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

Possible role of transforming growth factor alpha in the pathogenesis of Ménétrier's disease: supportive evidence form humans and transgenic mice

Ménétrier's disease is an uncommon disorder of unknown etiology characterized by enlarged gastric folds with foveolar hyperplasia and cystic dilatation of gastric glands. Biochemical features that are seen frequently include hypoproteinemia, hypochlorhydria, and increased gastric mucus. Because transforming growth factor alpha (TGF alpha) is an epithelial cell mitogen that inhibits gastric acid secretion and increases gastric mucin content, we hypothesized that its altered expression might be involved in the pathogenesis of this disease. Therefore, we characterized TGF alpha immunoreactivity in the gastric mucosa of 4 patients with Ménétrier's disease. In contrast to the normal pattern of TGF alpha immunostaining in which TGF alpha appears most concentrated in parietal cells, there was intense staining in the majority of mucous cells in the gastric mucosa of patients with Ménétrier's disease. In one patient from whom sufficient fresh tissue was obtained to isolate RNA, expression of TGF alpha and the epidermal growth factor receptor was higher in the gastric mucosa relative to a normal control. In addition, metallothionein-TGF alpha transgenic mice, which overexpress TGF alpha in gastric mucosa, show a number of features characteristic of Ménétrier's disease. These include foveolar hyperplasia and glandular cystic dilatation, increased gastric neutral mucin staining, and reduced basal and histamine-stimulated rates of acid production. Taken together, observations derived from the human material and correlation with data from a transgenic mouse model support an important role for TGF alpha in the pathogenesis of Ménétrier's disease.

Transforming growth factor alpha receptor binding sites in the canine gastrointestinal tract

Transforming growth factor alpha (TGF-alpha) interacts with the same plasma membrane receptor as epidermal growth factor and is likely to play a role in proliferative and trophic processes of gastrointestinal tissues. The distribution of receptor binding sites for TGF-alpha was examined in the canine gastrointestinal tract (distal esophagus, stomach fundus, descending duodenum, jejunum, ileum, transverse colon) by tissue section autoradiography. 125I-TGF-alpha yielded a labeling pattern comparable to that of 125I-epidermal growth factor. Specific binding sites were particularly abundant in the mucosa in each region, with the highest concentration in the esophagus, colon, and stomach, as assessed by computer assisted densitometry. The density of binding sites was moderate in the stomach muscularis mucosae, low in the external muscle layer, and very low to undetectable in the submucosa throughout the gastrointestinal tract. In most cases, the greatest density within the individual regions was detected in the area characterized by the highest proliferative rate. Lymphoid aggregates were not labeled. In conclusion, TGF-alpha receptor binding sites are present throughout the gastrointestinal tract with differential patterns in the various regions; they are principally distributed to the mucosa and predominantly located to proliferative cell areas. These results are consistent with a role of this factor in regional regulation of proliferation and differentiation in the gut.

Quantitative determination of EGF-R during epidermal wound healing

Little is known about the intrinsic regulation of growth factors of cytokines during the normal epidermal wound-healing processes in skin. A simplified model of wounding (tape stripping to remove the stratum corneum) was used to study the role of epidermal growth factor receptors (EGF-R) in this process. Although the dynamics of EGF-R in epidermal wound healing have not been determined, the immunoreactive EGF-R that are present presumably play an active role. Prior studies show that 1) EGF-R are present in increased numbers in proliferative skin diseases; 2) a hypertrophic epidermis, closely resembling normal wound healing, is induced in mouse skin by EGF injections; and 3) exogenous topical EGF potentiates wound healing. The number of immunoreactive receptors as measured by an enzyme-linked immunosorbent assay (ELISA) and histologic methods increased prior to an increase in epidermal thickness, total protein, and DNA content. This early increase in the levels of EGF-R was followed by a sharp decline in EGF-R and subsequent decline in epidermal thickness (hypertrophy), total protein, and DNA levels. Alterations in the temporal sequence in these parameters indicate that the EGF-R-mediated signaling systems play an active role in epidermal wound repair.

The growth regulation of keratinocytes

Taken together, all these results suggest that TGF-alpha and amphiregulin are the major growth factors for positive growth control, although we don't know which plays the central role. For negative growth control, TGF-beta is the major factor. However, it remains to be solved which isoform of TGF-beta is naturally involved in keratinocyte growth regulation.

Tissue distribution of mRNA for heparin-binding epidermal growth factor

Heparin-binding epidermal growth factor (HB-EGF) is a recently identified member of the EGF family. Mature HB-EGF is processed from a larger transmembrane precursor which can itself act as a cell-surface receptor for the internalization of diphtheria toxin into eukaryotic cells. However, to date there is no information available on the distribution of HB-EGF in mammalian tissues. We have therefore used reverse-transcription PCR to analyse the expression of HB-EGF mRNA in a wide range of tissues. HB-EGF transcripts were detected in RNA isolated from 15 of the 22 tissues obtained from adult pigs, which is consistent with the ability of diphtheria toxin to affect many body tissues.

The type 1 (EGFR-related) family of growth factor receptors and their ligands

This review considers the biology of the type 1 growth factor receptor family which is increasingly recognised as important in the control of normal cell proliferation and in the pathogenesis of human cancer. The family currently comprises three closely related members: the epidermal growth factor (EGF) receptor, c-erbB-2 and c-erbB-3, all of which show abnormalities of expression in various human tumours. The family of factors related to EGF has also expanded recently and now includes transforming growth factor alpha, heparin-binding EGF, amphiregulin, cripto and heregulin, as well as several other potential ligands for the c-erbB2-2 receptor. The involvement of these receptors and growth factors in human cancer has implications for the design of novel forms of therapy for cancer, and we review recent advances and future avenues for investigation.

