Elevated levels of MIC-1/GDF15 in the cerebrospinal fluid of patients are associated with glioblastoma and worse outcome

For patients with brain tumors identification of diagnostic and prognostic markers in easy accessible biological material, such as plasma or cerebrospinal fluid (CSF), would greatly facilitate patient management. MIC-1/GDF15 (growth differentiation factor 15) is a secreted protein of the TGF-beta superfamily and emerged as a candidate marker exhibiting increasing mRNA expression during malignant progression of glioma. Determination of MIC-1/GDF15 protein levels by ELISA in the CSF of a cohort of 94 patients with intracranial tumors including gliomas, meningioma and metastasis revealed significantly increased concentrations in glioblastoma patients (median, 229 pg/ml) when compared with control cohort of patients treated for non-neoplastic diseases (median below limit of detection of 156 pg/ml, p < 0.0001, Mann-Whitney test). However, plasma MIC-1/GDF15 levels were not elevated in the matching plasma samples from these patients. Most interestingly, patients with glioblastoma and increased CSF MIC-1/GDF15 had a shorter survival (p = 0.007, log-rank test). In conclusion, MIC-1/GDF15 protein measured in the CSF may have diagnostic and prognostic value in patients with intracranial tumors.

Modulation of angiogenic and inflammatory response in glioblastoma by hypoxia

Glioblastoma are rapidly proliferating brain tumors in which hypoxia is readily recognizable, as indicated by focal or extensive necrosis and vascular proliferation, two independent diagnostic criteria for glioblastoma. Gene expression profiling of glioblastoma revealed a gene expression signature associated with hypoxia-regulated genes. The correlated gene set emerging from unsupervised analysis comprised known hypoxia-inducible genes involved in angiogenesis and inflammation such as VEGF and BIRC3, respectively. The relationship between hypoxia-modulated angiogenic genes and inflammatory genes was associated with outcome in our cohort of glioblastoma patients treated within prospective clinical trials of combined chemoradiotherapy. The hypoxia regulation of several new genes comprised in this cluster including ZNF395, TNFAIP3, and TREM1 was experimentally confirmed in glioma cell lines and primary monocytes exposed to hypoxia in vitro. Interestingly, the cluster seems to characterize differential response of tumor cells, stromal cells and the macrophage/microglia compartment to hypoxic conditions. Most genes classically associated with the inflammatory compartment are part of the NF-kappaB signaling pathway including TNFAIP3 and BIRC3 that have been shown to be involved in resistance to chemotherapy.

Our results associate hypoxia-driven tumor response with inflammation in glioblastoma, hence underlining the importance of tumor-host interaction involving the inflammatory compartment.

Enhanced response to radiotherapy in tumours deficient in the function of hypoxia-inducible factor-1

BACKGROUND AND PURPOSE

To test the hypothesis that deficiency in expression of the transcription factor, HIF-1, renders tumours more radioresponsive than HIF-1 proficient tumours.

PATIENTS AND METHODS

Tumours comprising mouse hepatoma cells lacking HIF-1beta (and thereby HIF-1 function) were grown in nude mice and radiation-induced growth delay compared with that seen for wild-type tumours and tumours derived from HIF-1beta negative cells where HIF-1 function had been restored.

RESULTS

The xenografts that lack HIF-1 activity take longer to establish their growth and are more radioresponsive than both parental xenografts and those with restored HIF-1 function. Pre-treatment of the HIF-1 deficient xenografts with the hypoxic radiosensitizer misonidazole, had little effect on radioresponse. In contrast this treatment radiosensitized the parental xenografts. In spite of this, no difference in oxygenation status was found between the tumour types as measured by Eppendorf O(2)-electrodes and by binding of the hypoxic cell marker NITP. Admixing wild type and HIF-1 deficient cells in the same tumour at ratios of 1 in 10 and 1 in 100 restores the growth of the mixed tumours to that of a 100% HIF-1 proficient cell population. However, when comparing the effects of radiation on the mixed tumours, radioresponsiveness is maintained in those tumours containing the high proportion of HIF-1 deficient cells.

