Glucocorticoid receptor β regulates injury-mediated astrocyte activation and contributes to glioma pathogenesis via modulation of β-catenin/TCF transcriptional activity

Context is key: glucocorticoid receptor and corticosteroid therapeutics in outcomes after traumatic brain injury

Traumatic brain injury (TBI) is a global health burden, and survivors suffer functional and psychiatric consequences that can persist long after injury. TBI induces a physiological stress response by activating the hypothalamic-pituitary-adrenal (HPA) axis, but the effects of injury on the stress response become more complex in the long term. Clinical and experimental evidence suggests long lasting dysfunction of the stress response after TBI. Additionally, pre- and post-injury stress both have negative impacts on outcome following TBI. This bidirectional relationship between stress and injury impedes recovery and exacerbates TBI-induced psychiatric and cognitive dysfunction. Previous clinical and experimental studies have explored the use of synthetic glucocorticoids as a therapeutic for stress-related TBI outcomes, but these have yielded mixed results. Furthermore, long-term steroid treatment is associated with multiple negative side effects. There is a pressing need for alternative approaches that improve stress functionality after TBI. Glucocorticoid receptor (GR) has been identified as a fundamental link between stress and immune responses, and preclinical evidence suggests GR plays an important role in microglia-mediated outcomes after TBI and other neuroinflammatory conditions. In this review, we will summarize GR-mediated stress dysfunction after TBI, highlighting the role of microglia. We will discuss recent studies which target microglial GR in the context of stress and injury, and we suggest that cell-specific GR interventions may be a promising strategy for long-term TBI pathophysiology.

Acetylation halts missense mutant p53 aggregation and rescues tumor suppression in non-small cell lung cancers

TP53 mutations are ubiquitous with tumorigenesis in non-small cell lung cancers (NSCLC). By analyzing the TCGA database, we reported that TP53 missense mutations are correlated with chromosomal instability and tumor mutation burden in NSCLC. The inability of wild-type nor mutant p53 expression can't predict survival in lung cancer cohorts, however, an examination of primary NSCLC tissues found that acetylated p53 did yield an association with improved survival outcomes. Molecularly, we demonstrated that acetylation drove the ubiquitination and degradation of mutant p53 but enhanced stability of wild-type p53. Moreover, acetylation of a missense p53 mutation prevented the gain of oncogenic function observed in typical TP53 mutant-expressing cells and enhanced tumor suppressor functions. Consequently, acetylation inducer targeting of missense mutant p53 may be a viable therapeutic goal for NSCLC treatment and may improve the accuracy of current efforts to utilize p53 mutations in a prognostic manner.

Characterization of EGFR-reprogrammable temozolomide-resistant cells in a model of glioblastoma

Temozolomide (TMZ) resistance is a major clinical challenge for glioblastoma (GBM). O⁶-methylguanine-DNA methyltransferase (MGMT) mediated DNA damage repair is a key mechanism for TMZ resistance. However, MGMT-null GBM patients remain resistant to TMZ, and the process for resistance evolution is largely unknown. Here, we developed an acquired TMZ resistant xenograft model using serial implantation of MGMT-hypermethylated U87 cells, allowing the extraction of stable, TMZ resistant (TMZ-R) tumors and primary cells. The derived tumors and cells exhibited stable multidrug resistance both in vitro and in vivo. Functional experiments, as well as single-cell RNA sequencing (scRNA-seq), indicated that TMZ treatment induced cellular heterogeneity including quiescent cancer stem cells (CSCs) in TMZ-R tumors. A subset of these were labeled by NES⁺/SOX2⁺/CADM1⁺ and demonstrated significant advantages for drug resistance. Further study revealed that Epidermal Growth Factor Receptor (EGFR) deficiency and diminished downstream signaling may confer this triple positive CSCs subgroup’s quiescent phenotypes and chemoresistance. Continuous EGF treatment improved the chemosensitivity of TMZ-R cells both in vitro and in vivo, mechanically reversing cell cycle arrest and reduced drug uptake. Further, EGF treatment of TMZ-R tumors favorably normalized the response to TMZ in combination therapy. Here, we characterize a unique subgroup of CSCs in MGMT-null experimental glioblastoma, identifying EGF + TMZ therapy as a potential strategy to overcome cellular quiescence and TMZ resistance, likely endowed by deficient EGFR signaling.

The Human Glucocorticoid Receptor Beta: From Molecular Mechanisms to Clinical Implications

Glucocorticoids play a fundamental role in a plethora of cellular processes and physiologic functions through binding on a ubiquitously expressed receptor, the glucocorticoid receptor (GR), which functions as a ligand-activated transcription factor influencing the transcription rate of numerous genes in a positive or negative fashion. For many years, we believed that the pleiotropic actions of glucocorticoids were mediated by a single GR protein expressed by the NR3C1 gene. Nowadays, we know that the NR3C1 gene encodes 2 main receptor isoforms, the GRα and the GRβ, through alternative splicing of the last exons. Furthermore, the alternative initiation of GR mRNA translation generates 8 distinct GRα and possibly 8 different GRβ receptor isoforms. The tremendous progress of cellular, molecular, and structural biology in association with the data explosion provided by bioinformatics have enabled a deeper understanding of the role of GRβ in cellular homeostasis. In this review article, I will provide an update on the cellular properties and functions of hGRβ and summarize the current knowledge about the evolving role of the beta isoform of glucocorticoid receptor in endocrine physiology, pathophysiology, and beyond.

The positive regulatory loop of TCF4N/p65 promotes glioblastoma tumourigenesis and chemosensitivity

Background

NF‐κB signaling is widely linked to the pathogenesis and treatment resistance in cancers. Increasing attention has been paid to its anti‐oncogenic roles, due to its key functions in cellular senescence and the senescence‐associated secretory phenotype (SASP). Therefore, thoroughly understanding the function and regulation of NF‐κB in cancers is necessary prior to the application of NF‐κB inhibitors.

Methods

We established glioblastoma (GBM) cell lines expressing ectopic TCF4N, an isoform of the β‐catenin interacting transcription factor TCF7L2, and evaluated its functions in GBM tumorigenesis and chemotherapy in vitro and in vivo. In p65 knock‐out or phosphorylation mimic (S536D) cell lines, the dual role and correlation of TCF4N and NF‐κB signaling in promoting tumorigenesis and chemosensitivity was investigated by in vitro and in vivo functional experiments. RNA‐seq and computational analysis, immunoprecipitation and ubiquitination assay, minigene splicing assay and luciferase reporter assay were performed to identify the underlying mechanism of positive feedback regulation loop between TCF4N and the p65 subunit of NF‐κB. A eukaryotic cell‐penetrating peptide targeting TCF4N, 4N, was used to confirm the therapeutic significance.

