Inhibitory effects of cyclosporin A on calcium mobilization-dependent interleukin-8 expression and invasive potential of human glioblastoma U251MG cells

Effects of Postoperative Intravenous Cyclosporine Treatment on the Survival and Functional Performance Status of Patients With Glioblastoma: A Randomized, Triple-Blinded, Placebo-Controlled Clinical Trial

BACKGROUND

Glioblastoma is associated with low median survival time irrespective of maximal treatment. Previous in vitro studies have revealed tumor inhibitory effect of cyclosporine A. However, whether the addition of cyclosporine could improve survival among patients with glioblastoma is unknown. This study aimed to determine the impact of postoperation treatment with cyclosporine on the survival and performance status.

METHODS

In this randomized, triple-blinded, placebo-controlled trial, 118 patients with glioblastoma who underwent surgery were treated with standard chemoradiotherapy regimen. Patients were randomized to receive intravenous cyclosporine for 3 days postoperatively or placebo during the same period. The primary endpoint was the short-term effect of intravenous cyclosporine on survival and Karnofsky performance scores. Secondary endpoints were chemoradiotherapy toxicity and neuroimaging features.

RESULTS

The overall survival (OS) in the cyclosporine (17.03 ± 5.8, 95% confidence interval: 11-17.37 months) group was statistically lower than in the placebo (30.53 ± 4.9, 95% confidence interval: 8-32.3 months) groups (P = 0.049). However, compared to the placebo group, a statistically higher percentage of patients in the cyclosporine group were alive at 12 months follow-up. Also, progression-free survival in the cyclosporine group was significantly prolonged than in the placebo group (6.3 ± 4.07 months vs. 3.4 ± 2.98 months, P < 0.001). In the multivariate analysis, age <50 years (P = 0.022) and gross total resection (P = 0.03) were significantly associated with OS.

CONCLUSIONS

Our study results demonstrated that administering postoperative cyclosporine does not improve OS and functional performance status. Notably, the survival rate was significantly dependent on the patient age and the extent of glioblastoma resection.

Elevated plasma 20S proteasome chymotrypsin-like activity is correlated with IL-8 levels and associated with an increased risk of death in glial brain tumor patients

INTRODUCTION

In cancer treatment an attempt has been made to pharmacologically regulate the proteasome functions, thus the aim was to test whether 20S proteasome chymotrypsin-like (ChT-L) activity has a role in glial brain tumors. Furthermore, we analyzed the correlation between proteasome activity and IL-8, CCL2, NF-κB1 and NF-κB2 concentrations, which impact on brain tumors has already been indicated.

METHODS

Plasma 20S proteasome ChT-L activity was assayed using the fluorogenic peptide substrate Suc-Leu-Leu-Val-Tyr-AMC in the presence of SDS. IL-8, CCL2, NF-κB1 and NF-κB2 concentration was analyzed with the use of ELISA method. Immunohistochemistry for IDH1-R132H was done on 5-microns-thick formalin-fixed, paraffin-embedded tumor sections with the use of antibody specific for the mutant IDH1-R132H protein. Labelled streptavidin biotin kit was used as a detection system.

RESULTS

Brain tumor patients had statistically higher 20S proteasome ChT-L activity (0.649 U/mg) compared to non-tumoral individuals (0.430 U/mg). IDH1 wild-type patients had statistically higher 20S proteasome ChT-L activity (1.025 U/mg) compared to IDH1 mutants (0.549 U/mg). 20S proteasome ChT-L activity in brain tumor patients who died as the consequence of a tumor (0.649) in the following 2 years was statistically higher compared to brain tumor patients who lived (0.430 U/mg). In brain tumor patients the 20S proteasome ChT-L activity positively correlated with IL-8 concentration.

CONCLUSIONS

Elevated 20S proteasome ChT-L activity was related to the increased risk of death in glial brain tumor patients. A positive correlation between 20S proteasome ChT-L activity and IL-8 concentration may indicate the molecular mechanisms regulating glial tumor biology. Thus research on proteasomes may be important and should be carried out to verify if this protein complexes may represent a potential therapeutic target to limit brain tumor invasion.