Capillary endothelial cells secrete a heparin-binding mitogen for pericytes

The cells of the retinal microvasculature consist predominantly of mesodermally derived pericytes and endothelial cells, and the regulatory factors which govern their co-ordinated growth and define their phenotypic characteristics in vivo may be regarded as key elements of the angiogenic process. An investigation of these cells in co-culture experiments has led to the identification of a potent mitogen for pericytes in medium conditioned by retinal endothelial cells (EC-FBS). EC-FBS activity was shown to be non-dialyzable, and stable to both heat and acid treatment. EC-FBS was inactivated by passage over a heparin-Agarose column. The column-bound activity could be eluted as a single peak at approximately 1.0 M NaCl. Stimulation of pericyte growth was also achieved with platelet-derived growth factor (PDGF), acidic fibroblast growth factor (aFGF) and basic fibroblast growth factor (bFGF) and could be blocked by using the appropriate antiserum (anti-PDGF or anti-aFGF). Neither antisera, however, blocked the activity of EC-FBS. The EC-FBS mitogen markedly altered the phenotypic behavior of pericytes compared with PDGF and the FGFs; yet, unlike them, it failed to stimulate the growth of smooth muscle cells (SMC) and Balb/c 3T3 cells.

Heparin inhibition of autonomous growth implicates amphiregulin as an autocrine growth factor for normal human mammary epithelial cells

Normal human mammary epithelial cells (HMECs) proliferate in a serum-free defined growth medium in the absence of epidermal growth factor (Li and Shipley, 1991). Amphiregulin (AR) is a heparin-regulated, EGF-like growth factor. Our observation that one strain of HMECs produce AR mRNA (Cook et al., 1991 a) stimulated us to determine whether AR expression was a common phenomenon in HMECs and whether AR could act as an autocrine growth factor to support the EGF-independent growth of these cells. In this study, we detected high levels of AR expression in four separate HMEC strains while one immortal mammary cell line (HBL-100) and six mammary tumor-derived cell lines had low to undetectable levels of AR. The EGF-independent growth of HMECs was blocked by the addition of heparin or a monoclonal anti-EGF receptor antibody to the culture medium, implicating AR as an autocrine growth mediator. This hypothesis is further supported by the fact that medium conditioned by HMECs contains secreted AR protein. A mammary tumor-derived cell line, Hs578T, which proliferates in an EGF-independent manner, does not express detectable levels of AR and is not growth inhibited by heparin. Examination of the same cell types for expression of transforming growth factor type-alpha (TGF-alpha) mRNA revealed coordinate expression of AR and TGF-alpha in these cells. These data suggest that both AR and TGF-alpha mRNA are produced in much greater abundance by normal HMECs than in tumor-derived cells in culture, and that AR is an important autostimulatory factor for the growth of normal HMECs.

Human epidermal growth factor. High resolution solution structure and comparison with human transforming growth factor alpha

The solution structure of the 53 amino acid peptide hormone, human epidermal growth factor (hEGF), has been determined to high resolution from nuclear magnetic resonance (n.m.r.) data. A large number of internuclear distance and dihedral restraints was obtained, including data from uniformly 15N-labelled hEGF. Dynamical simulated annealing methods using the program XPLOR were used for structure calculation. An improved protocol was developed combining efficient conformational searching at a reduced computational cost. The general fold of the calculated structures compared well with that of a derivative of the carboxy-terminally truncated hEGF determined previously. A group of 44 structures were calculated with no violations greater than 0.3 A and 3 degrees for distance and dihedral restraints, respectively. The average pairwise root mean square (r.m.s.) deviation of all backbone atoms for these structures was 2.25 A for all 53 residues, 0.92 A for the bulk of the protein, and 0.23 A for the functionally important carboxy-terminal domain. Two new helical segments containing highly conserved amino acids have been identified; one between cysteines 6 and 14 and a second at the end of the carboxy-terminal domain. New insight into the molecular architecture of the site of putative receptor binding was provided by comparing the structure of hEGF with its biologically equipotent analogue, human transforming growth factor alpha. This comparison revealed a close structural relationship between the two growth factors and provides an improved understanding of the structure/function relationships in EGF.

Isolation and partial characterization of a growth factor from human cementum

Cementum is the mineralized interface through which collagen fibers of periodontal connective tissues are anchored onto the tooth surface. We have isolated and partially characterized a mitogenic factor from human cementum which has properties different from other growth factors. Cementum was harvested from healthy human teeth, extracted in 1.0 M CH3COOH and mitogenic activities were fractionated by heparin-affinity chromatography. Proteins eluted by 0.4-0.6 M NaCl, which contained most of the cementum mitogenic activity, were precipitated by trichloroacetic acid and resolved by HPLC through ion-exchange and reverse-phase columns. NaDodSO4-polyacrylamide gel electrophoresis revealed that the purified preparation contained a M(r) 23,000 protein and this protein was associated with mitogenic activity. The purified cementum-derived growth factor (CGF) was active alone, but at suboptimal concentrations its activity was potentiated by small quantities of plasma-derived serum and epidermal growth factor (EGF). The activity was resistant to heat, but it was destroyed by trypsin digestion. Reduction and alkylation destroyed the mitogenic activity, however electrophoretic mobility was not affected. Binding of EGF to fibroblast membranes was not affected by the CGF and assays to detect platelet-derived growth factor were negative. These characteristics indicated that CGF is a distinct molecular species. Our data show that cementum contains several mitogenic factors and that CGF is the major cementum mitogen.

