Hypoxia-inducible factor-1 and associated upstream and downstream proteins in the pathophysiology and management of glioblastoma

Targeting Tumor Hypoxia with Nanoparticle-Based Therapies: Challenges, Opportunities, and Clinical Implications

Hypoxia is a crucial factor in tumor biology, affecting various solid tumors to different extents. Its influence spans both early and advanced stages of cancer, altering cellular functions and promoting resistance to therapy. Hypoxia reduces the effectiveness of radiotherapy, chemotherapy, and immunotherapy, making it a target for improving therapeutic outcomes. Despite extensive research, gaps persist, necessitating the exploration of new chemical and pharmacological interventions to modulate hypoxia-related pathways. This review discusses the complex pathways involved in hypoxia and the associated pharmacotherapies, highlighting the limitations of current treatments. It emphasizes the potential of nanoparticle-based platforms for delivering anti-hypoxic agents, particularly oxygen (O2), to the tumor microenvironment. Combining anti-hypoxic drugs with conventional cancer therapies shows promise in enhancing remission rates. The intricate relationship between hypoxia and tumor progression necessitates novel therapeutic strategies. Nanoparticle-based delivery systems can significantly improve cancer treatment efficacy by targeting hypoxia-associated pathways. The synergistic effects of combined therapies underscore the importance of multimodal approaches in overcoming hypoxia-mediated resistance. Continued research and innovation in this area hold great potential for advancing cancer therapy and improving patient outcomes.

Morphological and Molecular Biological Characteristics of Experimental Rat Glioblastoma Tissue Strains Induced by Different Carcinogenic Chemicals

Glioblastoma (GBM) is a highly aggressive human neoplasm with poor prognosis due to its malignancy and therapy resistance. To evaluate the efficacy of antitumor therapy, cell models are used most widely, but they are not as relevant to human GBMs as tissue models of gliomas, closely corresponding to human GBMs in cell heterogeneity. In this work, we compared three different tissue strains of rat GBM 101.8 (induced by DMBA), GBM 11-9-2, and GBM 14-4-5 (induced by ENU).

MATERIALS AND METHODS

We estimated different gene expressions by qPCR-RT and conducted Western blotting and histological and morphometric analysis of three different tissue strains of rat GBM.

RESULTS

GBM 101.8 was characterized by the shortest period of tumor growth and the greatest number of necroses and mitoses; overexpression of Abcb1, Sox2, Cdkn2a, Cyclin D, and Trp53; and downregulated expression of Vegfa, Pdgfra, and Pten; as well as a high level of HIF-1α protein content. GBM 11-9-2 and GBM 14-4-5 were relevant to low-grade gliomas and characterized by downregulated Mgmt expression; furthermore, a low content of CD133 protein was found in GBM 11-9-2.

CONCLUSIONS

GBM 101.8 is a reliable model for further investigation due to its similarity to high-grade human GBMs, while GBM 11-9-2 and GBM 14-4-5 correspond to Grade 2-3 gliomas.

Morphological and molecular-biological features of glioblastoma progression in tolerant and susceptible to hypoxia Wistar rats

Hypoxia is a major pathogenetic factor in many cancers. Individual resistance to suboptimal oxygen availability is subject to broad variation and its possible role in tumorigenesis remains underexplored. This study aimed at specific characterization of glioblastoma progression in male tolerant and susceptible to hypoxia Wistar rats. Hypoxia resistance was assessed by gasping time measurement in an 11,500 m altitude-equivalent hypobaric decompression chamber. Based on the outcome, the animals were assigned to three groups termed 'tolerant to hypoxia' (n = 13), 'normal', and 'susceptible to hypoxia' (n = 24). The 'normal' group was excluded from subsequent experiments. One month later, the animals underwent inoculation with rat glioblastoma 101.8 followed by monitoring of survival, body weight dynamics and neurological symptoms. The animals were sacrificed on post-inoculation days 11 (subgroup 1) and 15 (subgroup 2). Relative vessels number, necrosis areas and Ki-67 index were assessed microscopically; tumor volumes were determined by 3D reconstruction from histological images; serum levels of HIF-1α, IL-1β, and TNFα were determined by ELISA. None of the tolerant to hypoxia animals died of the disease during observation period, cf. 85% survival on day 11 and 55% survival on day 15 in the susceptible group. On day 11, proliferative activity of the tumors in the tolerant animals was higher compared with the susceptible group. On day 15, proliferative activity, necrosis area and volume of the tumors in the tolerant to hypoxia animals were higher compared with the susceptible group. ELISA revealed no dynamics in TNFα levels, elevated levels of IL-1β in the susceptible animals on day 15 in comparison with day 11 and tolerant ones. Moreover, there were elevated levels of HIF-1α in the tolerant animals on day 15 in comparison with day 11. Thus, the proliferative activity of glioblastoma cells and the content of HIF-1α were higher in tolerant to hypoxia rats, but the mortality associated with the tumor process and IL-1β level in them were lower than in susceptible animals. Specific features of glioblastoma 101.8 progression in tolerant and susceptible to hypoxia rats, including survival, tumor growth rates and IL-1β level, can become the basis of new personalized approaches for cancer diseases treatment in accordance to individual hypoxia resistance.

HIF: a master regulator of nutrient availability and metabolic cross-talk in the tumor microenvironment

A role for hypoxia-inducible factors (HIFs) in hypoxia-dependent regulation of tumor cell metabolism has been thoroughly investigated and covered in reviews. However, there is limited information available regarding HIF-dependent regulation of nutrient fates in tumor and stromal cells. Tumor and stromal cells may generate nutrients necessary for function (metabolic symbiosis) or deplete nutrients resulting in possible competition between tumor cells and immune cells, a result of altered nutrient fates. HIF and nutrients in the tumor microenvironment (TME) affect stromal and immune cell metabolism in addition to intrinsic tumor cell metabolism. HIF-dependent metabolic regulation will inevitably result in the accumulation or depletion of essential metabolites in the TME. In response, various cell types in the TME will respond to these hypoxia-dependent alterations by activating HIF-dependent transcription to alter nutrient import, export, and utilization. In recent years, the concept of metabolic competition has been proposed for critical substrates, including glucose, lactate, glutamine, arginine, and tryptophan. In this review, we discuss how HIF-mediated mechanisms control nutrient sensing and availability in the TME, the competition for nutrients, and the metabolic cross-talk between tumor and stromal cells.