CONCLUSIONS

The differences in radioresponse do not correlate with tumour oxygenation, suggesting that the hypoxic cells within the HIF-1 deficient tumours do not contribute to the outcome of radiotherapy. Thus, hypoxia impacts on tumour radioresponsiveness not simply because of the physio-chemical mechanism of oxygen with radiation-induced radicals causing damage 'fixation', but also because hypoxia/HIF-1 promotes expression of genes that allow tumour cells to survive under these adverse conditions. Further, the results from the cell mixing experiments uncouple the growth promoting effects of HIF-1 and the underlying mechanism by which HIF-1 may increase radiation resistance in solid tumours.

Differential role of p300 and CBP acetyltransferase during myogenesis: p300 acts upstream of MyoD and Myf5

Studies in tissue culture cells have implicated p300 and CBP acetyltransferases in myogenic regulatory factor (MRF) mediated transcription and terminal differentiation of skeletal muscle cells. However, in vivo data placing p300 and CBP on myogenic differentiation pathways are not yet available. In this report we provide genetic evidence that p300 but not CBP acetyltransferase (AT) activity is required for myogenesis in the mouse and in embryonic stem (ES) cells. A fraction of embryos carrying a single p300 AT- deficient allele exhibit impaired MRF expression, delayed terminal differentiation and a reduced muscle mass. In mouse embryos lacking p300 protein, Myf-5 induction is severely attenuated. Similarly, ES cells homozygous for a p300 AT or a p300 null mutation fail to activate Myf5 and MyoD transcription efficiently, while Pax3, acting genetically upstream of these MRFs, is expressed. In contrast, ES cells lacking CBP AT activity express MyoD and Myf5 and undergo myogenic differentiation. These data reveal a specific requirement for p300 and its AT activity in the induction of MRF gene expression and myogenic cell fate determination in vivo.

Classification of human astrocytic gliomas on the basis of gene expression: a correlated group of genes with angiogenic activity emerges as a strong predictor of subtypes

The development of targeted treatment strategies adapted to individual patients requires identification of the different tumor classes according to their biology and prognosis. We focus here on the molecular aspects underlying these differences, in terms of sets of genes that control pathogenesis of the different subtypes of astrocytic glioma. By performing cDNA-array analysis of 53 patient biopsies, comprising low-grade astrocytoma, secondary glioblastoma (respective recurrent high-grade tumors), and newly diagnosed primary glioblastoma, we demonstrate that human gliomas can be differentiated according to their gene expression. We found that low-grade astrocytoma have the most specific and similar expression profiles, whereas primary glioblastoma exhibit much larger variation between tumors. Secondary glioblastoma display features of both other groups. We identified several sets of genes with relatively highly correlated expression within groups that: (a). can be associated with specific biological functions; and (b). effectively differentiate tumor class. One prominent gene cluster discriminating primary versus nonprimary glioblastoma comprises mostly genes involved in angiogenesis, including VEGF fms-related tyrosine kinase 1 but also IGFBP2, that has not yet been directly linked to angiogenesis. In situ hybridization demonstrating coexpression of IGFBP2 and VEGF in pseudopalisading cells surrounding tumor necrosis provided further evidence for a possible involvement of IGFBP2 in angiogenesis. The separating groups of genes were found by the unsupervised coupled two-way clustering method, and their classification power was validated by a supervised construction of a nearly perfect glioma classifier.

Targeted disruption of the mouse PAS domain serine/threonine kinase PASKIN

PASKIN is a novel mammalian serine/threonine kinase containing two PAS (Per-Arnt-Sim) domains. PASKIN is related to the Rhizobium oxygen sensor protein FixL and to AMP-regulated kinases. Like FixL, the sensory PAS domain of PASKIN controls the kinase activity by autophosphorylation in a (unknown) ligand-dependent manner. In Saccharomyces cerevisiae, the two PASKIN orthologues PSK1 and PSK2 phosphorylate three translation factors and two enzymes involved in glycogen synthesis, thereby coordinately regulating protein synthesis and glycolytic flux. To elucidate the function of mammalian PASKIN, we inactivated the mouse Paskin gene by homologous recombination in embryonic stem cells. Paskin(-/-) mice showed normal development, growth, and reproduction. The targeted integration of a lacZ reporter gene allowed the identification of the cell types expressing mouse PASKIN. Surprisingly, PASKIN expression is strongly upregulated in postmeiotic germ cells during spermatogenesis. However, fertility and sperm production and motility were not affected by the PASKIN knockout. The Ppp1r7 gene encoding Sds22, a regulatory subunit of protein phosphatase 1, shares the promoter region with the Paskin gene, pointing towards a common transcriptional regulation. Indeed, Sds22 colocalized with the cell types expressing PASKIN in vivo, suggesting a functional role of protein phosphatase-1 in the regulation of PASKIN autophosphorylation.

