A heparin-binding growth factor secreted by macrophage-like cells that is related to EGF

Synthesis and biological activity of N-terminal-truncated derivatives of human epidermal growth factor (h-EGF)

To investigate the contribution of the N-terminal sequence of h-EGF to its biological activity and the formation of three intramolecular disulfide bonds by oxidative refolding via air oxidation, five derivatives of h-EGF with a single N-terminal amino acid deletion were synthesized by solid-phase synthesis. The homogeneity of the synthetic peptides was confirmed by analytical reversed-phase HPLC, amino acid analysis, and FAB-MS. The pairing of the three disulfide bridges in synthetic peptides was determined by thermolytic digestion. All N-truncated derivatives of h-FGF formed the correct intramolecular three disulfide linkages during oxidative refolding and had equipotent activity in both EGF receptor binding on A-431 epidermoid carcinoma cells and mitogenesis on NIH-3T3 fibroblast cells, compared with authentic h-EGF. The results suggested that the five residues from N-terminal sequence of h-EGF have no effect on the formation of the correct disulfide linkages in h-EGF and do not exert a significant influence on its biological activity.

Localization of heparin-binding EGF-like growth factor in the smooth muscle cells and macrophages of human atherosclerotic plaques

Heparin-binding EGF-like growth factor (HB-EGF) is a potent chemoattractant and mitogen for smooth muscle cells (SMC) in culture. To elucidate whether HB-EGF is implicated in the pathogenesis of human atherosclerosis, we examined immunohistochemical localization of HB-EGF in human aortic walls and atherosclerotic plaques. The medial SMC of the aorta in babies and children synthesized HB-EGF protein, while the number of SMC producing HB-EGF was dramatically decreased in young and middle-aged adults. In atherosclerotic plaques, however, marked production of HB-EGF protein was detected in SMC and macrophages of the plaques. Furthermore, EGF receptors, to which HB-EGF is known to bind, were detected in plaque SMC. These data suggest that HB-EGF may be implicated in the migration and proliferation of SMC that occurs in the normal development of arterial walls, and in the formation of atherosclerotic plaques.

Heparin-induced oligomerization of FGF molecules is responsible for FGF receptor dimerization, activation, and cell proliferation

Heparin is required for fibroblast growth factor (FGF) stimulation of biological responses. Using isothermal titration calorimetry, we show that acidic FGF (aFGF) forms a 1:1 complex with the soluble extracellular domain of FGF receptor (FGFR). Heparin exerts its effect by binding to many molecules of aFGF. The resulting aFGF-heparin complex can bind to several receptor molecules, leading to FGFR dimerization. In two cell lines lacking endogenous heparan sulfate, exogenous heparin is required for FGFR dimerization, tyrosine kinase activation, c-fos mRNA transcription, and cell proliferation. Moreover, a synthetic heparin analog that binds monovalently to aFGF blocks FGFR dimerization, activation, and signaling via FGFR. We propose that heparin causes oligomerization of aFGF such that its binding to FGFR results in dimerization and activation. This represents a novel mechanism for transmembrane signaling and may account for the action of many heparin-bound growth factors.

Heparin-dependent binding and autophosphorylation of epidermal growth factor (EGF) receptor by heparin-binding EGF-like growth factor but not by EGF

Heparin-binding EGF-like growth factor (HB-EGF) is a recently identified member of the EGF family of growth factors and a potent mitogen for smooth muscle cells and fibroblasts. Chinese hamster ovary (CHO) cells genetically engineered to express the human EGF receptor bind with high affinity both EGF and HB-EGF. CHO mutant cells lacking heparan sulfate proteoglycans (HSPG) bind EGF equally well to wild-type cells and EGF binding is not affected by exogenous heparin. However, HSPG-deficient EGF receptor-expressing cells do not bind significant levels of HB-EGF unless heparin is present in the binding medium. Moreover, binding of radiolabeled EGF to HSPG-deficient EGF receptor-expressing cells is efficiently displaced by nonlabeled HB-EGF only in the presence of heparin. Signal transduction by the EGF receptor tyrosine kinase as evidenced by receptor autophosphorylation is induced by HB-EGF only in the presence of heparin, in contrast to EGF-induced receptor autophosphorylation, which is independent of heparin. These results directly demonstrate that HB-EGF but not EGF requires heparin or cell surface HSPG for binding and activation of the EGF receptor and that HB-EGF receptor interactions can be tightly regulated by the available local concentration of heparin-like molecules.

Expression of heparin-binding epidermal growth factor in human hepatocellular carcinoma

BACKGROUND/AIMS

Growth factors are involved in the development and progression of cancer. The purpose of this study was to evaluate the possible role of heparin-binding epidermal growth factor-like growth factor (HB-EGF), which is a member of the EGF family, in the neoplastic transformation of hepatocytes.

METHODS

Gene expression and protein production of HB-EGF were investigated in samples of human hepatocellular carcinoma (HCC) from 17 patients using Northern hybridization and immunohistochemical methods.

RESULTS

The amount of HB-EGF messenger RNA was increased in the patients' HCC specimens compared with the surrounding liver tissues. In noncancerous hepatic tissues, HB-EGF was faintly positive in hepatocytes. Immunoreactive HB-EGF-producing cells were identified in HCC cells of all 17 patients with HCC, indicating that HB-EGF was produced in HCC cells themselves. However, none of the specimens from 10 patients with metastatic adenocarcinoma in the liver was positive for HB-EGF. The EGF receptor, which binds to HB-EGF, was also expressed on HCC cells.

CONCLUSIONS

It is hypothesized that the enhanced expression of immunoreactive HB-EGF on the cell suggests a possible role of HB-EGF in the development or progression of human HCC in an autocrine and/or a juxtacrine manners.

