Showing papers by "Michael B. Sporn published in 1990"
TL;DR: It is reported that administration of anti-TGF-βl at the time of induction of the glomerular disease suppresses the increased production of extracellular matrix and dramatically attenuates histological manifestations of the disease.
Abstract: GLOMERULONEPHRITIS is an inflammation of the kidney characterized by the accumulation of extracellular matrix within the damaged glomeruli1–4, impaired filtration and proteinuria. In its progressive form, the disease destroys kidney function leading to uraemia and death, unless dialysis therapy or kidney transplantation is available. The pathogenesis of glomerulonephritis is incompletely understood, but the eliciting factor is thought often to be an immunological injury to mesangial and/or other resident cells in the glomeruli5,6. We have used an animal model of acute mesangial proliferative glomerulonephritis7,8 to show that this disease is associated with increased production and activity of transforming growth factor β1 (TGF-βl)9, an inducer of extracellular matrix production10–17. Here we report that administration of anti-TGF-βl at the time of induction of the glomerular disease suppresses the increased production of extracellular matrix and dramatically attenuates histological manifestations of the disease. These results provide direct evidence for a causal role of TGF-βl in the pathogenesis of the experimental disease and suggest a new approach to the therapy of glomerulonephritis.
1,024 citations
TL;DR: Exogenous transforming growth factor-beta injections into the subperiosteal region of newborn rat femurs demonstrate that mesenchymal precursor cells in the periosteum are stimulated by TGF-beta to proliferate and differentiate, as occurs in embryologic bone formation and early fracture healing.
Abstract: We have investigated the ability of exogenous transforming growth factor-beta (TGF-beta) to induce osteogenesis and chondrogenesis, critical events in both bone formation and fracture healing. Daily injections of TGF-beta 1 or 2 into the subperiosteal region of newborn rat femurs resulted in localized intramembranous bone formation and chondrogenesis. After cessation of the injections, endochondral ossification occurred, resulting in replacement of cartilage with bone. Gene expression of type II collagen and immunolocalization of types I and II collagen were detected within the TGF-beta-induced cartilage and bone. Moreover, injection of TGF-beta 2 stimulated synthesis of TGF-beta 1 in chondrocytes and osteoblasts within the newly induced bone and cartilage, suggesting positive autoregulation of TGF-beta. TGF-beta 2 was more active in vivo than TGF-beta 1, stimulating formation of a mass that was on the average 375% larger at a comparable dose (p less than 0.001). With either TGF-beta isoform, the dose of the growth factor determined which type of tissue formed, so that the ratio of cartilage formation to intramembranous bone formation decreased as the dose was lowered. For TGF-beta 1, reducing the daily dose from 200 to 20 ng decreased the cartilage/intramembranous bone formation ratio from 3.57 to zero (p less than 0.001). With TGF-beta 2, the same dose change decreased the ratio from 3.71 to 0.28 (p less than 0.001). These data demonstrate that mesenchymal precursor cells in the periosteum are stimulated by TGF-beta to proliferate and differentiate, as occurs in embryologic bone formation and early fracture healing.
773 citations
TL;DR: These results demonstrate that both components of the AP-1 complex are required for TGF-beta 1 autoinduction, and may amplify the action of TGF -beta 1 during normal development and oncogenesis.
Abstract: The multifunctional actions of transforming growth factor beta 1 (TGF-beta 1) indicate that it has a pivotal control function in many physiological and pathological processes. An important property of TGF-beta 1 is its ability to activate its own mRNA expression and thereby increase its own secretion. Two distinct regions of the promoter of the TGF-beta 1 gene are responsive to autoregulation: one 5' to the upstream transcriptional start site and another located between the two major start sites. In both promoter regions, autoinduction is mediated by binding of the AP-1 (Jun-Fos) complex. An important contribution to this positive regulation is the autoactivation of c-jun transcription by AP-1. Cotransfection of antisense c-jun or antisense c-fos expression vectors prevents TGF-beta 1 autoinduction. These results demonstrate that both components of the AP-1 complex are required for TGF-beta 1 autoinduction. Induction of jun expression by TGF-beta 1, as well as jun autoinduction, may amplify the action of TGF-beta 1 during normal development and oncogenesis.