Intersections of Ubiquitin-Proteosome System and Autophagy in Promoting Growth of Glioblastoma Multiforme: Challenges and Opportunities

Glioblastoma multiforme (GBM) is a brain tumor notorious for its propensity to recur after the standard treatments of surgical resection, ionizing radiation (IR), and temozolomide (TMZ). Combined with the acquired resistance to standard treatments and recurrence, GBM is an especially deadly malignancy with hardly any worthwhile treatment options. The treatment resistance of GBM is influenced, in large part, by the contributions from two main degradative pathways in eukaryotic cells: ubiquitin-proteasome system (UPS) and autophagy. These two systems influence GBM cell survival by removing and recycling cellular components that have been damaged by treatments, as well as by modulating metabolism and selective degradation of components of cell survival or cell death pathways. There has recently been a large amount of interest in potential cancer therapies involving modulation of UPS or autophagy pathways. There is significant crosstalk between the two systems that pose therapeutic challenges, including utilization of ubiquitin signaling, the degradation of components of one system by the other, and compensatory activation of autophagy in the case of proteasome inhibition for GBM cell survival and proliferation. There are several important regulatory nodes which have functions affecting both systems. There are various molecular components at the intersections of UPS and autophagy pathways that pose challenges but also show some new therapeutic opportunities for GBM. This review article aims to provide an overview of the recent advancements in research regarding the intersections of UPS and autophagy with relevance to finding novel GBM treatment opportunities, especially for combating GBM treatment resistance.

Growth differentiation factor-15 overexpression promotes cell proliferation and predicts poor prognosis in cerebral lower-grade gliomas correlated with hypoxia and glycolysis signature

AIMS

Growth differentiation factor-15 (GDF15) plays complex and controversial roles in cancer. In this study, the prognostic value and the exact biological function of GDF15 in cerebral lower-grade gliomas (LGGs) and its potential molecular targets were examined.

MAIN METHODS

Wilcoxon signed-rank test and logistic regression were applied to analyze associations between GDF15 expression and clinical characteristics using the Cancer Genome Atlas (TCGA) database. Overall survival was analyzed using Kaplan-Meier and Cox analyses. Gene set enrichment analysis (GSEA) and the hypoxia risk model was conducted to identify the potential molecular mechanisms underlying the effects of GDF15 on LGGs tumorigenesis. The biological function of GDF15 was examined using gain- and loss-of-function experiments, and a recombinant hGDF15 protein in LGG SW1783 cells in vitro.

KEY FINDINGS

We found that higher GDF15 expression is associated with poor clinical features in LGG patients, and an independent risk factor for overall survival among LGG patients. GSEA results showed that the poor prognostic role of GDF15 in LGGs is related to hypoxia and glycolysis signatures, which was further validated using the hypoxia risk model. Furthermore, GDF15 overexpression facilitated cell proliferation, while GDF15 siRNA inhibits cell proliferation in LGG SW1783 cells. In addition, GDF15 was upregulated upon CoCl2 treatment which induces hypoxia, correlating with the upregulation of the expressions of HIF-1α and glycolysis-related key genes in SW1783 cells.

SIGNIFICANCE

GDF15 may promote LGG tumorigenesis that is associated with the hypoxia and glycolysis pathways, and thus could serve as a promising molecular target for LGG prevention and therapy.

HIF1α/HIF2α induces glioma cell dedifferentiation into cancer stem cells through Sox2 under hypoxic conditions

Objective: Our previous study showed that glioma stem-like cells could be induced to undergo dedifferentiation under hypoxic conditions, but the mechanism requires further study. HIF1α and HIF2α are the main molecules involved in the response to hypoxia, and Sox2, as a retroelement, plays an important role in the formation of induced pluripotent stem cells, especially in hypoxic microenvironments. Therefore, we performed a series of experiments to verify whether HIF1α, HIF2α and Sox2 regulated glioma cell dedifferentiation under hypoxic conditions.

Materials and methods: Sphere formation by single glioma cells was observed, and CD133 and CD15 expression was compared between the normoxic and hypoxic groups. HIF1α, HIF2α, and Sox2 expression was detected using the CGGA database, and the correlation among HIF1α, HIF2α and Sox2 levels was analyzed. We knocked out HIF1α, HIF2α and Sox2 in glioma cells and cultured them under hypoxic conditions to detect CD133 and CD15 expression. The above cells were implanted into mouse brains to analyze tumor volume and survival time.

Results: New spheres were formed from single glioma cells in 1% O₂, but no spheres were formed in 21% O₂. The cells cultured in 1% O₂ highly expressed CD133 and CD15 and had a lower apoptosis rate. The CGGA database showed HIF1α and HIF2α expression in glioma. Knocking out HIF1α or HIF2α led to a decrease in CD133 and CD15 expression and inhibited sphere formation under hypoxic conditions. Moreover, tumor volume and weight decreased after HIF1α or HIF2α knockout with the same temozolomide treatment. Sox2 was also highly expressed in glioma, and there was a positive correlation between the HIF1α/HIF2α and Sox2 expression levels. Sox2 was expressed at lower levels after HIF1α or HIF2α was knocked out. Then, Sox2 was knocked out, and we found that CD133 and CD15 expression was decreased. Moreover, a lower sphere formation rate, higher apoptosis rate, lower tumor formation rate and longer survival time after temozolomide treatment were detected in the Sox2 knockout cells.