Characterization of HIF-1 alpha overexpressing HeLa cells and implications for gene therapy

Upon exposing mammalian tissues to hypoxia, expression of a number of physiologically important genes such as erythropoietin and vascular endothelial growth factor (VEGF) increases. The key regulator for this oxygen-dependent gene expression is the hypoxia-inducible factor-1 (HIF-1), a heterodimeric transcription factor consisting of an alpha and a beta subunit. Both HIF-1 subunits are widely expressed in the cells and tissue of vertebrates, flies, fishes, worms and probably most other species. The beta subunit (also termed ARNT, aryl hydrocarbon receptor nuclear translocator) is abundantly expressed in an oxygen-independent manner. On the other hand, HIF-1alpha cannot be detected above a critical partial pressure of oxygen when it is subjected to rapid ubiquitinylation and proteasomal degradation. Hypoxic exposure leads to stabilization of HIF-1alpha protein and subsequent activation of HIF-1-dependent target genes. HIF-1 is not only a master regulator of oxygen homeostasis, it also appears to play a key role in tumor development as well as cardiovascular and ischemic diseases. Genetic modulation of HIF-1alpha activity in vivo may therefore represent a novel therapeutic approach to these disorders. In this overview, we report on the generation of HIF-1alpha overexpressing HeLa cell lines and demonstrate the feasibility of normoxic HIF-1 gene transfer in vitro and in vivo thereby identifying the limiting steps for full activation of HIF-1.

Rescue of hypoxia-inducible factor-1alpha-deficient tumor growth by wild-type cells is independent of vascular endothelial growth factor

In tumors, rapid cell proliferation associated with deficient vascularization leads to areas of hypoxia. Tumor hypoxia has direct consequences on clinical and prognostic parameters and is a potential therapeutic target. The hypoxic response depends critically on hypoxia-inducible factor-1alpha (HIF-1alpha) in pathological (e.g., tumorigenesis) as well as physiological (e.g., development and wound healing) processes. By s.c. injection of HIF-1alpha(-/-) embryonic stem (ES) cells in nude mice, we were able to demonstrate the role of HIF-1alpha in cell differentiation of teratocarcinomas. HIF-1alpha(+/+) tumors grow fast and preferentially form neuronal tissue, whereas HIF-1alpha(-/-) tumors show delayed growth and favorably form mesenchyme-derived tissue. Mixing wild-type and HIF-1alpha(-/-) ES cells in the same tumor at a ratio as low as 1:100, we showed that HIF-1alpha(+/+) cells can rescue the growth of mixed tumors although these tumors are not significantly different phenotypically or genotypically from the original HIF-1alpha(-/-) tumors. Interestingly, these results are not restricted to teratocarcinomas: they were confirmed with mixtures of Hepa1/Hepa1C4 cells (where HIF-1beta is mutated), demonstrating that growth changes are not related to differences in differentiation observed within teratocarcinomas. We also showed that despite lower mRNA expression, vascular endothelial growth factor protein status in HIF-1alpha(-/-) and mixed tumors does not significantly differ from the HIF-1alpha(+/+) tumors. Moreover, we demonstrated that tumor vascularization remains proportional to vascular endothelial growth factor protein levels, but that hypoxic up-regulation of this growth factor is not the decisive factor influencing tumor growth. Differences in levels of apoptosis are not responsible for alteration in growth because poly(ADP-ribose) polymerase cleavage, a hallmark of the apoptotic process, was similar in HIF-1alpha(+/+), HIF-1alpha(-/-), and mixed tumors. Our data demonstrate that the HIF-1alpha-dependent response of a few cells is capable of sustaining the growth of the whole tumor, probably through the secretion of factors up-regulated under low oxygen conditions.

