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K Pfizenmaier

Publications and source records attributed to K Pfizenmaier.

At least 73 records · Page 4Linked to original sources
PubMed1993

TR60 and TR80 tumor necrosis factor (TNF)-receptors can independently mediate cytolysis.

The human rhabdomyosarcoma cell line KYM-1 coexpresses high numbers of both tumor necrosis factor-alpha (TNF) receptors, TR60 and TR80, and is highly sensitive to TNF-induced cytotoxicity. We show here that each receptor type can mediate cytotoxicity on its own on selective stimulation. This was achieved using receptor specific antibodies, able to compete with ligand binding to the respective receptor molecules. Thus, the TR60-specific monoclonal antibody H398 was strongly agonistic, i.e., cytotoxic, in the presence of a secondary cross-linking immunoglobulin. Selective stimulation of TR80 by antibody-mediated receptor crosslinking also induced strong cytotoxicity in KYM-1 cells. Interestingly, when both receptor subsets were stimulated in parallel by limited receptor cross-linking, additive cytolytic effects were observed. In each case the respective Fab fragments showed no agonistic activity. When the natural ligand TNF was used to induce cytolysis, blocking studies with receptor specific Fab fragments indicated that the main cytotoxic effect of TNF is mediated via TR60, although these receptors represent only about 8% of the total TNF receptor number.

Antibodies, Monoclonal↗
PubMed1991

Short-term treatment with gamma interferon induces stable reversion of ras-transformed mouse fibroblasts.

Persistent revertants have been generated from NIH 3T3 cells transformed by an activated human Ha-ras gene after short-term gamma interferon treatment in the presence of the cardiac aminoglycoside ouabain. Normal fibroblastlike morphology and anchorage dependence are restored in revertants. Tumorigenicity in nude mice is abolished. The revertants continue to express high steady-state levels of the ras oncogene. Partial retransformation of reverted cells is induced after 5-azacytidine treatment or after infection with retrovirus vectors carrying the v-abl, v-fes, v-myc, or v-src oncogene. The revertants resist the transforming activities of the v-Ha-ras and v-mos oncogenes.

Animals↗
PubMed1990

Regulation of IFN-gamma-receptor expression in human monocytes by granulocyte-macrophage colony-stimulating factor.

The regulation of human IFN-gamma receptor (IFN-gamma-R) expression by granulocyte-macrophage CSF (GM-CSF) was investigated. On monocytic cell lines (U937, HL60) and peripheral blood monocytes, IFN-gamma-binding capacity was down-regulated upon incubation with GM-CSF. Scatchard plot analyses revealed that down-regulation was caused by a decrease in IFN-gamma-R number rather than by a change in affinity. GM-CSF treatment did not reduce IFN-gamma-R-specific mRNA levels, but reduced the half-life of membrane-expressed IFN-gamma-R, indicating a post-translational control of IFN-gamma-R by GM-CSF. Because both IFN-gamma and GM-CSF are crucially involved in activation of monocytic function, the data presented suggest that down-regulation of IFN-gamma-R by GM-CSF may represent a potential negative feedback control of monocyte activation. Further studies of IFN-gamma binding characteristics and isolation of IFN-gamma-R by immunoprecipitation revealed that IFN-gamma binding to human peripheral blood monocytes is mediated by a receptor protein structurally and functionally identical to that previously characterized in several established cell lines of other tissue origin.

Blotting, Northern↗
PubMed1990

Identification of a 60-kD tumor necrosis factor (TNF) receptor as the major signal transducing component in TNF responses.

We describe here a monoclonal antibody (H398) that immunoprecipitates a human 60-kD tumor necrosis factor (TNF) membrane receptor (p60) and competes with TNF binding to p60 but not to p85 TNF receptors. Despite partial inhibition of TNF binding capacity of cells coexpressing both TNF receptor molecules, H398 uniformly and completely inhibits very distinct TNF responses on a variety of cell lines. These data suggest a limited structural heterogeneity in those components actually contributing to TNF responsiveness and identify p60 as a common receptor molecule essential for TNF signal transduction. As H398 is a highly effective TNF antagonist in vitro, it might be useful as a therapeutic agent in the treatment of TNF-mediated acute toxicity.