Results

Our results indicated that p65 subunit phosphorylation at Ser 536 (S536) and nuclear accumulation was a promising prognostic marker for GBM, and endowed the dual functions of NF‐κB in promoting tumorigenesis and chemosensitivity. p65 S536 phosphorylation and nuclear stability in GBM was regulated by TCF4N. TCF4N bound p65, induced p65 phosphorylation and nuclear translocation, inhibited its ubiquitination/degradation, and subsequently promoted NF‐κB activity. p65 S536 phosphorylation was essential for TCF4N‐led senescence‐independent SASP, GBM tumorigenesis, tumor stem‐like cell differentiation and chemosensitivity. Activation of p65 was closely connected to alterative splicing of TCF4N, a likely positive feedback regulation loop between TCF4N and p65 in GBM. 4N increased chemosensitivity, highlighting a novel anti‐cancer strategy.

Conclusion

Our study defined key roles of TCF4N as a novel regulator of NF‐κB through mutual regulation with p65 and provided a new avenue for GBM inhibition.

Glucocorticoid Receptor β Isoform Predominates in the Human Dysplastic Brain Region and Is Modulated by Age, Sex, and Antiseizure Medication

The glucocorticoid receptor (GR) at the blood−brain barrier (BBB) is involved in the pathogenesis of drug-resistant epilepsy with focal cortical dysplasia (FCD); however, the roles of GR isoforms GRα and GRβ in the dysplastic brain have not been revealed. We utilized dysplastic/epileptic and non-dysplastic brain tissue from patients who underwent resective epilepsy surgery to identify the GRα and GRβ levels, subcellular localization, and cellular specificity. BBB endothelial cells isolated from the dysplastic brain tissue (EPI-ECs) were used to decipher the key BBB proteins related to drug regulation and BBB integrity compared to control and transfected GRβ-overexpressed BBB endothelial cells. GRβ was upregulated in dysplastic compared to non-dysplastic tissues, and an imbalance of the GRα/GRβ ratio was significant in females vs. males and in patients > 45 years old. In EPI-ECs, the subcellular localization and expression patterns of GRβ, Hsp90, CYP3A4, and CYP2C9 were consistent with GRβ+ brain endothelial cells. Active matrix metalloproteinase levels and activity increased, whereas claudin-5 levels decreased in both EPI-ECs and GRβ+ endothelial cells. In conclusion, the GRβ has a major effect on dysplastic BBB functional proteins and is age and gender-dependent, suggesting a critical role of brain GRβ in dysplasia as a potential biomarker and therapeutic target in epilepsy.

Molecular Mechanisms and Clinical Challenges of Glioma Invasion

Glioma is the most common primary brain tumor, and its prognosis is poor. Glioma cells are highly invasive to the brain parenchyma. It is difficult to achieve complete resection due to the nature of the brain tissue, and tumors that invade the parenchyma often recur. The invasiveness of tumor cells has been studied from various aspects, and the related molecular mechanisms are gradually becoming clear. Cell adhesion factors and extracellular matrix factors have a strong influence on glioma invasion. The molecular mechanisms that enhance the invasiveness of glioma stem cells, which have been investigated in recent years, have also been clarified. In addition, it has been discussed from both basic and clinical perspectives that current therapies can alter the invasiveness of tumors, and there is a need to develop therapeutic approaches to glioma invasion in the future. In this review, we will summarize the factors that influence the invasiveness of glioma based on the environment of tumor cells and tissues, and describe the impact of the treatment of glioma on invasion in terms of molecular biology, and the novel therapies for invasion that are currently being developed.

Oncogenic Activity of Glucocorticoid Receptor β Is Controlled by Ubiquitination-Dependent Interaction with USP49 in Glioblastoma Cells

Previous studies have demonstrated that glucocorticoid receptor β (GRβ) functions as an oncoprotein, regulating the malignant phenotypes and stem-like cell maintaining in human glioblastoma (GBM). Of the glucocorticoid receptor (GR) isoforms, GRβ and GRα are highly homologous, though the mechanism underlying the distinct functions of these two isoforms in GBM has not been clarified. Here by establishing a carboxyl-terminal (COOH-terminal) deletion mutant, we determined that GRβ can be ubiquitinated. We also found that its COOH terminal is essential for this ubiquitination. The mutation of a lysine to arginine at residue 733 (K733R) blocked the ubiquitination of GRβ, indicating that K733 is a key site for ubiquitination. Using K733R to establish nonubiquitinated GRβ, we demonstrated that ubiquitination not only regulates the stability and nuclear translocation of GRβ, but is also a vital mechanism for its oncogenic functions in vitro and in vivo. Protein interaction assay further indicated that ubiquitin-specific protease 49 (USP49) is a GRβ-binding protein and the interaction depends on GRβ ubiquitination. USP49 knockdown resulted in a decrease of cell proliferation, invasion, and an increase of cell apoptosis. More importantly, USP49 knockdown increased ubiquitination and amplified the oncogenic effects of GRβ, confirming the decisive role of ubiquitination on GRβ carcinogenicity. Taken together, these findings established that ubiquitination is a vial process for GRβ the execution of oncogenic functions in GBM and that the K733 site is crucial for ubiquitination of GRβ. IMPLICATIONS: This work is the first identify of the activation GRβ by a single lysine point-mediated ubiquitination and proteasome degradation, which determines its oncogenic functions in GBM.

