Improved technique for establishing short term human brain tumor cultures

The effect of Azo-dyes on glioblastoma cells in vitro

Despite the multidisciplinary standard treatment of glioblastoma (GB) consisting of maximal surgical resection, followed by radiotherapy (RT) plus concomitant chemotherapy with temozolomide (TMZ), the majority of patients experience tumor progression and almost universal mortality. In recent years, efforts have been made to create new agents for GB treatment, of which azo-dyes proved to be potential candidates, showing antiproliferative effects by inducing apoptosis and by inhibiting different signaling pathways. In this study we evaluated the antiproliferative the effect of six azo-dyes and TMZ on a low passage human GB cell line using MTT assay. We found that all compounds proved antiproliferative properties on GB cells. At equimolar concentrations azo-dyes induced more cytotoxic effect than TMZ. We found that Methyl Orange required the lowest IC₅₀ for 3 days of treatment (26.4684 μM), whilst for 7 days of treatment, two azo dyes proved to have the highest potency: Methyl Orange IC₅₀ = 13.8808 μM and Sudan I IC₅₀ = 12.4829 μM. The highest IC₅₀ was determined for TMZ under both experimental situations. Conclusions: Our research represents a novelty, by offering unique valuable data regarding the azo-dye cyototoxic effects in high grade brain tumors. This study may focus the attention on azo-dye agents that may represent an insufficient exploited source of agents for cancer treatment.

Microdistribution and quantification of the boron neutron capture therapy drug BPA in primary cell cultures of human glioblastoma tumour by NanoSIMS

The ability of secondary ion mass spectrometry (SIMS) to provide high sensitivity imaging of elements and small-medium mass molecules in biological tissues and cells, makes it a very powerful tool for drug distribution studies. Here we report on the application of a high-resolution dynamic SIMS instrument for the quantification and localisation of therapeutic levels of the BNCT agent l-para-(dihydroxyboryl)-phenylalanine (BPA) in primary cell cultures from human patients exhibiting glioblastoma multiform tumours. Boron uptake and distribution was determined quantitatively as a function of cell-sampling location and different treatment regimes. Importantly, BPA was found to accumulate in cancer cells invading the 'brain around tumour' tissue in addition to the main tumour site. Pre-treatment of samples with l-tyrosine was found not to increase the uptake of BPA, nor change the intracellular drug distribution. In cultured cells from the tumour core and brain around tumour, with and without l-tyrosine pre-treatment, normalised boron-related signals were higher from cell nuclei than from cytoplasm. An efflux treatment was found to reduce BPA levels, but at a rate slower than the original uptake, and did not affect the intracellular drug distribution. To the best of our knowledge, these data represent the first published study of BPA uptake and l-amino acid pre-treatment in cultured primary human cells using dynamic SIMS, and the most detailed, subcellular distribution study of a BNCT agent in any cellular system.

High density is a property of slow-cycling and treatment-resistant human glioblastoma cells

Slow-cycling and treatment-resistant cancer cells escape therapy, providing a rationale for regrowth and recurrence in patients. Much interest has focused on identifying the properties of slow-cycling tumor cells in glioblastoma (GBM), the most common and lethal primary brain tumor. Despite aggressive ionizing radiation (IR) and treatment with the alkylating agent temozolomide (TMZ), GBM patients invariably relapse and ultimately succumb to the disease. In patient biopsies, we demonstrated that GBM cells expressing the proliferation markers Ki67 and MCM2 displayed a larger cell volume compared to rare slow-cycling tumor cells. In optimized density gradients, we isolated a minor fraction of slow-cycling GBM cells in patient biopsies and tumorsphere cultures. Transcriptional profiling, self-renewal, and tumorigenicity assays reflected the slow-cycling state of high-density GBM cells (HDGCs) compared to the tumor bulk of low-density GBM cells (LDGCs). Slow-cycling HDGCs enriched for stem cell antigens proliferated a few days after isolation to generate LDGCs. Both in vitro and in vivo, we demonstrated that HDGCs show increased treatment-resistance to IR and TMZ treatment compared to LDGCs. In conclusion, density gradients represent a non-marker based approach to isolate slow-cycling and treatment-resistant GBM cells across GBM subgroups.

