Epidermal Growth Factor-urogastrone Research Articles

Tumor inhibitory effects of 131I-Trastuzumab on human epidermal growth factor receptor 2 overexpressing breast cancer cells and its possible mechanisms

Objective To explore antitumor effect of 131I-Trastuzumab on human epidermal growth factor receptor(HER)2 overexpressing breast cancer cells and investigate its possible mechanism. Methods The expression levels of HER2 of three different breast cancer cell lines (BT474, MCF-7, HCC1937) were detected with immunofluorescence. Trastuzumab was labeled with 131I using the Iodogen method and 131I-Trastuzumab was isolated with ultrafiltration membrane, then the labeling efficiency, radiochemical purity and immunoreactivity were measured. The effects of 131I, Trastuzumab and 131I-Trastuzumab on viability of BT474 cells were evaluated with cell counting kit-8 (CCK-8) assay. The levels of total Akt and phosphorylated Akt (p-Akt) were detected with Western blot analysis. One-way analysis of variance (ANOVA), ANOVA for factorial design, Bonferroni correction and Pearson correlation analysis were used for data analysis. Results The expression level of HER2 in BT474 cells was much higher than those in HCC1937 and MCF-7 cells. The labeling efficiency, radiochemical purity and immunoreactivity of 131I-Trastuzumab were (89.71±2.93)%, (91.80±1.43)% and (58.84±3.35)% respectively. 131I (4.625 GBq/L), Trastuzumab(125.0 mg/L) and 131I-Trastuzumab(4.625 GBq/L) exhibited a dose-dependent cytotoxicity against BT474 cells (r=-0.964, -0.912, -0.618; all P 0.05). P-Akt expression in both Trastuzumab group and 131I-Trastuzumab group were much lower than those of control group and 131I group (t=12.524, 15.984, 7.347, 10.807; all P 0.05). Conclusions 131I-Trastuzumab may kill HER2 overexpressing breast cancer cells more effectively than Trastuzumab alone. The underlying mechanism may be attributed to that 131I-Trastuzumab may enhance the radiosensitivity by the inhibitory effect on PI3K/Akt pathway and thus exert synergistic effects with 131I. Key words: Breast neoplasms; Receptors, epidermal growth factor-urogastrone; Antibodies, monoclonal; Iodine radioisotopes; Tumor cells, cultured

Preparation of HER2 radioligand 99Tcm-ABH2 and its in vivo imaging in breast cancer-xenografted mice

Objective To prepare 99Tcm-human epidermal growth factor receptor 2 (HER2) affibody (ABH2) and explore its feasibility as an imaging agent in HER2-positive breast cancer. Methods Sodium glucoheptonate and SnCl2·2H2O were used to label ABH2 with 99Tcm. The labeling yield and radiochemical purity of 99Tcm-ABH2 were determined. The stability of 99Tcm-ABH2 was tested in PBS and serum. The equilibrium disassociation constant (Kd) of 99Tcm-ABH2 was measured with MBA-MD-361 breast cancer cells. SPECT/CT imaging was carried out at 1.0 h and 4.5 h after injection of 37 MBq 99Tcm-ABH2 in nude mice (n=4) xenografted with MBA-MD-361 breast cancer. The T/NT (liver, brain, lung, heart, bone and muscle) ratios were deduced from SPECT/CT acquired data. For the blocking experiment, 200 μg ABH2 was injected intravenously before 99Tcm-ABH2 injection. SPECT/CT imaging was performed in the same way. The T/NT ratios were compared between non-blocked and blocked groups by one-way analysis of variance. Results The labeling yield of 99Tcm-ABH2 was above 99%. 99Tcm-ABH2 was substantially stable in PBS and serum; the radiochemical purity was (95.0±1.0)% after incubation with serum at 37 ℃ for 6.0 h. The Kd of 99Tcm-ABH2 was 1.7 nmol/L. The radioactive uptake in cancer was visualized at 1.0 h and 4.5 h after injection of 99Tcm-ABH2 in HER2 positive MDA-MB-361 breast cancer. 99Tcm-ABH2 was cleared out mainly through urinary system. The ratios of tumor to liver, lung, brain, heart, muscle and bone were 1.81±0.60, 8.95±1.13, 20.08±6.12, 7.61±0.56, 10.62±1.78, 11.42±2.07, respectively at 4.5 h after 99Tcm-ABH2 injection. After ABH2 blocking, the corresponding T/NT ratios were 0.60±0.23, 3.05±1.38, 5.24±2.17, 2.42±1.02, 8.16±2.66, 2.76±0.48 (F=29.38, P<0.05) respectively. Conclusion 99Tcm-ABH2 could be synthesized with high purity, and this new agent could be used to image HER2-positive breast cancer specifically. Key words: Breast neoplasms; Receptors, epidermal growth factor-urogastrone; Isotope labeling; Tomography, emission computed, single-photon; Tomography, X-ray computed; Mice, nude; ABH2