Glutamine synthetase regulation by dexamethasone, RU486, and compound A in astrocytes derived from aged mouse cerebral hemispheres is mediated via glucocorticoid receptor

Glucocorticoids (GCs) regulate astrocyte function, while glutamine synthetase (GS), an enzyme highly expressed in astrocytes, is one of the most remarkable GCs-induced genes. GCs mediate their effects through their cognate glucocorticoid receptor (GRα and GRβ isoforms); however, the mechanism via which these isoforms regulate GS activity in astrocytes remains unknown. We used dexamethasone (DEX), a classical GRα/GRβ agonist, RU486, which is a specific GRβ ligand, and Compound A, a known "dissociated" ligand, to delineate the mechanism via which GR modulates GS activity. Aged Mouse Cerebral Hemisphere astrocytes were treated with DEX (1 μM), RU486 (1 nM-1 μM) or compound A (10 μM), alone or in combination with DEX. GS activity and expression, GR isoforms (mRNA and protein levels), and GRα subcellular trafficking were measured. DEX increased GS activity in parallel with GRα nuclear translocation. RU486 increased GS activity in absence of GRα nuclear translocation implicating thus a role of GRβ-mediated mechanism compound A had no effect on GS activity implicating a GRα-GRE-mediated mechanism. None of the compounds affected whole-cell GRα protein content. DEX reduced GRα and GRβ mRNA levels, while RU486 increased GRβ gene expression. We provide evidence that GS activity, in astrocytes, is regulated via GRα- and GRβ-mediated pathways with important implications in pathological conditions in which astrocytes are involved.

PRNCR1: a long non-coding RNA with a pivotal oncogenic role in cancer

Long non-coding RNAs (lncRNAs) have been gaining importance in the field of cancer research in recent years. PRNCR1 (prostate cancer-associated non-coding RNA1) is a 12.7 kb, intron-less lncRNA found to play an oncogenic role in malignancy of diverse organs including prostate, breast, lung, oral cavity, colon and rectum. Single-nucleotide polymorphisms (SNPs) of PRNCR1 locus have been found to be associated with cancer susceptibility in different populations. In this review, an attempt has been made for the first time to summarize all sorts of available data on PRNCR1 to date from relevant databases (GeneCard, LncExpDB, Ensembl genome browser, and PubMed). As functional roles of PRNCR1, miRNA (microRNA) sponging was mostly highlighted in the pathogenesis of different cancer; in addition, an association of the lncRNA with chromatin-modifying complex to enhance androgen receptor-mediated gene transcription was reported in prostate cancer. Diagnostic and prognostic importance of PRNCR1 was found in some malignancies suggesting potency of the lncRNA to serve as a clinical biomarker. For PRNCR1 SNPs, although cancer susceptibility of the risk alleles/genotypes was reported in different populations, majorities of the findings were not replicated and underlying molecular mechanisms remained unexplored. Therapeutic implication of PRNCR1 was not studied well and future research may come up in this direction for intervening novel strategies to fight against cancer.

Primary Generalized Glucocorticoid Resistance and Hypersensitivity Syndromes: A 2021 Update

Glucocorticoids are the final products of the neuroendocrine hypothalamic-pituitary-adrenal axis, and play an important role in the stress response to re-establish homeostasis when it is threatened, or perceived as threatened. These steroid hormones have pleiotropic actions through binding to their cognate receptor, the human glucocorticoid receptor, which functions as a ligand-bound transcription factor inducing or repressing the expression of a large number of target genes. To achieve homeostasis, glucocorticoid signaling should have an optimal effect on all tissues. Indeed, any inappropriate glucocorticoid effect in terms of quantity or quality has been associated with pathologic conditions, which are characterized by short-term or long-lasting detrimental effects. Two such conditions, the primary generalized glucocorticoid resistance and hypersensitivity syndromes, are discussed in this review article. Undoubtedly, the tremendous progress of structural, molecular, and cellular biology, in association with the continued progress of biotechnology, has led to a better and more in-depth understanding of these rare endocrinologic conditions, as well as more effective therapeutic management.

Glioblastoma cells express crucial enzymes involved in androgen synthesis: 3β-hydroxysteroid dehydrogenase, 17-20α-hydroxylase, 17β-hydroxysteroid dehydrogenase and 5α-reductase

Glioblastoma (GB) is the most common and aggressive primary brain tumour in adult humans. Therapeutic resistance and tumour recurrence after surgical removal contribute to poor prognosis for glioblastoma patients. Men are known to be more likely than women to develop an aggressive form of GB, and differences in sex steroids have emerged as a leading explanation for this finding. Studies indicate that the metabolism and proliferation of GB‐derived cells are increased by sex steroids, the expression of androgen receptors (ARs) and the synthesis of androgens and oestrogens, suggesting that these hormones have a role in the tumour pathogenesis. The expression of aromatase, the enzyme that converts androgens to oestrogens, has been reported in glial cells and GB cell lines. Thus, it was necessary to test whether the steroidogenic enzymes involved in androgen synthesis are expressed in GB cells. Therefore, here, we investigated the expression of four key enzymes involved in androgen synthesis in human‐derived GB cells. U87 cells were cultured in Dulbecco's modified Eagle medium plus foetal bovine serum and antibiotics on slides for immunocytochemistry or immunofluorescence. U87, LN229 and C6 cells were also cultured in multi‐well chambers to obtain proteins for Western blotting. We used primary antibodies against 3β‐hydroxysteroid dehydrogenase (3β‐HSD), 17α‐hydroxilase/17,20‐lyase (P450c17), 17β‐hydroxysteroid dehydrogenase (17β‐HSD) and 5α‐reductase. Immunocytochemistry, and immunofluorescence results revealed that glioblastoma cells express 3β‐HSD, P450c17, 17β‐HSD and 5α‐reductase proteins in their cytoplasm. Moreover, Western blot analyses revealed bands corresponding to the molecular weight of these four enzymes in the three GB cell lines. Thus, glioblastoma cells have the key enzymatic machinery necessary to synthesize androgens, and these enzymes might be useful targets for new therapeutic approaches.

Glucocorticoid Receptor β (GRβ): Beyond Its Dominant-Negative Function

Glucocorticoids (GCs) act via the GC receptor (GR), a receptor ubiquitously expressed in the body where it drives a broad spectrum of responses within distinct cell types and tissues, which vary in strength and specificity. The variability of GR-mediated cell responses is further extended by the existence of GR isoforms, such as GRα and GRβ, generated through alternative splicing mechanisms. While GRα is the classic receptor responsible for GC actions, GRβ has been implicated in the impairment of GRα-mediated activities. Interestingly, in contrast to the popular belief that GRβ actions are restricted to its dominant-negative effects on GRα-mediated responses, GRβ has been shown to have intrinsic activities and "directly" regulates a plethora of genes related to inflammatory process, cell communication, migration, and malignancy, each in a GRα-independent manner. Furthermore, GRβ has been associated with increased cell migration, growth, and reduced sensitivity to GC-induced apoptosis. We will summarize the current knowledge of GRβ-mediated responses, with a focus on the GRα-independent/intrinsic effects of GRβ and the associated non-canonical signaling pathways. Where appropriate, potential links to airway inflammatory diseases will be highlighted.