Animals↗
PubMed1990

Tumor necrosis factor signal transduction. Cell-type-specific activation and translocation of protein kinase C.

We have investigated the changes in protein kinase C (PKC) activity after treatment of several cell lines with TNF. Binding studies with [3H]phorbol dibutyrate (PBt2) on whole cells revealed rapid and transient activation of PKC in Jurkat, K562, and U937 cells with a maximum of phorbol ester binding at 6 min after TNF treatment. As shown by Scatchard analysis, the TNF-induced increase of [3H]PBt2 binding reflected increments of phorbol ester binding site numbers rather than greater binding affinities. Upon subfractionation of TNF-treated U937 cells a transient increase of PBt2 binding in the membrane fraction was accompanied by a long term loss of PBt2-binding in the cytosol, indicating a TNF-induced translocation of PKC from the cytosol to the cell membrane. With histone III-S as a substrate, the determination of specific PKC activity revealed similar kinetics of PKC translocation in U937 cells. TNF also induced PKC translocation in K562 and Jurkat cells. However, although TNF caused long term down-regulation of cytosolic PKC activity in U937 cells, the cytosolic PKC activity only transiently decreased in both Jurkat and K562 cells and then recovered to near basal levels. In the human nonmalignant fibroblast cell line CCD18, PKC was not activated by TNF. Our data suggest that PKC activation may play a major role in TNF signal transduction in some, but not all target cells.

Cell Compartmentation↗
PubMed1990

Glycosylation of the human interferon-gamma receptor. N-linked carbohydrates contribute to structural heterogeneity and are required for ligand binding.

The contribution of N-linked carbohydrates to human interferon-gamma receptor (hIFN-gamma-R) structure and function was investigated in four tumor cell lines of various tissue origin. Western and ligand blotting of native and deglycosylated, affinity-purified hIFN-gamma-R of the monocytic cell line U937 and the lymphoid cell line Raji revealed that the different sizes of hIFN-gamma-R from U937 (103 kDa) and Raji (90 kDa) cells are reduced upon either metabolic inhibition or enzymatic deglycosylation of N-linked carbohydrates to a common size of the receptor molecule with an apparent molecular mass of 73 kDa for both cell lines, indicating that heterogeneity in hIFN-gamma-R size is largely due to differential glycosylation. In all cell lines investigated, inhibition of N-linked glycosylation or modulation of carbohydrate processing did not prevent receptor transport to the cell membrane, but blocked hIFN-gamma binding capacity of membrane-expressed receptor molecules, as revealed by specific binding of hIFN-gamma-R-specific monoclonal antibody and specific binding of 125I-labeled hIFN-gamma. These data suggest that a lack of complex-type N-linked carbohydrates is associated with a complete loss of receptor function, i.e. high affinity binding capacity. Recovery of hIFN-gamma binding of deglycosylated receptors was achieved upon affinity purification and adsorption to nitrocellulose membranes, indicating that the carbohydrate side chains themselves do not directly contribute to the ligand binding epitope but seem to be essential for appropriate conformation of the receptor protein in the cell membrane.

Alkaloids↗
PubMed1990

Human chromosome 21 is necessary and sufficient to confer human IFN gamma responsiveness to somatic cell hybrids expressing the cloned human IFN gamma receptor gene.

The human interferon (IFN) gamma receptor cDNA has been stably expressed in human/mouse somatic cell hybrids, which differ in their content of human chromosome 21. Despite high affinity IFN gamma binding-capacity of all receptor transfectants, biological responsiveness to IFN gamma, as determined by enhancement of mouse-MHC class I gene expression, required the presence of chromosome 21. These data suggest complementation of at least two functionally distinct components in order to create a biologically active IFN gamma receptor.

Animals↗
PubMed1990

Molecular cloning and expression of human and rat tumor necrosis factor receptor chain (p60) and its soluble derivative, tumor necrosis factor-binding protein.

