Showing papers on "Growth factor receptor inhibitor published in 1996"

Vascular endothelial growth factor B, a novel growth factor for endothelial cells.

Abstract: We have isolated and characterized a novel growth factor for endothelial cells, vascular endothelial growth factor B (VEGF-B), with structural similarities to vascular endothelial growth factor (VEGF) and placenta growth factor. VEGF-B was particularly abundant in heart and skeletal muscle and was coexpressed with VEGF in these and other tissues. VEGF-B formed cell-surface-associated disulfide-linked homodimers and heterodimerized with VEGF when coexpressed. Conditioned medium from transfected 293EBNA cells expressing VEGF-B stimulated DNA synthesis in endothelial cells. Our results suggest that VEGF-B has a role in angiogenesis and endothelial cell growth, particularly in muscle.

A central role for Stat3 in IL‐6‐induced regulation of growth and differentiation in M1 leukemia cells.

Abstract: Interleukin-6 (IL-6) induces either differentiation or growth of a variety of cells. Little is known about the molecular basis of this cellular decision. The family of signal transducer and activator of transcription (Stat) proteins are involved in signaling through a variety of cytokine and growth factor receptors, although their biological roles have not been established. To address whether Stat proteins play roles in IL-6-induced growth or differentiation, we introduced two types of mutant Stat3 acting in a dominant-negative manner into M1 leukemic cells which respond to IL-6 with growth arrest and terminal differentiation. We show that dominant-negative forms of Stat3 inhibited both IL-6-induced growth arrest at G(0)/G1 and macrophage differentiation in the M1 transformants. Blocking of Stat activation resulted in inhibition of IL-6-induced repression of c-myb and c-myc. Furthermore, IL-6 enhanced the growth of M1 cells primarily through shortening the length of the G1 period when Stat3 was suppressed. Thus IL-6 generates both growth-enhancing signals and growth arrest- and differentiation-inducing signals at the same time. Stat3 may be a key molecule which determines the cellular decision from cell growth to differentiation in M1 cells.

Dominant-Negative Inhibition of Flk-1 Suppresses the Growth of Many Tumor Types in Vivo

Abstract: Angiogenesis, the sprouting of new blood vessels from existing vessels, occurs in many physiological and pathological processes, including embryonic development, wound healing, and tumor growth. It is required for tumor growth because new blood vessel formation is necessary for tumors to expand beyond a minimum volume. Several growth factor receptor tyrosine kinases have been implicated in angiogenesis, including receptors for epidermal, fibroblast, and platelet-derived growth factors, as well as the receptors Flk-1/KDR, Flt-1, Tek/Tie-2, and Tie-1. Endothelial cells in the vessels of tumors express Flk-1/KDR, a receptor for vascular endothelial growth factor. Flk-1 was previously shown to play a role in angiogenesis and tumor formation of s.c. xenografts of C6 glioma cells using dominant-negative methodology. We now demonstrate that Flk-1 seems to be generally involved in the growth of a wide range of solid tumors, including mammary, ovarian, and lung carcinoma, as well as glioblastoma. Furthermore, survival times in rats bearing intracerebral tumors were prolonged using the same dominant-negative methodology. The involvement of Flk-1 in a variety of tumor types suggests an important role for Flk-1 in tumor angiogenesis.

Flk-1 as a Target for Tumor Growth Inhibition

Abstract: A number of growth factor receptor tyrosine kinases have been implicated in angiogenesis, including epidermal growth factor receptor, fibroblast growth factor receptor, platelet-derived growth factor receptor, Flk-1/KDR, Flt-1, Tie-1, and Tek/Tie-2. Flk-1/KDR, a receptor for vascular endothelial growth factor (VEGF), is expressed exclusively in endothelial cells. Using dominant-negative methods, Flk-1 was shown to play a role in angiogenesis and the growth of a variety of tumor types. Because of this, a drug discovery effort was established to identify Flk-1 kinase inhibitors. For initial screening, an ELISA in a 96-well format was used to measure VEGF-induced Flk-1 tyrosine phosphorylation in whole cells. Compounds that inhibited ligand-induced receptor autophosphorylation were confirmed by antiphosphotyrosine immunoblotting. Inhibition of VEGF-stimulated DNA synthesis in human endothelial cells was also assessed. Inhibitors were further evaluated for their effects on vessel formation using the chorioallantoic membrane assay. Using these methods, antiangogenesis compounds that inhibit Flk-1 tyrosine kinase activity, endothelial cell mitogenesis, and blood vessel formation in the chorioallantoic membrane assay have been found.