664 citations
TL;DR: The results suggest common elements in latent complex structure despite differences between the TGF-beta subtypes in pro-region primary sequence as well as a common series of sharply defined parameters for activation.
Abstract: Native and recombinant forms of transforming growth factor-beta 1 (TGF-beta 1) are synthesized predominantly as biologically latent complexes Physicochemical analysis demonstrates that the more recently described TGF-beta 2 and TGF-beta 3 are also latent, and reveals a common series of sharply defined parameters for activation Human recombinant latent TGF-beta's 1 and 2 show identical profiles of activation by acid and base; the transition from latency occurs between pH 41 and 31, and between pH 110 and 119 The profile for chicken recombinant latent TGF-beta 3 is slightly shifted with activation between pH 31 and 25, and between pH 100 and 123 Thermal activation of native and recombinant latent TGF-beta 1 occurs over the temperature ranges of 75-100 degrees C and 65-100 degrees C, respectively, with complete activation after 5 min at 80 degrees C Temperatures above 90 degrees C result in thermal denaturation of TGF-beta 1 itself Recombinant latent TGF-beta's 2 and 3 are also activated over this temperature range; however, maximum activation occurs at 100 degrees C These results suggest common elements in latent complex structure despite differences between the TGF-beta subtypes in pro-region primary sequence
360 citations
TL;DR: The results suggest that formation of latent complexes may switch endogenous TGF-beta 1 from an autocrine/paracrine mode of action to a more endocrine mode involving target organs distant from the site of synthesis.
Abstract: Transforming growth factor beta 1 (TGF-beta 1) is a key regulator of cell growth and differentiation. Under normal physiological conditions, it is made as a biologically latent complex whose significance is unknown. Previous work has indicated that active TGF-beta 1 has a very short plasma half-life in rats (Coffey, R. J., L. J. Kost, R. M. Lyons, H. L. Moses, and N. F. La-Russo. 1987. J. Clin. Invest. 80:750-757). We have investigated the possibility that latent complex formation may extend the plasma half-life of TGF-beta 1 and alter its organ distribution. Radiolabeled latent TGF-beta 1 was formed by noncovalent association of 125I-TGF-beta 1 with the TGF-beta 1 precursor "pro" region from recombinant sources. TGF-beta 1 in this latent complex had a greatly extended plasma half-life (greater than 100 min) in rats compared with active TGF-beta 1 (2-3 min). Whereas active TGF-beta 1 was rapidly taken up by the liver, kidneys, lungs, and spleen and degraded, TGF-beta 1 in the latent complex was largely confined to the circulation, and was less than 5% degraded after 90 min. The pharmacokinetics of TGF-beta 1 in the latent complex were shown to be critically dependent on the degree of sialylation of the complex. The results suggest that formation of latent complexes may switch endogenous TGF-beta 1 from an autocrine/paracrine mode of action to a more endocrine mode involving target organs distant from the site of synthesis.
313 citations
TL;DR: TGF-beta research is proceeding at an exponential pace, and studies in this area have become increasingly relevant to many areas of cell regulation, continually providing new surprises and findings.
Abstract: TGF-beta research is proceeding at an exponential pace. Studies in this area have become increasingly relevant to many areas of cell regulation, continually providing new surprises and findings. One may confidently predict that TGF-beta will be one of the key molecules in future attempts to establish an integrated view of the processes whereby cells coordinate their own and mutual functions. We have seen only the beginning, and this minireview is only a glimpse.
238 citations
TL;DR: A role for Tax in the upregulation of TGF-beta 1 in HTLV-I-infected cells is suggested, which is similar to that suggested for T lymphotropic virus type 1.