Dutasteride combined with androgen receptor antagonists inhibit glioblastoma U87 cell metabolism, proliferation, and invasion capacity: Androgen regulation

Glioblastoma (GB) is the most common and aggressive primary brain tumor in adult humans. Therapeutic resistance and tumor recurrence after surgical resection contributes to a poor prognosis for glioblastoma patients. Men are known to be more likely than women to develop an aggressive form of GB. Although the reasons for this disparity remain poorly understood, differences in sex steroids have emerged as a leading explanation. Studies indicate that GB-derived cells express androgen receptors (ARs) and synthesize androgens, suggesting that androgens may have a role in the tumor pathogenesis. Thus, our objective was to investigate the effects of the 5α-reductase enzyme inhibitor dutasteride, the AR antagonists cyproterone and flutamide, and combinations of these drugs on the metabolism, proliferation, and invasion capacity of GB-derived U87 cells. We also examined the effects of three natural androgens testosterone, androstenedione and dihydrotestosterone (T, A₄, and DHT) on these cells. Cell metabolism was investigated by MTT assay, proliferation was assessed by the bromodeoxyuridine (BrdU) incorporation assay, and invasion was assessed by Boyden chamber assay. The results revealed that T and especially DHT, but not A₄, increased U87 cell metabolism and proliferation. Following these findings, we examined the effect of adding dutasteride, cyproterone, or flutamide to the culture media and found that they all significantly decreased cell metabolism and proliferation. Dutasteride also significantly reduced cell invasion. Moreover, any combination of these drugs enhanced their inhibitory effects; the combination of dutasteride to flutamide was most effective at decreasing GB cell proliferation. Our results suggest that administering a combination of AR antagonists and enzyme blockers may be a more effective alternative treatment for GB.

Astrocytoma: A Hormone-Sensitive Tumor?

Astrocytomas and, in particular, their most severe form, glioblastoma, are the most aggressive primary brain tumors and those with the poorest vital prognosis. Standard treatment only slightly improves patient survival. Therefore, new therapies are needed. Very few risk factors have been clearly identified but many epidemiological studies have reported a higher incidence in men than women with a sex ratio of 1:4. Based on these observations, it has been proposed that the neurosteroids and especially the estrogens found in higher concentrations in women's brains could, in part, explain this difference. Estrogens can bind to nuclear or membrane receptors and potentially stimulate many different interconnected signaling pathways. The study of these receptors is even more complex since many isoforms are produced from each estrogen receptor encoding gene through alternative promoter usage or splicing, with each of them potentially having a specific role in the cell. The purpose of this review is to discuss recent data supporting the involvement of steroids during gliomagenesis and to focus on the potential neuroprotective role as well as the mechanisms of action of estrogens in gliomas.

Glucocorticoid regulates mesenchymal cell differentiation required for perinatal lung morphogenesis and function

While antenatal glucocorticoids are widely used to enhance lung function in preterm infants, cellular and molecular mechanisms by which glucocorticoid receptor (GR) signaling influences lung maturation remain poorly understood. Deletion of the glucocorticoid receptor gene (Nr3c1) from fetal pulmonary mesenchymal cells phenocopied defects caused by global Nr3c1 deletion, while lung epithelial- or endothelial-specific Nr3c1 deletion did not impair lung function at birth. We integrated genome-wide gene expression profiling, ATAC-seq, and single cell RNA-seq data in mice in which GR was deleted or activated to identify the cellular and molecular mechanisms by which glucocorticoids control prenatal lung maturation. GR enhanced differentiation of a newly defined proliferative mesenchymal progenitor cell (PMP) into matrix fibroblasts (MFBs), in part by directly activating extracellular matrix-associated target genes, including Fn1, Col16a4, and Eln and by modulating VEGF, JAK-STAT, and WNT signaling. Loss of mesenchymal GR signaling blocked fibroblast progenitor differentiation into mature MFBs, which in turn increased proliferation of SOX9+ alveolar epithelial progenitor cells and inhibited differentiation of mature alveolar type II (AT₂) and AT₁ cells. GR signaling controls genes required for differentiation of a subset of proliferative mesenchymal progenitors into matrix fibroblasts, in turn, regulating signals controlling AT₂/AT₁ progenitor cell proliferation and differentiation and identifying cells and processes by which glucocorticoid signaling regulates fetal lung maturation.

Overexpression of Foxc1 regenerates crushed rat facial nerves by promoting Schwann cells migration via the Wnt/β-catenin signaling pathway

Facial paralysis can result in severe implications for patients. A good prognosis depends on the degree of nerve regeneration. Schwann cells (SCs) play an important role in facial nerve development and regeneration through migration. Forkhead box C1 (Foxc1), a member of the forkhead transcription factor family, is implicated in cell migration. However, the role of Foxc1 in the progression after facial nerve crush remains unknown. Our aim was to evaluate the effect of Foxc1 overexpression on SC migration and recovery of facial nerves after crush injury. The rat facial nerve crush injury model was established through the use of unilateral surgery. The results showed that the expression of Foxc1 was increased in the surgery group compared to that of the control group. SCs were isolated from the sciatic nerves and cultured. Foxc1, delivered by an adeno‐associated virus in vivo, or adenovirus in vitro, both induced overexpression of Foxc1, and increased the expression of CXCL12 and β‐catenin. After the transfection of Foxc1, the migration of SC was increased both in vitro and in vivo, was reduced by the inhibition of CXCL12 or β‐catenin. The facial nerve function and the nerve axon remyelination of the rats transfected with Foxc1 were significantly improved after nerve crush injury. Overall, the results demonstrated that overexpression of Foxc1 promoted SC migration by regulating CXCL12 via the Wnt/β‐catenin pathway, thus contributing to improved facial nerve function after crush injury.

