The effect of tumor necrosis factor-alpha on human malignant glial cells

Chronic Neuroinflammation Induced by Lipopolysaccharide Injection into the Third Ventricle Induces Behavioral Changes

The existence of Gram-negative bacteria in the brain, regardless of underlying immune status has been demonstrated by recent studies. The colocalization of lipopolysaccharide (LPS) with Aβ_1-40/42 in amyloid plaques supports the hypothesis that brain microbes may be the cause, triggering chronic neuroinflammation, leading to Alzheimer's disease (AD). To investigate the behavioral changes induced by infectious neuroinflammation, we chose the third ventricle as the site of a single LPS injection (20 μg or 80 μg) in male Wistar rats to avoid mechanical injury to forebrain structures while inducing widespread inflammation throughout the brain. Chronic neuroinflammation induced by LPS resulted in depressive-like behaviors and the impairment of spatial learning; however, there was no evidence of the development of pathological hallmarks (e.g., the phosphorylation of tau) for 10 months following LPS injection. The acceleration of cholesterol metabolism via CYP46A1 and the retardation of cholesterol synthesis via HMGCR were observed in the hippocampus of rats treated with either low-dose or high-dose LPS. The rate-limiting enzymes of cholesterol metabolism (CYP46A1) in SH-SY5Y cells and synthesis (HMGCR) in U251 cells were altered by inflammation stimulators, including LPS, IL-1β, and TNF-α, through the TLR4/MyD88/NF-κB signaling pathway. The data suggest that chronic neuroinflammation provoked by the administration of LPS into the third ventricle may induce depressive-like symptoms and that the loss of cholesterol might be a biomarker of chronic neuroinflammation. The lack of pathological hallmarks of AD in our model indicates that Gram-negative bacteria infection might not be a single cause of AD.

PTEN enhances TNF-induced apoptosis through modulation of nuclear factor-kappaB signaling pathway in human glioma cells

The PTEN tumor suppressor gene modulates cell growth and survival known to be regulated by the activation of the transcription factor NFkappaB, suggesting PTEN might affect the NFkappaB activation pathway. We found that PTEN inhibited NFkappaB activation induced by TNF. The suppression of NFkappaB activation correlated with sequential inhibition of the tumor necrosis factor-induced expression of NFkappaB-regulated anti-apoptotic (IAP1, IAP2, Bcl-2, Bcl-xL, cFLIP, Bfl-1/A1, and survivin) gene products. Downregulation of the antiapoptotic genes by PTEN increased TNF-induced apoptosis, as indicated by caspase activation, TUNEL, annexin staining, and esterase assay. We conclude that the ectopic expression of PTEN enhances TNF-induced apoptosis and downregulates the proliferation of glioma cells through the suppression of various molecules including NFkappaB, and various mediators of cellular survival and proliferation, and that this targets might be essential for its central role in the growth and survival of glioma cancer cells.

Impairment of Both Apoptotic and Cytoprotective Signalings in Glioma Cells Resistant to the Combined Use of Cisplatin and Tumor Necrosis Factor α

PURPOSE

Tumor necrosis factor (TNF)-alpha elicits two opposing effects, the induction of apoptosis and the transcription of antiapoptotic genes. We have recently shown that cisplatin sensitizes glioma cells to TNF-induced apoptosis, but only in some cell lines. To understand the mechanism involved in the different susceptibilities, we examined both the activation of caspases and cytoprotective signaling by TNF-alpha.

EXPERIMENTAL DESIGN

Caspase activation was examined by estimating the cleavage of substrate peptides and by immunoblot to identify the cleavage of procaspases. Peptide inhibitors of caspases were used to reverse the cytotoxicity. The binding of TNF-alpha to the receptor was analyzed by flow cytometry. Nuclear factor (NF)-kappaB activation was assayed by the binding of NF-kappaB to oligonucleotides containing the consensus binding site. Interleukin (IL)-1beta, IL-6, IL-8, and manganous superoxide dismutase (MnSOD) were measured by enzyme-linked immunoassays.

