Recent advances in immunobiology of brain tumors

Glioma stem-like cells evade interferon suppression through MBD3/NuRD complex-mediated STAT1 downregulation

Type I interferons (IFNs) are known to mediate antineoplastic effects during tumor progression. Type I IFNs can be produced by multiple cell types in the tumor microenvironment; however, the molecular mechanisms by which tumor cells evade the inhibition of immune microenvironment remain unknown. Here we demonstrate that glioma stem-like cells (GSCs) evade type I IFN suppression through downregulation of STAT1 to initiate tumor growth under inhospitable conditions. The downregulation of STAT1 is mediated by MBD3, an epigenetic regulator. MBD3 is preferentially expressed in GSCs and recruits NuRD complex to STAT1 promoter to suppress STAT1 expression by histone deacetylation. Importantly, STAT1 overexpression or MBD3 depletion induces p21 transcription, resensitizes GSCs to IFN suppression, attenuates GSC tumor growth, and prolongs animal survival. Our findings demonstrate that inactivation of STAT1 signaling by MBD3/NuRD provides GSCs with a survival advantage to escape type I IFN suppression, suggesting that targeting MBD3 may represent a promising therapeutic opportunity to compromise GSC tumorigenic potential.

Immunobiology of malignant gliomas

The immune system of patients with malignant gliomas is profoundly suppressed. The suppression involves both the cellular and humoral immunity and it is mainly attributable to selective depletion and malfunction of helper T cells. Malignant glioma cells express potent immunosuppressive factors such as transforming growth factor-beta(2), inteleukin-10 and prostaglandin E(2). Malignant glioma cells also produce chemoattractants and immunostimulatory cytokines which may activate the immune cells. However, the production of these stimulatory cytokines is not self-destructive to glioma cells because of the immunosuppression. Rather, the tumour cells use them to gain a growth advantage. Indeed the cytokines may act as a growth stimulator of the tumour cells themselves (autocrine mechanism), they may act as angiogenic factors to endothelial cells (paracrine mechanism) or induce the attracted immune cells to secrete angiogenic factors. Some cytokines produced by malignant glioma cells are known to be growth inhibitory to normal astrocytes. Recent studies on tumour suppressor genes suggest a close link between the aberrant genes and the immunobiologic features of malignant glioma cells.

In silico experimentation of glioma microenvironment development and anti-tumor therapy

Tumor cells do not develop in isolation, but co-evolve with stromal cells and tumor-associated immune cells in a tumor microenvironment mediated by an array of soluble factors, forming a complex intercellular signaling network. Herein, we report an unbiased, generic model to integrate prior biochemical data and the constructed brain tumor microenvironment in silico as characterized by an intercellular signaling network comprising 5 types of cells, 15 cytokines, and 69 signaling pathways. The results show that glioma develops through three distinct phases: pre-tumor, rapid expansion, and saturation. We designed a microglia depletion therapy and observed significant benefit for virtual patients treated at the early stages but strikingly no therapeutic efficacy at all when therapy was given at a slightly later stage. Cytokine combination therapy exhibits more focused and enhanced therapeutic response even when microglia depletion therapy already fails. It was further revealed that the optimal combination depends on the molecular profile of individual patients, suggesting the need for patient stratification and personalized treatment. These results, obtained solely by observing the in silico dynamics of the glioma microenvironment with no fitting to experimental/clinical data, reflect many characteristics of human glioma development and imply new venues for treating tumors via selective targeting of microenvironmental components.