Signaling Determinants of Glioma Cell Invasion

Tumor cell invasiveness is a critical challenge in the clinical management of glioma patients. In addition, there is accumulating evidence that current therapeutic modalities, including anti-angiogenic therapy and radiotherapy, can enhance glioma invasiveness. Glioma cell invasion is stimulated by both autocrine and paracrine factors that act on a large array of cell surface-bound receptors. Key signaling elements that mediate receptor-initiated signaling in the regulation of glioblastoma invasion are Rho family GTPases, including Rac, RhoA and Cdc42. These GTPases regulate cell morphology and actin dynamics and stimulate cell squeezing through the narrow extracellular spaces that are typical of the brain parenchyma. Transient attachment of cells to the extracellular matrix is also necessary for glioblastoma cell invasion. Interactions with extracellular matrix components are mediated by integrins that initiate diverse intracellular signalling pathways. Key signaling elements stimulated by integrins include PI3K, Akt, mTOR and MAP kinases. In order to detach from the tumor mass, glioma cells secrete proteolytic enzymes that cleave cell surface adhesion molecules, including CD44 and L1. Key proteases produced by glioma cells include uPA, ADAMs and MMPs. Increased understanding of the molecular mechanisms that control glioma cell invasion has led to the identification of molecular targets for therapeutic intervention in this devastating disease.

NFATc3 controls tumour growth by regulating proliferation and migration of human astroglioma cells

Calcium/Calcineurin/Nuclear Factor of Activated T cells (Ca/CN/NFAT) signalling pathway is the main calcium (Ca²⁺) dependent signalling pathway involved in the homeostasis of brain tissue. Here, we study the presence of NFATc members in human glioma by using U251 cells and a collection of primary human glioblastoma (hGB) cell lines. We show that NFATc3 member is the predominant member. Furthermore, by using constitutive active NFATc3 mutant and shRNA lentiviral vectors to achieve specific silencing of this NFATc member, we describe cytokines and molecules regulated by this pathway which are required for the normal biology of cancer cells. Implanting U251 in an orthotopic intracranial assay, we show that specific NFATc3 silencing has a role in tumour growth. In addition NFATc3 knock-down affects both the proliferation and migration capacities of glioma cells in vitro. Our data open the possibility of NFATc3 as a target for the treatment of glioma.

Bradykinin B1 receptor contributes to interleukin-8 production and glioblastoma migration through interaction of STAT3 and SP-1

Glioblastoma (GBM), the most aggressive brain tumor, has a poor prognosis due to the ease of migration to surrounding healthy brain tissue. Recent studies have shown that bradykinin receptors are involved in the progression of various cancers. However, the molecular mechanism and pathological role of bradykinin receptors remains unclear. We observed the expressions of two major bradykinin receptors, B1R and B2R, in two different human GBM cell lines, U87 and GBM8901. Cytokine array analysis showed that bradykinin increases the production of interleukin (IL)-8 in GBM via B1R. Higher B1R levels correlate with IL-8 expression in U87 and GBM8901. We observed increased levels of phosphorylated STAT3 and SP-1 in the nucleus as well. Using chromatin immunoprecipitation assay, we found that STAT3 and SP-1 mediate IL-8 expression, which gets abrogated by the inhibition of FAK and STAT3. We further demonstrated that IL-8 expression and cell migration are also regulated by the SP-1. In addition, expression levels of STAT3 and SP-1 positively correlate with clinicopathological grades of gliomas. Interestingly, our results found that inhibition of HDAC increases IL-8 expression. Moreover, stimulation with bradykinin caused increases in acetylated SP-1 and p300 complex formation, which are abrogated by inhibition of FAK and STAT3. Meanwhile, knockdown of SP-1 and p300 decreased the augmentation of bradykinin-induced IL-8 expression. These results indicate that bradykinin-induced IL-8 expression is dependent on B1R which causes phosphorylated STAT3 and acetylated SP-1 to translocate to the nucleus, hence resulting in GBM migration.

Overexpression of HOXC10 promotes glioblastoma cell progression to a poor prognosis via the PI3K/AKT signalling pathway

OBJECTIVE

The HOX gene is expressed in neoplasias occurred in multiple tissues, such as the colon, lung and breast. However, the effects of the HOX gene on glioblastoma (GBM) remain poorly understood. We examined HOXC10 expression in GBM tissues and cells, analysed its effect on GBM prognosis, and finally assessed its possible underlying mechanisms in this study.

METHODS

HOXC10 expression levels and its prognostic effects on GBM tissues were analysed based on The Cancer Genome Atlas (TCGA) and ONCOMINE database. Overall survival (OS) analysis was performed using the Kaplan-Meier method and log rank test. Then, the expression of HOXC10 was detected in four GBM cell lines using quantitative real-time reverse transcription-PCR (qRT-PCR). In addition, small interfering RNA (si-RNA) was utilised in the U87 cell line with the highest HOXC10 expression to facilitate subsequent in vitro cell experiment. Cell proliferation, migration and invasion were assessed using the Cell Counting Kit-8 (CCK-8) and colony formation assay, wound healing, Transwell assay, respectively in GBM U87 cell after HOXC10 knockdown. Key proteins related to the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) signalling pathway were measured by western blotting.