Radioresistance of human glioma spheroids and expression of HSP70, p53 and EGFr

BACKGROUND

Radiation therapy is routinely prescribed for high-grade malignant gliomas. However, the efficacy of this therapeutic modality is often limited by the occurrence of radioresistance, reflected as a diminished susceptibility of the irradiated cells to undergo cell death. Thus, cells have evolved an elegant system in response to ionizing radiation induced DNA damage, where p53, Hsp70 and/or EGFr may play an important role in the process. In the present study, we investigated whether the content of p53, Hsp70 and EGFr are associated to glioblastoma (GBM) cell radioresistance.

METHODS

Spheroids from U-87MG and MO59J cell lines as well as spheroids derived from primary culture of tumor tissue of one GBM patient (UGBM1) were irradiated (5, 10 and 20 Gy), their relative radioresistance were established and the p53, Hsp70 and EGFr contents were immunohistochemically determined. Moreover, we investigated whether EGFr-phospho-Akt and EGFr-MEK-ERK pathways can induce GBM radioresistance using inhibitors of activation of ERK (PD098059) and Akt (wortmannin).

RESULTS

At 5 Gy irradiation UGBM1 and U-87MG spheroids showed growth inhibition whereas the MO59J spheroid was relatively radioresistant. Overall, no significant changes in p53 and Hsp70 expression were found following 5 Gy irradiation treatment in all spheroids studied. The only difference observed in Hsp70 content was the periphery distribution in MO59J spheroids. However, 5 Gy treatment induced a significant increase on the EGFr levels in MO59J spheroids. Furthermore, treatment with inhibitors of activation of ERK (PD098059) and Akt (wortmannin) leads to radiosensitization of MO59J spheroids.

CONCLUSIONS

These results indicate that the PI3K-Akt and MEK-ERK pathways triggered by EGFr confer GBM radioresistance.

Adenovirus mediated transfer of p53, GM-CSF and B7-1 suppresses growth and enhances immunogenicity of glioma cells

OBJECTIVES

Malignant gliomas are good targets for gene therapy because they have been proven incurable with conventional treatments. However, malignant gliomas are genetically and physiologically highly heterogeneous, and current gene therapy interventions have been designed to target only a few variations of this kind of disease. Hence, we developed a combined gene therapy approach using a recombinant adenovirus carrying human wild-type p53 (WT-p53), granulocyte-macrophage colony-stimulating factor (GM-CSF) and B7-1 genes (designated BB-102) to combat the disease.

METHODS

Human malignant glioma cells U251 and U87 were transduced with BB-102. Expression of WT-p53, GM-CSF and B7-1 genes were determined by Western blot, enzyme linked immunosorbent assay and flow cytometric analysis, respectively. Growth rates were determined by serial cell counts. Apoptosis was detected by flow cytometric analysis. Proliferation of autologous peripheral blood lymphocytes (PBLs) and cytotoxicity against primary glioma cells were assessed by cell proliferation and cytotoxicity assay kits, respectively.

RESULTS

By the transduction of BB-102, high expression levels of the three exogenesis genes were detected in glioma cells. Cell growth was inhibited and apoptosis was induced. Significant proliferation of autologous PBLs and specific cytotoxicity against primary glioma cells were also induced by the infection of BB-102 in vitro, with the effect being more evident than that of Ad-p53.

CONCLUSION

These results suggest that glioma cell vaccination co-transferred with p53, GM-CSF and B7-1 genes may be a feasible and effective immunotherapeutic approach in glioma treatments.

Flow cytometry and in vitro analysis of human glioma-associated macrophages. Laboratory investigation

OBJECT

To date, glioma immunotherapy has been focused mostly on stimulating antitumor peripheral lymphocyte responses; however, some data suggest that microglia and/or macrophages (not lymphocytes) are the predominant inflammatory cells infiltrating gliomas. To study this hypothesis further, the authors analyzed inflammatory cell infiltrates in fresh human malignant glioma specimens and primary cultures.