Conclusion: In a hypoxic microenvironment, the HIF1α/HIF2α-Sox2 network induced the formation of glioma stem cells through the dedifferentiation of differentiated glioma cells, thus promoting glioma cell chemoresistance. This study demonstrates that both HIF1α and HIF2α, as genes upstream of Sox2, regulate the malignant progression of glioma through dedifferentiation.

Potential role of hydrogen sulfide in central nervous system tumors: a narrative review

Central nervous system tumors are classified as diseases of special clinical significance with high disability and high mortality. In addition to cerebrovascular diseases and craniocerebral injuries, tumors are the most common diseases of the central nervous system. Hydrogen sulfide, the third endogenous gas signaling molecule discovered in humans besides nitric oxide and carbon monoxide, plays an important role in the pathophysiology of human diseases. It is reported that hydrogen sulfide not only exerts a wide range of biological effects, but also develops a certain relationship with tumor development and neovascularization. A variety of studies have shown that hydrogen sulfide acts as a vasodilator and angiogenetic factor to facilitate growth, proliferation, migration and invasion of cancer cells. In this review, the pathological mechanisms and the effect of hydrogen sulfide on the central nervous system tumors are introduced.

Tumor Vessels Fuel the Fire in Glioblastoma

Glioblastoma, a subset of aggressive brain tumors, deploy several means to increase blood vessel supply dedicated to the tumor mass. This includes typical program borrowed from embryonic development, such as vasculogenesis and sprouting angiogenesis, as well as unconventional processes, including co-option, vascular mimicry, and transdifferentiation, in which tumor cells are pro-actively engaged. However, these neo-generated vascular networks are morphologically and functionally abnormal, suggesting that the vascularization processes are rather inefficient in the tumor ecosystem. In this review, we reiterate the specificities of each neovascularization modality in glioblastoma, and, how they can be hampered mechanistically in the perspective of anti-cancer therapies.

Expression of IDE and PITRM1 genes in ERN1 knockdown U87 glioma cells: effect of hypoxia and glucose deprivation

OBJECTIVE

The aim of the present investigation was to study the expression of genes encoding polyfunctional proteins insulinase (insulin degrading enzyme, IDE) and pitrilysin metallopeptidase 1 (PITRM1) in U87 glioma cells in response to inhibition of endoplasmic reticulum stress signaling mediated by ERN1/IRE1 (endoplasmic reticulum to nucleus signaling 1) for evaluation of their possible significance in the control of metabolism through ERN1 signaling as well as hypoxia, glucose and glutamine deprivations.

METHODS

The expression level of IDE and PITRM1 genes was studied in control and ERN1 knockdown U87 glioma cells under glucose and glutamine deprivations as well as hypoxia by quantitative polymerase chain reaction.

RESULTS

It was found that the expression level of IDE and PITRM1 genes was down-regulated in ERN1 knockdown (without ERN1 protein kinase and endoribonuclease activity) glioma cells in comparison with the control glioma cells, being more significant for PITRM1 gene. We also found up-regulation of microRNA MIR7-2 and MIRLET7A2, which have specific binding sites in 3'-untranslated region of IDE and PITRM1 mRNAs, correspondingly, and can participate in posttranscriptional regulation of these mRNA expressions. Only inhibition of ERN1 endoribonuclease did not change significantly the expression of IDE and PITRM1 genes in glioma cells. The expression of IDE and PITRM1 genes is preferentially regulated by ERN1 protein kinase. We also showed that hypoxia down-regulated the expression of IDE and PITRM1 genes and that knockdown of ERN1 signaling enzyme function modified the response of these gene expressions to hypoxia. Glucose deprivation increased the expression level of IDE and PITRM1 genes, but ERN1 knockdown enhanced only the effect of glucose deprivation on PITRM1 gene expression. Glutamine deprivation did not affect the expression of IDE gene in both types of glioma cells, but up-regulated PITRM1 gene and this up-regulation was stronger in ERN1 knockdown cells.

CONCLUSIONS

Results of this investigation demonstrate that ERN1 knockdown significantly decreases the expression of IDE and PITRM1 genes by ERN1 protein kinase mediated mechanism. The expression of both studied genes was sensitive to hypoxia as well as glucose deprivation and dependent on ERN1 signaling in gene-specific manner. It is possible that the level of these genes expression under hypoxia and glucose deprivation is a result of complex interaction of variable endoplasmic reticulum stress related and unrelated regulatory factors and contributed to the control of the cell metabolism.

The Role of 2-Oxoglutarate Dependent Dioxygenases in Gliomas and Glioblastomas: A Review of Epigenetic Reprogramming and Hypoxic Response

Gliomas are a heterogeneous group of cancers that predominantly arise from glial cells in the brain, but may also arise from neural stem cells, encompassing low-grade glioma and high-grade glioblastoma. Whereas better diagnosis and new treatments have improved patient survival for many cancers, glioblastomas remain challenging with a highly unfavorable prognosis. This review discusses a super-family of enzymes, the 2-oxoglutarate dependent dioxygenase enzymes (2-OGDD) that control numerous processes including epigenetic modifications and oxygen sensing, and considers their many roles in the pathology of gliomas. We specifically describe in more detail the DNA and histone demethylases, and the hypoxia-inducible factor hydroxylases in the context of glioma, and discuss the substrate and cofactor requirements of the 2-OGDD enzymes. Better understanding of how these enzymes contribute to gliomas could lead to the development of new treatment strategies.

