Antibodies to the epidermal growth factor receptor block the biological activities of sarcoma growth factor

Breast milk jaundice correlates with high levels of epidermal growth factor

Maternal milk plays an important role in breast milk jaundice (BMJ) development and is the major source of epidermal growth factor (EGF) for neonates. The aim of this study was to investigate whether there is a relationship between EGF levels in the infant serum and in the milk of nursing mothers and BMJ. Two groups were defined: study group (n = 30), newborns who were followed up for BMJ without any identifiable pathologic cause; control group, healthy newborns whose serum total bilirubin levels were <10 mg/dL. Milk and infant plasma samples were collected between the third and the fourth postpartum week. EGF concentrations in all of the samples were determined by using ELISA. The infants with BMJ had higher concentrations of EGF in the serum and in the breast milk compared with that of the infants without BMJ. The milk concentrations of EGF were significantly correlated with neonatal bilirubin and blood EGF concentrations. The degree of BMJ was associated with the increased levels of milk borne EGF. Although the exact mechanisms of the hyperbilirubinemic action of EGF are not completely known, the inhibition of gastric motility, increased absorption, and activation of bilirubin transport have been suggested as possible mechanisms.

Proteolytic processing of TGFα redirects its mitogenic activity: the membrane-anchored form is autocrine, the secreted form is paracrine

Wild-type transforming growth factor alpha (TGFalpha) expression in lactotrope cells in the pituitary gland led to lactotrope-specific pituitary hyperplasia and adenomata. To indicate whether the EGF receptor is involved in this TGFalpha-mediated phenotype, we bred TGFalpha mice with mice expressing the cytoplasmic truncated-EGF receptor (EGFR-tr), which is dominant-negative in other models. These bitransgenic mice developed pituitary pathology despite expression of the dominant-negative receptor. To further characterize this observation, we generated two lineages of transgenic mice that overexpress mutant forms of TGFalpha: a processed soluble form (s TGFalpha) and a cytoplasmic-deleted form (TGFalphaDeltaC). While sTGFalpha expression in lactotrope cells failed to induce autocrine lactotrope hyperplasia, the pituitary became very enlarged due to proliferation of neighboring interstitial cells. In contrast, the TGFalphaDeltaC mice did not develop a phenotype, although the mRNA and protein were present in the pituitary and this form of TGFalpha was confirmed to be biologically active and targeted properly to the plasma membrane of cultured CHO cells. The results suggest that the cytoplasmic domain of TGFalpha is required for autocrine parenchymal tumor formation in the pituitary gland. This signal cannot be inhibited by the EGFR-tr. Conversely, the released form of TGFalpha appears to have primarily paracrine activity.

Milk-borne epidermal growth factor modulates intestinal transforming growth factor-alpha levels in neonatal rats

Epidermal growth factor (EGF) is present in milk from various mammalian species, but its physiologic function in neonatal development remains unclear. Transforming growth factor-alpha (TGF-alpha) is a peptide structurally related to EGF, and its presence is detected in the developing small intestine of rats. The purpose of the present study was to examine the effect of milk-borne EGF on endogenous production of EGF and TGF-alpha in the small intestine of suckling rats. Neonatal rats were fed via gastrostomy either growth factor-free rat milk substitute (RMS) or RMS supplemented with EGF (100 ng/mL of RMS) from 8 to 12 d of age. Artificially reared rats were then compared with their dam-fed littermates. Animals fed the EGF-deficient diet RMS had markedly increased EGF and TGF-alpha mRNA levels in duodenum and ileum compared with dam-fed controls and significantly elevated total intestinal content of TGF-alpha peptide. Intestinal EGF content and EGF serum levels were significantly decreased in the RMS group compared with controls. The addition of EGF to the RMS diet normalized TGF-alpha mRNA levels in the duodenum and ileum, EGF mRNA levels in the ileum, and total intestinal TGF-alpha content and EGF serum levels to the levels measured in dam-fed littermates. Motility studies showed that enteral administration of EGF did not affect stomach emptying and intestinal transit. These studies indicate that exogenous milk-borne EGF modulates endogenous production of TGF-alpha in developing small intestine. It is likely that neither TGF-alpha nor EGF are solely responsible for small intestinal overgrowth of artificially reared neonatal rats.

Transfection of anti-sense complementary DNA of human epidermal-growth-factor receptor attenuates the proliferation of human non-small-cell-lung-cancer cells

The proliferation of human non-small-cell-lung-cancer (NSCLC) cells is regulated by the epidermal-growth-factor-receptor (EGFR)-mediated autocrine loop that interacts with transforming growth factor-alpha (TGF-alpha) of autocrine or paracrine origin. We have shown that EGFR expression is elevated in the brain metastatic variant of human NSCLC cells H226Br, which thereby acquire their increased sensitivity toward exogenous TGF-alpha. To determine detailed cell-phenotype changes as a result of EGFR down-regulation, H226Br cells were transfected with a human EGFR-cDNA construct encompassing an N-terminal fragment (1.8 kb) in anti-sense orientation downstream of the cytomegalovirus (CMV) promoter. The EGFR transcript expressed in the 3'-5' direction is expected to neutralize EGFR mRNA and to reduce protein expression correspondingly. The established cell lines resistant to G418 were shown integrated with the transfected construct and their proliferation rates reduced as compared with the parental cells and with those transfected with vector alone. Down-regulated EGFR expression in cells with the anti-sense construct can be confirmed by Scatchard analysis and suppressed EGFR kinase activity. The restrained-growth phenotype is also demonstrated in the prolonged G2-M phase during the cell cycle, and correlated with impairment of cell proliferation. This finding suggests that EGFR over-expression is critical in maintaining the malignant phenotype of NSCLC cells, thereby providing a valuable biomarker and potential target prevention for lung-cancer-cell proliferation.