Chronic Ethanol Consumption Alters Glucocorticoid Receptor Isoform Expression in Stress Neurocircuits and Mesocorticolimbic Brain Regions of Alcohol-Preferring Rats

Evidence suggests the hypothalamic-pituitary-adrenal (HPA) axis is involved in Alcohol Use Disorders (AUDs), which might be mediated by an imbalance of glucocorticoid receptor (GR), GRα and GRβ, activity. GRβ antagonizes the GRα isoform to cause glucocorticoid (GC) resistance. In the present study, we aimed to investigate the effects of chronic continuous free-choice access to ethanol on GR isoform expression in subregions of the mesocorticolimbic reward circuit. Adult male alcohol-preferring (P) rats had concurrent access to 15% and 30% ethanol solutions, with ad lib access to lab chow and water, for six weeks. Quantitative Real-time PCR (RT-PCR) analysis showed that chronic ethanol consumption reduced GRα expression in the nucleus accumbens shell (NAcsh) and hippocampus, whereas ethanol drinking reduced GRβ in the nucleus accumbens core (NAcc), prefrontal cortex (PFC), and hippocampus. An inhibitor of GRα, microRNA-124-3p (miR124-3p) was significantly higher in the NAcsh, and GC-induced gene, GILZ, as a measure of GC-responsiveness, was significantly lower. These were not changed in the NAcc. Likewise, genes associated with HPA axis activity were not significantly changed by ethanol drinking [i.e., corticotrophin-releasing hormone (Crh), adrenocorticotrophic hormone (Acth), and proopiomelanocortin (Pomc)] in these brain regions. Serum corticosterone levels were not changed by ethanol drinking. These data indicate that the expression of GRα and GRβ isoforms are differentially affected by ethanol drinking despite HPA-associated peptides remaining unchanged, at least at the time of tissue harvesting. Moreover, the results suggest that GR changes may stem from ethanol-induced GC-resistance in the NAcsh. These findings confirm a role for stress in high ethanol drinking, with GRα and GRβ implicated as targets for the treatment of AUDs.

The effect of finasteride and dutasteride on the synthesis of neurosteroids by glioblastoma cells

Glioblastoma (GBM) is the most aggressive local brain tumor and effective treatments are lacking. Many studies have proposed an important participation of steroid hormones in the development of gliomas. Evidence was provided by statistics analysis where the incidence in adult population is 50% higher in men than in women. Female patients have a better prognosis for survival compared to male patients with GBM. Also, the expression of receptors to estrogen, progesterone and androgens in glioma cell lines and tumor biopsies, and glucocorticoid receptors in GBM cell lines had been reported. Here we have investigated the effect of the pharmacological inhibition of 5-α reductases on the capacity of GBM derived cell lines C6 (rat) and U87 (human) to synthesize neurosteroids. As the knowledge of the pathways used to synthesize neurosteroids by GBM derived cells was incomplete, we have investigated the synthesis of these steroids by C6 and U87 cells using tritiated precursors and thin layer chromatography (TLC). Increasing concentrations of finasteride and dutasteride were added to U87 culture media that was collected after 24 and 48 h. The results of the study showed that C6 cells incubated with ³H-cholesterol yielded dihydroandrosterone, hydroxytestosterone, androstenediol, androstenedione and estriol, while U87 cells also synthesized progesterone, and androstanedione. Incubation with ³H-androstenedione or ³H-testosterone mainly yielded dihydrotestosterone, androsterone, dihydroandrosterone, hydroxytestosterone, and estradiol in both lines. To note, we showed here for the first time that U87 cells synthesize corticosteroids. Addition of finasteride or dutasteride to U87 cells reduced androgen and estrogen synthesis. Dutasteride also decreased the synthesis of dihydrocorticosterone and allotetrahydrodesoxycorticosterone while deoxycorticosterone was accumulated. In summary, both GBM cell lines synthesize numerous neurosteroids, including 5-α reductase products and 3α-HSD pathways that were inhibited by finasteride and dutasteride. These inhibitors may be considered as tools to control neurosteroid synthesis of potential relevance for GBM survival.

Long non-coding RNA polymorphisms on 8q24 are associated with the prognosis of gastric cancer in a Chinese population

Background

Gastric cancer (GC) remains the third leading cause of cancer death in China. Although genome-wide association studies have identified the association between several single nucleotide polymorphisms (SNPs) on 8q24 and the risk of GC, the role of these SNPs in the prognosis of GC in Chinese populations has not yet been fully evaluated. Therefore, this study was conducted to explore the association between long non-coding RNA (lncRNA) polymorphisms on 8q24 and the prognosis of GC.

Methods

We genotyped 726 surgically resected GC patients to explore the association between eight SNPs in the lncRNAs CCAT1 (rs10087719, rs7816475), PCAT1 (rs1026411), PRNCR1 (rs12682421, rs13252298), and CASC8 (rs1562430, rs4871789, rs6983267) transcribed from the 8q24 locus and the prognosis of GC in a Chinese population.

Results

We found that the patients carrying rs12682421 AA genotypes survived for a shorter time than those with the GG/GA genotype (HR = 1.39, 95% confidence interval (CI) [1.09-1.78]). Compared with the CC/CT genotype, the TT genotype of rs1562430 was associated with an increased risk of death (HR = 1.38, 95% CI [1.06-1.80]). Furthermore, the results also identified the rs1026411 SNP as an independent prognostic factor for poor survival in GC patients. Patients carrying AA/AG variant genotypes had a 36% increased risk of death compared to those carrying the GG genotype (HR = 1.36, 95% CI [1.06-1.74]). These findings suggested that the rs12682421, rs1026411 and rs1562430 SNPs may contribute to the survival of GC and be prognostic markers for GC.

Activation of G protein-coupled receptor 30 protects neurons by regulating autophagy in astrocytes

Ischemic stroke leads to neuronal damage induced by excitotoxicity, inflammation, and oxidative stress. Astrocytes play diverse roles in stroke and ischemia-induced inflammation, and autophagy is critical for maintaining astrocytic functions. Our previous studies showed that the activation of G protein-coupled receptor 30 (GPR30), an estrogen membrane receptor, protected neurons from excitotoxicity. However, the role of astrocytic GPR30 in maintaining autophagy and neuroprotection remained unclear. In this study, we found that the neuroprotection induced by G1 (GPR30 agonist) in wild-type mice after a middle cerebral artery occlusion was completely blocked in GPR30 conventional knockout (KO) mice but partially attenuated in astrocytic or neuronal GPR30 KO mice. In cultured primary astrocytes, glutamate exposure induced astrocyte proliferation and decreased astrocyte autophagy by activating mammalian target of rapamycin (mTOR) and c-Jun N-terminal kinase (JNK) and inhibiting p38 mitogen-activated protein kinase (MAPK) pathway. G1 treatment restored autophagy to its basal level by regulating the p38 pathway but not the mTOR and JNK signaling pathways. Our findings revealed a key role of GPR30 in neuroprotection via the regulation of astrocyte autophagy and support astrocytic GPR30 as a potential drug target against ischemic brain damage.