METHODS

Single-cell suspensions from fresh operative malignant glioma specimens, obtained by stereotactic localization, were analyzed for CD11b and CD45 by using flow cytometry. A comparison was made with peripheral blood mononuclear cells. In a subset of patients, a more detailed flow cytometry analysis of Class I and II major histocompatibility complex, B7-1, B7-2, CD11c, and CD14 expression was performed. Macrophage-like cells in primary glioma cultures were similarly assessed.

RESULTS

Operative samples were obtained from 9 newly diagnosed malignant gliomas. The mean percent of CD45(+)/CD11b(-) cells (lymphocytes) was 2.48% (range 0.65-5.50%); CD45(dim)/CD11b(+) cells (microglia), 1.65% (range 0.37-3.92%); and CD45(bright)/CD11b+ (monocytes/macrophages), 6.25% (range 1.56-15.3%). More detailed fluorescence-activated cell sorting suggested that macrophage-like cells expressed Class I and II major histocompatibility complex, B7-2, and CD11c but not CD14 or B7-1. Primary human glioma cultures contained significant numbers of macrophage-like (CD45(bright)/CD11b(+)) cells, but these cells were lost with successive passages. These cells maintained the immunomarker profiles of macrophage-like cells from fresh specimens only if they were cultured in serum-free media.

CONCLUSIONS

The CD45(+)/CD11b(+) cells are the predominant inflammatory cell infiltrating human gliomas. Of this type, the CD45(bright)/CD11b(+) cells, a phenotype compatible with circulating macrophages in rodent models, and not microglia, are the most common. Their immunomarker profile is compatible with an immature antigen-presenting cell. They are present in primary glioma cultures but are lost in successive passages. Their role is enigmatic, and they may prove an important target for future glioma immunotherapy studies.

Technical hurdles in a pilot clinical trial of combined B7-2 and GM-CSF immunogene therapy for glioblastomas and melanomas

OBJECTIVE

Malignant glioblastomas and melanomas continue to have a dismal prognosis despite advances in conventional therapy. This has led to investigations of novel treatment strategies including immunogene therapy. We report a pilot clinical trial of combined B7-2 and GM-CSF immunogene therapy for gliomas and melanomas and discuss technical hurdles encountered.

METHODS

Patients with recurrent malignant gliomas or medically refractory melanomas were vaccinated with irradiated autologous tumor cells transduced with B7-2 and GM-CSF genes using a retroviral vector. Patients were monitored for toxicity, inflammatory/immune reactions, and clinical status.

RESULTS

Vaccine preparation was attempted from 116 malignant glioma and 32 melanoma specimens. Adequate vaccines could only be prepared for five glioblastoma and three melanoma patients. Six patients (three recurrent glioblastomas and three melanomas) were actually vaccinated. Minor toxicities included flu-like symptoms (3/6), injection site erythema (4/6), and asymptomatic elevations in liver enzymes (3/6). Most patients showed evidence of an inflammatory response but specific anti-tumor immunity was not demonstrated. All six patients have died, although three patients with minimal residual disease at treatment had prolonged recurrence-free intervals after vaccination.

CONCLUSIONS

Combined B7-2 and GM-CSF immunogene therapy for glioblastomas and melanomas using autologous tumor cells has many technical pitfalls hindering large scale application and evaluation. As a result, this pilot study was too limited to draw meaningful conclusions regarding safety or anti-tumor immunity. While immunotherapy has been promising in pre-clinical studies, alternate strategies will be required to bring these benefits to patients.