Abstract: We examined the effect of the human T lymphotropic virus type 1 (HTLV-I) Tax gene product on the human transforming growth factor beta 1 (TGF-beta 1) promoter. Transfection of deleted constructs of the TGF-beta 1 promoter revealed regions homologous with AP-1 binding sites that were required for Tax-induced transactivation of the TGF-beta 1 promoter. In addition, we examined the expression and secretion of TGF-beta in fresh leukemic cells isolated from patients with adult T cell leukemia (ATL) and in HTLV-1-infected T cell lines. We report that fresh leukemic cells from ATL patients constitutively produce high levels of TGF-beta 1 mRNA and secrete TGF-beta 1 but not TGF-beta 2 into the culture medium. In addition, long-term ATL cell lines expressed significant amounts of TGF-beta 1 mRNA as well as detectable levels of TGF-beta 1 protein. These results suggest a role for Tax in the upregulation of TGF-beta 1 in HTLV-I-infected cells.
222 citations
TL;DR: The results indicate colocalization of TGF-beta 1 expression and that of matrix proteins in the developing lung when branching morphogenesis (cleft formation) and tissue stabilization occur, and suggests a direct participation of the growth factor in the development of the basic architecture of the lung.
Abstract: The possible in vivo role of TGF-beta 1 in regulating various proteins of the extracellular matrix, including fibronectin, collagen I and III, and glycosaminoglycans, was examined by immunohistochemical methods during critical stages of lung morphogenesis in the 11- to 18-day-old mouse embryo. Sections of Bouin-fixed, paraffin-embedded whole embryos were exposed to polyclonal antibodies specific to synthetic peptides present in the precursor part of TGF-beta 1 (pro-TGF-beta 1), in the processed TGF-beta 1 (antibody CC), collagen I and III, fibronectin, followed by the PAP or ABC technique to visualize the location of the antibody. GAG were stained with Alcian Blue 8GX. Our results indicate colocalization of TGF-beta 1 expression and that of matrix proteins in the developing lung when branching morphogenesis (cleft formation) and tissue stabilization occur. The presence of TGF-beta 1 at the epithelial-mesenchymal interfaces of stalks and clefts at a time when matrix proteins can first be visualized in these areas, suggests a direct participation of the growth factor in the development of the basic architecture of the lung.
221 citations
TL;DR: The ability of TGF-β to improve and/or accelerate tissue repair has been studied extensively in a variety of animal models of both normal and impaired healing.
216 citations
TL;DR: The present volume on transforming growth factor-betas (TGF-0s) provides a summation of the current excitement in research on this family of peptides and briefly summarizes the present range of E F p studies.
Abstract: The present volume on transforming growth factor-betas (TGF-0s) provides a summation of the current excitement in research on this family of peptides. This excitement is largely the result of the realization that the study of TGF-p in its multiple forms is germane to almost any topic in the entire field of biomedical research. E F p indeed is the prototypical multifunctional peptide growth factor. It is now recognized that essentially all cells may synthesize one or another isoform of TGF-P and that almost all normal cells possess functional membrane-bound receptors for members of this family of peptides. Thus, TGF-P can act by both autocrine and paracrine mechanisms to regulate the behavior of almost every cell in the mammalian organism. Depending on the particular cellular context of its action, TGF-p may act as a signal at certain times to enhance cellular proliferation, at other times to inhibit cellular proliferation, and in still other circumstances to modulate numerous other activities of cells that relate to their differentiated state, but are unrelated to DNA synthesis. In the present article, we will give a short historical introduction to the development of TGF-p research, then briefly summarize the present range of E F p studies, and finally conclude with some speculations about the directions of future research on EF-p .
214 citations
TL;DR: In Rous sarcoma virus-infected chickens, wounding leads to tumor formation with nearly 100% frequency in tissues that would otherwise remain tumor-free, and TGF-beta release during the wound-healing response may be a critical event that creates a conducive environment for RSV tumorigenesis and may act as a cofactor for transformation in this system.