Adaptation after small bowel resection is attenuated by sialoadenectomy: the role for endogenous epidermal growth factor

BACKGROUND

Epidermal growth factor (EGF) is likely involved during adaptation after small bowel resection (SBR) because some studies have shown enhanced adaptation by EGF administration. Because the major source of endogenous EGF in mice is the submandibular glands, we sought to determine the effect of submandibular gland excision (SAL) and luminal or systemic EGF replacement on adaptation after SBR.

METHODS

A 50% proximal SBR or Sham-SBR (bowel transection and reanastomosis) was performed on male C57BL/6 mice after either SAL or gland mobilization only. Additional mice underwent both SBR and SAL and then received daily EGF or saline solution by intraperitoneal or orogastric administration. At 1 week, adaptation was characterized in the ileum as changes in villus height, DNA, and protein content.

RESULTS

SAL significantly attenuated the increase in ileal villus height, total protein, and DNA content after SBR. Both systemic and oral EGF reversed these findings equally and significantly augmented all parameters of intestinal adaptation after SAL.

CONCLUSIONS

Submandibular EGF is important for the adaptive response to massive SBR. As both luminal and systemic EGF equally reversed the findings following SAL and SBR, the specific site of action for endogenous EGF during adaptation is either the luminal or basolateral surface of the enterocyte.

Differential modulation of pro- and anti-inflammatory cytokine receptors by N-(4-trifluoromethylphenyl)-2-cyano-3-hydroxy-crotonic acid amide (A77 1726), the physiologically active metabolite of the novel immunomodulator leflunomide

N-(trifluoromethylphenyl)-2-cyano-3-hydroxy-crotonic acid amide (A77 1726), the physiologically active metabolite of leflunomide, has been described to exert antiproliferative effects in vitro and anti-inflammatory actions in several animal models. Currently, its use is being evaluated in clinical trials in psoriasis, which is characterized by epidermal hyperproliferation and infiltration of inflammatory cells. We studied the effects of A77 1726 on growth and gene expression in cultured epidermal cells by 5-bromo-2'-deoxy-uridine (BrdU) incorporation, reverse transcriptase-polymerase chain reaction (RT-PCR), Northern blot hybridizations and flow cytometry. A77 1726 inhibited epidermal proliferation at concentrations above 5 microM after 24 hr. However, the cells were still fully viable at a concentration of 100 microM. The drug caused a dose-dependent reduction in the mRNA level of the type A receptor for the proinflammatory cytokine interleukin-8 (IL-8-RA) and, in contrast, induced gene expression of the receptor for the anti-inflammatory cytokine IL-10 (IL-10R) at the mRNA and protein levels. In addition, the mRNA and protein levels of the p53 gene, which is a negative cell cycle regulator, were up-regulated by A77 1726. These data suggest that A77 1726 exerts its anti-inflammatory action via the modulation of epidermal gene expression.

Histamine H2-receptor antagonists stimulate proliferation but not migration of human gastric mucosal cells in vitro

Gastric mucosal cell migration and proliferation are crucial events in the repair of gastric mucosal erosions. This study was designed to test the hypothesis that the H2 blockers roxatidine and ranitidine might stimulate migration and proliferation of gastric mucous cells derived from a human well-differentiated gastric adenocarcinoma cell line (MKN 28 cells) in vitro, in conditions independent of systemic factors and of acid inhibition. Confluent monolayers of MKN 28 cells were wounded with a razor blade and were then incubated with roxatidine or ranitidine. The number of cells migrating to the damaged area was determined 24 hr later. Cell proliferation was assessed by means of [3H] thymidine uptake and cell counts after incubation with roxatidine or ranitidine. Neither H2 antagonist significantly stimulated cell migration. On the other hand, cell proliferation was dose-dependently and significantly enhanced by incubation with roxatidine and ranitidine. Exogenous administration of TGF-alpha significantly stimulated MKN 28 cell division. However, incubation with roxatidine or ranitidine did not increase the steady-state mRNA expression of TGF-alpha or EGFR as assessed by northern blot analysis. Based on these in vitro findings, we postulate that the ulcer healing effect of these H2 antagonists in vivo might be due in part to stimulation of gastric mucosal cell proliferation.

Simulated annealing with restrained molecular dynamics using CONGEN: energy refinement of the NMR solution structures of epidermal and type-alpha transforming growth factors

The new functionality of the program CONGEN (Bruccoleri RE, Karplus M, 1987, Biopolymers 26:137-168; Bassolino-Klimas D et al., 1996, Protein Sci 5:593-603) has been applied for energy refinement of two previously determined solution NMR structures, murine epidermal growth factor (mEGF) and human type-alpha transforming growth factor (hTGF alpha). A summary of considerations used in converting experimental NMR data into distance constraints for CONGEN is presented. A general protocol for simulated annealing with restrained molecular dynamics is applied to generate NMR solution structures using CONGEN together with real experimental NMR data. A total of 730 NMR-derived constraints for mEGF and 424 NMR-derived constraints for hTGF alpha were used in these energy-refinement calculations. Different weighting schemes and starting conformations were studied to check and/or improve the sampling of the low-energy conformational space that is consistent with all constraints. The results demonstrate that loosened (i.e., "relaxed") sets of the EGF and hTGF alpha internuclear distance constraints allow molecules to overcome local minima in the search for a global minimum with respect to both distance restraints and conformational energy. The resulting energy-refined structures of mEGF and hTGF alpha are compared with structures determined previously and with structures of homologous proteins determined by NMR and X-ray crystallography.