Heparin and its non-anticoagulant analogues inhibit human keratinocyte growth without inducing differentiation

In addition to its anti-coagulant effect, heparin inhibits the growth of several types of cells. Recent studies suggest that heparin inhibition of proliferation of cultured human keratinocytes, results primarily from interaction with keratinocyte-generated, heparin-binding autocrine growth factors. In this study, we evaluated whether non-anticoagulant heparin analogs, and oligosaccharide fragments of heparin, retain the growth-inhibitory properties of whole heparin on human keratinocytes. Second-passage neonatal keratinocytes were grown in serum-free keratinocyte growth medium, and the effect of heparin analogs was studied in the absence of exogenous growth factors using keratinocyte-conditioned medium. Cell proliferation was assessed by measurement of both DNA content and [3H]-thymidine incorporation. The addition of heparin inhibited the conditioned medium-stimulated keratinocyte proliferation in a dose-dependent manner, with 80% inhibition at or above 10 micrograms/ml. Moreover, heparin was not toxic to keratinocytes (as detected by propidium-iodide fluorescence and by retention of normal protein synthetic rate) and it did not induce terminal differentiation (as measured by cornified envelope formation). Furthermore, heparin stimulated protein secretion by keratinocytes without altering rates of protein synthesis. The growth-inhibitory effects of heparin oligosaccharides were directly proportional to their chain length. The hexasaccharide unit represented the minimum requirement for inhibition, whereas decasaccharide units demonstrated nearly equivalent growth inhibition to native heparin. Finally, two non-anticoagulant heparin analogs were equipotent with heparin in inhibiting autocrine-induced keratinocyte growth. These studies show that the growth-inhibitory activities of heparin are independent of the anticoagulant effects and that decasaccharides contain the optimal oligosaccharide chain length for the antiproliferative effect in human keratinocytes.

Chemical synthesis and biological activity of the EGF-like domain of heparin-binding epidermal growth factor-like growth factor (HB-EGF)

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a recently discovered member of the epidermal growth factor (EGF) family. This novel growth factor possesses the EGF-like domain in the carboxyl portion. In order to evaluate the biological function of the EGF-like domain in HB-EGF, human HB-EGF(44-86) corresponding to the EGF-like domain was synthesized by the solid-phase procedure using the Fmoc strategy. It was confirmed by amino acid microsequencing of cysteine-containing fragments derived from thermolytic digestion that the pattern of three disulfide bond pairings in synthetic HB-EGF(44-86) was consistent with that of EGF and transforming growth factor-alpha (TGF-alpha). The homogeneity of the synthetic peptide was confirmed by analytical RP-HPLC, amino acid analysis and fast atom bombardment mass spectrometer (FAB-MS). Compared with h-EGF, the EGF-like domain of human HB-EGF showed a comparable mitogenic activity in the proliferation of NIH/3T3 fibroblast cells. These results suggest that the EGF-like domain of human HB-EGF may play an important role in mitogenic activity.

Estradiol-17 beta stimulates proliferation of uterine epithelial cells cultured with stromal cells but not cultured separately

There is indirect evidence that the in vivo proliferative response of rodent uterine epithelium to estrogen requires interaction with the underlying stroma in pre- and post-pubescent animals. To examine this potential requirement directly, the proliferative response of epithelium to 17 beta-estradiol in the presence or absence of stroma was measured in vitro. Uterine epithelial and stromal cells were isolated separately from immature or adult mice, and were maintained as monocultures or cocultures in defined, serum-free medium with or without 8 x 10(-9) M 17 beta-estradiol. Incorporation of bromodeoxyuridine into the DNA was determined by immunolabeling to assay proliferation in individual cells. Cell morphology and immunolabeling of cytokeratin were used to distinguish epithelial from stromal cells. Treatment of cocultures with 17 beta-estradiol for 24 h increased the proliferation of epithelial cells relative to controls approximately threefold, whereas, in monocultures of epithelial or stromal cells 17 beta-estradiol decreased the number of bromodeoxyuridine-incorporating cells by approximately half. Furthermore, cell contact between epithelial and stromal cells was important for the effects of 17 beta-estradiol on cells in cocultures. Approximately three quarters of the 17 beta-estradiol-induced proliferation of epithelial cells in cocultures was produced by epithelial cells within colonies that were also contacting stromal cells. These results are consistent with the hypothesis that stromal cells mediate the estrogenic proliferative response, and provide evidence that this mediation involves cell contact or stroma-mediated changes in the microenvironment immediately around the epithelial cell.

Endothelial seeding of polytetrafluoroethylene femoral popliteal bypasses: the failure of low-density seeding to improve patency

PURPOSE

We compared 66 seeded polytetrafluoroethylene and 53 autologous vein grafts to determine whether endothelial seeding could improve the patency of polytetrafluoroethylene femoral popliteal bypass grafts and to determine whether endothelial seeding could be performed consistently in multiple institutions.

METHODS

Nine surgeons at four hospitals randomized patients to receive either a seeded polytetrafluoroethylene or a vein graft, but if no satisfactory vein (n = 26) existed, an "obligatory" seeded polytetrafluoroethylene graft was used.

RESULTS

Scanning electron microscopy confirmed satisfactory initial attachment of endothelium on the discarded ends of the grafts. Patency was compared with the use of log rank analysis and revealed better patency in vein grafts at 30 months (vein = 91.6% +/- 4.1%; seeded polytetrafluoroethylene = 37.8% +/- 9.4%; p = 0.006). Failed grafts revealed anastomotic hyperplasia.

CONCLUSIONS

(1) Vein graft patency was better than seeded polytetrafluoroethylene grafts; (2) seeding did not improve patency in below-the-knee bypasses as suggested by pilot studies; (3) the failure of seeded grafts was associated with anastomotic hyperplasia but not with the failure of initial endothelial attachment; and (4) each institution reported similar results.

Receptor blockade with monoclonal antibodies as anti-cancer therapy

Human tumors express high levels of growth factors and their receptors, and many types of malignant cells appear to exhibit autocrine- or paracrine-stimulated growth. Therefore, antireceptor directed therapies have the potential of being useful anti-cancer agents. A series of murine monoclonal antibodies (MAbs) directed against human growth factor receptors and their corresponding growth factors have been produced. MAbs against the receptors for epidermal growth factor, Her2/Neu, transferrin, insulin-like growth factor, interleukin, (IL)-2 and IL-1 are currently being evaluated. MAbs directed against epidermal growth factor, transforming growth factor-alpha, bombesin, IL-2, and IL-6 also are under study. These MAbs have shown promising preclinical activity, and some of them are being tested in clinical trials. So far, anti-tumor responses have been observed with anti-IL-2 receptor, anti-bombesin and anti-IL-6 MAbs. Further research is focusing in the production of "chimeric" and "humanized" MAbs, in order to obviate the problem of host immune reactions.

