Swelling‐induced chloride current in glioblastoma proliferation,migration, and invasion

Glioblastoma (GBM) remains as the most common and aggressive brain tumor. The survival of GBM has been linked to the aberrant activation of swelling‐induced chloride current I_Cl,swell. In this study, we investigated the effects of I_Cl,swell on cell viability, proliferation, and migration in the human GBM cell lines, U251 and U87, using a combination of patch clamp electrophysiology, MTT, colony formation, wound healing assays and Western immunoblotting. First, we showed that the specific inhibitor of I_Cl,swell, DCPIB, potently reduced the I_Cl,swell in U87 cells. Next, in both U87 and U251 cells, we found that DCPIB reduced GBM viability, proliferation, colony formation, migration, and invasion. In addition, our Western immunoblot assay showed that DCPIB‐treated U251 cells had a reduction in JAK2, STAT3, and Akt phosphorylation, thus, suggesting that DCPIB potentially suppresses GBM functions through inhibition of the JAK2/STAT3 and PI3K/Akt signaling pathways. Therefore, the I_Cl,swell may be a potential drug target for GBM.     

The curry spice curcumin selectively inhibits cancer cells growth in vitro and in preclinical model of glioblastoma

Previous studies suggested that curcumin is a potential agent against glioblastomas (GBMs). However, the in vivo efficacy of curcumin in gliomas remains not established. In this work, we examined the mechanisms underlying apoptosis, selectivity, efficacy and safety of curcumin from in vitro (U138MG, U87, U373 and C6 cell lines) and in vivo (C6 implants) models of GBM. In vitro, curcumin markedly inhibited proliferation and migration and induced cell death in liquid and soft agar models of GBM growth. Curcumin effects occurred irrespective of the p53 and PTEN mutational status of the cells. Interestingly, curcumin did not affect viability of primary astrocytes, suggesting that curcumin selectivity targeted transformed cells. In U138MG and C6 cells, curcumin decreased the constitutive activation of PI3K/Akt and NFkappaB survival pathways, down-regulated the antiapoptotic NFkappaB-regulated protein bcl-xl and induced mitochondrial dysfunction as a prelude to apoptosis. Cells developed an early G2/M cell cycle arrest followed by sub-G1 apoptosis and apoptotic bodies formation. Caspase-3 activation occurred in the p53-normal cell type C6, but not in the p53-mutant U138MG. Besides its apoptotic effect, curcumin also synergized with the chemotherapeutics cisplatin and doxorubicin to enhance GBM cells death. In C6-implanted rats, intraperitoneal curcumin (50 mg kg(-1) d(-1)) decreased brain tumors in 9/11 (81.8%) animals against 0/11 (0%) in the vehicle-treated group. Importantly, no evidence of tissue (transaminases, creatinine and alkaline phosphatase), metabolic (cholesterol and glucose), oxidative or hematological toxicity was observed. In summary, data presented here suggest curcumin as a potential agent for therapy of GBMs.     

Exaggerated inflammatory responses mediated by Burkholderia cenocepacia in human macrophages derived from Cystic fibrosis patients

Glioblastoma (GBM) is a highly aggressive cancer type characterized by intense neovascularization. Several lines of evidence indicate that blood clotting enzymes play an important role in the tumor microenvironment, mainly through the activation of protease-activated receptors (PAR). In particular, PAR1 and PAR2 isoforms may activate signal transduction pathways that promote a number of pro-tumoral responses. However, little is known concerning the role of PAR1/PAR2 in GBM progression. In this study, we investigated the expression and function of PAR1 and PAR2 in the human GBM cell lines A172 and U87-MG. We also evaluated the effect of agonist peptides for PAR1 (PAR1-AP) and PAR2 (PAR2-AP) on signaling pathways and the expression of vascular endothelial growth factor (VEGF). Immunoblotting assays showed that A172 and U87-MG constitutively express PAR1 and PAR2. Treatment of GBM cells with PAR1-AP or PAR2-AP enhanced Akt (protein kinase B) and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation in a time-dependent manner. LY29042 and PD98059, inhibitors of the phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways, decreased PAR-mediated activation of Akt and ERK1/2, respectively. In addition, we observed that PAR2, but not PAR1, activation increased VEGF secretion in U87-MG and A172 cells. Notably, only PD98059 reduced PAR2-mediated VEGF production by GBM cells. Our results suggest that PAR2 modulates VEGF production through the MAPK/ERK1/2 pathway, and not the PI3K/Akt pathway, in human GBM cell lines. Therefore, the PAR2/MAPK signaling axis might be regarded as a relevant target for adjuvant treatment of GBM with a possible impact on tumor angiogenesis.     