Tumor necrosis factor-alpha (TNF-alpha), a protein released by activated macrophages, is involved in a wide variety of human diseases including septic shock, cachexia, and chronic inflammation. TNF binding protein (TNF-BP), a glycoprotein with high affinity to TNF-alpha isolated from urine, acts as an inhibitor of TNF-alpha by competing with the cell-surface TNF receptor. We report here the partial amino acid sequencing of human TNF-BP as well as the isolation, sequence, and expression of cDNA clones encoding a human and rat TNF receptor. The calculated Mr of the mature human and rat TNF receptor chains is 47,526 and 48,072, respectively. The extracellular ligand binding domain represents the soluble TNF-BP which is released by proteolytic cleavage. TNF-BP contains 24 cysteine residues and three potential N-glycosylation sites and shows sequence homology to the extracellular portions of TNF-R p80 chain and nerve growth factor receptor. Transfection of the human TNF receptor cDNA into mammalian cells resulted in increased binding capacity for TNF-alpha and increased reactivity with a monoclonal antibody directed against the human TNF receptor chain p60. When a stop codon was introduced into the cDNA at the site corresponding to the carboxyl terminus of TNF-BP, transfected cells secreted a protein that reacted with antibodies raised against natural TNF-BP.

Amino Acid Sequence↗
PubMed1989

Antagonistic control of tumor necrosis factor receptors by protein kinases A and C. Enhancement of TNF receptor synthesis by protein kinase A and transmodulation of receptors by protein kinase C.

We have investigated control mechanisms of TNF receptor expression (TNF-R) in various human tumor cells and normal peripheral blood monocytes. Activators of protein kinase A (PKA) signal transduction pathways were found to enhance TNF-R expression up to sevenfold, whereas in the same cells, IFN-alpha and -gamma receptors remained unaffected. Inhibitors of protein kinases downregulate both constitutive and cAMP-enhanced TNF-R expression. Binding studies revealed an increase in TNF-R numbers without a change in receptor affinity. Both, direct activators of PKA and inhibitors of phosphodiesterase, raising intracellular levels of cAMP, were found to be effective. As activation of PKA does not slow down the degradation rate of TNF-Rs, but rather enhances protein synthesis-dependent reexpression of TNF-Rs after transient PKC-mediated transmodulation and after tryptic digestion of TNF-Rs, it is concluded that PKA stimulates TNF-R synthesis. Maximum TNF-Rs enhancement is reached after 24 h of stimulation and is reversible, suggesting that receptor upregulation is not linked to irreversible steps of cellular differentiation. PKA-mediated enhancement of TNF-R expression was predominantly observed in normal peripheral blood monocytes and tumor cell lines of myeloid origin. As in these typical TNF producer cells, the production of TNF is also controlled by PKA and PKC, a regulatory circuit is proposed, by which these two independent signal pathways antagonistically regulate TNF production and, at the receptor level, TNF sensitivity.

Bucladesine↗
PubMed1989

Tumor necrosis factor signal transduction. Tissue-specific serine phosphorylation of a 26-kDa cytosolic protein.

Binding of tumor necrosis factor-alpha (TNF-alpha) to its receptor on U937 cells results in rapid and TNF dose-dependent phosphorylation of a cytosolic protein with an apparent molecular mass of 26,000 kDa (p26) and an isoelectric point of 5.6. Half-maximal phosphorylation of p26 was achieved at concentrations of 1.8 ng/ml and was detectable within 20 s of TNF-alpha treatment. p26 is phosphorylated exclusively at serine residues. p26 phosphorylation occurs at 37 degrees C as well as at 14 degrees C, indicating that internalization of the TNF receptor is not required for serine kinase activation. Dephosphorylation of p26 starts 10 min after TNF-induced phosphorylation, suggesting a possible regulatory function of this cytosolic protein within the post-TNF receptor signaling system. p26 is also phosphorylated upon treatment with lymphotoxin. In contrast, both interferon-gamma and lipopolysaccharide fail to induce p26 phosphorylation. Whereas phosphorylated p26 was detected in the TNF-sensitive breast cancer cell line CRL1500, other TNF-responsive tumor cell lines investigated lacked enhanced phosphorylation of p26 in response to TNF, indicating that the 26-kDa phosphoprotein (pp26) may be a cell type-specific second messenger molecule involved in TNF signal transduction in some, but not all, target cells. p26 is also phosphorylated in a subclone of U937 (U937.C27) that responds to TNF-alpha with differentiation, yet is resistant to TNF-alpha-mediated growth inhibition. In contrast, p26 is not phosphorylated in another U937 derivative (U937.G3) that is resistant to both TNF-alpha-induced growth arrest and differentiation, suggesting that pp26 may play a role in the TNF signaling pathway linked to differentiation processes rather than to growth control.