RESULTS

HOXC10 expression was significantly increased in GBM tissues and cell lines, leading a poor OS in GBM patients. Knockdown of HOXC10 could inhibit the GBM U87 cells proliferation, migration and invasion, as well as decreased expression levels of key proteins in PI3K/AKT signalling pathway.

CONCLUSION

HOXC10 was overexpressed in GBM tissues and cells, and associated with poor prognosis in GBM patients. Moreover, HOXC10 knockdown inhibited U87 cell proliferation, migration and invasion, which were potentially related to PI3K/AKT signalling pathway activation. Our findings revealed that HOXC10 represent a promising biological target for GBM treatment in the future.

Protein phosphatase 2A regulation of markers of extracellular matrix remodelling in hepatocellular carcinoma cells: functional consequences for tumour invasion

BACKGROUND AND PURPOSE

A hallmark of tumour invasion is breakdown of the extracellular matrix due to dysregulation of the matrix metalloproteinase (MMP) system. While our understanding of how this is regulated by kinase signalling pathways is well established, its counter-regulation by protein phosphatases (PP) is poorly understood. Therefore, we investigated the effect of PP inhibition on markers of extracellular remodelling and how PP2A activity modulated MMP-9 abundance and function of Hep3B cells.

EXPERIMENTAL APPROACH

Cells were exposed to okadaic acid (OA), tautomycetin and cyclosporin A, and the expression profile determined using PCR. Effects of OA and a protein inhibitor of PP2A, CIP2A, on MMP-9 abundance, PP2A activity and cell migration were investigated using ELISA, promoter constructs, siRNA knockdown and transwell migration assays.

KEY RESULTS

OA increased expression and abundance of MMP-9 and the tissue inhibitor of MMP, TIMP-1, without affecting other MMPs, TIMPs and ADAMs. The effect on MMP-9 was mimicked by CIP2A overexpression and knockdown of the PPP2CA catalytic, but not PPP2R1A scaffolding, subunit. Cyclosporin A and PPP1CA silencing did not alter MMP-9 expression, while tautomycetin transiently increased it. Mutation of AP-1, but not NF-κB, binding sites inhibited OA-mediated MMP-9 transcriptional activity. OA and CIP2A decreased PP2A activity and increased cell migration.

CONCLUSION AND IMPLICATIONS

OA increased MMP-9 by decreasing PP2A activity and PP2Ac, through AP-1 binding sites on the MMP-9 promoter. The functional consequence of this and CIP2A overexpression was increased cell migration. Hence, PP2A inhibition induced a metastatic phenotype through alterations in MMP-9 in Hep3B cells.

Necrotic cells influence migration and invasion of glioblastoma via NF-κB/AP-1-mediated IL-8 regulation

Glioblastoma multiforme (GBM) is the most common primary intracranial tumor in adults and has poor prognosis. Diffuse infiltration into normal brain parenchyma, rapid growth, and the presence of necrosis are remarkable hallmarks of GBM. However, the effect of necrotic cells on GBM growth and metastasis is poorly understood at present. In this study, we examined the biological significance of necrotic tissues by exploring the molecular mechanisms underlying the signaling network between necrotic tissues and GBM cells. The migration and invasion of the GBM cell line CRT-MG was significantly enhanced by treatment with necrotic cells, as shown by assays for scratch wound healing and spheroid invasion. Incubation with necrotic cells induced IL-8 secretion in CRT-MG cells in a dose-dependent manner. In human GBM tissues, IL-8 positive cells were mainly distributed in the perinecrotic region, as seen in immunohistochemistry and immunofluorescence analysis. Necrotic cells induced NF-κB and AP-1 activation and their binding to the IL-8 promoter, leading to enhanced IL-8 production and secretion in GBM cells. Our data demonstrate that when GBM cells are exposed to and stimulated by necrotic cells, the migration and invasion of GBM cells are enhanced and facilitated via NF-κB/AP-1 mediated IL-8 upregulation.

Functional cross talk between CXCR4 and PDGFR on glioblastoma cells is essential for migration

Glioblastoma (GBM) is the most common and aggressive form of brain tumor, characterized by high migratory behavior and infiltration in brain parenchyma which render classic therapeutic approach ineffective. The migratory behaviour of GBM cells could be conditioned by a number of tissue- and glioma-derived cytokines and growth factors. Although the pro-migratory action of CXCL12 on GBM cells in vitro and in vivo is recognized, the molecular mechanisms involved are not clearly identified. In fact the signaling pathways involved in the pro-migratory action of CXCL12 may differ in individual glioblastoma and integrate with those resulting from abnormal expression and activation of growth factor receptors. In this study we investigated whether some of the receptor tyrosine kinases commonly expressed in GBM cells could cooperate with CXCL12/CXCR4 in their migratory behavior. Our results show a functional cross-talk between CXCR4 and PDGFR which appears to be essential for GBM chemotaxis.