Endothelin-1 Production and Decreased Endothelin B Receptor Expression in Advanced Prostate Cancer

Abstract: The potent vasoconstrictor endothelin-1 (ET-1) is at its highest concentration in the normal human ejaculate and is associated with the progression of metastatic prostate cancer. ET-1 protein expression is detected in situ in 14 of 14 primary cancers and 14 of 16 metastatic sites of human prostatic carcinoma. Exogenous ET-1 induces prostate cancer proliferation directly and enhances the mitogenic effects of insulin-like growth factor I, insulin-like growth factor II, platelet-derived growth factor, basic fibroblast growth factor, and epidermal growth factor in serum-free conditions in vitro . The ETA-selective receptor antagonist A-127722 inhibits ET-1-stimulated growth, but the ETB-selective receptor antagonist BQ-788 does not. ET-3, an ETB-selective agonist, also had no effect on prostate cancer growth. No specific ETB-binding sites could be demonstrated in any established human prostate cancer cell line tested, and ETB mRNA, detected by reverse transcription PCR, was reduced. The predominance of ETB binding on human benign prostatic epithelial tissue is not present in metastatic prostate cancer by autoradiography. In human prostate cancer progression to metastases, ET-1 and ETA expression are retained, whereas ETB receptor expression is reduced.

Flt-1 but not KDR/Flk-1 tyrosine kinase is a receptor for placenta growth factor, which is related to vascular endothelial growth factor

Abstract: Placenta Growth Factor (PIGF) is a new member of vascular endothelial growth factor (VEGF) family. Although VEGF binds Flt family Flt-1 and KDR/Flk-1 tyrosine kinases at high affinity for signal transduction, biological activities and the receptors of PIGF have not been extensively studied. Reverse transcription-PCR showed that PIGF-2, a subtype of PIGF-1 that bears a basic amino acid-rich domain, is more abundant than PIGF-1 and thus is the major subtype in human placenta. Using antibodies specific to PIGF-1 or -2 as markers, we obtained large amounts of PIGFs in the baculovirus expression system. PIGF-2 had growth-stimulatory activity on human umbilical vein endothelial cells and vascular permeability activity in the Miles assay at levels about 10-fold lower than those of VEGF. All PIGF-1 activities were lower than those of PIGF-2. Both PIGFs competed for the binding of 125I-labeled VEGF to Flt-1 receptor but not to KDR/Flk-1 expressed on NIH3T3 cells. Furthermore, 125I-labeled PIGF bound to Flt-1 at high affinity but not to KDR/Flk-1. Supporting the notion that PIGF can use only Flt-1 as a receptor, PIGF activated Flt-1 to autophosphorylate, whereas PIGF could not generate signals from KDR/Flk-1. These results indicate that Flt-1, but not KDR/Flk-1, is a receptor for PIGF, suggesting that the weak biological activities of PIGF are due to its use of only part of the available VEGF signaling. These mild characteristics of PIGF may be important for the appropriate development and maintenance of normal placental tissue.

The Role of the Insulin-like Growth Factor System in Human Cancer

Abstract: Publisher Summary This chapter focuses on the role of the insulin-like growth factor system in human cancer. The normal process of growth and differentiation results from the genetically programmed action of a number of different cellular and extracellular factors. Derangement in the function of one or more of those agents can result in a pathologic phenotype, including neoplastic growth. A family of growth factors shown to be intimately involved in the regulation of cell growth as well as in cellular transformation is the insulin-like growth factor (IGF) family. IGF-I and IGF-II are mitogenic polypeptides produced in the largest amounts by the liver and secreted into the circulation, where they mediate the effects of growth hormone (GH) on longitudinal growth. In addition to ligands and receptors, the IGF system comprises a third category of molecules, which bind IGFs in the circulation and in extracellular compartments. Six IGF-binding proteins (IGFBPs) have been characterized to date. Binding of IGFs to the IGF-I receptor induces receptor autophosphorylation. The cell cycle consists of four major phases: (1) the presynthetic phase, G; (2) the phase of DNA synthesis, S; (3) the premitotic phase, G; and (4) mitosis, M. IGF-I, IGF-II, and insulin are chemotactic agents for the human melanoma cell line A2058, as assayed in a modified Boyden chamber. The chapter also gives selected examples of IGF involvement in human cancer. The wealth of information generated in the IGF field, as well as continued research efforts, both basic and clinic, promise to produce rational therapeutic approaches for those cancers in which the IGF system is involved.

