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PubMedDate not supplied

Effect of intraperitoneally, intravenously and intralesionally administered monoclonal anti-beta-FGF antibodies on rat chondrosarcoma tumor vascularization and growth.

The growth and vascularization of many tumours has been reported to be associated with the overexpression of the potent mitogenic and angiogenic polypeptide basic fibroblast growth factor (beta-FGF). Consequently, it has been proposed that inhibition of beta-FGF action would prevent the growth of beta-FGF-dependent tumours. In this study, cell culture assays were established to assess the ability of mouse monoclonal DG-2 anti-beta-FGF antibodies to inhibit the mitogenic action of beta-FGF in vitro. Following in vitro characterisation, the monoclonal DG-2 antibodies were used to evaluate the role of beta-FGF in promoting the vascularization and growth of rat chondrosarcoma tumours. The effect the monoclonal anti-B-FGF antibodies had on tumour vascularization and growth in vivo were monitored using a 99m Technetium (99mTc)-labelled red blood cell procedure. The characterization studies confirmed that the DG-2 monoclonal antibody recognised beta-FGF and inhibited its mitogenic action on mouse Balb/c cells and bovine endothelial cells in vitro. When examined in vivo, intralesional administration of mouse monoclonal DG-2 antibody significantly inhibited rat chondrosarcoma growth and vascularization. However when the monoclonal DG-2 antibody was administered intraperitoneally or intravenously no attenuation of rat chondrosarcoma tumour vascularization or growth was observed. This report has confirmed the potential effectiveness of anti-beta-FGF antibodies in the regulation of tumour growth. It has also demonstrated that further studies on the pharmacokinetics of administered antibodies and their mode of delivery are required so that the effectiveness of such anti-growth factor immunotherapy can be assured.

3T3 Cells↗
PubMed1998

Human FGF-1 gene delivery protects against quinolinate-induced striatal and hippocampal injury in neonatal rats.

Fibroblast growth factors (FGFs) are cell mitogens and differentiating factors with neuroprotective properties in the CNS. We have already shown that endothelial cells genetically engineered to secrete human FGF-1 (RBEZ-FGF) survive implantation to neonatal rat brain (Johnston et al. (1996) J. Neurochem. 67, 1643-1652]. In this study, the effects of cell-based FGF-1 gene delivery on quinolinate-induced neurotoxicity in the developing rat brain were examined. Control endothelial cells (RBE4), and RBEZ-FGF cells were implanted into right striatum at post-natal day (PND) 7. On PND 10, quinolinate (150 nmol), an endogenous N-methyl-d-aspartate (NMDA) receptor agonist, or vehicle alone was injected into striatum ipsilateral to cell implantation. Injury was quantified in coronal sections obtained from PND 17 animals by comparing striatal and hippocampal volumes ipsilateral and contralateral to the site of quinolinate injection. Human FGF-1 specific transgene expression in vivo was shown by Northern blot and RT-PCR up to 14 days after cell implantation in control animals, and up to 4 days after quinolinate exposure. Quinolinate reduced the size of ipsilateral striatum by 37% and hippocampus by 38% in animals preimplanted with control endothelial cells. In contrast, quinolinate reduced the size of striatum by only 14% and had no effect on hippocampal size in animals preimplanted with RBEZ-FGF cells. Thus, FGF-1 gene delivery protected the developing striatum and hippocampus from quinolinate-induced volume loss by 62% and 100%, respectively. Intrastriatal quinolinate resulted in a significant decrease in density of NOS+ CA3 hippocampal neurons (-38%) without affecting the density of NOS+ neurons in hippocampal regions CA1, dentate gyrus or striatum. This response of CA3 NOS+ neurons appeared to be only partially reversed by FGF-1 gene delivery. Our results show that intracerebral FGF-1 gene expression within the developing brain can protect striatum and hippocampus from quinolinate-mediated injury.

Animals↗
PubMed1997

FGF-2 converts mature oligodendrocytes to a novel phenotype.