Differential regulation of the genes encoding platelet-derived growth factor receptor and its ligand in rat lung during microvascular and alveolar wall remodeling in hyperoxia

The growth factors that operate while the lung remodels in hyperoxia are not known. At the lung periphery, high oxygen levels cause cell hypertrophy and hyperplasia, and this results in a thickening of the alveolar-capillary membrane and the walls of its associated microvessels. The present study examines gene expression of platelet-derived growth factor (PDGF) receptor and its ligand in this region of the lung of rats breathing 87% oxygen and compares this with the levels of expression in normal lung. In similar peripheral lung tissue, the proliferative response of specific cell populations has been assessed by [3H]thymidine incorporation and autoradiography. Normal lung expresses PDGF alpha-receptor subunit transcripts of 6.5 and 4.7 kb and PDGF beta-receptor transcripts of 5.5 and 4.5 kb. PDGF A-chain transcripts of 2.9, 2.3, and 1.7 kb are also expressed, each being at 10-fold higher levels than the single 3.5-kb transcript detected for PDGF B-chain. Within hours of breathing high concentrations of oxygen, mRNA levels change rapidly for the PDGF receptor subunits. These levels return to normal after 1 day and then decline over the next 28 days of exposure. PDGF A-chain mRNA increases 12 to 18 h after exposure, but then returns to normal levels. It is the PDGF B-chain mRNA that responds most to hyperoxia by increasing 10-fold on day 3. This increase immediately precedes the proliferative response on day 4 of microvascular adventitial fibroblasts, precursor smooth muscle cells, and epithelial cells but not smooth muscle cells, which do not proliferate until day 28.

Crystallization and preliminary characterization of three crystal forms of human recombinant transforming growth factor-alpha

Three crystal forms of human recombinant TGF-alpha have been grown from solutions containing 2-methyl-2,4-pentanediol. One of the forms belongs to the orthorhombic space group C222(1) and the other two belong to the monoclinic space group C2. Two of the crystal forms diffract to approximately 2.3 A Bragg spacings. X-ray diffraction data has been collected for all three forms. These data appear to be suitable for crystal structure determination, using either heavy atom isomorphous replacement methods or molecular replacement, for phase determination.

The gene lin-3 encodes an inductive signal for vulval development in C. elegans

The lin-3 gene is necessary for induction of the Caenorhabditis elegans vulva by the anchor cell. It encodes a molecule similar to epidermal growth factor and to transforming growth factor-alpha and acts through the epidermal growth factor receptor homologue let-23. Expression of lin-3 in the anchor cell stimulates vulval induction; lin-3 may encode the vulval inducing signal.

The Drosophila spitz gene encodes a putative EGF-like growth factor involved in dorsal-ventral axis formation and neurogenesis

We describe the molecular characterization of the Drosophila gene spitz (spi), which encodes a putative 26-kD, EGF-like transmembrane protein that is structurally similar to TGF-alpha. Temporal and spatial expression patterns of spi transcripts indicate that spi is expressed throughout the embryo. Examination of mutant embryos reveals that spi is involved in a number of unrelated developmental choices, for example, dorsal-ventral axis formation, glial migration, sensory organ determination, and muscle development. We propose that spi may act as a ligand for cell-specific receptors, possibly rhomboid and/or the Drosophila EGF receptor homolog.

Autocrine action of amphiregulin in a colon carcinoma cell line and immunocytochemical localization of amphiregulin in human colon

Amphiregulin (AR) is a newly discovered glycosylated, 84-amino acid residue polypeptide growth regulator which has sequence homology to the EGF family of proteins. To obtain immunological reagents to study the biological role of AR, two synthetic peptides containing sequences corresponding to distinct regions of AR were used to generate polyclonal antibodies in rabbits. One preparation of antipeptide antibodies directed against residues 26-44 of AR (AR-Ab2) was most effective in the detection of native AR, whereas another preparation of antibodies against residues 8-26 (AR-Ab1) was found to be most efficacious in the detection of AR in formalin-fixed and paraffin-embedded tissues. The growth of a colon carcinoma cell line, Geo, which proliferates autonomously under serum-free conditions, was stimulated by the exogenous addition of AR or EGF. Half-maximal stimulation of this growth was observed at 40 and 200 pM of EGF and AR, respectively. A mAb to the extracellular domain of the EGF receptor blocked the stimulation of cell proliferation induced by the exogenous addition of AR, suggesting that this stimulation was mediated via the EGF receptor. Geo cells were found to constitutively express significant levels of the AR mRNA transcript as determined by analysis of the polymerase chain reaction-amplified cDNA product and AR protein was detected immunocytochemically using the AR-Ab1 antibodies in these cells. AR was immunoprecipitated specifically using the AR-Ab2 antibodies from the conditioned medium of Geo cells, which had been metabolically labeled with [35S]cysteine. The secreted AR migrated as a broad band (18.5-22.5 kD) with a median molecular weight of approximately 20.7 kD in SDS-PAGE. Immunospecific removal of AR from serum-free medium conditioned by the Geo cells and readdition of the AR-depleted medium to Geo cells resulted in an approximately 40% inhibition of cell growth relative to controls. Furthermore, the growth of the Geo cells was also inhibited by approximately 50% by the addition of the anti-EGF receptor mAb alone. These results indicate that AR and the EGF receptor are involved in the autocrine growth of these cells and suggests that AR may act through the EGF receptor via an extracellular autocrine loop. To study the expression of AR in human colon in vivo, AR was localized immunocytochemically in formalin-fixed, paraffin-embedded sections from normal and malignant human colon using the AR-Ab1 antibodies.(ABSTRACT TRUNCATED AT 400 WORDS)