RESULTS

T98G and U87MG underwent apoptosis on treatment with cisplatin and TNF-alpha, but U373MG and A172 were resistant. Caspases 2, 3, and 6-10, but not caspases 1, 4, and 5, were activated in sensitive cells, and none were activated in resistant cells. The binding of TNF-alpha to the receptor was the same in all four of the cell lines. In the sensitive cells, NF-kappaB activation and the production of IL-1beta, IL-6, IL-8, and MnSOD were significantly elevated by TNF-alpha. However, in the resistant cells, the production of IL-1beta and IL-6 were specifically impaired in response to TNF-alpha.

CONCLUSIONS

Our results indicate that both apoptotic and cytoprotective pathways are impaired in glioma cells that are resistant to treatment with cisplatin and TNF-alpha.

Adenovirus-mediated gene transduction of IkappaB or IkappaB plus Bax gene drastically enhances tumor necrosis factor (TNF)-induced apoptosis in human gliomas

Tumor necrosis factor-alpha (TNF), which was initially supposed to be a promising cancer therapeutic reagent, does not kill most types of cancer cells partly due to the activation of an anti-apoptotic gene, NF-kappaB. NF-kappaB forms an inactive complex with the inhibitor kappa B alpha (IkappaBalpha), which is rapidly phosphorylated and degraded in response to various extracellular signals. To disrupt this protective mechanism, we introduced an inhibitor kappa B alpha (IkappaBdN) gene, a deletion mutant gene lacking the nucleotides for the N-terminal 36 amino acids of IkappaBalpha, into human glioma cells (U251, T-98G, and U-373MG) via an adenoviral (Adv) vector in addition to treatment of the glioma cells with recombinant TNF. Immunohistochemical analysis revealed that NF-kappaB was translocated to nuclei by TNF treatment in U251 and T-98G cells, but not in U-373MG cells. Neither transduction of IkappaBdN nor treatment with TNF protein alone induced apoptosis in U251 and T-98G cells, whereas both cell lines underwent drastic TNF-induced apoptosis after transduction of IkappaBdN. On the other hand, U-373MG cells were refractory to TNF-induced apoptosis even when they were transduced with the IkappaBdN gene. U-373MG cells underwent drastically increased apoptosis when co-transduced with the IkappaBdN and Bax gene in the presence of TNF. Adv-mediated transfer of IkappaBdN or IkappaBdN plus Bax may be a promising therapeutic approach to treat gliomas through TNF-mediated apoptosis.

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.

Extracellular matrix degradation by metalloproteinases and central nervous system diseases

Matrix metalloproteinases (MMPs) are a gene family of neutral proteases involved in normal and pathological processes in the central nervous system (CNS). Normally released into the extracellular space, MMPs break down the extracellular matrix (ECM) to allow cell growth and to facilitate remodeling. Proteolysis becomes pathological when the normal balance between the proteases and their inhibitors, tissue inhibitors to metalloproteinases (TIMPs), is lost. Cancer cells secrete neutral proteases to facilitate spread through the ECM. MMPs increase capillary permeability, and they have been implicated in demyelination. Neurological diseases, such as brain tumors, multiple sclerosis, Guillain-Barré, ischemia, Alzheimer's disease, and infections, lead to an increase in the matrix-degrading proteases. Two classes of neutral proteases have been extensively studied, namely the MMPs and the plasminogen activators (PAs), which act in concert to attack the ECM. After proteolytic injury occurs, the process of ECM remodeling begins, which can lead to fibrosis of blood vessels and gliosis. TIMPs are increased after the acute injury and may add to the fibrotic buildup of ECM components. Thus, an imbalance in proteolytic activity either during the acute injury or in recovery may aggravate the underlying disease process. Agents that affect the proteolytic process at any of the regulating sites are potentially useful in therapy.

Mechanisms of glioma invasion: role of matrix-metalloproteinases

One of the most lethal properties of high grade gliomas is their ability to invade the surrounding normal brain tissue, as infiltrated cells often escape surgical resection and inevitably lead to tumour recurrence. The consequent poor prognosis and survival rate underscore the need to further understand and target the cellular mechanisms that underly tumour invasiveness. Proteases which degrade the surrounding stromal cells and extracellular matrix proteins have been demonstrated to be critical effectors of invasion for tumours of both central and peripheral origin. Within the nervous system, the role of metalloproteinases as well as other classes of proteases in mediating the invasive phenotype of high grade gliomas has been an intense area of research. We present in this article a review of this literature and address the possibility that these proteases and the biochemical pathways that regulate their expression, such as protein kinase C, may represent potential targets in the therapy of high grade gliomas.