Fibroblast growth factor (FGF)-2 differentially regulates oligodendrocyte progenitor proliferation and differentiation in culture, and modulates gene expression of its own receptors, in a developmental and receptor type-specific manner (Bansal et al., 1996a,b). Three FGF receptors (types 1, 2, 3) are expressed in postmitotic, terminally differentiating oligodendrocytes. Exposure of such cells to FGF-2 results in: (a) the down-regulation of myelin-specific gene expression (e.g., ceramide galactosyltransferase, 2',3'-cyclic nucleotide 3'-phosphohydrolase, myelin basic protein, proteolipid protein), (b) dramatic increases in the length of cellular processes in a time- and dose-dependent manner, (c) re-entrance into the cell cycle without accompanying mitosis, and (d) the alteration of the expression of both low- and high-affinity FGF receptors. Compared to oligodendrocyte progenitors, the differentiated oligodendrocytes treated with FGF-2 incorporate BrdU at a slower rates, exhibit different patterns of both FGF high- and low-affinity (syndecans) receptors, and are morphologically very different. In addition, they do not re-express the progenitor markers A2B5, NG2 or PDGFalpha receptor. Therefore, although the FGF-treated cells lose their differentiated OL/myelin markers, they do not revert to progenitors and clearly represent a different, apparently novel, phenotype both morphologically and biochemically, which we have termed NOLs. These data indicate that terminally differentiated oligodendrocytes retain the plasticity to reprogram their differentiation fate under the influence of environmental factors. The possible significance of this response to FGF relative to normal and pathological physiology is discussed. In particular, on the basis of these data we predict the appearance of cells in and around multiple sclerosis plaques with the phenotype O4+, NG2-, A2B5-, O1-, MBP-.

Animals↗
PubMed1998

Regulation of astrocyte GFAP expression by TGF-beta1 and FGF-2.

Astrocytes play a critical role in the development of the CNS and its response to injury and disease. A key indicator of astrocyte activation is the increased accumulation of intermediate filaments composed of glial fibrillary acidic protein (GFAP). Treatment of astrocytes in vitro with transforming growth factor-beta1 (TGF-beta1) produced little morphological change, but resulted in a significant increase in GFAP mRNA and protein. Treatment with basic fibroblast growth factor (FGF-2) produced a dramatic change from a polygonal to a stellate morphology, and resulted in a significant decrease in GFAP mRNA and protein. FGF-2 also inhibited the TGF-beta1-mediated increase in GFAP mRNA and protein. Cycloheximide did not block the effects of TGF-beta1 or FGF-2 on GFAP mRNA levels, but blocked the inhibitory effects of FGF-2 on the TGF-beta1-mediated increase in GFAP expression. All effects of FGF-2 were blocked by co-incubation with 5'-methylthioadenosine, a specific inhibitor of FGF-2-induced tyrosine kinase activity and FGF receptor (FGFR) autophosphorylation. We also examined astrocyte expression of FGFR, and demonstrate the presence of FGFR 1 and 2, and lower levels of FGFR 3. Our results demonstrate that TGF-beta1 and FGF-2 cause differential effects on the astrocyte cytoskeleton and morphology, suggesting an uncoupling of process outgrowth from GFAP synthesis.

Animals↗
PubMed1998

Effects of differentiation on the transcriptional regulation of the FGF-4 gene: critical roles played by a distal enhancer.

Embryonal carcinoma (EC) cells are used widely as a model system for studying the expression of developmentally regulated genes, in particular genes that are regulated at the transcriptional level when EC cells differentiate. This review focuses on the molecular mechanisms that govern the transcription of the fibroblast growth factor-4 (FGF-4) gene, which appears to be the first FGF expressed during mammalian development. Interest in this gene has increased considerably with the finding that FGF-4 is essential for mammalian embryogenesis. The FGF-4 gene has also generated considerable interest because it is inhibited at the transcriptional level when EC cells undergo differentiation and because this gene is regulated by a powerful distal enhancer located 3 kb downstream of the transcription start site in the last exon of the gene. Hence, study of the FGF-4 gene is likely to shed light on the molecular mechanisms by which distal enhancers regulate gene expression. In addition to being regulated by the downstream enhancer, the expression of this gene is influenced by a regulatory region located just upstream of the transcription start site, which contains two Sp1 motifs and a CCAAT box motif. Examination of the downstream enhancer has identified three functional cis-regulatory elements: a high mobility group (HMG) protein binding motif, an octamer binding motif, and an Sp1 motif, which are likely to bind Sox-2, Oct-3, and Sp1/Sp3, respectively, in vivo. Interestingly, Sox-2 and Oct-3 expression, like FGF-4 expression, decreases when EC cells differentiate, which suggests that the loss of these transcription factors is responsible, at least in part, for the transcriptional turn-off of the FGF-4 gene. In view of these and other findings, we present a model for the differential expression of the FGF-4 gene that includes not only the contributions of specific transcription factors, but also the contribution of chromatin structure before and after differentiation.

