Chemotherapeutic effect of tamoxifen on temozolomide-resistant gliomas

CDS-DB, an omnibus for patient-derived gene expression signatures induced by cancer treatment

Patient-derived gene expression signatures induced by cancer treatment, obtained from paired pre- and post-treatment clinical transcriptomes, can help reveal drug mechanisms of action (MOAs) in cancer patients and understand the molecular response mechanism of tumor sensitivity or resistance. Their integration and reuse may bring new insights. Paired pre- and post-treatment clinical transcriptomic data are rapidly accumulating. However, a lack of systematic collection makes data access, integration, and reuse challenging. We therefore present the Cancer Drug-induced gene expression Signature DataBase (CDS-DB). CDS-DB has collected 78 patient-derived, paired pre- and post-treatment transcriptomic source datasets with uniformly reprocessed expression profiles and manually curated metadata such as drug administration dosage, sampling time and location, and intrinsic drug response status. From these source datasets, 2012 patient-level gene perturbation signatures were obtained, covering 85 therapeutic regimens, 39 cancer subtypes and 3628 patient samples. Besides data browsing, download and search, CDS-DB also supports single signature analysis (including differential gene expression, functional enrichment, tumor microenvironment and correlation analyses), signature comparative analysis and signature connectivity analysis. This provides insights into drug MOA and its heterogeneity in patients, drug resistance mechanisms, drug repositioning and drug (combination) discovery, etc. CDS-DB is available at http://cdsdb.ncpsb.org.cn/.

Tamoxifen as a modulator of CXCL12-CXCR4-CXCR7 chemokine axis: A breast cancer and glioblastoma view

The chemokine stromal cell-derived-factor 1 (SDF)-1/CXCL12 acts by binding to its receptors, the CXC-4 chemokine receptor (CXCR4) and the CXC-7 chemokine receptor (CXCR7). The binding of CXCL12 to its receptors results in downstream signaling that leads to cell survival, proliferation and migration of tumor cells. CXCL12 and CXCR4 are highly expressed in breast cancer (BC) and glioblastoma (GBM) compared to normal cells. High expression of this chemokine axis correlates with increased therapy resistance and grade, tumor spread and poorer prognosis in these tumors. Tamoxifen (TMX) is a selective estrogen receptor modulator (SERM) that inhibits the expression of estrogen-regulated genes, including growth and angiogenic factors secreted by tumor cells. Additionally, TMX targets several proteins, such as protein kinase C (PKC), phospholipase C (PLC), P-glycoprotein (PgP), phosphatidylinositol-3-kinase (PI3K) and ion channels. This drug showed promising antitumor activity against both BC and GBM cells. In this review, we discuss the role of the CXCL12-CXCR4-CXCR7 chemokine axis in BC and GBM tumor biology and propose TMX as a potential modulator of this axis in these tumors. TMX modulates the CXCL12-CXCR4-CXCR7 axis in BC, however, there are no studies on this in GBM. We propose that studying this axis in GBM cells/patients treated with TMX might be beneficial for these patients. TMX inhibits important signaling pathways in these tumors and the activation of this chemokine axis is associated with increased therapy resistance.

The role of PKN1 in glioma pathogenesis and the antiglioma effect of raloxifene targeting PKN1

PKN1 (protein kinase N1), a serine/threonine protein kinase family member, is associated with various cancers. However, the role of PKN1 in gliomas has rarely been studied. We suggest that PKN1 expression in glioma specimens is considerably upregulated and positively correlates with the histopathological grading of gliomas. Knocking down PKN1 expression in glioblastoma (GBM) cells inhibits GBM cell proliferation, invasion and migration and promotes apoptosis. In addition, yes-associated protein (YAP) expression, an essential effector of the Hippo pathway contributing to the oncogenic role of gliomagenesis, was also downregulated. In contrast, PKN1 upregulation enhances the malignant characteristics of GBM cells and simultaneously upregulates YAP expression. Therefore, PKN1 is a promising therapeutic target for gliomas. Raloxifene (Ralo), a commonly used selective oestrogen-receptor modulator to treat osteoporosis in postmenopausal women, was predicted to target PKN1 according to the bioinformatics team from the School of Mathematics, Tianjin Nankai University. We showed that Ralo effectively targets PKN1, inhibits GBM cells proliferation and migration and sensitizes GBM cells to the major chemotherapeutic drug, Temozolomide. Ralo also reverses the effect of PKN1 on YAP activation. Thus, we confirm that PKN1 contributes to the pathogenesis of gliomas and may be a potential target for Ralo adjuvant glioma therapy.