Interleukin-1 regulates the expression of sphingosine kinase 1 in glioblastoma cells

Chronic inflammation and inflammatory cytokines have recently been implicated in the development and progression of various types of cancer. In the brain, neuroinflammatory cytokines affect the growth and differentiation of both normal and malignant glial cells, with interleukin 1 (IL-1) shown to be secreted by the majority of glioblastoma cells. Recently, elevated levels of sphingosine kinase 1 (SphK1), but not SphK2, were correlated with a shorter survival prognosis for patients with glioblastoma multiforme. SphK1 is a lipid kinase that produces the pro-growth, anti-apoptotic sphingosine 1-phosphate, which can induce invasion of glioblastoma cells. Here, we show that the expression of IL-1 correlates with the expression of SphK1 in glioblastoma cells, and neutralizing anti-IL-1 antibodies inhibit both the growth and invasion of glioblastoma cells. Furthermore, IL-1 up-regulates SphK1 mRNA levels, protein expression, and activity in both primary human astrocytes and various glioblastoma cell lines; however, it does not affect SphK2 expression. The IL-1-induced SphK1 up-regulation can be blocked by the inhibition of JNK, the overexpression of the dominant-negative c-Jun(TAM67), and the down-regulation of c-Jun expression by small interference RNA. Activation of SphK1 expression by IL-1 occurs on the level of transcription and is mediated via a novel AP-1 element located within the first intron of the sphk1 gene. In summary, our results suggest that SphK1 expression is transcriptionally regulated by IL-1 in glioblastoma cells, and this pathway may be important in regulating survival and invasiveness of glioblastoma cells.

Results of a phase 1 study utilizing monocyte-derived dendritic cells pulsed with tumor RNA in children and young adults with brain cancer

We conducted a phase 1 study of 9 pediatric patients with recurrent brain tumors using monocyte-derived dendritic cells pulsed with tumor RNA to produce antitumor vaccine (DCRNA) preparations. The objectives of this study included (1) establishing safety and feasibility and (2) measuring changes in general, antigen-specific, and tumor-specific immune responses after DCRNA. Dendritic cells were derived from freshly isolated monocytes after 7 days of culture with IL-4 and granulocyte-macrophage colony-stimulating factor, pulsed with autologous tumor RNA, and then cryopreserved. Patients received at least 3 vaccines, each consisting of an intravenous and an intradermal administration at biweekly intervals. The study showed that this method for producing and administering DCRNA from a single leukapheresis product was both feasible and safe in this pediatric brain tumor population. Immune function at the time of enrollment into the study was impaired in all patients tested. While humoral responses to recall antigens (diphtheria and tetanus) were intact in all patients, cellular responses to mitogen and recall antigens were below normal. Following DCRNA vaccine, 2 of 7 patients showed stable clinical disease and 1 of 7 showed a partial response. Two of 7 patients who were tested showed a tumor-specific immune response to DCRNA. This study showed that DCRNA vaccines are both safe and feasible in children with tumors of the central nervous system with a single leukapheresis.

Gene therapy of rat malignant gliomas using neural stem cells expressing IL-12

Primary malignant brain tumors have a poor prognosis. This report investigates the potential for gene therapy of experimental brain tumors using neural stem cells (NSCs) expressing IL-12. In this study NSCs were isolated from the hippocampi of 3-5-month human embryos and used for lipofectamine mediated transfer of the IL-12 gene. Positive clones of anti-G418 were obtained and were proliferated in culture and expression of IL-12 was demonstrated by RT-PCR. For the in vivo studies three groups of rats were used and stereotactic injections were made into the striatum. In the first group C6 tumor cells were injected, in the second C6 cells and hNSCs. IL-12, and in the third C6 cells on Day 0 followed by hNSCs.IL-12 on day 5. The growth of the resulting tumors was monitored by magnetic resonance imaging (MRI) and after sacrifice by immunohistochemistry. Rats injected with C6 cells and hNSCs.IL-12 had a significantly prolonged survival. Injections of hNSCs.IL-12 were also made into established gliomas. The survival time was also significantly prolonged compared to controls. MR imaging demonstrated that there was initial growth of tumor followed by shrinkage and then disappearance. After sacrifice, tumor areas were studied by histochemistry. NSCs were often seen intermingled with tumor cells, particularly when they had been injected into established tumors; they were also present at the boundaries of the tumor mass. The immunohistochemical analysis showed that these infiltrates were mostly constituted by CD4(+) and CD8(+) T-lymphocytes, the CD8(+) being more numerous than the CD4(+). These findings indicated that NSCs engineered to release IL-12 could have a strong antitumor effect. Neural stem/precursor cells could be useful vectors in genetic approaches to brain tumors.