A unique model system for tumor progression in GBM comprising two developed human neuro-epithelial cell lines with differential transforming potential and coexpressing neuronal and glial markers

The molecular mechanisms involved in tumor progression from a low-grade astrocytoma to the most malignant glioblastoma multiforme (GBM) have been hampered due to lack of suitable experimental models. We have established a model of tumor progression comprising of two cell lines derived from the same astrocytoma tumor with a set of features corresponding to low-grade glioma (as in HNGC-1) and high-grade GBM (as in HNGC-2). The HNGC-1 cell line is slow-growing, contact-inhibited, nontumorigenic, and noninvasive, whereas HNGC-2 is a rapidly proliferating, anchorage-independent, highly tumorigenic, and invasive cell line. The proliferation of cell lines is independent of the addition of exogenous growth factors. Interestingly, the HNGC-2 cell line displays a near-haploid karyotype except for a disomy of chromosome 2. The two cell lines express the neuronal precursor and progenitor markers vimentin, nestin, MAP-2, and NFP160, as well as glial differentiation protein S100beta. The HNGC-1 cell line also expresses markers of mature neurons like Tuj1 and GFAP, an astrocytic differentiation marker, hence contributing toward a more morphologically differentiated phenotype with a propensity for neural differentiation in vitro. Additionally, overexpression of epidermal growth factor receptor and c-erbB2, and loss of fibronectin were observed only in the HNGC-2 cell line, implicating the significance of these pathways in tumor progression. This in vitro model system assumes importance in unraveling the cellular and molecular mechanisms in differentiation, transformation, and gliomagenesis.

Rat strain differences in the ectopic osteogenic potential of recombinant human BMP adenoviruses

Different animal strains have different genetic backgrounds that influence their physiological function and pathological process. The differences in genetic background may affect the efficiency of adenoviral infection and target gene expression and further cause different gene therapy results when target genes are delivered with adenoviral vectors. In this study, ectopic bone was not seen in ADCMVBMP4 injection sites, but was formed in ADCMVBMP9 injection sites in all rat strains. The mean volumes of bone induced with ADCMVBMP9 were 0.87 +/- 0.2 cm3 in Wistar, 0.26 +/- 0.1 cm3 in Long-Evans, 0.34 +/- 0.2 cm3 in Sprague-Dawley, 0.44 +/- 0.1 cm3 in ACI, 0.66 +/- 0.2 cm3 in PVG, and 0.58 +/- 0.1 cm3 in Fischer 344 rats. This indicates that ADCMVBMP9 has different bone formation potentials in different immunocompetent rat strains (P = 0.02). The basic levels of CD4+ and CD8+ T cells in blood before viral infection and titers of adenoviral neutralizing antibodies 30 days post-viral infection were significantly different among rat strains (P < 0.01). The efficiencies of target gene expression delivered with adenovirus were also significantly different in primary muscle cell cultures from different rat strains (P < 0.01). The different osteogenic potentials of ADCMVBMP9 among rat strains may be, in part, due to the differences in immune factors and target gene expression efficiency in muscle tissue.

Proliferative activity and in vitro replication of HSV1716 in human metastatic brain tumours

BACKGROUND

The neurotropic herpes simplex virus mutant HSV1716 lacks the gene encoding the virulence factor ICP34.5 and cannot replicate in non-dividing cells where proliferating cell nuclear antigen (PCNA) is not actively engaged in cellular DNA synthesis. In the brain, tumoral expression of PCNA therefore confers on it oncolytic specificity and may determine its efficacy. Three phase I trials in glioma patients and one in metastatic melanoma patients have established that HSV1716 is safe and replicates selectively in tumour tissue. Here we examine the in situ PCNA profiles of common human metastatic brain tumours and determine their in vitro permissivity for HSV1716 replication to ascertain their suitability for HSV1716 therapy.

METHODS

Histological sections of tumour biopsies obtained from patients undergoing craniotomies were stained for PCNA expression. The replicative ability of HSV wild-type (17(+)) and mutant (1716) viruses was assessed in tissue cultures of the same tumour biopsies and in cancer cell lines by plaque assay.

