The effects of human recombinant tumor necrosis factor on glioma-derived cell lines: cellular proliferation, cytotoxicity, morphological and radioreceptor studies

Effect of tumour necrosis factor-alpha and irradiation alone or in combination on the viability of hepatocellular and biliary adenocarcinoma cell lines in vitro

BACKGROUND

Tumour necrosis factor alpha (TNF-alpha) may exhibit antitumoral activity and can influence the reaction of both tumour and normal tissue to radiation.

AIMS

To test the effect of TNF-alpha and/or irradiation on hepatocellular (HepG2, Hep3B, Sk-Hep1, HuH7) and cholangiocellular (Sk-chA1, Mz-chA1) tumour cell lines.

METHODS

Colony formation, apoptosis analysis and trypan blue exclusion were used to assess cell viability. Doses of radiation (2-25 Gy) and TNF-alpha (100-50,000 U) as well as their respective sequencing were varied (24 and 12 h before and 6 h after). The expression of TNF-alpha and TNF receptors 1/2 was determined using real-time polymerase chain reaction and IkappaBalpha protein expression was detected by Western blot.

RESULTS

Sole irradiation induced a reduction in colony formation in all cell lines and sole TNF-alpha in HepG2 and Sk-chA1 cells only. No difference in apoptosis induction after TNF-alpha or irradiation was observed. Cellular death induced by the combination of TNF-alpha and radiation was not superior to the use of any of the two agents alone. All cell lines revealed that radiation induced upregulation of TNF-alpha whereas the extent of TNF receptor-specific transcription did not change. Furthermore, radiation-induced changes in IkappaBalpha expression were not detectable.

CONCLUSIONS

Our data suggest that both TNF-alpha and radiation may be treatment options for hepatocellular and cholangiocellular carcinomas. Because TNF-alpha and radiation do not interact in terms of radiosensitization, anti-TNF-alpha treatment may have the potential to protect against hepatocellular injury after abdominal irradiation. However, further in vivo studies are needed to confirm that anti-TNF-alpha treatment does not compromise tumour control and actually attenuates radiation-induced liver injury.

Mitochondrial thioredoxin-2 has a key role in determining tumor necrosis factor-alpha-induced reactive oxygen species generation, NF-kappaB activation, and apoptosis

Tumor necrosis factor-alpha (TNF-alpha) is a cytokine that is involved in numerous pathologies, in part through stimulation of the mitochondrial production of reactive oxygen species (ROS). Previous studies show that in addition to mitochondrial superoxide dismutase- and glutathione-dependent systems, mitochondria also contain thioredoxin-2 (Trx2), an antioxidant protein that can detoxify ROS. The purpose of this study was to determine whether Trx2 protects against oxidative damage triggered by TNF-alpha. After a 30-min treatment in HeLa cells, TNF-alpha (5-40 ng/ml) oxidized Trx2 but not cytoplasmic Trx1. Preferential, significant Trx2 oxidation occurred within 10 min of TNF-alpha treatment. Moreover, overexpression of Trx2, but not Trx1, decreased TNF-alpha-induced ROS generation, suggesting mitochondrial compartmentation of ROS production and subsequent specific detoxification by Trx2, not Trx1. Overexpression of Trx2 or the active-site mutant C93S Trx2 was used to evaluate their downstream effects following TNF-alpha stimulation. Results showed that nuclear translocation of NF-kappaB was inhibited with Trx2 overexpression but not with the dominant negative active-site mutant C93S Trx2. Moreover, when cotransfected with a NF-kappaB-luciferase reporter and then treated with TNF-alpha, NF-kappaB activity was significantly attenuated with Trx2 overexpression but not with C93S Trx2 expression. Trx2 overexpression, but not C93S Trx2, significantly inhibited TNF-alpha-induced apoptosis as measured by terminal dUTP nick-end labeling assay. These findings support the interpretation that mitochondrial-generated ROS is a principal component in TNF-alpha-induced effects and that Trx2 blocks TNF-alpha-induced ROS generation and downstream NF-kappaB activation and apoptosis.

Reactive oxygen intermediates in TNF signaling

Tumor necrosis factor (TNF) is arguably the most potent inducer of several intracellular signals, including apoptosis, cell differentiation, and gene transcription. It does so through the activation of caspases, specific kinases including mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK), transcription factors Activated protein 1 (AP-1), and nuclear factor kappa-B (NF-kappaB). By activating these signals, TNF mediates pro-apoptotic and pro-survival mechanisms in the cell. It has also been suggested that TNF mediates its intracellular signaling by adjusting the redox potential of the cell, specifically through reactive oxygen intermediates (also known as reactive oxygen species). Here we review the evidence linking ROI to TNF-induced signaling and propose that ROI mediate both pro-apoptotic and pro-survival signals. How these antagonistic signals are balanced to maintain homeostasis is still not clear.

Cellular mechanisms for the repression of apoptosis

Apoptosis, also known as programmed cell death, is a ubiquitous mode of cell death known to play an important role during embryogenesis, development, and adult cellular homeostasis. Disruption of this normal physiological cell death process can result in either excessive or insufficient apoptosis, which can lead to various disease states and pathology. Since most cells contain the machinery that brings about apoptosis, it is clear that living cells must contain inherent repressive mechanisms to keep the death process in check. In this review, we examine several modes of repression of apoptosis that exist in cells.