Epidermal growth factor receptor binding and biological activity in the ovary of goldfish, Carassius auratus.

The receptor binding and biological activity of epidermal growth factor-urogastrone (EGF) was characterized in the follicle-enclosed goldfish oocyte. The binding of 125I-labeled mouse EGF (mEGF) to goldfish ovarian membrane preparation was peptide specific, saturable, reversible, and dependent on time and tissue concentration. Binding data analysis indicated the presence of a single class of high-affinity binding sites with an estimated equilibrium dissociation constant of 4.4 +/- 1.8 x 10(-10) M. The 125I-mEGF binding was displaced by unlabeled mEGF and by human recombinant transforming growth factor-alpha (hTGF-alpha). Both mEGF and hTGF-alpha were found to stimulate reinitiation of oocyte meiosis, as indicated by germinal vesicle breakdown (GVBD). Treatment with mEGF and hTGF-alpha stimulated GVBD from a basal level of 8.5 to approximately 30% with an estimated half-maximal effective dose for EGF of 5.80 +/- 0.82 + 10(-10) and for hTGF-alpha, 1.9 +/- 1.0 x 10(-10) M. Furthermore, treatment with mEGF marginally increased 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (DHP)-induced GVBD without significantly influencing the gonadotropin-induced response. Treatment with either mEGF or hTGF-alpha significantly reduced human chorionic gonadotropin-stimulated testosterone production in a concentration-related manner. These data suggest that members of the EGF family may play a role in the regulation of ovarian function in goldfish.

Tyrosine kinase-mediated signal transduction pathways and the actions of polypeptide growth factors and G-protein-coupled agonists in smooth muscle.

This synopsis focuses on the role that tyrosine kinase pathways may play in the acute regulation of smooth muscle contractility by receptor-kinase-activating growth factors, such as epidermal growth factor-urogastrone (EGF-URO) and by G-protein-coupled agonists, such as angiotensin-II. Growth factor-activated response paradigms that modulate smooth muscle contractility are summarized and the parallels between the actions of G-protein-coupled agonists and growth factors in these response systems are pointed out. A possible dynamic interplay between tyrosine kinase and tyrosine phosphatase activities to modulate tissue tension is also hypothesized. Finally, a model is proposed, wherein an intermediary tyrosine kinase pathway is suggested as a point of convergence for the regulation of smooth muscle contractility by agonists as diverse as EGF-URO and angiotensin-II.

