas OR7E156P silencing decreased HIF1A protein levels under hypoxic conditions. Hypoxia promoted glioma cell invasion and DNA synthesis, and HUVEC tube formation, whereas OR7E156P silencing partially reversed the cellular effects of hypoxia. HIF1A overexpression promoted, whereas OR7E156P silencing inhibited tumor growth; the inhibitory effects of OR7E156P silencing on tumor growth were partially reversed by HIF1A overexpression. miR-143 directly targeted OR7E156P and HIF1A, respectively. miR-143 inhibition increased HIF1A protein levels, promoted glioma cell invasion and DNA synthesis. Moreover, they enhanced HUVEC tube formation, whereas OR7E156P silencing partially reversed the cellular effects of miR-143 inhibition. HIF1A targeted the promoter region of miR-143 and inhibited miR-143 expression. Altogether a regulatory axis consisting of OR7E156P, miR-143, and HIF1A, was identified which is deregulated in glioma, and the process of the OR7E156P/miR-143/HIF1A axis modulating glioma cell invasion through ZEB1 and HUVEC tube formation through VEGF was demonstrated.

Genotoxic therapy and resistance mechanism in gliomas

Glioma is one of the most common and lethal brain tumors. Surgical resection followed by radiotherapy plus chemotherapy is the current standard of care for patients with glioma. The existence of resistance to genotoxic therapy, as well as the nature of tumor heterogeneity greatly limits the efficacy of glioma therapy. DNA damage repair pathways play essential roles in many aspects of glioma biology such as cancer progression, therapy resistance, and tumor relapse. O6-methylguanine-DNA methyltransferase (MGMT) repairs the cytotoxic DNA lesion generated by temozolomide (TMZ), considered as the main mechanism of drug resistance. In addition, mismatch repair, base excision repair, and homologous recombination DNA repair also play pivotal roles in treatment resistance as well. Furthermore, cellular mechanisms, such as cancer stem cells, evasion from apoptosis, and metabolic reprogramming, also contribute to TMZ resistance in gliomas. Investigations over the past two decades have revealed comprehensive mechanisms of glioma therapy resistance, which has led to the development of novel therapeutic strategies and targeting molecules.

Control of brain tumor growth by reactivating myeloid cells with niacin

Glioblastomas are generally incurable partly because monocytes, macrophages, and microglia in afflicted patients do not function in an antitumor capacity. Medications that reactivate these macrophages/microglia, as well as circulating monocytes that become macrophages, could thus be useful to treat glioblastoma. We have discovered that niacin (vitamin B3) is a potential stimulator of these inefficient myeloid cells. Niacin-exposed monocytes attenuated the growth of brain tumor-initiating cells (BTICs) derived from glioblastoma patients by producing anti-proliferative interferon-α14. Niacin treatment of mice bearing intracranial BTICs increased macrophage/microglia representation within the tumor, reduced tumor size, and prolonged survival. These therapeutic outcomes were negated in mice depleted of circulating monocytes or harboring interferon-α receptor-deleted BTICs. Combination treatment with temozolomide enhanced niacin-promoted survival. Monocytes from glioblastoma patients had increased interferon-α14 upon niacin exposure and were reactivated to reduce BTIC growth in culture. We highlight niacin, a common vitamin that can be quickly translated into clinical application, as an immune stimulator against glioblastomas.

Application of the antitussive agents oxelaidin and butamirate as anti-glioma agents

Glioblastoma (GBM) is an aggressive brain tumor with a strong tendency of relapse and resistance to chemotherapy, but we currently lack non-toxic agents that effectively treat GBM. In this study, high-throughput screening of FDA-approved drugs was performed to identify safe and effective molecules and test their effect on GBM cell lines, LN229, U87 and T98G. Cough suppressants, oxelaidin and butamirate inhibited GBM growth. A Ras family GTPase, Ras-related associated with diabetes (RRAD), contributes to activation of STAT3, which is essential for survival and growth of many cancer types. Interestingly, oxelaidin and butamirate did not affect proliferation in RRAD negative GBM cells. Docking simulation analyses revealed selective interactions between oxelaidin and RRAD. The mechanism by which butamirate and oxelaidin inhibits GBM cell growth involves the suppression of STAT3 transcriptional activity, leading to down-regulation of cyclin D1 and survivin. In addition, components of RRAD-associated signaling cascades, including p-EGFR, p-Akt, and p-STAT3, were inhibited upon oxelaidin treatment. Intraperitoneal administration of oxelaidin or butamirate markedly suppressed tumor growth in a glioblastoma xenograft mouse model without significant adverse effects. Our collective findings indicate that oxelaidin and butamirate exert anti-tumor effects in glioblastoma, supporting its utility as a novel therapeutic candidate for glioblastoma.

The miR-223-3p/MAP1B axis aggravates TGF-β-induced proliferation and migration of BPH-1 cells

Uncontrolled proliferation and migration of benign prostatic hyperplasia (BPH) epithelial cells play a critical role in the pathogenesis of BPH. The regulatory roles of microRNAs (miRNAs) in multiple human diseases have been observed. This study was dedicated to investigating the regulatory effects of the miR-223-3p on the proliferation and migration of BPH progress. In the present study, the aberrant upregulation of miR-223-3p in BPH samples and BPH-1 cells was determined. TGF-β stimulation induced miR-223-3p expression, promoted BPH-1 cell viability and DNA synthesis, inhibited BPH-1 cell apoptosis, and decreased pro-apoptotic Bax/caspase 3. These changes induced by TGF-β stimulation were further enhanced the overexpression of miR-223-3p and attenuated via the inhibition of miR-223-3p. Under TGF-β stimulation, the overexpression of miR-223-3p enhanced, whereas the inhibition of miR-223-3p inhibited the EMT and MAPK signaling pathways. By targeting the MAP1B 3'UTR, miR-223-3p repressed MAP1B expression. In contrast to miR-223-3p overexpression, MAP1B overexpression attenuated TGF-β-induced changes in BPH-1 cell phenotypes, pro-apoptotic Bax/caspase 3, and the EMT and MAPK signaling pathways; more importantly, MAP1B overexpression significantly attenuated the roles of miR-223-3p overexpression in BPH-1 cell phenotypes, pro-apoptotic Bax/caspase 3, and the EMT and MAPK signaling pathways under TGF-β stimulation. In conclusion, miR-223-3p aggravates the uncontrolled proliferation and migration of BPH-1 cells through targeting MAP1B. The EMT and MAPK signaling pathways might be involved.