TMBIM1 promotes proliferation and attenuates apoptosis in glioblastoma cells by targeting the p38 MAPK signalling pathway

Glioblastoma multiforme (GBM) is the most common and most fatal primary malignant brain tumour in adults. The average survival time of patients after diagnosis is only 12–15 months. And its characteristics of excessive proliferation and apoptosis evasion play a crucial role in the poor prognosis of patients. Therefore, it is worth investigating the molecular mechanism of GBM to find an effective therapeutic target to overcome the dilemma. In the current study, Transmembrane BAX inhibitor motif containing 1 (TMBIM1) was highly expressed in GBM tissues and high TMBIM1 expression in GBM cell lines (U87 and U251) could promote cell proliferation and inhibit cell cycle arrest. In addition, TMBIM1 could significantly attenuate GBM cell apoptosis and decrease the sensitivity of GBM cells to temozolomide (TMZ). In terms of the molecular mechanism, we revealed that TMBIM1 interferes with the p38/MAPK pathway by inhibiting p38 phosphorylation to promote cell proliferation and attenuate cell apoptosis. In vivo experiments showed that the survival time of mice in TMBIM1 knockdown group was significantly prolonged. Our discovery provided an important basis for future intensive molecular mechanism research in GBM and presented a potential target for the treatment of GBM.     

The Synergistic Effect of Combination Progesterone and Temozolomide on Human Glioblastoma Cells

Glioblastoma multiforme (GBM) is the most common and most aggressive malignant brain tumor. Despite optimal treatment and evolving standard of care, the median survival of patients diagnosed with GBM is only 12–15 months. In this study, we combined progesterone (PROG) and temozolomide (TMZ), a standard chemotherapeutic agent for human GBM, to test whether PROG enhances the antitumor effects of TMZ and reduces its side effects. Two WHO grade IV human GBM cells lines (U87MG and U118MG) and primary human dermal fibroblasts (HDFs) were repeatedly exposed to PROG and TMZ either alone or in combination for 3 and 6 days. Cell death was measured by MTT reduction assay. PROG and TMZ individually induced tumor cell death in a dose-dependent manner. PROG at high doses produced more cell death than TMZ alone. When combined, PROG enhanced the cell death-inducing effect of TMZ. In HDFs, PROG did not reduce viability even at the same high cytotoxic doses, but TMZ did so in a dose-dependent manner. In combination, PROG reduced TMZ toxicity in HDFs. PROG alone and in combination with TMZ suppressed the EGFR/PI3K/Akt/mTOR signaling pathway and MGMT expression in U87MG cells, thus suppressing cell proliferation. PROG and TMZ individually reduced cell migration in U87MG cells but did so more effectively in combination. PROG enhances the cytotoxic effects of TMZ in GBM cells and reduces its toxic side effects in healthy primary cells.     

MALT1 is a potential therapeutic target in glioblastoma and plays a crucial role in EGFR‐induced NF‐κB activation

Glioblastoma multiforme (GBM) is the most common malignant tumour in the adult brain and hard to treat. Nuclear factor κB (NF‐κB) signalling has a crucial role in the tumorigenesis of GBM. EGFR signalling is an important driver of NF‐κB activation in GBM; however, the correlation between EGFR and the NF‐κB pathway remains unclear. In this study, we investigated the role of mucosa‐associated lymphoma antigen 1 (MALT1) in glioma progression and evaluated the anti‐tumour activity and effectiveness of MI‐2, a MALT1 inhibitor in a pre‐clinical GBM model. We identified a paracaspase MALT1 that is involved in EGFR‐induced NF‐kB activation in GBM. MALT1 deficiency or inhibition significantly affected the proliferation, survival, migration and invasion of GBM cells both in vitro and in vivo. Moreover, MALT1 inhibition caused G1 cell cycle arrest by regulating multiple cell cycle–associated proteins. Mechanistically, MALTI inhibition blocks the degradation of IκBα and prevents the nuclear accumulation of the NF‐κB p65 subunit in GBM cells. This study found that MALT1, a key signal transduction cascade, can mediate EGFR‐induced NF‐kB activation in GBM and may be potentially used as a novel therapeutic target for GBM.     