Regulation of vascular and gastric smooth muscle contractility by pervanadate

1. The contractile actions of vanadate (VO4) and pervanadate (PV, peroxide(s) of vanadate) were studied in rat gastric longitudinal muscle strips and in aortic rings. The roles of extracellular sodium and calcium were evaluated and the potential effects of nerve-released agonists were considered. The possibility that these responses were due to the potentiation of tyrosine kinase activity, as a result of PV-mediated tyrosine phosphatase inhibition was explored with the use of tyrosine kinase inhibitors (genistein, tyrphostin) and by Western blot analysis of phosphotyrosyl proteins in PV-treated tissues. The ability of PV to mimic the action of the tyrosine kinase receptor-associated agonist, epidermal growth factor-urogastrone (EGF-Uro), in the gastric preparation was also studied. 2. PV caused concentration-dependent contractions in both gastric and aorta-derived tissues, with a potency that was 1 to 2 orders of magnitude greater than that of VO4. 3. Although repeated exposure of gastric and aortic tissues to a fixed concentration of VO4 caused reproducible contractions in both tissues, repeated exposure of gastric tissue to PV caused an increased contractile response plateauing after 3 exposures. In contrast, a single exposure of aortic tissue to PV (20 microM) caused a prolonged desensitization of the tissue to the subsequent contractile actions of PV or other agonists. 4. The contractile responses to PV were unaffected in both preparations by tetrodotoxin, atropine, yohimbine and phenoxybenzamine; and in the aortic preparation, the responses to VO4 and PV were the same in the presence or absence of a functional endothelium. 5. PV-induced contractions in both tissues were observed in the absence of extracellular sodium but required extracellular calcium and were attenuated by 1 micro M nifedipine.6. In the gastric preparation, the characteristics of the contractile actions of PV paralleled those of EGF-Uro in terms of (1) inhibition by genistein, (2) inhibition by indomethacin and (3) a requirement for extracellular calcium. These response characteristics differed from those of other contractile agonists such as carbachol.7. In both the gastric and aortic preparations genistein was able to inhibit PV-induced contractions selectively without causing comparable inhibition of KCI-induced contractions. Tyrphostin (AG18) also selectively blocked PV-induced contractions in the gastric, but not in the aortic preparation.8. In both the gastric and aortic tissue, in step with an increased contractile response, PV caused increases in tissue phosphotyrosyl protein content, as detected by Western blot analysis using a monoclonal antiphosphotyrosine antibody; the increases in phosphotyrosyl protein content were reduced when tissues were treated with PV at the same time as a tyrosine kinase inhibitor.9 PV, at sub-contractile concentrations, potentiated the contractile action of angiotensin II in both the gastric and aorta tissue.10 We conclude that the growth factor-mimetic agent, PV, is a much more potent contractile agonist than V04 in both vascular and gastric smooth muscle tissue. PV can cause enhanced tissue phosphotyrosyl protein content most likely via the inhibition of tissue protein tyrosine phosphatases. The contractile actions of PV, which require extracelullar calcium and are independent of extracellular sodium, would appear not to be due either to Na+/Ca2" exchange, promoted by Na+/K+-ATPase inhibition or to the inhibition of Ca2+-ATPase and might be best explained by the ability of PV, via tyrosine phosphatase inhibition, to potentiate a tyrosine kinase pathway linked to calcium entry and to the contractile process.

The ulceration-associated cell lineage (UACL) reiterates the Brunner's gland differentiation programme but acquires the proliferative organization of the gastric gland.

The ulceration-associated cell lineage (UACL) develops in the human gastrointestinal mucosa after ulceration; it grows out from the bases of adjacent crypts and ramifies in the lamina propria to form a new gland, finally giving rise to a duct by which the glandular secretion and indeed cells are carried to the surface. Using immunocytochemistry and in situ hybridization with 35S-labelled riboprobes, we have defined the pattern of trefoil peptide gene expression (pS2; human spasmolytic polypeptide, hSP), epidermal growth factor/urogastrone (EGF/URO), and the distribution of cell proliferation during the development of the UACL, as indicated by immunostaining for proliferating cell nuclear antigen (PCNA). Our studies reveal that the morphogenesis of the UACL shows a marked morphological resemblance to developing Brunner's glands; the pattern of trefoil peptide gene expression during UACL development is also very similar. However, trefoil peptide gene expression in the mature UACL complex is unique amongst gastrointestinal cells. The mature UACL shows a distinctive proliferative organization: while the early buds and glands are non-proliferative, apparently being fed by cells from the parent crypts, a definitive proliferative zone develops within the duct. This, of course, corresponds to the location of the gastric gland proliferative zone. We propose that while the UACL shows novel features, it shares its differentiation programme with Brunner's glands, but its pattern of cell renewal eventually is that of the gastric gland.