Potassium Ion Channels in Glioma: From Basic Knowledge into Therapeutic Applications

Ion channels, specifically those controlling the flux of potassium across cell membranes, have recently been shown to exhibit an important role in the pathophysiology of glioma, the most common primary central nervous system tumor with a poor prognosis. Potassium channels are grouped into four subfamilies differing by their domain structure, gating mechanisms, and functions. Pertinent literature indicates the vital functions of potassium channels in many aspects of glioma carcinogenesis, including proliferation, migration, and apoptosis. The dysfunction of potassium channels can result in pro-proliferative signals that are highly related to calcium signaling as well. Moreover, this dysfunction can feed into migration and metastasis, most likely by increasing the osmotic pressure of cells allowing the cells to initiate the "escape" and "invasion" of capillaries. Reducing the expression or channel blockage has shown efficacy in reducing the proliferation and infiltration of glioma cells as well as inducing apoptosis, priming several approaches to target potassium channels in gliomas pharmacologically. This review summarizes the current knowledge on potassium channels, their contribution to oncogenic transformations in glioma, and the existing perspectives on utilizing them as potential targets for therapy.

The location of estrogen receptor variant ER-α36 is associated with the invasion of glioblastoma

Glioblastoma (GBM) is the most common central nervous system tumor and is associated with poor outcomes. There have been no significant improvements in GBM mortality in recent decades. ER-α36 is a variant of ER-α66 that may be involved in carcinoma growth and proliferation via genomic and nongenomic mechanisms. This variant might play an essential role in tamoxifen resistance of several tumors. Previously, our laboratory found that ER-α36 is expressed in GBM and participates in proliferation; nevertheless, the role of ER-α36 in GBM invasion remains unknown. This study aimed to determine the effects of the ER-α36 modulator SNG162 on GBM growth and invasion. U251 cells, U87cells, and U87-36KD cells with knockdown of ER-α36 expression were cultured under the two-dimensional and the three-dimensional (3D) environments. GBM cells growth was examined by cell counting, flow cytometry, western blot, and MTT assays. Invasiveness was measured using confocal microscopy in the 3D environment. Growth of U87 cells with downregulated EGFR and ER-α36 expression was significantly reduced after treatment with 1 µM, 3 µM, and 5 µM of SNG162; growth inhibition in U251 cells was more potent than in U87 cells, although the expression level of ER-α36 in U251 cells was lower than in U87 cells. We found that 1 μM SNG162 suppressed E₂-induced MAPK/ERK pathway activation in U87 cells. We also showed that SNG162 inhibited U87 cells invasion; however, it did not significantly affect U251 and U87-36KD cells invasion using the 3D culture method. Finally, we determined that ER-α36 was expressed in the nucleus of invading GBM cells, and SNG162 significantly inhibited the expression of ER-α36 in these cells. SNG162 inhibited the expression of EGFR on cell membranes of non-invasive GBM cells. These results suggest that SNG162 could be a therapeutic agent for GBM by targeting ER-α36.

Ion Channels in Gliomas-From Molecular Basis to Treatment

Ion channels provide the basis for the nervous system's intrinsic electrical activity. Neuronal excitability is a characteristic property of neurons and is critical for all functions of the nervous system. Glia cells fulfill essential supportive roles, but unlike neurons, they also retain the ability to divide. This can lead to uncontrolled growth and the formation of gliomas. Ion channels are involved in the unique biology of gliomas pertaining to peritumoral pathology and seizures, diffuse invasion, and treatment resistance. The emerging picture shows ion channels in the brain at the crossroads of neurophysiology and fundamental pathophysiological processes of specific cancer behaviors as reflected by uncontrolled proliferation, infiltration, resistance to apoptosis, metabolism, and angiogenesis. Ion channels are highly druggable, making them an enticing therapeutic target. Targeting ion channels in difficult-to-treat brain tumors such as gliomas requires an understanding of their extremely heterogenous tumor microenvironment and highly diverse molecular profiles, both representing major causes of recurrence and treatment resistance. In this review, we survey the current knowledge on ion channels with oncogenic behavior within the heterogeneous group of gliomas, review ion channel gene expression as genomic biomarkers for glioma prognosis and provide an update on therapeutic perspectives for repurposed and novel ion channel inhibitors and electrotherapy.

Integrated analysis of inflammatory response subtype-related signature to predict clinical outcomes, immune status and drug targets in lower-grade glioma

Background: The inflammatory response in the tumor immune microenvironment has implications for the progression and prognosis in glioma. However, few inflammatory response-related biomarkers for lower-grade glioma (LGG) prognosis and immune infiltration have been identified. We aimed to construct and identify the prognostic value of an inflammatory response-related signature, immune infiltration, and drug targets for LGG.

Methods: The transcriptomic and clinical data of LGG samples and 200 inflammatory response genes were obtained from public databases. The LGG samples were separated into two inflammatory response-related subtypes based on differentially expressed inflammatory response genes between LGG and normal brain tissue. Next, inflammatory response-related genes (IRRGs) were determined through a difference analysis between the aforementioned two subtypes. An inflammatory response-related prognostic model was constructed using IRRGs by using univariate Cox regression and Lasso regression analyses and validated in an external database (CGGA database). ssGSEA and ESTIMATE algorithms were conducted to evaluate immune infiltration. Additionally, we performed integrated analyses to investigate the correlation between the prognostic signature and N 6-methyladenosine mRNA status, stemness index, and drug sensitivity. We finally selected MSR1 from the prognostic signature for further experimental validation.