PKCγ promotes axonal remodeling in the cortico-spinal tract via GSK3β/β-catenin signaling after traumatic brain injury

Traumatic brain injury (TBI) is a common cause of death and disability. Enhancing the midline-crossing of the contralateral corticospinal tract (CST) to the denervated side of spinal cord facilitates functional recovery after TBI. Activation of the gamma isoform of PKC (PKCγ) in contralateral CST implicates its roles in promoting CST remodeling after TBI. In this study, we deployed loss and gain of function strategies in N2a cells and primary cortical neurons in vitro, and demonstrated that PKCγ is not only important but necessary for neuronal differentiation, neurite outgrowth and axonal branching but not for axonal extension. Mechanically, through the phosphorylation of GSK3β, PKCγ stabilizes the expression of cytosolic β-catenin and increase GAP43 expression, thus promoting axonal outgrowth. Further, rAAV2/9-mediated delivery of constitutive PKCγ in the corticospinal tract after unilateral TBI in vivo additionally showed that specifically delivery of active PKCγ mutant to cortical neuron promotes midline crossing of corticospinal fibers from the uninjured side to the denervated cervical spinal cord. This PKCγ-mediated injury response promoted sensorimotor functional recovery. In conclusion, PKCγ mediates stability of β-catenin through the phosphorylation of GSK3β to facilitate neuronal differentiation, neurite outgrowth and axonal branching, and PKCγ maybe a novel therapeutic target for physiological and functional recovery after TBI.

Neurovascular glucocorticoid receptors and glucocorticoids: implications in health, neurological disorders and drug therapy

Glucocorticoid receptors (GRs) are ubiquitous transcription factors widely studied for their role in controlling events related to inflammation, stress and homeostasis. Recently, GRs have reemerged as crucial targets of investigation in neurological disorders, with a focus on pharmacological strategies to direct complex mechanistic GR regulation and improve therapy. In the brain, GRs control functions necessary for neurovascular integrity, including responses to stress, neurological changes mediated by the hypothalamic-pituitary-adrenal axis and brain-specific responses to corticosteroids. Therefore, this review will examine GR regulation at the neurovascular interface in normal and pathological conditions, pharmacological GR modulation and glucocorticoid insensitivity in neurological disorders.

Uncovering a multitude of human glucocorticoid receptor variants: an expansive survey of a single gene

Background

Glucocorticoids are commonly used in the clinical setting for their potent anti-inflammatory effects; however, significant variations in response to treatment have been demonstrated. Although the underlying mechanisms have yet to be fully understood, this variable response may be a result of alterations in human glucocorticoid receptor (hGR) expression and function. In addition to hGRα, the biologically active isoform, a screening of current databases and publications revealed five alternative splice isoforms and hundreds of variants that have been reported to date. Many of these changes in the hGR-coding gene, NR3C1, have been linked to pathophysiology. However, many studies focus on evaluating hGR expression in vitro or detecting previously reported variants.

Results

In this study, blood from healthy volunteers, burn and asthma patients, as well as from peripheral blood mononuclear cells isolated from leukoreduced donor whole blood, were screened for NR3C1 isoforms. We identified more than 1500 variants, including an additional 21 unique splice isoforms which contain 15 new cryptic exons. A dynamic database, named the Universal hGR (UhGR), was created to annotate and visualize the variants.

Conclusion

This identification of naturally occurring and stress-induced hGR isoforms, as well as the establishment of an hGR-specific database, may reveal new patterns or suggest areas of interest that will lead to the improved understanding of the human stress response system.

Electronic supplementary material

The online version of this article (10.1186/s12863-019-0718-z) contains supplementary material, which is available to authorized users.

Glucocorticoid Resistance

Primary generalized glucocorticoid resistance or Chrousos syndrome is a rare disorder, which affects all tissues expressing the human glucocorticoid receptor. It is characterized by generalized, partial tissue insensitivity to glucocorticoids caused by genetic defects in the NR3C1 gene. We and others have applied standard methods of molecular and structural biology to investigate the molecular mechanisms and conformational alterations through which the mutant glucocorticoid receptors lead to the broad spectrum of clinical manifestations of Chrousos syndrome. The ever-increasing application of novel technologies, including the next-generation sequencing, will enhance our knowledge in factors that influence the glucocorticoid signal transduction in a positive or negative fashion.

Nuclear Smad6 promotes gliomagenesis by negatively regulating PIAS3-mediated STAT3 inhibition

To date, the molecular mechanism underlying constitutive signal transducer and activator of transcription 3 (STAT3) activation in gliomas is largely unclear. In this study, we report that Smad6 is overexpressed in nuclei of glioma cells, which correlates with poor patient survival and regulates STAT3 activity via negatively regulating the Protein Inhibitors of Activated STAT3 (PIAS3). Mechanically, Smad6 interacts directly with PIAS3, and this interaction is mediated through the Mad homology 2 (MH2) domain of Smad6 and the Ring domain of PIAS3. Smad6 recruits Smurf1 to facilitate PIAS3 ubiquitination and degradation, which also depends on the MH2 domain and the PY motif of Smad6. Consequently, Smad6 reduces PIAS3-mediated STAT3 inhibition and promotes glioma cell growth and stem-like cell initiation. Moreover, the Smad6 MH2 transducible protein restores PIAS3 expression and subsequently reduces gliomagenesis. Collectively, we conclude that nuclear-Smad6 enhances glioma development by inducing PIAS3 degradation and subsequent STAT3 activity upregulation.

The Unwanted Cell Migration in the Brain: Glioma Metastasis

Cell migration is identified as a highly orchestrated process. It is a fundamental and essential phenomenon underlying tissue morphogenesis, wound healing, and immune response. Under dysregulation, it contributes to cancer metastasis. Brain is considered to be the most complex organ in human body containing many types of neural cells with astrocytes playing crucial roles in monitoring both physiological and pathological functions. Astrocytoma originates from astrocytes and its most malignant type is glioblastoma multiforme (WHO Grade IV astrocytoma), which is capable to infiltrate widely into the neighboring brain tissues making a complete resection of tumors impossible. Very recently, we have reviewed the mechanisms for astrocytes in migration. Given the fact that astrocytoma shares many histological features with astrocytes, we therefore attempt to review the mechanisms for glioma cells in migration and compare them to normal astrocytes, hoping to obtain a better insight into the dysregulation of migratory mechanisms contributing to their metastasis in the brain.