Abstract: In Rous sarcoma virus (RSV)-infected chickens, wounding leads to tumor formation with nearly 100% frequency in tissues that would otherwise remain tumor-free. Identifying molecular mediators of this phenomenon should yield important clues to the mechanisms involved in RSV tumorigenesis. Immunohistochemical staining showed that TGF-beta is present locally shortly after wounding, but not unwounded controls. In addition, subcutaneous administration of recombinant transforming growth factor-beta 1 (TGF-beta 1) could substitute completely for wounding in tumor induction. A treatment protocol of four doses of 800 nanograms of TGF-beta resulted in v-src-expressing tumors with 100% frequency; four doses of only 10 nanograms still led to tumor formation in 80% of the animals. This effect was specific, as other growth factors with suggested roles in wound healing did not elicit the same response. Epidermal growth factor (EGF) or TGF-alpha had no effect, and platelet-derived growth factor (PDGF) or insulin-like growth factor-1 (IGF-1) yielded only occasional tumors after longer latency. TGF-beta release during the wound-healing response may thus be a critical event that creates a conducive environment for RSV tumorigenesis and may act as a cofactor for transformation in this system.
TL;DR: Mechanistically, TGF-beta s act to control gene expression of their target cells, many of their actions converging on a complex, multifaceted scheme of control of matrix proteins and their interactions with cells; these effects on matrix are thought to mediate many of the effects of TGF -beta on development.
Abstract: Transforming growth factors-beta (TGF-beta) are 25 kilodalton (kDa) homodimeric peptides with multifunctional actions controlling the growth, differentiation and function of a broad range of target cells of both epithelial and mesenchymal derivation. They are expressed early in embryogenesis and their tissue-specific and developmentally dependent expression is strongly suggestive of an essential role in particular morphogenetic and histogenetic events. Five distinct TGF-beta s have been characterized so far, with 65-80% homology to each other. By using both molecular biological and immunohistochemical techniques, we are currently attempting to define specific sites of expression of the different TGF-beta s and to determine whether TGF-beta s 1-5 might have unique functions in development and in the mature organism. Comparative study of the promoter regions for the different TGF-beta s and for any particular TGF-beta in different species is also underway. Mechanistically, TGF-beta s act to control gene expression of their target cells, many of their actions converging on a complex, multifaceted scheme of control of matrix proteins and their interactions with cells; these effects on matrix are thought to mediate many of the effects of TGF-beta on development.
TL;DR: A novel transforming growth factor-beta (TGF-beta) mRNA of about 3.0 kilobases, which encodes a putative protein of 382 amino acids, has been identified in amphibians by cDNA cloning and is developmentally regulated and highly expressed beginning at early neurula and in many adult tissues in Xenopus laevis.
TL;DR: It is suggested that RA inhibits collagenase transcription at least in part through inhibition of c-fos, which plays a major role in cartilage and bone destruction in rheumatoid arthritis.
Abstract: Collagenase production by synovial fibroblast-like cells (synoviocytes) plays a major role in cartilage and bone destruction in rheumatoid arthritis. Interleukin-1 (IL-1) increases collagenase secretion by elevating the steady state levels of collagenase mRNA in cultured rheumatoid synoviocytes, while all-trans-retinoic acid (RA) has the opposite effect. We have studied the regulation of collagenase gene transcription by IL-1 and RA in synoviocytes by transient transfection of plasmid constructs containing deletion mutants of the 5'-flanking region of the collagenase gene or the isolated phorbol ester-responsive element ligated to a chloramphenicol acetyltransferase reporter gene. We show that the phorbol ester-responsive element of the collagenase gene mediates both positive and negative regulatory effects, respectively, of IL-1 and RA on transcription. In addition, we show that IL-1 and 12-O-tetradecanoyl-phorbol-13-acetate transiently induce c-jun and c-fos expression and that retinoic acid inhibits IL-1 and 12-O-tetradecanoyl-phorbol-13-acetate induction of c-fos, but not c-jun. These results suggest that RA inhibits collagenase transcription at least in part through inhibition of c-fos.
TL;DR: It is suggested that alpha 2M is an important differential regulator of the biological activities of T GF-beta 1 and TGF-beta 2 in vivo.
TL;DR: It is found that serum treatment increased TGF-beta 1 mRNA levels in 32D-123 cells and that the v-Src protein could replace the serum requirement by stimulating binding to the AP-1 complex of the T GF- beta 1 promoter, thereby mediating the induction of TGF -beta 1 transcription.