The location and expression of fibroblast growth factor (FGF) in F9 visceral and parietal embryonic cells after retinoic acid-induced differentiation

It is well-established that fibroblast growth factors (FGFs) participate in mesoderm formation and patterning in the developing embryo. To identify cells in mammalian embryos that produce and/or respond to FGFs, we utilized the F9 teratocarcinoma cell system. Undifferentiated F9 cells resemble inner cell mass (ICM) cells of the mouse blastocyst by several criteria including having a characteristic high nuclear to cytoplasmic ratio and by their expression of stage-specific embryonic antigens. F9 stem cells differ from ICM cells by their low spontaneous rate of differentiation and their differentiation potential. ICM cells are heterogeneous with a proportion of the cells maintaining totipotency. In contrast, F9 stem cells appear capable of forming only endodermal derivatives. Retinoic acid (RA) treatment of F9 stem cells is required for them to differentiate, and under different culturing conditions the F9 cells will form either extraembryonic parietal or visceral endoderm. We have previously shown that FGF is synthesized by F9 parietal endoderm, but not by F9 stem cells. Our present study demonstrates that F9 aggregate cultures that contain visceral endoderm cells produce cell-associated-heparin-binding mitogens for 3T3 and endothelial cells, factors with characteristics of FGFs. Furthermore, our studies detect endothelial cell-mitogens within the extracellular matrix (ECM) of F9 parietal endoderm cells, not detected within F9 stem cell 'matrices'. Parietal endoderm cell matrix mitogens could be removed by prior treatment of the ECM with buffers containing heparin or 2 M NaCl, and could be neutralized by basic FGF antibodies.

Identification of heregulin, a specific activator of p185erbB2

The proto-oncogene designated erbB2 or HER2 encodes a 185-kilodalton transmembrane tyrosine kinase (p185erbB2), whose overexpression has been correlated with a poor prognosis in several human malignancies. A 45-kilodalton protein heregulin-alpha (HRG-alpha) that specifically induced phosphorylation of p185erbB2 was purified from the conditioned medium of a human breast tumor cell line. Several complementary DNA clones encoding related HRGs were identified, all of which are similar to proteins in the epidermal growth factor family. Scatchard analysis of the binding of recombinant HRG to a breast tumor cell line expressing p185erbB2 showed a single high affinity binding site [dissociation constant (Kd) = 105 +/- 15 picomolar]. Heregulin transcripts were identified in several normal tissues and cancer cell lines. The HRGs may represent the natural ligands for p185erbB2.

Neu differentiation factor: a transmembrane glycoprotein containing an EGF domain and an immunoglobulin homology unit

We recently reported that a 44 kd glycoprotein secreted by transformed fibroblasts stimulates tyrosine phosphorylation of the product of the neu proto-oncogene and induces differentiation of mammary tumor cells to milk-producing, growth-arrested cells. A partial amino acid sequence of the protein, termed Neu differentiation factor (NDF), enabled cloning of the corresponding complementary DNA. The deduced structure of the precursor of NDF indicated that it is a transmembrane protein whose extracellular portion contains an EGF-like domain that probably functions as a receptor recognition site. In addition, the ectodomain contains one immunoglobulin homology unit. Despite the lack of a recognizable hydrophobic signal peptide at the N-terminus, a recombinant NDF, like the natural molecule, is released into the medium of transfected COS-7 cells in a biologically active form. Northern blot analysis indicated the existence of several NDF transcripts, the major ones being 1.8, 2.6, and 6.7 kb in size. Transformation by the ras oncogene dramatically elevated the expression of NDF in fibroblasts.

Expression cloning of a diphtheria toxin receptor: identity with a heparin-binding EGF-like growth factor precursor

A monkey cDNA (pDTS) encoding a diphtheria toxin (DT) sensitivity determinant was isolated by expression cloning in mouse L-M cells. Mouse cells are naturally resistant to DT, because they lack functional cell surface receptors for the toxin. Unlike wild-type L-M cells, pDTS-transfected mouse cells are extremely toxin sensitive and specifically bind radioiodinated DT. Intoxication of the transfected cells requires receptor-mediated endocytosis of the bound toxin. The cDNA is predicted to encode an integral membrane protein that is identical to the precursor of a heparin-binding EGF-like growth factor. The DT sensitivity protein is thus a growth factor precursor that DT exploits as a receptor.

Epidermal growth factor receptor: elements of intracellular communication

While EGF has an important function in cell growth regulation, the molecular mechanisms by which intracellular signal connect the EGF: receptor complex on the plasma membrane with the initiation of DNA synthesis and mitogenesis is not well understood. The discovery that rasGAP, PI-3 kinase and PLC-gamma 1 are substrates for the EGF receptor tyrosine kinase has provided a beginning in understanding the biochemistry underlying growth factor receptor transduction.