Effects of denervation upon receptor cell survival and basal cell proliferation in tuberous electroreceptor organs of a weakly electric fish

Weakly electric fish generate electric fields for the purposes of electrolocation and communication. These fields are detected by specialized receptor organs: the tuberous organs. In the present study we investigated the effects of denervation upon receptor cell survival and progenitor (basal) cell proliferation rate. The left, infraorbital, anterior lateral line nerve of brown ghosts (Apteronotus leptorhynchus) was sectioned, and the proximal stump was dipped in ricin to prevent regrowth. In groups of four, the animals were given two daily injections of the cell proliferation marker bromodeoxyuridine (BrdU) for 2 days at 1, 2, 3, or 4 weeks following denervation. At the completion of the BrdU injection schedule, a piece of cheek skin, rostroventral to the eye, was removed from the left (denervated) and the right (intact) sides and processed for light microscopy or immunocytochemistry. Our results show: (1) there is progressive receptor cell death and tuberous organ degeneration following denervation; (2) basal cell proliferation increases steadily with time after denervation and tuberous organ degeneration; and (3) despite denervation, some proliferating basal cells differentiate into receptor cells, but these new receptor cells eventually die. These results suggest that innervation is essential for tuberous electroreceptor cell survival and that the rate at which basal cells proliferate is regulated by receptor cell health, locally released factors, or both.

Activation of AT1 angiotensin receptors induces DNA synthesis in a rat intestinal epithelial (RIE-1) cell line

Proliferation of the rat intestinal epithelial cell-line, RIE-1, has previously been shown to be stimulated by certain polypeptide growth factors acting via receptors that possess intrinsic tyrosine kinase activity. In this study, we show that the octapeptide hormone angiotensin II (AII), apparently acting through the AT1 G-protein-coupled receptor, is also a mitogen for RIE-1 cells. Maximal stimulation of DNA synthesis and cellular proliferation occurred at an AII concentration of 10-100 nM, with half-maximal stimulation at 1 nM. The mitogenic response to AII was completely inhibited by the AT1 angiotensin-receptor antagonist, DuP753, but not by the AT2-receptor antagonist, PD123319. The early signalling responses activated by AII in RIE-1 cells include increased production of inositol phosphates, a transient increase in the intracellular concentration of free calcium, an activation of protein kinase C, and a rapid change in the pattern of cellular protein-tyrosine phosphorylation. These results implicate an activation of the inositol lipid signalling pathway via the AT1 receptor subtype in the AII-stimulated mitogenic response of this normal epithelial cell line.

Interaction of the small interstitial proteoglycans biglycan, decorin and fibromodulin with transforming growth factor beta

We have analysed the interactions of three proteoglycans of the decorin family, decorin, biglycan and fibromodulin, with transforming growth factor beta (TGF-beta). The proteoglycan core proteins, expressed from human cDNAs as fusion proteins with Escherichia coli maltose-binding protein, each bound TGF-beta 1. They showed only negligible binding to several other growth factors. Intact decorin, biglycan and fibromodulin isolated from bovine tissues competed with the fusion proteins for the TGF-beta binding. Affinity measurements suggest a two-site binding model with Kd values ranging from 1 to 20 nM for a high-affinity binding site and 50 to 200 nM for the lower-affinity binding site. The stoichiometry indicated that the high-affinity binding site was present in one of ten proteoglycan core molecules and that each molecule contained a low-affinity binding site. Tissue-derived biglycan and decorin were less effective competitors for TGF-beta binding than fibromodulin or the non-glycosylated fusion proteins; removal of the chondroitin/dermatan sulphate chains of decorin and biglycan (fibromodulin is a keratan sulphate proteoglycan) increased the activities of decorin and biglycan, suggesting that the glycosaminoglycan chains may hinder the interaction of the core proteins with TGF-beta. The fusion proteins competed for the binding of radiolabelled TGF-beta to Mv 1 Lu cells and endothelial cells. Affinity labelling showed that the binding of TGF-beta to betaglycan and the type-I receptors in Mv 1 Lu cells and to endoglin in endothelial cells was reduced, but the binding to the type-II receptors was unaffected. TGF-beta 2 and 3 also bound to all three fusion proteins. Latent recombinant TGF-beta 1 precursor bound slightly to fibromodulin and not at all to decorin and biglycan. The results show that the three decorin-type proteoglycans each bind TGF-beta isoforms and that slight differences exist in their binding properties. They may regulate TGF-beta activities by sequestering TGF-beta into extracellular matrix.

The heparin-binding domain of heparin-binding EGF-like growth factor can target Pseudomonas exotoxin to kill cells exclusively through heparan sulfate proteoglycans

Heparin-binding EGF-like growth factor (HB-EGF) is a smooth muscle cell mitogen composed of both EGF receptor and heparin-binding domains. To better understand the function of its domains, intact HB-EGF or its heparin-binding (HB) domain (amino acids 1-45) were fused to a mutant Pseudomonas exotoxin with an inactivated cell-binding domain. The resulting chimeric toxins, HB-EGF-PE* and HB-PE*, were tested on tumor cells, proliferating smooth muscle cells and a mutant Chinese hamster ovary cell line deficient in heparan sulfate proteoglycans (HSPGs). Two targets were found for HB-EGF-PE*. Cells were killed mainly through EGF receptors, but the HB domain was responsible for killing via HSPGs. HB-PE* did not bind to the EGF receptor and thus was cytotoxic by interacting exclusively with HSPGs. We conclude that the HB domain of HB-EGF is able to mediate internalization through HSPGs, without requiring the EGF receptor.