Stress-Related and Circadian Secretion and Target Tissue Actions of Glucocorticoids: Impact on Health

Living organisms are highly complex systems that must maintain a dynamic equilibrium or homeostasis that requires energy to be sustained. Stress is a state in which several extrinsic or intrinsic disturbing stimuli, the stressors, threaten, or are perceived as threatening, homeostasis. To achieve homeostasis against the stressors, organisms have developed a highly sophisticated system, the stress system, which provides neuroendocrine adaptive responses, to restore homeostasis. These responses must be appropriate in terms of size and/or duration; otherwise, they may sustain life but be associated with detrimental effects on numerous physiologic functions of the organism, leading to a state of disease-causing disturbed homeostasis or cacostasis. In addition to facing a broad spectrum of external and/or internal stressors, organisms are subject to recurring environmental changes associated with the rotation of the planet around itself and its revolution around the sun. To adjust their homeostasis and to synchronize their activities to day/night cycles, organisms have developed an evolutionarily conserved biologic system, the "clock" system, which influences several physiologic functions in a circadian fashion. Accumulating evidence suggests that the stress system is intimately related to the circadian clock system, with dysfunction of the former resulting in dysregulation of the latter and vice versa. In this review, we describe the functional components of the two systems, we discuss their multilevel interactions, and we present how excessive or prolonged activity of the stress system affects the circadian rhythm of glucocorticoid secretion and target tissue effects.

Glucocorticoid receptor beta increases migration of human bladder cancer cells

Bladder cancer is observed worldwide having been associated with a host of environmental and lifestyle risk factors. Recent investigations on anti-inflammatory glucocorticoid signaling point to a pathway that may impact bladder cancer. Here we show an inverse effect on the glucocorticoid receptor (GR) isoform signaling that may lead to bladder cancer. We found similar GRα expression levels in the transitional uroepithelial cancer cell lines T24 and UMUC-3. However, the T24 cells showed a significant (p < 0.05) increased expression of GRβ compared to UMUC-3, which also correlated with higher migration rates. Knockdown of GRβ in the T24 cells resulted in a decreased migration rate. Mutational analysis of the 3' untranslated region (UTR) of human GRβ revealed that miR144 might positively regulate expression. Indeed, overexpression of miR144 increased GRβ by 3.8 fold. In addition, miR144 and GRβ were upregulated during migration. We used a peptide nucleic acid conjugated to a cell penetrating-peptide (Sweet-P) to block the binding site for miR144 in the 3'UTR of GRβ. Sweet-P effectively prevented miR144 actions and decreased GRβ expression, as well as the migration of the T24 human bladder cancer cells. Therefore, GRβ may have a significant role in bladder cancer, and possibly serve as a therapeutic target for the disease.

Overexpression of Glucocorticoid Receptor β Enhances Myogenesis and Reduces Catabolic Gene Expression

Unlike the glucocorticoid receptor α (GRα), GR β (GRβ) has a truncated ligand-binding domain that prevents glucocorticoid binding, implicating GRα as the mediator of glucocorticoid-induced skeletal muscle loss. Because GRβ causes glucocorticoid resistance, targeting GRβ may be beneficial in impairing muscle loss as a result of GRα activity. The purpose of this study was to determine how the overexpression of GRβ affects myotube formation and dexamethasone (Dex) responsiveness. We measured GR isoform expression in C₂C12 muscle cells in response to Dex and insulin, and through four days of myotube formation. Next, lentiviral-mediated overexpression of GRβ in C₂C12 was performed, and these cells were characterized for cell fusion and myotube formation, as well as sensitivity to Dex via the expression of ubiquitin ligases. GRβ overexpression increased mRNA levels of muscle regulatory factors and enhanced proliferation in myoblasts. GRβ overexpressing myotubes had an increased fusion index. Myotubes overexpressing GRβ had lower forkhead box O3 (Foxo3a) mRNA levels and a blunted muscle atrophy F-box/Atrogen-1 (MAFbx) and muscle ring finger 1 (MuRF1) response to Dex. We showed that GRβ may serve as a pharmacological target for skeletal muscle growth and protection from glucocorticoid-induced catabolic signaling. Increasing GRβ levels in skeletal muscle may cause a state of glucocorticoid resistance, stabilizing muscle mass during exposure to high doses of glucocorticoids.

Depression as a Glial-Based Synaptic Dysfunction

Recent studies combining pharmacological, behavioral, electrophysiological and molecular approaches indicate that depression results from maladaptive neuroplastic processes occurring in defined frontolimbic circuits responsible for emotional processing such as the prefrontal cortex, hippocampus, amygdala and ventral striatum. However, the exact mechanisms controlling synaptic plasticity that are disrupted to trigger depressive conditions have not been elucidated. Since glial cells (astrocytes and microglia) tightly and dynamically interact with synapses, engaging a bi-directional communication critical for the processing of synaptic information, we now revisit the role of glial cells in the etiology of depression focusing on a dysfunction of the “quad-partite” synapse. This interest is supported by the observations that depressive-like conditions are associated with a decreased density and hypofunction of astrocytes and with an increased microglia “activation” in frontolimbic regions, which is expected to contribute for the synaptic dysfunction present in depression. Furthermore, the traditional culprits of depression (glucocorticoids, biogenic amines, brain-derived neurotrophic factor, BDNF) affect glia functioning, whereas antidepressant treatments (serotonin-selective reuptake inhibitors, SSRIs, electroshocks, deep brain stimulation) recover glia functioning. In this context of a quad-partite synapse, systems modulating glia-synapse bidirectional communication—such as the purinergic neuromodulation system operated by adenosine 5′-triphosphate (ATP) and adenosine—emerge as promising candidates to “re-normalize” synaptic function by combining direct synaptic effects with an ability to also control astrocyte and microglia function. This proposed triple action of purines to control aberrant synaptic function illustrates the rationale to consider the interference with glia dysfunction as a mechanism of action driving the design of future pharmacological tools to manage depression.