Simvastatin Induces Unfolded Protein Response and Enhances Temozolomide-Induced Cell Death in Glioblastoma Cells

Glioblastoma (GBM) is the most prevalent malignant primary brain tumor with a very poor survival rate. Temozolomide (TMZ) is the common chemotherapeutic agent used for GBM treatment. We recently demonstrated that simvastatin (Simva) increases TMZ-induced apoptosis via the inhibition of autophagic flux in GBM cells. Considering the role of the unfolded protein response (UPR) pathway in the regulation of autophagy, we investigated the involvement of UPR in Simva–TMZ-induced cell death by utilizing highly selective IRE1 RNase activity inhibitor MKC8866, PERK inhibitor GSK-2606414 (PERKi), and eIF2α inhibitor salubrinal. Simva–TMZ treatment decreased the viability of GBM cells and significantly increased apoptotic cell death when compared to TMZ or Simva alone. Simva–TMZ induced both UPR, as determined by an increase in GRP78, XBP splicing, eukaryote initiation factor 2α (eIF2α) phosphorylation, and inhibited autophagic flux (accumulation of LC3β-II and inhibition of p62 degradation). IRE1 RNase inhibition did not affect Simva–TMZ-induced cell death, but it significantly induced p62 degradation and increased the microtubule-associated proteins light chain 3 (LC3)β-II/LC3β-I ratio in U87 cells, while salubrinal did not affect the Simva–TMZ induced cytotoxicity of GBM cells. In contrast, protein kinase RNA-like endoplasmic reticulum kinase (PERK) inhibition significantly increased Simva–TMZ-induced cell death in U87 cells. Interestingly, whereas PERK inhibition induced p62 accumulation in both GBM cell lines, it differentially affected the LC3β-II/LC3β-I ratio in U87 (decrease) and U251 (increase) cells. Simvastatin sensitizes GBM cells to TMZ-induced cell death via a mechanism that involves autophagy and UPR pathways. More specifically, our results imply that the IRE1 and PERK signaling arms of the UPR regulate Simva–TMZ-mediated autophagy flux inhibition in U251 and U87 GBM cells.

ANXA2P2/miR-9/LDHA axis regulates Warburg effect and affects glioblastoma proliferation and apoptosis

BACKGROUND

Aerobic glycolysis is a unique tumor cell phenotype considered as one of the hallmarks of cancer. Aerobic glycolysis can accelerate tumor development by increasing glucose uptake and lactate production. In the present study, lactate dehydrogenase A (LDHA) is significantly increased within glioma tissue samples and cells, further confirming the oncogenic role of LDHA within glioma.

METHODS

Hematoxylin and eosin (H&E) and immunohistochemical (IHC) staining were applied for histopathological examination. The protein levels of LDHA, transporter isoform 1 (GLUT1), hexokinase 2 (HK2), phosphofructokinase (PFK) in target cells were detected by Immunoblotting. The predicted miR-9 binding to lncRNA Annexin A2 Pseudogene 2 (ANXA2P2) or the 3' untranslated region (UTR) of LDHA was verified using Luciferase reporter assay. Cell viability or apoptosis were examined by MTT assay or Flow cytometry. Intracellular glucose and Lactate levels were measured using glucose assay kit and lactate colorimetric assay kit.

RESULTS

The expression of ANXA2P2 showed to be dramatically upregulated within glioma tissue samples and cells. Knocking down ANXA2P2 within glioma cells significantly inhibited cell proliferation and aerobic glycolysis, as manifested as decreased lactate and increased glucose in culture medium, and downregulated protein levels of glycolysis markers, GLUT1, HK2, PFK, as well as LDHA. miR-9 was predicted to target both lncRNA ANXA2P2 and LDHA. The overexpression of miR-9 suppressed the cell proliferation and aerobic glycolysis of glioma cells. Notably, miR-9 could directly bind to LDHA 3'UTR to inhibit LDHA expression and decrease the protein levels of LDHA. ANXA2P2 competitively targeted miR-9, therefore counteracting miR-9-mediated repression on LDHA. Within tissues, miR-9 exhibited a negative correlation with ANXA2P2 and LDHA, respectively, whereas ANXA2P2 and LDHA exhibited a positive correlation with each other.

CONCLUSIONS

In conclusion, ANXA2P2/miR-9/LDHA axis modulates the aerobic glycolysis progression in glioma cells, therefore affecting glioma cell proliferation.

A Potential Mechanism of Temozolomide Resistance in Glioma-Ferroptosis

Temozolomide (TMZ) is the first-line chemotherapy drug that has been used to treat glioma for over a decade, but the benefits are limited by half of the treated patients who acquired resistance. Studies have shown that glioma TMZ resistance is a complex process with multiple factors, which has not been fully elucidated. Ferroptosis, which is a new type of cell death discovered in recent years, has been reported to play an important role in tumor drug resistance. The present study reviews the relationship between ferroptosis and glioma TMZ resistance, and highlights the role of ferroptosis in glioma TMZ resistance. Finally, the investigators discussed the future orientation for ferroptosis in glioma TMZ resistance, in order to promote the clinical use of ferroptosis induction in glioma treatment.

Knockdown of Tousled‑like kinase 1 inhibits survival of glioblastoma multiforme cells

Glioblastoma multiforme (GBM) is an aggressive type of brain tumour that commonly exhibits resistance to treatment. The tumour is highly heterogenous and complex kinomic alterations have been reported leading to dysregulation of signalling pathways. The present study aimed to investigate the novel kinome pathways and to identify potential therapeutic targets in GBM. Meta‑analysis using Oncomine identified 113 upregulated kinases in GBM. RNAi screening was performed on identified kinases using ON‑TARGETplus siRNA library on LN18 and U87MG. Tousled‑like kinase 1 (TLK1), which is a serine/threonine kinase was identified as a potential hit. In vitro functional validation was performed as the role of TLK1 in GBM is unknown. TLK1 knockdown in GBM cells significantly decreased cell viability, clonogenicity, proliferation and induced apoptosis. TLK1 knockdown also chemosensitised the GBM cells to the sublethal dose of temozolomide. The downstream pathways of TLK1 were examined using microarray analysis, which identified the involvement of DNA replication, cell cycle and focal adhesion signalling pathways. In vivo validation of the subcutaneous xenografts of stably transfected sh‑TLK1 U87MG cells demonstrated significantly decreased tumour growth in female BALB/c nude mice. Together, these results suggested that TLK1 may serve a role in GBM survival and may serve as a potential target for glioma.