Animals↗
PubMed2000

Autocrine effect of DHT on FGF signaling and cell proliferation in LNCaP cells: role of heparin/heparan-degrading enzymes.

BACKGROUND: LNCaP cells are androgen-sensitive human prostate cancer cells. They are characterized by a bell-shaped growth curve in response to increasing doses of dihydrotestosterone (DHT) in culture. At a low concentration of DHT (0.1 nM), these cells show an increase in proliferation, but their growth is arrested at a high concentration (100 nM) of DHT. Results of our previous study demonstrated that the inhibitory effect of DHT at a high concentration was mediated through the action of TGF-beta1. The objective of the present study was to elucidate the mechanism of the proliferative effect of DHT in LNCaP cells. METHODS AND RESULTS DHT stimulated LNCaP proliferation only when cells were cultured in the presence of serum. In serum-free cultures, the characteristic DHT-induced proliferation was not observed. The addition of neutralizing antibody against FGF-2 (basic fibroblast growth factor) was able to inhibit this DHT-induced proliferation. These results suggest that the proliferative effect of DHT was mediated through the action of FGF-2. However, results of the reverse transcriptase polymerase chain reaction indicated that LNCaP cells did not express FGF-2 message. As a result, the source of FGF-2 in these cultures must be the serum supplemented in the culture media. FGF-2 can bind to heparin sulfate chains within the extracellular matrix (ECM). In cultures treated with exogenous heparin, the proliferative effect of DHT was abolished. These results led to the development of the hypothesis that DHT treatment mediates the release of FGF-2 entrapped in the ECM through increased heparinase activity. The addition of heparinase to cultures of LNCaP cells, in the absence of DHT, was able to stimulate cell proliferation. Moreover, 0.1 nM DHT caused a significant increase in heparinase activity. CONCLUSIONS: These results provide a possible mechanism for DHT action in LNCaP cells. In the absence of DHT, FGF-2 in culture was trapped in the extracellular matrix and was not available to interact with LNCaP cells. However, in the presence of 0.1 nM DHT, heparinase activity in the culture was elevated and, as a result, it liberated the trapped FGF-2 which, in turn, stimulated proliferation in LNCaP cells.

Cell Division↗
PubMed2006

Differential regulation of GDF-5 and FGF-2/4 by immobilisation in ovo exposes distinct roles in joint formation.

Members of the fibroblast growth factor (FGF) family and growth and differentiation factor 5 (GDF-5) have been implicated in joint specification, but their roles in subsequent cavity formation are not defined. Cavity formation (cavitation) depends upon limb movement in embryonic chicks and factors involved in joint formation are often identified by their expression at the joint-line. We have sought support for the roles of FGF-2, FGF-4, and GDF-5 in cavitation by defining expression patterns, immunohistochemically, during joint formation and establishing whether these are modified by in ovo immobilisation. We found that FGF-2 exhibited low level nuclear expression in chondrocytes and fibrocartilage cells close to presumptive joints, but showed significantly higher expression levels in cells at, and directly bordering, the forming joint cavity. This high-level joint line FGF-2 expression was selectively diminished in immobilised limbs. In contrast, we show that FGF-4 does not exhibit differential joint-line expression and was unaffected by immobilisation. GDF-5 protein also failed to show joint-line selective labelling, and although immobilisation induced a cartilaginous fusion across presumptive joints, it did not affect cellular GDF-5 expression patterns. Examining changes in GDF-5 expression in response to a direct mechanical strain stimulus in primary embryonic chick articular surface (AS) cells in vitro discloses only small mechanically-induced reductions in GDF-5 expression, suggesting that GDF-5 does not exert a direct positive contribution to the mechano-dependent joint cavitation process. This notion was supported by retroviral overexpression of UDPGD, a characteristic factor involved in hyaluronan (HA) accumulation at presumptive joint lines, which was also found to produce small decreases in AS cell GDF-5 expression. These findings support a direct mechano-dependent role for FGF-2, but not FGF-4, in the cavitation process and indicate that GDF-5 is likely to influence chondrogenesis positively without contributing directly to joint cavity formation.