Involvement of the Androgen and Glucocorticoid Receptors in Bladder Cancer

Bladder cancer is encountered worldwide having been associated with a host of environmental and lifestyle risk factors. The disease has a male to female prevalence of 3 : 1. This disparity has raised the possibility of the androgen receptor (AR) pathway being involved in the genesis of the disease; indeed, research has shown that AR is involved in and is likely a driver of bladder cancer. Similarly, an inflammatory response has been implicated as a major player in bladder carcinogenesis. Consistent with this concept, recent work on anti-inflammatory glucocorticoid signaling points to a pathway that may impact bladder cancer. The glucocorticoid receptor- (GR-) α isoform has an important role in suppressing inflammatory processes, which may be attenuated by AR in the development of bladder cancer. In addition, a GR isoform that is inhibitory to GRα, GRβ, is proinflammatory and has been shown to induce cancer growth. In this paper, we review the evidence of inflammatory mediators and the relationship of AR and GR isoforms as they relate to the propensity for bladder cancer.

Role of Wnt Signaling in Central Nervous System Injury

The central nervous system (CNS) is highly sensitive to external mechanical damage, presenting a limited capacity for regeneration explained in part by its inability to restore either damaged neurons or the synaptic network. The CNS may suffer different types of external injuries affecting its function and/or structure, including stroke, spinal cord injury, and traumatic brain injury. These pathologies critically affect the quality of life of a large number of patients worldwide and are often fatal because available therapeutics are ineffective and produce limited results. Common effects of the mentioned pathologies involves the triggering of several cellular and metabolic responses against injury, including infiltration of blood cells, inflammation, glial activation, and neuronal death. Although some of the underlying molecular mechanisms of those responses have been elucidated, the mechanisms driving these processes are poorly understood in the context of CNS injury. In the last few years, it has been suggested that the activation of the Wnt signaling pathway could be important in the regenerative response after CNS injury, activating diverse protective mechanisms including the stimulation of neurogenesis, blood brain structure consolidation and the recovery of cognitive brain functions. Because Wnt signaling is involved in several physiological processes, the putative positive role of its activation after injury could be the basis for novel therapeutic approaches to CNS injury.

Transcriptional and metabolic effects of glucocorticoid receptor α and β signaling in zebrafish

In humans and zebrafish, 2 glucocorticoid (GC) receptor (GR) splice variants exist: the canonical GR α-isoform (GRα), and the GRβ. In the present study, we have used the zebrafish model system in order to reveal genes affected by each of these 2 receptor isoforms. By injecting zebrafish embryos with different splice-blocking morpholinos, we could knock down both GR isoforms or could target the alternative splicing of the GR pre-mRNA in favor of the GRβ. In addition, specific GRβ overexpression was achieved by injecting mRNA. Embryos were treated with the synthetic GC dexamethasone, and transcriptome analysis was performed. Two distinct gene clusters were found that were regulated by GRα: one that was regulated by GRα under basal conditions (presence of endogenous cortisol only), and one that was regulated upon increased activation of GRα (using a pharmacological dose of dexamathasone). GRβ may act as a dominant-negative inhibitor of GRα when GRβ is overexpressed and the GRα expression level is knocked down simultaneously. However, without GRα knockdown, no evidence for this activity was found. In addition, the data indicate regulation of gene transcription through other mechanisms of action by GRβ. We also investigated the concentrations of several metabolites using nuclear magnetic resonance spectroscopy. We found that dexamethasone treatment and knockdown of GRα together with overexpression of GRβ had opposite effects on glucose, amino acid, and fatty acid levels. Thus, we have shed new light on the molecular mechanisms of GC-induced effects on metabolism, which are known to increase the risk of obesity, hyperglycemia, and diabetes.

Chrousos syndrome: from molecular pathogenesis to therapeutic management

BACKGROUND

Primary Generalized Glucocorticoid Resistance or Chrousos syndrome is a rare genetic condition characterized by end-organ insensitivity to glucocorticoids owing to inactivating mutations of the NR3C1 gene.

MATERIALS AND METHODS

We conducted a systematic review of the published, peer-reviewed medical literature using MEDLINE (1975 through November 2014) to identify original articles and reviews on this topic. The search terms included 'primary generalized glucocorticoid resistance', 'Chrousos syndrome', 'glucocorticoid receptor gene' and 'glucocorticoid receptor mutations'.

RESULTS

Only a few cases of Chrousos syndrome have been described to date, ranging from asymptomatic to severe forms of mineralocorticoid and/or androgen excess. All reported cases have been associated with point mutations or deletions in the NR3C1 gene. The tremendous progress of molecular biology has enabled us to apply standard methods to investigate the molecular mechanisms of action of the mutant glucocorticoid receptors (GRs). We and others have identified and functionally characterized novel mutations causing Chrousos syndrome, while structural biology has enabled us to have a better understanding of how conformational changes of the receptor cause glucocorticoid resistance. In this review, we also present our results of the functional characterization of two recently described mutations, and we discuss the diagnostic approaches and therapeutic management of patients with Chrousos syndrome.

CONCLUSIONS

Although Chrousos syndrome is a rare condition, many clinical cases remain unrecognized for a long time. We recommend determination of the 24-h urinary free cortisol excretion and sequencing of the NR3C1 gene in patients with hyperandrogenism and/or hypertension of unknown origin.

Glucocorticoid Receptor β Acts as a Co-activator of T-Cell Factor 4 and Enhances Glioma Cell Proliferation

We previously reported that glucocorticoid receptor β (GRβ) regulates injury-mediated astrocyte activation and contributes to glioma pathogenesis via modulation of β-catenin/T-cell factor/lymphoid enhancer factor (TCF/LEF) transcriptional activity. The aim of this study was to characterize the mechanism behind cross-talk between GRβ and β-catenin/TCF in the progression of glioma. Here, we reported that GRβ knockdown reduced U118 and Shg44 glioma cell proliferation in vitro and in vivo. Mechanistically, we found that GRβ knockdown decreased TCF/LEF transcriptional activity without affecting β-catenin/TCF complex. Both GRα and GRβ directly interact with TCF-4, while only GRβ is required for sustaining TCF/LEF activity under hormone-free condition. GRβ bound to the N-terminus domain of TCF-4 its influence on Wnt signaling required both ligand- and DNA-binding domains (LBD and DBD, respectively). GRβ and TCF-4 interaction is enough to maintain the TCF/LEF activity at a high level in the absence of β-catenin stabilization. Taken together, these results suggest a novel cross-talk between GRβ and TCF-4 which regulates Wnt signaling and the proliferation in gliomas.