TNF Resistance Research Articles

Development of resistance to tumour necrosis factor (TNFα) in KYM-1 cells involves both TNF receptors

In this study, we investigated the type of TNF receptor expressed by the human rhabdomyosarcoma cell line KYM-1 and related TNF-sensitive sublines and showed that the majority (> 90%) of TNF receptors were type II (p75) receptors with only a relatively small number (< 10%) of type I (p55) receptors. Selection with TNF alpha led to the isolation of KYM-1 related TNF-resistant cell lines of which three cloned lines showed a near to total loss of type II TNF receptors. To investigate further the role of each type of TNF receptor in the regulation of TNF-mediated cytotoxicity and the development of TNF resistance, we used receptor-specific antibodies and antisera, able to compete with ligand binding to the respective receptor molecules, but representing efficient agonists via crosslinking of receptors. We found that in KYM-1 and related TNF-sensitive sublines both type I and type II TNF receptors can be functional on their own, as selective cross-linking of each receptor subset lead to cytolysis. However, investigation of three TNF-resistant KYM-1 related cell lines by selective receptor stimulation via cross-linking indicated different mechanisms underlied the development of TNF-resistant for each receptor type. Our data indicate that resistance to TNF-mediated cytotoxicity in KYM-1 related cell lines can be developed both by a selective loss of type II receptor expression and the selective loss of type I receptor function without reduction in type I receptor numbers.

Role of protein phosphorylation in TNF-induced apoptosis: phosphatase inhibitors synergize with TNF to activate DNA fragmentation in normal as well as TNF-resistant U937 variants.

This study examined the role of protein phosphorylation in TNF induction of apoptosis in several tumor cell lines by testing the effects of agents that either stimulate or inhibit protein phosphorylation. The serine-threonine phosphatase inhibitors, okadaic acid (OKA) and calyculin A (CLA), synergistically augmented TNF-induced apoptosis in several TNF-sensitive tumor cell lines including the U937 histiocytic lymphoma, the BT-20 mammary carcinoma, and the LNCap prostatic tumor cell line. Furthermore, the phosphatase inhibitors completely reversed the TNF resistance of a variant (U9-TR) derived from U937. CLA also inhibited phosphatase activity in cell-free extracts from both U937 and U9-TR at the same concentrations (0.4-2.0 nM) that it synergized with TNF. In contrast, TNF treatment of U937 cells did not result in inhibition of phosphatase activity mediated by protein phosphatase 1 (PP1) and PP2A in cell extracts. Since the phosphatase inhibitors are known to increase the overall levels of protein phosphorylation in cells, this suggested that TNF may act by stimulating protein kinase (PK) activity. This hypothesis was supported by the results of testing a panel of relatively specific protein kinase inhibitors. TNF activation of DNA fragmentation was blocked by a potent inhibitor of myosin light chain kinase (MLCK) but was unaffected by inhibitors of cAMP or cGMP-dependent PKs. We postulate that a defect in the activation of MLCK or possibly some other as yet unknown PK may be responsible for the TNF resistance of U9-TR. Furthermore, this resistance may be circumvented by promoting protein phosphorylation with the serine-threonine-dependent phosphatase inhibitors.

Overexpression of major heat shock protein hsp70 inhibits tumor necrosis factor-induced activation of phospholipase A2.

We have recently shown that major heat shock protein (hsp70) protects WEHI-S tumor cells from the cytotoxicity mediated by TNF. In the present study, the mechanism of hsp70-associated TNF resistance was investigated. Overexpression of human hsp70 or inhibition of endogenous hsp70 synthesis by expression of antisense hsp70 RNA did not change the ability of WEHI-S tumor cells to bind TNF or internalize and degrade the receptor-bound TNF. Moreover, TNF-induced activation of NF-kappa B-like transcription factors was unaffected by altered levels of hsp70 as tested by electrophoretic mobility shift assay. Thus, it is unlikely that the resistance is due to changes in TNF receptors or in their ability to transduce signals leading to the regulation of genes, whose expression is regulated by NF-kappa B-like transcription factors. The idea that hsp70-associated TNF resistance is independent of regulation of TNF-induced gene expression was further supported by the results showing that hsp70 protected WEHI-S cells from TNF-mediated killing also in the presence of inhibitors of either translation or transcription. Interestingly, TNF-induced activation of arachidonic acid metabolism correlated directly with their sensitivity to TNF and inversely with the amount of hsp70 in the cells. Furthermore, TNF-induced activation of arachidonic acid metabolism was inhibited in WEHI-S cells and two TNF-sensitive human cell lines by induction of the synthesis of endogenous heat shock proteins by heat shock. Even stronger inhibition of arachidonic acid metabolism was seen in WEHI cells rendered TNF-resistant by culturing them in the presence of increasing concentrations of TNF. These cells also had reduced numbers of type 1 TNF receptors. Overexpression of a low molecular weight heat shock protein hsp27 in WEHI-S cells had no effect on any of the parameters studied. These results show that both hsp70-mediated and TNF-induced TNF resistance are associated with a reduced activation of phospholipase A2 suggesting that phospholipase A2 plays an essential role in TNF-mediated cytotoxicity and that hsp70 interferes with the signal transduction pathway leading to its activation.