Distribution of fibroblast growth factors in cultured tumor cells and their transplants

The distributions of acidic fibroblast growth factor (aFGF) and basic FGF (bFGF) in extracts of various cultured mammalian cells were determined from their elution profiles on heparin-affinity chromatography, and assay of activity as ability to stimulate DNA synthesis in BALB/c3T3 cells. Only aFGF was found in extracts of mouse melanoma B 16 cell and rat Morris hepatoma cell (MH1C1) lines. Other tumor cell lines established from solid tumors and some normal cells contained bFGF as a main component, but blood tumor cell lines contained no aFGF or bFGF. The FGFs in extracts of solid tumor tissues derived by transplantations of these cultured tumor cells and various normal tissues of mice were also examined. Tumors formed by all cell lines, regardless of whether they produced aFGF, bFGF, or neither, contained bFGF that was probably derived from host cells including capillary endothelial cells, in addition to the tumor-derived aFGF or bFGF, if produced. The content of bFGF, possibly derived from the host, in these tumor tissues was comparable to those of various mouse organs other than thymus, lung, spleen, and testis, which have higher bFGF contents. Tumor tissues derived from cultured cells producing bFGF had relatively higher bFGF contents. Like bFGF, aFGF was distributed almost ubiquitously in normal mouse tissues.

Androgen-responsive expression and mitogenic activity of schwannoma-derived growth factor on an androgen-dependent Shionogi mouse mammary carcinoma cell line

We report here, using the androgen-dependent SC2G cell line derived from Shionogi mouse mammary carcinoma SC115, that cDNA encoding mouse homologue of the rat schwannoma-derived growth factor (SDGF) was isolated and its protein product was identified to be an autocrine growth factor which is expressed in response to androgen in this hormone-dependent cell line. The androgen-independent SC1G cells derived from SC115 were shown to express SDGF even in the absence of androgen, while Northern analysis probed with mouse mammary tumor virus (MMTV) DNA showed that the androgen inducible transcriptional machinery remains functional in this hormone independent cell line.

Species-specific differences in the mitogenic activity of heparin-binding growth factors in the sera of various mammals

Sera from different mammalian species displayed great differences in mitogenic activity, as measured by stimulation of DNA synthesis in BALB/c 3T3 cells (3T3 cells). Among the sera examined, fetal bovine serum was least active, and increasing activity was detected in calf serum, human serum, rat serum and mouse serum, in that order. Rat and mouse sera exhibited extremely high mitogenic activity with 3T3 cells, but when TIG-1 human fetal lung fibroblasts were used for the DNA assay instead, the activity levels of all of the sera were lower, and the differences between them were smaller. To determine the reasons for these differences, the heparin-binding growth factors in each serum were separated on a heparin affinity column. Five peaks of DNA-stimulating activity were obtained. Three of these were found in all sera examined, with both 3T3 cells and TIG-1 cells. Two other peaks were found only with 3T3 cells; one was peculiar to rat and mouse sera, with extremely high activity in the rat, and the other was specific to fetal serum. The dependence of the activity of these peaks on the cells used for the test was confirmed using normal rat lung fibroblasts and immortalized rat kidney cells. These findings adequately explain the species-specific differences in mitogenic activity of whole sera, and the variation in activity depending on the cells used for assay of DNA synthesis.

Epidermal growth factor stimulates cAMP accumulation in cultured rat cardiac myocytes

We have previously shown that epidermal growth factor (EGF) augments cAMP accumulation in the heart and stimulates cardiac adenylyl cyclase via a G protein mediated mechanism (Nair et al., 1989). More recently, employing an antibody against the carboxy-terminus decapeptide of Gs alpha, we have demonstrated that Gs alpha mediates the effects of EGF on cardiac adenylyl cyclase (Nair et al., 1990). Since the heart comprises of a variety of cell types, the purpose of the studies presented here was to determine whether or not the effects of EGF on adenylyl cyclase were mediated in cardiac myocytes or noncardiomyocytes. Therefore, cultures of ventricular cardiomyocytes and noncardiomyocytes from neonatal rat hearts were established and characterized. Apart from the differences in cellular morphology, cardiomyocytes but not the noncardiomyocytes employed in our studies expressed the alpha- and beta-myosin heavy chain (MHC) mRNA and the beta-MHC protein. Additionally, as described previously, treatment of cardiomyocytes with thyroid hormone increased alpha-MHC mRNA and decreased the expression of beta-MHC mRNA, indicating that the cardiomyocytes employed in our studies were responding in a physiologically relevant manner. EGF in a time-dependent manner increased cAMP accumulation in the cardiomyocytes but not in noncardiomyocytes. Maximum and half-maximum effects were observed at 100 nM and 2 nM concentrations of EGF, respectively. As determined by the presence of immunoreactive EGF receptors and tyrosine phosphorylation of the 170 kDa protein in membranes of cardiomyocytes and noncardiomyocytes, both the cell populations contained functional EGF receptors. Therefore, the differential effects of EGF on cAMP accumulation in the two cell populations appear to be due to differential coupling of the EGF receptors to the adenylyl cyclase system rather than the absence of EGF receptors in noncardiomyocytes. Consistent with our previous findings in isolated membranes and perfused rat hearts, EGF-elicited increase in cAMP accumulation in cardiomyocytes did not involve activation of beta-adrenoreceptors and was abolished by prior treatment of cells with cholera toxin. Overall, our findings demonstrate that EGF-elicited increase in cAMP accumulation in the heart is the reflection of changes in cAMP content of cardiomyocytes and not noncardiomyocytes.