HIF1α/HIF2α-Sox2/Klf4 promotes the malignant progression of glioblastoma via the EGFR-PI3K/AKT signalling pathway with positive feedback under hypoxia

Previous studies have suggested that hypoxic responses are regulated by hypoxia-inducible factors (HIFs), which in turn promote the malignant progression of glioblastoma (GBM) by inhibiting apoptosis and increasing proliferation; these events lead to a poor prognosis of GBM patients. However, there are still no HIF-targeted therapies for the treatment of GBM. We have conducted series of experiments and discovered that GBM cells exhibit features indicative of malignant progression and are present in a hypoxic environment. Knocking out HIF1α or HIF2α alone resulted in no significant change in cell proliferation and cell cycle progression in response to acute hypoxia, but cells showed inhibition of stemness expression and chemosensitization to temozolomide (TMZ) treatment. However, simultaneously knocking out HIF1α and HIF2α inhibited cell cycle arrest and promoted proliferation with decreased stemness, making GBM cells more sensitive to chemotherapy, which could improve patient prognosis. Thus, HIF1α and HIF2α regulate each other with negative feedback. In addition, HIF1α and HIF2α are upstream regulators of epidermal growth factor (EGF), which controls the malignant development of GBM through the EGFR-PI3K/AKT-mTOR-HIF1α signalling pathway. In brief, the HIF1α/HIF2α-EGF/EGFR-PI3K/AKT-mTOR-HIF1α signalling axis contributes to the growth of GBM through a positive feedback mechanism. Finally, HIF1α and HIF2α regulate Sox2 and Klf4, contributing to stemness expression and inducing cell cycle arrest, thus increasing malignancy in GBM. In summary, HIF1α and HIF2α regulate glioblastoma malignant progression through the EGFR-PI3K/AKT pathway via a positive feedback mechanism under the effects of Sox2 and Klf4, which provides a new tumour development model and strategy for glioblastoma treatment.

Disruption of the Complex between GAPDH and Hsp70 Sensitizes C6 Glioblastoma Cells to Hypoxic Stress

Hypoxia, which commonly accompanies tumor growth, depending on its strength may cause the enhancement of tumorigenicity of cancer cells or their death. One of the proteins targeted by hypoxia is glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and we demonstrated here that hypoxia mimicked by treating C6 rat glioblastoma cells with cobalt chloride caused an up-regulation of the enzyme expression, while further elevation of hypoxic stress caused the enzyme aggregation concomitantly with cell death. Reduction or elevation of GAPDH performed with the aid of specific shRNAs resulted in the augmentation of the tumorigenicity of C6 cells or their sensitization to hypoxic stress. Another hypoxia-regulated protein, Hsp70 chaperone, was shown to prevent the aggregation of oxidized GAPDH and to reduce hypoxia-mediated cell death. In order to release the enzyme molecules from the chaperone, we employed its inhibitor, derivative of colchicine. The compound was found to substantially increase aggregation of GAPDH and to sensitize C6 cells to hypoxia both in vitro and in animals bearing tumors with distinct levels of the enzyme expression. In conclusion, blocking the chaperonic activity of Hsp70 and its interaction with GAPDH may become a promising strategy to overcome tumor resistance to multiple environmental stresses and enhance existing therapeutic tools.

Deciphering the Role of Autophagy in Treatment of Resistance Mechanisms in Glioblastoma

Autophagy is a process essential for cellular energy consumption, survival, and defense mechanisms. The role of autophagy in several types of human cancers has been explicitly explained; however, the underlying molecular mechanism of autophagy in glioblastoma remains ambiguous. Autophagy is thought to be a “double-edged sword”, and its effect on tumorigenesis varies with cell type. On the other hand, autophagy may play a significant role in the resistance mechanisms against various therapies. Therefore, it is of the utmost importance to gain insight into the molecular mechanisms deriving the autophagy-mediated therapeutic resistance and designing improved treatment strategies for glioblastoma. In this review, we discuss autophagy mechanisms, specifically its pro-survival and growth-suppressing mechanisms in glioblastomas. In addition, we try to shed some light on the autophagy-mediated activation of the cellular mechanisms supporting radioresistance and chemoresistance in glioblastoma. This review also highlights autophagy’s involvement in glioma stem cell behavior, underlining its role as a potential molecular target for therapeutic interventions.

Flavonoids Targeting HIF-1: Implications on Cancer Metabolism

Tumor hypoxia is described as an oxygen deprivation in malignant tissue. The hypoxic condition is a consequence of an imbalance between rapidly proliferating cells and a vascularization that leads to lower oxygen levels in tumors. Hypoxia-inducible factor 1 (HIF-1) is an essential transcription factor contributing to the regulation of hypoxia-associated genes. Some of these genes modulate molecular cascades associated with the Warburg effect and its accompanying pathways and, therefore, represent promising targets for cancer treatment. Current progress in the development of therapeutic approaches brings several promising inhibitors of HIF-1. Flavonoids, widely occurring in various plants, exert a broad spectrum of beneficial effects on human health, and are potentially powerful therapeutic tools against cancer. Recent evidences identified numerous natural flavonoids and their derivatives as inhibitors of HIF-1, associated with the regulation of critical glycolytic components in cancer cells, including pyruvate kinase M2(PKM2), lactate dehydrogenase (LDHA), glucose transporters (GLUTs), hexokinase II (HKII), phosphofructokinase-1 (PFK-1), and pyruvate dehydrogenase kinase (PDK). Here, we discuss the results of most recent studies evaluating the impact of flavonoids on HIF-1 accompanied by the regulation of critical enzymes contributing to the Warburg phenotype. Besides, flavonoid effects on glucose metabolism via regulation of HIF-1 activity represent a promising avenue in cancer-related research. At the same time, only more-in depth investigations can further elucidate the mechanistic and clinical connections between HIF-1 and cancer metabolism.