Interleukins in glioblastoma pathophysiology: implications for therapy

Despite considerable amount of research, the poor prognosis of patients diagnosed with glioblastoma multiforme (GBM) critically needs new drug development to improve clinical outcomes. The development of an inflammatory microenvironment has long been considered important in the initiation and progression of glioblastoma; however, the success of developing therapeutic approaches to target inflammation for GBM therapy has yet been limited. Here, we summarize the accumulating evidence supporting a role for inflammation in the pathogenesis of glioblastoma, discuss anti-inflammatory targets that could be relevant for GBM treatment and provide a perspective on the challenges faced in the development of drugs that target GBM inflammation. In particular, we will review the function of IL-1β, IL-6 and IL-8 as well as the potential of kinase inhibitors targeting key players in inflammatory cell signalling cascades such as JAK, JNK and p38 MAPK.

Role of CXCR1 (CKR-1) in inflammation of experimental mesangioproliferative glomerulonephritis

CXCR1 (CKR-1), a receptor of IL-8, is expressed in various cells including neutrophils and monocytes, both of which play a major role in proliferating glomerular diseases. We investigated time-dependent expression of CXCR1 and the effect of single-dose cyclosporine A (CsA) treatment on this expression in experimental mesangioproliferative glomerulonephritis induced by anti-thymocyte serum (ATS). Wistar rats were divided into three groups. Group 1 (control, n = 24) received non-immune serum. Group 2 (nephritis, n = 24) received ATS. Group 3 (nephritis + CsA, n = 24) received ATS and CsA concomitantly. Kidneys from six rats in each group were removed at sixth hour, 3 days, 5 days, and 7 days. ATS induced proteinuria compared to controls (p < 0.001) and CsA precluded the development of proteinuria. Glomerular inflammation and mesangial proliferation were significantly higher in ATS group than control and CsA-treated rats (p < 0.001). ATS injection caused marked interstitial inflammation that was precluded by CsA (p < 0.001). CXCR1 was not expressed in control kidneys. However, ATS induced expression of CXCR1 in both glomeruli and tubulointerstitium. CsA treatment precluded CXCR1 expression in both glomeruli and tubulointerstitium only in the first 6 h. CXCR1 may contribute to inflammation in experimental mesangioproliferative glomerulonephritis. CsA may be beneficial by inhibiting CXCR1 expression and corresponding inflammation.

Signaling determinants of glioma cell invasion

Tumor cell invasiveness is a critical challenge in the clinical management of glioma patients. In addition, there is accumulating evidence that current therapeutic modalities, including anti-angiogenic therapy and radiotherapy, can enhance glioma invasiveness. Glioma cell invasion is stimulated by both autocrine and paracrine factors that act on a large array of cell surface-bound receptors. Key signaling elements that mediate receptor-initiated signaling in the regulation of glioblastoma invasion are Rho family GTPases, including Rac, RhoA and Cdc42. These GTPases regulate cell morphology and actin dynamics and stimulate cell squeezing through the narrow extracellular spaces that are typical of the brain parenchyma. Transient attachment of cells to the extracellular matrix is also necessary for glioblastoma cell invasion. Interactions with extracellular matrix components are mediated by integrins that initiate diverse intracellular signalling pathways. Key signaling elements stimulated by integrins include PI3K, Akt, mTOR and MAP kinases. In order to detach from the tumor mass, glioma cells secrete proteolytic enzymes that cleave cell surface adhesion molecules, including CD44 and L1. Key proteases produced by glioma cells include uPA, ADAMs and MMPs. Increased understanding of the molecular mechanisms that control glioma cell invasion has led to the identification of molecular targets for therapeutic intervention in this devastating disease.

Expression and Role of the Intermediate-Conductance Calcium-Activated Potassium Channel KCa3.1 in Glioblastoma

Glioblastomas are characterized by altered expression of several ion channels that have important consequences in cell functions associated with their aggressiveness, such as cell survival, proliferation, and migration. Data on the altered expression and function of the intermediate-conductance calcium-activated K (KCa3.1) channels in glioblastoma cells have only recently become available. This paper aims to (i) illustrate the main structural, biophysical, pharmacological, and modulatory properties of the KCa3.1 channel, (ii) provide a detailed account of data on the expression of this channel in glioblastoma cells, as compared to normal brain tissue, and (iii) critically discuss its major functional roles. Available data suggest that KCa3.1 channels (i) are highly expressed in glioblastoma cells but only scantly in the normal brain parenchima, (ii) play an important role in the control of glioblastoma cell migration. Altogether, these data suggest KCa3.1 channels as potential candidates for a targeted therapy against this tumor.