Results: A total of nine IRRGs were identified to construct the prognostic signature for LGG. LGG patients in the high-risk group presented significantly reduced overall survival than those in the low-risk group. An ROC analysis confirmed the predictive power of the prognostic model. Multivariate analyses identified the risk score as an independent predictor for the overall survival. ssGSEA revealed that the immune status was definitely disparate between two risk subgroups, and immune checkpoints such as PD-1, PD-L1, and CTLA4 were significantly expressed higher in the high-risk group. The risk score was strongly correlated with tumor stemness and m6A. The expression levels of the genes in the signature were significantly associated with the sensitivity of tumor cells to anti-tumor drugs. Finally, the knockdown of MSR1 suppressed LGG cell migration, invasion, epithelial–mesenchymal transition, and proliferation.

Conclusion: The study constructed a novel signature composed of nine IRRGs to predict the prognosis, potential drug targets, and impact immune infiltration status in LGG, which hold promise for screening prognostic biomarkers and guiding immunotherapy for LGG.

Gallotannin-Enriched Fraction from Quercus infectoria Galls as an Antioxidant and Inhibitory Agent against Human Glioblastoma Multiforme

In recent years, herbal medicine has experienced rapid development in the search for alternative anticancer compounds. Various phytochemicals present in Quercus infectoria (QI) galls have been reported to trigger cytotoxic effects on many types of cancer cells. However, a specific active constituent of QI galls with the potential to inhibit highly invasive stage IV malignant brain tumor, glioblastoma multiforme (GBM), is yet to be discovered. In this study, a two-phase system composed of aqueous soxhlet extraction and methanolic enrichment fractionation was employed to extract an anticancer compound, gallotannin, from the QI galls. This optimized two-phase system successfully generated a fraction (F4) with ~71% gallotannin, verified by the TLC and HPLC assays. Astoundingly, this fraction showed significantly higher (~1.15-fold) antioxidant activities compared to its crude extract, as well as to a commercial synthetic pure gallotannin. The F4 was also found to significantly suppress GBM cell growth, better than the synthetic pure gallotannin and the QI gall crude extract, probably related to its significantly higher antioxidant property. Moreover, the inhibitory effects exerted by the F4 treatment on GBM cells were comparable to the effects of two clinically used chemo-drugs (Temozolomide and Tamoxifen), indicating its high efficiency in combating human cancer. In conclusion, this study pioneered the development of an optimized extraction procedure for enriched yield of the natural gallotannin metabolite from the galls of the QI medicinal plant with high antioxidant potential and inhibitory effects on human GBM cells.

Ion Channels as Therapeutic Targets in High Grade Gliomas

Simple Summary

Glioblastoma multiforme is an aggressive grade IV lethal brain tumour with a median survival of 14 months. Despite surgery to remove the tumour, and subsequent concurrent chemotherapy and radiotherapy, there is little in terms of effective treatment options. Because of this, exploring new treatment avenues is vital. Brain tumours are intrinsically electrically active; expressing unique patterns of ion channels, and this is a characteristic we can exploit. Ion channels are specialised proteins in the cell’s membrane that allow for the passage of positive and negatively charged ions in and out of the cell, controlling membrane potential. Membrane potential is a crucial biophysical signal in normal and cancerous cells. Research has identified that specific classes of ion channels not only move the cell through its cell cycle, thus encouraging growth and proliferation, but may also be essential in the development of brain tumours. Inhibition of sodium, potassium, calcium, and chloride channels has been shown to reduce the capacity of glioblastoma cells to grow and invade. Therefore, we propose that targeting ion channels and repurposing commercially available ion channel inhibitors may hold the key to new therapeutic avenues in high grade gliomas.

Abstract

Glioblastoma multiforme (GBM) is a lethal brain cancer with an average survival of 14–15 months even with exhaustive treatment. High grade gliomas (HGG) represent the leading cause of CNS cancer-related death in children and adults due to the aggressive nature of the tumour and limited treatment options. The scarcity of treatment available for GBM has opened the field to new modalities such as electrotherapy. Previous studies have identified the clinical benefit of electrotherapy in combination with chemotherapeutics, however the mechanistic action is unclear. Increasing evidence indicates that not only are ion channels key in regulating electrical signaling and membrane potential of excitable cells, they perform a crucial role in the development and neoplastic progression of brain tumours. Unlike other tissue types, neural tissue is intrinsically electrically active and reliant on ion channels and their function. Ion channels are essential in cell cycle control, invasion and migration of cancer cells and therefore present as valuable therapeutic targets. This review aims to discuss the role that ion channels hold in gliomagenesis and whether we can target and exploit these channels to provide new therapeutic targets and whether ion channels hold the mechanistic key to the newfound success of electrotherapies.