Breast Cancer Patient with Li-Fraumeni Syndrome: A Case Report Highlighting the Importance of Multidisciplinary Management

Germline mutations in TP53, a tumor suppressor gene, are involved in the development of Li-Fraumeni syndrome, a rare disorder that predisposes carriers to multiple tumors. TP53 mutations have been associated with resistance to treatment and poor prognosis. A young female with the pathogenic germline TP53 mutation c.844C > T (p.R282W) was diagnosed with two metachronous breast tumors, one HER2-negative and the other HER2-positive. She was later diagnosed with synchronous glioblastoma, epidermal growth factor receptor-mutated lung adenocarcinoma, and HER2-negative breast cancer metastases. The patient was treated with local therapies, including brain surgery and radiotherapy, lung surgery, and a bilateral mastectomy, as well as with targeted systemic treatment. She proved to be highly sensitive to systemic therapy, and 13 years after the initial diagnosis of breast cancer and 6 years after the diagnosis of the two new primary tumors and recurrence of a prior cancer, she is alive with an excellent performance status. This surprising positive evolution may well be partly due to the pronged multidisciplinary approach to managing her disease and her extraordinary response to treatment: the lung adenocarcinoma showed excellent response to erlotinib; the breast cancer responded extremely well to eribulin and pegylated liposomal doxorubicin; and the glioblastoma has remained in response to surgery and radiotherapy. Despite harboring a TP53 mutation and having multiple tumors, this patient has shown an unexpectedly favorable evolution. The coordinated participation of a multidisciplinary team and the patient's own extraordinarily high sensitivity to systemic treatment played a major role in this evolution.

Downregulation of SNRPG induces cell cycle arrest and sensitizes human glioblastoma cells to temozolomide by targeting Myc through a p53-dependent signaling pathway

Objective: Temozolomide (TMZ) is commonly used for glioblastoma multiforme (GBM) chemotherapy. However, drug resistance limits its therapeutic effect in GBM treatment. RNA-binding proteins (RBPs) have vital roles in posttranscriptional events. While disturbance of RBP-RNA network activity is potentially associated with cancer development, the precise mechanisms are not fully known. The SNRPG gene, encoding small nuclear ribonucleoprotein polypeptide G, was recently found to be related to cancer incidence, but its exact function has yet to be elucidated. Methods:SNRPG knockdown was achieved via short hairpin RNAs. Gene expression profiling and Western blot analyses were used to identify potential glioma cell growth signaling pathways affected by SNRPG. Xenograft tumors were examined to determine the carcinogenic effects of SNRPG on glioma tissues. Results: The SNRPG-mediated inhibitory effect on glioma cells might be due to the targeted prevention of Myc and p53. In addition, the effects of SNRPG loss on p53 levels and cell cycle progression were found to be Myc-dependent. Furthermore, SNRPG was increased in TMZ-resistant GBM cells, and downregulation of SNRPG potentially sensitized resistant cells to TMZ, suggesting that SNRPG deficiency decreases the chemoresistance of GBM cells to TMZ via the p53 signaling pathway. Our data confirmed that SNRPG suppression sensitizes GBM cells to TMZ by targeting Myc via the p53 signaling cascade. Conclusions: These results indicated that SNRPG is a probable molecular target of GBM and suggested that suppressing SNRPG in resistant GBM cells might be a substantially beneficial method for overcoming essential drug resistance.

Longitudinal assessment of tumor development using cancer avatars derived from genetically engineered pluripotent stem cells

Many cellular models aimed at elucidating cancer biology do not recapitulate pathobiology including tumor heterogeneity, an inherent feature of cancer that underlies treatment resistance. Here we introduce a cancer modeling paradigm using genetically engineered human pluripotent stem cells (hiPSCs) that captures authentic cancer pathobiology. Orthotopic engraftment of the neural progenitor cells derived from hiPSCs that have been genome-edited to contain tumor-associated genetic driver mutations revealed by The Cancer Genome Atlas project for glioblastoma (GBM) results in formation of high-grade gliomas. Similar to patient-derived GBM, these models harbor inter-tumor heterogeneity resembling different GBM molecular subtypes, intra-tumor heterogeneity, and extrachromosomal DNA amplification. Re-engraftment of these primary tumor neurospheres generates secondary tumors with features characteristic of patient samples and present mutation-dependent patterns of tumor evolution. These cancer avatar models provide a platform for comprehensive longitudinal assessment of human tumor development as governed by molecular subtype mutations and lineage-restricted differentiation.

Glioblastoma invasion and NMDA receptors: A novel prospect

PURPOSE

Glioblastoma cells create glutamate-rich tumor microenvironment, which initiates activation of ion channels and modulates downstream intracellular signaling. N-methyl-D-aspartate receptors (NMDARs; a type of glutamate receptors) have a high affinity for glutamate. The role of NMDAR activation on invasion of glioblastoma cells and the crosstalk with α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) is yet to be explored.

MAIN METHODS

LN18, U251MG, and patient-derived glioblastoma cells were stimulated with NMDA to activate NMDAR glutamate receptors. The role of NMDAR activation on invasion and migration and its crosstalk with AMPAR were evaluated. Invasion and migration of glioblastoma cells were investigated by in vitro trans-well Matrigel invasion and trans-well migration assays, respectively. Expression of NMDARs and AMPARs at transcript level was evaluated by quantitative real-time polymerase chain reaction.

RESULTS

We determined that NMDA stimulation leads to enhanced invasion in LN18, U251MG, and patient-derived glioblastoma cells, whereas inhibition of NMDAR using MK-801, a non-competitive antagonist of the NMDAR, significantly decreased the invasive capacity. Concordant with these findings, migration was significantly augmented by NMDAR in both cell lines. Furthermore, NMDA stimulation upregulated the expression of GluN2 and GluA1 subunits at the transcript level.