Numbl inhibits glioma cell migration and invasion by suppressing TRAF5-mediated NF-κB activation

Numblike, a negative regulator in glioma cell migration and invasion, was found to mediate nuclear factor kappa B activation by suppressing tumor necrosis factor receptor–associated factor 5.

The Notch signaling regulator Numblike (Numbl) is expressed in the brain, but little is known regarding its role in the pathophysiology of glial cells. In this paper, we report that Numbl expression was down-regulated in high-grade human glioma tissue samples and glioblastoma cell lines. To investigate the role of Numbl in glioma migration and invasion, we generated human glioma cell lines in which Numbl was either overexpressed or depleted. Overexpression of Numbl suppressed, while elimination of Numbl promoted, the migration and invasion of glioma cells. Numbl inhibited glioma migration and invasion by dampening NF-κB activity. Furthermore, Numbl interacted directly with tumor necrosis factor receptor–associated factor 5 (TRAF5), which signals upstream and is required for the activation of NF-κB, and committed it to proteasomal degradation by promoting K48-linked polyubiquitination of TRAF5. In conclusion, our data suggest that Numbl negative regulates glioma cell migration and invasion by abrogating TRAF5-induced activation of NF-κB.

CXCL12-induced glioblastoma cell migration requires intermediate conductance Ca2+-activated K+ channel activity

The activation of ion channels is crucial during cell movement, including glioblastoma cell invasion in the brain parenchyma. In this context, we describe for the first time the contribution of intermediate conductance Ca2+-activated K (IKCa) channel activity in the chemotactic response of human glioblastoma cell lines, primary cultures, and freshly dissociated tissues to CXC chemokine ligand 12 (CXCL12), a chemokine whose expression in glioblastoma has been correlated with its invasive capacity. We show that blockade of the IKCa channel with its specific inhibitor 1-[(2-chlorophenyl) diphenylmethyl]-1 H-pyrazole (TRAM-34) or IKCa channel silencing by short hairpin RNA (shRNA) completely abolished CXCL12-induced cell migration. We further demonstrate that this is not a general mechanism in glioblastoma cell migration since epidermal growth factor (EGF), which also activates IKCa channels in the glioblastoma-derived cell line GL15, stimulate cell chemotaxis even if the IKCa channels have been blocked or silenced. Furthermore, we demonstrate that both CXCL12 and EGF induce Ca2+ mobilization and IKCa channel activation but only CXCL12 induces a long-term upregulation of the IKCa channel activity. Furthermore, the Ca2+-chelating agent BAPTA-AM abolished the CXCL12-induced, but not the EGF-induced, glioblastoma cell chemotaxis. In addition, we demonstrate that the extracellular signal-regulated kinase (ERK)1/2 pathway is only partially implicated in the modulation of CXCL12-induced glioblastoma cell movement, whereas the phosphoinositol-3 kinase (PI3K) pathway is not involved. In contrast, EGF-induced glioblastoma migration requires both ERK1/2 and PI3K activity. All together these findings suggest that the efficacy of glioblastoma invasiveness might be related to an array of nonoverlapping mechanisms activated by different chemotactic agents.

IL-8 is a mediator of NF-κB induced invasion by gliomas

Glioblastoma (GBM) is the most common and deadly form of primary brain tumor with a median survival of eleven months, despite use of extensive chemotherapy, radiotherapy and surgery. We have previously shown that nuclear factor-kappa B (NF-κB) is aberrantly expressed in GBM tumors and primary cell lines derived from tumor tissue. Here we show that IL-8, a chemokine is also aberrantly expressed by GBM cell lines and expression of IL-8 is in large part, attributable to the aberrant activation of NF-κB. We hypothesized that invasiveness of GBM cells is driven at least in part by aberrantly expressed IL-8. In support of the hypothesis we found that treatment of glioma cells with an IL-8 neutralizing antibody markedly decreased their invasiveness compared to cells treated with control IgG or left untreated. Furthermore, downregulation of IL-8 protein production with use of IL-8 targeted siRNA also resulted in decreased invasion in matrigel. We next investigated the presence of IL-8 receptors by FACS analysis and found that GBM cells (U87, U251, D54 and LN229) only express CXCR1 but not CXCR2. Treatment of U87 cells with a blocking CXCR1 antibody reduced their invasion through matrigel. Finally, we found that addition of exogenous IL-8, following downregulation of NF-κB which results in loss of endogenous IL-8 production, incompletely restored tumor cell invasion. Our data indicate that IL-8 is necessary but not solely responsible for glioma cell invasion and mediates its effect in an autocrine manner.