Regulation of prostatic growth and function by peptide growth factors.

Abstract: Polypeptide growth factors are positive and negative regulators of prostatic growth and function. Expression and biological effects of epidermal growth factor (EGF), transforming growth factors (TGFs) alpha and beta, fibroblast growth factors (FGFs), and insulin-like growth factors (IGFs) in the prostate have been extensively studied. EGF and TGF alpha, which share the same receptor, are strong mitogens for prostatic epithelial and stromal cells. Their paracrine mode of action in normal tissue and early-stage tumors is apparently altered towards an autocrine stimulation in hormone-independent tumors, which gain the ability to produce TGF alpha by themselves. TGF beta has a dual role in the regulation of prostatic growth. It inhibits growth of prostatic epithelial cells in culture and mediates programmed cell death after androgen withdrawal. However, advanced prostatic carcinomas become insensitive to the inhibitory effect of TGF beta. Several members of the FGF family have been identified in the prostate. They are mainly or exclusively expressed in the stromal cells, and stimulate the epithelial cells. In the rat Dunning tumor model, progression is accompanied by distinct changes in the expression of FGFs and their receptors. In the hyperplastic tissue, basic FGF (bFGF) is accumulated. This growth factor is also a potent angiogenic inducer, expression of which may determine the metastatic capability of a tumor. IGFs are paracrine growth stimulators in the normal and hyperplastic prostate. It is still under consideration whether prostatic cancer cells gain the ability to produce IGF-I by themselves and thus shift to an autocrine mode of IGF-I stimulation. Growth factors also interact with the androgen-signaling pathway. IGF-I in particular, other growth factors as well, can activate the androgen receptor.

Anti-epidermal growth factor receptor monoclonal antibody 225 up-regulates p27KIP1 and induces G1 arrest in prostatic cancer cell line DU145.

Abstract: Autocrine production of transforming growth factor α and overexpression of the epidermal growth factor receptor (EGFR) may contribute to androgen-independent prostatic cancer growth at both primary and metastatic sites Previously, we showed that human EGFR-blocking monoclonal antibody mAb225 inhibited the growth of DU145 human prostatic cancer cells Here we explore the hypothesis that mAb225 may act by interfering with cell cycle traversal in these cells Treatment with mAb225 induced G 1 arrest, which was accompanied by a marked decrease in CDK2-, cyclin A-, and cyclin E-associated histone H1 kinase activities, and a sustained increase in cell cycle inhibitor p27 KIP1 The increased p27 KIP1 levels were attributable to elevation of both transcription and translation CDK2 associated with p27 KIP1 was increased in mAb225-treated DU145 cells The retinoblastoma-related protein p130 remained hypophosphorylated in these retinoblastoma-negative cells These studies demonstrate that the antiproliferative effect of EGFR blockade in DU145 cells may be mediated by up-regulation of p27 KIP1 at both the mRNA and protein levels

Growth control of lung cancer by interruption of 5-lipoxygenase-mediated growth factor signaling.

Abstract: Signal transduction pathways shared by different autocrine growth factors may provide an efficient approach to accomplish clinically significant control of lung cancer growth. In this study, we demonstrate that two autocrine growth factors activate 5-lipoxygenase action of the arachidonic acid metabolic pathway in lung cancer cell lines. Both growth factors increased the production of 5(S)-hydrooxyeicosa-6E,8Z,11Z,14Z-tetraeno ic acid (5-HETE), a major early 5-lipoxygenase metabolic product. Exogenously added 5-HETE stimulated lung cancer cell growth in vitro. Inhibition of 5-lipoxygenase metabolism by selective antagonists resulted in significant growth reduction for a number of lung cancer cell lines. Primary clinical specimens and lung cancer cell lines express the message for the 5-lipoxygenase enzymes responsible for the generation of active metabolites. In vivo evaluation demonstrated that interruption of 5-lipoxygenase signaling resulted in enhanced levels of programmed cell death. These findings demonstrate that 5-lipoxygenase activation is involved with growth factor-mediated growth stimulation for lung cancer cell lines. Pharmacological intervention with lipoxygenase inhibitors may be an important new clinical strategy to regulate growth factor-dependent stages of lung carcinogenesis.