Receptor-mediated effects on ligand availability influence relative mitogenic potencies of epidermal growth factor and transforming growth factor alpha

Epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) elicit quantitatively different cell proliferation responses even though they act via a common receptor, the epidermal growth factor receptor (EGFR). We hypothesized that differential cellular trafficking of available ligand is responsible for the different mitogenic responses elicited by EGF and TGF alpha. Mitogenesis and ligand depletion were determined simultaneously in NR6 mouse fibroblasts expressing either wild-type (WT) or internalization-deficient cytoplasmic domain-truncated (c'973) EGFR. Thus we could determine the effects of both ligand-induced and low level constitutive ligand/receptor processing. For a given initial amount of growth factor, TGF alpha is a weaker stimulus than EGF in cells expressing either form of the EGFR. This difference in the mitogenic potencies correlates with increased depletion of TGF alpha observed during the growth assays. When this difference in ligand depletion is accounted for, or minimized, EGF and TGF alpha elicit quantitatively similar growth responses. Therefore, the relative mitogenic potencies of EGF and TGF alpha depend on ligand availability, as determined by the cellular trafficking of these ligands in conjunction with environmental circumstances. Interestingly, our data demonstrate that TGF alpha can be a less potent mitogenic stimulus than EGF under conditions where ligand availability is limited. Further, in our assays, differences in ligand processing are sufficient to explain the different mitogenic potencies of these growth factors in either of the receptor trafficking scenarios. Our results suggest a model of regulation of hormone responsiveness which favors dissociative ligands (such as TGF alpha) in receptor-limited situations and non-dissociative ligands (such as EGF) in the face of high receptor levels.

Transforming growth factor-alpha expression in in situ epidermal neoplasia

Twenty cases of solar keratosis and 15 cases of Bowen's disease were investigated for the expression of transforming growth factor alpha (TGF-alpha) by an indirect immunoperoxidase technique using monoclonal antibody TGF-alpha AB-2 in formalin-fixed wax-embedded tissue. Twelve cases (60%) of solar keratosis and 13 cases (86%) of Bowen's disease showed marked overexpression of TGF-alpha in both membranous and cytoplasmic distributions. This suggests that overexpression of TGF-alpha may play an important role in the evolution of these two neoplastic conditions.

Expression of transforming growth factor beta (TGF beta) receptors and expression of TGF beta 1, TGF beta 2 and TGF beta 3 in human small cell lung cancer cell lines

A panel of 21 small cell lung cancer cell (SCLC) lines were examined for the presence of Transforming growth factor beta receptors (TGF beta-r) and the expression of TGF beta mRNAs. By the radioreceptor assay we found high affinity receptors to be expressed in six cell lines. scatchard analysis of the binding data demonstrated that the cells bound between 4.5 and 27.5 fmol mg-1 protein with a KD ranging from 16 to 40 pM. TGF beta 1 binding to the receptors was confirmed by cross-linking TGF beta 1 to the TGF beta-r. Three classes of TGF beta-r were demonstrated, type I and type II receptors with M(r) = 65,000 and 90,000 and the betaglycan (type III) with M(r) = 280,000. Northern blotting showed expression of TGF beta 1 mRNA in ten, TGF beta 2 mRNA in two and TGF beta 3 mRNA in seven cell lines. Our results provide, for the first time, evidence that a large proportion of a broad panel of SCLC cell lines express TGF beta-receptors and also produce TGF beta mRNAs.

Expression of epidermal growth factor receptor (proto-oncogene c-erbB-1) and estrogen receptor in human breast carcinoma. An immunocytochemical study of 70 cases

In vitro studies have shown that growth factors may mediate the growth stimulatory effect of estrogen in hormone-dependent human breast carcinomas while the constitutive expression of same growth factors might by-pass the need for estrogenic stimulus in hormone-independent neoplasms. We have performed immunocytochemical analysis of the expression of epidermal growth factor receptor (EGF-R or proto-oncogen c-erbB-1) and estrogen receptor (ER) in 70 cases of human breast carcinoma. We found an inverse relationship between the expression of EGF-R and ER (Kendall's tau b = -0.1997, P < 0.03), which prompts us to conclude that ER(-) breast carcinomas may grow in a hormone-independent manner through the over-expression of the proto-oncogene c-erbB-1, which is the receptor for epidermal (EGF) and alpha transforming (TGFalfa) growth factors.

Transforming growth factor alpha protection against drug-induced injury to the rat gastric mucosa in vivo

This study was designed to determine whether transforming growth factor alpha (TGF alpha) protects rat gastric mucosa against ethanol- and aspirin-induced injury. Systemic administration of TGF alpha dose-dependently decreased 100% ethanol-induced gastric mucosal injury; a dose of 50 micrograms/kg delivered intraperitoneally 15 min before ethanol decreased macroscopic mucosal injury by > 90%. At the microscopic level, TGF alpha prevented deep gastric necrotic lesions and reduced disruption of surface epithelium. Pretreatment with orogastric TGF alpha (200 micrograms/kg) only partially (40%) decreased macroscopic ethanol damage. Intraperitoneal administration of TGF alpha at a dose of 10 micrograms/kg, which does not significantly inhibit gastric acid secretion, decreased aspirin-induced macroscopic damage by > 80%. TGF alpha protection does not seem to be mediated by prostaglandin, glutathione, or ornithine decarboxylase-related events, as evidenced by lack of influence of the inhibition of their production. Pretreatment with the sulfhydryl blocking agent N-ethylmaleimide partially abolished (40%) the protective effect of TGF alpha. In addition, systemic administration of TGF alpha resulted in a two-fold increase in tyrosine phosphorylation of phospholipase C-gamma 1 and in a time- and dose-dependent increase in levels of immunoreactive insoluble gastric mucin; these events occurred in a time frame consistent with their participation in the protective effect of TGF alpha.