Knockdown of CypA inhibits interleukin-8 (IL-8) and IL-8-mediated proliferation and tumor growth of glioblastoma cells through down-regulated NF-κB

Although cyclophilin A (CypA) has been reported to be over-expressed in cancer cells and solid tumors, its expression and role in glioblastomas have not been studied. Herein, we show that expression of CypA in human glioblastoma cell lines and tissues is significantly higher than in normal human astrocytes and normal counterparts of brain tissue. To determine the role of over-expressed CypA in glioblastoma, stable RNA interference (RNAi)-mediated knockdown of CypA (CypA KD) was performed in gliobastoma cell line U87vIII (U87MG · ΔEGFR). CypA KD stable single clones decrease proliferation, infiltration, migration, and anchorage-independent growth in vitro and with slower growth in vivo as xenografts in immunodeficient nude mice. We have also observed that knockdown of CypA inhibits expression of interleukin-8 (IL-8), a tumorigenic and proangiogenic cytokine. Conversely, enforced expression of CypA in the CypA KD cell line, Ud-12, markedly enhanced IL-8 transcripts and restored Ud-12 proliferation, suggesting that CypA-mediated IL-8 production provides a growth advantage to glioblastoma cells. CypA knockdown-mediated inhibition of IL-8 is due to reduced activity of NF-κB, which is one of the major transcription factors regulating IL-8 expression. These results not only establish the relevance of CypA to glioblastoma growth in vitro and in vivo, but also suggest that small interfering RNA-based CypA knockdown could be an effective therapeutic approach against glioblastomas.

Characterization of contraction-inducible CXC chemokines and their roles in C2C12 myocytes

Physical exercise triggers the release of several cytokines/chemokines from working skeletal muscles, but the underlying mechanism(s) by which skeletal muscles decipher and respond to highly complex contractile stimuli remains largely unknown. In an effort to investigate the regulatory mechanisms of the expressions of two contraction-inducible CXC chemokines, CXCL1/KC and CXCL5/LIX, in contracting skeletal muscle cells, we took advantage of our in vitro exercise model using highly developed contractile C(2)C(12) myotubes, which acquire properties similar to those of in vivo skeletal muscle via manipulation of Ca(2+) transients with electric pulse stimulation (EPS). Production of these CXC chemokines was immediately augmented by EPS-evoked contractile activity in a manner dependent on the activities of JNK and NF-kappaB, but not p38, ERK1/2, or calcineurin. Intriguingly, exposure of myotubes to cyclic mechanical stretch also induced expression of these CXC chemokines; however, a much longer period of stimulation (approximately 12 h) was required, despite rapid JNK phosphorylation. We also demonstrate herein that CXCL1/KC and CXCL5/LIX have the ability to raise intracellular Ca(2+) concentrations via CXCR2-mediated activation of pertussis toxin-sensitive Galpha(i) proteins in C(2)C(12) myoblasts, an action at least partially responsible for their migration and differentiation. Although we revealed a possible negative feedback regulation of their own production in response to the contractile activity in differentiated myotubes, exogenous administration of these CXC chemokines did not acutely influence either insulin-induced Akt phosphorylation or GLUT4 translocation in C(2)C(12) myotubes. Taken together, these data shed light on the fundamental characteristics of contraction-inducible CXC chemokine production and their potential roles in skeletal muscle cells.

The prolyl isomerase Pin1 regulates the NF-kappaB signaling pathway and interleukin-8 expression in glioblastoma

The brain tumor glioblastoma remains one of the most aggressive and devastating tumors despite decades of effort to find more effective treatments. A hallmark of glioblastoma is the constitutive activation of the NF-κB signaling pathway, which regulates cell proliferation, inflammation, migration, and apoptosis. The prolyl isomerase Pin1 has been found to bind directly to the NF-κB protein, p65, and cause increases in NF-κB promoter activity in a breast cancer model. We now present evidence that this interaction occurs in glioblastoma and that it has important consequences on NF-κB signaling. We demonstrate that Pin1 levels are enhanced in primary glioblastoma tissues compared to controls, and that this difference in Pin1 expression affects the migratory capacity of glioblastoma-derived cells. Pin1 knockdown decreases the amount of activated, phosphorylated p65 in the nucleus, resulting in inhibition of the transcriptional program of the IL-8 gene. Through the use of microarray, we also observed changes in the expression levels of other NF-κB regulated genes due to Pin1 knockdown. Taken together, these data suggest that Pin1 is an important regulator of NF-κB in glioblastoma, and support the notion of using Pin1 as a therapeutic target in the future.