Betacellulin activates the epidermal growth factor receptor and erbB-4, and induces cellular response patterns distinct from those stimulated by epidermal growth factor or neuregulin-beta.

Abstract: Betacellulin is a member of the epidermal growth factor (EGF) family. These soluble proteins are ligands for one or more of the four receptor tyrosine kinases encoded by the erbB gene family (erbB-1/epidermal growth factor receptor (EGFR), neu/erbB-2/HER2, erbB-3/HER3 and erbB-4/HER4). While evidence suggests that betacellulin is a ligand for the EGFR, the ability of betacellulin to regulate other erbB family receptors has not been analysed. Previously we engineered derivatives of the mouse Ba/F3 hematopoietic cell line to ectopically express erbB family receptors, singly and in pairwise combinations. We have stimulated this panel of cell lines with betacellulin and two other EGF family members, EGF itself and neuregulin-beta (NRG-beta). In the cell lines expressing a single erbB family receptor, betacellulin not only stimulated EGFR tyrosine phosphorylation, but it activated erbB-4 as well. Furthermore, in the double recombinant Ba/F3 derivatives, betacellulin stimulated a complex pattern of receptor phosphorylation distinct from the patterns activated by NRG-beta and EGF. Moreover, betacellulin stimulated a complex pattern of interleukin-3 independence in the Ba/F3 derivatives distinct from those activated by NRG-beta and EGF. These data identify a novel receptor for betacellulin and establish that different EGF family ligands activate distinct patterns of receptor phosphorylation and coupling to cellular signaling pathways.

Significance of Vessel Count and Vascular Endothelial Growth Factor and Its Receptor (KDR) in Intestinal-type Gastric Cancer'

Abstract: Angiogenesis is essential for tumor growth and metastasis and depends on the production of angiogenic factors by host and/or tumor cells. The role of angiogenesis and angiogenic factor expression in intestinal- and diffuse-type gastric cancer are undefined. Archival specimens of 51 intestinal-type and 38 diffuse-type human gastric carcinomas were examined for tumor vessel counts, angiogenic factor expression, and the presence or absence of angiogenic factor receptors on tumor endothelium using antibodies against vascular endothelial growth factor (VEGF) and its receptors (KDR and flt-1), basic fibroblast growth factor (bFGF) and its receptors (bek and flg), and factor VIII (endothelial cells). Vessel count and VEGF and bFGF expression were higher in intestinal-type than in diffuse-type gastric cancers (P = 0.01, P < 0.001, and P < 0.001, respectively). Similarly, vessel count and VEGF expression were higher in patients with liver metastasis than in patients with peritoneal dissemination (P = 0.003 and P = 0.01, respectively). Vessel count correlated with VEGF expression and the presence of endothelial KDR in intestinal-type gastric cancer (P = 0.003 and P = 0.02, respectively) but not diffuse-type gastric cancer. Vessel count, VEGF expression, and presence of endothelial KDR increased with increasing stage of disease in intestinal-type gastric cancer but not diffuse-type gastric cancer. The expression of bFGF and its receptors did not correlate with vessel count in either cancer type. These findings suggest that the pattern of metastasis in intestinal-type gastric cancer is angiogenesis dependent. The correlation of VEGF expression and its endothelial receptor with vessel count and stage of disease suggests that VEGF is at least one of the factors responsible for the induction of angiogenesis in intestinal-type gastric cancer.

Enhanced expression of vascular endothelial growth factor in human SaOS-2 osteoblast-like cells and murine osteoblasts induced by insulin-like growth factor I.

Abstract: Formation of new capillaries, a critical component of tissue growth and repair, is a recognized process in the development, formation, and remodeling of bone. Vascular endothelial growth factor (VEGF), a potent angiogenic factor with specific mitogenic actions on endothelial cells, is produced in a regulated manner by many cell types, including osteoblasts. The aim of the present investigation was to test the hypothesis that insulin-like growth factor I (IGF-I), a known osteogenic factor, modulates VEGF expression in osteoblasts. In human SaOS-2 osteoblast-like cells, 10 nM IGF-I increased the abundance of VEGF messenger RNA (mRNA) by 4-fold above the control value at 2h, and the elevated levels of mRNA returned to near basal by 8 h. IGF-I stimulated VEGF mRNA levels at IGF-I concentrations as low as 1-2 nM. The stability of VEGF mRNA was not increased after IGF-I treatment, and actinomycin D abrogated the enhanced expression of VEGF mRNA by IGF-I, indicating that the action of IGF-I was probably mediated...