Glioblastoma chemoresistance: roles of the mitochondrial melatonergic pathway

Treatment-resistance is common in glioblastoma (GBM) and the glioblastoma stem-like cells (GSC) from which they arise. Current treatment options are generally regarded as very poor and this arises from a poor conceptualization of the biological underpinnings of GBM/GSC and of the plasticity that these cells are capable of utilizing in response to different treatments. A number of studies indicate melatonin to have utility in the management of GBM/GSC, both per se and when adjunctive to chemotherapy. Recent work shows melatonin to be produced in mitochondria, with the mitochondrial melatonergic pathway proposed to be a crucial factor in driving the wide array of changes in intra- and inter-cellular processes, as well as receptors that can be evident in the cells of the GBM/GSC microenvironment. Variations in the enzymatic conversion of N-acetylserotonin (NAS) to melatonin may be especially important in GSC, as NAS can activate the tyrosine receptor kinase B to increase GSC survival and proliferation. Consequently, variations in the NAS/melatonin ratio may have contrasting effects on GBM/GSC survival. It is proposed that mitochondrial communication across cell types in the tumour microenvironment is strongly driven by the need to carefully control the mitochondrial melatonergic pathways across cell types, with a number of intra- and inter-cellular processes occurring as a consequence of the need to carefully regulate the NAS/melatonin ratio. This better integrates previously disparate data on GBM/GSC as well as providing clear future research and treatment options.

Protein modification by thiolactone homocysteine chemistry: a multifunctionalized human serum albumin theranostic

As the most abundant protein with a variety of physiological functions, albumin has been used extensively for the delivery of therapeutic molecules. Thiolactone chemistry provides a powerful tool to prepare spin-labeled albumin-based multimodal imaging probes and therapeutic agents. We report the synthesis of a tamoxifen homocysteine thiolactone derivative and its use in thiol-'click' chemistry to prepare multi-functionalized serum albumin. The released sulfhydryl group of the homocysteine functional handle was labeled with a nitroxide reagent to prepare a spin-labeled albumin-tamoxifen conjugate confirmed by MALDI-TOF-MS, EPR spectroscopy, UV-vis and fluorescent emission spectra. This is the basis for a novel multimodal tamoxifen-albumin theranostic with a significant (dose-dependent) inhibitory effect on the proliferation of malignant cells. The response of human glioblastoma multiforme T98G cells and breast cancer MCF-7 cells to tamoxifen and its albumin conjugates was different in tumor cells with different expression level of ERα in our experiments. These results provide further impetus to develop a serum protein for delivery of tamoxifen to cancer cells.

High Concentrations of Boric Acid Trigger Concentration-Dependent Oxidative Stress, Apoptotic Pathways and Morphological Alterations in DU-145 Human Prostate Cancer Cell Line

Boric acid is known to regulate the proliferation of cancer cells. Prostate cancer is among the types of cancer with high mortality in men. There are a few numbers of studies investigating the effects of boric acid on prostate cancer cells. The objective of the present study was to assess the effects of boric acid at concentrations higher than that can be achieved in blood by dietary intake on DU-145 human prostate cancer cells for 24 h. Firstly, we determined the cytotoxic activity of boric acid (0 to 12.5 mM) on DU-145 human prostate cancer cells by using 3-(4, 5-dimethylthiazol, 2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) and defined the IC50 concentration of boric acid. Then, by employing the doses found in MTT, the levels of antioxidant-oxidant molecules and apoptotic proteins were measured and morphological changes were evaluated. We have concluded that boric acid caused oxidative stress, inhibition of cell growth, apoptosis, and morphological alterations in a concentration-dependent manner in DU-145 cells. Furthermore, treatments with increasing boric acid concentrations decreased the antioxidant levels in cells. We actually revealed that boric acid, known as an antioxidant, may prevent cell proliferation by acting as an oxidant in certain doses. Although the high IC50 concentration of boric acid is perceived to be negative, we think it provides important background for subsequent studies.

Risk of primary brain tumour after breast cancer

INTRODUCTION

Cancer registry data in the USA indicated that women diagnosed with breast cancer before the age of 40 were at increased risk of a new primary tumour within the brain and women aged 50 years or above were at lower risk than expected. Our aim was to investigate if similar results could be found in Danish population-based data, considering an explanatory role of hormonal status.

METHODS

Our study cohort included all women diagnosed with breast cancer below the age of 60 between 1978 and 2013 in Denmark. A total of 47,920 women were followed up in the Danish Cancer Registry for primary brain cancer. Standardized incidence ratios (observed/expected cases (O/E)) were used to estimate the risk of getting a primary brain tumour in the breast cancer cohort.

RESULTS

Data indicated an increased tendency of brain cancer following breast cancer at ages below 60 years (O/E = 1.24). For premenopausal women (age <49 at the diagnosis of breast cancer) the O/E was 1.25. Stratifying by time of breast cancer diagnosis, we observed an increased risk of being diagnosed with a brain tumour among women aged 49 years or younger at breast cancer diagnosis between 2004 and 2013.