A Potential Role for the Inhibition of PI3K Signaling in Glioblastoma Therapy

Glioblastoma multiforme (GBM) is the most common primary brain tumor and among the most difficult to treat malignancies per se. In almost 90% of all GBM alterations in the PI3K/Akt/mTOR have been found, making this survival cascade a promising therapeutic target, particular for combination therapy that combines an apoptosis sensitizer, such as a pharmacological inhibitor of PI3K, with an apoptosis inducer, such as radio- or chemotherapy. However, while in vitro data focusing mainly on established cell lines has appeared rather promising, this has not translated well to a clinical setting. In this study, we analyze the effects of the dual kinase inhibitor PI-103, which blocks PI3K and mTOR activity, on three matched pairs of GBM stem cells/differentiated cells. While blocking PI3K-mediated signaling has a profound effect on cellular proliferation, in contrast to data presented on two GBM cell lines (A172 and U87) PI-103 actually counteracts the effect of chemotherapy. While we found no indications for a potential role of the PI3K signaling cascade in differentiation, we saw a clear and strong contribution to cellular motility and, by extension, invasion. While blocking PI3K-mediated signaling concurrently with application of chemotherapy does not appear to be a valid treatment option, pharmacological inhibitors, such as PI-103, nevertheless have an important place in future therapeutic approaches.     

IL‐17A promotes cell migration and invasion of glioblastoma cells via activation of PI3K/AKT signalling pathway

Glioblastomas (GBMs) are the most common of both benign and malignant primary brain tumours, in which the inflammatory and immunologic abnormalities are involved. Interleukin‐17A (IL‐17A) plays an important role in various inflammatory diseases and cancers. Several recent studies revealed that the expression of IL‐17A was overexpressed in human GBMs tissue. However, the accurate role of IL‐17A in GBMs remains unclear. In this study, we aimed to explore the effect of IL‐17A on cell migration and invasion of GBMs and the mechanism by which the effects occurred. We found that exogenous IL‐17A promoted significantly cell migration and invasion abilities in two GBMs cell lines (U87MG and U251) in a time‐dependent manner. In addition, the protein expressions of PI3K, Akt and MMP‐2/9 were increased in the GBMs cells challenged by IL‐17A. Furthermore, a tight junction protein ZO‐1 was down‐regulated but Twist and Bmi1 were up‐regulated. Treatment with a PI3K inhibitor (LY294002) significantly reduced the abilities of both migration and invasion in U87MG and U251 cells. LY294002 treatment also attenuated the IL‐17A causing increases of protein levels of PI3K, AKT, MMP‐2/9, Twist and the decreases of protein level of ZO‐1 in the U87MG and U251 cells. Taken together, we concluded that IL‐17A promotes the GBM cells migration and invasion via PI3K/AKT signalling pathway. IL‐17A and its related signalling pathways may be potential therapeutic targets for GBM.     

Suppressing H19 Modulates Tumorigenicity and Stemness in U251 and U87MG Glioma Cells

Glioblastoma multiforme (GBM) is a type of malignant carcinoma found in the brain. Its high frequency of occurrence and poor survival rate have garnered much research attention in recent years. Long non-coding RNAs (lncRNAs) are known to be related to the formation and progression of several cancer types by both promoting and suppressing tumor transformation. H19 is one such lncRNA and has been shown to be upregulated in a few types of cancer. In this study, we discovered that the expression of H19 increased in GBM cell lines. H19 knocked down GBM cells also displayed decreased cellular proliferation and a higher apoptosis rate when induced by temozolomide. Interestingly, the GBM cell lines U87MG and U251 were found to express cancer stem cell markers CD133, NANOG, Oct4 and Sox2. Expression of these markers was downregulated in H19-deficient cells. Collectively, these data suggest a role for H19 in contributing to GBM malignancy and the maintenance of its stem cell properties.     