Vein is a novel component in the Drosophila epidermal growth factor receptor pathway with similarity to the neuregulins.

Abstract: The activation signal from tyrosine kinase receptors, such as the epidermal growth factor receptor (EGFR), is relayed via a highly conserved intracellular pathway involving Ras, Raf, and MAPK. In Drosophila, the EGFR and components of the intracellular pathway are broadly expressed, yet receptor activation evokes tissue-specific cell responses. Extracellular events that lead to receptor activation are one mechanism by which signaling is modulated. Here we show molecular and genetic evidence that Drosophila vein (vn) encodes a candidate EGFR ligand and that vn expression is spatially restricted. Consequently, vn may promote tissue-specific receptor activation. Unlike two other ligands, Gurken (Grk) and Spitz (Spi), which are transforming growth factor alpha-like proteins, Vn has both an immunoglobulin-like and an EGF-like domain. This combination of domains mirrors those in the vertebrate neuregulins that bind EGFR relatives.

Method and reagent for the treatment of diseases or conditions related to levels of vascular endothelial growth factor receptor

Abstract: Nucleic acid molecule which modulates the synthesis, expression and/or stability of an mRNA encoding one or more receptors of vascular endothelial growth factor.

Liver regeneration versus direct hyperplasia.

Abstract: Liver cell growth can be induced in two distinct patterns: compensatory regeneration and direct hyperplasia. In the former, DNA synthesis is preceded by a loss of liver cells such as seen after partial resection of the liver or cell necrosis, whereas in direct hyperplasia, DNA synthesis is stimulated without cell loss. During the past decade, considerable advances have been made in understanding molecular mechanisms of the compensatory regeneration. There is increasing evidence that hepatocyte proliferation induced by some primary mitogens is mediated by patterns of growth factor modulation and signal transduction different from those of compensatory regeneration. Indeed, whereas activation of transcription factors such as NF-kappa B and increased expression of immediate early genes such as c-fos, c-jun, egr-1, and c-myc are induced during compensatory regeneration, such changes are not observed during hyperplasia induced by certain primary mitogens. In addition, although experimental evidence suggests a critical role for growth factors such as hepatocyte growth factor and transforming growth factor-alpha for the progression into cell cycle of competent hepatocytes in compensatory regeneration, these growth factors do not appear to play a major role in direct hyperplasia. One class of primary mitogens may trigger their actions through tumor necrosis factor-alpha, and the other by activation of nuclear hormone receptors. The differences in molecular events observed between liver regeneration and direct hyperplasia may affect differently the initiation step of chemical hepatocarcinogenesis. Whereas the former supports initiation by chemicals, the latter does not. A similar lack of effect on promotion of carcinogen-altered cells has also been observed after acute treatment with some primary mitogens. Definition of the mechanisms by which primary mitogens stimulate liver cell proliferation may elucidate the nature of the signals responsible for triggering the entry into cell cycle. Furthermore, due to their low toxicity, primary liver mitogens could have significant clinical applications in gene transfer and liver transplantation.

HIV-tat protein is a heparin-binding angiogenic growth factor.

Abstract: Transgenic animal studies have linked the expression of the HIV-1 tat gene to the appearance of Kaposi's sarcoma (KS)-like lesions. We have recently shown that recombinant tat is angiogenic in vivo, and that tat angiogenic response is enhanced by heparin. Also in the rabbit cornea model, recombinant HIV-1 tat alone is poorly angiogenic, but gives a good response when combined with heparin. Like many angiogenic growth factors, tat has a basic domain similar to that of several heparin binding angiogenic factors, including FGF, VEGF and HGF, suggesting that this region is important in endothelial cell activation. We show that tat binds heparin sepharose with a high affinity, similar to bFGF. Binding of tat to the cell surface is also modulated by heparin. Biological activities of tat, such as induction of endothelial cell growth, migration and invasion in vitro are all enhanced by low concentrations and inhibited by high concentrations of heparin, as has been shown for other heparin-binding angiogenic factors. Heparan sulfate is also effective, whereas the unsulfated polysaccharide K5 does not enhance tat activity. Furthermore, a peptide encompassing the tat basic domain is able to induce growth and migration of endothelial cells, while an adjacent peptide is not. Our data indicate that the tat basic domain plays a key role in its vascular cell activation properties, and strongly suggest that extracellular HIV-tat is essentially a 'new' heparin-binding angiogenic factor.