CONCLUSIONS

This study demonstrated the previously unexplored role of NMDAR in invasion of glioblastoma cells. Furthermore, the expression of the GluN2 subunit of NMDAR and the differential overexpression of the GluA1 subunit of AMPAR in both cell lines provide a plausible rationale of crosstalk between these calcium-permeable subunits in the glutamate-rich microenvironment of glioblastoma.

TNF-α mediated MEK-ERK signaling in invasion with putative network involving NF-κB and STAT-6: a new perspective in glioma

Glioblastoma is the most common malignant primary brain tumor with poor prognosis. Invasion involves pro-inflammatory cytokines and major signaling hubs. Tumor necrosis factor-α (TNF-α) acts as a master switch in establishing an intricate link between inflammation and cancer. The present study attempted to explore the possible implication of MAPK extracellular signaling-regulated kinase kinase (MEK)-extracellular signaling-regulated kinase (ERK) signaling pathway and expression of nuclear factor-κB (NF-κB), signal transducers and activators of transcription-6 (STAT-6), ERK, and phosphorylated-ERK (p-ERK) signaling proteins in TNF-α microenvironment. U0126 and PD98059 were used to inhibit the MEK-ERK1/2 pathway. TNF-α stimulation enhanced invasion in U87MG, U251MG and patient-derived primary glioma cells, whereas cell viability was not altered. Matrix metalloproteinase-2 (MMP-2) activity was increased only in U251MG glioma cells. These data suggest that TNF-α microenvironment plays an important role in the invasion of U251MG, U87MG, and patient-derived primary glioma cells, without any cytotoxic effect. The MMP-2 activity is differentially regulated by TNF-α stimulation in these cells. TNF-α stimulation upregulated the protein expression of ERK-1, ERK-2 and also increased the level of p-ERK1/2. TNF-α stimulation further upregulated the expression of NF-κB1, STAT-6 in tandem with Ras-MEK signaling system in U87MG cells, which emphasized the possible involvement of these signaling hubs in the glioma microenvironment. MEK-ERK inhibitors significantly attenuated the invasion of U87MG cells mediated by the TNF-α stimulation, probably through their inhibitory impact on p-ERK1/2 and ERK-2. This study provides the possible rationale of invasion by glioma cells in a TNF-α-induced pro-inflammatory milieu, which involves direct role of MEK-ERK signaling, with possible implication of NF-κB and STAT-6.

Antimicrobial Peptide TP4 Induces ROS-Mediated Necrosis by Triggering Mitochondrial Dysfunction in Wild-Type and Mutant p53 Glioblastoma Cells

Antimicrobial peptide tilapia piscidin 4 (TP4) from Oreochromis niloticus exhibits potent bactericidal and anti-tumorigenic effects. In a variety of cancers, the mutation status of p53 is a decisive factor for therapeutic sensitivity. Therefore, we investigated the impact of p53 status on TP4-induced cytotoxicity in glioblastoma cell lines and the molecular mechanisms that govern cytotoxic effects. Both U87MG (wild-type/WT p53) and U251 (mutant p53) glioblastoma cell lines were sensitive to TP4-induced cytotoxicity. The necrosis inhibitors Necrostatin-1 and GSK’872 attenuated TP4-induced cytotoxicity, and TP4 treatment induced the release of cyclophilin A, a biomarker of necrosis. Moreover, TP4 induced mitochondrial hyperpolarization and dysfunction, which preceded the elevation of intracellular reactive oxygen species, DNA damage, and necrotic cell death in both U87MG and U251 glioblastoma cells. p38 was also activated by TP4, but did not contribute to cytotoxicity. SB202190, a specific p38 inhibitor, enhanced TP4-induced oxidative stress, mitochondrial dysfunction, and cytotoxicity, suggesting a protective role of p38. Furthermore, TP4-induced cytotoxicity, oxidative stress, phosphorylation of p38, and DNA damage were all attenuated by the mitochondrial-targeted reactive oxygen species (ROS) scavenger MitoTEMPO, or the reactive oxygen species scavenger N-acetyl-L-cysteine. Based on these data, we conclude that TP4 induces necrosis in both WT and mutant p53 glioblastoma cells through a mitochondrial ROS-dependent pathway.

YB-1 modulates the drug resistance of glioma cells by activation of MDM2/p53 pathway

Background

Y-box-binding protein-1 (YB-1) is aberrantly expressed in a variety of cancers. However, the biological functional role of YB-1 in glioma is not yet clear.

Methods

The expression of MDM2 and YB-1 was analyzed by real time PCR. Overexpression and knockdown of YB-1 in glioma cells were created by transfection of pcDNA-YB-1 and siRNA against YB-1, respectively. Cell viability was performed by CCK8 assay.

Results

Our findings showed that glioma tissues had higher expressions of YB-1 than that in cancer-free tissues in 54 glioma patients, which were also positively correlated with Murine MDM2 expression. Overexpression of YB-1 or MDM2 renders a drug resistance feature in glioma cell exposed to temozolomide (TMZ), by directly targeting p53. Genetic or chemical inhibition of MDM2 significantly blocked YB-1-modulated response of glioma cells to TMZ. Moreover, inhibition of YB-1 or MDM2 reduced glioma cells metastasis and mortality in mice.

Conclusion

YB-1 facilitates the resistance of glioma cells to TMZ by direct activation of MDM2/p53 signaling and represents a promising molecular target for glioma treatment.

Towards identifying potent new hits for glioblastoma

Glioblastoma is a devastating disease of the brain and is the most common malignant primary brain tumour in adults. The prognosis for patients is very poor with median time of survival after diagnosis measured in months, due in part to the tumours being highly aggressive and often resistant to chemotherapies. Alongside the ongoing research to identify key factors involved in tumour progression in glioblastoma, medicinal chemistry approaches must also be used in order to rapidly establish new and better treatments for brain tumour patients. Using a computational similarity search of the ZINC database, alongside traditional analogue design by medicinal chemistry intuition to improve the breadth of chemical space under consideration, six new hit compounds (14, 16, 18, 19, 20 and 22) were identified possessing low micromolar activity against both established cell lines (U87MG and U251MG) and patient-derived cell cultures (IN1472, IN1528 and IN1760). Each of these scaffolds provides a new platform for future development of a new therapy in this area, with particular promise shown against glioblastoma subtypes that are resistant to conventional chemotherapeutic agents.