The role of the Bcl-2 family in the regulation of outer mitochondrial membrane permeability

Mitochondria are well known as sites of electron transport and generators of cellular ATP. Mitochondria also appear to be sites of cell survival regulation. In the process of programmed cell death, mediators of apoptosis can be released from mitochondria through disruptions in the outer mitochondrial membrane; these mediators then participate in the activation of caspases and of DNA degradation. Thus the regulation of outer mitochondrial membrane integrity is an important control point for apoptosis. The Bcl-2 family is made up of outer mitochondrial membrane proteins that can regulate cell survival, but the mechanisms by which Bcl-2 family proteins act remain controversial. Most metabolites are permeant to the outer membrane through the voltage dependent anion channel (VDAC), and Bcl-2 family proteins appear to be able to regulate VDAC function. In addition, many Bcl-2 family proteins can form channels in vitro, and some pro-apoptotic members may form multimeric channels large enough to release apoptosis promoting proteins from the intermembrane space. Alternatively, Bcl-2 family proteins have been hypothesized to coordinate the permeability of both the outer and inner mitochondrial membranes through the permeability transition (PT) pore. Increasing evidence suggests that alterations in cellular metabolism can lead to pro-apoptotic changes, including changes in intracellular pH, redox potential and ion transport. By regulating mitochondrial membrane physiology, Bcl-2 proteins also affect mitochondrial energy generation, and thus influence cellular bioenergetics. Cell Death and Differentiation (2000) 7, 1182 - 1191

Expression of superoxide dismutases, catalase, and glutathione peroxidase in glioma cells

Four primary antioxidant enzymes were measured in both human and rat glioma cells. Both manganese-containing superoxide dismutase (MnSOD) and copper-zinc-containing superoxide dismutase (CuZnSOD) activities varied greatly among the different glioma cell lines. MnSOD was generally higher in human glioma cells than in rat glioma cells and relatively higher than in other tumor types. High levels of MnSOD in human glioma cells were due to the high levels of expression of MnSOD mRNA and protein. Heterogeneous expression of MnSOD was present in individual glioma cell lines and may be due to subpopulations or cells at different differentiation stages. Less difference in CuZnSOD, catalase, or glutathione peroxide was found between human and rat glioma cells. The human glioma cell lines showed large differences in sensitivity to the glutathione modulating drugs 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU) and buthionine sulfoximine (BSO). A good correlation was found between sensitivity to BCNU and the activities of catalase in these cell lines. Only one cell line was sensitive to BSO and this line had low CuZnSOD activity.

TNF-induced signaling in apoptosis

Out of the almost 17 members of the TNF superfamily, TNF is probably the most potent inducer of apoptosis. TNF activates both cell-survival and cell-death mechanisms simultaneously. Activation of NF-kB-dependent genes regulates the survival and proliferative effects pf TNF, whereas activation of caspases regulates the apoptotic effects. TNF-induced apoptosis is mediated primarily through the activation of type I receptors, the death domain of which recruits more than a dozen different signaling proteins, which together are considered part of an apoptotic cascade. This cascade does not, however, account for the role of reactive oxygen intermediates, ceramide, phospholipases, and serine proteases which are also implicated in TNF-induced apoptosis. This cascade also does not explain how type II TNF receptors which lack the death domain, induce apoptosis. Nevertheless, this review of apoptosis signaling will be limited to those proteins that makeup the cascade.

Receptor expression, cytogenetic, and molecular analysis of six continuous human glioma cell lines

Six human glioma cell lines were established from tissues obtained from five patients diagnosed with Kernohan grade IV glioblastoma multiforme and one from a patient with a grade II astrocytoma. One line was from a recurrent patient who had received prior therapy; the other lines were derived from patients at initial diagnosis and/or before cytoreductive therapies other than surgery were given. Considerable variability in phenotypic, karyotypic, and cell surface marker expression was displayed between the six human glioma cell lines. The karyotypes ranged from apparently normal (grade II astrocytoma) to those with complex rearrangements. Trisomy of chromosome 7 was the most common abnormality. The extensive cytogenetic and molecular characterization of these lines may facilitate their utilization in cellular and molecular biologic studies.

Morphological change in tumor endothelial cells induced by natural-type human tumor necrosis factor

The effects of natural-type human tumor necrosis factor (nh-TNF) on tumor endothelial cells of experimental brain tumors were investigated electron microscopically. Tumor vessels with hypertrophic endothelial cells were observed 12 and 24 hr after an intralesional administration of 5,000 U of nh-TNF. Increased biosynthetic organelles such as the Golgi complex and rough endoplasmic reticulum were evident in the plump cytoplasms. These endothelial cells resembled those in high endothelial venules (HEV) functionally characterized by the high permeability of leukocytes. In addition, close interactions between these endothelial cells and leukocytes were observed. Our findings indicated that nh-TNF could promote the morphological change in tumor endothelial cells into HEV-like cells.