Induction of heparin-binding epidermal growth factor-like growth factor mRNA by protein kinase C activators

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a potent smooth muscle cell mitogen of macrophage origin. To determine whether the HB-EGF gene is transcribed and regulated in mesangial cells, we measured HB-EGF mRNA levels in cultured rat mesangial cells by RNA blot analysis. A 2.5-kb HB-EGF mRNA was detected in unstimulated mesangial cells. The protein kinase C activator 12-O-tetradecanoylphorbol 13-acetate (TPA) increased HB-EGF mRNA levels by 15-fold in mesangial cells, and this induction of HB-EGF mRNA by TPA was both time- and dose-dependent. HB-EGF mRNA could also be stimulated by 10% fetal calf serum, ionomycin, thrombin, and endothelin-1. Staurosporine, a protein kinase C inhibitor, abolished the induction of HB-EGF mRNA by TPA and serum. To determine whether HB-EGF is mitogenic for mesangial cells, we transfected COS cells with HB-EGF expression plasmids. Culture medium from COS cells transfected with these plasmids increased 3H-thymidine incorporation in mesangial cells in a dose-dependent manner. To our knowledge, this is the first report that HB-EGF is expressed in renal cells. This inducible transcription of HB-EGF suggests that it may have an autocrine role in mesangial cell proliferation in kidney disease.

Epidermal growth factor receptor expression by human squamous cell carcinomas of the head and neck, cell lines and xenografts

Epidermal growth factor receptor (EGFR) overexpression has been associated frequently with squamous cell carcinomas (SCC) and SCC cell lines. In most cases the level of EGFR on the tumours from which the cell lines were derived has not been determined, nor have EGFR levels been determined for xenograft tumours from the cell lines. In this study we determined EGFR expression on a new series of head and neck SCC (SCCHN)-derived cell lines, which were obtained from tumours representing a spectrum of malignant progression, and two cell strains derived from erythroplakia premalignant lesions. The level of EGFR on cell lines was determined by [125I]EGF competitive binding assays. EGFR levels on some of the original tumours and xenografts of the cell lines were determined on cryosections by a competitive binding assay based on [125I]EGFR1, an EGFR-specific monoclonal antibody. EGFR expression on the tumour cryosections was compared with expression on cryosections of skin and buccal mucosa. Eight of the ten tumour cell lines had elevated EGFR. Two of the tumour-derived cell lines and the two erythroplakia-derived cell strains expressed EGFR at levels similar to that detected on normal keratinocytes in tissue culture. Only two of the tumours overexpressed EGFR when compared with normal tissue. The other tumours had levels similar to that detected on the basal layers of skin or buccal mucosa. The xenografts expressed EGFR, as did the original tumours, even though they were derived from cell lines that displayed significant overexpression of EGFR. This study suggests that most tumours have a latent potential to overexpress EGFR which is realised in tissue culture.

Structural characterization and alternate splicing of the gene encoding the preadipocyte EGF-like protein pref-1

Preadipocyte factor 1 (pref-1), a member of the EGF-like protein family, is a transmembrane protein with six tandem EGF-like repeats in the putative extracellular domain. Expression of pref-1 is abolished during the in vitro differentiation of 3T3-L1 preadipocytes to adipocytes, and constitutive expression of pref-1 in preadipocytes inhibits their differentiation [Smas, C.M., & Sul, H.S. (1993) Cell 73, 725-734]. In the present studies, we have isolated and characterized genomic clones for pref-1 and have identified multiple pref-1 transcripts generated by alternate splicing. The pref-1 gene consists of five exons and four introns spanning approximately 7.3 kb. By primer extension analysis, the transcription start site was determined to be 169 bp upstream from the translation initiation codon. We have identified functional promoter sequences by transient transfection using a 2.1 kb fragment of the pref-1 5' flanking region linked to a luciferase gene; the pref-1-luciferase fusion gene construct gave 20-fold higher promoter activity as compared to the promoterless vector. Analysis of exon-intron junctions reveals that unlike the majority of the mammalian EGF-like genes, EGF-like repeats of pref-1 are not encoded by discrete exons. Through RT-PCR and the isolation and analysis of multiple pref-1 cDNA clones, we have identified, in addition to full-length pref-1, five alternately spliced forms with various in-frame deletions of all or a part of the sixth EGF-like repeat, juxta-membrane, and predicted transmembrane domains.(ABSTRACT TRUNCATED AT 250 WORDS)

Contribution of host-derived growth factors to in vivo growth of a transplantable murine mammary carcinoma

The contribution of host-derived growth factors to tumour growth in vivo was studied using the transplantable murine mammary carcinoma, MT1, grown in syngeneic mice. Promotion of growth of the mammary carcinoma by a factor(s) from the host was evident in experiments in which the carcinoma cells were inoculated intraperitoneally. In this environment, tumours develop as multiple solid nodules, each probably arising from an individual cell or a small cluster of cells. Tumour growth was found to occur in the peritoneal cavity following inoculation of 10(3) cells, but an inoculum of as few as ten cells grew if a leucocyte-rich exudate had first been induced. To determine which host-derived growth factors might contribute to growth of MT1, extracts of the tumour were first examined for growth factor activity. Fractionation of tumour extracts by either ion-exchange chromatography or gel filtration revealed several peaks of mitogenic activity, but none of this could be attributed to epidermal growth factor (EGF). Accordingly, an anti-EGF antibody was tested as a putative inhibitor of tumour growth as any effect of this antibody could be ascribed to removal of EGF derived from the host. The antibody was found to have potent anti-tumour activity when tested against MT1 tumours that had been inoculated into the peritoneal cavity. In contrast, the antibody had little effect on growth of the discrete tumour mass which formed when MT1 was transplanted subcutaneously. The results suggest that host-derived EGF contributes to establishment of microcolonies of MT1 carcinoma within the peritoneal cavity. This may be directly, by providing growth factors to supplement those produced by the tumour until it reaches a certain critical mass to sustain autocrine growth, or indirectly, by affecting the production of other growth-stimulatory factors or cytokines.