RESULTS

Biopsies of all 10 metastatic tumours (3 melanoma, 4 carcinoma and 3 adenocarcinoma) as well as 4 glioblastoma multiforme were positive for PCNA immunoexpression and supported the replication of HSV1716. The PCNA-positive cells in the metastatic tumours were distributed comparatively in larger and more contiguous areas than in glioblastoma (1.69 +/- 1.61 mm(2) vs. 0.73 +/- 0.77 mm(2)) and numbered 29.0 +/- 12.4 and 12.6 +/- 4.7%, respectively.

CONCLUSIONS

The results show that human cerebral metastatic tumours have generally larger and more contiguous proliferative areas, support efficient HSV1716 replication, and are thus potential candidates for such oncolytic viral therapy.

Cancer immunogene therapy: a review

Although immunotherapy has long held out promise as a specific, potent approach to cancer therapy, clinical applications have been unrewarding to date. However, advances in gene transfer technology and basic immunology have opened new avenues to stimulate antitumor immune responses including immunogene therapy. Many different approaches to immunogene therapy have been identified. These include transferring genes encoding proinflammatory proteins to tumor cells, suppressing immunosuppressive gene expression, and transferring proinflammatory genes and/or tumor antigen genes to professional antigen-presenting cells. In some cases, genes are transferred to tumor or antigen-presenting cells in situ. In others, gene transfer is performed ex vivo as part of preparing an anticancer vaccine. We discuss the underlying approach, relative success, and clinical application of various cancer immunogene therapy strategies, paying particular attention to immunogene therapy vaccines. Large numbers of preclinical studies have been reported, but only scattered clinical trial results have appeared in the literature. Although very successful preclinically, the ideal cancer immunogene therapy approach remains to be determined and will likely vary with tumor type. Clinical impact may be improved in the future as treatment protocols are refined.

Human autologous in vitro models of glioma immunogene therapy using B7-2, GM-CSF, and IL12

BACKGROUND

Cancer immunogene therapy is based on vaccination with radiated, autologous tumor cells transduced with immunostimulatory genes. To help determine an optimal glioma immunogene therapy strategy, we stimulated lymphocytes with autologous human glioma cells transduced with B7-2 (CD86), granulocyte-macrophage colony-stimulating factor (GM-CSF), and/or interleukin-12 (IL12).

METHODS

A human glioma-derived cell culture (Ed147.BT) was transduced with B7-2, GM-CSF, and/or IL12 using retroviral vectors. Autologous peripheral blood mononuclear cells (PBMC) were co-cultured with irradiated gene-transduced tumor alone or a combination of radiated wild type and gene-transduced cells. Peripheral blood mononuclear cells proliferation was determined by serial cell counts. Peripheral blood mononuclear cells phenotype was assessed by flow cytometry for CD4, CD8, and CD16. Anti-tumor cytotoxicity was determined by chromium-51 (51Cr) release assay.

RESULTS

Peripheral blood mononuclear cells cell numbers all decreased during primary stimulation but tumor cells expressing B7-2 or GM-CSF consistently caused secondary proliferation. Tumors expressing B7-2 and GM-CSF or B7-2, GM-CSF, and IL12 consistently increased PBMC CD8+ (cytotoxic T) and CD16+ (natural killer) percentages. Interestingly, anti-tumor cytotoxicity only exceeded that of PBMC stimulated with wild type tumor alone when peripheral blood mononuclear cells were stimulated with both wild type tumor and B7-2/GM-CSF- (but not IL12) transduced cells.

CONCLUSIONS

PBMC proliferation and phenotype is altered as expected by exposure to immunostimulatory gene-transduced tumor. However, transduced tumor cells alone do not stimulate greater anti-tumor cytotoxicity than wild type tumor. Only B7-2/GM-CSF-transduced cells combined with wild type produced increased cytotoxicity. This may reflect selection of tumor subclones with limited antigenic spectra during retrovirus-mediated gene transfer.