Anti-sense transforming growth factor alpha oligonucleotides inhibit autocrine stimulated proliferation of a colon carcinoma cell line

Many carcinoma cells secrete transforming growth factor alpha (TGF alpha). A 23 base anti-sense oligonucleotide that recognizes the TGF alpha mRNA inhibits both DNA synthesis and the proliferation of the colon carcinoma cell line LIM 1215. The effects of the anti-sense TGF alpha oligonucleotide are reversed by epidermal growth factor (EGF) at 20 ng/ml. When the LIM 1215 cells are grown under serum free conditions, the anti-sense TGF alpha oligonucleotides have their greatest effects at high cell density (2 x 10(5) cells/cm2), indicating that the secreted TGF alpha is acting as an exogenous growth stimulus. In addition, at higher cell densities, the kinase activity of the EGF receptor is activated and the receptor is down-modulated. The cell density dependent activation of the EGF receptor is inhibited by the application of the antisense TGF alpha oligonucleotides.

Localization of transforming growth factor-alpha in human appendageal tumors

Transforming growth factor-alpha (TGF alpha) is a potent mitogen for epithelial cells that has been localized to normal human appendageal epithelia. To further understand the role of TGF alpha in human appendages, we examined TGF alpha expression immunohistochemically in 17 types of human appendageal tumors differentiating toward hair follicles, eccrine, apocrine, and sebaceous glands. In order of decreasing degrees of differentiation, tumors could be divided into hyperplasias, adenomas, benign epitheliomas, and primordial epitheliomas. Using an antibody that recognizes primarily the 6-kd and 13-kd forms of TGF alpha, TGF alpha immunostaining in 16 of 17 tumor types analyzed was found to follow a similar pattern, with expression in hyperplasias greater than adenomas greater than benign epitheliomas greater than primordial epitheliomas. Within a given tumor, TGF alpha expression also correlated well with the known differentiation state of the tumor cell types. The results suggest that TGF alpha expression is directly correlated with the differentiation state of hair follicle, eccrine, apocrine, and sebaceous tumors in human skin, and raises the possibility that TGF alpha may play a role in the differentiation of appendageal epithelia.

Towards a molecular basis for tamoxifen resistance in breast cancer

Breast cancer patients who acquire tamoxifen resistance may respond to second-line hormonal therapy or progress to true endocrine resistance. The biological basis for these processes are poorly understood. Following successful therapy with tamoxifen there is little evidence at relapse for change in either the host endocrine environment or drug metabolic profile to account for the development of acquired resistance. Many tamoxifen resistant tumours still retain a structurally and functionally normal oestrogen receptor (ER) and yet will grow independent of oestrogen. The oestrogen-regulated molecular events which normally govern the growth of hormone-sensitive breast cancer involve a complex autocrine and paracrine interaction between several peptide growth factors (including TGF alpha, IGF-1 and TGF beta), their receptors and signal transduction pathways. Evidence now exists that constitutive activity of many of these mediators of the mitogenic signal can bypass the cell's dependence on oestrogen and provide a mechanism for hormone-independent growth. Research into these molecular mechanisms may result in a better understanding of how to overcome the clinical problem of tamoxifen resistance.

NMR study on solution structure of the site-specific mutant Leu48----Ala transforming growth factor alpha

The NMR spectra of the Leu48----Ala mutant of human transforming growth factor alpha were compared to that of the wild-type. All chemical shift changes are less than or equal to 0.02 ppm with the exception of resonances associated with residues 47, 48 and 50 (all less than or equal to 0.07 ppm). Minimal changes were observed for NOEs associated with residues Val1 to His45. The weakening of some NOEs associated with the region Ala46-Ala50 may suggest a slightly increased flexibility for this region. Refinement of the previously calculated wild-type structures using distance constraints derived from the L48A mutant had little overall effect. Leu48-Ala50 is ill-defined for both wild-type and mutant proteins. These results suggest that Leu48 has no structural role and thus must be an important factor in the protein-receptor interface.

TGF-alpha is widely expressed in differentiated as well as hyperproliferative skin epithelium

Transforming growth factor-alpha (TGF-alpha) is a potent mitogen for epithelial cells that is expressed at low levels in normal epidermis and overexpressed in psoriasis. Epidermal growth factor (EGF) has been shown to inhibit hair growth but stimulate the growth of sebaceous and sweat glands, suggesting a potential role for a member of the EGF/TGF-alpha family in the normal development and function of skin appendages as well as epidermis. The present work demonstrates TGF-alpha protein in eccrine ducts, and eccrine, sebaceous, and apocrine glands. The proliferative dermal hair bulb does not express TGF-alpha in contrast to the differentiated outer root sheath hair follicle epithelia. In addition, hyperproliferative skin diseases including bullous congenital ichthyosiform erythroderma, squamous cell carcinoma, and psoriasis show increased TGF-alpha expression. Thus, TGF-alpha may play a role in the morphogenesis and function of normal skin appendages and its overexpression is common in benign and malignant hyperproliferative skin diseases.

Differential role of transforming growth factor-alpha in two human colon-carcinoma cell lines

Antibodies to epidermal-growth-factor receptor (EGF) and transforming growth factor-alpha (TGF-alpha) were used to determine the role of endogenous TGF-alpha in the growth of 2 human colon-carcinoma cell lines. Both the GEO and HCT 116 colon-carcinoma cell lines secrete similar levels of TGF-alpha and have similar numbers of low-affinity binding sites for EGF. However, the HCT 116 cells lack the high-affinity EGF binding site present on the GEO cells. The anti-EGF receptor antibodies effectively blocked the binding of 125I-EGF to the GEO and HCT 116 cell lines. Growth of the GEO cell line was inhibited 50-80% by the anti-EGF receptor and anti-TGF-alpha antibodies. When the same antibodies, in sufficient amounts to block binding of TGF-alpha to the cells, were added to the HCT 116 cell line, no effect on growth was seen. These results suggest that while the GEO cell line utilizes TGF-alpha in an autocrine manner, the TGF-alpha secreted by the HCT 116 cells apparently does not play a role in the growth of these cells.