Breast Neoplasms↗
PubMed1989

Sequential therapy with recombinant interferons gamma and alpha in patients with unfavorable prognosis of chronic myelocytic leukemia: clinical responsiveness to recombinant IFN-alpha correlates with the degree of receptor down-regulation.

Natural and recombinant interferons (IFNs) have already demonstrated therapeutic efficacy, including cytogenetic remissions, in patients with chronic myelocytic leukemia (CML). We investigated at the level of ligand-receptor interaction the question whether heterogeneity of receptor number or affinity might contribute to primary or secondary treatment failures in CML. We therefore analyzed IFN-gamma and IFN-alpha receptor expression and regulation during treatment with recombinant IFN-gamma and IFN-alpha in 15 patients with advanced CML. We found no difference in number or affinity of constitutively expressed IFN-gamma receptors (mean 1,100) and, on average, a 30% reduction of IFN-alpha receptors (mean 750) on peripheral blood mononuclear cells (PBMNC) of patients with chronic or accelerated CML as compared to mature granulocytes and/or bone marrow cells of healthy controls, which express on average 1,050 and 1,100 IFN-gamma and IFN-alpha receptors, respectively. While IFN-gamma receptor expression on PBMNC is not influenced upon treatment with rIFN-gamma, there is a substantial downregulation of IFN-alpha receptors in the course of rIFN-alpha therapy. Our data also show a differential pattern of receptor downregulation between patients achieving complete hematologic remission (CHR) (4 out of 12) compared with patients with partial hematologic remission (PHR) and non-responders. We conclude that differences in IFN receptor number cannot explain primary or secondary treatment failures. However, the differential ligand induced downregulation of IFN-alpha receptors in patients achieving CHR compared to those with PHR or non-responders suggest a prospective value of IFN-alpha receptor determination.

Adult↗
PubMed1989

Intralesional application of recombinant human tumor necrosis factor alpha induces local tumor regression in patients with advanced malignancies.

Fourteen patients with different advanced solid tumors were treated by intratumoral application of recombinant human tumor necrosis factor alpha. In five patients, local tumor regression occurred. However, the duration of response was short, implying a rapid development of resistance to rTNF-alpha application. The main clinical side-effects, including chills, fever, anorexia and fatigue, were similar to systemic rTNF-alpha treatment. Cardiovascular, pulmonary or metabolic toxicities were not observed. This study demonstrates that a high concentration of rTNF-alpha at the tumor site has the potential to induce local tumor regressions and, therefore, seems more reasonable for further clinical investigations, especially in combination with other cytokines.

Adolescent↗
PubMed1989

Regulation of tumor necrosis factor gene expression in colorectal adenocarcinoma: in vivo analysis by in situ hybridization.

Tumor necrosis factor (TNF) produced by macrophages is thought to contribute to the host defense against development of cancer. However, since tumor cells themselves are able to produce TNF, it is conceivable that TNF may also play an adverse pathological role in carcinogenesis. To better understand the functional significance of TNF in neoplastic disease, we have determined the cellular source of TNF activity produced in 10 patients with colorectal cancer. Northern blot analysis of RNAs extracted from fresh biopsy specimens revealed detectable TNF mRNA levels in all instances. By using in situ hybridization of frozen sections, scattered cells expressing TNF mRNA could be discerned. Based on morphological criteria, these TNF-positive cells most likely belong to the macrophage lineage. Macrophages in normal tissue surrounding the tumor did not express TNF mRNA, suggesting that macrophage activation occurs locally at the site of neoplastic transformation. Immunohistochemistry using anti-TNF monoclonal antibodies revealed that less than 1% of tumor-infiltrating macrophages synthesize TNF protein. Thus we present evidence that in colorectal cancer only a small proportion of tumor-infiltrating macrophages produces TNF, indicating that the microenvironment of the tumor provides adequate, yet suboptimal, conditions for macrophage activation.