CONCLUSION

The results indicate an increased tendency of developing a primary brain tumour in women with previous breast cancer history. Whereas the finding in premenopausal women is in line with the SEER data, the finding among postmenopausal is not. Primary brain tumours in breast cancer patients call for research in genetics and hormones to establish common risk factors.

Role of liraglutide in brain repair promotion through Sirt1-mediated mitochondrial improvement in stroke

Brain repair, especially axonal sprouting, is critical to restore motor function in disabled stroke patients. Liraglutide (LG) is a new kind of long-acting analogue of glucagon-like peptide-1 (GLP-1) and has potential protective effects in stroke. The mitochondria participate in brain repair after cerebral injury. However, the mechanism of the effect of LG on brain repair and its potential influence on mitochondria in stroke remains obscure. Here, in focal cerebral cortical ischemic mice model, LG improved the motor functional recovery and promoted axonal sprouting by restoring the activities of isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and succinate dehydrogenase. Moreover, LG remarkably increased the cell survival rate and revived the NeuN and GAP-43 levels in cortical neurons under hydrogen peroxide (H₂ O₂ ) exposure. It was also observed that LG reduced the generation of reactive oxygen species, stabilized the mitochondrial membrane potential, enhanced the levels of adenosine triphosphate, enhanced activities of mitochondrial complex-I, and decreased protein expression levels of fission-1 in H₂ O₂ -injured cortical neurons. Additionally, LG suppressed the expressions of sirtuin 1 (Sirt1) in cortical neurons exposed to H₂ O₂ . Furthermore, knockdown of Sirt1 by short interfering RNA facilitated the LG-mediated mitochondrial protection in cortical neurons under H₂ O₂ . Collectively, this data from the present study illustrated that LG exerted a promoting influence on brain repair, after cerebral ischemic injury, through Sirt1-mediated mitochondrial improvement.

Design, synthesis, and biological evaluation of lipophilically modified bisphenol Z derivatives

In the present study, a small library of bisphenol Z (BPZ) derivatives was synthesized and investigated for anti-proliferative effects in cultured breast and glioblastoma cell lines. Synthesized BPZ derivatives varied in molecular size, polarity, and lipophilicity. Of the 8 derivatives tested, compounds 4 and 6, both of which displayed the highest degree of lipophilicity, were most active at inducing cell death as determined by the XTT assay. Cell membranes were interrogated using trypan blue staining and were shown to remain intact during treatments with 4 and 6. Activation of caspase enzymes (3 and/or 7) was noted to occur following treatment with compound 4. Polar BPZ derivatives, those with a substituted amine or alcohol, were devoid of any inhibitory or proliferative effects. The remaining derivatives seem to lack sufficient lipophilicity to execute an overt toxic effect. Our results suggest that increasing the lipophilic character of BPZ enhances the cytotoxic effects.

The role of caveolin-1 in tumors of the brain - functional and clinical implications

BACKGROUND

Caveolin-1 (cav-1) is the major structural protein of caveolae, the flask-shaped invaginations of the plasma membrane mainly involved in cell signaling. Today, cav-1 is believed to play a role in a variety of disease processes including cancer, owing to the variations of its expression in association with tumor progression, invasive behavior, metastasis and therapy resistance. Since first detected in the brain, a number of studies has particularly focused on the role of cav-1 in the various steps of brain tumorigenesis. In this review, we discuss the different roles of cav-1 and its contributions to the molecular mechanisms underlying the pathobiology and natural behavior of brain tumors including glial, non-glial and metastatic subtypes. These contributions could be attributed to its co-localization with important players in tumorigenesis within the lipid-enriched domains of the plasma membrane. In that regard, the ability of cav-1 to interact with various cell signaling molecules as well as the impact of caveolae depletion on important pathways acting in brain tumor pathogenesis are noteworthy. We also discuss conversant causes hampering the treatment of malignant glial tumors such as limited transport of chemotherapeutics across the blood tumor barrier and resistance to chemoradiotherapy, by focusing on the molecular fundamentals involving cav-1 participation.

CONCLUSIONS

Cav-1 has the potential to pivot the molecular basis underlying the pathobiology of brain tumors, particularly the malignant glial subtype. In addition, the regulatory effect of cav-1-dependent and caveola-mediated transcellular transport on the permeability of the blood tumor barrier could be of benefit to overcome the restricted transport across brain barriers when applying chemotherapeutics. The association of cav-1 with tumors of the brain other than malignant gliomas deserves to be underlined, as well given the evidence suggesting its potential in predicting tumor grade and recurrence rates together with determining patient prognosis in oligodendrogliomas, ependymomas, meningiomas, vestibular schwannomas and brain metastases.