Dissecting hypoxia-dependent and hypoxia-independent steps in the HIF-1alpha activation cascade: implications for HIF-1alpha gene therapy

The heterodimeric hypoxia-inducible factor (HIF)-1 is a master transcriptional regulator of oxygen homeostasis and a possible target for gene therapy of ischemic disease. Although the role of oxygen concentration in HIF-1a protein stabilization is well established, it is less clear whether and how oxygen-regulated mechanisms contribute to HIF-1a protein modifications, nuclear translocation, heterodimerization with the b-subunit, recruitment of cofactors, and gene trans-activation. Because the HIF-1a protein is proteolytically degraded under normoxic conditions, we established two HeLa Tet-Off cell lines (HT42 and HT43), which inducibly overexpress high levels of HIF-1a under normoxic conditions, allowing to distinguish hypoxia-dependent from hypoxia-independent activation mechanisms. Using these cells, we found that normoxically induced HIF-1a is localized to the nucleus, binds DNA, and trans-activates reporter and endogenous target genes. The levels of p53 expression remained unaffected. The MAP kinase inhibitor PD98059 attenuated HIF-1a protein modifications and trans-activation ability but not protein stabilization and DNA-binding activity. Because overexpressed HIF-1a is fully localized to the nucleus but displays only partial DNA-binding and trans-activation activity, mitogen-activated protein kinase-dependent phosphorylation might be required for full HIF-1 activation. HIF-1a protein was also overexpressed in vivo, following the transplantation of HT42 cells into nude mice, demonstrating the feasibility of HIF-1a gene transfer.

Mammalian PASKIN, a PAS-serine/threonine kinase related to bacterial oxygen sensors

The PAS domain is a versatile protein fold found in many archaeal, bacterial, and plant proteins capable of sensing environmental changes in light intensity, oxygen concentration, and redox potentials. The oxygen sensor FixL from Rhizobium species contains a heme-bearing PAS domain and a histidine kinase domain that couples sensing to signaling. We identified a novel mammalian PAS protein (PASKIN) containing a domain architecture resembling FixL. PASKIN is encoded by an evolutionarily conserved single-copy gene which is ubiquitously expressed. The human PASKIN and mouse Paskin genes show a conserved intron-exon structure and share their promoter regions with another ubiquitously expressed gene that encodes a regulator of protein phosphatase-1. The 144-kDa PASKIN protein contains a PAS region homologous to the FixL PAS domain and a serine/threonine kinase domain which might be involved in signaling. Thus, PASKIN is likely to function as a mammalian PAS sensor protein.

Embryoid bodies: an in vitro model of mouse embryogenesis

Embryonic stem (ES) cells are pluripotent cells isolated from the inner cell mass of blastocysts. ES cells are able to differentiate into the three primitive layers (endoderm, mesoderm and ectoderm) of the organism, including the germline. To study early stages of development, as well as to investigate the impact of a gene knock-out in vitro, ES cells are differentiated into three-dimensional structures called embryoid bodies, because of their ability to mimick post-implantation embryonic tissues. This review summarises the work on ES cell differentiation into haematopoietic and vascular cells, neuronal and glial cells, myocytes, and adipocytes, using this in vitro model of early embryogenesis. We also present the potential of this method to analyse the impact of genetic alterations in vitro.

Regulation of interleukin-8 expression by reduced oxygen pressure in human glioblastoma

Oxygen deprivation is an important biological feature of tumor growth. We previously showed that in glioma, anoxia increases expression of IL-8, a chemokine and angiogenic factor. Here, we analysed for the first time the biochemical mechanisms inducing the IL-8 gene upon anoxia in glioma cells, and showed that they differ from those inducing the VEGF gene. Both genes are induced in biologically and genetically heterogenous glioblastoma cell lines (LN-229, LN-Z308, U87MG, T98G), whereas, in gliosarcoma cells (D247MG), only the VEGF gene is induced. The kinetics of IL-8 and VEGF mRNA inductions differ in these cells and reoxygenation experiments showed that the induction is due to the anoxic stress per se. Furthermore, in LN-229 and LN-Z308 cell lines actinomycin D, DRB and nuclear run-on experiments showed that anoxia stimulates increased transcription of both genes. Electromobility shift assays show increased protein binding to the AP-1 site on the IL-8 promoter following anoxia treatment. Finally, in situ hybridization on glioblastoma sections shows that the in vivo expression patterns of IL-8 and VEGF genes overlap, but are not identical. Since intratumoral augmentation of IL-8 and VEGF secretion, following microenvironmental decreases in oxygen pressure, may promote angiogenesis, further definition of these pathways is essential to appropriately target them for antitumoral therapy.