The acute actions of growth factors in smooth muscle systems

Work over the past six to eight years has established that mitogenic polypeptides such as epidermal growth factor-urogastrone (EGF-URO) or platelet-derived growth factor (PDGF), commonly referred to as ‘growth factors’, can have rapid (seconds to minutes) regulatory actions in a variety of smooth muscle systems. With EGF-URO as a prototype example, this article describes three distinct smooth muscle response paradigms, two of which (type A and type B) comprise a rapid (seconds to minutes) increase in muscle tension) and one of which (type C) is characterized by an EGF-URO-mediated reduction in sensitivity to other agonists. The quite distinct signal transduction pathways for the three types of response paradigms are outlined, and the marked tissue and species variation in the types of smooth muscle responses that can be observed, even for a single growth factor agonist, are summarized. The article also illustrates that G-protein-coupled vasoactive agents such as angiotensin-II and vasopressin, which can act as ‘growth factors’ in cultured cell systems, can also work via tyrosine kinase pathways to cause contraction in some of the same intact smooth muscle preparations that contract in response to growth factors such as EGF-URO. Attention is drawn to the fact that many so-called ‘growth factors’, quite apart from stimulating cell division and differentiation, may in many instances act as rapid localized paracrine/autocrine regulators of tissues such as smooth muscle. It is also pointed out that some of the tyrosine kinase-modulated signal pathways usually associated with the mitogenic action of ‘growth factors’ may be involved not only in the rapid effects of agents such as EGF-URO in smooth muscle but also in the contractile actions of G-protein-linked agonists.

Potentiation of sensory tachykininergic transmission by epidermal growth factor-urogastrone

Potentiation of sensory tachykininergic transmission by epidermal growth factor-urogastrone

Synergistic actions of epidermal growth factor-urogastrone and vasopressin in cultured aortic A-10 smooth muscle cells.

In cultured rat aorta-derived A-10 cells, epidermal growth factor-urogastrone (EGF-URO) acts synergistically with arginine vasopressin (AVP) to augment the AVP-mediated release of 3H-arachidonate (3H-AA) from 3H-AA prelabeled cells. On its own, EGF-URO had no effect on AA release and had no effect on calcium influx or efflux either in the absence or presence of AVP. The synergistic action of EGF-URO was not affected by actinomycin D, cycloheximide, indomethacin, by the diacylglycerol lipase inhibitor U-57,908, or by the tyrosine kinase inhibitors genistein (GS) and tyrphostin (TP). TP did, nonetheless, completely abrogate 3H-thymidine incorporation triggered in the presence of EGF-URO. Although EGF-URO stimulated an increase in calpactin-II (lipocortin-I) phosphorylation in permeabilized cells, no such increase was detected in intact cells exposed to EGF-URO either alone or in combination with AVP, under conditions where EGF-URO augmented the action of AVP. The phospholipase A2 inhibitor, mepacrine, had no effect on AVP-mediated AA release, but abolished the synergistic action of EGF-URO. We conclude that in contrast with our previous results with gastric smooth muscle strips, wherein EGF-URO acts via the diacylglycerol lipase-mediated metabolism of diacylglycerol, and in keeping with observations with cultured mesangial cells, EGF-URO acts synergistically with AVP in A-10 cells via the activation of phospholipase A2. This synergistic action of EGF-URO does not appear to be due to increased levels of cyclooxygenase and would appear not to require increased tyrosine kinase activity.

Association of radiolabeled urogastrone binding with regenerating intestinal mucosa and epidermal growth factor/ urogastrone producing organs in rat

In the present study, we have tested the hypothesis that the regeneration of intestinal epithelium is regulated by changes in the uptake of radiolabeled recombinant human urogastrone ( 125I rhUG) in the regenerating mucosa and epidermal growth factor/urogastrone (EGF/URO) producing organs in the rats. Operations were performed on rats to approximate the ileal mucosa to the serosal surface of the cecum. This procedure allows the regeneration of ileal mucosa onto the serosal surface of the cecum. Groups of 5 rats were killed on the 2nd, 4th, 8th and 12th post-operative days. Two hours before autopsy, rats were given 0.5 ml (50 μCi with 30 μgm protein) of 125I rhUG intravenously and the following tissues were removed: regenerating mucosa, salivary gland, duodenum, liver and kidney. Results indicated that the uptake of 125I rhUG was significantly greater in the salivary gland and duodenum on the 2nd post-operative day which gradually tapered with increasing time after surgery. A similar pattern in the uptake of 125I rhUG was also evident in the regenerating mucosa. Further analysis revealed a significant correlation between the uptake of 125I rhUG in the salivary gland and duodenum vs rate of epithelialization and uptake of 125I rhUG in the regenerative mucosa. These results suggested that the endogenous EGF/URO produced in the salivary gland and duodenum may be a factor in the regulation of intestinal regeneration; however, the mechanism responsible for reflex stimulation of EGF/URO production in these organs is not known.