Abstract: Growth factor-independent 32D-src and 32D-abl cell lines, established by infecting the interleukin-3-dependent myeloid precursor cell line (32D-123) with retroviruses containing the src or abl oncogene, were used to study transcriptional regulation of transforming growth factor beta 1 (TGF-beta 1) mRNA. Analysis of different TGF-beta 1 promoter constructs regulated by pp60v-src indicated that sequences responsive to high levels of src induction contain binding sites for AP-1. Both src and serum induced expression of the c-fos and c-jun genes in myeloid cells, resulting in transcriptional activation of the TGF-beta 1 gene. We found that serum treatment increased TGF-beta 1 mRNA levels in 32D-123 cells and that the v-Src protein could replace the serum requirement by stimulating binding to the AP-1 complex of the TGF-beta 1 promoter, thereby mediating the induction of TGF-beta 1 transcription.
TL;DR: Since the TGF-beta s have activity in promoting or inhibiting proliferation and differentiation of multiple cell types, it seems likely that the differential and tissue-specific transcriptional regulation of these genes is of fundamental importance in the induction and maintenance of differentiated cell types in various tissues.
TL;DR: A significant level of TGF-beta 2 secretion and receptor binding occur before the decrease in DNA synthesis, suggesting that the inhibition of DNA synthesis associated with differentiation of keratinocytes is mediated through the production and autocrine action of T GF- beta 2.
Abstract: Primary cultures of mouse keratinocytes maintain a basal cell phenotype in 0.05 mm Ca2+ medium, while culture in 1.4 mm Ca2+ results in terminal differentiation and inhibition of DNA synthesis. Induction of differentiation by Ca2+ results in a 10- to 20-fold increase in the expression of transforming growth factor-β2 (TGF-β2) mRNA and peptide, but a decrease in the expression of TGF-β1. In contrast, binding and cross-linking analyses show that the number of available surface 80 kilodalton (kDa) and 65 kDa TGF-β receptor types decrease during differentiation. However, a mild acid wash significantly increases the number of available receptor sites on the differentiated keratinocytes, indicating that the TGF-β receptors are unavailable for binding due to masking by endogenous ligand. A significant level of TGF-β2 secretion and receptor binding occur before the decrease in DNA synthesis, suggesting that the inhibition of DNA synthesis associated with differentiation of keratinocytes is mediated through the pr...
TL;DR: Using a simian transforming growth factor-beta 2 (TGF- Beta 2) cDNA probe, isolated chicken cDNA clones for TGF- beta 2 from a chicken embryo chondrocyte cDNA library is isolated and the predicted precursor protein is 412 amino acids long, two amino acids shorter than the human form.
Abstract: Using a simian transforming growth factor-β2 (TGF-β2) cDNA probe, we have isolated chicken cDNA clones for TGF-β2 from a chicken embryo chondrocyte cDNA library. The predicted precursor protein of chicken TGF-β2 is 412 amino acids long, two amino acids shorter than the human form to which it shows 90% identity. Cleavage of the chicken TGF-β2 precursor at a pentabasic Arg-Arg-Lys-Lys-Arg site would produce a 112-amino acid processed peptide differing by only one amino acid from the human TGF-β2 peptide. In contrast to TGF-β3 and 4 mRNAs, TGF-β2 mRNA is expressed in both cultured and non-cultured chicken embryo chondrocytes and at higher levels in chicken embryo fibroblasts. In chondrocytes and fibroblasts, the 3.9- and 4.3-kb TGF-β2 mRNAs are both expressed at higher levels than the 8-kb TGF-β2 mRNA; however, in developing chicken embryos, the level of expression of the 8-kb mRNA is higher than that of the 3.9- and 4.3-kb mRNAs.
TL;DR: The isolation of a murine TGF-beta 3 cDNA is reported, which hybridizes to a unique 3.5-kb RNA and is differentially expressed in various mouse tissues and at different embryonic stages.