HOXB13 promotes proliferation,migration, and invasion of glioblastoma through transcriptional upregulation of lncRNA HOXC-AS3

HOXB13 exerts a close relation in several human cancers. This study explored the role of HOXB13 in glioblastoma (GBM), a brain tissue with the highest aggressive rate and mortality in adults. Through microarray and immunohistochemistry analyses, HOXB13 was highly expressed in GBM tissues. Furthermore, we showed that high-level expression of HOXB13 in GBM was associated with worse survival, suggesting that HOXB13 could be a prognostic marker for patients with GBM. GBM cells U87 and U251 overexpressing HOXB13 showed enhanced proliferation, migration, and invasion relative to the control cells, while knockdown of HOXB13 led to decreased cell proliferation, migration, and invasion abilities. In addition, dual-luciferase report assay, chromatin immunoprecipitation assay, and quantitative real-time polymerase chain reaction data showed that HOXB13 directly bound to HOXC-AS3 promoter. HOXC-AS3 was involved in HOXB13-induced proliferation, migration, and invasion of GBM cells. In summary, this study revealed the prognostic potential of HOXB13 in GBM. We believed that HOXB13/HOXC-AS3 signaling axis can be served as therapeutic targets for this highly aggressive cancer.     

CFTR activation suppresses glioblastoma cell proliferation,migration and invasion

The aim of this study was to investigate the function of Cystic fibrosis transmembrane conductance regulator (CFTR) in human glioblastoma (GBM) cells. Data dining results of the Human Protein Atlas showed that low CFTR expression was associated with poor prognosis for GBM patients. We found that CFTR protein expression was lower in U87 and U251 GBM cells than that in normal humane astrocyte cells. CFTR activation significantly reduced GBM cell proliferation. In addition, CFTR activation significantly abrogated migration and invasion of GBM cells. Besides, CFTR activator Forskolin treatment markedly reduced MMP-2 protein expression. These effects of CFTR activation were significantly inhibited by CFTR inhibitor CFTRinh-172 pretreatment. Our findings suggested that JAK2/STAT3 signaling was involved in the anti-glioblastoma effects of CFTR activation. Moreover, CFTR overexpression in combination with Forskolin induced a synergistic anti-proliferative response in U87?cells. Overall, our findings demonstrated that CFTR activation suppressed GBM cell proliferation, migration and invasion likely through the inhibition of JAK2/STAT3 signaling.     

NFκB pathway is down-regulated by 1α,25(OH)(2)-vitamin D(3) in endothelial cells transformed by Kaposi sarcoma-associated herpes virus G protein coupled receptor

We have previously demonstrated that 1α,25 dihydroxy-vitamin D(3) (1α,25(OH)(2)D(3)) has antiproliferative effects on the growth of endothelial cells transformed by the viral G protein-coupled receptor associated to Kaposi sarcoma (vGPCR). In this work, we have investigated whether 1α,25(OH)(2)D(3) exerts its growth inhibitory effects by inhibiting the Nuclear Factor κ B (NFκB) pathway which is highly activated by vGPCR. Cell proliferation studies demonstrated that 1α,25(OH)(2)D(3), similarly to bortezomib, a proteosome inhibitor that suppresses the activation of NFκB, reduced the proliferation of endothelial cells transformed by vGPCR (SVEC-vGPCR). The activity of NFκB in these cells decreased by 70% upon 1α,25(OH)(2)D(3) treatment. Furthermore, time and dose response studies showed that the hormone significantly decreased NFκB and increased IκBα mRNA and protein levels in SVEC-vGPCR cells, whereas in SVEC only IκBα increased significantly. Moreover, NFκB translocation to the nucleus was inhibited and occurred by a mechanism independent of NFκB association with vitamin D(3) receptor (VDR). 1α,25(OH)(2)D(3)-induced increase in IκBα required de novo protein synthesis, and was independent of MAPK and PI3K/Akt pathways. Altogether, these results suggest that down-regulation of the NFκB pathway is part of the mechanism involved in the antiproliferative effects of 1α,25(OH)(2)D(3) on endothelial cells transformed by vGPCR.     