Caffeine Sensitizes U87-MG Human Glioblastoma Cells to Temozolomide through Mitotic Catastrophe by Impeding G2 Arrest

Temozolomide (TMZ) is the first-line chemotherapeutic agent in the treatment of glioblastoma multiforme (GBM). Despite its cytotoxic effect, TMZ also induces cell cycle arrest that may lead to the development of chemoresistance and eventual tumor recurrence. Caffeine, a widely consumed neurostimulant, shows anticancer activities and is reported to work synergistically with cisplatin and camptothecin. The present study aimed to investigate the effects and the mechanisms of action of caffeine used in combination with TMZ in U87-MG GBM cells. As anticipated, TMZ caused DNA damage mediated by the ATM/p53/p21 signaling pathway and induced significant G2 delay. Concurrent treatment with caffeine repressed proliferation and lowered clonogenic capacity on MTT and colony formation assays, respectively. Mechanistic study showed that coadministration of caffeine and TMZ suppressed the phosphorylation of ATM and p53 and downregulated p21 expression, thus releasing DNA-damaged cells from G2 arrest into premature mitosis. Cell cycle analysis demonstrated that the proportion of cells arrested in G2 phase decreased when caffeine was administered together with TMZ; at the same time, the amount of cells with micronucleation and multipolar spindle poles increased, indicative of enhanced mitotic cell death. Pretreatment of cells with caffeine further enhanced mitotic catastrophe development in combined treatment and sensitized cells to apoptosis when followed by TMZ alone. In conclusion, our study demonstrated that caffeine enhanced the efficacy of TMZ through mitotic cell death by impeding ATM/p53/p21-mediated G2 arrest.

GSK3β‑mediated Ser156 phosphorylation modulates a BH3‑like domain in BCL2L12 during TMZ‑induced apoptosis and autophagy in glioma cells

BH3 domains, classified initially as BCL2 homology domains, participate in both apoptosis and autophagy. Beclin-1 contains a BH3 domain, which is required for binding to antiapoptotic BCL2 homologs and BCL2-mediated inhibition of autophagy. BCL2-like 12 (BCL2L12) also harbors a BH3-like domain, which is 12 residues long and contains a LXXXAE/D motif. In a yeast two-hybrid system performed in the present study, BCL2L12 shared similar binding partnerships to antiapoptotic BCL2 homologs, such as Beclin-1. In addition, this BH3-like domain was involved in antiapoptosis and drug-induced autophagy in glioma cell lines. Mutations in S156 and hydrophobic L213 to alanine counteracted the antiapoptotic properties of BCL2L12 and downregulated the activation of microtubule associated protein 1 light chain 3B (LC3B), autophagy-related (ATG)12-ATG5 conjugates and Beclin-1, compared with a BCL2L12 wild-type group. Molecular dynamics simulations revealed that phosphorylation at Ser156 of BCL2L12 (within α-6 and α-7 helices) influenced the BH3-like domain conformation (α-9 helix), indicating that glycogen synthase kinase (GSK) 3β-mediated Ser156 phosphorylation modulated a BH3-like domain in BCL2L12. Altogether, the present findings indicated that BCL2L12 may participate in anti-apoptosis and autophagy via a BH3-like domain and GSK3β-mediated phosphorylation at Ser156. Furthermore, blockade of temozolomide (TMZ)-induced autophagy by 3-methyladenine (3-MA) resulted in enhanced activation of apoptotic markers, as well as tumor suppresor protein p53 (p53) expression in U87MG cells. The present results suggested that p53 and O6-methylguanine DNA methyltransferase activation, and BCL2, BCL-extra large, Beclin-1 and BCL2L12 expression may be used as a detection panel to determine which patients can benefit from TMZ and ABT-737 combination treatment.

The role of p53 in cancer drug resistance and targeted chemotherapy

Cancer has long been a grievous disease complicated by innumerable players aggravating its cure. Many clinical studies demonstrated the prognostic relevance of the tumor suppressor protein p53 for many human tumor types. Overexpression of mutated p53 with reduced or abolished function is often connected to resistance to standard medications, including cisplatin, alkylating agents (temozolomide), anthracyclines, (doxorubicin), antimetabolites (gemcitabine), antiestrogenes (tamoxifen) and EGFR-inhibitors (cetuximab). Such mutations in the TP53 gene are often accompanied by changes in the conformation of the p53 protein. Small molecules that restore the wild-type conformation of p53 and, consequently, rebuild its proper function have been identified. These promising agents include PRIMA-1, MIRA-1, and several derivatives of the thiosemicarbazone family. In addition to mutations in p53 itself, p53 activity may be also be impaired due to alterations in p53s regulating proteins such as MDM2. MDM2 functions as primary cellular p53 inhibitor and deregulation of the MDM2/p53-balance has serious consequences. MDM2 alterations often result in its overexpression and therefore promote inhibition of p53 activity. To deal with this problem, a judicious approach is to employ MDM2 inhibitors. Several promising MDM2 inhibitors have been described such as nutlins, benzodiazepinediones or spiro-oxindoles as well as novel compound classes such as xanthone derivatives and trisubstituted aminothiophenes. Furthermore, even naturally derived inhibitor compounds such as a-mangostin, gambogic acid and siladenoserinols have been discovered. In this review, we discuss in detail such small molecules that play a pertinent role in affecting the p53-MDM2 signaling axis and analyze their potential as cancer chemotherapeutics.