The HIF1α/HIF2α-miR210-3p network regulates glioblastoma cell proliferation, dedifferentiation and chemoresistance through EGF under hypoxic conditions

Hypoxia-inducible factor 1α (HIF1α) promotes the malignant progression of glioblastoma under hypoxic conditions, leading to a poor prognosis for patients with glioblastoma; however, none of the therapies targeting HIF1α in glioblastoma have successfully eradicated the tumour. Therefore, we focused on the reason and found that treatments targeting HIF1α and HIF2α simultaneously increased tumour volume, but the combination of HIF1α/HIF2α-targeted therapies with temozolomide (TMZ) reduced tumourigenesis and significantly improved chemosensitization. Moreover, miR-210-3p induced HIF1α expression but inhibited HIF2α expression, suggesting that miR-210-3p regulates HIF1α/HIF2α expression. Epidermal growth factor (EGF) has been shown to upregulate HIF1α expression under hypoxic conditions. However, in the present study, in addition to the signalling pathways mentioned above, the upstream proteins HIF1α and HIF2α have been shown to induce EGF expression by binding to the sequences AGGCGTGG and GGGCGTGG. Briefly, in a hypoxic microenvironment the HIF1α/HIF2α-miR210-3p network promotes the malignant progression of glioblastoma through a positive feedback loop with EGF. Additionally, differentiated glioblastoma cells underwent dedifferentiation to produce glioma stem cells under hypoxic conditions, and simultaneous knockout of HIF1α and HIF2α inhibited cell cycle arrest but promoted proliferation with decreased stemness, promoting glioblastoma cell chemosensitization. In summary, both HIF1α and HIF2α regulate glioblastoma cell proliferation, dedifferentiation and chemoresistance through a specific pathway, which is important for glioblastoma treatments.

Annexin A2-STAT3-Oncostatin M receptor axis drives phenotypic and mesenchymal changes in glioblastoma

Glioblastoma (GBM) is characterized by extensive tumor cell invasion, angiogenesis, and proliferation. We previously established subclones of GBM cells with distinct invasive phenotypes and identified annexin A2 (ANXA2) as an activator of angiogenesis and perivascular invasion. Here, we further explored the role of ANXA2 in regulating phenotypic transition in GBM. We identified oncostatin M receptor (OSMR) as a key ANXA2 target gene in GBM utilizing microarray analysis and hierarchical clustering analysis of the Ivy Glioblastoma Atlas Project and The Cancer Genome Atlas datasets. Overexpression of ANXA2 in GBM cells increased the expression of OSMR and phosphorylated signal transducer and activator of transcription 3 (STAT3) and enhanced cell invasion, angiogenesis, proliferation, and mesenchymal transition. Silencing of OSMR reversed the ANXA2-induced phenotype, and STAT3 knockdown reduced OSMR protein expression. Exposure of GBM cells to hypoxic conditions activated the ANXA2–STAT3–OSMR signaling axis. Mice bearing ANXA2-overexpressing GBM exhibited shorter survival times compared with control tumor-bearing mice, whereas OSMR knockdown increased the survival time and diminished ANXA2-mediated tumor invasion, angiogenesis, and growth. Further, we uncovered a significant relationship between ANXA2 and OSMR expression in clinical GBM specimens, and demonstrated their correlation with tumor histopathology and patient prognosis. Our results indicate that the ANXA2–STAT3–OSMR axis regulates malignant phenotypic changes and mesenchymal transition in GBM, suggesting that this axis is a promising therapeutic target to treat GBM aggressiveness.

Peptidylarginine Deiminase Isozyme-Specific PAD2, PAD3 and PAD4 Inhibitors Differentially Modulate Extracellular Vesicle Signatures and Cell Invasion in Two Glioblastoma Multiforme Cell Lines

Glioblastoma multiforme (GBM) is an aggressive adult brain tumour with poor prognosis. Roles for peptidylarginine deiminases (PADs) in GBM have recently been highlighted. Here, two GBM cell lines were treated with PAD2, PAD3 and PAD4 isozyme-specific inhibitors. Effects were assessed on extracellular vesicle (EV) signatures, including EV-microRNA cargo (miR21, miR126 and miR210), and on changes in cellular protein expression relevant for mitochondrial housekeeping (prohibitin (PHB)) and cancer progression (stromal interaction molecule 1 (STIM-1) and moesin), as well as assessing cell invasion. Overall, GBM cell-line specific differences for the three PAD isozyme-specific inhibitors were observed on modulation of EV-signatures, PHB, STIM-1 and moesin protein levels, as well as on cell invasion. The PAD3 inhibitor was most effective in modulating EVs to anti-oncogenic signatures (reduced miR21 and miR210, and elevated miR126), to reduce cell invasion and to modulate protein expression of pro-GBM proteins in LN229 cells, while the PAD2 and PAD4 inhibitors were more effective in LN18 cells. Furthermore, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for deiminated proteins relating to cancer, metabolism and inflammation differed between the two GBM cell lines. Our findings highlight roles for the different PAD isozymes in the heterogeneity of GBM tumours and the potential for tailored PAD-isozyme specific treatment.

Potential implications of hydrogen peroxide in the pathogenesis and therapeutic strategies of gliomas

Glioma is the most common type of primary brain tumor, and it has a high mortality rate. Currently, there are only a few therapeutic approaches for gliomas, and their effects are unsatisfactory. Therefore, uncovering the pathogenesis and exploring more therapeutic strategies for the treatment of gliomas are urgently needed to overcome the ongoing challenges. Cellular redox imbalance has been shown to be associated with the initiation and progression of gliomas. Among reactive oxygen species (ROS), hydrogen peroxide (H₂O₂) is considered the most suitable for redox signaling and is a potential candidate as a key molecule that determines the fate of cancer cells. In this review, we discuss the potential cellular and molecular roles of H₂O₂ in gliomagenesis and explore the potential implications of H₂O₂ in radiotherapy and chemotherapy and in the ongoing challenges of current glioma treatment. Moreover, we evaluate H₂O₂ as a potential redox sensor and potential driver molecule of nanocatalytic therapeutic strategies for glioma treatment.

Hypoxic regulation of EDN1, EDNRA, EDNRB, and ECE1 gene expressions in ERN1 knockdown U87 glioma cells

Objective. The aim of the present investigation was to study the effect of hypoxia on the expression of genes encoding endothelin-1 (EDN1) and its cognate receptors (EDNRA and EDNRB) as well as endothelin converting enzyme 1 (ECE1) in U87 glioma cells in response to inhibition of endoplasmic reticulum stress signaling mediated by ERN1/IRE1 (endoplasmic reticulum to nucleus signaling 1) for evaluation of their possible significance in the control of glioma growth through ERN1 and hypoxia.