Growth-promoting effect of bacterial products from Clostridium perfringens on human keratinocytes

Wound healing substance (WHS) from cultured Clostridium perfringens has been reported to be effective in the treatment of wounds. The effects of WHS, now named SNK-863, on proliferation and differentiation of human keratinocytes were examined. The characteristics of WHS are as follows: 1) WHS stimulates human keratinocyte growth and DNA synthesis; 2) WHS and EGF show some additive effects on human keratinocyte growth; 3) WHS does not interfere with the binding of EGF to its receptor; 4) WHS does not counteract the growth inhibitory effects of TGF-beta or vitamin D3 on human keratinocytes; 5) WHS has no significant effect on human keratinocyte differentiation. These results indicate that the growth-promoting effect of WHS on keratinocytes may contribute to the treatment of wound healing.

Identification of epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor in surgically induced pelvic adhesions in the rat and intraperitoneal adhesions in the human

OBJECTIVE

Our purpose was to determine the presence and cellular distribution of epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor in surgically induced pelvic fibrous adhesions in rat uterine horns subjected to burn, crush, and debridement injury and intraperitoneal fibrous adhesions formed to various organs in the human.

STUDY DESIGN

A total of 15 injured and five uninjured rats were used in this study, and fibrous adhesions and intact peritoneum were removed for processing 2 weeks after surgery. Fibrous adhesions formed to uterine, ovarian, and oviductal tissues and the peritoneal wall from eight patients who had gynecologic surgery were also collected. The tissues were processed for immunohistochemical localization of epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor with specific antibodies to human and rat epidermal growth factor and transforming growth factor-alpha and the extracellular binding domain of the epidermal growth factor receptor.

RESULTS

All the cell types in the rat fibrous adhesion immunostained for epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor. The highest immunostaining intensity for epidermal growth factor was associated with inflammatory cells infiltrated into the fibrous adhesion, followed by arteriole endothelial and smooth muscle cells, fascial striated muscle, and fibroblasts of the fibrous adhesion. In the uterine tissue at the site of injuries myometrial smooth muscle cells, in addition to inflammatory cells that migrated among stromal cells, also immunostained for epidermal growth factor. Fibrous adhesions also immunostained for transforming growth factor-alpha with three separate polyclonal antibodies to the amino and carboxy termini of transforming growth factor-alpha precursor and the mature transforming growth factor-alpha, with no substantial differences in their intensity and pattern compared with epidermal growth factor. The pattern and cellular distribution of epidermal growth factor receptor was similar to that seen for epidermal growth factor and transforming growth factor-alpha. Fibrous adhesions from patients with intraperitoneal adhesions immunostained for epidermal growth factor, transforming growth factor-alpha, and epidermal growth factor receptor with a pattern and intensity similar to that observed in fibrous adhesions in the rats.

CONCLUSIONS

The data suggest that epidermal growth factor and transforming growth factor-alpha may play a key role both in normal mechanism of peritoneal repair after injury and formation and maintenance of fibrous adhesions.

NDF/heregulin stimulates the phosphorylation of Her3/erbB3

Her3/erbB3 has been identified as a third member of the epidermal growth factor receptor (EGFR) family [(1989) Proc. Natl. Acad. Sci. USA 86, 9193-9197; (1990) Proc. Natl. Acad. Sci. USA 87, 4905-4909]. The natural ligand for Her3 has not been identified. Although recently NDF has been proposed as a specific ligand for Her4 [(1993) Nature 366, 473-475; (1993) J. Biol. Chem. 268, 18407-18410], we report here that Her3 was phosphorylated on tyrosine not only in three breast carcinoma cell lines, MDAMB453, MDAMB468 and SKBR3, but also in Her3-transfected CHO cells in response to NDF stimulation. In further studies, cells were reacted with 125I-labeled NDF and then chemically crosslinked. Immunoprecipitation with anti-Her3 revealed a dense high Mw band, greater than 400 kDa. The results suggest that NDF may be a ligand of Her3 and induces receptor hetero-oligomerization.

Pathophysiology of glial growth factor receptors

Activation and proliferation of glial cells are common events in the pathology of the nervous system. Although we are only beginning to understand the molecular signals leading to glial activation in vivo, there is increasing evidence that growth factors and their receptors may play an important part. In this paper we summarize the data on the pathophysiology of glial growth factor receptors and their ligands in the central and peripheral nervous systems.

Association of the transmembrane TGF-alpha precursor with a protein kinase complex

A variety of growth factors including transforming growth factor-alpha (TGF-alpha) are synthesized as transmembrane precursors. The short cytoplasmic domain of the transmembrane TGF-alpha precursor lacks any apparent motif associated with signal transduction. However, the sequence conservation of this cytoplasmic domain and its abundance of cysteine residues, reminiscent of the cytoplasmic domains of CD4 and CD8, suggest a biological function. In this study, we showed that transmembrane TGF-alpha was rapidly internalized after interaction with a specific antibody and that this internalization was greatly decreased when the COOH-terminal 31 amino acids were removed. Chemical cross-linking experiments revealed two associated proteins of 86 and 106 kD which coimmunoprecipitated with the TGF-alpha precursor. The association of p86 was dependent on the presence of the COOH-terminal cytoplasmic 31 amino acids of the TGF-alpha precursor, whereas p106 still remained associated when this segment was deleted. In addition, p106 was tyrosine-phosphorylated and exposed on the cell surface. The protein complex associated with transmembrane TGF-alpha displayed kinase activities towards tyrosine, serine, and threonine residues. These activities were not associated with transmembrane TGF-alpha when the COOH-terminal segment was truncated. The association of a protein kinase complex with transmembrane TGF-alpha may provide the basic elements for a "reverse" mode of signaling through the cytoplasmic domain of this growth factor, which may lead to two-directional communication during ligand-receptor interaction.