Effect of Aspirin and Indomethacin on Prostaglandin E2 Synthesis in C6 Glioma Cells

Prostaglandin E2 (PGE2) plays an important role in immunosuppression and tumor growth. PGE2 inhibitors such as aspirin and indomethacin suppress experimental tumor growth. Little is known of the relationship between PGE2 synthesis in brain tumors and the dose of aspirin or indomethacin. The present study was undertaken to evaluate the effect of different doses of aspirin and indomethacin on PGE2 synthesis in C6 glioma cells. C6 glioma cells were incubated with different concentrations (2, 4, and 8 microM) of aspirin and indomethacin for 1, 2, 4, 6, 8, 12, and 24 hours. Intracellular PGE2 concentration was measured by enzyme immunoassay. Each concentration of aspirin and indomethacin effectively inhibited PGE2 synthesis. Concentrations of 2, 4, and 8 microM of aspirin significantly inhibited PGE2 production at 6, 4, and 1 hour, respectively, and the inhibition persisted for more than 24 hours (p < 0.05). Concentrations of 2 and 4 microM of indomethacin were effective at 4 and 2 hours (p < 0.05), respectively. However, inhibition was not observed beyond 12 hours (p > 0.05). Indomethacin 8 microM was effective at 1 hour and the inhibition persisted beyond 24 hours (p < 0.05). Our study demonstrates that aspirin and indomethacin inhibit PGE2 synthesis in C6 glioma cells and that low-dose aspirin is as effective as high-dose aspirin. This study may encourage future clinical use of low-dose aspirin in the prevention or treatment of brain tumors.

Models for Angiogenesis in Gliomas

During the last decades a lot of attention has been focussed on mechanisms of glioma vascularization, particularly in terms of investigating vascular growth factors and receptors. Recently, these efforts resulted in various approaches for antiangiogenic treatment strategies using in vitro cell culture systems as well as experimental orthotopic and non-orthotopic brain tumors. These basic science and preclinical trials need an assortment of models, which should allow investigating a variety of questions. Several objectives concerning basic endothelial cell (EC) characteristics can adequately be studied in vitro using EC monolayer assays. Three-dimensional spheroid techniques respect the more complex cell-cell and cell-environment interplay within a 3-dimensional culture. Recent advances in molecular genetic techniques offer a wide access to the genome of EC. Using these micro array or chip methods differences between micro- and macromolecular EC as well as variations within the gene pool of different organ specific EC can be assessed. To optimize the imitation of the crucial interaction of human gliomas with host endothelial cells, immunological cells and extracellular matrix, animal models are mandatory. An essential rule is to utilize an orthotopic model, since tumor-host-interaction is organ specific. To avoid alloimmunogenic responses, it is desirable to use weak or non-immunogenic glioma grafts, which is best accomplished in a syngeneic model. However, since rat gliomas poorly resemble human glioma growth patterns, human glioma xenografting into immunocompromized animals should be considered. In vivo-monitoring techniques like videoscopy via a cranial window or magnetic resonance imaging (MRI) allow for functional studies and improve the validity of the model employed. Finally, it is essentially to recognize the limitations of each model considered and to select that model which seems to be most appropriate for the objectives to be investigated.