Up-regulation of hypoxia-inducible factor-1alpha is not sufficient for hypoxic/anoxic p53 induction

Oxygen-deprived regions of a solid tumor can induce tumor suppressor p53 expression and hence select for p53-mutant tumor cells with diminished apoptotic potential. It has been proposed that the hypoxia-inducible factor-1 (HIF-1) alpha subunit binds to p53 and protects it from proteasomal degradation. However, we found that hypoxic conditions that strongly induce HIF-1-dependent endogenous gene expression as well as HIF-1alpha protein neither induce p53-dependent gene expression nor p53 protein. The iron chelator deferoxamine induced both HIF-1alpha and p53, but p53 up-regulation could still be detected in HIF-1alpha-deficient cells, suggesting that mechanisms other than HIF-1alpha activation contribute to oxygen-regulated p53 induction.

Necrogenesis and Fas/APO-1 (CD95) expression in primary (de novo) and secondary glioblastomas

Glioblastomas may develop rapidly without clinical and histopathological evidence of a less malignant precursor lesion (de novo or primary glioblastoma) or through progression from low-grade or anaplastic astrocytoma (secondary glioblastoma). Primary glioblastomas typically show overexpression of EGFR, but rarely p53 mutations, while secondary glioblastomas frequently carry a p53 mutation, but usually lack overexpression of EGFR, suggesting that these glioblastoma subtypes develop through distinct genetic pathways. In the present study, we assessed the expression of Fas/APO-1 (CD95), an apoptosis-mediating cell membrane protein, and its relation to necrosis phenotype in primary and secondary glioblastomas. Large areas of ischemic necroses were observed in all 18 primary glioblastomas, but were significantly less frequent in secondary glioblastomas (10 of 19, 53%; p = 0.0004). Fas expression was predominantly observed in glioma cells surrounding large areas of necrosis and was thus significantly more frequent in primary glioblastomas (18 of 18, 100%) than in secondary glioblastomas (4 of 19, 21%; p < 0.0001), suggesting that these clinically and genetically defined subtypes of glioblastoma differ in the extent and mechanism of necrogenesis. Necrosis and microvascular proliferation are histologic hallmarks of the glioblastoma. Following incubation of glioblastoma cell lines under hypoxic/anoxic conditions for 24-48 hours, Fas mRNA levels remained unchanged, whereas VEGF expression was markedly upregulated. This suggests that in contrast to VEGF Fas expression is not induced by ischemia/hypoxia. Analysis of Fas mRNA levels in a glioblastoma cell line containing a p53 mutation and an inducible wild-type p53 gene showed little difference under induced and noninduced conditions, suggesting that in glioblastomas, Fas expression is not directly linked to the p53 status.

Upregulation of interleukin 8 by oxygen-deprived cells in glioblastoma suggests a role in leukocyte activation, chemotaxis, and angiogenesis

Leukocyte infiltration and necrosis are two biological phenomena associated with the development of neovascularization during the malignant progression of human astrocytoma. Here, we demonstrate expression of interleukin (IL)-8, a cytokine with chemotactic and angiogenic properties, and of IL-8-binding receptors in astrocytoma. IL-8 expression is first observed in low grade astrocytoma in perivascular tumor areas expressing inflammatory cytokines. In glioblastoma, it further localizes to oxygen-deprived cells surrounding necrosis. Hypoxic/anoxic insults on glioblastoma cells in vitro using anaerobic chamber systems or within spheroids developing central necrosis induced an increase in IL-8 messenger RNA (mRNA) and protein expression. mRNA for IL-8-binding chemokine receptors CXCR1, CXCR2, and the Duffy antigen receptor for chemokines (DARC) were found in all astrocytoma grades by reverse transcription/PCR analysis. In situ hybridization and immunohistochemistry localized DARC expression on normal brain and tumor microvascular cells and CXCR1 and CXCR2 expression to infiltrating leukocytes. These results support a model where IL-8 expression is initiated early in astrocytoma development through induction by inflammatory stimuli and later in tumor progression increases due to reduced microenvironmental oxygen pressure. Augmented IL-8 would directly and/or indirectly promote angiogenesis by binding to DARC and by inducing leukocyte infiltration and activation by binding to CXCR1 and CXCR2.