Antitumor Activity of Combined Blockade of Epidermal Growth Factor Receptor and Protein Kinase A

Abstract: BACKGROUND Epidermal growth factor (EGF)-related proteins, such as transforming growth factor-alpha (TGF-alpha), control cancer cell growth through hormonal pathways (i.e., autocrine [hormone acts on cell that produces it] and paracrine [hormone acts on nearby cells] pathways). Overexpression of TGF-alpha and/or its receptor (EGFR) has been detected in human cancers. The blockade of EGFR activation by the use of anti-EGFR monoclonal antibodies (MAbs) has been proposed as a potential anticancer therapy. The type I cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKAI) is generally overexpressed in human cancer cells and is involved in neoplastic transformation. Inhibition of PKAI by selective cAMP analogues, such as 8-chloro-cAMP (8-CI-cAMP), induces growth inhibition in various human cancer cell lines. PURPOSE On the basis of our previous observations of a cooperative anti-proliferative effect of anti-EGFR Mab 528 and 8-Cl-cAMP in human cancer cell lines in vitro, we evaluated the anticancer activity in vivo of the combination of an anti-EGFR MAb (MAb C225) and 8-Cl-cAMP. METHODS Athymic mice were injected subcutaneously with 10(7) human colon carcinoma GEO cells. After 7 days, when established tumor xenografts of 0.30-0.35 cm3 were detectable, 10-15 mice per group were treated intraperitoneally twice weekly with different doses of 8-Cl-cAMP and/or MAb C225. Cancer cell expression of various growth factors was evaluated by immunohistochemical analysis in tumors obtained from control and treated mice. Data were evaluated for statistical significance using the Student's t test and the Mantel-Cox logrank test. All P values represent two-sided tests of statistical significance. RESULTS A 5-week treatment with low doses of 8-Cl-cAMP (0.5 mg/dose) and MAb C225 (0.25 mg/dose) blocked GEO tumor growth (compared with that in control mice; P < .00001) and suppressed cancer cell production of autocrine growth factors, such as TGF-alpha, amphiregulin, and CRIPTO, and of angiogenic (promotes new blood vessel formation) factors, such as vascular endothelial growth factor and basic fibroblast growth factor, with no signs of toxicity. Control and 8-Cl-cAMP (0.5 mg/dose)-treated mice died within 9-10 weeks after tumor cell injection. In MAb C225 (0.25 mg/dose)-treated mice, GEO tumors resumed a growth rate comparable to that in control animals within 3 weeks following the end of treatment and the mice died between 11 and 20 weeks after tumor cell injection. GEO tumor growth was significantly delayed in the MAb C225 plus 8-Cl-cAMP treatment group (P < .00001) and was accompanied by a prolonged survival of mice (P < .00001) as compared with the control group. CONCLUSIONS Long-term treatment with a combination of agents that selectively inhibit two intracellular signal-transduction enzymes, such as the PKAI serine-threonine kinase and the EGFR tyrosine kinase, has anticancer activity in vivo, reflected by suppression of tumor proliferation and angiogenesis, with no signs of toxicity. IMPLICATIONS Since these inhibitors of intracellular mitogenic (growth-stimulating) signaling have a different mechanism(s) of action and do not antagonize the effects of cytotoxic therapy, a combination of anti-EGFR MAb C225 and 8-Cl-cAMP should be investigated as a nontoxic, long-term treatment for cancer patients following chemotherapy.

p75NTR: A Receptor After All

Abstract: One of the first growth factor receptors to be cloned, p75NTR was supplanted by newer molecules that bind nerve growth factor (NGF). Now in a number of recent papers, including one in this issue of Science , p75NTR proves to be a receptor for NGF after all, with a specialized function in Schwann's cells. In his Perspective, Bothwell points out that signal transduction by p75NTR is in many ways similar to transduction by the tumor necrosis factor receptors, CD40, and Fas, which couple to both apoptotic cell death and the transcription factor NF-kappaB.

Interaction of angiogenic basic fibroblast growth factor with endothelial cell heparan sulfate proteoglycans. Biological implications in neovascularization.