Animals↗
PubMed1994

FGF-2 in the MPTP model of Parkinson's disease: effects on astroglial cells.

Fibroblast growth factor (FGF) is synthesized and stored by astroglial cells and regulates their proliferation and differentiation in vitro. Its implication in the transformation of quiescent astrocytes into reactive astroglia has been discussed. Using a mouse model of Parkinson's disease, in which FGF-2 has been shown to exert marked neuroprotection of nigrostriatal dopaminergic neurons, we have studied striatal levels of glial fibrillary acidic protein (GFAP), an established marker for astrocytes, and the distribution and morphologies of GFAP-immunoreactive cells following treatments with the neurotoxic drug 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), the growth factor FGF-2, and the non-trophic control protein cytochrome C (cyt C). Systemic injections of MPTP (30 mg/kg) on 3 consecutive days, which we have previously shown to cause profound and long-lasting damage to the nigrostriatal system, induced an approximate 20% transient increase in striatal GFAP, determined by enzyme-linked immunosorbent assay (ELISA), 1 day after the final MPTP injection (= day 4), with subsequent normalization at day 7, which lasted until the end of the experiment (day 18). Morphologically, MPTP elicited a marked increase in number, size, arborization, and stainability of GFAP-immunoreactive cells at day 4 in a striatal area adjacent to the corpus callosum, which was evaluated throughout all experiments. Even on day 18, astrocytes were still apparently larger and more branched than in unlesioned controls. Administration of 4 micrograms of either FGF-2 or cyt C (soaked into a piece of Gelfoam unilaterally to the right striatum in either MPTP- or saline-injected controls) increased striatal GFAP levels bilaterally about 2- to 2.5-fold at 14 days, when FGF-2 showed marked protection of dopaminergic parameters. Likewise, GFAP immunocytochemistry revealed increased numbers of intensely immunoreactive astrocytes under any experimental situation. Differences in the morphologies of astrocytes in FGF-2- and cyt C-treated animals were very subtle and only noted at greater distances away from the site of application of the factors. We conclude that FGF-2, a potent neurotrophic factor for the neurotoxically lesioned nigrostriatal system, does not cause a marked astrogliotic reaction, which might be expected from previous in vitro and in vivo studies in other neural systems. This may limit concerns regarding potential applicability of FGF-2 to the parkinsonian striatum.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2005

Identification of c-Jun as a critical mediator for the intracrine 24 kDa FGF-2 isoform-induced cell proliferation.

Tumor cells frequently synthesize an N-terminally extended the FGF-2 isoform of 24 kDa devoid of signal peptide but that contains a functional nuclear localization sequence (NLS). Although the signaling pathways elicited by secreted FGF-2 are well described, the molecular mechanisms involved in the growth promoting action of nuclearized 24 kDa FGF-2 remain unknown. The cancer cell line AR4-2J was engineered to stably express only the 24 kDa FGF-2 isoform and cDNA microarrays were used to identify targets implicated in the intracrine-induced cell proliferation. Levels of 27 transcripts were found either upregulated or downregulated compared to control cells. Among the 18 upregulated genes was c-jun, which is often involved in cell proliferation. Real-time PCR and Western blot analyses confirmed c-jun induction at both mRNA and protein levels. The c-jun antisense oligonucleotide strategy pointed out the involvement of c-Jun in the 24 kDa FGF-2-induced cell proliferation. The mitogenic effect was found to depend on ERK pathway and not on phosphoinositide 3-kinase, p38 MAPK, c-Jun NH2-terminal kinase signal transducers. In addition, the MEK inhibitor PD98059 reduced the 24 kDa FGF-2-dependent c-Jun level. These data show that intracrine FGF-2-mediated regulation of cell growth involves ERK activation and consequent c-Jun expression. Thus, despite its incapacity to be secreted, the intracellular-localized 24 kDa FGF-2 can activate a growth-related signaling pathway normally elicited by cell surface receptors.