Effects of urogastrone-epidermal growth factor on intestinal brush border enzymes and mitotic activity.

The wet weight of the stomach, small intestine, caecum, and colon were significantly reduced (p less than 0.001) in intravenously fed rats compared with orally fed controls. Human epidermal growth factor (urogastrone) reversed this atrophy. Detailed analysis of the small intestine showed a similar effect on intestinal crypt cell population, mitoses per crypt, and protein content. Brush border gamma glutamyltransferase and alpha glucosidase activities were reduced by up to 50% throughout the small intestine of the animals fed intravenously. The specific activities (mU/mg protein) were unchanged, as a concomitant decrease in the tissue weight and protein content also occurred. Intestinal brush border enzyme activities in the rats treated with urogastrone-epidermal growth factor were restored to those seen in the orally fed rats except for alpha glucosidase activity in the proximal gut. In addition, the specific activity of gamma glutamyltransferase was highly significantly increased (p less than 0.01) in all regions of the small intestine. Thus, although urogastrone administration prevents the decrease in brush border enzyme activity seen after the removal of luminal nutrition, the response seems to differ depending on the intestinal location, with the specific activities of some enzymes being higher than those seen in orally fed rats. Urogastrone-epidermal growth factor can thus significantly increase the functional ability of the intestine in addition to its trophic effects.

Diacylglycerol lipase and the contractile action of epidermal growth factor-urogastrone: evidence for distinct signal pathways in a single strip of gastric smooth muscle

In guinea pig gastric longitudinal muscle preparations, wherein epidermal growth factor-urogastrone (EGF-URO) causes contraction via the generation of arachidonate-derived prostaglandins, the specific diacylglycerol lipase (DG lipase) inhibitor. U57,908 (formerly designated RHC 80267) completely blocked EGF-URO and transforming growth factor-α (TGF-α)-mediated contraction, without affecting contractions caused by other agonists such as bradykinin, prostaglandin F 2α or arachidonic acid (AA). In contrast, the contractile actions of EGF-URO and TGF-α on the gastric circular muscle component, present in the same tissue strip as the longitudinal muscle preparation, were unaffected by concentrations ofU57,908 that maximally inhibited contraction in the longitudinal muscle preparation. We conclude that in the longitudinal muscle preparation, EGF-URO acts not by the activation of phospholipase A 2, but rather via the metabolism of diacylglycerol by DG lipase, thereby liberating arachidonic acid for the synthesis of contractile prostanoids. We also conclude that, even in the same tissue, the effects of EGF-URO on anatomically different components (longitudinal muscle versus circular muscle) can be mediated via two quite distinct signal transduction pathways.

Distinct receptors for epidermal growth factor-urogastrone in cultured gastric smooth muscle cells

We describe a propagable cell strain from guinea pig gastric circular muscle (GCM), which we have characterized in terms of its smooth muscle phenotype and its binding and biological response (thymidine incorporation) to epidermal growth factor-urogastrone (EGF-URO) and transforming growth factor-alpha (TGF-alpha). The binding of 125I-labeled EGF-URO to the GCM cells exhibited high affinity and an appropriate peptide specificity. A curvilinear Scatchard plot of the binding data indicated two classes of high-affinity binding sites (dissociation constants of 0.69 and 4.3 nM) and a maximal binding capacity of 24,000 sites/cell. Binding competition data demonstrated that the binding affinity of TGF-alpha was greater than that of EGF-URO by a factor of 2. These relative binding affinities agreed with the two- to threefold greater potency of TGF-alpha, compared with EGF-URO, for the stimulation of GCM thymidine incorporation. The relative order of binding affinity and biological potency (TGF-alpha greater than EGF-URO) was distinct from the relative order of binding affinities (EGF-URO greater than TGF-alpha) observed using guinea pig liver and human placental membrane preparations. We conclude that the cultured smooth muscle-derived GCM cells possess a receptor subtype that is in accord with contractile bioassay data obtained previously with intact gastric circular muscle strips. This receptor (TGF-alpha greater than EGF-URO) appears distinct from the one previously characterized in nonmuscle tissues.