History of allergies and autoimmune diseases and risk of brain tumors in adults

To explore a possible influence of the immune system in the development of brain tumors, we evaluated the relationship between history of allergies and autoimmune diseases and risk of brain tumors within a large, hospital-based case-control study. Cases (n = 782) were patients recently diagnosed with glioma (n = 489), meningioma (n = 197) or acoustic neuroma (n = 96) at hospitals in Boston, Phoenix and Pittsburgh (USA). Controls (n =799) were patients hospitalized for a variety of nonmalignant conditions and frequency-matched to cases by hospital, age, sex, race/ethnicity and distance of residence from hospital. Research nurses collected data by personal interview of patients. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using unconditional logistic regression. There was a significant inverse association between glioma and history of any allergies (OR = 0.67, 95% CI = 0.52-0.86) or autoimmune diseases (OR = 0.49, 95% CI = 0.35-0.69). No significant associations were evident for meningioma or acoustic neuroma with history of any allergies. An inverse association was observed between meningioma and history of autoimmune diseases (OR = 0.59, 95% CI = 0.38-0.92). There was a suggestion of interaction between allergies and autoimmune diseases on risk of glioma (p = 0.06), with subjects having both conditions being at lowest risk (OR = 0.24, 95% CI = 0.14-0.42). Among the specific conditions, asthma and diabetes showed the most consistent associations (OR = 0.63, 95% CI = 0.43-0.92 and OR = 0.44, 95% CI = 0.27-0.70, respectively). Our results add to evidence that persons with allergies or autoimmune diseases are at reduced risk of glioma. The basis of the associations is not clear, but they might imply a role of immunologic factors in the development of brain tumors. Published 2002 Wiley-Liss, Inc.

The alteration of prostaglandin E2 levels in patients with brain tumors before and after tumor removal

BACKGROUND

Both experimental and human tumors often synthesize high levels of prostaglandins, most notably prostaglandin E2 (PGE2). This compound may play an important role in tumor growth and immunosuppression. Little is known of the production of PGE2 by brain tumors. The present study was designed to investigate the levels of PGE2 in the plasma of human brain tumors before and after tumor removal.

METHODS

The plasma PGE2 levels of brain tumors before and after tumor removal were measured by high-performance liquid chromatography (HPLC).

RESULTS

There is a significantly high concentration of PGE2 in malignant brain tumor before tumor removal. Significantly decrease of PGE2 concentration after total removal of the tumor was found both in the malignant and benign brain tumor groups (P = 0.0001 and P = 0.0039 respectively). However, compared to the control group, only malignant brain tumor showed a significant decrease of PGE2 concentration after tumor removal (P = 0.0009).

CONCLUSION

Our study demonstrates the malignant brain tumor synthesized higher relative proportions of PGE2 and surgical removal of the brain tumor can reduce the production of PGE2.

Malignant glioma cells use MHC class II transactivator (CIITA) promoters III and IV to direct IFN-gamma-inducible CIITA expression and can function as nonprofessional antigen presenting cells in endocytic processing and CD4(+) T-cell activation

Malignant gliomas (MGs), lethal human central nervous system (CNS) neoplasms, contain tumor infiltrating lymphocytes (TIL). Although MHC class II molecules are frequently detected on MG cells, suggesting that they may be capable of antigen (Ag) presentation to CD4(+) T cells, deficiencies in CD4(+) T-cell activation are associated with these nonimmunogenic tumors. We evaluated regulation of the MHC class II transactivator (CIITA), the key intermediate that controls class II expression, in MG cells and tested whether MG cells could process native Ag. After interferon-gamma (IFN-gamma) stimulation, MG cells upregulated CIITA and class II molecules. IFN-gamma-inducible CIITA expression in MG cells, as well as primary human astrocytes, was directed by two CIITA promoters, pIV, the promoter for IFN-gamma-inducible CIITA expression in nonprofessional antigen-presenting cells (APC), and pIII, the promoter that directs constitutive CIITA expression in B cells. Both pIII and pIV directed CIITA transcription in vivo in MGs and ex vivo in IFN-gamma-activated primary MG cultures. We also demonstrate for the first time that MG cells can process native Ag for presentation to CD4(+) MHC class II-restricted Th1 cells, indicating that MG cells can serve as nonprofessional APC. CIITA may be a key target to modulate MHC class II expression, which could augment immunogenicity, Ag presentation, and CD4(+) T-cell activation in MG therapy.

Preliminary results of active specific immunization with modified tumor cell vaccine in glioblastoma multiforme

OBJECT

Treatment for glioblastoma multiforme has failed to show any progress for decades. While specific immunization with tumor cells modified with Newcastle-Disease-Virus (NDV) has been reported successful in some extracerebral tumors, its effect on glioblastoma is unknown. We report on 11 patients, in whom this approach was analyzed.