Methods. The expression level of EDN1, EDNRA, EDNRB, and ECE1 genes as well as micro-RNA miR-19, miR-96, and miR-206 was studied in control and ERN1 knockdown U87 glioma cells under hypoxia by quantitative polymerase chain reaction.

Results. It was shown that the expression level of EDN1, EDNRA, EDNRB, and ECE1 genes was up-regulated in ERN1 knockdown glioma cells in comparison with the control glioma cells, being more significant for endothelin-1. We also observed down-regulation of microRNA miR-206, miR-96, and miR-19a, which have specific binding sites in mRNA EDN1, EDNRA, and EDNRB, correspondingly, and can participate in posttranscriptional regulation of these mRNA expressions. Furthermore, inhibition of ERN1 endoribonuclease lead to up-regulation of EDNRA and ECE1 gene expressions and down-regulation of the expression level of EDN1 and EDNRB genes in glioma cells. Thus, the expression of EDNRA and ECE1 genes is regulated by ERN1 endoribonuclease, but EDN1 and EDNRB genes preferentially by ERN1 protein kinase. We have also shown that hypoxia enhanced the expression of EDN1, EDNRA, and ECE1 genes and that knockdown of ERN1 signaling enzyme function significantly modified the response of all studied gene expressions to hypoxia. Thus, effect of hypoxia on the expression level of EDN1 and ECE1 genes was significantly or completely reduced in ERN1 knockdown glioma cells since the expression of EDNRA gene was down-regulated under hypoxia. Moreover, hypoxia is induced the expression of EDNRB gene in ERN1 knockdown glioma cells.

Conclusions. Results of this investigation demonstrate that ERN1 knockdown significantly increased the expression of endothelin-1 and its receptors as well as ECE1 genes by different mechanisms and that all studied gene expressions were sensitive to hypoxia. It is possible that hypoxic regulation of the expression of these genes is a result of complex interaction of variable ERN1 related transcription and regulatory factors with HIF1A and possibly contributed to the control of glioma growth.

Enhancement of radiosensitivity by the novel anticancer quinolone derivative vosaroxin in preclinical glioblastoma models

Purpose

Glioblastoma multiforme (GBM) is the most aggressive brain tumor. The activity of vosaroxin, a first-in-class anticancer quinolone derivative that intercalates DNA and inhibits topoisomerase II, was investigated in GBM preclinical models as a single agent and combined with radiotherapy (RT).

Results

Vosaroxin showed antitumor activity in clonogenic survival assays, with IC₅₀ of 10−100 nM, and demonstrated radiosensitization. Combined treatments exhibited significantly higher γH2Ax levels compared with controls. In xenograft models, vosaroxin reduced tumor growth and showed enhanced activity with RT; vosaroxin/RT combined was more effective than temozolomide/RT. Vosaroxin/RT triggered rapid and massive cell death with characteristics of necrosis. A minor proportion of treated cells underwent caspase-dependent apoptosis, in agreement with in vitro results. Vosaroxin/RT inhibited RT-induced autophagy, increasing necrosis. This was associated with increased recruitment of granulocytes, monocytes, and undifferentiated bone marrow–derived lymphoid cells. Pharmacokinetic analyses revealed adequate blood-brain penetration of vosaroxin. Vosaroxin/RT increased disease-free survival (DFS) and overall survival (OS) significantly compared with RT, vosaroxin alone, temozolomide, and temozolomide/RT in the U251-luciferase orthotopic model.

Materials and Methods

Cellular, molecular, and antiproliferative effects of vosaroxin alone or combined with RT were evaluated in 13 GBM cell lines. Tumor growth delay was determined in U87MG, U251, and T98G xenograft mouse models. (DFS) and (OS) were assessed in orthotopic intrabrain models using luciferase-transfected U251 cells by bioluminescence and magnetic resonance imaging.

Conclusions

Vosaroxin demonstrated significant activity in vitro and in vivo in GBM models, and showed additive/synergistic activity when combined with RT in O6-methylguanine methyltransferase-negative and -positive cell lines.

Identification of P4HA1 as a prognostic biomarker for high-grade gliomas

BACKGROUND

Prolyl 4-Hydroxylase Subunit Alpha 1 (P4HA1) is the active catalytic component of prolyl 4-hydroxylase and plays a crucial role in modulating extracellular matrix hemostasis. P4HA1 has been reported to promote tumor progression by enhancing invasion and angiogenesis. Overexpression of P4HA1 is associated with decreased survival for patients with breast and prostate cancer. However, the prognostic significance of P4HA1 for glioma patients remains undefined.

METHODS

The expression of P4HA1 in 290 gliomas (WHO grade II-IV) and 10 normal brain tissues was examined with TMA-based immunohistochemistry assay. The correlation between P4HA1 expression and clinicopathological parameters as well as the prognosis of glioma patients was investigated.

RESULTS

Cytoplasmic expression of P4HA1 is high in 37.93% of all glioma cases, with 44.98% in high-grade gliomas and 19.75% in low-grade gliomas respectively. Increased P4HA1 level was correlated with advanced histological grade (p<0.01) and old age (p=0.01). Upregulation of P4HA1, as well as histological grade, was an independent risk factor for unfavorable prognosis. Subgroup analysis demonstrated that high P4HA1 expression was significantly associated with poor prognosis for high-grade gliomas (p<0.01) but not for low-grade gliomas.

CONCLUSIONS

P4HA1 was upregulated in gliomas. High expression of P4HA1 was correlated with the malignancy of gliomas and could serve as a prognostic indicator for patients with high-grade gliomas.

Coiled-coil domain containing 109B is a HIF1α-regulated gene critical for progression of human gliomas

Background

The coiled-coil domain is a structural motif found in proteins that participate in a variety of biological processes. Aberrant expression of such proteins has been shown to be associated with the malignant behavior of human cancers. In this study, we investigated the role of a specific family member, coiled-coil domain containing 109B (CCDC109B), in human gliomas.