Heparin-binding EGF-like growth factor gene is induced in the mouse uterus temporally by the blastocyst solely at the site of its apposition: a possible ligand for interaction with blastocyst EGF-receptor in implantation

Heparin-binding EGF-like growth factor (HB-EGF) is a newly discovered member of the EGF family of growth factors. HB-EGF can bind to two loci on cell surfaces, heparan sulphate proteoglycans and EGF-receptor (EGF-R), and either one or both of these interactions could play a role in cell-cell interactions. In the rodent, increased endometrial vascular permeability at the site of blastocyst apposition is considered to be an earliest discernible prerequisite event in the process of implantation and this event coincides with the initial attachment reaction between the blastocyst trophectoderm and uterine luminal epithelium. This investigation demonstrates that the HB-EGF gene is expressed in the mouse uterine luminal epithelium surrounding the blastocyst 6–7 hours before the attachment reaction that occurs at 2200–2300 hours on day 4 of pregnancy. It was further demonstrated that this gene is not expressed in the luminal epithelium at the site of the blastocyst apposition during the progesterone-maintained delayed implantation, but is readily induced in the luminal epithelium surrounding an activated blastocyst after termination of the delay by an estrogen injection. In vitro studies showed that HB-EGF induced blastocyst EGF-R autophosphorylation, and promoted blastocyst growth, zona-hatching and trophoblast outgrowth. These results suggest possible interactions between the uterine HB-EGF and blastocyst EGF-R very early in the process of implantation, earlier than any other embryo-uterine interactions defined to date at the molecular level.

The basis of molecular strategies for treating coronary restenosis after angioplasty

Excessive smooth muscle cell proliferation significantly contributes to restenosis, which occurs in 25% to 50% of patients within 6 months of coronary angioplasty. Because successful treatment will probably depend on our acquiring a comprehensive knowledge of the molecular and cellular mechanisms involved, this report reviews 1) information relevant to the molecular and cellular mechanisms responsible for the smooth muscle cell(s) response to vascular injury, and 2) several molecular-based therapeutic strategies currently being explored as possible approaches to the control of restenosis, including recombinant DNA technology to target delivery of cytotoxic molecules to proliferating smooth muscle cell(s), antisense strategies to inhibit expression of gene products necessary for cell proliferation and gene therapy.

T lymphocytes synthesize and export heparin-binding epidermal growth factor-like growth factor and basic fibroblast growth factor, mitogens for vascular cells and fibroblasts: differential production and release by CD4+ and CD8+ T cells

T lymphocytes infiltrate wounds, tumors, and atherosclerotic plaques, pathophysiological processes characterized by the migration and proliferation of vascular cells and fibroblasts. Although T lymphocytes are known to produce cytokines for inflammatory cells, it has not been demonstrated that they synthesize growth factors that are mitogenic for vascular cells and fibroblasts. We demonstrate that cultured T lymphocytes isolated from normal human peripheral blood synthesize and export two well-characterized growth factors, heparin-binding epidermal growth factor-like growth factor (HB-EGF) and basic fibroblast growth factor (bFGF). This conclusion is based on mRNA expression analysis, heparin-affinity chromatography profiles, target-cell specificity, and functional inhibition by specific neutralizing antibodies. Atypically, a substantial amount of T-cell-derived bFGF-like activity appears to be constitutively released into conditioned medium, almost as much as is associated with T-cell lysates. bFGF is synthesized and exported by purified CD4+ and CD8+ T cells, whereas HB-EGF is synthesized and exported primarily by CD4+ T cells. The T-cell-derived HB-EGF and bFGF activities are potent mitogens for fibroblasts and smooth muscle cells, and the bFGF-like activity is also mitogenic for endothelial cells. These results suggest that T lymphocytes may play key roles in mediating smooth muscle hyperplasia associated with atherosclerosis and in angiogenesis associated with wound healing and tumor growth by acting locally to deliver vascular-cell growth factors to tissues.

Protection of transforming growth factor-beta 1 activity by heparin and fucoidan

The transforming growth factor-beta (TGF-beta) family of proteins exert diverse and potent effects on proliferation, differentiation, and extracellular matrix synthesis. However, relatively little is known about the stability or processing of endogenous TGF-beta activity in vitro or in vivo. Our previous work indicated that 1) TGF-beta 1 has strong heparin-binding properties that were not previously recognized because of neutralization by iodination, and 2) heparin, and certain other polyanions, could block the binding of TGF-beta 1 to alpha 2-macroglobulin (alpha 2-M). The present studies investigated the influence of heparin-like molecules on the stability of the TGF-beta 1 signal in the pericellular environment. The results indicate that heparin and fucoidan, a naturally occurring sulfated L-fucose polymer, suppress the formation of an initial non-covalent interaction between 125I-TGF-beta 1 and activated alpha 2-M. Electrophoresis of 125I-TGF-beta 1 showed that fucoidan protects TGF-beta 1 from proteolytic degradation by plasmin and trypsin. While plasmin caused little, if any, activation of latent TGF-beta derived from vascular smooth muscle cells (SMC), plasmin degraded acid-activated TGF-beta, and purified TGF-beta 1, and this degradation was inhibited by fucoidan. In vitro, heparin and fucoidan tripled the half-life of 125I-TGF-beta 1 and doubled the amount of cell-associated 125I-TGF-beta 1. Consistent with this protective effect, heparin- and fucoidan-treated SMC demonstrated elevated levels of active, but not latent, TGF-beta activity.

The heparin-binding domain of amphiregulin necessitates the precursor pro-region for growth factor secretion

The five members of the human epidermal growth factor (EGF) family (EGF, transforming growth factor alpha [TGF-alpha], heparin-binding EGF-like growth factor [HB-EGF], betacellulin, and amphiregulin [AR]) are synthesized as transmembrane proteins whose extracellular domains are proteolytically processed to release the biologically active mature growth factors. These factors all activate the EGF receptor, but in contrast to EGF and TGF-alpha, the mature forms of HB-EGF and AR are also glycosylated, heparin-binding proteins. We have constructed a series of mutants to examine the influence of the distinct precursor domains in the biosynthesis of AR. The transmembrane and cytoplasmic domains of the precursor are not required for secretion of bioactive AR from either COS or mammary epithelium-derived cells, although proteolytic removal of the N-terminal pro-region is less efficient in the absence of the membrane anchor. Deletion of the N-terminal pro-region, however, results in rapid intracellular degradation of the molecule with no detectable secretion of active growth factor. AR secretion is preserved by replacing the native pro-region with the corresponding domain of the HB-EGF precursor but not with that of the TGF-alpha precursor. In the absence of any N-terminal pro-region, secretion of the molecule is restored by deleting the N-terminal heparin-binding domain of mature AR. Both EGF and TGF-alpha, in contrast, can be secreted without their pro-regions. However, if the protein is fused with the AR heparin-binding domain, TGF-alpha secretion is inhibited unless the AR pro-region is also present. We propose that the heparin-binding domain of mature AR necessitates the presence of a specific structural motif in an N-terminal pro-region to permit proper folding, and thus secretion, of a bioactive molecule.