Growth inhibition in clonal subpopulations of a human epithelioid sarcoma cell line by retinoic acid and tumour necrosis factor alpha

Epithelioid sarcoma is a highly malignant soft tissue tumour that is refractory to conventional chemotherapy and irradiation. Since permanent cell lines of this tumour are extremely rare, in vitro data on compounds with significant antiproliferative effects are still lacking. Therefore, we investigated the effects of retinoic acid (RA) and tumour necrosis factor alpha (TNF-alpha) on tumour cell proliferation of three different clonal subpopulations (GRU-1A, GRU-1B, GRU-1C) derived from the same human epithelioid sarcoma cell line, GRU-1. In GRU-1A both RA (P=0.01) and TNF-alpha (P=0.002) exhibited highly significant and dose-dependent growth inhibitory effects, which could further be increased by a combined application of both compounds (P<0.006). GRU-1B proved to be sensitive to RA (P=0.006), whereas no response to TNF-alpha was observed. GRU-1C was resistant to both RA and TNF-alpha. The antiproliferative effect of TNF-alpha was mediated by TNF receptor 1(TNF-R1) and correlated positively with both the number of TNF-R1 per cell and receptor affinity. No correlation was detected between RA-induced growth inhibition and the expression pattern of the RA receptors (RARs) RAR-alpha, RAR-beta, and RAR-gamma. Plating efficiency, however, could exclusively be reduced by RA in GRU-1B, the only cell line expressing RAR-alpha. Taken together, these data are the first showing significant antiproliferative effects in human epithelioid sarcoma by RA and TNF-alpha. Whereas the TNF-alpha response seems to depend on the expression of TNF-R1, no simple correlation could be found between RA sensitivity and the expression pattern of RARs.

Cytokines and tumors of the central nervous system

Cytokines are a group of molecules with an extremely broad range of activities on a variety of target cells. This review summarizes the known cytokine and cytokine receptor expression in primary brain tumors and derived cell lines. These expression patterns are compared with those occurring in other CNS diseases, such as virus or bacterial infections, experimental allergic encephalitis, multiple sclerosis, and trauma. A variety of cytokines are expressed during CNS neoplasia; their potential involvement in tumor growth through a variety of mechanisms, such as autocrine or paracrine growth stimulation, angiogenesis, and immune surveillance evasion, are discussed. Finally, results of preliminary therapeutic approaches with cytokines are critically evaluated.

Transfection of cells with basic fibroblast growth factor and Kaposi fibroblast growth factor genes induce resistance to and receptor modulation of tumor necrosis factor

Tumor necrosis factor (TNF) has been shown to inhibit the growth of some cell types and stimulate the proliferation of others by a mechanism that is not understood. In the present study, we investigated the effect of transfection of NIH-3T3 cells with either the basic fibroblast growth factor gene (bFGF) or the kaposi FGF gene (K-fgf) on the growth-modulatory effects of TNF. Our results show that transformation of cells with either gene leads to resistance to the growth-inhibitory effects of TNF. The K-fgf gene was found to be a more potent inducer of cellular resistance than the bFGF gene. The cellular resistance correlated with the inhibition of TNF-induced activation of phospholipase A2 and down-modulation of TNF receptors. Overall, our results indicate that both K-fgf and bFGF play an important role in suppression of antiproliferative effects of TNF.

Detection of tumor necrosis factor-alpha protein and messenger RNA in human glial brain tumors: comparison of immunohistochemistry with in situ hybridization using molecular probes

Tumor necrosis factor-alpha (TNF alpha) protein and messenger (m)RNA distribution was studied in biopsy samples of glial brain tumors, using immunohistochemistry and in situ hybridization with molecular probes, to investigate the role of this cytokine in tumor proliferation and immunological host defense. Focal expression of TNF alpha was detected in four of four glioblastomas, one of two anaplastic astrocytomas, and four of five low-grade astrocytomas, regardless of their subtype or grade of malignancy, but in none of the normal peritumoral brain tissues used as controls. The TNF alpha protein and mRNA were present in reactive astrocytes and protoplasmic tumor cells, confined to areas of leukocyte or T-lymphocyte infiltrating, and less pronounced in tumor cells at the edge of necrosis. Additionally, TNF alpha reactivity was found in infiltrating macrophages and perivascular microglia. Immunohistochemistry and in situ hybridization for TNF alpha showed comparable reaction patterns and numbers of TNF alpha-positive cells, even though the sensitivity of in situ hybridization was significantly higher. Quantitative evaluation of TNF alpha protein, TNF alpha mRNA, and leukocyte infiltration revealed a significant positive correlation between the TNF alpha-positive reactive astrocytes and the number of lymphocytes present in corresponding areas. Together, these data lead to the conclusion that TNF alpha in reactive astrocytes and monocytic cells within tumor areas of high leukocyte infiltration and in tumor cells at the border of necrosis may represent one defense pathway of the immune system against tumor proliferation.