Estrone modulates the EGF receptor in the liver of db/db mouse

The genetically diabetic db/db mouse is an excellent model to study the effect of diabetes on hormone receptors. The decrease of EGF binding sites could be detected in the hepatic microsomes of diabetic mice as early as 3 weeks of age. In addition, there was an age-related decrease in the autophosphorylating activity of EGF receptor isolated from the liver of diabetic mice. Estrone feeding (0.005%) partially restored this autophosphorylating activity. Northern blot analysis showed that the hepatic EGF receptor transcripts were dramatically decreased during the progression of diabetes and could be reversed by estrone feeding. Transfection experiments carried out on HepG2 cells using EGF receptor promoter (pERCAT-6) demonstrated that addition of 2 x 10(-8) M estrone stimulated chloramphenicol acetyltransferase activity. Our results suggest that estrone modulates EGF receptor by enhancing EGF receptor transcripts and the promoter activity of this gene.

Monoclonal antibody 425 inhibits growth stimulation of carcinoma cells by exogenous EGF and tumor-derived EGF/TGF-alpha

Carcinoma cells frequently coexpress transforming growth factor (TGF)-alpha and its receptor, the epidermal growth factor (EGF) receptor, implicating an autocrine function of carcinoma-derived TGF-alpha. Using a monoclonal antibody (425) to the EGF-receptor, we investigated the role of exogenous and tumor cell-derived EGF/TGF-alpha mitogenic activities in proliferation of cell lines derived from solid tumors. Monoclonal antibody 425 was chosen for these studies because it inhibits binding of EGF/TGF-alpha to the EGF-receptor and effectively blocks activation of the EGF-receptor by EGF/TGF-alpha. Seven malignant cell lines originating from carcinomas of colon, pancreas, breast, squamous epithelia, and bladder expressed surface EGF-receptor and secreted EGF/TGF-alpha-like mitogenic activities into their tissue culture media. All cell lines were maintained in a defined medium free of exogenous EGF/TGF-alpha. EGF and TGF-alpha added to the culture medium stimulated proliferation of five cell lines to comparable levels. EGF/TGF-alpha-dependent proliferation was significantly reduced by addition of MAb 425 to culture media. In addition, monoclonal antibody 425 reduced proliferation of the five EGF/TGF-alpha responsive cell lines in the absence of exogenous EGF/TGF-alpha. Antiproliferative effects induced by monoclonal antibody 425 were reversible and could be overcome by addition of EGF to culture media. Our results indicate that tumor-derived EGF-receptor-reactive mitogens can promote proliferation of carcinoma cells in an autocrine fashion.

Retroviral expression of transforming growth factor-alpha does not transform fibroblasts or keratinocytes

Transforming growth factor alpha (TGF alpha) is a peptide so named because it helps to impart anchorage-independent growth to normal rat kidney (NRK) cells in vitro and is secreted by many rodent and human tumor cells. To directly investigate the transforming properties of this factor, we constructed a replication-defective murine retrovirus that expresses the human sequence coding for TGF alpha. Infection of NIH/3T3 cells with the TGF alpha retrovirus led to the integration of a transcriptionally active provirus and overexpression of biologically active TGF alpha, but failed to induce morphologic transformation. Similarly, the TGF alpha retrovirus failed to induce morphologic transformation of five other types of rodent fibroblasts. We also investigated the effect of TGF alpha expression on the growth of BALB/MK mouse keratinocytes, which require epidermal growth factor (EGF) for proliferation. We show that exogenously added TGF alpha is an extremely potent mitogen for BALB/MK cells. However, retroviral expression of TGF alpha in BALB/MK cells failed to relieve dependence on exogenously added EGF (or TGF alpha) for cell growth. These results suggest that overexpression of TGF alpha does not, by itself, transform rodent fibroblasts or keratinocytes.

Expression of transforming growth factor-alpha in primary human colon and lung carcinomas

The expression of TGF-alpha in human colon and lung carcinoma cell lines has been reported previously, but its expression in primary tumours has not been described in detail. We have used the radio-immunoassay method to measure the specific content of immunoreactive TGF-alpha in the acid ethanol extracts of normal and cancerous tissues of human colon and lung. The average TGF-alpha content of colon carcinomas is 4 times that of the normal mucosa, and for non-small cell lung carcinomas it is twice that of the normal parenchyma. Because of variability in the TGF-alpha expression among individuals and in different segments of colon and lobes of lung, the ratio of TGF-alpha content of paired tumour and normal tissue was also calculated. On average, the tumour/normal ratio for colon carcinoma is higher than that for lung carcinoma. Although 55% of colon tumours show a ratio 4 times, or greater, only 33% of lung carcinomas demonstrate this ratio. The level of TGF-alpha in both colon and lung carcinomas does not correlate with histological type stage, grade nor degree of desmoplasia of these tumours. Northern blot analysis of total cellular RNA confirms the expression of an approximately 4.8 kb TGF-alpha mRNA in normal colonic mucosa and lung parenchyma. However, in contrast to the results of radio-immunoassay, significant over-expression of TGF-alpha mRNA is uncommon in primary human colon carcinomas.

Human keratinocyte growth factor activity on proliferation and differentiation of human keratinocytes: differentiation response distinguishes KGF from EGF family

Human keratinocyte growth factor (KGF) is an epithelial cell specific mitogen which is secreted by normal stromal fibroblasts. In the present studies, we demonstrate that KGF is as potent as EGF in stimulating proliferation of primary or secondary human keratinocytes in tissue culture. Exposure of KGF- or EGF-stimulated keratinocytes to 1.0 mM calcium, an inducer of differentiation, led to cessation of cell growth. However, immunologic analysis of early and late markers of terminal differentiation, K1 and filaggrin, respectively, revealed striking differences in keratinocytes propagated in the presence of these growth factors. With KGF, the differentiation response was associated with expression of both markers whereas their appearance was retarded or blocked by EGF. TGF alpha, which also interacts with the EGF receptor, gave a similar response to that observed with EGF. These findings functionally distinguish KGF from the EGF family and support the role of KGF in the normal proliferation and differentiation of human epithelial cells.