The heparin-binding domain of amphiregulin necessitates the precursor pro-region for growth factor secretion

The five members of the human epidermal growth factor (EGF) family (EGF, transforming growth factor alpha [TGF-alpha], heparin-binding EGF-like growth factor [HB-EGF], betacellulin, and amphiregulin [AR]) are synthesized as transmembrane proteins whose extracellular domains are proteolytically processed to release the biologically active mature growth factors. These factors all activate the EGF receptor, but in contrast to EGF and TGF-alpha, the mature forms of HB-EGF and AR are also glycosylated, heparin-binding proteins. We have constructed a series of mutants to examine the influence of the distinct precursor domains in the biosynthesis of AR. The transmembrane and cytoplasmic domains of the precursor are not required for secretion of bioactive AR from either COS or mammary epithelium-derived cells, although proteolytic removal of the N-terminal pro-region is less efficient in the absence of the membrane anchor. Deletion of the N-terminal pro-region, however, results in rapid intracellular degradation of the molecule with no detectable secretion of active growth factor. AR secretion is preserved by replacing the native pro-region with the corresponding domain of the HB-EGF precursor but not with that of the TGF-alpha precursor. In the absence of any N-terminal pro-region, secretion of the molecule is restored by deleting the N-terminal heparin-binding domain of mature AR. Both EGF and TGF-alpha, in contrast, can be secreted without their pro-regions. However, if the protein is fused with the AR heparin-binding domain, TGF-alpha secretion is inhibited unless the AR pro-region is also present. We propose that the heparin-binding domain of mature AR necessitates the presence of a specific structural motif in an N-terminal pro-region to permit proper folding, and thus secretion, of a bioactive molecule.

The mouse waved-2 phenotype results from a point mutation in the EGF receptor tyrosine kinase

Mice harboring the waved-1 (wa-1) and waved-2 (wa-2) mutations exhibit skin and eye abnormalities that are strikingly similar to those of TGF-alpha-deficient mice, and wa-1 and TGF-alpha were recently shown to be allelic. Because the wa-2 mutation was mapped previously to the vicinity of the EGF/TGF-alpha receptor (EGFR) gene on mouse chromosome 11, we hypothesized that the wa-2 phenotype might result from a defect in either the expression or activity of EGFR, or both. In the present report, we show that EGFR mRNA and protein of normal size are expressed in wa-2 liver and skin at levels that are comparable to those in the corresponding normal tissues, and that the ability of wa-2 EGFR to bind ligand is unaltered. However, ligand-dependent autophosphorylation of wa-2 EGFR is diminished 5- to 10-fold in vitro, and the ability of wa-2 EGFR to phosphorylate an exogenous substrate is reduced by > 90% compared with that of the control receptor. EGF-induced tyrosine phosphorylation, including that of EGFR itself, is also diminished in skin, particularly at lower dose of exogenous EGF. To establish the nature of the wa-2 mutation, we determined the nucleotide sequence of the coding region of normal and wa-2 murine EGFR cDNAs. A comparison of these sequences revealed a single-nucleotide transversion resulting in the substitution of a glycine for a conserved valine residue near the amino terminus of the tyrosine kinase domain. The importance of this mutation was confirmed by showing that its introduction into an otherwise normal EGFR markedly reduced the receptor's tyrosine kinase activity in transfected Chinese hamster ovary cells. Finally, in situ hybridization analysis demonstrated expression of EGFR predominantly in the outer root sheath of active hair follicles in neonatal mice. As we previously localized TGF-alpha mRNA to the inner root sheath, this pattern of EGFR expression is consistent with the effect of the wa-2 mutation on hair structure, and together with our previous characterization of TGF-alpha-deficient mice, reveals a critical role for signaling by this ligand/receptor system in skin.

Lysophosphatidylcholine transcriptionally induces growth factor gene expression in cultured human endothelial cells

Lysophosphatidylcholine (lyso-PC) is a major phospholipid component of atherogenic lipoproteins (e.g., oxidized LDL and beta-VLDL) and also can be generated through the action of leukocyte-secreted phospholipase A2 at sites of inflammation. We have previously reported that lyso-PC can activate cultured endothelia, resulting in the selective upregulation of adhesion molecules, such as vascular cell adhesion molecule-1 and intercellular adhesion molecule-1. In this study, we have found that lyso-PC increased steady state mRNA levels for two smooth muscle/fibroblast-directed growth factors, the A and B chains of PDGF and heparin-binding EGF-like protein (HB-EGF), in cultured human endothelial cells. Lyso-PC did not upregulate the expression of certain other inducible endothelial genes, including E-selectin, IL-8, or monocyte chemoattractant protein-1 in the same cells, in contrast to the coordinate pattern of activation typically observed with other stimuli, such as TNF alpha, bacterial endotoxin, or PMA. Nuclear runoff assays documented an increased transcriptional rate for the HB-EGF gene in lyso-PC-treated cells. Northern blot analyses, after actinomycin D treatment, further indicated that the increased amounts of mRNA for HB-EGF, PDGF A and B chains, and intercellular adhesion molecule-1 were not dependent upon message stabilization. We conclude that lyso-PC can induce growth factor gene expression in cultured endothelial cells and thus may contribute to the migration and proliferation of smooth muscle cells and fibroblasts in various response-to-injury settings in vivo.