Inhibition of autonomous human keratinocyte proliferation and amphiregulin mitogenic activity by sulfated polysaccharides

We previously demonstrated that human keratinocyte cultures proliferate in the absence of polypeptide growth factors (autonomous growth) and that this autonomous growth is blocked by interaction of heparin with a human keratinocyte-derived autocrine factor (KAF) which we identified as amphiregulin (AR). In the present study, we demonstrate that sulfated polysaccharides other than heparin (low and high molecular weight dextran sulfates) also inhibit the AR-mediated autonomous proliferation of human keratinocytes. Furthermore, sulfated polysaccharides such as high and low molecular weight dextran sulfates, heparan sulfate and, to a lesser extent, chondroitin sulfates B and C were also shown to be inhibitors of human keratinocyte-derived AR (k-d AR)-stimulated DNA synthesis in quiescent murine AKR-2B cell cultures. Our results demonstrate that sulfation of polysaccharides is required for AR inhibitory activity, and that several sulfated polysaccharides (other than heparin) can act as inhibitors of AR-mediated autonomous proliferation in human epidermal keratinocytes and as inhibitors of k-d AR-mediated mitogenic activity in AKR-2B cells.

Modulation of epidermal growth factor receptors in psoriatic lesions during treatment with topical EGF

Active psoriatic lesions have increased EGF/TGF alpha receptors, historically known as the EGF-R. This increase is due to their persistence into the outer parakeratotic layers as measured by autoradiography, immunohistochemistry, and mRNA assays. When psoriatic lesions in patients resolve due to therapy with different modalities, the EGF-R persistently expressed in the outer layers of the epidermis either disappear or resume a basal location presumably due to receptor downregulation. To test whether EGF could downregulate EGF-R and biologically affect psoriatic epidermis, split-thickness skin grafts of active psoriatic lesions were sutured onto the dorsal surface of nude mice. After 3 weeks, the mice were treated daily for a 6-week period with placebo, or 10 or 50 micrograms/ml EGF. Immunostaining showed persistent EGF-R in all epidermal layers in the untreated, placebo-, and 10 micrograms/ml EGF-treated groups. Those grafts receiving a high dose of EGF (50 micrograms/ml) showed either no immunoreactive EGF-R or faint basilar staining. As an additional check for functional activity of the EGF-R, an abundant substrate for this receptor, PLC-gamma 1 was also evaluated following EGF treatment. A similar distribution and modulation pattern following treatment were observed in the grafts immunostained for PLC-gamma 1, suggesting that exogenous EGF treatment affected metabolic pathways subsequent to ligand receptor binding. Morphologic alterations characteristic of a regressing psoriatic phenotype (a decrease in acanthosis, thickness, and the resumption of the orthokeratotic mode of differentiation) were noted in those lesions receiving the 50 micrograms/ml EGF treatment. This study indicates that persistent EGF-R in psoriasis vulgaris are biologically active in vivo and may serve a pivotal role in the regulation of psoriatic lesions.

Isolation and sequence of the granulin precursor cDNA from human bone marrow reveals tandem cysteine-rich granulin domains

Granulins are candidate growth factors recently discovered in human and rat inflammatory leukocytes and bone marrow. Two granulin homologs, epithelin 1 and 2, occur in the rat kidney. Epithelin 1, which is probably identical to rat leukocyte granulin, exhibits proliferative and antiproliferative effects on epithelial cells in vitro. Here we show by cDNA analysis that the prepropeptide for the human granulins is a 593-residue glycoprotein, containing seven tandem repeats of the 12-cysteine granulin domain. By Northern blot analysis, gene expression was seen in myelogenous leukemic cell lines of promonocytic, promyelocytic, and proerythroid lineage, in fibroblasts and was seen very strongly in epithelial cell lines. Some epithelial cell lines respond to the mature peptide and express the gene. Among tissues examined, the kidney had the highest levels of granulin mRNA.

Heparin is required for cell-free binding of basic fibroblast growth factor to a soluble receptor and for mitogenesis in whole cells

Heparin is required for the binding of basic fibroblast growth factor (bFGF) to high-affinity receptors on cells deficient in cell surface heparan sulfate proteoglycan. So that this heparin requirement could be evaluated in the absence of other cell surface molecules, we designed a simple assay based on a genetically engineered soluble form of murine FGF receptor 1 (mFR1) tagged with placental alkaline phosphatase. Using this assay, we showed that FGF-receptor binding has an absolute requirement for heparin. By using a cytokine-dependent lymphoid cell line engineered to express mFR1, we also showed that FGF-induced mitogenic activity is heparin dependent. Furthermore, we tested a series of small heparin oligosaccharides of defined lengths for their abilities to support bFGF-receptor binding and biologic activity. We found that a heparin oligosaccharide with as few as eight sugar residues is sufficient to support these activities. We also demonstrated that heparin facilitates FGF dimerization, a property that may be important for receptor activation.

Macrophages in tissues and in vitro

Macrophages have specialized functions in different tissue microenvironments such as lymphohaemopoietic organs and the nervous system. Recently, progress has been made in defining cellular and molecular properties of isolated and tissue macrophages in the developing and adult animal.