Methods and results

We confirmed that CCDC109B was highly expressed in high grade gliomas (HGG; WHO III–IV) using immunofluorescence, western blot analysis, immunohistochemistry (IHC) and open databases. Through Cox regression analysis of The Cancer Genome Atlas (TCGA) database, we found that the expression levels of CCDC109B were inversely correlated with patient overall survival and it could serve as a prognostic marker. Then, a serious of cell functional assays were performed in human glioma cell lines, U87MG and U251, which indicated that silencing of CCDC109B attenuated glioma proliferation and migration/invasion both in vitro and in vivo. Notably, IHC staining in primary glioma samples interestingly revealed localization of elevated CCDC109B expression in necrotic areas which are typically hypoxic. Moreover, small interfering RNA (siRNA) and specific inhibiters of HIF1α led to decreased expression of CCDC109B in vitro and in vivo. Transwell assay further showed that CCDC109B is a critical factor in mediating HIF1α-induced glioma cell migration and invasion.

Conclusion

Our study elucidated a role for CCDC109B as an oncogene and a prognostic marker in human gliomas. CCDC109B may provide a novel therapeutic target for the treatment of human glioma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1266-9) contains supplementary material, which is available to authorized users.

Role of AHR and HIF-1α in Glioblastoma Metabolism

Glioblastoma (GBM) progression is associated with metabolic remodeling in both glioma and immune cells, resulting in the use of aerobic glycolysis as the main source of energy and biosynthetic molecules. The transcription factor hypoxia-inducible factor (HIF)-1α drives this metabolic reorganization. Oxygen levels, as well as other factors, control the activity of HIF-1α. In addition, the ligand-activated transcription factor aryl hydrocarbon receptor (AHR) modulates tumor-specific immunity and can also participate in metabolic remodeling. AHR activity is regulated by tryptophan derivatives present in the tumor microenvironment. Thus, the tumor microenvironment and signaling via HIF-1α and AHR regulate the metabolism of gliomas and immune cells, modulating tumor-specific immunity and, consequently, tumor growth. Here, we review the roles of HIF-1α and AHR in cancer and immune cell metabolism in GBM.

Advances in the targeting of HIF-1α and future therapeutic strategies for glioblastoma multiforme (Review)

Cell metabolism can be reprogrammed by tissue hypoxia leading to cell transformation and glioblastoma multiforme (GBM) progression. In response to hypoxia, GBM cells are able to express a transcription factor called hypoxia inducible factor-1 (HIF-1). HIF-1 belongs to a family of heterodimeric proteins that includes HIF-1α and HIF-1β subunits. HIF-1α has been reported to play a pivotal role in GBM development and progression. In the present review, we discuss the role of HIF-1α in glucose uptake, cancer proliferation, cell mobility and chemoresistance in GBM. Evidence from previous studies indicates that HIF-1α regulates angiogenesis, metabolic and transcriptional signaling pathways. Examples of such are the EGFR, PI3K/Akt and MAPK/ERK pathways. It affects cell migration and invasion by regulating glucose metabolism and growth in GBM cells. The present review focuses on the strategies through which to target HIF-1α and the related downstream genes highlighting their regulatory roles in angiogenesis, apoptosis, migration and glucose metabolism for the development of future GBM therapeutics. Combined treatment with inhibitors of HIF-1α and glycolysis may enhance antitumor effects in clinical settings.

Intranasal Oncolytic Virotherapy with CXCR4-Enhanced Stem Cells Extends Survival in Mouse Model of Glioma

The challenges to effective drug delivery to brain tumors are twofold: (1) there is a lack of non-invasive methods of local delivery and (2) the blood-brain barrier limits systemic delivery. Intranasal delivery of therapeutics to the brain overcomes both challenges. In mouse model of malignant glioma, we observed that a small fraction of intranasally delivered neural stem cells (NSCs) can migrate to the brain tumor site. Here, we demonstrate that hypoxic preconditioning or overexpression of CXCR4 significantly enhances the tumor-targeting ability of NSCs, but without altering their phenotype only in genetically modified NSCs. Modified NSCs deliver oncolytic virus to glioma more efficiently and extend survival of experimental animals in the context of radiotherapy. Our findings indicate that intranasal delivery of stem cell-based therapeutics could be optimized for future clinical applications, and allow for safe and repeated administration of biological therapies to brain tumors and other CNS disorders.

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Intranasal delivery of NSCs is a promising platform for glioma therapy

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Hypoxia or CXCR4 overexpression enhances NSC migration to glioma

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Oncolytic viruses loaded in CXCR4-enhanced NSCs improve animal survival

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Non-invasive intranasal NSC-based therapies warrant clinical translation

Aberrant expression of miR-153 is associated with overexpression of hypoxia-inducible factor-1α in refractory epilepsy

Evidence suggest that overexpression of hypoxia-inducible factor-1α (HIF-1α) is linked to multidrug resistance of epilepsy. Here we explored whether aberrant expression of HIF-1α is regulated by miRNAs. Genome-wide microRNA expression profiling was performed on temporal cortex resected from mesial temporal lobe epilepsy (mTLE) patients and age-matched controls. miRNAs that are putative regulator of HIF-1α were predicted via target scan and confirmed by real-time quantitative polymerase chain reaction (RT-qPCR). Mimics or miRNA morpholino inhibitors were transfected in astrocytes and luciferase reporter assay was applied to detect HIF-11α expression. Microarray profiling identified down-regulated miR-153 as a putative regulator of HIF-1α in temporal cortex resected from surgical mTLE patients. RT-qPCR confirmed down-regulation of miR-153 in plasma of mTLE patients in an independent validation cohort. Knockdown of miR-153 significantly enhanced expression of HIF-1α while forced expression of miR-153 dramatically inhibited HIF-1α expression in pharmacoresistant astrocyte model. Luciferase assay established that miR-153 might inhibit HIF-1α expression via directly targeting two binding sites in the 3′UTR region of HIF-1α transcript. These data suggest that down-regulation of miR-153 may contribute to enhanced expression of HIF-1α in mTLE and serve as a novel biomarker and treatment target for epilepsy.