Lysophosphatidylcholine upregulates the level of heparin-binding epidermal growth factor-like growth factor mRNA in human monocytes

Lysophosphatidylcholine is increased in the plasma of hypercholesterolemic patients, is a component of oxidatively modified low-density lipoprotein, and, as such, may play an important role in atherosclerosis. Here we demonstrate that in human monocytes, lysophosphatidylcholine increases the level of mRNA encoding the heparin-binding epidermal growth factor-like growth factor (HB-EGF), a potent smooth muscle mitogen. Lysophosphatidylcholine treatment also enhances the release of heparin-binding mitogenic activity by these cells in culture. The anti-inflammatory glucocorticoid dexamethasone inhibits the upregulation of HB-EGF mRNA induced by either lysophosphatidylcholine or bacterial lipopolysaccharide in cultured monocytes. However, the responses induced by lysophosphatidylcholine and by lipopolysaccharide differ in their kinetics. In addition, the response to lysophosphatidylcholine is resistant to the action of cycloheximide, whereas the response to lipopolysaccharide is not, suggesting that the activation mechanisms induced by these two stimuli are different. Since a nuclear run-on assay showed no effect of lysophosphatidylcholine on the transcription of the HB-EGF gene, we speculate that lysophosphatidylcholine may increase the level of HB-EGF mRNA by altering the processing or degradation of primary or mature transcripts. Lysophosphatidylcholine enhancement of monocyte production of HB-EGF may represent an important result of the interactions among oxidized low-density lipoprotein and monocyte-derived macrophages and may play a role in initiation of smooth muscle proliferation in atherogenesis.

Follicular development, oocyte viability and recovery in relation to follicular steroids, prolactin and glycosaminoglycans throughout the estrous period in superovulated heifers with a normal LH surge, no detectable LH surge, and progestin inhibition of LH surge

Estrous cycles of heifers (n = 137) were synchronized with prostaglandin (PGF2 alpha) and follicular development stimulated with follicle stimulating hormone. Twenty-eight animals were administered Norgestomet implants 12 hr prior to the initial PGF2 alpha injection to suppress the LH surge that initiates ovulation. Animals were ovariectomized every 12 hr after the initial PGF2 alpha (7-9/time, 12-108 hr and at 192 and 240 hr post PGF2 alpha) and divided into three treatment groups to consist of: 1) animals exhibiting a normal luteinizing hormone (LH) surge (n = 86), 2) animals in which no LH surge was detected (n = 23), and 3) suppression of the LH surge via Norgestomet implants (72-108 hr, n = 28). Follicular diameter was measured and follicular fluid was collected for analysis of prolactin, estradiol, progesterone and glycosaminoglycan concentrations. Progesterone concentrations were increased in animals exhibiting an LH surge as compared to animals in which no LH surge was detected; primarily in large follicles (> 8 mm diameter) after the LH surge. Animals not exhibiting an LH surge also had increased follicular progesterone concentrations compared to Norgestomet-implanted animals (242.3 +/- 36.3 vs 86.7 +/- 6.4 ng/ml, respectively, P < .01), indicating some LH stimulation. Follicular estradiol in animals exhibiting an LH surge increased up to the time of LH surge detection and then declined whereas animals with no LH surge detected had follicular estradiol concentrations that declined after the PGF2 alpha injection. No differences were noted between those that did not exhibit an LH surge or in which the LH surge was suppressed with Norgestomet in relation to follicular estradiol concentrations. Follicular estradiol concentrations increased with follicular size in all treatment groups (P < .01). Follicular concentrations of prolactin were increased in small follicles (P < .05; < or = 4 mm diameter) and follicular prolactin increased from 12 to 36 hr post PGF2 alpha injection, then declined after the LH surge. Follicular glycosaminoglycan concentrations decreased with increases in follicular size (P < .01) and were higher in animals that did not exhibit an LH surge (P < .01). No differences in follicular glycosaminoglycans were noted between Norgestomet-implanted animals and those not exhibiting an LH surge. In the animals representing days 4 and 6 of the subsequent estrous cycle (192 and 240 hr post PGF2 alpha), numbers of small-sized follicles were increased. Follicular progesterone and estradiol concentrations were related to atretic large follicles unovulated from the prior estrus and a new wave of growth in small and medium follicles.(ABSTRACT TRUNCATED AT 400 WORDS)

The epidermal growth factor receptor as a target for therapy in breast carcinoma

The epidermal growth factor (EGF) receptor and its ligands have an important regulatory role in breast carcinoma. We have produced a series of monoclonal antibodies (MAbs) directed against the external portion of the EGF receptor. These MAbs prevent the binding of the ligands to the receptor, block ligand-induced activation of the receptor, and can inhibit the growth of breast cancer cells both in tissue culture and in human tumor xenografts in nude mice. We have also shown that anti-EGF receptor antibodies greatly enhance the antitumor effects of chemotherapeutic agents active in breast cancer. Phase I clinical trials with single doses of MAb conducted in patients with tumors over-expressing EGF receptors demonstrated favorable pharmacokinetics, good tumor imaging, and a lack of toxicity. A human:murine chimeric antibody has been produced with comparable affinity and antitumor activity that will enable us to administer repeated doses of MAb either alone or in combination with chemotherapy. Our pre-clinical data support the concept that the EGF receptor may be an optimal target for treatment with receptor blocking antibodies, either alone or in combination with chemotherapy.

Growth factor targeted and conventional therapy of breast cancer

Sustained breast cancer growth and metastasis requires paracrine signals between the tumor cells and the normal surrounding host tissue. One crucial function of these signals is to recruit endothelial cells and thus new blood vessels for the nourishment of the expanding tumor mass. This proliferation and migration of endothelial cells in the vicinity of progressing tumors contrasts with the extremely low turn-over rate of endothelial cells in the healthy adult. A blockade of tumor-induced endothelial cell proliferation should inhibit tumor growth and potentially metastasis with only few adverse effects. Different therapeutic approaches that take advantage of this situation are discussed with respect to their interaction with conventional therapies of breast cancer.