Glioma invasion in vitro: regulation by matrix metalloprotease-2 and protein kinase C

A hallmark of invasive tumors is their ability to effect degradation of the surrounding extracellular matrix (ECM) by the local production of proteolytic enzymes, such as the matrix metalloproteases (MMPs). In this paper, we demonstrate that the invasion of human gliomas is mediated by a 72 kDa MMP, referred to as MMP-2, and provide further evidence that the activity of MMP-2 is regulated by protein kinase C (PKC). The invasiveness of five human glioma cell lines (A172, U87, U118, U251, U563) was assessed in an in vitro invasion assay and was found to correlate with the level of MMP-2 activity (r2 = 0.95); in contrast, the activity of this 72 kDa metalloprotease was barely detectable in non-invasive control glial cells (non-transformed human astrocytes and oligodendrocytes). Treatment with 1,10-phenanthroline, a metalloprotease inhibitor, or with a synthetic dipeptide, containing a blocking sequence (ala-phe) specific for MMPs, resulted in a > 90% reduction in glioma invasion. Furthermore, this MMP-2 activity could be inhibited by the treatment of tumor cells with calphostin C, a specific inhibitor of PKC. Glioma cell lines treated with calphostin C demonstrated a dose-dependent decrease (IC50 = 30 nM) in tumor invasiveness with a concomitant reduction in the activity of the MMP-2. Conversely, treatment of non-invasive control astrocytes with a PKC activator (phorbol ester) led to a corresponding increase in their invasiveness and metalloprotease activity. These findings support the postulate that MMP-2 activity constitutes an important effector of human glioma invasion and that the regulation of this proteolytic activity can be modulated by PKC.

Release of collagen type IV degrading activity from C6 astrocytoma cells and cell density

Type IV collagen is a major protein component of the vascular basement membrane and its degradation is crucial to the initiation of tumor-associated angiogenesis. The authors have investigated the influence of cell density on the release of collagen type IV degrading activity by C6 astrocytoma cells in monolayer culture. The release of collagen type IV degrading activity was assessed biochemically, immunocytochemically, and by Western blot analysis. The results demonstrate that increasing plating density and increasing cell density are associated with decreased collagen type IV degrading activity released per tumor cell. These findings indicate the existence of regulatory mechanisms dependent on cell-cell communication, which modulate release of collagen type IV degrading activity. The extrapolation of these results to the in vivo tumor microenvironment would suggest that individual and/or small groups of invading tumor cells, distant from the main tumor mass, would release substantial collagen type IV degrading activity, which may be crucial to their continued invasion and to angiogenesis.

Gene transfer of human TNF alpha into glioblastoma cells permits modulation of mdr1 expression and potentiation of chemosensitivity

Despite substantial advances in the surgery, radiotherapy and chemotherapy of gliomas, the prognosis of patients with glioblastomas has still not improved. Disappointing results in chemotherapy of glioblastomas resulting from multi-drug resistance (MDR) prompted us to investigate the influence of cytokine gene transfer in glioblastoma cells on the expression of P-glycoprotein and on chemosensitivity of transduced cells. Several investigations have shown that malignant gliomas express P-glycoprotein at high levels. The P-glycoprotein is a product of the multi-drug resistance gene (mdr1) and functions as an energy-dependent efflux pump which decreases drug accumulation and cytotoxicity. Since tumour necrosis factor alpha (TNF alpha) is a powerful anti-cancer agent used in clinical trials and gene therapy protocols, this cytokine gene was chosen for the present investigations. Transduction of the human TNF alpha (hTNF) gene carrying retroviral vector pN2tk-hTNF into U373MG human glioblastoma cells resulted in expression and secretion of biologically active hTNF. Release of transduced hTNF reduces P-glycoprotein expression and is associated with enhanced rhodamine-123 uptake and potentiation of cytotoxicity of the MDR-relevant drugs vincristine and doxorubicin. Furthermore, the transfected cell clones showed a reduced growth rate compared to the parental cells.