Colorectum cell-derived growth factor (CRDGF) is homologous to amphiregulin, a member of the epidermal growth factor family

We have previously shown that an autocrine factor (CRDGF) of molecular weight 25,000 is produced by the HT29 human colon cancer cell line. Although CRDGF was shown to inhibit the binding of epidermal growth factor (EGF) to its receptor, several lines of evidence suggested that it was distinct from EGF or transforming growth factor-alpha (TGF-alpha). In order to check the possibility that CRDGF represents a new member of the EGF family, a four-step purification protocol involving acid gel filtration, cation-exchange high-performance liquid chromatography (HPLC), C18 reversed-phase HPLC and gel permeation HPLC was used to purify this protein to homogeneity. The purified material exhibited a 22 kDa molecular mass on SDS-PAGE. Partial N-terminal amino acid sequence of CRDGF showed identity to amphiregulin (AR), an EGF-related protein. Western blotting experiments using AR-specific antiserum confirmed that CRDGF and AR are identical proteins. In addition, we showed that AR, like EGF or TGF-alpha stimulated the phosphorylation of the epidermal growth factor receptor (EGF-R) on tyrosine residues. This indicates that the AR intracellular signalling pathway involves the activation of EGF-R kinase.

Heparin is required for cell-free binding of basic fibroblast growth factor to a soluble receptor and for mitogenesis in whole cells

Heparin is required for the binding of basic fibroblast growth factor (bFGF) to high-affinity receptors on cells deficient in cell surface heparan sulfate proteoglycan. So that this heparin requirement could be evaluated in the absence of other cell surface molecules, we designed a simple assay based on a genetically engineered soluble form of murine FGF receptor 1 (mFR1) tagged with placental alkaline phosphatase. Using this assay, we showed that FGF-receptor binding has an absolute requirement for heparin. By using a cytokine-dependent lymphoid cell line engineered to express mFR1, we also showed that FGF-induced mitogenic activity is heparin dependent. Furthermore, we tested a series of small heparin oligosaccharides of defined lengths for their abilities to support bFGF-receptor binding and biologic activity. We found that a heparin oligosaccharide with as few as eight sugar residues is sufficient to support these activities. We also demonstrated that heparin facilitates FGF dimerization, a property that may be important for receptor activation.

Transforming growth factors and related peptides in gastrointestinal neoplasia

Transforming growth factor alpha and beta 1 (TGF alpha and TGF beta 1) are representative members of two distinct and expanding families of polypeptide growth factors. TGF alpha is an epithelial cell mitogen, whereas TGF beta 1 inhibits epithelial cell growth; the role of these factors in contributing to the transformed phenotype is uncertain. Steady state mRNA expression for these growth factors and their receptors in a panel of human colon cancers and adjacent normal mucosa is presented. Based in part on results from transgenic mice in which TGF alpha is selectively overproduced in the mammary gland, a possible role for TGF alpha as a tumor promoter in the process of transformation is discussed.

Interaction of heparin-binding EGF-like growth factor (HB-EGF) with the epidermal growth factor receptor: modulation by heparin, heparinase, or synthetic heparin-binding HB-EGF fragments

The binding of heparin-binding EGF-like growth factor (HB-EGF) to the epidermal growth factor (EGF) receptor of human endometrial carcinoma cells was compared to that of EGF using an 125I-EGF radioreceptor assay. The inhibitory effect of HB-EGF on 125I-EGF binding was reversed either in the presence of heparin (but not by chondroitin sulfate) or by pre-treating the cells with heparinase. These treatments did not affect the binding of EGF to its receptor. To map potential regions in the HB-EGF molecule that mediate its heparin-dependent interaction with the EGF receptor, HB-EGF peptides were synthesized that were non-homologous to EGF. Accordingly residues 20-25 and 36-41, but not residues 8-19, of HB-EGF were found to be (i) heparin-binding and (ii) modulators of HB-EGF (but not of EGF) binding to the EGF receptor.

Light microscopic and ultrastructural pathology of seminiferous tubules of rats given multiple doses of Pasteurella multocida group D protein toxin

Male Holtzman rats were given subcutaneous doses of a purified Pasteurella multocida group D heat-labile toxin on alternate days for up to 22 days. Rats were necropsied at 18 days or 36 days (14 days after last dose of toxin) or when moribund, and testicles were taken for histologic and ultrastructural examination. Other selected tissues, including liver and spleen, were taken for histologic examination. Histologically, testicular and splenic lesions occurred more consistently and at much smaller doses when compared with lesions in other target organs such as liver. Testicular and splenic lesions were present in all rats (6/6) given 0.8 micrograms/kg toxin and were seen in some rats (1/6) given as little as 0.2 micrograms/kg toxin. Only 3/6 rats given 0.8 micrograms/kg toxin had hepatic lesions; no hepatic lesions were seen at doses of 0.2 micrograms/kg. Testicles from toxin-treated rats were smaller and weighed less than controls. Seminiferous tubules were moderately dilated and lined by polygonal sertoli cells. The normal spermatogenic maturation sequence and mature spermatids were absent, and many tubules contained multinucleate spermatocytes. Severely affected tubules were necrotic and mineralized. Ultrastructurally, there was necrosis of adluminal spermatocytes, multinucleate cell formation, and spaces between Sertoli cell plasma membranes. Testicular lesions were similar to those described for vitamin D-deficient rats, vitamin A-deficient rats, vasectomized rats, and rats given intravenous tumor necrosis factor; however, rats given lethal doses of toxin did not have elevated levels of TNF alpha activity.