METHODS

A vaccine was produced from autologous tumor cell cultures of 11 patients with glioblastoma. After completed surgery and radiotherapy an intracutaneous vaccination was performed 4 times with a 2 week interval and finally after 3 months. Local reactions, general side effects and survival were monitored closely.

RESULTS

The local reaction of the skin after injection of vaccine increased from 1.67 to 4.05 cm2 in 8 weeks. The skin reaction after parallel injection of inactivated, untreated tumor cells increased from 0.11 to 1.09 cm2. The median survival was 46 weeks (mean 60 weeks). No side effects were noted.

CONCLUSION

Active specific immunization with NDV-modified glioblastoma cells produced a noticeable peripheral immune response. In this preliminary series survival of patients was not significantly longer after active specific immunization than after combined treatment of surgery, radiotherapy and chemotherapy. As there were no side effects, however, active specific immunization may be considered an alternative in the management of glioblastoma.

Antigen-presenting capability of glial cells under glioma-harboring conditions and the effect of glioma-derived factors on antigen presentation

The antigen-presenting capability of syngeneic rat glial cells was investigated under glioma-harboring conditions. Microglia induced a significant proliferation of glioma-primed splenocytes, but astrocytes did not. Furthermore, astrocytes suppressed the accessory cell function of microglia. The presence of both indomethacin and anti-interleukin (IL)-10 neutralizing antibody during priming of microglia enhanced splenocyte proliferation. The glioma culture supernatants down-regulated the interferon-gamma-induced expression of major histocompatibility complex class II molecules on microglia. The down-regulation was blocked by indomethacin and anti-IL-10 antibody. The results suggest that microglia but not astrocytes may function as antigen-presenting cells in glioma, and that glioma may suppress the antigen-presenting abilities of microglia.

Models for assessment of angiogenesis in gliomas

In the last two decades, much attention has been focussed on mechanisms of glioma vascularization including the investigation of growth factors and receptors involved. Recently, these efforts resulted in various approaches for antiangiogenic treatment of experimental brain tumors. These basic science and preclinical trials need an assortment of models, which should allow investigating a variety of questions. Several objectives concerning basic endothelial cell (EC) characteristics can adequately be studied in vitro using EC monolayer assays. Three-dimensional spheroid techniques respect the more complex cell-cell and cell-environment interplay within a three-dimensional culture. To optimize the imitation of the crucial interaction of human gliomas with host endothelial cells, immunological cells and extracellular matrix, animal models are mandatory. An essential rule is to utilize an orthotopic model, since tumor-host interaction is organ specific. To avoid alloimmunogenic responses, it is desirable to use weakly or not immunogenic glioma grafts, what is best accomplished in a syngeneic model. However, since rat gliomas poorly resemble human glioma growth patterns, human glioma xenografting into immunocompromized animals should be considered. In vivo monitoring techniques like videoscopy via a cranial window or magnetic resonance imaging (MRI) allow for functional studies and improve the validity of the model employed. Finally, it is essentially to recognize the limitations of each model considered and to select that model, which seems to be most appropriate for the objectives to be investigated.

Glioma immunology and immunotherapy

OBJECTIVE

Despite advances in conventional therapy, the prognosis for most glioma patients remains dismal. This has prompted an intensive search for effective treatment alternatives. Immunotherapy, one such alternative, has long been recognized as a potentially potent cancer treatment but has been limited by an inadequate understanding of the immune system. Now, increased insight into immunology is suggesting more rational approaches to immunotherapy. In this article, we explore key aspects of modern immunology and discuss their implications for glioma therapy.

METHODS

A thorough literature review of glioma immunology and immunotherapy was undertaken to inquire into the basic immunology, central nervous system immunology, glioma immunobiology, standard glioma immunotherapy, and recent immunotherapeutic advances in glioma treatment.

RESULTS

Although gliomas express tumor-associated antigens and appear potentially sensitive to immune responses, many factors work together to inhibit antiglioma immunity. Not surprisingly, most clinical attempts at glioma immunotherapy have met with little success to date. However, novel immunostimulatory strategies, such as immunogene therapy, directed cytokine delivery, and dendritic cell manipulation, have recently yielded dramatic preclinical results in glioma models. This suggests that glioma-derived immunosuppression can be overcome.