Involvement of nuclear factor-kappa B in bcl-xL-induced interleukin 8 expression in glioblastoma

We recently reported that bcl-xL regulates interleukin 8 (CXCL8) protein expression and promoter activity in glioblastoma cells. In this paper we demonstrate that CXCL8 induction by bcl-xL is mediated through a nuclear factor-kappa B (NF-kB)-dependent mechanism. Mutational studies on the CXCL8 promoter showed that NF-kB binding site was required for bcl-xL-induced promoter activity and an enhanced nuclear expression of NF-kB subunits p65 and p50 was observed after bcl-xL over-expression. Electrophoretic mobility shift assay showed an increased DNA-binding activity of NF-kB in bcl-xL over-expressing cells and the use of specific antibodies confirmed the involvement of p65 and p50 in NF-kB activity on CXCL8 promoter sequence. NF-kB activity regulation by bcl-xL involved IkBalpha and IKK complex signaling pathway. In fact, bcl-xL over-expression induced a decrease of cytoplasmic expression of the IkBalpha protein, paralleled by an increase in the phosphorylation of the same IkBalpha and IKKalpha/beta. Moreover, the down-regulation of the ectopic or endogenous bcl-xL expression through RNA interference confirmed the ability of bcl-xL to modulate NF-kB pathway, and the transient expression of a degradation-resistant form of the cytoplasmic NF-kB inhibitor IkBalpha in bcl-xL transfectants confirmed the involvement of that inhibitor in bcl-xL-induced CXCL8 expression and promoter activity. In conclusion, our results demonstrate the role of NF-kB as the mediator of bcl-xL-induced CXCL8 up-regulation in glioblastoma cells.

Kaempferol induces apoptosis in glioblastoma cells through oxidative stress

Despite recent advances in understanding molecular mechanisms involved in glioblastoma progression, the prognosis of the most malignant brain tumor continues to be dismal. Because the flavonoid kaempferol is known to suppress growth of a number of human malignancies, we investigated the effect of kaempferol on human glioblastoma cells. Kaempferol induced apoptosis in glioma cells by elevating intracellular oxidative stress. Heightened oxidative stress was characterized by an increased generation of reactive oxygen species (ROS) accompanied by a decrease in oxidant-scavenging agents such as superoxide dismutase (SOD-1) and thioredoxin (TRX-1). Knockdown of SOD-1 and TRX-1 expression by small interfering RNA (siRNA) increased ROS generation and sensitivity of glioma cells to kaempferol-induced apoptosis. Signs of apoptosis included decreased expression of Bcl-2 and altered mitochondrial membrane potential with elevated active caspase-3 and cleaved poly(ADP-ribose) polymerase expression. Plasma membrane potential and membrane fluidity were altered in kaempferol-treated cells. Kaempferol suppressed the expression of proinflammatory cytokine interleukin-6 and chemokines interleukin-8, monocyte chemoattractant protein-1, and regulated on activation, normal T-cell expressed and secreted. Kaempferol inhibited glioma cell migration in a ROS-dependent manner. Importantly, kaempferol potentiated the toxic effect of chemotherapeutic agent doxorubicin by amplifying ROS toxicity and decreasing the efflux of doxorubicin. Because the toxic effect of both kaempferol and doxorubicin was amplified when used in combination, this study raises the possibility of combinatorial therapy whose basis constitutes enhancing redox perturbation as a strategy to kill glioma cells.

Production of angiogenic factors by human glioblastoma cells following activation of the G-protein coupled formylpeptide receptor FPR

Activation of the formylpeptide receptor (FPR), a G-protein-coupled receptor, by its chemotactic peptide ligand N-formylmethionyl-leucyl-phenylalanine (fMLF) promotes the directional migration and survival of human glioblastoma cells. fMLF also stimulates glioblastoma cells to produce biologically active VEGF, an important angiogenic factor involved in tumor progression. In this study, we examined the capacity of FPR to regulate the production of another angiogenic factor, the chemokine IL-8 (CXCL8), in addition to its demonstrated ability to induce VEGF secretion by malignant glioma cells. We showed that the human glioblastoma cell line U87 secreted considerable levels of IL-8 (CXCL8) upon stimulation by the FPR agonist peptide fMLF. Tumor cells transfected with small interference (si)RNA targeting FPR failed to produce IL-8 as well as VEGF in response to fMLF. Glioblastoma cells bearing FPR siRNA exhibited reduced rate of tumorigenicity in nude mice and tumors formed by such tumor cells showed less active angiogenesis and lower level expression of both IL-8 and VEGF. These results suggest that FPR plays an important role in the angiogenesis of human malignant gliomas through increasing the production of angiogenic factors by FPR positive tumor cells.