Animals↗
PubMed2001

Response of bovine endothelial cells to FGF-2 and VEGF is dependent on their site of origin: Relevance to the regulation of angiogenesis.

Angiogenesis, the formation of new capillary blood vessels, occurs almost exclusively in the microcirculation. This process is controlled by the interaction between factors with positive and negative regulatory activity. In this study, we have compared the effect of two well described positive regulators, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF-2) on bovine adrenal cortex-derived microvascular endothelial (BME) and bovine aortic endothelial (BAE) cells. The parameters we assessed included (a) cellular reorganization and lumen formation following exposure of the apical cell surface to a three-dimensional collagen gel; (b) organization of the actin cytoskeleton; (c) expression of thrombospondin-1 (TSP-1), an endogenous negative regulator of angiogenesis; and (d) extracellular proteolytic activity mediated by the plasminogen activator (PA)/plasmin system. We found that (a) collagen gel overlay induces rapid reorganization and lumen formation in BME but not BAE cells; (b) FGF-2 but not VEGF induced dramatic reorganization of actin microfilaments in BME cells, with neither cytokine affecting BAE cells; (c) FGF-2 decreased TSP-1 protein and mRNA expression in BME cells, an effect which was specific for FGF-2 and BME cells, since TSP-1 protein levels were unaffected by VEGF in BME cells, or by FGF-2 or VEGF in BAE cells; (d) FGF-2 induced urokinase-type PA (uPA) in BME and BAE cells, while VEGF induced uPA and tissue-type PA in BME cells with no effect on BAE cells. Taken together, these findings reveal endothelial cell-type specific responses to FGF-2 and VEGF, and point to the greater specificity of these cytokines for endothelial cells of the microvasculature than for large vessel (aortic) endothelial cells. Furthermore, when viewed in the context of our previous observation on the synergistic interaction between VEGF and FGF-2, our present findings provide evidence for complementary mechanisms which, when acting in concert, might account for the synergistic effect.

Animals↗
PubMed2005

Role of AKT/PKB signaling in fibroblast growth factor-1 (FGF-1)-induced angiogenesis in the chicken chorioallantoic membrane (CAM).

Transfection of chicken chorioallantoic membranes (CAMs) with a chimeric secreted version of fibroblast growth factor-1 (sp-FGF-1) gene construct leads to a significant increase in vascularization. Though FGF-stimulated angiogenesis has been extensively studied, the molecular mechanisms regulating FGF-1-induced angiogenesis are poorly understood in vivo. This study was designed to investigate the role of the AKT (PKB) kinase signaling pathway in mediating sp-FGF-1-induced angiogenesis in the chicken CAM. The involvement of the AKT pathway was demonstrated by up-regulation of AKT1 mRNA expression in sp-FGF-1 compared to vector alone control transfected CAMs as demonstrated by real-time RT-PCR. Western analysis using an antibody specific to the activated AKT (phosphorylated AKT), demonstrated an increase in AKT activity in sp-FGF-1 compared to vector control transfected CAMs. More importantly, the AKT inhibitor ML-9 significantly reduced sp-FGF-1-induced angiogenesis in CAMs. These results indicate that AKT signaling plays a role in FGF-1-stimulated angiogenesis in vivo and the AKT pathway may serve as a therapeutic target for angiogenesis-associated diseases.

Animals↗
PubMed2005

PDGF-BB induces vascular smooth muscle cell expression of high molecular weight FGF-2, which accumulates in the nucleus.

Basic fibroblast growth factor (FGF-2) and platelet-derived growth factor (PDGF) are implicated in vascular remodeling secondary to injury. Both growth factors control vascular endothelial and smooth muscle cell proliferation, migration, and survival through overlapping intracellular signaling pathways. In vascular smooth muscle cells PDGF-BB induces FGF-2 expression. However, the effect of PDGF on the different forms of FGF-2 has not been elucidated. Here, we report that treatment of vascular aortic smooth muscle cells with PDGF-BB rapidly induces expression of 20.5 and 21 kDa, high molecular weight (HMW) FGF-2 that accumulates in the nucleus and nucleolus. Conversely, PDGF treatment has little or no effect on 18 kDa, low-molecular weight FGF-2 expression. PDGF-BB-induced upregulation of HMW FGF-2 expression is controlled by sustained activation of extracellular signal-regulated kinase (ERK)-1/2 and is abolished by actinomycin D. These data describe a novel interaction between PDGF-BB and FGF-2, and indicate that the nuclear forms of FGF-2 may mediate the effect of PDGF activity on vascular smooth muscle cells.