Growth-inhibiting effect of intratumoral recombinant human tumor necrosis factor on an experimental model of primitive neuroectodermal tumor

The effect of intratumoral administration of recombinant human tumor necrosis factor on an experimental model of primitive neuroectodermal neoplasia was studied. A clear inhibition of tumor growth was achieved by immunotherapy that consisted in intralesion injections of 100 micrograms of tumor necrosis factor daily, the first three days of each week, for a period of four weeks. At this time, tumor size was 2.21 +/- 0.66 cm2 (mean +/- standard deviation) in the treated group, versus 7.62 +/- 0.43 cm2 in the control group. These data support previous studies on the influence of tumor necrosis factor on the development of ethyl-nitrosourea-induced tumors, and suggest the potential usefulness of this cytokine in human primitive neuroectodermal neoplasms.

Immunological fluctuations during intrathecal immunotherapy in three patients affected by CNS tumours disseminating via CSF

The immunological therapy of cancer has been proposed in a number of neoplasms (Borden, Sondel, 1989; Foon, 1989; Rosenberg, 1992) and has recently been adopted in the treatment of Central Nervous System (CNS) tumors in combination with conventional surgical and radiotherapeutical approach. In this context, loco-regional administration of immunomodulating agents (for instance in post-surgical cavity) allows to achieve much higher in situ concentrations than by systemic route. Since these treatments have potential adverse effects, careful assessment of clinical and immunological parameters in phase I trials is needed. CNS tumors disseminating via Cerebrospinal Fluid (CSF) pathways offer a stimulating opportunity for intrathecal immunotherapy. In this context, alpha-IFN and IL2 (alone or in combination with LAK cells) have been employed either loco-regionally or intrathecally (Merchant, Mc Vicar, Merchant & Young, 1992; Schiller, Hank, Storer, Borchert, Moore, Albertini, Bechhofer, Wesley, Brown, Bastin & Sondel, 1993). The rationale for the use of both these substances includes the known anti-tumor action of alpha-IFN (Mahaley, Urso, Whaley, Blue, Williams, Guaspari & Selker, 1985; Nagai, 1988) and the ability of r-IL2 to generate activated cells effective in lysing tumor cell targets (Hayes, Moore, Pierz, Chen, Da Rosso, Nirenberg & Allen, 1993). We treated 3 patients (2 affected by disseminating cerebellar medulloblastoma, 1 by disseminating thalamic glioblastoma) by intrathecal r-IL2 via recervoir. In the first 2 patients, this treatment was preceded by alpha-IFN (also intrathecally). Monitoring of immunological effects of the treatment schedule involved kinetics of CSF and serum TNF-alpha, IL2s and IL2R during the first day of r-IL2 treatment, as well as on day +2 and +4 of both r-IL2 cycles, and assessment of CSF cells, protein and CSF and PB NK cell activity and CD3-CD56+ cells during the course of all treatment cycles. We also assessed clinical and neuroradiological effects of immunotherapy.

Influence of the postnatal administration of tumor necrosis factor plus interferon-alpha 2b on the development of ethyl-nitrosourea-induced brain tumors in rats

Using the experimental model of brain tumors induced by ethyl-nitrosourea (ENU), interferon-alpha 2b and human recombinant tumor necrosis factor-alpha (TNF) have been administered to Wistar rats between 100 and 130 days of life (one injection each week, by intraperitoneal route, of 100 micrograms of TNF and 10(4) IU of interferon-alpha 2b, in a total volume of 1 ml per injection). The results obtained suggest, that at this time, this association achieves a reduction in the number of so-called 'malignant schwannomas', but it does not influence the time of appearance nor the number of so-called 'malignant schwannomas', but it does not influence the time of appearance nor the number of so-called 'oligodendroglioma-like tumors'. On the basis of previous observations about cytokine modulation of these ENU-induced neoplasms, a different course of time for obtaining a postnatal biomodulation of both type of tumors is suggested.

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.

Modulation of proliferation and antigen expression of a cloned human glioblastoma by interleukin-4 alone and in combination with tumor necrosis factor-alpha and/or interferon-gamma

As part of continuing studies to investigate the possible regulatory effects of cytokines on malignant astrocytes, we investigated the effects of interleukin-4 (IL-4) alone and in combination with tumor necrosis factor-alpha (TNF alpha) and/or interferon-gamma (IFN gamma) on the cell growth and major histocompatibility complex (MHC) antigen expression of a cloned human glioblastoma cell line (9C). The 9C cells were treated with IL-4 alone or in combination with TNF alpha and/or IFN gamma and were examined for proliferation by crystal violet assay and for Class II MHC antigen by flow cytometry. Results indicated that IL-4 alone did not affect 9C proliferation. In combination with TNF alpha or IFN gamma, however, IL-4 significantly and dose-dependently inhibited cell growth. As previous reports have shown, TNF alpha combined with IFN gamma exerted an additive growth suppressive effect on glioblastoma cells, probably by enhancing TNF receptor expression. This additive effect of TNF alpha and IFN gamma was further enhanced by IL-4. In contrast, IL-4 did not modulate expression of Class II MHC antigen on 9C cells, even in combination with IFN gamma, which predictably enhanced this antigen. These results suggest that IL-4 is capable of modulating glioblastoma growth only in the presence of other cytokines, such as TNF alpha and/or IFN gamma. Further, the effect of IL-4 on glioblastoma proliferation is selective and independent of the mechanisms involved in regulating MHC antigen expression.