Human astrocytomas and glioblastomas express monocyte chemoattractant protein-1 (MCP-1) in vivo and in vitro

Expression of the monocyte chemoattractant protein-1 (MCP-1) was examined in human central nervous system tumours (glioblastomas and astrocytomas) and normal human brain. Northern blot analysis demonstrated constitutive expression of MCP-1 mRNA in 6 of 12 glioblastoma cell lines. Expression could be stimulated by interleukin (IL)-1 beta and tumour necrosis factor (TNF)-alpha in all cell lines tested. Immunoprecipitation demonstrated secretion of both isoforms, MCP-1 alpha and -beta, of the MCP-1 protein. Reverse-transcription polymerase chain reaction and Northern blot analysis on tissues demonstrated MCP-1 mRNA expression in 17 of 17 glioblastomas, 3 of 6 anaplastic astrocytomas and 6 of 6 low-grade astrocytomas, as well as in fetal brain but not in normal adult brain. In situ hybridization on 2 glioblastomas and 1 low-grade astrocytoma indicates that neoplastic astrocytes and endothelial cells express MCP-1 mRNA in vivo. Moreover, tumour cyst fluids of glioblastomas and astrocytomas were able to induce monocyte chemoattraction in an in vitro assay. This chemotactic activity was specifically neutralized by anti-MCP-1 antibodies in 9 of 10 samples, further demonstrating the production of bioactive MCP-1 in vivo and supporting an important role for this factor in the infiltration of monocytes/macrophages into tumour tissue.

Analysis of cytokine receptor messenger RNA expression in human glioblastoma cells and normal astrocytes by reverse-transcription polymerase chain reaction

To elucidate which cytokine receptors may be expressed by human glioblastoma and normal astrocytic cells, the presence of messenger ribonucleic acid (RNA) for a number of cytokine receptors was examined in 16 glioblastoma cell lines and adult and fetal astrocytes. A complementary deoxyribonucleic acid copy of total RNA was synthesized and amplified with specific primers using the polymerase chain reaction method. The receptors studied were interleukin (IL)-1 receptor type I (IL-1RI) and type II (IL-1RII), p75 and p55 tumor necrosis factor (TNF) receptors (p75TNFR and p55TNFR), interferon (IFN)-alpha/beta and -gamma receptors (IFN-alpha/beta R and IFN-gamma R), granulocyte-macrophage (GM) colony-stimulating factors receptor alpha subunit (GM-CSFR), G-CSF receptor (G-CSFR), M-CSF receptor (c-fms, M-CSFR), stem cell factor receptor (c-kit, SCFR), IL-6 receptor (IL-6R), and IL-8 receptor (IL-8R). Transcripts for IL-1RI, p55TNFR, IFN-alpha/beta R, and IFN-gamma R were present in all cell lines. The presence of IL-1RII, p75TNFR, GM-CSFR, M-CSFR, SCFR, IL-6R, and IL-8R was identified in 13, eight, seven, eight, 14, three, and one cell lines, respectively. Normal astrocytes were positive for IL-1RI, p75TNFR, p55TNFR, IFN-alpha/beta R, IFN-gamma R, M-CSFR, and SCFR, showing a similarity to glioblastoma cells. Expression of IL-1RII was observed in adult astrocytes but not in fetal astrocytes. Furthermore, gene expression was assessed in normal brain tissue and 11 glioblastoma tissue specimens. The normal brain tissue expressed IL-1RI, IL-1RII, IFN-alpha/beta R, M-CSFR, and SCFR. Of the 11 glioblastoma tissue specimens, IL-1RI was positive in 11, IL-1RII in 10, p75TNFR in nine, p55TNFR in nine, IFN-alpha/beta R in 10, IFN-gamma R in 10, GM-CSFR in two, G-CSFR in three, IL-8R in eight, and M-CSFR and SCFR in 11. These expressions were consistent with those in the cell lines, except for IL-8R. It is concluded that glioblastoma cells and normal astrocytes express a similar set of cytokine receptor genes in vitro and in vivo. Possible autocrine loops are suggested for IL-1 alpha/IL-1RI, TNF-alpha/p55TNFR, IFN-beta/IFN-alpha/beta R, M-CSF/M-CSFR, and SCF/SCFR in glioblastomas.