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.

Response of multicellular tumor spheroids to liposomes containing TNF-alpha

This publication describes a new model to investigate the influence of tumor necrosis factor-alpha (TNF-alpha) on a three-dimensional glial cell aggregate under defined, standardized, reproducible conditions using the glioma cell line A 172. The cells are initially grown as normal monolayer culture until they reach a cell density of up to 1 x 10(6). Subsequently they are grown as spheroids by the liquid overlay technique. Spheroids grown in this way were divided into ten groups of more than 50 cell aggregates. Three groups were coincubated with free TNF-alpha in increasing dosages (100 ng/ml, 200 ng/ml and 1000 ng/ml); three groups were incubated with empty liposomes (0.2 mg/ml, 0.4 mg/ml and 2 mg/ml); three groups received liposomes which had been loaded with TNF-alpha, and one group, which received no treatment, served as control. The diameter of the spheroids ranged from 80 microns to 350 microns. There was no significant difference in growth between the 3 groups treated with 'free' TNF-alpha. Comparing spheroids treated with TNF-alpha with those which had been coincubated with empty liposomes, there was a significant difference (p < 0.001) in growth, which correlated with the amount of liposomes. Similarly, free TNF-alpha had a significantly (P < 0.001) stronger growth-inhibiting effect as compared to liposomes loaded with TNF-alpha. Comparing the groups treated with liposomes only to those treated with liposomes loaded with TNF-alpha, the latter exhibited a more marked (although not significantly) growth-inhibiting effect. The preliminary conclusion is that the major growth-inhibiting effect seems to be mediated by the liposomes.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo effects of recombinant human lymphotoxin on human medulloblastoma xenograft: enhancement of antitumor activity of etoposide

The authors investigated the antitumor activities of rHuLT alone and in combination with etoposide on human meduloblastoma xenografts growing subcutaneously in nude mice. Intravenous administration of rHuLT (1.0 x 10(5) U/kg, 5.0 x 10(5)U/kg, 2.5 x 10(6)U/kg, three times a week for three weeks) suppressed medulloblastoma growth depending on the dose. However, the highest dosage caused serious side effects. Combining rHuLT (intravenously, 5.0 x 10(5)U/kg, three times a week for three weeks) with etoposide (intraperitoneally, 20mg/kg, once a week for three weeks) increased the antitumor activity without causing serious toxicity. Microscopically, tumor specimen showed thrombosed tumor vessels and massive necrosis 3 weeks after rHuLT treatment. Ultrastructural examination revealed that 120 minutes after the administration of rHuLT alone, disruption of interendothelial junctions was evident, and that the endothelial cells were destroyed at 240 minutes. Concentration of etoposide in tumor tissue peaked 30 minutes after intraperitoneal administration, and then decreased with time. When etoposide was administered in combination with rHuLT, the concentration of etoposide in tumor tissue after 60 to 240 minutes was significantly higher than when etoposide was given alone, and the area under the concentration versus time curve was also greater for the tumors of mice with combination treatment. The findings suggest that the proper combination of rHuLT and etoposide may have synergistic antitumor activities. Histological changes suggest that increased concentrations of etoposide within the tumor after combination therapy may occur due to increased vascular permeability and/or decreased etoposide clearance which is the result of blood statis in the tumor vasculature.

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.

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.

Serum proteolytic activity during the growth of C6 astrocytoma

Tumor growth is dependent on the ability of neoplastic cells to induce angiogenesis. Blood-vessel remodeling requires the reconstruction of the nonfibrous proteins and type IV collagen components of the basement membrane. This study has assessed the influence of the growth of C6 astrocytoma cells in the rat spheroid implantation model on serum general protease and type IV collagenase activity. The results demonstrate that general protease activity increased in serum, reaching maximum values on Day 6 and Day 13 following spheroid implantation, and that type IV collagenase activity increased in serum, obtaining maximum values on Day 8 and Day 15. The measurement of serum proteolytic activity may be of value in the detection of recurrent tumors.