Animals↗
PubMed2005

FGF and FGFR signaling in chondrodysplasias and craniosynostosis.

The first experimental mouse model for FGF2 in bone dysplasia was made serendipitously by overexpression of FGF from a constitutive promoter. The results were not widely accepted, rightfully drew skepticism, and were difficult to publish; because of over 2,000 studies published on FGF-2 at the time (1993), only a few reported a role of FGF-2 in bone growth and differentiation. However, mapping of human dwarfisms to mutations of the FGFRs shortly, thereafter, made the case that bone growth and remodeling was a major physiological function for FGF. Subsequent production of numerous transgenic and targeted null mice for several genes in the bone growth and remodeling pathways have marvelously elucidated the role of FGFs and their interactions with other genes. Indeed, studies of the FGF pathway present one of the best success stories for use of experimental genetics in functionally parsing morphogenetic regulatory pathways. What remains largely unresolved is the pleiotropic nature of FGF-2. How does it accelerate growth in one cell then stimulate apoptosis or retard growth for another cell in the same type of tissue? Some of the answers may come through distinguishing the FGF-2 protein isoforms, made from alternative translation start sites, these appear to have substantially different functions. Although we have made substantial progress, there is still much to be learned regarding FGF-2 as a most complex, enigmatic protein. Studies of genetic models in mice and human FGFR mutations have provided strong evidence that FGFRs are important modulators of osteoblast function during membranous bone formation. However, there is some controversy regarding the effects of FGFR signaling in human and murine genetic models. Although significant progress has been made in our understanding of FGFR signaling, several questions remain concerning the signaling pathways involved in osteoblast regulation by activated FGFR. Additionally, little is known about the specific role of FGFR target genes involved in cranial bone formation. These issues need to be addressed in future in in vitro and in vivo approaches to better understand the molecular mechanisms of action of FGFR signaling in osteoblasts that result in anabolic effects in bone formation.

Animals↗
PubMed2006

Differential activity of the FGF-4 enhancer in F9 and P19 embryonal carcinoma cells.

Transcription factors Oct-3/4 and Sox2 behave as global regulators during mammalian embryogenesis. They work together by binding co-operatively to closely spaced HMG and POU motifs (HMG/POU cassettes). Recently, it was suggested that a critical Sox2:Oct-3/4 target gene, FGF-4, is expressed at lower levels in P19 than in F9 embryonal carcinoma (EC) cells, due to lower levels of Sox2 in P19 than in F9 cells. We tested this possibility to better understand how FGF-4 expression is modulated during development. Although we found that P19 EC cells express approximately 10-fold less FGF-4 mRNA than F9 EC cells, we determined that Sox2 levels do not differ markedly in F9 and P19 EC cells. We also determined that Sox2 and Oct-3/4 work together equally well in both EC cell lines. Moreover, in contrast to an earlier prediction based on in vitro binding studies, we demonstrate that the function of the HMG/POU cassettes of the FGF-4 and UTF1 genes does not differ significantly in these EC cell lines when tested in the context of a natural enhancer. Importantly, we determined that the FGF-4 promoter is highly responsive to a heterologous enhancer in both EC cell lines; whereas, the FGF-4 enhancer is 7- to 10-fold less active in P19 than in F9 EC cells. Because F9 and P19 EC cells are likely to represent cells at different stages of mammalian development, we suggest that this difference in FGF-4 enhancer activity may reflect a mechanism used to decrease, but not abolish, FGF-4 expression as the early embryo develops.

Animals↗
PubMed1994

Transcriptional regulation of the murine k-fgf gene.