Abstract: Two TGF-beta s, TGF-beta 1 and 2, have previously been isolated from the mouse. Here we report the isolation of a murine TGF-beta 3 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-beta 3 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-beta 3 cDNA were obtained. The mouse TGF-beta 3 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.
Journal Article•
TL;DR: Notably, the addition of PMA inhibited the increase in CAT activity in response to okadaic acid, which suggests that the activation of PKC may also induce inhibitory factors.
Abstract: We have used a specific phosphatase inhibitor, okadaic acid, to examine the role of two phosphatases, PP1 and PP2A, in the induction of NF-kappa B and the long terminal repeat of the human immunodeficiency virus type 1 (HIV-LTR). Treatment of Jurkat cells with okadaic acid induced NF-kappa B in nuclear extracts. The rate of induction by okadaic acid was delayed compared to the induction of NF-kappa B by phorbol myristate acetate (PMA). The induction of NF-kappa B by okadaic acid was enhanced by cycloheximide or phytohemagglutinin (PHA). In contrast to PMA, okadaic acid appeared to induce NF-kappa B independently of protein kinase C (PKC). That the NF-kappa B induced by okadaic acid was functional was demonstrated by the marked increase in CAT activity that occurred in Jurkat, BJA-B, and U251 cells that were transfected with HIV-LTR-CAT and treated with okadaic acid. The increase in CAT activity triggered by okadaic acid was dependent on the presence of the NF-kappa B sites in the long terminal repeat of HIV as assessed by deletion and mutation analysis. Similarly to its effect on the induction of NF-kappa B, PHA added together with okadaic acid resulted in a further increase in CAT activity. Somewhat surprisingly, the addition of PMA inhibited the increase in CAT activity in response to okadaic acid, which suggests that the activation of PKC may also induce inhibitory factors.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: The results suggest that more complex systems, in contrast to individual cell types, may respond selectively to the various TGF-beta isoforms and that there might be biological consequences of TGF -beta isoform switching in vivo.
Abstract: Induction of mesoderm in ectodermal explants of Xenopus laevis blastula embryos had previously been shown to respond selectively to TGF-β2, with TGF-βs 1 and 5 having no activity in this assay. As TGF-βs 1, 2, and 3 are frequently coexpressed in tissues, we wished to examine the activity of TGF-β3 relative to that of TGF-βs 1 and 2 in this assay as well as in other in vitro assays. We report here that when the activity of recombinant TGF-β3 is normalized to that of TGF-β1 in the assay for growth inhibition in CCL-64 cells, it is also equal to that of TGF-β1 in assays for stimulation of both anchorage-independent growth of rat NRK cells and chemotaxis of human monocytes. In contrast, in the assay for mesoderm induction, recombinant TGF-β3 is 10-fold more active than TGF-β2, inducing expression of muscle specific α-actin at concentrations as low as 1 ng/ml. These results suggest that more complex systems, in contrast to individual cell types, may respond selectively to the various TGF-β isoforms and...
TL;DR: It is suggested that phosphorylation regulates collagenase gene expression mediated by an AP-1 binding site through a region known to contain multiple regulatory elements.
Abstract: Human collagenase gene expression is regulated transcriptionally and is inducible by various mitogens in many cell types. To investigate the molecular mechanisms of this response, we examined the effects on collagenase gene expression of okadaic acid, a non-12-O-tetradecanoyl-phorbol-13-acetate (TPA)-type tumor promoter, which induces apparent "activation" of protein kinases by inhibition of protein phosphatases. Steady state levels of collagenase mRNA were markedly increased by okadaic acid treatment. We show that the AP-1 consensus sequence in the collagenase promoter is required for the induction of collagenase gene expression by okadaic acid, even though sequences upstream of the AP-1 consensus site have an additive effect. We also examined the regulation by okadaic acid of expression of the components of the AP-1 complex, c-fos and c-jun. c-fos expression is dramatically stimulated by okadaic acid, whereas c-jun expression is stimulated to a lesser extent. Induction of c-fos gene mRNA occurs through a region known to contain multiple regulatory elements. These results suggest that phosphorylation regulates collagenase gene expression mediated by an AP-1 binding site.