Reversing the Warburg Effect as a Treatment for Glioblastoma

Glioblastoma multiforme (GBM), like most cancers, possesses a unique bioenergetic state of aerobic glycolysis known as the Warburg effect. Here, we documented that methylene blue (MB) reverses the Warburg effect evidenced by the increasing of oxygen consumption and reduction of lactate production in GBM cell lines. MB decreases GBM cell proliferation and halts the cell cycle in S phase. Through activation of AMP-activated protein kinase, MB inactivates downstream acetyl-CoA carboxylase and decreases cyclin expression. Structure-activity relationship analysis demonstrated that toluidine blue O, an MB derivative with similar bioenergetic actions, exerts similar action in GBM cell proliferation. In contrast, two other MB derivatives, 2-chlorophenothiazine and promethazine, exert no effect on cellular bioenergetics and do not inhibit GBM cell proliferation. MB inhibits cell proliferation in both temozolomide-sensitive and -insensitive GBM cell lines. In a human GBM xenograft model, a single daily dosage of MB does not activate AMP-activated protein kinase signaling, and no tumor regression was observed. In summary, the current study provides the first in vitro proof of concept that reversal of Warburg effect might be a novel therapy for GBM.     

The role of A-kinase interacting protein 1 in regulating progression and stemness as well as indicating the prognosis in glioblastoma

BackgroundA-kinase interacting protein 1 (AKIP1) is recently implicated in the pathogenesis of several solid tumors, while its role in glioblastoma multiforme (GBM) is largely unknown. Therefore, the current study aimed to investigate the effect of AKIP1 on GBM cell malignant behaviors, stemness, and its underlying molecular mechanisms.MethodsU-87 MG and A172 cells were transfected with control or AKIP1 overexpression plasmid; control or AKIP1 siRNA plasmid. Then cell proliferation, apoptosis, invasion, CD133⁺ cell proportion, and sphere formation assays were performed. Furthermore, RNA-Seq was performed in U-87 MG cells. Besides, AKIP1 expression was detected in 25 GBM and 25 low-grade glioma (LGG) tumor samples.ResultsAKIP1 was increased in several GBM cell lines compared to the control cell line. After transfections, it was found that AKIP1 overexpression increased cell invasion, CD133⁺ cell proportion, and sphere formation ability while less affecting cell proliferation or cell apoptosis in U-87 MG and A172 cells. Moreover, AKIP1 siRNA achieved the opposite effect in these cells, except that it inhibited cell proliferation but induced cell apoptosis to some extent. Subsequent RNA-Seq assay showed several critical carcinogenetic pathways, such as PI3K/AKT, Notch, EGFR tyrosine kinase inhibitor resistance, Ras, ErbB, mTOR pathways, etc. were potentially related to the function of AKIP1 in U-87 MG cells. Clinically, AKIP1 expression was higher in GBM tissues than in LGG tissues, which was also correlated with the poor prognosis of GBM to some degree.ConclusionsAKIP1 regulates the malignant behaviors and stemness of GBM via regulating multiple carcinogenetic pathways.     

A preclinical orthotopic model for glioblastoma recapitulates key features of human tumors and demonstrates sensitivity to a combination of MEK and PI3K pathway inhibitors

Current therapies for glioblastoma multiforme (GBM), the highest grade malignant brain tumor, are mostly ineffective, and better preclinical model systems are needed to increase the successful translation of drug discovery efforts into the clinic. Previous work describes a genetically engineered mouse (GEM) model that contains perturbations in the most frequently dysregulated networks in GBM (driven by RB, KRAS and/or PI3K signaling and PTEN) that induce development of Grade IV astrocytoma with properties of the human disease. Here, we developed and characterized an orthotopic mouse model derived from the GEM that retains the features of the GEM model in an immunocompetent background; however, this model is also tractable and efficient for preclinical evaluation of candidate therapeutic regimens. Orthotopic brain tumors are highly proliferative, invasive and vascular, and express histology markers characteristic of human GBM. Primary tumor cells were examined for sensitivity to chemotherapeutics and targeted drugs. PI3K and MAPK pathway inhibitors, when used as single agents, inhibited cell proliferation but did not result in significant apoptosis. However, in combination, these inhibitors resulted in a substantial increase in cell death. Moreover, these findings translated into the in vivo orthotopic model: PI3K or MAPK inhibitor treatment regimens resulted in incomplete pathway suppression and feedback loops, whereas dual treatment delayed tumor growth through increased apoptosis and decreased tumor cell proliferation. Analysis of downstream pathway components revealed a cooperative effect on target downregulation. These concordant results, together with the morphologic similarities to the human GBM disease characteristics of the model, validate it as a new platform for the evaluation of GBM treatment.KEY WORDS: Glioblastoma, Mouse model, PI3K and MEK inhibition, Apoptosis     