Structure‐activity relationships for transmembrane signaling: the receptor's turn

The cloning, sequencing, and functional expression in host cells of a variety of receptors has led to a focus on the structural determinants of pharmacologic receptors involved in the complex processes of ligand binding and cell activation. The three basic mechanisms of receptor-mediated transmembrane signaling (ligand-regulated ion flux; ligand-regulated receptor-enzymes; ligand-regulated receptor-G protein activation) can now be placed in the structural context of at least three receptor superfamilies: 1) ligand-regulated oligomeric ion channels, 2) ligand-regulated tyrosine kinases, and 3) G protein-linked rhodopsin-related receptors. For each of these receptor superfamilies, structure-activity studies that use 1) site-directed mutagenesis, 2) cassette switching to form receptor chimeras, and 3) sequence-specific antireceptor antibodies are beginning to delineate the domains responsible for specific receptor functions. Analyses of such receptor domains related to: 1) ligand binding, 2) membrane insertion, 3) catalytic activity (in the case of receptor-enzymes), 4) internalization and interaction with other membrane constituents, 5) substrate or G protein binding, and 6) regulatory sites of receptor phosphorylation are discussed, using as principal examples the nicotinic receptor for acetylcholine, the epidermal growth factor-urogastrone receptor, and the beta-adrenergic receptor. These studies illustrate that in terms of structure-activity studies, which have traditionally emphasized the ligand, it is now the receptor's turn for intense attention.

Contraction of porcine ocular ciliary muscle by epidermal growth factor-urogastrone

Epidermal growth factor-urogastrone (EGF) caused a concentration-dependent contractile response in porcine ocular ciliary muscle preparations. The half-maximal contraction was observed at 23 ng/ml EGF (4 nM). The contractile action of EGF, which was not abolished by the removal of extracellular calcium, was not affected by atropine, tetrodotoxin, phentolamine and indomethacin. In addition to causing contractions on its own, the contractile action of EGF was potentiated in the presence of prostaglandin E 1 and vasopressin. Our data point to a potential role for EGF in the regulation of ciliary muscle tension.

Contribution of the C-terminal dipeptide of transforming growth factor-α to its activity: biochemical and pharmacologic profiles

We have used a matrix of biological (two distinct guinea-pig stomach contractile smooth muscle preparations) and biochemical (human placental membrane receptor binding and phosphorylation) assays to evaluate the activity profiles of epidermal growth factor-urogastrone (EGF-URO, mouse and human), transforming growth factor-α (TGF-α, human) and the TGF-α derivative lacking the C-terminal dipeptide, Leu 49-Ala 50, TGF-α-(1–48). In the longitudinal muscle (LM) bioassay, the relative potencies of the peptides were: EGF-URO > TGF-α > TGF-α-(1–48), with relative activity ratios (EC 50s) of approximately 1:3:16. In the LM assay system, TGF-α-(1–48) was a partial agonist. In the cicular muscle (CM) bioassay, the relative order of potencies was: TGF-α > EGF-URO > TGF-α-(1–48), with EC 50s of about 1:2:7. In the CM assay, all three peptides were full agonists, even though EGF-URO caused an intense desensitization of the tissue whereas TGF-α and TGF-α-(1–48) did not. The relative affinities of the peptides in the placenta membrane binding assay, EGF-URO > TGF-α > TGF-α-(1–48), were in good qualitative and quantitative agreement with the LM (but not the CM) bioassay, with relative K Ds in the proportions of about 1:3:17. In the phosphorylation assay, using either the phosphorylated EGF-URO receptor or calpactin-II as an index of receptor kinase activation, the relative potencies of the peptides, EGF-URO > TGF-α > TGF-α-(1–48), were also qualitatively in accord with the relative potencies measured in the LM and ligand binding assays (but not in the CM preparation); however, quantitatively, the relative potency ratios (EC 50s) observed in the phosphorylation assay (1:2:3) were somewhat out of keeping with the relative values observed in the LM and ligand binding assays. All three peptides were full agonists in the phosphorylation assay. Our data point to the importance of the C-terminal dipeptide, Leu 49-Ala 50 of TGF-α in terms of the binding affinity and intrinsic activity of this polypeptide; and our work provides further evidence for the distinct nature of the EGF-URO/TGF-α receptor system present in the CM bioassay preparation. The biological/biochemical activity profiles documented for the three polypeptides can serve as a basis for the further evaluation of other synthetic and naturally occurring members of the EGF-URO/TGF-α family of polypeptides.