Effect of recombinant tumor necrosis factor-alpha on three-dimensional growth, morphology, and invasiveness of human glioblastoma cells in vitro

In order to investigate the antiproliferative and anti-invasive effects of tumor necrosis factor (TNF)-alpha on human glioblastoma cells, an in vitro three-dimensional (anchorage-independent) assay was performed using Matrigel, a mixture of extracellular matrix proteins. Four glioblastoma-derived cell lines, including one cloned line, were cultured in Matrigel with or without TNF-alpha. In the Matrigel containing TNF-alpha, three of the four cell lines, including the cloned line, showed significant growth inhibition in a dose-dependent manner. Dramatic three-dimensional morphological differences were observed between TNF-treated and untreated glioblastoma cells cultured in Matrigel. Untreated cells formed large and highly branched colonies throughout the gel. In contrast, the majority of TNF-treated cells demonstrated truncated branching processes and, at a high TNF-alpha dose, an increasing number of cells remained in relatively small spherical aggregates, their cell processes being significantly reduced. Quantitative invasion assay using a micro-Boyden chamber system confirmed that TNF-treated cells lost invasiveness in a dose-dependent manner. These results suggest that TNF-alpha exerts not only antiproliferative but also anti-invasive effects on human glioblastoma cells in vitro. It is believed that this is the first report showing the anti-invasive effect of TNF-alpha on tumor cells.

Divergent responses of human astrocytoma and non-neoplastic astrocytes to tumor necrosis factor alpha involve the 55 kDa tumor necrosis factor receptor

The effects of tumor necrosis factor (TNF) on DNA synthesis, proliferation, and induction of gene/protein expression of TNF were compared in neoplastic and non-neoplastic adult human astrocytes. Previously, we demonstrated that TNF induced proliferative responses in non-neoplastic adult human astrocytes. In astrocytoma cells, however, TNF elicited both proliferative and cytostatic responses depending upon cell density and TNF concentration. This bimodal effect persisted even in a homogeneous, cloned astrocytoma cell line (STT-9C), and was inhibitable by neutralizing antibody to TNF. TNF treatment enhanced expression of TNF mRNA in astrocytoma cells but not in non-neoplastic astrocytes, and cell-associated or secreted TNF was detectable in any culture. The involvement of receptors in astrocyte responses to TNF was examined in serological studies using monoclonal antibodies Utr-1 to the 75 kDa, and Htr-9 to the 55 kDa TNF receptor. Antibody to the 55 kDa TNF receptor alone was able to mimic the effects of TNF in both neoplastic and non-neoplastic astrocyte cultures while antibody to the 75 kDa TNF receptor had no effect. These data indicate that the bimodal actions of TNF on human astrocytoma cells as well as the stimulatory effects on non-neoplastic adult astrocytes are regulated at least in part by the 55 kDa TNF receptor. Astrocyte TNF receptors, however, do not appear to constitute part of an autocrine growth pathway in either non-neoplastic or neoplastic human astrocytes.

Responses of human glioblastoma cells to human natural tumor necrosis factor-alpha: susceptibility, mechanism of resistance and cytokine production studies

Responses and susceptibility of 14 human glioblastoma cell lines to human natural tumor necrosis factor-alpha (TNF) were studied in vitro. Susceptibility of glioblastoma cells to TNF varied in experimental conditions applied. Most of glioblastoma cell lines were resistant to cytotoxic activity of TNF in a MTT assay at concentrations below 16 U/ml for 72 h exposure. However, TNF at higher dose, in prolonged exposure and against low density of target cells was antiproliferative for certain glioblastoma cultures. TNF exposure at 10 U/ml for 48 h suppressed DNA synthesis in 9 of 14 glioblastoma cultures, but increased in 3 cultures. In addition, colony forming assay showed anti-clonogenic activity of TNF in 5 of 6 glioblastoma cell lines tested. In spite of their low susceptibility to TNF, glioblastoma cells well responded to TNF stimulation at low dose (10 U/ml) for a short period in the absence of cell damage. Productions of Interleukin-6 (IL-6), IL-8-like activity, granulocyte-macrophage colony stimulating factor (GM-CSF), prostaglandin E2 (PGE2) and manganous superoxide dismutase (Mn-SOD) were enhanced or induced by the low-dose TNF stimulation. Mn-SOD, a protein protective against oxidative cell damage, was well induced in time- and dose-dependent manner, however did not correlate with TNF resistance. Whereas the levels of PGE2 in TNF-susceptible cell lines, H-4 and SF-188, were higher than those of other lines. In conclusion, most of glioblastoma cells are resistant to TNF cytotoxic effects, but highly responsive to TNF stimulation. Its effect on glioblastoma cells appears to modulate cell differentiation rather than to kill the cells.