The interaction of amphiregulin with nuclei and putative nuclear localization sequence binding proteins

Amphiregulin (AR) is a 23 kDa, bifunctional growth modulating glycoprotein belonging to the epidermal growth factor (EGF) family of polypeptide growth regulators. AR possesses two putative nuclear localization sequences (NLS), binds to DNA sepharose, and localizes to the nucleoli of human ovarian surface epithelial carcinoma cells suggesting that AR has a direct nuclear role. We have found that 125I-labeled AR, when exogenously applied to several carcinoma cell lines, associated with nuclei in a time, temperature, and concentration dependent fashion. The control peptide, EGF, also associated with these fractions but at approximately 20% of the efficiency of AR. Cross-linking experiments with 125I-labeled AR and nuclear fractions derived from various carcinoma and normal cell lines demonstrated that AR binds two proteins of molecular mass 205 and 120 kDa. AR binding to these nuclear fraction proteins was specific and saturable as shown by competition experiments utilizing both SV-40 large T antigen NLS and an AR derived peptide encompassing both putative AR NLS. The combined results suggest that nuclear interactions may play a significant role in AR induced growth responses.

Growth factors and cutaneous wound repair

The healing of an adult skin lesion is a well studied but complex affair of some considerable clinical interest. Endogenous growth factors, including the EGF, FGF, PDGF and TGF beta families, are released at the wound site and presumed to be a necessary part of the natural wound healing machinery. Moreover, members of each of these families have been shown to enhance healing if added exogenously to a wound site. In this review we shall briefly discuss what is known about the mechanics and cell biology of adult wound healing, describe the normal cellular source of growth factors during the healing process and, with reference to their known capacities in tissue culture, speculate as to how particular growth factors might be able to enhance healing.

Response to and expression of amphiregulin by ovarian carcinoma and normal ovarian surface epithelial cells: nuclear localization of endogenous amphiregulin

Amphiregulin (AR) is a polypeptide growth regulator which has sequence homology to the epidermal growth factor-related family of ligands and contains putative nuclear targeting sequences. Human ovarian carcinoma cell lines and their normal counterparts, ovarian surface epithelial cells (OSEs), were assessed for their ability to respond to and express AR. Addition of exogenous AR (8-200 pM) inhibited the growth of 2 of 3 OSE specimens and 3 of the 6 carcinoma cell lines indicating that AR has the potential to inhibit the growth of normal cells, in addition to carcinoma cells. In contrast, concentrations of AR ranging from 1-5 nM stimulated the growth of all 3 of the OSEs and 4 of the 6 carcinoma cell lines. Immunocytochemical staining of the cells using antipeptide antibodies directed against residues 8-26 of AR indicated that all cells expressed AR and that the staining was localized to the nucleus. The nuclear staining of AR was concentrated in the nucleolus of the carcinoma cells, whereas the staining was diffuse in the nucleus of the OSEs. These results suggest that AR may play a growth regulatory role in the nucleus of cells and this role may be different in normal and malignant epithelial cells.

Extracellular matrix regulation of growth factor and protease activity

Extracellular matrices bind many growth factors, proteases, and protease inhibitors. These interactions not only localize these molecules to the pericellular environment, but also modulate their biological activities. Recent evidence suggests that some growth factors may be active in vivo primarily in complexes with extracellular matrix molecules and that this interaction may be essential to their activity.

Dystrophic neurites infiltrate extracellular neurofibrillary tangles in Alzheimer disease

The neurotrophic activity of beta-amyloid protein (beta-AP) has been suggested to be responsible for the dystrophic neurites that surround beta-AP deposits in senile plaques of Alzheimer disease. The recent finding that neurofibrillary tangles (NFT) that remain as remnants in the extracellular space (E-NFT) after the death of the neuron contain beta-AP, suggested that dystrophic neurites might also be associated with E-NFT. In this study, we use a probe for E-NFT, basic fibroblast growth factor (bFGF)-binding to show that E-NFT do contain dystrophic neurites. Since these neurites contain the amyloid precursor protein whose cleavage can lead to beta-AP, they may also play a role in further beta-AP deposition in the E-NFT.

Differential expression of epidermal growth factor-related proteins in human colorectal tumors

Amphiregulin (AR) and cripto are proteins that are structurally related to epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha). AR is also functionally related to this family of growth regulatory molecules and is able to bind and activate the 170-kDa EGF receptor (EGFR). Human EGFR-3 (HER3)/ERBB3 is a recently identified protein related to the EGFR that is widely expressed in breast carcinomas and is a candidate receptor for EGF-like growth factors. Differential expression of these putative ligands and receptors in transformed cells suggests that they may function in an autocrine manner to regulate tumor cell growth. Specific mRNA transcripts for TGF-alpha [4.8 kilobases (kb)], AR (1.4 kb), cripto (2.2 kb), and HER3 (6.2 kb) were expressed in a majority of human colon cancer cell lines. HER3 mRNA was detected in 55% of primary or metastatic human colorectal carcinomas but in only 22% of normal colon mucosa and 32% of normal liver samples. In contrast, cripto and AR mRNA were expressed in 60-70% of primary or metastatic human colorectal cancers but in only 2-7% of normal human colonic mucosa. Immunostaining also detected AR protein in primary and metastatic colorectal tumors but not in normal colon or uninvolved liver. These findings suggest that cripto and AR may be useful markers to discriminate between normal and malignant colonic epithelium and may provide a selective growth advantage for colorectal carcinomas.