Biomarkers and therapeutic advances in glioblastoma multiforme

Glioblastoma multiforme (GBM) is a malignant tumor within the brain. Generally classified as primary and secondary with several different subtypes, ample molecular biomarkers have risen throughout the years which have garnered the attention of researchers. The advancements in genomics and proteomics have allowed researchers to gather prominent molecular biomarkers. All these biomarkers are gathered by means of biopsy or bodily fluid sample collection and are quantitatively analyzed by polymerase chain reaction coupled with other computational technologies. This review highlights the significance, regulation and prevalence of molecular biomarkers such as O⁶ -methylguanine-DNA methyltransferase, epidermal growth factor receptor vIII, isocitrate dehydrogenase mutation and several others which expressed differently in different types and molecular subtypes of GBM. The discoveries and roles of GBM-specific microRNAs including miR-21 and miR-10b as biomarkers with promising prognostic values were also delineated. The role and mechanism of biomarkers in GBM tumorigenesis are essential in the development of therapy for patients suffering from the disease itself. Thus, this review also discusses the mechanisms, effects and limitations of therapy such as temozolomide, viral gene transfer, biomarker-based vaccines or even engineered T cells for more specific responses. Biomarkers have displayed a high value and could eventually be utilized as drug targets. It is hoped that by combining different aspects of the disease which present with different biomarkers could lead to the development of a robust, effective and innovative take on GBM therapy.

GADD45A plays a protective role against temozolomide treatment in glioblastoma cells

Glioblastoma multiforme (GBM) is one of the most aggressive cancers. Despite recent advances in multimodal therapies, high-grade glioma remains fatal. Temozolomide (TMZ) is an alkylating agent used worldwide for the clinical treatment of GBM; however, the innate and acquired resistance of GBM limits its application. Here, we found that TMZ inhibited the proliferation and induced the G2/M arrest of GBM cells. Therefore, we performed microarrays to identify the cell cycle- and apoptosis-related genes affected by TMZ. Notably, GADD45A was found to be up-regulated by TMZ in both cell cycle and apoptosis arrays. Furthermore, GADD45A knockdown (GADD45A^kd) enhanced the cell growth arrest and cell death induced by TMZ, even in natural (T98) and adapted (TR-U373) TMZ-resistant cells. Interestingly, GADD45A^kd decreased the expression of O⁶-methylguanine-DNA methyltransferase (MGMT) in TMZ-resistant cells (T98 and TR-U373). In MGMT-deficient/TMZ-sensitive cells (U87 and U373), GADD45A^kd decreased TMZ-induced TP53 expression. Thus, in this study, we investigated the genes influenced by TMZ that were important in GBM therapy, and revealed that GADD45A plays a protective role against TMZ treatment which may through TP53-dependent and MGMT-dependent pathway in TMZ-sensitive and TMZ-resistant GBM, respectively. This protective role of GADD45A against TMZ treatment may provide a new therapeutic strategy for GBM treatment.

The Role of Neurotrophin Signaling in Gliomagenesis: A Focus on the p75 Neurotrophin Receptor (p75NTR/CD271)

The p75 neurotrophin receptor (p75^NTR, a.k.a. CD271), a transmembrane glycoprotein and a member of the tumor necrosis family (TNF) of receptors, was originally identified as a nerve growth factor receptor in the mid-1980s. While p75^NTR is recognized to have important roles during neural development, its presence in both neural and nonneural tissues clearly supports the potential to mediate a broad range of functions depending on cellular context. Using an unbiased in vivo selection paradigm for genes underlying the invasive behavior of glioma, a critical characteristic that contributes to poor clinical outcome for glioma patients, we identified p75^NTR as a central regulator of glioma invasion. Herein we review the expanding role that p75^NTR plays in glioma progression with an emphasis on how p75^NTR may contribute to the treatment refractory nature of glioma. Based on the observation that p75^NTR is expressed and functional in two critical glioma disease reservoirs, namely, the highly infiltrative cells that evade surgical resection, and the radiation- and chemotherapy-resistant brain tumor-initiating cells (also referred to as brain tumor stem cells), we propose that p75^NTR and its myriad of downstream signaling effectors represent rationale therapeutic targets for this devastating disease. Lastly, we provide the provocative hypothesis that, in addition to the well-documented cell autonomous signaling functions, the neurotrophins, and their respective receptors, contribute in a cell nonautonomous manner to drive the complex cellular and molecular composition of the brain tumor microenvironment, an environment that fuels tumorigenesis.

Apoptosis induced by temozolomide and nimustine in glioblastoma cells is supported by JNK/c-Jun-mediated induction of the BH3-only protein BIM

The outcome of cancer therapy strongly depends on the complex network of cell signaling pathways, including transcription factor activation following drug exposure. Here we assessed whether and how the MAP kinase (MAPK) cascade and its downstream target, the transcription factor AP-1, influence the sensitivity of malignant glioma cells to the anticancer drugs temozolomide (TMZ) and nimustine (ACNU). Both drugs induce apoptosis in glioma cells at late times following treatment. Activation of the MAPK cascade precedes apoptosis, as shown by phosphorylation of Jun kinase (JNK) and c-Jun, a main component of AP-1. Pharmacological inhibition and siRNA mediated knockdown of JNK and c-Jun reduced the level of apoptosis in LN-229 glioma cells treated with TMZ or ACNU. Analyzing the underlying molecular mechanism, we identified the pro-apoptotic gene BIM as a critical target of AP-1, which is upregulated following TMZ and ACNU. Importantly, shRNA mediated downregulation of BIM in the malignant glioma cell lines LN-229 and U87MG led to an attenuated cleavage of caspase-9 and, consequently, reduced the level of apoptosis following TMZ and ACNU treatment. Overall, we identified JNK/c-Jun activation and BIM induction as a late pro-apoptotic response of glioma cells treated with alkylating anticancer drugs.

Temozolomide resistance in glioblastoma multiforme

Temozolomide (TMZ) is an oral alkylating agent used to treat glioblastoma multiforme (GBM) and astrocytomas. However, at least 50% of TMZ treated patients do not respond to TMZ. This is due primarily to the over-expression of O⁶-methylguanine methyltransferase (MGMT) and/or lack of a DNA repair pathway in GBM cells. Multiple GBM cell lines are known to contain TMZ resistant cells and several acquired TMZ resistant GBM cell lines have been developed for use in experiments designed to define the mechanism of TMZ resistance and the testing of potential therapeutics. However, the characteristics of intrinsic and adaptive TMZ resistant GBM cells have not been systemically compared. This article reviews the characteristics and mechanisms of TMZ resistance in natural and adapted TMZ resistant GBM cell lines. It also summarizes potential treatment options for TMZ resistant GBMs.