CONCLUSION

Modern molecular biology and immunology techniques have yielded a wealth of new data about glioma immunobiology. Armed with this information, many investigators have proposed novel means to stimulate antiglioma immune responses. Although definitive clinical results remain to be seen, the current renaissance in glioma immunology and immunotherapy shows great promise for the future.

Effects of continuous localized infusion of granulocyte-macrophage colony-stimulating factor and inoculations of irradiated glioma cells on tumor regression

OBJECT

Glioblastoma multiforme (GBM) is a malignant tumor of the central nervous system that directly suppresses immunological defenses in vitro and in vivo. The authors used the peripheral delivery of continuously infused granulocyte-macrophage colony-stimulating factor (GM-CSF) in the presence of irradiated tumor antigens as a tumor-specific stimulant to dendritic cells to initiate an immune response to GBM in rats.

METHODS

The 9L gliosarcoma tumors were established in the flanks of syngeneic Fischer 344 rats. Osmotic minipumps implanted in the animals' contralateral flanks continuously delivered recombinant GM-CSF (0, 0.1, 1, or 10 ng/day) for 28 days. Irradiated gliosarcoma cells were intermittently injected at the site of the GM-CSF infusion. Animals in the saline control group (0 ng/day GM-CSF) died on Day 59 with average tumor volumes greater than 30,000 mm3. This control group was significantly different from the GM-CSF-treated animals, which all survived with average tumor volumes that peaked on Day 23 and later regressed completely. Tumor growth as well as peak tumor volumes (5833+/-2284 mm3, 3294+/-1632 mm3, and 1979+/-1142 mm3 for 0.1, 1, and 10 ng/day GM-CSF, respectively) in the different treatment groups reflected a significant dose-response relationship with the GM-CSF concentrations. All animals treated with GM-CSF and irradiated cells were resistant to additional challenges of peripheral and intracerebral gliosarcoma, even when they were inoculated 8 months after initial immunotherapy. The colocalization of GM-CSF and inactivated tumor antigens was required to stimulate immunoprotection. To test the efficacy of a peripherally administered immunological therapy on intracerebral brain tumors the authors transplanted 10(6) gliosarcoma cells into the striatum of treated and control animals. Subcutaneous pumps that released GM-CSF (10 ng/day) and irradiated gliosarcoma cells were placed in the treated animals. The control animals all died within 31 days after intracerebral tumor implantation. In contrast, 40% of the animals receiving GM-CSF-irradiated cell vaccinations survived beyond 300 days. These long-term survivors showed no evidence of gliosarcoma at the injection site on evaluation by magnetic resonance imaging.

CONCLUSIONS

These results suggest that the continuous localized delivery of subcutaneous GM-CSF in conjunction with inactivated tumor antigens can initiate a systemic response that leads to the regression of distant peripheral and intracerebral tumors. The success of this treatment illustrates the feasibility of tumor-specific peripheral immunological stimulation after tumor resection to prevent the recurrence of malignant brain tumors.

New aspects of immunotherapy of leptomeningeal metastasis

Immunotherapeutic approaches to leptomeningeal metastasis (LM) include the intrathecal application of cytokines such as interleukin-2 (IL-2) and interferon-alpha (IFN-alpha), and lymphokine-activated killer cells (LAK cells). Results in a rodent model of leptomeningeal gliomatosis with intrathecal IL-2 application are discouraging, but some clinical improvement and clearance of neoplastic cells from CSF have been seen in patients with LM from melanoma treated with intrathecal IL-2 alone, and in patients with LM from primary brain tumors and squamous cell carcinoma of the tongue treated with intrathecal LAK cells and IL-2. The neurotoxicity of this therapy, mainly increased intracranial pressure, has been considerable but generally manageable. However, IFN-alpha caused severe neurotoxicity in form of an only partly reversible progressive vegetative state in the majority of patients. Considering the small number of patients treated with IL-2 and LAK cells, its value for the treatment of LM could only be stated by further investigation. In future, the application of recently discovered cytokines such as Fas-ligand, the continuous paracrine cytokine release by genetically modified cells, or vaccination strategies using genetically modified tumor cells might offer new immunotherapeutic approaches in LM.