Molecular cloning and expression of an additional epidermal growth factor receptor-related gene

Epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha), and amphiregulin are structurally and functionally related growth regulatory proteins. These secreted polypeptides all bind to the 170-kDa cell-surface EGF receptor, activating its intrinsic kinase activity. However, amphiregulin exhibits different activities than EGF and TGF-alpha in a number of biological assays. Amphiregulin only partially competes with EGF for binding EGF receptor, and amphiregulin does not induce anchorage-independent growth of normal rat kidney cells (NRK) in the presence of TGF-beta. Amphiregulin also appears to abrogate the stimulatory effect of TGF-alpha on the growth of several aggressive epithelial carcinomas that overexpress EGF receptor. These findings suggest that amphiregulin may interact with a separate receptor in certain cell types. Here we report the cloning of another member of the human EGF receptor (HER) family of receptor tyrosine kinases, which we have named "HER3/ERRB3." The cDNA was isolated from a human carcinoma cell line, and its 6-kilobase transcript was identified in various human tissues. We have generated peptide-specific antisera that recognizes the 160-kDa HER3 protein when transiently expressed in COS cells. These reagents will allow us to determine whether HER3 binds amphiregulin or other growth regulatory proteins and what role HER3 protein plays in the regulation of cell growth.

Prognostic value of epidermal growth factor receptor in node-positive breast cancer

The prognostic significance of EGFR (epidermal growth factor receptor) was studied in a cohort of 68 node-positive patients with breast cancer, who entered a controlled protocol of adjuvant therapy between February 1980 and June 1984. EGFR radioligand binding assay was carried out on frozen stored samples. Twenty five (37%) of 68 primary sites and 9 (41%) of 19 lymph node metastases assayed were EGFR-positive with a cut off value of 5 fmol/mg membrane protein; there is no statistical difference between the two distributions. EGFR was significantly correlated to ER and histological grade. EGFR-positive tumors and high levels of EGFR were mainly found in the ER-negative group of tumors (p = 0.008) and in histological grade III (p = 0.007). Fifty five patients could be followed for 40 to 92 months. EGFR was an independent prognostic factor for survival after 40 months (p = 0.05). EGFR+/ER- patients had the lowest survival probability, but statistical significance was not reached (p = 0.06). The EGFR phenotype appeared as a patients with different early outcome, with potential therapeutic implication especially in the group of ER-negative patients. These results emphasize the need for a standardized assay methodology and for further clinical studies, particularly in protocols where adjuvant hormonal therapy is prescribed on the basis of steroid hormone receptor status, in order to assess the respective prognostic worth of EGFR and ER (or PR).

Localization of transforming growth factor alpha and its receptor in gastric mucosal cells. Implications for a regulatory role in acid secretion and mucosal renewal

Transforming growth factor alpha (TGF alpha) shares with epidermal growth factor (EGF) structural homology (35%), a common cell-surface membrane receptor (TGF alpha/EGF receptor), and a nearly identical spectrum of biological activity, including inhibition of gastric acid secretion. Herein, we report expression of TGF alpha mRNA in normal gastric mucosa of the adult guinea pig, rat, and dog. TGF alpha mRNA was also detected in matched surgically resected gastric mucosa and adjacent gastric carcinoma from 10 patients, and in gastric mucosa adjacent to a benign ulcer from an additional patient. TGF alpha protein was quantitated by radioimmunoassay and was present in tumor and adjacent mucosa. TGF alpha/EGF receptor mRNA was also detected in gastric mucosa from all species studied. Localization of TGF alpha and TGF alpha/EGF receptor mRNA expression was examined in samples of unfractionated guinea pig gastric mucosa and from chief cell-enriched and parietal cell-enriched fractions. All samples exhibited TGF alpha and TGF alpha/EGF receptor expression. The TGF alpha signal was greatest in the parietal cell fraction (5.8-fold increase), but was also enhanced in the chief cell fraction (1.9-fold increase) relative to the unfractionated gastric mucosa. Like TGF alpha expression, TGF alpha/EGF receptor mRNA expression was most intense in the parietal cell-enriched fraction (7.8-fold increase), but was also increased in the chief cell-enriched fraction (2.7-fold increase) relative to the unfractionated guinea pig gastric mucosa. We conclude that TGF alpha and TGF alpha/EGF receptor genes are expressed in normal adult mammalian gastric mucosa. These findings, when interpreted in light of described actions of TGF alpha and EGF, provide evidence that local production of TGF alpha could play an important role in the regulation of acid secretion and mucosal renewal in the stomach.

Expression of transforming growth factor alpha messenger RNA in the normal and neoplastic gastro-intestinal tract

The presence of TGF alpha mRNA has been reported previously to occur in primary colon cancers. We report the expression of the normal 4.5 kb TGF alpha transcript in the mucosa of the normal human gastro-intestinal tract from oesophagus through to colon. The highest levels of human TGF alpha mRNA occurred in the duodenum but significant levels were present in all of the mucosa. Similarly, in the rat gastro-intestinal tract, TGF alpha transcripts were detected in the lower gastro-intestinal tract mucosa. The relative abundance of the TGF alpha mRNA appeared to decrease in distal regions of the gastro-intestinal tract. The level of the TGF alpha mRNA was similar in both the normal and the neoplastic colon tissue. Similarly, in 2 patients with carcinomas, the TGF alpha mRNA was expressed at similar levels in the tumour and in adjacent mucosa. Although TGF alpha mRNA is associated with transformed cells from the gastro-intestinal tract, the presence of this mRNA at equivalent concentrations in normal mucosa suggests that over-production of TGF alpha is not an essential feature of carcinomas in the gastro-intestinal tract.