Estrogen receptor variant ER-α36 promotes tamoxifen agonist activity in glioblastoma cells

Glioblastoma (GBM) is a highly infiltrative and malignant primary brain tumor. Despite aggressive therapy, patients with GBM have a dismal prognosis with median survival of approximately 1 year. Tamoxifen (TAM), a selective estrogen receptor modulator (SERM), has been used to treat GBM for many years. ER‐α36 is a novel variant of estrogen receptor‐alpha66 (ER‐α66) and can mediate cell proliferation through estrogen or anti‐estrogen signaling in different cancer cells. Previously, we found that ER‐α36 was highly expressed in GBM and was involved in the tamoxifen sensitivity of glioblastoma cells. However, the molecular mechanism responsible has not been well established. Here, we found that ER‐α36 is highly expressed in glioblastoma specimens. We further found that ER‐α36 knockdown increased sensitivity of glioblastoma U87 cells to TAM and decreased autophagy in these cells. However, ER‐α36 overexpression decreased TAM sensitivity and induced autophagy. We also established TAM‐resistant glioblastoma U251 cells by a long‐term culture in TAM‐containing medium and found that TAM‐resistant cells showed a six‐fold increase of ER‐α36 mRNA expression and elevated basal autophagy. ER‐α36 knockdown in these TAM‐resistant cells restored TAM sensitivity. In addition, we recapitulated the physiologically relevant tumor microenvironment in an integrated microfluidic device, and U87 cells were treated with a gradient of TAM. We found that ER‐α36 expression is consistent with autophagy protein P62 in a three‐dimensional microenvironment. In summary, these results indicate that ER‐α36 contributes to tamoxifen resistance in glioblastoma cells presumably through regulation of autophagy.

A Dexamethasone-regulated Gene Signature Is Prognostic for Poor Survival in Glioblastoma Patients

BACKGROUND

Dexamethasone is reported to induce both tumor-suppressive and tumor-promoting effects. The purpose of this study was to identify the genomic impact of dexamethasone in glioblastoma stem cell (GSC) lines and its prognostic value; furthermore, to identify drugs that can counter these side effects of dexamethasone exposure.

METHODS

We utilized 3 independent GSC lines with tumorigenic potential for this study. Whole-genome expression profiling and pathway analyses were done with dexamethasone-exposed and control cells. GSCs were also co-exposed to dexamethasone and temozolomide. Risk scores were calculated for most affected genes, and their associations with survival in The Cancer Genome Atlas and Repository of Molecular Brain Neoplasia Data databases. In silico Connectivity Map analysis identified camptothecin as antagonist to dexamethasone-induced negative effects.

RESULTS

Pathway analyses predicted an activation of dexamethasone network (z-score: 2.908). Top activated canonical pathways included "role of breast cancer 1 in DNA damage response" (P=1.07E-04). GSCs were protected against temozolomide-induced apoptosis when coincubated with dexamethasone. Altered cellular functions included cell movement, cell survival, and apoptosis with z-scores of 2.815, 5.137, and -3.122, respectively. CCAAT/enhancer binding protein beta (CEBPB) was activated in a dose dependent manner specifically in slow-dividing "stem-like" cells. CEBPB was activated in dexamethasone-treated orthotopic tumors. Patients with high risk scores had significantly shorter survival. Camptothecin was validated as potential partial neutralizer of dexamethasone-induced oncogenic effects.

CONCLUSIONS

Dexamethasone exposure induces a genetic program and CEBPB expression in GSCs that adversely affects key cellular functions and response to therapeutics. High risk scores associated with these genes have negative prognostic value in patients. Our findings further suggest camptothecin as a potential neutralizer of adverse dexamethasone-mediated effects.

The clinical significance of QT prolongation associated with tamoxifen: A review of the literature

Objective To review the literature discussing QT prolongation associated with the use of tamoxifen in order to evaluate the clinical significance. Data sources A search of PubMed (1946 to 2017), MEDLINE (1946 to 2017) and EMBASE (1947 to 2017) was performed using a combination of the following search terms: tamoxifen, estrogen antagonist, selective estrogen receptor modulator, QT prolongation, QT interval, long QT syndrome and torsades de pointes. All searches were limited to human subjects. Reference lists of the literature found were also reviewed but did not reveal any further articles. Study selection Articles reviewed were relating to humans only and included clinical trials and case reports that mentioned QT prolongation in association with the use of tamoxifen. Data synthesis It can be common for patients on tamoxifen to also be on a number of different medications being used to treat comorbid medical conditions. Such combinations of medications increase the potential risk for drug interactions, such as drug-induced QT prolongation. Tamoxifen is often flagged by tertiary drug information sources as a drug with indeterminate effects on the QT interval. However, the risk may be elevated when combined with other QT-prolonging agents. A total of five publications were identified, including two phase I clinical trials and three case reports, which discussed the association between tamoxifen and QT prolongation. Conclusions Tertiary drug information sources identify tamoxifen as an agent that may cause QT prolongation when used in combination with other QT-prolonging agents. However, based on the limited number of published reports found, it would suggest that the use of tamoxifen concurrently with other agents known to prolong the QT interval is likely to be of low risk for causing a clinically significant QT-prolonging event, especially at a dose of 20 mg daily.