Cellular and cytokine responses of the human central nervous system to intracranial administration of tumor necrosis factor alpha for the treatment of malignant gliomas

To elucidate the role of tumor necrosis factor alpha (TNF alpha) as a biological response modifier, we studied cellular and cytokine responses of the central nervous system to TNF alpha administered intracranially in a phase I clinical trial for patients with malignant gliomas. Six patients received injections of TNF alpha (1.25 x 10(3)-10 x 10(3) U/injection) into the tumor cavities, and regional fluids (RF) and lumbar cerebrospinal fluids (CF) were serially sampled before and after the injections. Recruitment of neutrophils occurred, mostly peaking 8 h after TNF alpha injection, and fewer numbers of CD4+ T cells and monocytes/macrophages migrated, subsequently peaking at 24 h. The CF leukocytosis persisted for 48 h and was associated with an increased level of neutrophil chemotactic activity in the CF. This neutrophil chemotactic activity was attributed to interleukin-8 (IL-8) by HPLC. The level of IL-6 activity in the CF and RF consistently increased; beginning 2 h after TNF alpha injection and reaching the maximum between 8 h and 12 h. It returned to the basal level within 48 h. IL-1 beta was detected in the CF of three patients, its level peaking at 8 h. Prostaglandin E2 also increased after injection of TNF alpha, peaking between 4 h and 12 h and then gradually decreasing. Transforming growth factor beta was found in all cases tested and one patient showed a significant change after TNF alpha injection. IL-2 activity, interferon alpha (INF alpha) activity, IFN beta, and granulocyte/macrophage-colony-stimulating factor were not detected in the CF or RF. In conclusion, TNF alpha is biologically effective in inducing migration of immune cells and generating multiple cytokine responses in the human central nervous system.

Differential effects of tumor necrosis factor-alpha on proliferation, cell surface antigen expression, and cytokine interactions in malignant gliomas

Tumor necrosis factor-alpha (TNF-alpha), a cytokine produced by astrocytes in vivo and in vitro, was tested for its effects on two malignant astrocytoma cell lines (A-172, U-87). Both lines were immunoreactive for glial fibrillary acidic protein, vimentin, Class I antigens, and interleukin-6. The lines differed in their expression of Class II and intercellular adhesion molecule-1 (ICAM-1) antigenic determinants: A-172 cells were negative for both Class II and ICAM-1 antigens, while U-87 cells were intensely positive for Class II and weakly positive for ICAM-1. When these astrocytoma cell lines were exposed to TNF-alpha, A-172 growth was stimulated while U-87 growth was inhibited. Furthermore, in U-87 cells, TNF-alpha enhanced both ICAM-1 and interleukin-1 beta (IL-1 beta) expression, and decreased immunoreactivity for transforming growth factor-beta (TGF-beta) protein. In contrast, in the presence of TNF-alpha, A-172 cells remained negative for IL-1 beta and TGF-beta, but showed an increased expression of ICAM-1. These results demonstrate that TNF-alpha can induce changes in growth rate, cytokine production, and surface antigen expression in malignant astrocytomas; however, the nature of these changes is dependent on the specific characteristics of these malignant astrocytomas. The resultant variability in the immunological microenvironment of these tumors may reflect differences in their growth potential.

Tumour necrosis factor (TNF-alpha) and neurological disorders in HIV infection

Tumour necrosis factor (TNF-alpha) concentrations were determined in the CSF from 42 HIV-infected patients, with or without CNS involvement. In addition, 14 subjects with various neurological disorders but without HIV antibodies were included as controls. Raised CSF concentrations of TNF-alpha (greater than 40 ng/l) were detected both in patients with AIDS dementia complex (ADC) (6/9) and with CNS opportunistic infections (10/19) and, less commonly, in HIV infected subjects without CNS diseases (2/14) and in anti-HIV negative controls (1/14). The highest CSF concentrations of TNF-alpha (greater than 100 ng/l), however, were found in seven out of eight patients with cryptococcal meningitis. Although a role for TNF-alpha in demyelinating lesions associated with ADC has been suggested, our results indicate that a clear elevation of TNF-alpha in the CSF from HIV positive patients mostly occurs in acute inflammatory disorders, such as cryptococcal meningitis.

Evidence for a hyperexcitability state of staggerer mutant mice macrophages

We recently reported an abnormal production of interleukin-1 (IL-1) in peripheral macrophages of several neurological mutant mice that exhibit patterns of neuronal degeneration, especially in the cerebellum. After in vitro activation by lipopolysaccharide acid (LPS), these macrophages hyperexpress IL-1 beta mRNA and hyperproduce IL-1 protein in comparison with +/+ controls. In the present study, focused on the staggerer mutant mice, we investigate if this genetic dysregulation is specific for IL-1 beta or if it reflects a generalized hyperexcitability of these macrophages. The hyperexpression of IL-1 beta mRNA in sg/sg macrophages is present whatever the duration of LPS stimulation, even for periods as short as 15 min, although it reaches a maximum after 4 h of stimulation. The hyperinducibility of sg/sg macrophages is observed even when very low doses of LPS are used (0.01 microgram/ml) and reaches its maximum for 5 micrograms/ml LPS. Synthetic molecules (muramyl dipeptides), such as N-acetylmuramyl-L-alanyl-D-isoglutamine or murabutide, known as macrophage activators, are also efficient in revealing the cytokine hyperexpression in sg/sg macrophages. In addition, hyperexpression of two other cytokines, i.e., tumor necrosis factor-alpha and IL-1 alpha mRNAs, is also detected in LPS-stimulated macrophages of mutant mice. Finally, the effect of an inhibitor of protein synthesis, cycloheximide, is similar in +/+ and sg/sg macrophages. As a whole, these data lead us to conclude that the sg/sg macrophages are in a state of general hyperexcitability when compared with +/+ ones.