TL;DR: A stable stem-loop structure in the 5' untranslated region (UTR) of the TGF-beta 1 mRNA is identified that inhibits translation of a heterologous reporter gene, and the possibility that anti-estrogens may regulate the activity of this element, and hence the translatability of theTGF- beta 1 message is investigated.
Abstract: Transforming growth factor-beta s (TGF-beta s) are potent regulators of cell growth and differentiation. Expression of the closely related TGF-beta subtypes in vivo is differentially regulated both temporally and spatially. Members of the steroid hormone superfamily may play an important role in this gene- and tissue-specific regulation. We have shown that anti-estrogens induce the production of TGF-beta 1 in mammary carcinoma cells and fetal fibroblasts, whereas retinoic acid specifically induces TGF-beta 2 in primary epidermal keratinocytes. The induction of TGF-beta 2 by retinoids is accompanied by an increase in TGF-beta 2 mRNAs, but little change in transcription rates, suggesting an effect of retinoids on message stability or processing. In contrast, TGF-beta 1 mRNA levels are unchanged by anti-estrogen treatment, suggesting these compounds may regulate the translatability of the TGF-beta 1 message or some post-translational processing event. We have identified a stable stem-loop structure in the 5' untranslated region (UTR) of the TGF-beta 1 mRNA that inhibits translation of a heterologous reporter gene, and we are investigating the possibility that anti-estrogens may regulate the activity of this element, and hence the translatability of the TGF-beta 1 message. A significant fraction (25-90%) of the TGF-beta induced by retinoids and anti-estrogens is in the biologically active rather than the latent form. We have shown that active TGF-beta has a much shorter in vivo half-life than latent TGF-beta, suggesting that the TGF-beta induced by retinoids and steroids may act locally at the site of production. Since many tumor cells retain sensitivity to the growth inhibitory effects of active TGF-beta, the use of members of the steroid hormone superfamily for inducing this potent growth inhibitor locally at the tumor site may have therapeutic potential.
TL;DR: The view that cytokines such as PDGF, and possibly aFGF and bFGF, play major roles in stimulating synoviocyte hyperplasia in RA and SCW arthritis, whereas TGF-beta may inhibit synoviocytes growth is supported.
Abstract: Paracrine growth factors probably stimulate the pathologic proliferation of synovial fibroblast-like cells (synoviocytes) in rheumatoid arthritis (RA), but the relative importance of various factors is highly controversial. To address this problem, we compared the effects of highly purified or recombinant cytokines, in serum-free medium, on the in vitro long-term growth of synoviocytes from patients with RA and rats with streptococcal cell wall (SCW) arthritis. Of the factors tested (PDGF, aFGF, bFGF, EGF, TGF-beta, IL-1-alpha, TNF-alpha and IFN-gamma), PDGF, was clearly the most potent stimulant of long-term growth of both rat and human synoviocytes. The strong mitogenic activity of rheumatoid synovial fluids was significantly inhibited by neutralizing anti-PDGF antibody, thus confirming the importance of PDGF. EGF, TGF-beta, IL-1-alpha, TNF-alpha, and IFN-gamma had minimal effects. Similar to the effects on anchorage-independent growth, TGF-beta 1 and 2, inhibited serum- or PDGF-stimulated anchorage-dependent growth. Considered in the context of other reports, these data support the view that cytokines such as PDGF, and possibly aFGF and bFGF, play major roles in stimulating synoviocyte hyperplasia in RA and SCW arthritis, whereas TGF-beta may inhibit synoviocyte growth.
TL;DR: Its properties in vitro suggest that it might be important in such processes as cardiac embryogenesis, hypertrophy, atherogenesis, healing of myocardial infarction, and development of coronary collaterals.