A Systematic Comparison Identifies an ATP-Based Viability Assay as Most Suitable Read-Out for Drug Screening in Glioma Stem-Like Cells

Serum-free culture methods for patient-derived primary glioma cultures, selecting for glioma stem-like cells (GSCs), are becoming the gold standard in neurooncology research. These GSCs can be implemented in drug screens to detect patient-specific responses, potentially bridging the translational gap to personalized medicine. Since numerous compounds are available, a rapid and reliable readout for drug efficacies is required. This can be done using approaches that measure viability, confluency, cytotoxicity, or apoptosis. To determine which assay is best suitable for drug screening, 10 different assays were systematically tested on established glioma cell lines and validated on a panel of GSCs. General applicability was assessed using distinct treatment modalities, being temozolomide, radiation, rapamycin, and the oncolytic adenovirus Delta24-RGD. The apoptosis and cytotoxicity assays did not unequivocally detect responses and were excluded from further testing. The NADH- and ATP-based viability assays revealed comparable readout for all treatments; however, the latter had smaller standard deviations and direct readout. Importantly, drugs that interfere with cell metabolism require alternative techniques such as confluency monitoring to accurately measure treatment effects. Taken together, our data suggest that the combination of ATP luminescence assays with confluency monitoring provides the most specific and reproducible readout for drug screening on primary GSCs.

Expression and Prognostic Significance of p53 in Glioma Patients: A Meta-analysis

Glioma is a brain tumor deriving from the neoplastic glial cells or neuroglia. Due to its resistance to anticancer drugs and different disease progress of individuals, patients with high-grade glioma are difficult to completely cure, leading to a poor prognosis and low overall survival. Therefore, there is an urgent need to look for prognostic and diagnostic indicators that can predict glioma grades. P53 is one of the widely studied biomarkers in human glioma. The purpose of this study was to comprehensively evaluate the significance of p53 expression in glioma grades and overall survival. We searched commonly used electronic databases to retrieve related articles of p53 expression in glioma. Overall, a total of 21 studies including 1322 glioma patients were finally screened out. We observed that the frequency of p53 immuno-positivity was higher in high-grade patients than that in low-grade category (63.8 vs. 41.6 %), and our statistic analysis indicated that p53 expression was associated with pathological grade of glioma (OR 2.93, 95 % CI 1.87-4.60, P < 0.00001). This significant correction was also found in 1-, 3- and 5-year overall survival. However, no positive relationship was found between age, sex, tumor size and p53 expression in patients with glioma. In conclusion, our results suggested that p53 immunohistochemical expression might have an effective usefulness in predicting the prognosis in patients with glioma.

Study on the therapeutic effect of neural progenitor cells in mice of a glioma murine model

Glioma is a common malignacy of the brain that affects elderly patients in particular. Despite treatment, however, the survival rate is 12 months. The aim of the present study was to examine the therapeutic effect of neural progenitor cells (NPCs) on a glioma murine model, and to determine the possible mechanism of action. A glioma murine model was constructed and the tumor volume and tumor growth rate were measured. The therapeutic effect of cell injection on the glioma mouse model mice was confirmed. The quantitative polymerase chain reaction method was used to detect the expression of proto-oncogene and tumor suppressor gene. Intracranial injection of NPCs was performed to determine cell apoptosis. Preliminary results showed the mechanism of cell therapy effect at the transcription and cellular level. Compared with the model group, the tumor volume of the mice of the cell therapy group was significantly reduced from the 6th to 8th week, and the tumor growth rate was downregulated. The mechanism of action identified that NPCs regulate gene expression in tumor tissues, increase the expression of tumor suppressor gene, downregulate the gene expression of tumor cells, and reverse the proto-oncogene and imbalance of gene expression in gliomas. In conclusion, the new type of cell injection method can regulate the proto-oncogene of tumor tissue and tumor suppressor gene, improve the function phenotype of the cell, and effectively improve the clinical symptoms of mice with gliomas.

M011L-deficient oncolytic myxoma virus induces apoptosis in brain tumor-initiating cells and enhances survival in a novel immunocompetent mouse model of glioblastoma

BACKGROUND

Myxoma virus (MYXV) is a promising oncolytic agent and is highly effective against immortalized glioma cells but less effective against brain tumor initiating cells (BTICs), which are believed to mediate glioma development/recurrence. MYXV encodes various proteins to attenuate host cell apoptosis, including an antiapoptotic Bcl-2 homologue known as M011L. Such proteins may limit the ability of MYXV to kill BTICs, which have heightened resistance to apoptosis. We hypothesized that infecting BTICs with an M011L-deficient MYXV construct would overcome BTIC resistance to MYXV.

METHODS

We used patient-derived BTICs to evaluate the efficacy of M011L knockout virus (vMyx-M011L-KO) versus wild-type MYXV (vMyx-WT) and characterized the mechanism of virus-induced cell death in vitro. To extend our findings in a novel immunocompetent animal model, we derived, cultured, and characterized a C57Bl/6J murine BTIC (mBTIC0309) from a spontaneous murine glioma and evaluated vMyx-M011L-KO efficacy with and without temozolomide (TMZ) in mBTIC0309-bearing mice.

RESULTS

We demonstrated that vMyx-M011L-KO induces apoptosis in BTICs, dramatically increasing sensitivity to the virus. vMyx-WT failed to induce apoptosis as M011L protein prevented Bax activation and cytochrome c release. In vivo, intracranial implantation of mBTIC0309 generated tumors that closely recapitulated the pathological and molecular profile of human gliomas. Treatment of tumor-bearing mice with vMyx-M011L-KO significantly prolonged survival in immunocompetent-but not immunodeficient-mouse models, an effect that is significantly enhanced in combination with TMZ.

CONCLUSIONS

Our data suggest that vMyx-M011L-KO is an effective, well-tolerated, proapoptotic oncolytic virus and a strong candidate for clinical translation.