Glioblastoma entities express subtle differences in molecular composition and response to treatment

Glioblastoma (GBM) is a grade IV astrocytoma. GBM patients show resistance to chemotherapy such as temozolomide (TMZ), the gold standard treatment. In order to simulate the molecular mechanisms behind the different chemotherapeutic responses in GBM patients we compared the cellular heterogeneity and chemotherapeutic resistance mechanisms in different GBM cell lines. We isolated and characterized a human GBM cell line obtained from a GBM patient, named GBM11. We studied the GBM11 behaviour when treated with Tamoxifen (TMX) that, among other functions, is a protein kinase C (PKC) inhibitor, alone and in combination with TMZ in comparison with the responses of U87 and U118 human GBM cell lines. We evaluated the cell death, cell cycle arrest and cell proliferation, mainly through PKC expression, by flow cytometry and western blot analysis and, ultimately, cell migration capability and f-actin filament disorganization by fluorescence microscopy. We demonstrated that the constitutive activation of p-PKC seems to be one of the main metabolic implicated on GBM malignancy. Despite of its higher resistance, possibly due to the overexpression of P-glycoprotein and stem-like cell markers, GBM11 cells presented a subtle different chemotherapeutic response compared to U87 and U118 cells. The GBM11, U87, U118 cell lines show subtle molecular differences, which clearly indicate the characterization of GBM heterogeneity, one of the main reasons for tumor resistance. The adding of cellular heterogeneity in molecular behaviour constitutes a step closer in the understanding of resistant molecular mechanisms in GBM, and can circumvents the eventual impaired therapy.

Glioblastoma-derived cells in vitro unveil the spectrum of drug resistance capability - comparative study of tumour chemosensitivity in different culture systems

Resistance to cancer drugs is a complex phenomenon which could be influenced by in vitro conditions. However, tumour-derived cell cultures are routinely used for studies related to mechanisms of drug responsiveness or the search for new therapeutic approaches. The purpose of our work was to identify the potential differences in drug resistance and response to treatment of glioblastoma with the use of three in vitro models: traditional adherent culture, serum-free spheroid culture and novel adherent serum-free culture.The experimental models were evaluated according to 'stemness state' and epithelial-to-mesenchymal transition (EMT) status, invasion capability and their expression pattern of genes related to the phenomenon of tumour drug resistance. Additionally, the response to drug treatments of three different culture models was compared with regard to the type of cell death.Multi-gene expression profiling revealed differences between examined culture types with regard to the expression pattern of the selected genes. Functionally, the examined genes were related to drug resistance and metabolism, DNA damage and repair and cell cycle control, and included potential therapeutic targets.Cytotoxicity analyses confirmed that environmental factors can influence not only the molecular background of glioblastoma drug-resistance and efficiency of treatment, but also the mechanisms/pathways of cell death, which was reflected by a distinct intensification of apoptosis and autophagy observed in particular culture models. Our results suggest that parallel exploitation of different in vitro experimental models can be used to reveal the spectrum of cancer cell resistance capability, especially regarding intra-heterogeneous glioblastomas.

Aquaporin 4-Mediated Glutamate-Induced Astrocyte Swelling Is Partially Mediated through Metabotropic Glutamate Receptor 5 Activation

Astrocytes are one of the most abundant cell types in the mammalian central nervous system (CNS), and astrocyte swelling is the primary event associated with brain edema. Glutamate, the principal excitatory amino acid neurotransmitter in the CNS, is released at high levels after brain injury including cerebral ischemia. This leads to astrocyte swelling, which we previously demonstrated is related to metabotropic glutamate receptor (mGluR) activation. Aquaporin 4 (AQP4), the predominant water channel in the brain, is expressed in astrocyte endfeet and plays an important role in brain edema following ischemia. Studies recently showed that mGluR5 is also expressed on astrocytes. Therefore, it is worth investigating whether AQP4 mediates the glutamate-induced swelling of astrocytes via mGluR5. In the present study, we found that 1 mM glutamate induced astrocyte swelling, quantified by the cell perimeter, but it had no effect on astrocyte viability measured by the cell counting kit-8 (CCK-8) and lactate dehydrogenase (LDH) assays. Quantitative reverse transcription polymerase chain reaction analyses revealed that AQP4, among AQP1, 4, 5, 9 and 11, was the main molecular expressed in cultured astrocytes. Glutamate-induced cell swelling was accompanied by a concentration-dependent change in AQP4 expression. Furthermore, RNAi technology revealed that AQP4 gene silencing inhibited glutamate-induced astrocyte swelling. Moreover, we found that mGluR5 expression was greatest among the mGluRs in cultured astrocytes and was co-expressed with AQP4. Activation of mGluR5 in cultured astrocytes using (S)-3,5-dihydroxyphenylglycine (DHPG), an mGluR5 agonist, mimicked the effect of glutamate. This effect was abolished by co-incubation with the mGluR5 antagonist fenobam but was not influenced by DL-threo-β-benzyloxyaspartic acid (DL-TBOA), a glutamate transporter inhibitor. Finally, experiments in a rat model of transient middle cerebral artery occlusion (tMCAO) revealed that co-expression of mGluR5 and AQP4 was increased in astrocyte endfeet around capillaries in the penumbra, and this was accompanied by brain edema. Collectively, these results suggest that glutamate induces cell swelling and alters AQP4 expression in astrocytes via mGluR5 activation, which may provide a novel approach for the treatment of edema following brain injury.