Combined over-expression of the hypoxia-inducible factor 2α gene and its long non-coding RNA predicts unfavorable prognosis of patients with osteosarcoma

BACKGROUND

LncRNA hypoxia-inducible factor-2α (HIF-2α) promoter upstream transcript (HIF2PUT) functions as a novel regulatory factor of osteosarcoma stem cells partly by controlling HIF-2α expression. The aim of this study was to investigate the clinical significance of HIF-2α and HIF2PUT in human osteosarcoma.

MATERIALS AND METHODS

Quantitative real-time PCR was performed to detect the expression levels of HIF-2α mRNA and HIF2PUT in 82 surgical specimens of primary osteosarcoma and matched non-cancerous bone tissues. Then, the associations of HIF-2α and/or HIF2PUT expression with various clinicopathological features of osteosarcoma patients were statistically analyzed. Moreover, their prognostic value was further evaluated.

RESULTS

Compared with non-cancerous bone tissues, HIF-2α mRNA and HIF2PUT expression were both significantly upregulated in osteosarcoma tissues (all P<0.001). Interestingly, the expression levels of HIF-2α mRNA in osteosarcoma tissues were positively correlated with those of HIF2PUT (r=0.28, P=0.009). Additionally, osteosarcoma patients with HIF-2α mRNA and/or HIF2PUT over-expression more frequently had large tumor size (all P<0.05), advanced clinical stage (all P<0.01) and positive distant metastasis (all P<0.01). Moreover, osteosarcoma patients with HIF-2α mRNA and/or HIF2PUT over-expression had a significantly shorter overall and disease-free survival (all P<0.05). Furthermore, Cox multivariate analysis identified that HIF-2α mRNA and/or HIF2PUT expression, clinical stage and distant metastasis were all independent and significant prognostic factors for both overall and disease-free survival (all P<0.05).

CONCLUSIONS

HIF-2α and HIF2PUT upregulation may be a common feature in human osteosarcomas with aggressive potency. The over-expression of the two molecules, alone or combined, may predict poor prognosis in osteosarcoma patients.

Radioresistance of Brain Tumors

Radiation therapy (RT) is frequently used as part of the standard of care treatment of the majority of brain tumors. The efficacy of RT is limited by radioresistance and by normal tissue radiation tolerance. This is highlighted in pediatric brain tumors where the use of radiation is limited by the excessive toxicity to the developing brain. For these reasons, radiosensitization of tumor cells would be beneficial. In this review, we focus on radioresistance mechanisms intrinsic to tumor cells. We also evaluate existing approaches to induce radiosensitization and explore future avenues of investigation.

The Impact of Hypoxia and Mesenchymal Transition on Glioblastoma Pathogenesis and Cancer Stem Cells Regulation

Glioblastoma (GBM) is an aggressive primary brain tumor with potential for wide dissemination and resistance to standard treatments. Although GBM represents a single histopathologic diagnosis under current World Health Organization criteria, data from multiplatform molecular profiling efforts, including The Cancer Genome Atlas, indicate that multiple subgroups with distinct markers and biology exist. It remains unclear whether treatment resistance differs based on subgroup. Recent evidence suggests that hypoxia, or absence of normal tissue oxygenation, is important in generating tumor resistance through a signaling cascade driven by hypoxia-inducible factors and vascular endothelial growth factor. Hypoxia can result in isolation of tumor cells from therapeutic agents and activation of downstream tumor protective mechanisms. In addition, there are links between hypoxia and the phenomenon of mesenchymal transition in gliomas. Mesenchymal transformation in gliomas resembles at many levels the epithelial-mesenchymal transition that has been described in other solid tumors in which epithelial cells lose their epithelial characteristics and take on a more mesenchymal phenotype, but the mesenchymal transition in brain tumors is also distinct, perhaps related to the unique cell types and cellular organization in the brain and brain tumors. Cancer stem cells, which are specific cell populations involved in self-renewal, differentiation, and GBM pathophysiology, are also importantly regulated by hypoxia signaling pathways. In this review, we discuss the interplay of hypoxia and mesenchymal signaling in GBM including the key pathway regulators and downstream genes, the effect of these processes in regulation of the tumor microenvironment and cancer stem cells, and their role in treatment resistance.

Dopamine induces growth inhibition and vascular normalization through reprogramming M2-polarized macrophages in rat C6 glioma

Dopamine (DA), a monoamine catecholamine neurotransmitter with antiangiogenic activity, stabilizes tumor vessels in colon, prostate and ovarian cancers, thus increases chemotherapeutic efficacy. Here, in the rat C6 glioma models, we investigated the vascular normalization effects of DA and its mechanisms of action. DA (25, 50mg/kg) inhibited tumor growth, while a precursor of DA (levodopa) prolonged the survival time of rats bearing orthotopic C6 glioma. DA improved tumor perfusion, with significant effects from day 3, and a higher level at days 5 to 7. In addition, DA decreased microvessel density and hypoxia-inducible factor-1α expression in tumor tissues, while increasing the coverage of pericyte. Conversely, an antagonist of dopamine receptor 2 (DR2) (eticlopride) but not DR1 (butaclamol) abrogated DA-induced tumor regression and vascular normalization. Furthermore, DA improved the delivery and efficacy of temozolomide therapy. Importantly, DA increased representative M1 markers (iNOS, CXCL9, etc.), while decreasing M2 markers (CD206, arginase-1, etc.). Depletion of macrophages by clodronate or zoledronic acid attenuated the effects of DA. Notably, DA treatment induced M2-to-M1 polarization in RAW264.7 cells and mouse peritoneal macrophages, and enhanced the migration of pericyte-like cells (10T1/2), which was reversed by eticlopride or DR2-siRNA. Such changes were accompanied by the downregulation of VEGF/VEGFR2 signaling. In summary, DA induces growth inhibition and vascular normalization through reprogramming M2-polarized macrophages. Thus, targeting the tumor microvasculature by DA represents a promising strategy for human glioma therapy.