Enhancement of epidermal growth factor receptor expression on glioma cells by recombinant tumor necrosis factor alpha

Recombinant tumor necrosis factor alpha (rTNF alpha; optimal dose 1000 U/ml) significantly increased the density of epidermal growth factor receptor (EGF-R) in three of four glioma cell lines in culture as determined by binding analysis of anti-EGF-R monoclonal antibody (mAb) 425. Since enhancement of EGF-R expression by rTNF-alpha was inhibited when cells were treated with the protein synthesis inhibitor cycloheximide, the effects of rTNF alpha may be protein-synthesis-dependent. The dose of rTNF alpha that was optimal for up-regulation of EGF-R on glioma cells did not inhibit the growth of these cells. 125I-labeled mAb 425 lysed glioma cells in culture following its internalization into the cells. After glioma cells had been treated with rTNF alpha, the growth-inhibitory effects of the mAb were significantly enhanced, probably a reflection of the increase in EGF-R density on the tumor cell surfaces. The rTNF alpha effects were specific to the EGF-R and did not affect unrelated glioma-associated antigens. In our previous clinical trials, 125I-labeled mAb 425 showed immunotherapeutic effects in glioma patients. The present study provides the basis for considerations of combined immunotherapy of glioma patients with 125I-labeled mAb 425 and rTNF alpha.

Effects of recombinant human tumor necrosis factor on rodent gliomas and normal brain

In a study examining the possible therapeutic effects of recombinant human tumor necrosis factor-alpha (rHuTNF-alpha) on malignant gliomas without expression of tumor necrosis factor (TNF)-receptors, RG-2 glioma cells were tested in vitro as well as in a rat experimental glioma model. A growth inhibition assay revealed no inhibiting effect in vitro up to a concentration of 20 micrograms/ml rHuTNF-alpha. Receptor-binding studies showed that RG-2 cells did not present specific receptors for rHuTNF-alpha. The pharmacokinetics of rHuTNF-alpha after intravenous injection were studied with respect to serum, tissue, and brain tumor concentrations and showed increased glioma concentrations of (mean +/- standard error of the mean) 0.47 +/- 0.18 ng TNF/mg brain compared to 0.15 +/- 0.05 ng TNF/mg brain in the normal contralateral hemisphere. No therapeutic effect on solid RG-2 gliomas could be observed after stereotactic injection of 7.3 micrograms rHuTNF/10 microliter buffer solution into the tumor in 10 animals. Immunohistochemical studies after stereotactic injection of rHuTNF-alpha showed total disappearance of the substance after 24 hours without internalization into tumor cells. Stereotactic injection of 7.3 micrograms rHuTNF 10 microliters into normal brain resulted in marked inflammatory response around the injection track, including microvascular thrombosis. These results demonstrate that rHuTNF has neither direct nor indirect cytotoxic activity on RG-2 glioma cells. Furthermore, before clinical use of rHuTNF-alpha in malignant gliomas, the authors suggest that receptor studies be done in each patient. In receptor-positive patients undergoing treatment with rHuTNF-alpha, precautions should be taken to prevent local encephalitic reactions.

Acute effects of human recombinant tumor necrosis factor-alpha on the cerebral vasculature of the rat in both normal brain and in an experimental glioma model

The effects of intravenous (IV) infusion of human recombinant tumor necrosis factor-alpha (rTNF-alpha, Cetus) on normal brain and malignant glioma in rats were examined. Twelve Fischer 344 rats were given either a single injection of 10(6) U rTNF-alpha or injections of 5 x 10(5) U rTNF-alpha for three days. One day post-rTNF-alpha injection(s), rats were injected IV with horseradish peroxidase (HRP) to determine blood-brain barrier (BBB) breakdown and, one hour later, were perfused with an aldehyde fixative and processed for histologic examination. Treatment of normal rats with rTNF-alpha by either dosage or schedule caused no remarkable histopathologic changes in the brain and no alteration in BBB integrity. Human glioma models were produced by intracerebal inoculation of 10(4) syngeneic RT-2 glioma cells into the right parietal lobe of 30 rats. Animals received single IV injections of 10(6) U human rTNF-alpha or its excipient (TNF-E) as above on day 3, 7, or 10 post-tumor inoculation or multiple injections of 5 x 10(5) U rTNF-alpha beginning on day 7, 10, or 12 post-tumor inoculation. With a single IV injection of either rTNF-alpha or its excipient, 3-day models showed a similar pattern of HRP extravasation limited to the extracellular space of the tumor inoculation site. In 7-day models treated with a single IV injection of rTNF-alpha or TNF-E, HRP extravasated throughout the tumor, but did not exceed peritumoral margins. In 10-day models treated with a single injection of TNF-E, HRP was found only in the tumor and immediate peritumoral regions while rTNF-alpha-treated rats showed more extensive areas of BBB breakdown with HRP evident throughout the entire right hemisphere and extending via the corpus callosum into the contralateral hemisphere. Pericapillary halos were also evident around the small blood vessels within the edematous areas of the corpus callosum. Within tumors, hemorrhagic necrosis and adherence of neutrophils to vessels was observed only in animals treated with rTNF-alpha at 10 days post-tumor inoculation. Multiple IV injections of rTNF-alpha in 7 and 10-day models triggered widespread hemorrhagic necrosis, neutrophil adherence and infiltration in the tumor. There was also extravasation and diffusion of HRP from the site of glioma into the contralateral hemisphere. Twelve-day models treated with multiple rTNF-alpha injections, in addition, showed irregular luminal surfaces and gaps between adjacent endothelial cells of tumor vasculature.(ABSTRACT TRUNCATED AT 400 WORDS)