Cloning, expression, and characterization of TNFSF14 (LIGHT) gene in mefugu, Takifugu obscurus

Tumor necrosis factor receptor-associated factor 6 (TRAF6), which plays an important role in inflammation and immune response, is an essential adaptor protein for the NF-κB (nuclear factor κB) signaling pathway. Recent studies have shown that TRAF6 played an important role in tumorigenesis and invasion by suppressing NF-κB activation. However, up to now, the biologic role of TRAF6 in glioma has still remained unknown. To address the expression of TRAF6 in glioma cells, four glioma cell lines (U251, U-87MG, LN-18, and U373) and a non-cancerous human glial cell line SVG p12 were used to explore the protein expression of TRAF6 by Western blot. Our results indicated that TRAF6 expression was upregulated in human glioma cell lines, especially in metastatic cell lines. To investigate the role of TRAF6 in cell proliferation, apoptosis, invasion, and migration of glioma, we generated human glioma U-87MG cell lines in which TRAF6 was either overexpressed or depleted. Subsequently, the effects of TRAF6 on cell viability, cell cycle distribution, apoptosis, invasion, and migration in U-87MG cells were determined with 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyl tetrazolium bromide (MTT) assay, flow cytometry analysis, transwell invasion assay, and wound-healing assay. The results showed that knockdown of TRAF6 could decrease cell viability, suppress cell proliferation, invasion and migration, and promote cell apoptosis, whereas overexpression of TRAF6 displayed the opposite effects. In addition, the effects of TRAF6 on the expression of phosphor-NF-κB (p-p65), cyclin D1, caspase 3, and MMP-9 were also probed. Knockdown of TRAF6 could lower the expression of p-p65, cyclin D1, and MMP-9, and raise the expression of caspase 3. All these results suggested that TRAF6 might be involved in the potentiation of growth, proliferation, invasion, and migration of U-87MG cell, as well as inhibition of apoptosis of U-87MG cell by abrogating activation of NF-κB.     

Changes in the expression of proteins associated with aerobic glycolysis and cell migration are involved in tumorigenic ability of two glioma cell lines

ABSTRACT: BACKGROUND: The most frequent and malignant brain cancer is glioblastoma multiforme (GBM). In gliomas, tumor progression and poor prognosis are associated with the tumorigenic ability of the cells. U87MG cells (wild-type p53) are known to be tumorigenic in nude mice, but T98G cells (mutant p53) are not tumorigenic. We investigated the proteomic profiling of these two cell lines in order to gain new insights into the mechanisms that may be involved in tumorigenesis. RESULTS: We found 24 differentially expressed proteins between T98G and U87MG cells. Gene Ontology supports the notion that over-representation of differentially expressed proteins is involved in glycolysis, cell migration and stress oxidative response. Among those associated with the glycolysis pathway, TPIS and LDHB are up-regulated in U87MG cells. Measurement of glucose consumption and lactate production suggests that glycolysis is more effective in U87MG cells. On the other hand, G6PD expression was 3-fold higher in T98G cells and this may indicate a shift to the pentose-phosphate pathway. Moreover, GRP78 expression was also three-fold higher in T98G than in U87MG cells. Under thapsigargin treatment both cell lines showed increased GRP78 expression and the effect of this agent was inversely correlated to cell migration. Quantitative RT-PCR and immunohistochemistry of GRP78 in patient samples indicated a higher level of expression of GRP78 in grade IV tumors compared to grade I and non-neoplastic tissues, respectively. CONCLUSIONS: Taken together, these results suggest an important role of proteins involved in key functions such as glycolysis and cell migration that may explain the difference in tumorigenic ability between these two glioma cell lines and that may be extrapolated to the differential aggressiveness of glioma tumors.