Sulfasalazine intensifies temozolomide cytotoxicity in human glioblastoma cells

Temozolomide (TMZ) is an alkylating agent used to treat glioblastoma. This tumor type synthesizes the antioxidant glutathione through system X c (-) , which is inhibited by sulfasalazine (SAS). We exposed A172 and T98G human glioblastoma cells to a presumably clinically relevant concentration of TMZ (25 µM) and/or 0.5 mM SAS for 1, 3, or 5 days and assessed cell viability. For both cell lines, TMZ alone did not alter viability at any time point, while the coadministration of TMZ and SAS significantly reduced cell viability after 5 days. The drug combination exerted a synergistic effect on A172 cells after 3 and 5 days. Therefore, this particular lineage was subjected to complementary analyses on the genetic (transcriptome) and functional (glutathione and proliferating cell nuclear antigen (PCNA) protein) levels. Cellular pathways containing differentially expressed genes related to the cell cycle were modified by TMZ alone. On the other hand, SAS regulated pathways associated with glutathione metabolism and synthesis, irrespective of TMZ. Moreover, SAS, but not TMZ, depleted the total glutathione level. Compared with the vehicle-treated cells, the level of PCNA protein was lower in cells treated with TMZ alone or in combination with SAS. In conclusion, our data showed that the association of TMZ and SAS is cytotoxic to T98G and A172 cells, thus providing useful insights for improving TMZ clinical efficacy through testing this novel drug combination. Moreover, the present study not only reports original information on differential gene expression in glioblastoma cells exposed to TMZ and/or SAS but also describes an antiproliferative effect of TMZ, which has not yet been observed in A172 cells.

Topological robustness analysis of protein interaction networks reveals key targets for overcoming chemotherapy resistance in glioma

Biological networks display high robustness against random failures but are vulnerable to targeted attacks on central nodes. Thus, network topology analysis represents a powerful tool for investigating network susceptibility against targeted node removal. Here, we built protein interaction networks associated with chemoresistance to temozolomide, an alkylating agent used in glioma therapy, and analyzed their modular structure and robustness against intentional attack. These networks showed functional modules related to DNA repair, immunity, apoptosis, cell stress, proliferation and migration. Subsequently, network vulnerability was assessed by means of centrality-based attacks based on the removal of node fractions in descending orders of degree, betweenness, or the product of degree and betweenness. This analysis revealed that removing nodes with high degree and high betweenness was more effective in altering networks' robustness parameters, suggesting that their corresponding proteins may be particularly relevant to target temozolomide resistance. In silico data was used for validation and confirmed that central nodes are more relevant for altering proliferation rates in temozolomide-resistant glioma cell lines and for predicting survival in glioma patients. Altogether, these results demonstrate how the analysis of network vulnerability to topological attack facilitates target prioritization for overcoming cancer chemoresistance.

Alternative mitochondrial electron transfer for the treatment of neurodegenerative diseases and cancers: Methylene blue connects the dots

Brain has exceptional high requirement for energy metabolism with glucose as the exclusive energy source. Decrease of brain energy metabolism and glucose uptake has been found in patients of Alzheimer's, Parkinson's and other neurodegenerative diseases, providing a clear link between neurodegenerative disorders and energy metabolism. On the other hand, cancers, including glioblastoma, have increased glucose uptake and rely on aerobic glycolysis for energy metabolism. The switch of high efficient oxidative phosphorylation to low efficient aerobic glycolysis pathway (Warburg effect) provides macromolecule for biosynthesis and proliferation. Current research indicates that methylene blue, a century old drug, can receive electron from NADH in the presence of complex I and donates it to cytochrome c, providing an alternative electron transfer pathway. Methylene blue increases oxygen consumption, decrease glycolysis, and increases glucose uptake in vitro. Methylene blue enhances glucose uptake and regional cerebral blood flow in rats upon acute treatment. In addition, methylene blue provides protective effect in neuron and astrocyte against various insults in vitro and in rodent models of Alzheimer's, Parkinson's, and Huntington's disease. In glioblastoma cells, methylene blue reverses Warburg effect by enhancing mitochondrial oxidative phosphorylation, arrests glioma cell cycle at s-phase, and inhibits glioma cell proliferation. Accordingly, methylene blue activates AMP-activated protein kinase, inhibits downstream acetyl-coA carboxylase and cyclin-dependent kinases. In summary, there is accumulating evidence providing a proof of concept that enhancement of mitochondrial oxidative phosphorylation via alternative mitochondrial electron transfer may offer protective action against neurodegenerative diseases and inhibit cancers proliferation.