Increased sensitivity to TNF-mediated cytotoxicity of BL6 melanoma cells after H-2Kb gene transfection.

Transfection of the H-2Kb and neor genes into BL6-8 (H-2Kb-, H-2Db+) melanoma clone resulted in various phenotypic changes with appearance of soybean agglutinin (SBA) and Grifonia Simplicifolia 1-B4 (GS1B4) lectin binding carbohydrates and loss of melanoma-associated antigen (MAA). In parallel H-2Kb gene-transfected melanoma cells showed increased sensitivity to TNF lysis. To further delineate the ability of H-2Kb gene to induce the phenotypic changes and TNF sensitivity, BL6-8 melanoma clone was transfected with the H-2Kb gene alone without cotransfection with neor gene and transfected cells were selected for adherence to SBA lectin-conjugated agarose beads. Analysis of isolated clones revealed that 38 of 47 tested clones have been found to be expressing the H-2Kb Ag, SBA, and GS1B4 lectin binding carbohydrates but lost MAA, e.g., H-2Kb+, lectin+, MAA-, and in parallel these cells became sensitive to TNF lysis. Although all clones with high expression of H-2Kb Ag were sensitive to TNF lysis, it seems unlikely that H-2K molecules are directly required for or involved in TNF-induced melanoma cell lysis. This conclusion is based on findings that four H-2Kb-transfected clones selected on SBA-agarose beads did not expressed H-2Kb Ag but manifested increase in SBA and GS1B4 lectin binding and loss of MAA and also became sensitive to TNF lysis. It seems that increase in TNF sensitivity is a part of the broad phenotypic changes induced by the H-2K gene that remained stable even in the clones in which the transfected H-2Kb gene was lost or down-regulated. We believe that the effects of the H-2Kb gene on melanoma cell phenotype and TNF sensitivity are indirect and are probably mediated via its inhibition of the melanoma-associated ecotropic retrovirus production and activation of some repressed cellular genes. Study of the mechanisms responsible for TNF sensitivity of BL6 melanoma cells revealed that the H-2Kb gene transfection resulted in an increase in p55 TNF receptor expression. TNF-induced activation of phospholipase A2 and release of arachidonic acid metabolites was observed only in the H-2Kb transfected, but not in BL6-8 melanoma cells transfected with neor or class II H-21Ak genes. TNF resistance of BL6 melanoma cells appeared to be due to a block in transduction of the lytic signal that was reversed after transfection with H-2Kb gene.

Protein kinase C is implicated in the modulation of TNF resistance in U937 histiocytic cells and A U937 monocytic hybridoma A10: [formula omitted] Division of Immunobiology, NIBSC, Blanche Lane, South Mimms, Potters Bar, Herts. EN6 3QG

Protein kinase C is implicated in the modulation of TNF resistance in U937 histiocytic cells and A U937 monocytic hybridoma A10: [formula omitted] Division of Immunobiology, NIBSC, Blanche Lane, South Mimms, Potters Bar, Herts. EN6 3QG

Effect of tumor necrosis factor-alpha on the proliferation of leukemic cells from children with B-cell precursor-acute lymphoblastic leukemia (BCP-ALL): studies of primary leukemic cells and BCP-ALL cell lines

The effect of recombinant tumor necrosis factor-alpha (rTNF-alpha) on the primary leukemic blasts and leukemic cell lines derived from children with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) was studied. The proliferation of leukemic cells from the bone marrow of 11 of 13 patients (seven at diagnosis, four in relapse) and from the 697 (BCP-ALL) cell line was significantly inhibited by rTNF-alpha at the lowest dose tested (0.1 ng/mL), as measured by 3H-TdR uptake. The degree of inhibition was variable, ranging from 17% to 78%. Furthermore, a dose-dependent inhibitory effect was observed, with approximately 70% mean inhibition of DNA synthesis detected when cells from 12 of 13 patients were incubated with 100 ng/mL of rTNF-alpha for 3 days. In contrast, rTNF-alpha did not inhibit another BCP-ALL cell line (EU-1/ALL) established recently in our laboratory. Studies indicated that the TNF-alpha gene was expressed by the primary leukemic blasts of one TNF-resistant case in his third relapse and by EU-1 cells. Also, TNF-alpha protein was detected by Western blot analysis and enzyme-linked immunoabsorbent assay in the supernatant of EU-1 cells; this is the first report of TNF production by a BCP-ALL cell lines. The production of TNF-alpha mRNA and protein was not detected in the 697 cell line and in the primary leukemic blasts from six patients (four at diagnosis, two in relapse) whose leukemic cells were inhibited by TNF. The partially purified TNF-alpha obtained from the EU-1 cell line also suppressed the proliferation of TNF-sensitive primary leukemic cells, and this inhibitory activity was abolished by an anti- TNF-alpha specific antibody. Our results demonstrate that TNF-alpha is an inhibitor of in vitro proliferation of BCP-ALL cells from most patients. The TNF-resistant leukemic cells from a few patients and the EU-1 cell line express TNF mRNA, suggesting that the induction of TNF gene expression is associated with the development of TNF resistance.

