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

Intracellular application of TNF-alpha impairs cell to cell communication via gap junctions in glioma cells

Human gliomas are the most common class of brain neoplasm. In order to better characterize their response to inflammation, we evaluated the influence of tumor necrosis factor alpha (TNF-alpha) on the coupling behaviour and the membrane resting potential (MRP) of glioma cells (F98 glioma cell line) compared to primary astrocytes. In contrast to cultured primary astrocytes which exhibited a profound inhibition of gap junction mediated intercellular communication (GJIC), extracellular exposure of TNF-alpha to F98 glioma cells gained no effect on the functional coupling. Whereas, intracellular application of TNF-alpha into the glioma cells elicited similar effects as those found in primary astrocytes indicating a compromised accessibility of the TNF-alpha receptor in F98 cells. Western blotting, immunocytochemical staining and real time RT PCR analysis revealed a differential expression and distribution of TNF-alpha receptor 1 (TNFR1) in the glioma cells. Connexin 43 (Cx43) is the major astrocytic gap junction protein which when phosphorylated has been shown to reveal altered gating properties. Here we show that TNF-alpha increases the level of phosphorylated Cx43 in primary astrocytes but not in the F98 glioma cells. Our observations could account for the decreased regulatory effects of TNF-alpha on GJIC of F98 glioma 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.

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.

Growth inhibition of subcutaneously transplanted human glioma by transfection-induced tumor necrosis factor-alpha and augmentation of the effect by gamma-interferon

Using subcutaneous solid tumors produced by U251-MG human glioma cells, we studied the in vivo transfection of the cells with the tumor necrosis factor-alpha (TNF-alpha) gene delivered by means of liposomes. When the tumor had become 7 mm in diameter, liposomes with entrapped TNF-alpha gene were injected into the center of the subcutaneous tumor. We found that mRNA of transfection-induced TNF-alpha, which was expressed in the tumor tissue, was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) method and its protein was demonstrated by enzyme-linked immunoassay. Growth of the tumor was inhibited when the injection was carried out five times at every other day. The growth-inhibitory effect by transfection-induced TNF-alpha was much remarkable as compared with exogenous TNF-alpha and the effect was enhanced by the intraperitoneal injection of gamma-interferon (IFN-gamma) 12 h prior to intratumoral injection of the liposomes.

Antitumor effect of exogenous/endogenous TNF (EET) therapy with cyclophosphamide on C6 glioma in rat

We earlier reported that endogenous TNF could be induced in mice as well as in patients by successive administration of exogenous TNF as a primer and OK-432 as a trigger, and we termed this exogenous/endogenous TNF (EET) therapy. We studied the effect of EET therapy with cyclophosphamide (CY) on tumor-transplanted rats. In order to induce endogenous TNF, 5 x 10(5) U/kg of recombinant human TNF-S(AM2) (rTNF; 5.6x10(6) U/mg protein) was injected intravenously (iv) as a primer followed by injection of 25 KE/kg of OK-432 as a trigger. TNF activity induced in serum was about 500 U/ml. Only 1 U/g of TNF was detected in the brain. To evaluate the antitumor effect, C6 glioma cells (1.6 x 10(4) cell/5 microliters) was transplanted into the brain. On day 7 of the transplantation, the rats were administered iv with CY (75 mg/kg), treated with EET therapy 7 days thereafter, and survival days were checked. No clear difference in survival days was observed between the rats treated with the EET and the control group. Three rats out of 6 treated with CY survived for more than 40 days, and all the rats treated with the combination of CY and EET continued to survive. The histological examination on day 44 revealed necrotic changes at the tumor lesions in all of the surviving rats, and the animals were evaluated as completely cured. These results suggest that applied treatment based on the EET therapy will be also effective against malignant brain tumors.

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.

Immune adjuvants for chemotherapy or radiotherapy in the 9L rat brain tumor model

The therapeutic efficacy and toxicity of three biological response modifiers, Corynebacterium parvum (Cp), Chinese blister beetle extract (CBBE), recombinant human IL-1 alpha (rhIL-1 alpha), used alone or in combination with chemotherapy or radiotherapy, were investigated in the intracerebral (ic) rat 9L brain tumor model. Used alone, Cp (2 mg/rat, ip plus 70 micrograms/rat, ic), CBBE (5 microliters of an ethanol extract, ic), or IL-1 alpha (1 microgram/rat, ic or 1 microgram/rat x 3, q 3 d, ic), had no effect on animal survival compared to the untreated or saline treated controls. When combined with chemotherapy or radiotherapy, the three immunotherapeutic agents did not show any additive effects on survival compared to that observed with systemic BCNU (12 mg/kg), local ic bleomycin (0.25 unit), or local radiotherapy (16 Gy). While ic IL-1 alpha did not produce evident toxicity, there was fatal toxicity caused by ic Cp or CBBE treatment in a few animals. The combination of Cp and bleomycin produced severe neurotoxicity, resulting in the early death of animals. This study demonstrates a lack of efficacy of the nonspecific immune adjuvants IL-1 alpha, Cp or CBBE, used either alone or combined with cytotoxic chemotherapy or radiotherapy, in this rat brain tumor model.

Recombinant human tumor necrosis factor alpha constricts pial arterioles and increases blood-brain barrier permeability in newborn piglets

Tumor necrosis factor alpha (TNF alpha) plays a significant role in the pathogenesis of central nervous system infections. We investigated the effect of intracisternal injection of recombinant human TNF alpha (50-50,000 IU) on pial vasoreactivity and blood-brain barrier permeability in newborn piglets. The cytokine administration resulted in arterial vasoconstrictions, blood-brain barrier opening for Na-fluorescein (mol. wt. 376 Da) and increased Na-fluorescein uptake in brain regions examined (parietal and occipital cortex, cerebellum, pons/medulla, periventricular white matter) in a dose-dependent manner. TNF alpha may be involved in the pathophysiology of neonatal brain injuries.