Abstract: Transforming growth factor-61 is a multifunctional peptide' found in platelets and most organs, including the heart? Although nothing is known of the role(s) played in the heart by TGF-61, its properties in vitro suggest that it might be important in such processes as cardiac embryogenesis, hypertrophy, atherogenesis, healing of myocardial infarction, and development of coronary collaterals. The gene for TGF-Pl, and other genes of the TGF-P family, have been cloned? Although the receptor for TGF-PI and the means of signal transduction have been only partially characterized, it is clear that almost all cells express receptors for TGF-Pl, at least in culture! Effects on growth, migration, and differentiation of a wide variety of cells have been demonstrated and found to vary markedly with cell culture conditions. In general, however, TGF-61 inhibits cell growth, particularly that of epithelial cells. TGF-Dl can enhance or inhibit the proliferation of vascular smooth muscle cells depending on density.' TGF-(31 inhibits the proliferation of endothelial cells in monolayer culture, even in the presence of basic fibroblast growth factor.5s6 However, in three-dimensional collagen gels, TGF01 rapidly induces endothelial cells to invade the gel and form capillarylike tubular structures?
TL;DR: None of the TGF-β2 peptide antibodies was able to block receptor binding of either TGF -β1 or 2, and both anti-P 50–75(2) andAnti-P 79–108 (2) specifically immunoprecipitated TGF,β2 under reducing conditions only.
Abstract: Polyclonal antibodies have been raised to synthetic peptides corresponding to several regions of transforming growth factor-β2 (TGF-β2). All antisera were tested for their ability to react with either the native or reduced forms of both TGF-β1 and TGF-β2 in enzyme-linked immunosorbent assays, Western blots, and immunoprecipitation assays. On Western blots, antisera raised to a peptide corresponding to residues 50–75 of TGF-β2 specifically detected 5 ng TGF-β2, while antisera raised to regions 1–30 and 79–108 cross-reacted with TGF-β1. Anti-P 50–75(2) also localized TGF-β2 in murine placenta in immunohistochemical studies. In immunoprecipitation assays with either iodinated TGF-βs or with media conditioned by cells labeled with [35S]Jcysteine, both anti-P 50–75(2) and anti-P 79–108(2) specifically immunoprecipitated TGF-β2 under reducing conditions only, while anti-P 79–108(2) also reacted with TGF-β1. None of the TGF-β2 peptide antibodies was able to block receptor binding of either TGF-β1 or 2. A...
TL;DR: Despite the greatly enhanced rate of secretion of activated T GF-β, metastatic cells exhibited markedly altered responses of TGF-β1, and TGF -β2., being unable to either increase collagen sec...
Abstract: We 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 -β2 and the regulation of TGF-β-responsive genes in oncogene-transformed metastatic fibrosarcomas. All transformed lines derived from either 10T1/2; or N1H 3T3 bv either H-ras or protein-kinase encoding oncogenes produced more TGF-β than parental cells. However, onlv highlv metastatic fibrosarcomas secreted activated TGF-β at 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 sec...
Journal Article•
TL;DR: This review will be limited to a discussion of transcriptional regulation of the activity of mF-0 in a variety of in vitro and in vivo systems and of evidence suggesting that expression of the five TGF-ps is under different celland tissue-specific transcriptional control.
Abstract: In recent years, there has been an exponential increase in understanding of the chemistry and biology of the family of peptides called transforming growth factor-S (TGFp). The discovery and characterization of five distinct, highly conserved, yet functionally similar TGF-Ps has added an unexpected level of complexity to the problems of defining the roles of the different TGF-Ps in normal and pathological physiology! Furthermore, understanding of the biology of the TGF-ps, once narrowly defined by their ability to confer a transformed phenotype on nonneoplastic NRK fibroblasts, has now expanded to include effects on almost every cell type and to range from processes such as control of steroidogenesis or control of epithelial cell growth and differentiation, to more complex processes involving multiple cell types such as wound healing, bone remodeling, hemopoiesis, or specific morphogenetic and histogenetic events in embryonic development ! Given the many cell types sensitive to TGF-p action, it is clear that multiple levels of control of its activity must exist. Though control of TGF-P receptor expression, receptor signalling, and activation of the latent forms of the various TGF-Ps are without doubt important, this review will be limited to a discussion of transcriptional regulation of the activity of mF-0 in a variety of in vitro and in vivo systems and of evidence suggesting that expression of the five TGF-ps is under different celland tissue-specific transcriptional control.