Adenocarcinoma↗
PubMed1989

[Systemic versus local therapy with recombinant tumor necrosis factor-alpha (r-TNF-alpha) in patients with advanced tumors].

44 patients with different advanced malignant tumors were treated with recombinant Tumor-necrosis factor alpha (rTNF-alpha) in two Phase-I trials. 30 patients received rTNF-alpha 3 x/week intramuscular in doses between 25-300 mcg. 14 patients were treated intra/peritumoral with rTNF-alpha in the same dose range. The maximal tolerated dose (MTD) was 150 mcg/m2 for both ways of application. The duration of therapy was 1-26 weeks for systemic application and 2-20 weeks for local treatment. 25 patients treated systemically were evaluable for response. In 2 patients a minor response (MR) and in 9 patients stable disease was observed. 5/14 patients receiving rTNF-alpha locally showed a significant tumor regression (3 PR, 2 MR). Main side effects were dose dependent fever, chills, anorexia and nausea. In doses greater than 50mcg/m2 a decrease of blood pressure according to WHO III was noted. Hematologic toxicity included a transient decrease of leucocytes and platelets without indicating a cumulative hematologic toxicity. There were no further organ toxicities. The experience from both phase-I trials indicate a definite antitumoral activity of rTNF-alpha suggesting that locoregional treatment might be superior to systemic application. The side effects observed might be a limitation for larger clinical trials.

Adult↗
PubMed1989

Modulation of major histocompatibility complex (MHC) class I genes in adenovirus 12 transformed cells: interferon-gamma increases class I expression by a mechanism that circumvents E1A induced-repression and tumor necrosis factor enhances the effect of interferon-gamma.

The protein products of the E1A gene of adenovirus type-12 (Ad12) block transcription of major histocompatibility (MHC) class I genes in both rodent and human transformed cells and interferon-gamma (IFN-gamma) is able to override this repression. Although IFN-gamma is known to stimulate class I transcription, we investigated whether its dominance over E1A repression could alternatively result from the ability of this cytokine to induce antiviral mechanisms. We show that this is not so, since the accumulation of Ad12 E1A mRNA and protein are unabated in the presence of IFN-gamma. Also, tumor necrosis factor (TNF) was shown to act synergistically with IFN-gamma to enhance class I antigen levels, although it had little effect alone. These results suggest that the normal pathway by which IFN-gamma acts to enhance the level of class I mRNAs, circumvents the block by which E1A represses class I transcription.

Adenovirus Early Proteins↗
PubMed1989

N-glycosidase treatment of Colo 205 cells interferes with hIFN-gamma induced HLA-DR expression.

We investigated the effects of N-glycosidase treatment on the interferon-gamma (IFN-gamma) induced HLA-DR expression of Colo 205 cells. N-glycosidase treatment resulted in a significant decrease of IFN-gamma induced HLA-DR specific immunofluorescence intensity ranging from complete reduction to approximately 30% of that of untreated control cells depending on the IFN-gamma dose. IFN-gamma binding studies showed that this was due to a severe reduction in IFN-gamma binding capacity of N-glycosidase treated cells. Since the number of cell membrane IFN-gamma receptors (IFN-gamma-Rs) was virtually unchanged as revealed by immunofluorescence analysis with a hIFN-gamma-R specific monoclonal antibody this indicates that N-linked carbohydrates play an important role in signal transduction and ligand binding capacity of the hIFN-gamma-R and strengthens the view that carbohydrate moieties of receptor proteins are of greater functional significance than originally anticipated.

Cell Line↗