Diminished monocytic HLA-DR expression and ex vivo cytokine secretion capacity in patients with glioblastoma: effect of tumor extirpation

Severe immunodysregulation on lymphocyte level has been described in patients with glioblastoma and is likely involved into its unfavorable prognosis. Although the major importance of monocytic cells for immunoregulation is well established, only very limited data exist regarding the monocyte status in glioblastoma patients. Here we demonstrate a markedly diminished monocytic HLA-DR expression and ex vivo cytokine secretion capacity (TNF-alpha, IL-1beta, IL-10) as signs for monocyte deactivation in glioblastoma patients but not in patients with astrocytoma. As known in immunocompromised patients from other reasons, monocyte deactivation indicate global immunodepression associated with an enhanced risk of infectious complications. Interestingly, tumor resection resulted in partial recovery from the monocytic deactivation. This suggests that the glioblastoma itself contributed to this phenomenon. However, IL-10 and the active forms of transforming growth factor-beta2 and -beta1, which are produced by glioblastoma cells and known to inhibit monocyte function, were not detectable in plasma in our patients. Moreover, low levels of the adrenocorticotropic hormone and cortisol excluded hypothalamo-pituitary-adrenal axis involvement. So, further investigations are necessary to clarify the mechanism. The demonstrated severe glioblastoma-associated monocytic deactivation may contribute to its unfavorable prognosis. Therefore, monocytes may represent target cells for new adjuvant immunotherapies in glioblastoma.

Human astrocytoma cells are capable of producing macrophage inflammatory protein-1beta

We investigated expression of macrophage inflammatory protein-1 (MIP-1) alpha and beta in human astrocytoma cell lines and surgical specimens of astrocytic tumors. Enzyme-linked immunosorbent assay (ELISA) showed constitutive secretion of MIP-1alpha protein in only one and MIP-1beta in none of 7 cell lines tested. However, MIP-1alpha production was increased in three cell lines by stimulation with lipopolysaccharide (LPS) and 5 cell lines by stimulation with phorbol-12myristate-13-acetate (PMA). Also, induction of MIP-1beta production was observed in one cell line with LPS stimulation and in two cell lines with PMA stimulation. Reverse-transcription polymerase chain reaction (RT-PCR) showed the increase of MIP-1alpha and beta mRNA expression in these cell lines. The increase of the mRNA with the stimuli was further confirmed by Northern blot analysis. In contrast, RT-PCR analysis revealed that the majority of the tested tumor specimens of high-grade.astrocytomas expressed both MIP-1alpha and MIP-1beta mRNAs. ELISA detected MIP-1beta protein in 1 of 11 cerebrospinal fluid samples from patients with high-grade astrocytoma and in 8 of 9 tumor cyst fluid samples, whereas MIP-1alpha was detected in only 1 cyst fluid somple. Taken together, these results indicate that astrocytic tumor cells are capable of expressing and producing MIPs, and suggest that MIPs may participate in the inflammatory responses commonly seen in astrocytic tumors.

Different release of cytokines into the cerebrospinal fluid following surgery for intra- and extra-axial brain tumours