Production of interleukin-1 receptor antagonist by human glioblastoma cells in vitro and in vivo

We investigated the expression and production of the interleukin-1 receptor antagonist (IL-1ra) in three human glioblastoma cell lines (LN443, LN444, LN859). Reverse transcription-polymerase chain reaction (RT-PCR) demonstrated the expression of IL-1ra mRNA transcripts in the three cell lines. These three cell lines also expressed mRNA for IL-1 alpha, IL-1 beta, as well as IL-1 receptor type I and type II, suggesting the presence of an IL-1 autocrine loop in these cell lines. Northern blot analysis demonstrated that the IL-1ra mRNA expression increased with IL-1 beta or tumor necrosis factor (TNF)-alpha but not with GM-CSF stimulation in both LN443 and LN444 cell lines. PMA stimulation increased the mRNA expression in LN444 but not in LN443 cells. Immunocytochemical staining showed IL-1ra immunoreactivity in these three cell lines. ELISA on culture supernatants demonstrated that the IL-1ra was secreted from the cell lines in agreement with the mRNA expression. RT-PCR with isoform-specific primers showed that both intracellular and secreted forms of IL-1ra were expressed by the three cell lines, with a predominance of the intracellular form. In vivo study with RT-PCR and Northern blot analysis demonstrated IL-1ra mRNA in six out of 12 human glioblastoma and two out of five anaplastic astrocytoma tissues, although the expression level was not high in some cases. Immunohistochemistry demonstrated the presence of IL-1ra within the cytoplasm of tumor cells in six out of 10 glioblastomas in vivo. These results suggest a potential role of IL-1ra in regulation of the IL-1 autocrine loop in glioblastomas.

Interleukin-8 is produced in neoplastic and infectious diseases of the human central nervous system

The presence of interleukin-8 (IL-8), a leukocyte chemotactic factor, was examined in primary and metastatic central nervous system tumors and in nonneoplastic acute meningoencephalitides. In vitro: (a) 11 of 12 glioblastoma cell lines constitutively expressed IL-8 mRNA; (b) 5 of 6 of these cell lines secreted IL-8 protein as detected by enzyme-linked immunosorbent assay and a glucosaminidase release bioassay; and (c) IL-1 beta or tumor necrosis factor was able to augment both IL-8 mRNA steady state levels and protein secretion of all cell lines tested except IN-319. IL-8 was also found in vivo. (a) IL-8 poly A+ mRNA was detected in 2 of 2 low grade astrocytomas, 1 of 2 anaplastic astrocytomas, and 6 of 6 glioblastomas. (b) IL-8 protein was present in the cyst fluid of 1 of 4 low grade astrocytomas, 1 anaplastic astrocytoma, 2 of 2 glioblastomas, 1 oligodendroglioma grade III, and one central nervous system cervical carcinoma metastasis. (c) The cerebrospinal fluid of 3 of 4 metastatic lymphomas, 2 of 16 glioblastomas, 1 of 2 low grade astrocytomas, but none of 3 anaplastic astrocytomas and none of 9 meningiomas contained IL-8. The presence of IL-8 was not restricted to central nervous system tumors as 2 of 2 bacterial meningitis and 5 of 5 acute viral meningitis patients contained considerable IL-8 levels in the cerebrospinal fluid. (d) Immunohistochemical analysis showed IL-8 immunoreactivity in perivascular tumor cells in 11 of 15 glioblastoma sections. These data suggest that IL-8 secretion could be a key factor involved in the determination of the lymphoid infiltrates observed in brain tumors and the development of cerebrospinal fluid pleocytosis in meningoencephalitides.