A high-resolution 1H-NMR study of human transforming growth factor alpha. Structure and pH-dependent conformational interconversion

The 500-MHz and 600-MHz 1H-NMR spectra of recombinant human transforming growth factor alpha have been recorded at pH values of 3.8, 6.5 and 9.4. Analysis of various two-dimensional spectra has enabled sequence-specific assignments to be made and the secondary structure to be identified. Information on the tertiary fold has also been obtained from observed nuclear Overhauser effects and titration of histidine residues. The overall fold of the protein is very similar to that of epidermal growth factor, as might be expected from the sequence similarity. However, the structure of transforming growth factor alpha at pH 3.8 is found to show interesting differences from those at the two higher pHs and from that of epidermal growth factor.

Mitogenic regulation of normal and malignant breast epithelium

The multiple roles of both estrogenic and polypeptide regulators of mammary epithelial cell growth are reviewed in this article. Effects of both steroidal and peptide hormones are complex and involve multiple interactions with malignant cells and non-malignant host components. Initial carcinogenesis and progression of mammary epithelium to cancer probably require both proliferative stimuli (estrogen, polypeptide growth factors) and genetic damage. This condition may lead to qualitatively different hormonal responses (hormone-responsive cancer). Estrogens can be shown to induce growth-regulatory polypeptide growth factors and interact with them in hormone-dependent breast cancer. Progression of hormone-dependent (estrogen-responsive) breast cancer to hormone independence probably involves multiple mechanisms, including oncogene activation, loss of the estrogen receptor, or loss of hormone responsivity of other gene products. One direction for further therapies may be blockade of hormonal stimulation and interference with necessary activated or induced components of malignant progression such as oncogenes or polypeptide growth factor-receptor systems.

Spontaneously transformed NRK cells lose their mitogenic response to epidermal growth factor

To understand the relationship between growth factor-induced mitogenesis and spontaneous cell transformation, a clonal isolate of epidermal growth factor (EGF)-responsive NRK cells was passed in vitro until morphologically transformed variants arose. Subclones of EGF responsive (Cl-3) and EGF nonresponsive (Cl-10) NRK cells were isolated. Cl-3 cells grew as flat, contact-inhibited monolayers, while Cl-10 cells grew as rounded or spindle-shaped cells that formed dense foci. Cl-10 cells formed colonies in soft agar more efficiently (p less than 0.01) and formed larger tumors in nude mice (p less than 0.05) than Cl-3 cells. Cl-3 cells exhibited a sixfold increase in DNA synthesis in response to 1.0 nM EGF. Cl-10 cells did not increase DNA synthesis on exposure to 100 nM EGF. These different responses to EGF occurred despite similar numbers of receptors and similar receptor.binding affinities for EGF (Cl-3: 7000 receptors, Kd = 0.67 nM; Cl-10: 8000 receptors, Kd = 0.72 nM). No evidence of transforming growth factor-alpha was detected in either of these cell lines using Northern blots, Western blots, or biologic assays. We conclude that NRK cells which undergo spontaneous morphologic transformation and exhibit enhanced anchorage-independent growth lose their mitogenic response to EGF.

Cooperative transforming activities of ras, myc, and src viral oncogenes in nonestablished rat adrenocortical cells

Early-passage rat adrenocortical cells were infected with Kirsten murine sarcoma virus and MMCV mouse myc virus, two retroviruses carrying the v-Ki-ras and v-myc oncogenes, respectively. Efficient morphological transformation required coinfection with the two viruses, was dependent on the presence of high serum concentrations, and was not immediately accompanied by growth in soft agar. The doubly infected cells coordinately acquired the capacity for anchorage- and serum-independent growth during passage in culture. The appearance of such highly transformed cells was correlated with the emergence of a dominant clone, as suggested by an analysis of retrovirus integration sites. These results indicate that the concerted expression of v-Ki-ras and v-myc could induce rapid morphological transformation of nonestablished adrenocortical cells but that an additional genetic or epigenetic event was required to permit full transformation by these two oncogenes. In contrast, v-src, introduced by retrovirus infection in conjunction with v-myc, rapidly induced serum- and anchorage-independent growth. Therefore, the p60v-src protein-tyrosine kinase, unlike p21v-ras, is apparently not restricted in the induction of a highly transformed phenotype in adrenocortical cells. This system provides an in vitro model for the progressive transformation of epithelial cells by dominantly acting oncogenes.

Androgens stimulate both growth rate and epidermal growth factor receptor activity of the human prostate tumor cell LNCaP

LNCaP cells (derived from a lymph node carcinoma of the human prostate) contain androgen receptors and show androgen-responsive growth in vitro. Maximal effects on growth were seen at 0.1 nM of the synthetic androgen R1881 or 0.2 nM of epidermal growth factor (EGF); both compounds independently increased the growth rate 2-3 times. EGF-receptors were measured after 6 days culture in the presence or absence of 0.1 nM R1881. A 2.3-fold increase in receptor number/cell was found when binding was measured at 0 degrees C (from 12,500 to 28,900 sites/cell in stimulated cells). The kD value (0.45 nM) was not affected by androgen treatment. The increase of EGF-receptor activity was first observed between 6 and 12 h after exposure to androgen. It is concluded that LNCaP cells are sensitive to low concentrations of EGF (or EGF-like compounds) and that one of the mechanisms involved in androgen action on these cells is an increase of EGF-receptor expression at the cell surface.