To elucidate the role of cytokines in brain repair processes and in local inflammation after neurosurgical procedures, cerebrospinal fluid (CSF) samples from 8 patients with intra-axial tumours and 8 patients with extra-axial tumours were analysed for interleukin (IL)-1 beta, IL-1 receptor antagonist (IL-1 ra), IL-6, IL-8, IL-10, and tumour necrosis factor (TNF)-alpha at the beginning and after surgery. Levels of IL-6 and IL-8 increased dramatically in all patients just hours after surgery and fell during subsequent days. IL-1 beta was found only in low amounts in the CSF of both patient groups. Other cytokines demonstrated different courses. In patients with intra-axial tumours IL-1 ra peaked two to four hours after surgery with a subsequent decrease. In patients with extra-axial tumours there was a continuous low-level IL-1 ra release into the CSF without a peak. TNF-alpha was not present in detectable levels in the CSF after surgery for extra-axial tumours but was found to peak two to four hours after surgery for intra-axial tumours. IL-10 was detected in the CSF of both patient groups, but a higher peak was seen after surgery for extra-axial tumours. These results suggest different requirements for the cytokine response and an involvement of different cell types in cytokine release. However, the analysis of the CSF from both patient groups showed no differences in cell counts and populations, with a mild pleocytosis being present in both patient groups after surgery. Therefore, we conclude that after surgery for extra-axial tumours cytokines were predominately produced by non-immune cells stimulated through hypoxia or mechanical irritation. After surgery for intra-axial tumours with a significant brain injury immune cells-activated by necrotic material-seen to be involved in the process of cytokine synthesis. In these cases an additional IL-1ra and TNF-alpha peak was found and these cytokines may be markers for cerebral injury.

Intrathecal treatment of C6 glioma leptomeningeal metastasis in Wistar rats with interleukin-2

The efficacy of intrathecal treatment of leptomeningeal metastasis (LM) with interleukin-2 (IL-2) was evaluated in an animal model using Wistar rats inoculated intracisternally with 10(7) C6 glioma cells. Prior to the in vivo experiments the antiproliferative effects of human IL-2, and of murine IFN-gamma and TNF-alpha which are cytokines induced by IL-2 were tested in a colony forming assay. Only IFN-gamma caused a dose-dependent inhibition of colony formation. Twelve animals were treated intracisternally with either 10(5) IU IL-2 or control medium on day 0, 2, and 5 after tumor cell inoculation. Both IL-2 treated and sham-treated animals developed LM with a symptom-free survival of 7 to 9 days. There was no significant difference between treated and untreated animals regarding time to onset of symptoms and pattern of tumor growth. Infiltration of the tumor tissue with ED-1+ monocytes and macrophages, and CD8+ lymphocytes, however, was slightly increased in IL-2 treated animals. In a second experiment 4 non tumor-bearing Wistar rats were intracisternally injected with a single dose of 10(5) IU IL-2. These animals also showed slightly enhanced leptomeningeal infiltration with CD8+ lymphocytes compared to controls. We conclude that intrathecal application of high-dose IL-2 although eliciting a slight immune reaction within the leptomeninges does not inhibit leptomeningeal tumor growth or prolong symptom-free survival in our animal model of LM. These results raise doubt about the clinical efficacy of intrathecal IL-2 treatment in patients with LM.

Transforming growth factor-beta-mediated autocrine growth regulation of gliomas as detected with phosphorothioate antisense oligonucleotides

Transforming growth factors-beta 1 and -beta 2 (TGF-beta 1 and -beta 2) are important growth-regulatory proteins for astroglial neoplasms. We analyzed their role in tumor-cell proliferation in 12 glioma cell lines, employing phosphorothioate antisense oligodeoxynucleotides (S-ODNs, 14 mer), specifically targeted against the coding sequences of TGF-beta 1-mRNA and TGF-beta 2-mRNA. TGF-beta 1-S-ODNs inhibited cell proliferation in 5 of 12 gliomas, whereas TGF-beta 2-S-ODNs reduced the cell proliferation in all glioma cell lines, compared to nonsense-S-ODN-treated and S-ODN-untreated cells as controls. The efficacy and specificity of antisense effects was validated by Northern-blot analysis and determination of protein concentrations in culture supernatants (ELISA). Exogenous hrTGF-beta 1 either stimulated or inhibited the cell lines, whereas pnTGF-beta 2 stimulated the proliferation of most glioma cells. Blocking the extracellular pathway of TGF-beta by neutralizing antibodies only slightly inhibited those cell lines, which were markedly stimulated by TGF-betas. As the effects of TGF-beta 2-S-ODNs were much stronger than those of TGF-beta neutralizing antibodies, we postulate that the endogenously produced TGF-beta 2 control glioma-cell proliferation, in part by an intracellular loop.