Invasion of human glioma biopsy specimens in cultures of rodent brain slices: a quantitative analysis

OBJECT

The reliable assessment of the invasiveness of gliomas in vitro has proved elusive, because most invasion assays inadequately model in vivo invasion in its complexity. Recently, organotypical brain cultures were successfully used in short-term invasion studies on glioma cell lines. In this paper the authors report that the invasiveness of human glioma biopsy specimens directly implanted into rodent brain slices by using the intraslice implantation system (ISIS) can be quantified with precision. The model was first validated by the demonstration that, in long-term studies, established glioma cells survive in the ISIS and follow pathways of invasion similar to those in vivo.

METHODS

Brain slices (400 microm thick) from newborn mice were maintained on millicell membranes for 15 days. Cells from two human and one rodent glioblastoma multiforme (GBM) cell lines injected into the ISIS were detected by immunohistochemistry or after transfection with green fluorescent protein-containing vectors. Preferential migration along blood vessels was identified using confocal and fluorescent microscopy. Freshly isolated (< or = 24 hours after removal) 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate-prelabeled human glioma biopsy specimens were successfully implanted in 19 (83%) of 23 cases, including 12 GBMs and seven lower grade gliomas (LGGs). Morphometric quantification of distance and density of tumor cell invasion showed that the GBMs were two to four times more invasive than the LGGs. Heterogeneity of invasion was also observed among GBMs and LGGs. Directly implanted glioma fragments were more invasive than spheroids derived from the same biopsy specimen.

CONCLUSIONS

The ISIS combines a high success rate, technical simplicity, and detailed quantitative measurements and may, therefore, be used to study the invasiveness of biopsy specimens of gliomas of different grades.

Human brain tumor cell culture characterization after immunostimulatory gene transfer

OBJECTIVE

Immunogene therapy is a novel cancer treatment strategy based on vaccination with irradiated autologous tumor cells transduced with immunostimulatory genes. To characterize such cells before clinical applications, we studied a human glioma cell line (D54 MG) and early passage human glioma (Ed147.BT, Ed149.BT) and melanoma (Ed141.MEL) cultures after immunostimulatory gene transfer.

METHODS

Granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-12 (IL-12), and B7-2 genes were retrovirally transferred to tumor cells. Gene expression before and after irradiation (200 Gy) was assessed by enzyme-linked immunosorbent assay (GM-CSF, IL-12) and flow cytometry (B7-2). Viability and clonogenicity were determined via trypan blue staining before and after irradiation. Growth rates were determined by serial cell counts.

RESULTS

GM-CSF expression was high in GM-CSF-transduced (10.36-162.10 ng/10(6) cells/d preirradiation and 10.22-122.02 ng/10(6) cells/d postirradiation) but lower in B7-2/GM-CSF-transduced cultures (1.41-2.90 ng/10(6) cells/d preirradiation, 1.96-5.02 ng/10(6) cells/d postirradiation). IL-12 expression also was lower (1.30-2.10 ng/10(6) cells/d preirradiation, 0.47-1.70 ng/10(6) cells/d postirradiation). B7-2 expression was high (one- to two-logarithm increase in fluorescence) and unaffected by radiation. Postirradiation viability was initially high (94.20 +/- 8.46%, Day 1) but decreased rapidly (28.13 +/- 4.64%, Day 10). No cultures demonstrated evidence of clonogenicity (i.e., cell division) after 200-Gy irradiation. Growth rates were similar in wild-type and gene-transduced Ed141.MEL, Ed147.BT, and Ed149.BT. However, D54MG-IL-12 growth was slower than that of wild-type D54MG.

CONCLUSION

GM-CSF, IL-12, and B7-2 genes can be transferred to human glioma and melanoma cell cultures efficiently by use of our retroviral vectors. Irradiation (200 Gy) does not significantly alter therapeutic gene expression. Irradiated cells remain viable for several days but cannot undergo further cell division. Early passage culture growth rates are not altered by therapeutic gene expression but are decreased by IL-12 in an immortalized cell line (D54MG). These results suggest that it is feasible to create vaccines with irradiated, autologous, genetically modified brain tumor cells.