Effect of Tumor Necrosis Factor-α on the Proliferation of Leukemic Cells From Children With B-Cell Precursor-Acute Lymphoblastic Leukemia (BCP-ALL): Studies of Primary Leukemic Cells and BCP-ALL Cell Lines

The effect of recombinant tumor necrosis factor-alpha (rTNF-alpha) on the primary leukemic blasts and leukemic cell lines derived from children with B-cell precursor acute lymphoblastic leukemia (BCP-ALL) was studied. The proliferation of leukemic cells from the bone marrow of 11 of 13 patients (seven at diagnosis, four in relapse) and from the 697 (BCP-ALL) cell line was significantly inhibited by rTNF-alpha at the lowest dose tested (0.1 ng/mL), as measured by 3H-TdR uptake. The degree of inhibition was variable, ranging from 17% to 78%. Furthermore, a dose-dependent inhibitory effect was observed, with approximately 70% mean inhibition of DNA synthesis detected when cells from 12 of 13 patients were incubated with 100 ng/mL of rTNF-alpha for 3 days. In contrast, rTNF-alpha did not inhibit another BCP-ALL cell line (EU-1/ALL) established recently in our laboratory. Studies indicated that the TNF-alpha gene was expressed by the primary leukemic blasts of one TNF-resistant case in his third relapse and by EU-1 cells. Also, TNF-alpha protein was detected by Western blot analysis and enzyme-linked immunoabsorbent assay in the supernatant of EU-1 cells; this is the first report of TNF production by a BCP-ALL cell lines. The production of TNF-alpha mRNA and protein was not detected in the 697 cell line and in the primary leukemic blasts from six patients (four at diagnosis, two in relapse) whose leukemic cells were inhibited by TNF. The partially purified TNF-alpha obtained from the EU-1 cell line also suppressed the proliferation of TNF-sensitive primary leukemic cells, and this inhibitory activity was abolished by an anti-TNF-alpha specific antibody. Our results demonstrate that TNF-alpha is an inhibitor of in vitro proliferation of BCP-ALL cells from most patients. The TNF-resistant leukemic cells from a few patients and the EU-1 cell line express TNF mRNA, suggesting that the induction of TNF gene expression is associated with the development of TNF resistance.

Inhibitors of ADP-ribose polymerase decrease the resistance of HER2/neu-expressing cancer cells to the cytotoxic effects of tumor necrosis factor.

Four human ovarian and breast tumor lines expressing the HER2/neu oncogene were resistant to the cytotoxic and DNA-degradative activity of TNF. The resistance was not associated with altered TNF receptor function because Scatchard analysis of 125I-rTNF binding to HER2/neu-expressing target cells revealed receptors with normal binding parameters. Furthermore, the TNF receptors on the resistant lines were capable of signal transduction as evidence by the induction of ADP-ribose polymerase activity and MHC expression. TNF resistance was not reversed by coincubation with drugs that interrupted the glutathione redox cycle. In addition, although coincubation of HER2/neu-expressing targets with cycloheximide resulted in significant TNF-induced lysis, when compared to HER2/neu-nonexpressing targets similarly treated with cycloheximide, a significant relative resistance was still present. To investigate the role of ADP-ribosylation in the resistance of these targets, we used nontoxic concentrations of two inhibitors of ADP-ribose polymerase, 3-aminobenzamide, and nicotinamide. Both inhibitors completely reversed the resistance of HER2/neu-expressing targets to TNF-mediated cytotoxicity and DNA injury in a concentration-dependent fashion. These inhibitors of ADP-ribose polymerase did not act by down-regulating expression of HER2/neu oncogenes. In contrast, aminobenzamide and nicotinamide significantly diminished TNF-induced cytotoxicity of L929 targets. These data suggest that the activity of ADP-ribose polymerase may play a pivotal role in determining the fate of the target cell during exposure to TNF.

TNF resistance correlates to free radical resistance

TNF resistance correlates to free radical resistance

Nonhematopoietic cells selected for resistance to tumor necrosis factor produce tumor necrosis factor.

TNF-resistant lines of L cells can be derived from TNF-sensitive populations by repeated exposure to TNF, and these resistant L cells, in contrast to sensitive L cells and other types of cells, lack demonstrable cell surface receptors for TNF. We have now found that TNF-resistant L cells produce a factor that is cytotoxic for L cells and has the following distinguishing characteristics of mouse TNF: it is a protein of 43 kD, composed of 16 kD subunits, that competes with TNF for receptor binding, induces hemorrhagic necrosis of the TNF-sensitive mouse sarcoma Meth A, has synergistic cytotoxic action with interferon, and its activity is neutralized by antibody to TNF. The two conclusions of this study are that cells selected for TNF resistance spontaneously produce a molecule resembling macrophage TNF, and that cells of nonhematopoietic origin are capable of producing TNF.