Embryonal carcinoma (EC) cells provide a useful model system for studying the roles of growth factors during early mammalian development. In 1988, we determined that EC cells express a member of the fibroblast growth factor (FGF) family that cannot be detected after EC cells undergo differentiation. Attempts to understand how differentiation regulates the production of FGFs led to the finding that EC cells express the fibroblast growth factor k-FGF (FGF-4), whereas there is a large decrease in the steady state levels of k-FGF mRNA when EC cells differentiate. This suggested that transcription of the k-fgf gene is repressed when EC cells differentiate. To investigate this possibility, we prepared a series of reporter gene constructs containing various regions of the murine k-fgf gene. These constructs were transfected into two mouse EC cell lines and one mouse embryonic stem (ES) cell line. We determined that the mouse 5' flanking region cannot support expression of the reporter gene. In both EC and ES cell lines, expression of the reporter gene is elevated greatly by the addition of a 316 bp region from the third exon of the murine k-fgf gene. Sequence analysis of the 316 bp region identified one and possibly two conserved octamer binding motifs. These sequences are likely to be involved in regulation of the k-fgf gene, because differentiation of EC cells is known to reduce the expression of octamer binding proteins, including Oct-3. To test the possible role of octamer binding proteins, we examined the expression of our reporter gene constructs in F9-differentiated cells and in PYS-2 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Functional effects of FGF-13 on human lung fibroblasts, dermal microvascular endothelial cells, and aortic smooth muscle cells.

We studied the effects of FGF-13 and FGF-2 on human lung fibroblasts, dermal microvascular endothelial cells, and aortic smooth muscle cells. FGF-13 induced cell growth of lung fibroblasts and aortic smooth muscle cells but had no effect on dermal vascular endothelial cells. FGF-2 induced cell growth in all the three cell types. FGF-13 and FGF-2 had little effect on IL-6 production by lung fibroblasts and aortic smooth muscle cells and substantially enhanced that induced by IL-1alpha. In contrast, FGF-13 and FGF-2 had little effect on IL-6 production by dermal vascular endothelial cells, either alone or in synergy with IL-1alpha.

Aorta↗
PubMed1998

Intracellular association of FGF-2 with the ribosomal protein L6/TAXREB107.

By using the yeast two-hybrid system, we identified the ribosomal protein L6/TAXREB107 as an intracellular partner for FGF-2. L6/TAXREB107 also mediates the DNA binding of the HTLV-1 transactivator Tax. In vitro binding experiments indicated that both the high-molecular-weight forms (HMW) and the 18-kDa form of FGF-2 bind to L6/TAXREB107. Deletion analysis suggested that L6/TAXREB107 has two binding sites for HMW FGF-2 and one binding site for 18-kDa FGF-2, implying that the unique N-terminal extension of the HMW FGF-2 is one of the binding domains for L6/TAXREB107. Transfection assays showed that high expression of either HMW or 18 kDa FGF-2 stimulates Tax-mediated transactivation in NIH 3T3 cells. This result suggests a possible role of FGF-2 in Tax-mediated HTLV-1 transformation as well as FGF-2 binding to ribosomes and/or their precursors.

Animals↗
PubMed2001

FGF-23 inhibits renal tubular phosphate transport and is a PHEX substrate.

Oncogenic osteomalacia (OOM), X-linked hypophosphatemia (XLH), and autosomal dominant hypophosphatemic rickets (ADHR) are phenotypically similar disorders characterized by hypophosphatemia, decreased renal phosphate reabsorption, normal or low serum calcitriol concentrations, normal serum concentrations of calcium and parathyroid hormone, and defective skeletal mineralization. XLH results from mutations in the PHEX gene, encoding a membrane-bound endopeptidase, whereas ADHR is associated with mutations of the gene encoding FGF-23. Recent evidence that FGF-23 is expressed in mesenchymal tumors associated with OOM suggests that FGF-23 is responsible for the phosphaturic activity previously termed "phosphatonin." Here we show that both wild-type FGF-23 and the ADHR mutant, FGF-23(R179Q), inhibit phosphate uptake in renal epithelial cells. We further show that the endopeptidase, PHEX, degrades native FGF-23 but not the mutant form. Our results suggest that FGF-23 is involved in the pathogenesis of these three hypophosphatemic disorders and directly link PHEX and FGF-23 within the same biochemical pathway.

Amino Acid Substitution↗