Abstract: Basic fibroblast growth factor is an angiogenic molecule involved in several physiological and pathological processes, including wound repair, embryonic development, and tumor growth. In vitro, basic fibroblast growth factor induces an “angiogenic phenotype” in endothelial cells, which includes chemotaxis, mitogenesis, protease production, β-integrin expression, and tube formation in three-dimensional gels. It acts by binding to specific tryosine kinase receptors and to cell-associated heparan sulfate proteoglycans. The physiological significance of the interaction with cell-associated and soluble heparan sulfate proteoglycans is manyfold. Heparan sulfate proteoglycans protect basic fibroblast growth factor from inactivation in the extracellular environment and modulate its bioavailability. At the cell surface, soluble and cell-associated heparan sulfate proteoglycans may play different roles in modulating the dimerization of the growth factor and its interaction with tyrosine kinase receptors. Finally, they affect the internalization and the intracellular fate of basic fibroblast growth factor, suggesting that growth factor slash proteoglycan complexes are involved in intracellular delivery. The bioavailability and the biological activity of basic fibroblast growth factor on endothelial cells strictly depend on the glycosaminoglycan milieu of the extracellular environment. Hence the angiogenic activity of the growth factor in vivo might be modulated by using exogenous glycosaminoglycans. The capacity of glycosaminoglycans to bind to and to influence the biological activity of basic fibroblast growth factor depends on size, degree of sulfation, and disaccharide composition. In the present paper we discuss the physiological significance and the biochemical bases of the interaction of the growth factor with heparan sulfate proteoglycans and exogenous glycosaminoglycans with a view to the possible therapeutic use of heparin-related oligosaccharides as basic fibroblast growth factor agonists or antagonists in angiogenesis-dependent diseases.

Radiation-induced autophosphorylation of epidermal growth factor receptor in human malignant mammary and squamous epithelial cells.

Abstract: In an effort to identify events initiating up-regulation of epidermal growth factor receptor after single and repeated radiation exposures, we investigated the role of epidermal growth factor receptor, a receptor protein tyrosine kinase, in radiation-induced signal transduction. Human malignant mammary, MCF-7, and squamous, A431, cells showed low baseline phospho-tyrosine levels of epidermal growth factor receptor, permitting reproducible dose-dependent stimulation of epidermal growth factor receptor autophosphorylation after exposure to epidermal growth factor. MCF-7 cells exhibited a mean 2.3-fold increase (95% confidence interval: 1.91, 2.65; P < 0.0001) in levels of epidermal growth factor phosphorylation in response to exposures of 2 Gy, which was substantially less than the epidermal growth factor receptor Y phosphorylation induced by epidermal growth factor. A quantitatively similar radiation response was seen in A431 cells. In the dose range of 1 to 4 Gy, no clear dose response was seen. There was a rapid induction of radiation-induced epidermal growth factor receptor Y phosphorylation, starting within 2 min, with maximum values between 0.5 and 5 min after radiation exposure followed by a slower decline to baseline levels after 20 min. The data presented identify the epidermal growth factor receptor protein tyrosine kinase associated with the plasma membrane as one target for ionizing radiation in the dose range used in radiotherapy.

Fibroblast growth factor receptor 1-induced differentiation of endothelial cell line established from tsA58 large T transgenic mice.

Abstract: Angiogenesis of capillary endothelial cells includes at least four sequential cellular responses: digestion of basement membrane, migration, proliferation, and differentiation. To study differentiation of endothelial cells, we established a brain capillary endothelial cell line from H.2KbtsA58 transgenic mice. These cells are stable at 33#{176}C and display endothelial cell-specific characters, such as expression of von Willebrand factor and binding sites for the lectin Bandeiraea simpllfolla, and uptake of acetylated-low densfty lipoprotein. We measured the effects of a panel of growth factors on cellular responses. A number of factors, such as hepatocyte growth factor, vascular endothelial growth factor, and platelet-derived growth factor (PDGF)-AA failed to induce biological responses. PDGF-BB, epidermal growth factor, and acidic and basic fibroblast growth factor (FGF) induced proliferation of the cells. Of all the factors tested, only acidic FGF and basic FGF induced differentiation of the cells, visualized as the formation of tube-like structures of cells grown in three-dimensional collagen gels. All factors were also analyzed for their effects on plasminogen activator (PA)-induction and migration of the cells. Transfected cells, expressing a chimeric receptor, composed of the extracellular part from the