A practical review of prognostic correlations of molecular biomarkers in glioblastoma

Despite extensive efforts in research and therapeutics, achieving longer survival for patients with glioblastoma (GBM) remains a formidable challenge. Furthermore, because of rapid advances in the scientific understanding of GBM, communication with patients regarding the explanations and implications of genetic and molecular markers can be difficult. Understanding the important biomarkers that play a role in GBM pathogenesis may also help clinicians in educating patients about prognosis, potential clinical trials, and monitoring response to treatments. This article aims to provide an up-to-date review that can be discussed with patients regarding common molecular markers, namely O-6-methylguanine-DNA methyltransferase (MGMT), isocitrate dehydrogenase 1 and 2 (IDH1/2), p53, epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFR), phosphatase and tensin homolog (PTEN), phosphoinositide 3-kinase (PI3K), and 1p/19q. The importance of the distinction between a prognostic and a predictive biomarker as well as clinical trials regarding these markers and their relevance to clinical practice are discussed.

Minor Changes in Expression of the Mismatch Repair Protein MSH2 Exert a Major Impact on Glioblastoma Response to Temozolomide

Glioblastoma (GBM) is often treated with the cytotoxic drug temozolomide, but the disease inevitably recurs in a drug-resistant form after initial treatment. Here, we report that in GBM cells, even a modest decrease in the mismatch repair (MMR) components MSH2 and MSH6 have profound effects on temozolomide sensitivity. RNAi-mediated attenuation of MSH2 and MSH6 showed that such modest decreases provided an unexpectedly strong mechanism of temozolomide resistance. In a mouse xenograft model of human GBM, small changes in MSH2 were sufficient to suppress temozolomide-induced tumor regression. Using The Cancer Genome Atlas to analyze mRNA expression patterns in tumors from temozolomide-treated GBM patients, we found that MSH2 transcripts in primary GBM could predict patient responses to initial temozolomide therapy. In recurrent disease, the absence of microsatellite instability (the standard marker for MMR deficiency) suggests a lack of involvement of MMR in the resistant phenotype of recurrent disease. However, more recent studies reveal that decreased MMR protein levels occur often in recurrent GBM. In accordance with our findings, these reported decreases may constitute a mechanism by which GBM evades temozolomide sensitivity while maintaining microsatellite stability. Overall, our results highlight the powerful effects of MSH2 attenuation as a potent mediator of temozolomide resistance and argue that MMR activity offers a predictive marker for initial therapeutic response to temozolomide treatment.

Preclinical activity of combined HDAC and KDM1A inhibition in glioblastoma

BACKGROUND

Glioblastoma (GBM) is the most common and aggressive form of brain cancer. Our previous studies demonstrated that combined inhibition of HDAC and KDM1A increases apoptotic cell death in vitro. However, whether this combination also increases death of the glioma stem cell (GSC) population or has an effect in vivo is yet to be determined. Therefore, we evaluated the translational potential of combined HDAC and KDM1A inhibition on patient-derived GSCs and xenograft GBM mouse models. We also investigated the changes in transcriptional programing induced by the combination in an effort to understand the induced molecular mechanisms of GBM cell death.

METHODS

Patient-derived GSCs were treated with the combination of vorinostat, a pan-HDAC inhibitor, and tranylcypromine, a KDM1A inhibitor, and viability was measured. To characterize transcriptional profiles associated with cell death, we used RNA-Seq and validated gene changes by RT-qPCR and protein expression via Western blot. Apoptosis was measured using DNA fragmentation assays. Orthotopic xenograft studies were conducted to evaluate the effects of the combination on tumorigenesis and to validate gene changes in vivo.

RESULTS

The combination of vorinostat and tranylcypromine reduced GSC viability and displayed efficacy in the U87 xenograft model. Additionally, the combination led to changes in apoptosis-related genes, particularly TP53 and TP73 in vitro and in vivo.

CONCLUSIONS

These data support targeting HDACs and KDM1A in combination as a strategy for GBM and identifies TP53 and TP73 as being altered in response to treatment.

Cellular plasticity regulated cancer stem cell niche: a possible new mechanism of chemoresistance

The cancer stem cell (CSC) theory is an emerging concept that proposes a hierarchical nature of carcinogenesis, where a small number of tumor cells are capable of driving tumor growth. Despite many unanswered questions surrounding the cancer stem cell model, the hypothesis has rejuvenated hopes for formulating a novel therapeutic strategy for targeting the roots of cancer. This model predicts that cancer stem cells have the capacity to resist conventional radio- and chemotherapy and initiate disease recurrence. We recently investigated the mechanisms of chemoresistance in glioblastoma (GBM), the most common and aggressive adult human brain tumor. Exposure of patient derived glioma xenograft lines to a therapeutic dose of temolozolomide (TMZ), the most commonly used chemotherapy for patients with GBM, consistently increased the glioma stem cell (GSC) frequency over time. Lineage tracing analysis at the single sell level revealed unprecedented cellular plasticity within the glioma cells, allowing them to reprogram from a differentiated state to an undifferentiated CSC-like state. This reprogramming, mediated by cellular plasticity, is driven by TMZ-induced hypoxia inducible factors (HIFs), and provides a novel mechanism for chemoresistance acquisition. We herein discuss the possible role of temozolomide in regulating a cancer stem cell niche that supports GSC resistance, proliferation, and subsequent therapeutic relapse.

A nanoparticle carrying the p53 gene targets tumors including cancer stem cells, sensitizes glioblastoma to chemotherapy and improves survival

Temozolomide (TMZ)-resistance in glioblastoma multiforme (GBM) has been linked to upregulation of O(6)-methylguanine-DNA methyltransferase (MGMT). Wild-type (wt) p53 was previously shown to down-modulate MGMT. However, p53 therapy for GBM is limited by lack of efficient delivery across the blood brain barrier (BBB). We have developed a systemic nanodelivery platform (scL) for tumor-specific targeting (primary and metastatic), which is currently in multiple clinical trials. This self-assembling nanocomplex is formed by simple mixing of the components in a defined order and a specific ratio. Here, we demonstrate that scL crosses the BBB and efficiently targets GBM, as well as cancer stem cells (CSCs), which have been implicated in recurrence and treatment resistance in many human cancers. Moreover, systemic delivery of scL-p53 down-modulates MGMT and induces apoptosis in intracranial GBM xenografts. The combination of scL-p53 and TMZ increased the antitumor efficacy of TMZ with enhanced survival benefit in a mouse model of highly TMZ-resistant GBM. scL-p53 also sensitized both CSCs and bulk tumor cells to TMZ, increasing apoptosis. These results suggest that combining scL-p53 with standard TMZ treatment could be a more effective therapy for GBM.