Calcineurin inhibitors and rapamycin: cancer protection or promotion?

Since the introduction of cyclosporin A (CsA) in the early 1980s, the use of immunosuppressants has markedly increased. Already established drugs have proved effective in the treatment of a wide range of diseases outside transplantation medicine and new immunosuppressants have been developed for more specific indications such as psoriasis and atopic dermatitis. Patients in transplantation medicine as well as in dermatology have benefited significantly from systemic and topical application of both new and established drugs. But are these drugs without risks? Cancer-protecting effects have been reported for some of the available immunosuppressants. Conversely, other publications and the issue of a black box warning by the US Food and Drug Administration have increased concerns about cancer-promoting effects. Knowledge of the specific effects as well as adverse effects is paramount to ensure an application that is safe and beneficial for the patient. Here we review the mechanisms of action and therapeutic potential, and critically review recent literature with respect to possible carcinogenic side effects of systemic and topical CsA, tacrolimus, pimecrolimus and rapamycin.

Aberrant constitutive activation of nuclear factor kappaB in glioblastoma multiforme drives invasive phenotype

Several recent studies have shown that aberrant constitutive activation of nuclear factor kappaB (NF-kappaB) is present in a variety of cancers including gliomas. NF-kappaB is known to play important roles in the physiological regulation of diverse cellular processes such as inflammation, growth and immunity. In contrast, aberrant activation of this latent transcription factor promotes cancer cell migration, invasion and resistance to chemotherapy. Here we show by electro-mobility shift assay (EMSA) and immuno-staining that constitutive NF-kappaB activation is present in various malignant glioma cell lines as well as in primary cultures derived from tumor tissue. This activation was not serum dependent and it led to high IL-8 gene transcription and protein production. Over-expression of an I-kappaB super-repressor (I-kappaB SR) transgene completely blocked constitutive NF-kappaB activation, nuclear localization and transcription of some but not all NF-kappaB regulated genes indicating that NF-kappaB signaling in glioma cells is I-kappaB dependent. Surprisingly, over-expression of IkappaBSR did not have any effect on the transcription levels of anti-apoptotic genes in these glioma cultures and cell lines. Down-regulation of NF-kappaB activation reduced invasion of glioma cells through matrigel. Collectively these data suggest that aberrant constitutive activation of NF-kappaB in glioblastoma cells promotes their invasive phenotype. Interruption of this aberrant NF-kappaB activity may help reduce the spread of this infiltrative tumor.

The role of interleukin-8 and its receptors in gliomagenesis and tumoral angiogenesis

Interleukin-8 (IL-8, or CXCL8), which is a chemokine with a defining CXC amino acid motif that was initially characterized for its leukocyte chemotactic activity, is now known to possess tumorigenic and proangiogenic properties as well. In human gliomas, IL-8 is expressed and secreted at high levels both in vitro and in vivo, and recent experiments suggest it is critical to glial tumor neovascularity and progression. Levels of IL-8 correlate with histologic grade in glial neoplasms, and the most malignant form, glioblastoma, shows the highest expression in pseudopalisading cells around necrosis, suggesting that hypoxia/anoxia may stimulate expression. In addition to hypoxia/anoxia stimulation, increased IL-8 in gliomas occurs in response to Fas ligation, death receptor activation, cytosolic Ca(2+), TNF-alpha, IL-1, and other cytokines and various cellular stresses. The IL-8 promoter contains binding sites for the transcription factors NF-kappaB, AP-1, and C-EBP/NF-IL-6, among others. AP-1 has been shown to mediate IL-8 upregulation by anoxia in gliomas. The potential tumor suppressor ING4 was recently shown to be a critical regulator of NF-kappaB-mediated IL-8 transcription and subsequent angiogenesis in gliomas. The IL-8 receptors that could contribute to IL-8-mediated tumorigenic and angiogenic responses include CXCR1 and CXCR2, both of which are G-protein coupled, and the Duffy antigen receptor for cytokines, which has no defined intracellular signaling capabilities. The proangiogenic activity of IL-8 occurs predominantly following binding to CXCR2, but CXCR1 appears to contribute as well through independent, small-GTPase activity. A precise definition of the mechanisms by which IL-8 exerts its proangiogenic functions requires further study for the development of effective IL-8-targeted therapies.