Pathological features of virus infections of the central nervous system (CNS) in the acquired immunodeficiency syndrome (AIDS)

Neurological disorders are a common cause of morbidity and mortality in the acquired immunodeficiency syndrome (AIDS). In this report we describe the neuropathological changes associated with both human immunodeficiency virus (HIV) infection and with the major opportunistic virus infections, cytomegalovirus (CMV), JC papovavirus (JCV) and herpes simplex virus (HSV) seen in AIDS. In addition "in situ" hybridization studies have been employed for the detection of virus genomic material in each case and the usefulness of this method in supporting the pathological diagnosis is demonstrated. Mechanisms whereby HIV infection results in leukoencephalopathy and the possible contributing roles of the three opportunistic virus infections are discussed.

Neurologic and psychiatric manifestations of HIV disease

Neuropsychiatric problems have assumed an increasingly prominent role in HIV-infected individuals. Disease occurs at all levels of the central and peripheral nervous systems by a variety of mechanisms. The AIDS dementia complex is the prototypical example of "direct" effects of HIV on the neuraxis, while infections such as toxoplasmosis and cryptococcal meningitis are complications of HIV-induced immunosuppression. Neurologic manifestations vary in frequency depending upon the overall stage of HIV disease; diagnostic difficulties may be encountered because of HIV's effect on cerebrospinal fluid parameters. The uncertainties of management of neurosyphilis in this setting provide and example of these problems. As is the case with other organ systems, the main goal of neurodiagnostic efforts is to find the increasing number of treatable components of neuropsychiatric dysfunction.

Tumor necrosis factor production and receptor expression by a human malignant glioma cell line, D54-MG

Human malignant gliomas possess some of the same immune-related functions as astrocytes do. For instance, they are capable of secreting various immunoregulatory molecules and expressing HLA-DR antigens on their surface. The human malignant glioma cell line, D54-MG, was used to investigate the proliferative effects of tumor necrosis factor-alpha (TNF-alpha) and the expression of specific surface receptors for TNF-alpha. Additionally, we were interested in examining whether D54-MG cells are capable of synthesizing and secreting biologically active TNF-alpha. D54-MG cells responded in a mitogenic fashion upon incubation with TNF-alpha for 48 h under serum-free conditions. 125I-labeled TNF-alpha was used in this study to investigate the expression of receptors specific for TNF-alpha on D54-MG cells. Scatchard analysis of our receptor binding data produced curvilinear plots indicating there are two distinct receptor sites for TNF-alpha. From these data, we calculated that there are approximately 3500 high affinity and 24,666 low affinity binding sites per cell. Pretreating these cells with interferon-gamma (IFN-gamma) resulted in a 2-fold increase in the number of high affinity binding sites and a moderate increase in the number of low affinity binding sites, with no appreciable change in binding affinity (Kd) of either site. D54-MG cells were unable to constitutively secrete TNF-alpha; however, upon stimulation, these cells synthesize and secrete biologically active TNF-alpha. Polyclonal antisera reactive with human macrophage-derived TNF-alpha neutralized the cytotoxicity of D54-MG-derived TNF-alpha, demonstrating that the cytotoxic activity was in fact due to TNF-alpha. Our observations indicate that TNF-alpha could act in an autocrine fashion to induce the proliferation of this malignant glioma cell line and that TNF-alpha exerts its effect by binding to specific TNF-alpha receptors whose expression was enhanced by IFN-gamma.

A receptor for tumor necrosis factor defines an unusual family of cellular and viral proteins

Tumor necrosis factor alpha and beta (TNF-alpha and TNF-beta) bind surface receptors on a variety of cell types to mediate a wide range of immunological responses, inflammatory reactions, and anti-tumor effects. A cDNA clone encoding an integral membrane protein of 461 amino acids was isolated from a human lung fibroblast library by direct expression screening with radiolabeled TNF-alpha. The encoded receptor was also able to bind TNF-beta. The predicted cysteine-rich extracellular domain has extensive sequence similarity with five proteins, including nerve growth factor receptor and a transcriptionally active open reading frame from Shope fibroma virus, and thus defines a family of receptors.