摘要:

AbstractPlatelet-derived growth factor (PDGF) occurs as three dimeric isoforms, AA, BB, and AB. Two distinct receptor subunits,αandβ, have been identified which bind either all three isoforms of PDGF (α) or PDGF-BB only (β). Here, we have compared the effect of purified PDGF homodimers on the early intracellular signaling events and mitogenesis in Swiss 3T3 cells, which possess equivalent numbers of theαandβsubunits. Both PDGF-AA and PDGF-BB stimulated receptor phosphorylation, inositol phosphate formation, activation of protein kinase C, calcium mobilization, EGF receptor transmodulation, sodium uptake, arachidonic acid release, cyclic AMP accumulation, andc-fosinduction in a comparable, dose-dependent manner (half-maximal values for all these responses were in the 2–10 ng/ml range for both homodimers). At high concentrations of PDGF (>10 ng/ml), the BB homo-dimer effect on early membrane and cytosolic signals was 20–30% greater than PDGF-AA, reflecting the greater number of available binding sites for PDGF-BB. DNA synthesis studies indicated that PDGF-AA and PDGF-BB were potent mitogens for Swiss 3T3 cells, displaying identical dose-response effects. Moreover, the mitogenic activities of both homodimers were equally potentiated in the presence of insulin. These results indicate that both PDGF-AA and PDGF-BB stimulate the full complement of molecular responses required for the synergistic interactions mediating long-term mitogenesis. We conclude thatαandβreceptor subunits do not differ in their ability to transduce PDGF-mediated signals leading to DNA synthesis in Swiss 3T3 cells.

ISSN:0897-7194    

DOI:10.3109/08977199009108271

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractEpidermal growth factor receptors (EGF-R) are present in a number of human breast cancer cell lines and tumor biopsies. Furthermore, it has been suggested that EGF-R levels are higher in estrogen receptor negative (ER-) than in ER + human breast tumors and that EGF-R status may be a prognostic indicator in breast cancer. The present study was undertaken to establish whether there is a quantitative relationship between EGF-R and ER mRNA concentrations in a series of 10 well-characterized human breast cancer cell lines. All cell lines expressed detectable quantities of EGF-R mRNA by Northern analysis but the relative abundance of EGF-R mRNA varied more than 50-fold. Two transcripts corresponding to the 10.5- and 5.8-kb mRNAs described in other cell types were present but in different relative proportions in different cell lines. When these lines were divided into an ER+ and an ER- group based on their ability to bind estradiol, ER- cell lines were shown to express significantly higher concentrations of EGF-R mRNA than did ER+ cell lines (p<0.005). Furthermore, linear-regression analysis revealed a significant inverse relationship between ER and EGF-R mRNA concentrations both within the group of 10 human breast cancer cell lines as a whole (r = 0.66) and within the 6 functionally ER+ lines (r= 0.77). This demonstration of a significant (p<0.005) inverse relationship between the concentrations of ER and EGF-R mRNAs in ER + cell lines raises the possibility of reciprocal regulation of the expression of these genes in human breast cancer.

ISSN:0897-7194    

DOI:10.3109/08977199009108272

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractDefatted bovine colostrum and decaseinated whey contain biological activity similar to that of TGF-βin that they stimulate the anchorage-independent growth of NRK-49F cells in the presence of EGF. Two new proteins with such activity, termed BC-1 and BC-2, were isolated from decaseinated colostrum by a sequence of DEAE-Sephacel chromatography, Sephadex G-100 gel filtration in 1 M acetic acid, Sephadex G-50 re-gelfiltration in 8 M urea-1 M acetic acid and reverse-phase FPLCs. The two proteins showed distinctly different molecular weight from that of TGF-β1. BC-1 was a small Mrpeptide of 8.5 kD. BC-2 had molecular mass of 46 kD, which yielded peptides of 46, 40, and 6 kD on reduction. In contrast to TGF-β, both proteins did not lose their biological activity on reduction. Both BC-1 and BC-2 suppress DNA synthesis in concanavalin A-stimulated thymocytes. These results suggest that BC-1 and BC-2 belong to a new class of mitogen/inhibitors, though their biological activities resemble those of TGF-β.

ISSN:0897-7194    

DOI:10.3109/08977199009108273

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractWe have examined the possible role of transforming growth factor-β(TGF-β) in metastatic malignancy by analyzing the production and activation of TGF-β, and -β2and the regulation of TGF-β-responsive genes in oncogene-transformed metastatic fibrosarcomas. All transformed lines derived from either 10T1/2; or N1H 3T3 bv eitherH-rasor protein-kinase encoding oncogenes produced more TGF-βthan parental cells. However, onlv highlv metastatic fibrosarcomas secreted activated TGF-βat rates that were greater than parental fibroblasts. Immunohistochemical staining for TGF-β, showed widespread intra- and extracellular distribution in metastatic lung nodules and adjacent tissue. Cells isolated from tumors successfully metastasizing to the lung had TGF-β1, mRNA levels which were increased 19-fold over in ritro controls. Despite the greatly enhanced rate of secretion of activated TGF-β, metastatic cells exhibited markedly altered responses of TGF-β1, and TGF-β2., being unable to either increase collagen secretion or enhance collagen a2(l) or TGF-β1, mRNA levels. This lack of response was not due to either altered TGF-βreceptor affinity or numbers. Metastatic progression was, therefore, associated with an increase in the secretion of activated TGF-β1and a loss of the ability to deregulate TGF-β-responsive genes.