Human glioma immunobiology in vitro: implications for immunogene therapy

OBJECTIVE

Human gliomas are known to be immunosuppressive. Recent reports have suggested novel strategies to overcome this immunosuppression, including immunogene therapy. We examined expression of 10 immunologically important molecules by human gliomas in vitro, and we discuss the implications for immunogene therapy.

METHODS

Early passage human glioma cultures and established human glioma cell lines were analyzed by flow cytometry for expression of Class I and II major histocompatibility complex (MHC), B7-2 (CD86), and Fas (CD95). Culture supernatants were assayed by enzyme-linked immunosorbent assay for interleukin (IL)-6, IL-10, IL-12, transforming growth factor beta2, prostaglandin E2, and granulocyte-macrophage colony-stimulating factor levels.

RESULTS

All cultures (16 of 16 samples) expressed Class I MHC and Fas, but few expressed Class II MHC (1 of 16 samples) or B7-2 (0 of 16 samples). Nearly all expressed high levels of IL-6 (19 of 21 samples; mean, 36.5 +/- 10.8 ng/10(6) cells/d) and prostaglandin E2 (21 of 21 samples; mean, 15.6 +/- 4.5 ng/10(6) cells/d) levels, and many expressed transforming growth factor beta2 (13 of 21 samples; mean, 8.6 +/- 3.7 ng/10(6) cells/d). Although several cultures (6 of 14 samples) expressed granulocyte-macrophage colony-stimulating factor, expression levels were very low (mean, 0.2 +/- 0.1 ng/10(6) cells/d). Few cultures (4 of 21 samples) expressed measurable IL-10, and none (0 of 22 samples) expressed IL-12.

CONCLUSION

Class I MHC and Fas expression suggests that human glioma cells may be susceptible to Class I MHC-dependent cytotoxic T cell recognition and Fas-mediated killing. Unfortunately, transforming growth factor beta2 and prostaglandin E2 probably impair T cell activation, and IL-6 may shift immunity to less effective humoral (T helper 2) responses. Proinflammatory gene expression (B7-2, granulocyte-macrophage colony-stimulating factor, and/or IL-12) is lacking. Together, these results suggest that modifying glioma cells via proinflammatory gene transfer or immunoinhibitory gene suppression might stimulate immune responses that are effective against unmodified tumors.

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.

Gene gun transfection of human glioma and melanoma cell lines with genes encoding human IL-12 and GM-CSF

We used particle-mediated gene transfer by a custom-built gene gun to transfect two well-established human glioma (D54MG and U251) and melanoma (SK mel 28 and Ed 141) cell lines, as well as two glioma lines locally established from primary patient tumors (Ed 147 and Ed 149). Using beta-galactosidase as a reporter gene, D54MG, U251, Ed 141 and SK mel 28 showed an average transfection efficiency of 15-40%, whereas Ed 147 and Ed 149 had mean transfection efficiencies of 3% and 5% respectively. Twenty-four hours after transfection with the gene encoding human interleukin-12 (IL-12), ELISA was performed on cell supernatants (mean of n = 12 for each cell line). IL-12 expression was extremely variable between the different cell lines, ranging from 52 to 1,151 pg/10(6) cells/24 h. Results were very similar when cells were exposed to 20,000 rads of gamma irradiation 2 h after transfection. When the cell lines were transfected with human granulocyte-macrophage colony-stimulating factor, 24 h levels were: 13.0 (Ed 147), 17.8 (Ed 149), 18.6 (Ed 141), 27.4 (D54MG) and 27.7 ng/10(6) cells/24h (U251). SK mel 28 produced 88.1 ng/10(6) cells/24 h. We conclude that the gene gun can efficiently transfect a variety of immortalized, well-established and locally-established glioma and melanoma cell lines. High dose gamma irradiation does not adversely affect the expression of the foreign gene (IL-12) at 24 h. Significantly, transfected cell lines show different levels of expression depending on the particular gene/plasmid introduced. Therefore, each cell line has to be assessed individually for the level of expression of each introduced gene.