Preparation of a monoclonal antibody to a melanoma growth-stimulatory activity released into serum-free culture medium by Hs0294 malignant melanoma cells

Autostimulatory growth factors may contribute to the ability of malignant cells to escape normal growth controls. We have previously shown that Hs0294 human malignant melanoma cells release into culture medium an acid-soluble, heat-stable, trypsin-sensitive, autostimulatory monolayer mitogen which can be purified from acetic acid extracts of conditioned medium by gel filtration, reverse-phase high-performance liquid chromatography, and preparative electrophoresis. The majority of this melanoma growth-stimulatory activity (MGSA) resides in a 16-Kd moiety, though bioactivity is also associated with 24-26 and less than 14-Kd forms of MGSA (Richmond and Thomas: J Cell Physiol 129:375, 1986). In order to further characterize this growth factor, monoclonal antibodies were prepared against a partially purified preparation of the autostimulatory melanoma mitogen. Monoclonal antibody clones were selected based on supernate inhibition of 3H-thymidine incorporation in serum-free Hs0294 melanoma cultures. One of these, termed FB2AH7, slows, but does not completely block, the growth of Hs0294 cells in serum-free medium in a dose-dependent manner. This antibody does not slow the growth of normal rat kidney fibroblasts, which neither produce nor require this mitogen, in either serum-free medium or medium containing 0.8% calf serum. This monoclonal antibody also blocks the mitogenic effects of partially purified preparations of this melanoma growth stimulatory activity (MGSA) on both Hs0294 cells and normal rat kidney fibroblasts. The FB2AH7 antibody has been demonstrated to bind MGSA by Western blot and by immunoprecipitation procedures. Western blot analysis of reverse-phase high-performance liquid chromatography purified growth factor demonstrated that FB2AH7 antibody binds to the 16-Kd and approximately 13-14-Kd forms of MGSA. FB2AH7 antibody can be used in immunoprecipitation experiments to bind the approximately 13-16-Kd forms of MGSA. The specificity of the binding of FB2AH7 antibody for MGSA but not other growth factors has been demonstrated in a modified dot blot assay. These data thus support the hypothesis that MGSA is an autostimulatory melanoma mitogen distinct from other growth factors.

Epidermal-growth-factor receptor status as predictor of early recurrence of and death from breast cancer

In 135 primary breast cancers, there was a significant inverse relation between epidermal-growth-factor receptor (EGFR) and oestrogen receptor (ER) status, and a significant association with tumour size and poor differentiation. The relapse-free survival and overall survival were significantly worse for patients with EGFR+ tumours compared with EGFR- tumours. Relapse-free survival and overall survival were also worse for patients with ER- tumours compared with ER+ tumours. Of the 71 ER- patients 28 were EGFR+ and 43 were EGFR-. The relapse-free and overall survival for ER- but EGFR+ patients were significantly worse than for "double-negative" patients. Moreover, relapse-free survival and overall survival for "double-negative" patients were similar to those for ER+ patients. Thus EGFR status divides the ER- population into good and poor prognosis subgroups. The presence of EGFR was the most important variable in the primary tumours for predicting relapse-free and overall survival. Multivariate analysis showed that EGFR status was the most important variable in predicting relapse-free and overall survival in lymph-node-negative patients, and the second most important variable in lymph-node positive patients.

The human transforming growth factor type alpha coding sequence is not a direct-acting oncogene when overexpressed in NIH 3T3 cells

A peptide secreted by some tumor cells in vitro imparts anchorage-independent growth to normal rat kidney (NRK) cells and has been termed transforming growth factor type alpha (TGF-alpha). To directly investigate the transforming properties of this factor, the human sequence coding for TGF-alpha was placed under the control of either a metallothionein promoter or a retroviral long terminal repeat. These constructs failed to induce morphological transformation upon transfection of NIH 3T3 cells, whereas viral oncogenes encoding a truncated form of its cognate receptor, the EGF receptor, or another growth factor, sis/platelet-derived growth factor 2, efficiently induced transformed foci. When NIH 3T3 clonal sublines were selected by transfection of TGF-alpha expression vectors in the presence of a dominant selectable marker, they were shown to secrete large amounts of TGF-alpha into the medium, to have downregulated EGF receptors, and to be inhibited in growth by TGF-alpha monoclonal antibody. These results indicated that secreted TGF-alpha interacts with its receptor at a cell surface location. Single cell-derived TGF-alpha-expressing sublines grew to high saturation density in culture. However, when plated as single cells on contact-inhibited monolayers of NIH 3T3 cells, they failed to form colonies, whereas v-sis- and v-erbB-transfected cells formed transformed colonies under the same conditions. Moreover, TGF-alpha-expressing sublines were not tumorigenic in nude mice. These and other results imply that TGF-alpha exerts a growth-promoting effect on the entire NIH 3T3 cell population after secretion into the medium but little, if any, effect on the individual cell synthesizing this factor. It is concluded that the normal coding sequence for TGF-alpha is not a direct-acting oncogene when overexpressed in NIH 3T3 cells.

Malignant transformation of murine fibroblasts by a human c-Ha-ras-1 oncogene does not require a functional epidermal growth factor receptor

Although mutations in ras genes are thought to be important for the development of about 20% of human tumors, almost nothing is known about the way in which these mutations lead to cellular transformation. The known biochemical properties of the 21-kilodalton ras proteins suggest that they may behave as G proteins, regulating the proliferation of cells in response to growth factor stimulation of a receptor. Although the putative receptor(s) has not been identified, several lines of evidence, in particular the fact that rodent cell lines containing ras oncogenes produce transforming growth factor alpha, have suggested that the epidermal growth factor (EGF) receptor is involved in ras transformation. Here we show that murine fibroblasts with no EGF receptors can be transformed to a completely malignant phenotype with a mutated ras gene. It appears, therefore, that the EGF receptor is not required for ras-mediated transformation of these cells.