Ulceration Induces a Novel Epidermal Growth Factor-Secreting Cell Lineage in Human Gastrointestinal Mucosa

Ulceration anywhere in the gastrointestinal tract induces a novel cell lineage, which grows from the bases of existing crypts, ramifies to form a new gland, and ultimately emerges onto the mucosal surface. The lineage produces neutral mucin, shows a unique lectin-binding profile and immunophenotype, and secretes abundant immunoreactive epidermal growth factor/urogastrone (EGF/URO). All gastrointestinal stem cells can produce this cell lineage following mucosal ulceration, secreting EGF/URO to stimulate cell proliferation, regeneration and ulcer healing. This cell lineage is very commonly associated with gastrointestinal ulceration, and we propose that a major in vivo role for EGF/URO is to stimulate ulcer healing throughout the gut via induction of this cell lineage in the adjacent mucosa. EGF/URO should therefore be assessed in the conservative management of inflammatory bowel disease.

Transforming growth factor α and epidermal growth factor levels in normal human gastrointestinal mucosa

Acid soluble proteins from 23 samples of normal human gastrointestinal mucosa derived from four normal adult organ donors were extracted and subjected to specific radiommunoassays for transforming growth factor alpha (TGF alpha) and urogastrone epidermal growth factor (URO-EGF). All tissues were found to contain immunoreactive TGF alpha and levels ranged from 57 to 4,776 pg-1 wet weight of tissue. Although levels varied between tissue donors, the distribution of TGF alpha throughout the gastrointestinal tract appeared similar in all cases. URO-EGF levels were much lower (0-216 pg g-1 wet weight). TGF alpha levels in extracts of gastrointestinal mucosa from a 7-year-old female donor were higher and the observed distribution was markedly different from adult levels. URO-EGF was not detected in mucosal or submucosal tissue extracts from this patient. Further studies in juveniles are indicated.

Growth factors, their receptors and development.

The hypothesis is put forward that the localized production of growth factors and the regulation both of their receptors and their receptor-triggered transmembrane signaling reactions played an important role in organ development. The developing palate is used as an example to support this hypothesis. Data are summarized to demonstrate that during palatogenesis, there are variations in the amount of fetal epidermal growth factor-urogastrone (EGF-URO), in the amount of EGF-URO receptor, and that there is a developmentally regulated variation in cellular responsiveness to EGF-URO. Further, it is demonstrated that the growth factor EGF-URO itself can regulate the production by palate tissue of a second growth factor, insulin-like growth factor (IGF). The multiple actions of the many so-called growth factors, quite apart from their ability to regulate cell growth are pointed out; and the implications of the many distinct actions of a single growth factor on a single cell type are discussed in the context of a developmental process like palate formation. A model is developed to illustrate the kinds of interactive processes that may occur in a tissue microenvironment during a developmental process, involving cell-cell communication and an influence of the extracellular matrix.

Autoradiographic localization of binding sites for epidermal growth factor-urogastrone (EGF-URO) in coronary arteries

Previously published data have indicated that epidermal growth factor-urogastrone (EGF-URO) can regulate blood flow in vivo and can modulate vascular smooth muscle contractility in vitro. However, the exact location of the receptors responsible for this vascular action of EGF-URO has not been previously determined. In this report, employing in vitro autoradiography with 125I-labeled EGF-URO, we have documented the presence of specific EGF-URO binding sites in the tunica media of bovine and porcine coronary arteries. Our observations support the indirect evidence pointing to presence of EGF-URO receptors on the smooth muscle elements of arterial tissue. Our data also support further the hypothesis that EGF-URO and related growth factors (like TGF-α or PDGF) may play a role in normal and pathophysiological vascular function.