ISSN:0897-7194    

DOI:10.3109/08977199009108274

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractChinese hamster ovary (CHO) clones secreting high levels of transforming growth factor-β2 (TGF-β2) were obtained after transfection with a cDNA clone coding for the 414-amino acid TGF-β2 precursor and subsequent amplification with methotrexate. The TGF-β2 was secreted in a latent form since acidification was necessary for detection of maximal levels of bioactivity. Amino- and carboxy-terminal sequencing of purified recombinant TGF-β2 indicated that correct processing of mature TGF-β2 had occurred. In addition to mature TGF-β2, the recombinant CHO clones secreted larger proteins having molecular weights of 85, 105, and 130 kD, which consisted of both mature and pro-region sequences when analyzed by immunoblotting using site-specific anti-peptide antibodies. Analysis of serum-and cell-free media from recombinant CHO cells metabolically labeled with [3Hglucosamine and [32Porthophosphate indicated that pro-TGF-β2 was glycosylated and phosphorylated. Two-dimensional electrophoretic analysis of acid hydrolysates showed that the32P was incorporated into mannose-6-phosphate.

ISSN:0897-7194    

DOI:10.3109/08977199009108275

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractTwo TGF-βs, TGF-β1 and 2, have previously been isolated from the mouse. Here we report the isolation of a murine TGF-β3 cDNA. RNAs extracted from 15-day-old mouse embryos and several mouse cell lines were reverse-transcribed. These cDNA mixtures were used as substrates for polymerase chain-reaction amplifications, using oligonucleotides designed on the basis of known human and chicken TGF-β3 sequences, including the initiation and stop codons. Several overlapping cDNAs containing either the amino-terminal domain or the carboxy-terminal domain, as well as the complete 1.2-kb coding region of the mouse TGF-β3 cDNA were obtained. The mouse TGF-β3 coding region is 1230 nucleotides long and codes for a 410 amino acid polypeptide very similar to its human counterpart. This cDNA hybridizes to a unique 3.5-kb RNA and is differentially expressed in various mouse tissues and at different embryonic stages.

ISSN:0897-7194    

DOI:10.3109/08977199009108276

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractIt has been shown that bone cells produce and secrete several growth factors (GFs) which are also found in the bone matrix. To investigate the role of these growth factors in bone cell metabolism, we compared the effects of different factors separately and in combination with respect to osteoblastic cell proliferation and differentiation. While basic fibroblast GF (FGF), transforming GFβ-1 (TGFβ), and platelet-derived GF (PDGF) enhance DNA synthesis, they had the opposite effect on alkaline phosphatase (ALP) activity in cell extracts: FGF, TGFβ, and PDGF inhibited cell ALP but strongly stimulated DNA synthesis. The IGFs had little effect on cell ALP but increased the release of ALP into the conditioned medium. In mitogenic tests of combinations of GFs, most had at least additive effects at low concentrations, and FGF, TGFβ, and IGF2 produced synergistic effects. Evidence is presented for (1) the modulation of the effects of one GF by the action of other GF, (2) synergistic interactions between FGF, TGFβ, and IGF2, and (3) a possible role for the observed interactions among GF for the mitogenic effect of human bone extract.

ISSN:0897-7194    

DOI:10.3109/08977199009108277

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

AbstractOne approach to the localization of functionally active regions of human granulocyte-macrophage colony-stimulating factor (hGM-CSF) is to map the epitopes recognized by neutralizing anti-hGM-CSF monoclonal antibodies. We have defined the epitope recognized by one neutralizing antibody (LMM102) using proteolytic fragments obtained by enzymic digestion of bacterially synthesized hGM-CSF. RP-HPLC fractionation of a tryptic digest resulted in the identification of an immunoreactive“tryptic core”peptide containing 66 amino acids (52% of the protein). Further digestion of this“tryptic core”withS. aureusV8 protease produced a unique immunoreactive hGM-CSF product comprising two peptides, residues 86–93 and 112–127, linked by a disulfide bond between residues 88 and 121. The individual peptides, generated by reduction with dithiothreitol, were not recognized by the antibody. An analog of this peptide has been synthesized chemically and shown to have similar immunoreactivity to the epitope obtained by enzymic digestion. A series of modified peptides has also been synthesized to identify further the region required for antibody recognition.

ISSN:0897-7194    

DOI:10.3109/08977199009108278

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor