FGF1 Mediates Overnutrition-Induced Compensatory β-Cell Differentiation

Increased insulin demand resulting from insulin resistance and/or overnutrition induces a compensatory increase in β-cell mass. The physiological factors responsible for the compensation have not been fully characterized. In zebrafish, overnutrition rapidly induces compensatory β-cell differentiation through triggering the release of a paracrine signal from persistently activated β-cells. We identified Fgf1 signaling as a key component of the overnutrition-induced β-cell differentiation signal in a small molecule screen. Fgf1 was confirmed as the overnutrition-induced β-cell differentiation signal, as inactivation of fgf1 abolished the compensatory β-cell differentiation. Furthermore, expression of human FGF1 solely in β-cells in fgf1(-/-) animals rescued the compensatory response, indicating that β-cells can be the source of FGF1. Additionally, constitutive secretion of FGF1 with an exogenous signal peptide increased β-cell number in the absence of overnutrition. These results demonstrate that fgf1 is necessary and FGF1 expression in β-cells is sufficient for the compensatory β-cell differentiation. We further show that FGF1 is secreted during prolonged activation of cultured mammalian β-cells and that endoplasmic reticulum stress acts upstream of FGF1 release. Thus, the recently discovered antidiabetes function of FGF1 may act partially through increasing β-cell differentiation.

Connexin and pannexin hemichannels in inflammatory responses of glia and neurons

Mammals express ∼20 different connexins, the main gap junction forming proteins in mammals, and 3 pannexins, homologs of innexins, the main gap junction forming proteins in invertebrates. In both classes of gap junction, each channel is formed by two hemichannels, one contributed by each of the coupled cells. There is now general, if not universal, agreement that hemichannels of both classes can open in response to various physiological and pathological stimuli when they are not apposed to another hemichannels and face the external milieu. Connexin (and likely pannexin) hemichannel permeability is consistent with that of the cell-cell channels and open hemichannels can be a release site for relatively large molecules such as ATP and glutamate, which can serve as transmitters between cells. Here we describe three experimental paradigms in which connexin and pannexin hemichannel signaling occurs. (1) In cultures of spinal astrocytes FGF-1 causes the release of ATP, and ATP causes opening of pannexin hemichannels, which then release further ATP. Subsequently, several hours later, connexin hemichannels are also opened by an unknown mechanism. Release of ATP appears to become self sustaining through action of P2X7 receptors to open pannexin hemichannels and then connexin hemichannels, both of which are ATP permeable. (2) Spinal cord injury by dropping a small weight on the exposed cord is followed by release of ATP in the region surrounding the primary lesion. This release is greatly reduced in a mouse in which Cx43 is knocked down in the astrocytes. Application of FGF-1 causes a similar release of ATP in the uninjured spinal cord, and an inhibitor of the FGF-1 receptor, PD173074, inhibits both FGF-1 and injury-induced release. Reduction in ATP release is associated with reduced inflammation and less secondary expansion of the lesion. (3) Cortical astrocytes in culture are permeabilized by hypoxia, and this effect is increased by high or zero glucose. The mechanism of permeabilization is opening of Cx43 hemichannels, which can lead to cell death. Activated microglia secrete TNF-α and IL-1β, which open connexin hemichannels in astrocytes. Astrocytes release ATP and glutamate which can kill neurons in co-culture through activation of neuronal pannexin hemichannels. These studies implicate two kinds of gap junction hemichannel in inflammatory responses and cell death. This article is part of a Special Issue entitled Electrical Synapses.

Transgenic expression of nonclassically secreted FGF suppresses kidney repair

FGF1 is a signal peptide-less nonclassically released growth factor that is involved in angiogenesis, tissue repair, inflammation, and carcinogenesis. The effects of nonclassical FGF export in vivo are not sufficiently studied. We produced transgenic mice expressing FGF1 in endothelial cells (EC), which allowed the detection of FGF1 export to the vasculature, and studied the efficiency of postischemic kidney repair in these animals. Although FGF1 transgenic mice had a normal phenotype with unperturbed kidney structure, they showed a severely inhibited kidney repair after unilateral ischemia/reperfusion. This was manifested by a strong decrease of postischemic kidney size and weight, whereas the undamaged contralateral kidney exhibited an enhanced compensatory size increase. In addition, the postischemic kidneys of transgenic mice were characterized by hyperplasia of interstitial cells, paucity of epithelial tubular structures, increase of the areas occupied by connective tissue, and neutrophil and macrophage infiltration. The continuous treatment of transgenic mice with the cell membrane stabilizer, taurine, inhibited nonclassical FGF1 export and significantly rescued postischemic kidney repair. It was also found that similar to EC, the transgenic expression of FGF1 in monocytes and macrophages suppresses kidney repair. We suggest that nonclassical export may be used as a target for the treatment of pathologies involving signal peptide-less FGFs.

Acidic and basic fibroblast growth factors involved in cardiac angiogenesis following infarction

Acidic and basic fibroblast growth factors (FGF-1/FGF-2) promote angiogenesis in cancer. Angiogenesis is integral to cardiac repair following myocardial infarction (MI). The potential regulation of FGF-1/FGF-2 in cardiac angiogenesis postMI remains unexplored. Herein, we examined the temporal and spatial expression of FGF-1/FGF-2 and FGF receptors (FGFR) in the infarcted rat heart at days 1, 3, 7, and 14 postMI. FGF-1/-2 gene and protein expression, cells expressing FGF-1/-2 and FGFR expression were examined by quantitative in situ hybridization, RT-PCR; western blot, immunohistochemistry and quantitative in vitro autoradiography. Compared to the normal heart, we found that in the border zone and infarcted myocardium 1) FGF-1 gene expression was increased in the first week postMI and returned to control levels at week 2; FGF-1 protein levels were, however, largely reduced at day 1, then elevated at day 3 peaked at day 7 and declined at day 14; and cells expressing FGF-1 were primarily inflammatory cells; 2) FGF-2 gene expression was significantly elevated from day 1 to day 14; the increase in FGF-2 protein level was most evident at day 7 and cells expressing FGF-2 were primarily endothelial cells; 3) FGFR expression started to increase at day 3 and remained elevated thereafter; and 4) FGF-1/FGF-2 and FGFR expression remained unchanged in the noninfarcted myocardium. Thus, FGF-1/FGF-2 and FGFR expression are enhanced in the infarcted myocardium in the early stage after MI, which is spatially and temporally coincident with angiogenesis, suggesting that FGF-1/FGF-2 are involved in regulating cardiac angiogenesis and repair.

A novel fibroblast growth factor-1 (FGF1) mutant that acts as an FGF antagonist

BACKGROUND

Crosstalk between integrins and FGF receptors has been implicated in FGF signaling, but the specifics of the crosstalk are unclear. We recently discovered that 1) FGF1 directly binds to integrin alphavbeta3, 2) the integrin-binding site and FGF receptor (FGFR) binding site are distinct, and 3) the integrin-binding-defective FGF1 mutant (R50E) is defective in inducing FGF signaling although R50E still binds to FGFR and heparin and induces transient ERK1/2 activation.

PRINCIPAL FINDINGS

We tested if excess R50E affect DNA synthesis and cell survival induced by WT FGF1 in BaF3 mouse pro-B cells expressing human FGFR1. R50E suppressed DNA synthesis and cell proliferation induced by WT FGF1. We tested if WT FGF1 and R50E generate integrin-FGF1-FGFR ternary complex. WT FGF1 induced ternary complex formation (integrin-FGF-FGFR1) and recruitment of SHP-2 to the complex in NIH 3T3 cells and human umbilical endothelial cells, but R50E was defective in these functions. It has been reported that sustained ERK1/2 activation is integrin-dependent and crucial to cell cycle entry upon FGF stimulation. We thus determined the time-course of ERK1/2 activation induced by WT FGF1 and R50E. We found that WT FGF1 induced sustained activation of ERK1/2, but R50E was defective in this function.

CONCLUSIONS/SIGNIFICANCE

Our results suggest that 1) R50E is a dominant-negative mutant, 2) Ternary complex formation is involved in FGF signaling, 3) The defect of R50E to bind to integrin may be directly related to the antagonistic action of R50E. Taken together, these results suggest that R50E has potential as a therapeutic in cancer.

Protein engineering of a fibroblast growth factor-1 fusion protein with cell adhesive activity

Fibroblast growth factor-1 (FGF1) is one of the most potent angiogenic growth factors, and also plays an important role in regulating cellular functions including cell proliferation, motility, differentiation, survival, and tissue regeneration processes. Here we described a novel fusion protein that was designed by combining the cell adhesion sequence from fibronectin with FGF1. The F1-Fn fusion protein functions as a minimized protein that directs integrin-dependent cell adhesion and stimulates cellular responses including cell proliferation and differentiation. Moreover, our results indicate that Fn-mediated signaling synergizes with signals from FGF1 in promoting cellular adhesion, proliferation, and differentiation in MG63 cells.

Involvement of acidic fibroblast growth factor in spinal cord injury repair processes revealed by a proteomics approach

Acidic fibroblast growth factor (aFGF; also known as FGF-1) is a potent neurotrophic factor that affects neuronal survival in the injured spinal cord. However, the pathological changes that occur with spinal cord injury (SCI) and the attribution to aFGF of a neuroprotective effect during SCI are still elusive. In this study, we demonstrated that rat SCI, when treated with aFGF, showed significant functional recovery as indicated by the Basso, Beattie, and Bresnahan locomotor rating scale and the combined behavior score (p < 0.01-0.001). Furthermore proteomics and bioinformatics approaches were adapted to investigate changes in the global protein profile of the damaged spinal cord tissue when experimental rats were treated either with or without aFGF at 24 h after injury. We found that 51 protein spots, resolvable by two-dimensional PAGE, had significant differential expression. Using hierarchical clustering analysis, these proteins were categorized into five major expression patterns. Noticeably proteins involved in the process of secondary injury, such as astrocyte activation (glial fibrillary acidic protein), inflammation (S100B), and scar formation (keratan sulfate proteoglycan lumican), which lead to the blocking of injured spinal cord regeneration, were down-regulated in the contusive spinal cord after treatment with aFGF. We propose that aFGF might initiate a series of biological processes to prevent or attenuate secondary injury and that this, in turn, leads to an improvement in functional recovery. Moreover the quantitative expression level of these proteins was verified by quantitative real time PCR. Furthermore we identified various potential neuroprotective protein factors that are induced by aFGF and may be involved in the spinal cord repair processes of SCI rats. Thus, our results could have a remarkable impact on clinical developments in the area of spinal cord injury therapy.

Microarray analyses of transdifferentiated mesenchymal stem cells

The molecular events associated with the age-related gain of fatty tissue in human bone marrow are still largely unknown. Besides enhanced adipogenic differentiation of mesenchymal stem cells (MSCs), transdifferentiation of osteoblast progenitors may contribute to bone-related diseases like osteopenia. Transdifferentiation of MSC-derived osteoblast progenitors into adipocytes and vice versa has previously been proven feasible in our cell culture system. Here, we focus on mRNA species that are regulated during transdifferentiation and represent possible control factors for the initiation of transdifferentiation. Microarray analyses comparing transdifferentiated cells with normally differentiated cells exhibited large numbers of reproducibly regulated genes for both, adipogenic and osteogenic transdifferentiation. To evaluate the relevance of individual genes, we designed a scoring scheme to rank genes according to reproducibility, regulation level, and reciprocity between the different transdifferentiation directions. Thereby, members of several signaling pathways like FGF, IGF, and Wnt signaling showed explicitly differential expression patterns. Additional bioinformatic analysis of microarray analyses allowed us to identify potential key factors associated with transdifferentiation of adipocytes and osteoblasts, respectively. Fibroblast growth factor 1 (FGF1) was scored as one of several lead candidate gene products to modulate the transdifferentiation process and is shown here to exert inhibitory effects on adipogenic commitment and differentiation.

Could chronic wounds not heal due to too low local copper levels?

Copper is an essential trace element involved in numerous human physiological and metabolic processes. It plays a key role in many of the processes that together comprise wound healing, including induction of endothelial growth factor, angiogenesis and expression and stabilization of extracellular skin proteins. We hypothesize that in individuals with diabetic ulcers, decubitus, peripheral vascular, or other wounds which might have compromised circulation to the wound site, that part of the incapacity of the wounds to heal is due to low local copper levels. Contamination of wounds is also an important factor causing impaired wound healing. Importantly, copper has potent broad biocidal properties. In contrast, the risk of adverse skin reactions due to exposure to copper is extremely low. We thus hypothesize that introducing copper into wound dressings would not only reduce the risk of wound and dressing contamination, as silver does but, more importantly, would stimulate faster wound repair directly. This would be done by the release of copper from the wound dressings directly into the wound site inducing angiogenesis and skin regeneration.

Mechanism for FGF-1 to regulate biogenesis of apoE-HDL in astrocytes

Fibroblast growth factor-1 (FGF-1) is secreted by astrocytes and stimulates apolipoprotein E (apoE)-HDL biogenesis by an autocrine mechanism to help in recovery from brain injury. In apoE-deficient mouse astrocytes, FGF-1 stimulated cholesterol biosynthesis without enhancing its release, indicating a signaling pathway independent of apoE biosynthesis upregulation. SU5402, an inhibitor of FGF receptor, inhibited FGF-1-induced phosphorylation of MEK, ERK, and Akt, as well as all the apoE-HDL biogenesis-related events in rat astrocytes. LY294002, an inhibitor of phosphatidylinositide 3-OH kinase (PI3K) and of Akt phosphorylation, inhibited apoE-HDL secretion but not cholesterol biosynthesis, whereas U0126, an inhibitor of MEK and of ERK phosphorylation, inhibited cholesterol biosynthesis but not apoE-HDL secretion. Increase of apoE-mRNA by FGF-1 was not influenced by either inhibitor. When rat apoE/pcDNA3.his was transfected to transformed rat astrocyte GA-1 cells that otherwise do not synthesize apoE (GA-1/25), FGF-1 did not influence apoE-mRNA, but did increase the apoE secretion and Akt phosphorylation that were suppressed by LY294002. Lipid biosynthesis was increased by FGF-1 in GA-1/25 cells and suppressed by U0126. FGF-1 upregulates apoE-HDL biogenesis by three independent signaling pathways. The PI3K/Akt pathway upregulates secretion of apoE/apoE-HDL, the MEK/ERK pathway stimulates cholesterol biosynthesis, and an unknown pathway enhances apoE transcription.

Forced expression of hepatocyte-specific fibroblast growth factor 21 delays initiation of chemically induced hepatocarcinogenesis

Inappropriate fibroblast growth factor (FGF) signaling is involved in most tissue-specific pathologies including cancer. Previously we showed that inappropriate expression and chronic activity of FGF receptor (FGFR) 1 in hepatocytes accelerated diethylnitrosamine (DEN)-initiated hepatocarcinogenesis. Here we showed that although widely expressed FGF1 and FGF2 are frequently upregulated in hepatocellular carcinoma (HCC), germline deletion of both FGF1 and FGF2 had no effect on DEN-initiated hepatocarcinogenesis. Thus overexpression of FGF1 or FGF2 may be a consequence rather than contributor to hepatoma progression. FGF21 is the first of 22 homologues whose expression has been reported to be preferentially in the liver. We showed that similar to FGF1 and FGF2, FGF21 mRNA was upregulated in neoplastic and regenerating liver after partial hepatectomy (PH) and CCl4 administration. In situ hybridization analysis confirmed that in contrast to FGF1 and FGF2, expression of FGF21 mRNA was limited to hepatocytes. Forced overexpression of FGF21 in hepatocytes by gene targeting had no apparent impact on normal liver development and compensatory response to injury. Surprisingly, overexpression of FGF21 delayed the appearance of DEN-induced liver tumors. At 8 and 10 mo, only 10% and 30% of transgenic mice, respectively, developed adenomas compared to 50% (all adenomas) and 80% (60% adenoma/20% HCC) in the wild-type (WT) mice. However, the incidence and burden of HCC at 10 mo and later was equal in the FGF21 transgenic and WT mice. We propose that FGF21 may delay development of adenomas through activation of resident hepatocyte FGFR4 at early times, but counteracts the delay by acceleration of progression to HCC through interaction with ectopic FGFR1 once it appears in hepatoma cells. This indicates a dual function of FGF21 that may reflect changes in FGFR isotype during progression of differentiated hepatoma cells.

fgf1 is required for normal differentiation of erythrocytes in zebrafish primitive hematopoiesis

Hematopoiesis in vertebrate development involves an embryonic, primitive wave and a later, definitive wave in which embryonic blood cells are replaced with adult blood cells. We here show that zebrafish fgf1 is involved in vivo in primitive hematopoiesis. Fibroblast growth factor-1 (FGF1) morpholino knockdown leads to abnormal accumulation of blood cells in the posterior intermediate cell mass at 32 hr postfertilization. Expression of the erythroid markers gata1 and ika, normally diminishing in differentiating erythrocytes at this stage, is maintained at abnormally high levels in primitive blood cells. The onset of erythrocyte differentiation as assessed by o-dianisidine staining is severely delayed. Most fgf1 morphants later recover to wild-type appearance, and primitive erythrocytes eventually differentiate. Zebrafish fgf1 is syntenic to human FGF1, which maps to a critically deleted region in human del(5q) syndrome posing an increased risk of leukemia to patients. As its knockdown in zebrafish changes expression of gata1, a gene involved in hematopoietic stem cell decisions, FGF1 should be considered to play a role in the pathogenesis of del(5q) syndrome.

Three faces of mortalin: a housekeeper, guardian and killer

Mortalin was first cloned as a mortality factor that existed in the cytoplasmic fractions of normal, but not in immortal, mouse fibroblasts. A decade of efforts have expanded its persona from a house keeper protein involved in mitochondrial import, energy generation and chaperoning of misfolded proteins, to a guardian of stress that has multiple binding partners and to a killer protein that contributes to carcinogenesis on one hand and to old age disorders on the other. Being proved to be an attractive target for cancer therapy, it also warrants attention from the perspectives of management of old age diseases and healthy aging.

Role of FGF1, FGF2 and FGF7 in the development of the pancreas from control and streptozotocin-treated hamsters

Although progress has been made with respect to the growth and transcription factors implicated in pancreatic development, many questions remain unsolved. It has been established that during embryonic life, both endocrine and acinar cells are derived from pancreatic epithelial precursor cells. Growth factors control the proliferation of precursor cells and their ability to differentiate into mature cells, both in pre-natal and in early post-natal life. Pancreatic development during the early post-natal period is an area of great interest for many scientists. In this study we have examined the structure characteristics, functional and proliferative activity of control and diabetic hamster pancreatic ductal, exocrine and beta cells, following treatment with FGFs 1, 2 and 7 in vitro. Light and electron microscopic studies indicated active synthetic processes in these cells under the influence of the investigated FGFs. In our experimental model of diabetes, the labelling index of the cells was significantly higher than in corresponding control groups of hamsters. We established that FGF2 at a concentration of 10 ng/l was responsible for the most prominent effect on ductal cells and beta cells in the diabetic groups. FGF1 at a concentration of 10 ng/l displayed the highest stimulatory effect on exocrine cells in the diabetic groups at post-natal day 10. Taken together these data strongly suggest that FGF1 and FGF2 induce proliferation of pancreatic epithelial cells during the early post-natal period whereas FGF7 is not strictly specific for pancreatic cell proliferation.

Sustained low levels of fibroblast growth factor-1 promote persistent microvascular network formation

BACKGROUND

Therapeutic neovascularization using high growth factor concentrations may lead to transient vessel formation and abnormal microvascular structure. The goal of this study was to quantify temporal and concentration effects of fibroblast growth factor-1 (FGF-1) on the persistence and morphology of microvascular networks.

METHODS

Endothelial cells were incubated in suspension culture forming aggregates that were embedded in fibrin glue (FG) and stimulated with varying concentrations of FGF-1 with of heparin. Capillary networks formed were quantified for 21 days.

RESULTS

High FGF-1 concentrations resulted in rapid and intense sprout formation, with excessive branching. At later times, these vessels regressed, with cellular debris in former vessel locations. At later times, the 1-ng/mL group surpassed the high concentration groups with continuous sprout growth and complete FG vascularization by 23 days.

CONCLUSION

Sustained low levels of FGF-1 maintained a persistent microvascular network response, whereas higher levels resulted in abnormal phenotype followed by vessel regression.

Muscle cell survival mediated by the transcriptional coactivators p300 and PCAF displays different requirements for acetyltransferase activity

Normal skeletal muscle development requires the proper orchestration of genetic programs by myogenic regulatory factors (MRFs). The actions of the MRF protein MyoD are enhanced by the transcriptional coactivators p300 and the p300/CBP-associated factor (PCAF). We previously described C2 skeletal myoblasts lacking expression of insulin-like growth factor-II (IGF-II) that underwent progressive apoptotic death when incubated in differentiation-promoting medium. Viability of these cells was sustained by addition of IGF analogs or unrelated peptide growth factors. We now show that p300 or PCAF maintains myoblast viability as effectively as added growth factors through mechanisms requiring the acetyltransferase activity of PCAF but not of p300. The actions of p300 to promote cell survival were not secondary to increased expression of known MyoD targets, as evidenced by results of gene microarray experiments, but rather appeared to be mediated by induction of other genes, including fibroblast growth factor-1 (FGF-1). Conditioned culture medium from cells expressing p300 increased myoblast viability, and this was blocked by pharmacological inhibition of FGF receptors. Our results define a role for p300 in promoting cell survival, which is independent of its acetyltransferase activity and acts at least in part through FGF-1.

FGF-1 as a possible carrier for targeted drug delivery

Delivery of anticancer chemotherapeuticals to tumor cells raises many problems due to pronounced systemic side effects. Targeted delivery using specific monoclonal antibodies has been postulated; however, monoclonal antibodies very often produce immune response in the human body. Chimeric and humanized antibodies have some advantages over monoclonals, but still some side effects can be observed. Because some tumor cells (e.g., breast cancer cells) overexpress fibroblast growth factor receptors, it is possible to use these receptors for drug targeting. We think that growth factors of human origin can be used for drug delivery to tumor cells. Fibroblast growth factor-1 (FGF-1) is especially suitable as drug carrier because it can cross the barrier of the cell membrane and reach the cytosol and, further, it is translocated to the cell nucleus. One possible approach for anticancer therapy is to use biotinylated growth factors linked to avidin/ streptavidin-coated liposomes. Another possibility is to link drug molecules or radioisotopes directly to growth factors. Thus, we wanted to determine if FGF-1 retains its biological activity after chemical modification, and if it is able to bind its receptors and if it can be internalized by the cells. For this purpose we have biotinylated recombinant human FGF-1 and we have verified that it retains its biological activities in NIH/3T3 and MDA-MB-453 cells and it is able to enter the target cells.

Expression of the SNT-1/FRS2 phosphotyrosine binding domain inhibits activation of MAP kinase and PI3-kinase pathways and antiestrogen resistant growth induced by FGF-1 in human breast carcinoma cells

Fibroblast growth factor (FGF) signaling can bypass the requirement for estrogen receptor (ER) activation in the growth of ER-positive (ER+) breast cancer cells. Fibroblast growth factor-1 stimulation leads to phosphorylation of the adaptor protein Suc1-associated neurotrophic factor-induced tyrosine-phosphorylated target (SNT-1) on C-terminal tyrosine residues, whereas it is constitutively bound through its N-terminal phosphotyrosine-binding domain (PTB) to FGF receptors (FGFRs). By expressing the PTB domain of SNT-1 (SNT-1 PTB) in an inducible manner in an ER+ breast carcinoma line, ML20, we asked whether we could uncouple FGFR activation from its downstream signaling components and abrogate FGF-1-induced antiestrogen-resistant growth. Induction of SNT-1 PTB resulted in a significant decrease of FGF-1-dependent tyrosine phosphorylation of endogenous SNT-1, strong inhibition of complex formation between SNT-1, Gab-1 and Sos-1, and reduced activation of Ras, mitogen-activated protein kinase (MAP kinase), and Akt. SNT-1 PTB also inhibited the phosphorylation of p70S6K on Thr421/Ser424 and Ser411, which may result from the abrogation of MAP kinase activity. Moreover, we also observed a decreased phosphorylation of the MAP kinase-independent site Thr389. This may reflect both inhibition of PI-3 kinase pathways and mammalian target of rapamycin (mTOR)-dependent signaling, as the phosphorylation of Thr389 site was sensitive to treatment with the PI3-K and mTOR inhibitors, LY294002 and rapamycin, respectively. Collectively these results suggest that SNT-1 plays a pivotal role in FGF-dependent activation of the Ras-MAP kinase, PI-3 kinase, and mTOR pathways in these cells. Fibroblast growth factor-1 dependent colony formation of ML20 cells in media containing the pure antiestrogen ICI 182,780 was also markedly inhibited upon induction of SNT-1 PTB, suggesting that blockade of FGFR-SNT-1 interactions might abrogate FGF-mediated antiestrogen resistance in breast cancers.

FGF-1 and FGF-2 Require the Cytosolic Chaperone Hsp90 for Translocation into the Cytosol and the Cell Nucleus

Similarly to many protein toxins, the growth factors fibroblast growth factor 1 (FGF-1) and FGF-2 translocate from endosomes into the cytosol. It was recently found that certain toxins are dependent on cytosolic Hsp90 for efficient translocation across the endosomal membrane. We therefore investigated the requirement for Hsp90 in FGF translocation. We found that low concentrations of the specific Hsp90 inhibitors, geldanamycin and radicicol, completely blocked the translocation of FGF-1 and FGF-2 to the cytosol and the nucleus. The drugs did not interfere with the initial binding of FGF-1 to the growth factor receptors at the cell-surface or with the subsequent internalization of the growth factors into endosomes. The activation of known signaling cascades downstream of the growth factor receptors was also not affected by the drugs. The data indicate that the drugs block translocation from endosomes to the cytosol implying that Hsp90 is required for translocation of FGF-1 and FGF-2 across the endosomal membrane.

Transforming growth factor-beta stimulates epithelial-mesenchymal transformation in the proepicardium

The proepicardium (PE) migrates over the heart and forms the epicardium. A subset of these PE-derived cells undergoes epithelial-mesenchymal transformation (EMT) and gives rise to cardiac fibroblasts and components of the coronary vasculature. We report that transforming growth factor-beta (TGFbeta) 1 and TGFbeta2 increase EMT in PE explants as measured by invasion into a collagen gel, loss of cytokeratin expression, and redistribution of ZO1. The type I TGFbeta receptors ALK2 and ALK5 are both expressed in the PE. However, only constitutively active (ca) ALK2 stimulates PE-derived epithelial cell activation, the first step in transformation, whereas caALK5 stimulates neither activation nor transformation in PE explants. Overexpression of Smad6, an inhibitor of ALK2 signaling, inhibits epithelial cell activation, whereas BMP7, a known ligand for ALK2, has no effect. These data demonstrate that TGFbeta stimulates transformation in the PE and suggest that ALK2 partially mediates this effect.

Prox1 promotes lineage-specific expression of fibroblast growth factor (FGF) receptor-3 in lymphatic endothelium: a role for FGF signaling in lymphangiogenesis

Fibroblast growth factors play important roles in angiogenesis, but their functions in lymphangiogenesis remain poorly understood. The homeodomain transcription factor Prox1 is essential for development of the lymphatic system by specifying lymphatic endothelial cell (LEC) fate. Here, we identify fibroblast growth factor (FGF) receptor (FGFR)-3 as a novel Prox1 target gene. Ectopic overexpression of Prox1 in blood vascular endothelial cells up-regulates FGFR-3. Prox1 induces the expression of the IIIc isoform, which we also found to be the major isoform of FGFR-3 expressed in LECs. This transcriptional activation is mediated by a direct binding of Prox1 to newly identified Prox1-response elements in the FGFR-3 promoter. Consistently, FGFR-3 is up-regulated in Prox1-positive newly formed lymphatic vessels during embryogenesis and its lymphatic-specific expression is maintained throughout development. We also found that FGF-1 and FGF-2 promote proliferation, migration, and survival of cultured LECs without involvement of vascular endothelial cell growth factor receptor-3. We show that FGF-2 binds to low- and high-affinity receptors on LECs and is efficiently internalized and processed. Moreover, functional inhibition of FGFR-3 using small interfering RNA represses LEC proliferation. Together, these results indicate that FGFR-3 is an initial target of Prox1 during the lymphatic cell fate specification and that FGF signaling may play an important role in lymphatic vessel development.

FGF1 inhibits p53-dependent apoptosis and cell cycle arrest via an intracrine pathway

We analysed the relationships between p53-induced apoptosis and the acidic fibroblast growth factor 1 (FGF1) survival pathway. We found that p53 activation in rat embryonic fibroblasts induced the downregulation of FGF1 expression. These data suggest that the fgf1 gene is a repressed target of p53. Unlike extracellular FGF1, which has no effect on p53-dependent pathways, intracellular FGF1 inhibits both p53-dependent apoptosis and cell growth arrest via an intracrine pathway. FGF1 increases MDM2 expression at both mRNA and protein levels. This increase is associated with an acceleration of p53 degradation, which may partly account for the ability of endogenous FGF1 to counteract p53 pathways. In the presence of FGF1, p53 was unable to transactivate bax, but no modification of p21 gene transactivation was observed. As Bax is an essential component of the p53-dependent apoptosis pathway, this suggests that intracellular FGF1 inhibits p53 pathways not only by decreasing the stability of p53, but also by modifying some of its transactivation properties. In conclusion, we showed that p53 and FGF1 pathways may interact in the cell to determine cell fate. Deregulation of one of these pathways modifies the balance between cell proliferation and cell death and may lead to tumor progression.

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.

Fibroblast growth factor 1: a key regulator of human adipogenesis

Obesity, with its related problems, is recognized as the fastest growing disease epidemic facing the world, yet we still have limited insight into the regulation of adipose tissue mass in humans. We have previously shown that adipose-derived microvascular endothelial cells (MVECs) secrete a factor(s) that increases proliferation of human preadipocytes. We now demonstrate that coculture of human preadipocytes with MVECs significantly increases preadipocyte differentiation, evidenced by dramatically increased triacylglycerol accumulation and glycerol-3-phosphate dehydrogenase activity compared with controls. Subsequent analysis identified fibroblast growth factor (FGF)-1 as an adipogenic factor produced by MVECs. Expression of FGF-1 was demonstrated in MVECs but not in preadipocytes, while preadipocytes were shown to express FGF receptors 1-4. The proliferative effect of MVECs on human preadipocytes was blocked using a neutralizing antibody specific for FGF-1. Pharmacological inhibition of FGF-1 signaling at multiple steps inhibits preadipocyte replication and differentiation, supporting the key adipogenic role of FGF-1. We also show that 3T3-L1 cells, a highly efficient murine model of adipogenesis, express FGF-1 and, unlike human preadipocytes, display no increased differentiation potential in response to exogenous FGF-1. Conversely, FGF-1-treated human preadipocytes proliferate rapidly and differentiate with high efficiency in a manner characteristic of 3T3-L1 cells. We therefore suggest that FGF-1 is a key human adipogenic factor, and these data expand our understanding of human fat tissue growth and have significant potential for development of novel therapeutic strategies in the prevention and management of human obesity.

Angiogenesis-dependent and independent phases of intimal hyperplasia

BACKGROUND

Neointimal vascular smooth muscle cell (VSMC) proliferation is a primary cause of occlusive vascular disease, including atherosclerosis, restenosis after percutaneous interventions, and bypass graft stenosis. Angiogenesis is implicated in the progression of early atheromatous lesions in animal models, but its role in neointimal VSMC proliferation is undefined. Because percutaneous coronary interventions result in induction of periadventitial angiogenesis, we analyzed the role of this process in neointima formation.

METHODS AND RESULTS

Local injury to the arterial wall in 2 different animal models induced periadventitial angiogenesis and neointima formation. Application of angiogenesis stimulators vascular endothelial growth factor (VEGF-A165) or a proline/arginine-rich peptide (PR39) to the adventitia of the injured artery induced a marked increase in neointimal thickening beyond that seen with injury alone in both in vivo models. Inhibition of either VEGF (with soluble VEGF receptor 1 [sFlt1]) or fibroblast growth factor (FGF) (with a dominant=negative form of FGF receptor 1 [FGF-R1DN]), respectively, signaling reduced adventitial thickening induced by VEGF and PR39 to the level seen with mechanical arterial injury alone. However, neither inhibitor was effective in preventing neointimal thickening after mechanical injury when administered in the absence of angiogenic growth factor.

CONCLUSIONS

Our findings indicate that adventitial angiogenesis stimulates intimal thickening but does not initiate it.

Fibroblast growth factor-1 improves cardiac functional recovery and enhances cell survival after ischemia and reperfusion: a fibroblast growth factor receptor, protein kinase C, and tyrosine kinase-dependent mechanism

OBJECTIVES

We sought to investigate the role of fibroblast growth factor (FGF)-1 during acute myocardial ischemia and reperfusion.

BACKGROUND

The FGFs display cardioprotective effects during ischemia and reperfusion.

METHODS

We investigated FGF-1-induced cardioprotection during ischemia and reperfusion and the intracellular signaling pathways responsible for these effects in an ex vivo murine setup of myocardial ischemia and reperfusion.

RESULTS

Cardiac-specific human FGF-1 overexpression was associated with enhanced post-ischemic hemodynamic recovery and decreased lactate dehydrogenase release during reperfusion. Inhibition of the FGF receptor, protein kinase C (PKC), and tyrosine kinase (TK) resulted in blockade of FGF-1-induced protective effects on cardiac functional recovery and cell death.

CONCLUSIONS

The overexpression of FGF-1 induces cardioprotection through a pathway that involves the FGF receptor, PKC, and TK.

The docking protein Gab1 is an essential component of an indirect mechanism for fibroblast growth factor stimulation of the phosphatidylinositol 3-kinase/Akt antiapoptotic pathway

The docking protein Gab1 has been implicated as a mediator of multiple signaling pathways that are activated by a variety of receptor tyrosine kinases and cytokines. We have previously proposed that fibroblast growth factor 1 (FGF1) stimulation of tyrosine phosphorylation of Gab1 and recruitment of phosphatidylinositol (PI) 3-kinase are mediated by an indirect mechanism in which the docking protein fibroblast receptor substrate 2alpha (FRS2alpha) plays a critical role. In this report, we explore the role of Gab1 in FGF1 signaling by using mouse embryo fibroblasts (MEFs) derived from Gab1(-/-) or FRS2alpha(-/-) mice. We demonstrate that Gab1 is essential for FGF1 stimulation of both PI 3-kinase and the antiapoptotic protein kinase Akt, while FGF1-induced mitogen-activated protein kinase (MAPK) stimulation is not affected by Gab1 deficiency. To test the indirect mechanism for FGF1 stimulation of PI 3-kinase and Akt, we use a chimeric docking protein composed of the membrane targeting signal and the phosphotyrosine-binding domain of FRS2alpha fused to the C-terminal portion of Gab1, the region including the binding sites for the complement of signaling proteins that are recruited by Gab1. We demonstrate that expression of the chimeric docking protein in Gab1(-/-) MEFs rescues PI 3-kinase and the Akt responses, while expression of the chimeric docking protein in FRS2alpha(-/-) MEFs rescues stimulation of both Akt and MAPK. These experiments underscore the essential role of Gab1 in FGF1 stimulation of the PI 3-kinase/Akt signaling pathway and provide further support for the indirect mechanism for FGF1 stimulation of PI 3-kinase involving regulated assembly of a multiprotein complex.

Repression of fibroblast growth factor receptor 1 gene expression by E2F4 in skeletal muscle cells

Fibroblast growth factor receptor 1 (FGFR1) gene expression is positively and negatively regulated during muscle differentiation. We recently reported that FGFR1 gene expression was up-regulated by Sp transcription factors in proliferating myoblasts. However, the mechanism of down-regulation of this gene during differentiation is unknown. We have identified the transcription factor E2F4 as a negative regulator of FGFR1 gene expression. Immunodetection studies revealed that endogenous E2F1 and E2F2 proteins were cytoplasmic in myoblasts and myotubes, whereas E2F4 was abundant in the nuclei of both. Upon overexpression, E2F4 repressed FGFR1 promoter activity in a dose-dependent manner in myoblasts and Drosophila SL2 cells, and mutation of the E2F4 binding site increased FGFR1 promoter activity and reduced E2F4-mediated repression. Gel shift assays detected E2F4 binding to a synthetic FGFR1 E2F4 binding site and chromatin immunoprecipitation assays detected E2F4 binding to the endogenous FGFR1 promoter in proliferating myoblasts and myotubes. The results indicate that FGFR1 promoter activity in skeletal muscle cells is repressed by E2F4.

Highly Diverse Heparan Sulfate Analogue Libraries: Providing Access to Expanded Areas of Sequence Space for Bioactivity Screening

Structurally diverse heparan sulfate analogue libraries were produced chemicoenzymatically from heparin. They possess vastly more heterogeneity than tissue heparan sulfates, expand the sequence space available for screening, and can help identify minimal structural features associated with activity. Library components are likely to exhibit fewer nonspecific interactions and side-effects than heparin or simple chemically modified heparin. A strategy for their use is illustrated for the fibroblast growth factor-receptor tyrosine kinase signaling system.

[Expression of aFGF and bFGF in ovarian cancer and their effect on ovarian cancer cell proliferation]

BACKGROUND & OBJECTIVE

There was overexpression of fibroblast growth factor (FGF) in many kinds of malignant tumors. Overexpression of basic fibroblast growth factor (bFGF) has been found in ovary cancer and there is no report about acidic fibroblast growth factor (aFGF) in ovary cancer up to now. The aim of this study was to explore the expression of aFGF and bFGF in ovarian cancer, and the effects of exogenous aFGF and bFGF on the proliferation of ovarian cancer OVCA3 cells, to discuss the relationship between FGF and ovary cancer.

METHODS

The expression levels of aFGF and bFGF were determined by reverse transcription polymerase chain reaction (RT-PCR) in 40 cases of ovarian epithelial cancer. MTT assay was used to determine the influence of aFGF and bFGF on the proliferation of ovarian cancer cell.

RESULTS

The expression levels of aFGF mRNA and bFGF mRNA in the ovarian epithelial cancer were 0.981+/-0.130 and 1.023+/-0.131, respectively. Compared with normal ovary, ovarian tumor like lesion and benign ovary tumors, the difference was significant (P< 0.05). The expression levels in stage III-IV were significantly higher than those in stageI-II. Addition of exogenous aFGF and bFGF to OVCA3 cell line resulted in significant and reproducible increases in cell number in a dose-dependent manner. When the concentration of aFGF was at 1.2 microg/ml, the proliferative ratio of OVCA3 cell line was 1.51 times of the control group. When the concentration of bFGF was at 100 ng/ml, the proliferative ratio of OVCA3 cell line was 1.85 times of the control group.

CONCLUSION

aFGF and bFGF may play important roles in carcinogenesis, development, and invasion of ovarian epithelial cancer, and they can be used as the important indices for biologic behavior of ovarian cancer.

[Expression of aFGF in ovarian epithelial cancer and its signal transduction pathway]

OBJECTIVE

To explore the expression of acidic fibroblast growth factor (aFGF) and its receptor FGFR1 in ovarian epithelial cancer and observe the effects of aFGF and TPK inhibitor Genistein on intracellular PKC and ERK activity in ovarian epithelial cancer cells line CAOV3.

METHODS

The expression levels of aFGF and FGFR1 were evaluated by RT-PCR and western blot in 40 cases of ovarian epithelial cancer. The activity of PKC and ERK in cells induced by different concentration of aFGF and Genistein were detected by incorporation of [gamma-(32)P]-ATP into exogenous substrate.

RESULTS

The expression levels of aFGFmRNA and FGFR1mRNA in the ovarian epithelial cancer were 0.981 +/- 0.130 and 1.047 +/- 0.148, respectively. Compared with normal ovary, ovarian tumor like condition and benign ovary tumors, the difference was significant (P < 0.05). The expression levels in stage III - IV were significantly higher than those in stage I - II (P < 0.05). There were overexpression of aFGF and FGFR1 in the ovarian epithelial cancer in western blot, too. The intracellular PKC and ERK activity increased with aFGF in a dose dependent manner, Genistein suppressed the intracellular PKC and ERK activity also in a dose dependent manner.

CONCLUSION

aFGF may play an important role in carcinogenesis, development and invasion of ovarian epithelial cancer. Its receptor in human ovarian cancer cell line CAOV3 possessed TPK activity. These tyrosine-specific protein phosphorylation may initiate a cascade of biochemical events, which may increase the intracellular PKC and ERK activity. PKC and ERK locate downstream of TPK in CAOV3 cell line.

Adrenocortical cell transplantation in scid mice: the role of the host animals' adrenal glands

Adrenocortical cell transplantation is a powerful technique for the investigation of the regulation of adrenocortical structure and function. Some classical organ and tissue transplantation experiments suggest that the success of transplantation depends on the activity of the pituitary gland and other endocrine systems, and is therefore influenced by the host animals' own adrenal glands. For this reason, our experiments have usually been performed on adrenalectomized animals. However, we show here that cell transplantation experiments, involving the introduction of bovine adrenocortical cells into scid mice, do produce transplant tissues in the presence of the host animals' adrenal glands. However, the tissue that forms is small and its cells also smaller than usual. When the adrenals of such animals are removed in a second surgical procedure, the transplants show a rapid increase in steroidogenic function and a slower increase in size, over several weeks. We conclude that the initial process by which transplanted adrenocortical cells organize into a tissue structure is not affected by the presence of the host animals' adrenal glands, but the growth of the transplants is limited until the adrenal glands are removed.

Notch activation suppresses fibroblast growth factor-dependent cellular transformation

Aberrant activations of the Notch and fibroblast growth factor receptor (FGFR) signaling pathways have been correlated with neoplastic growth in humans and other mammals. Here we report that the suppression of Notch signaling in NIH 3T3 cells by the expression of either the extracellular domain of the Notch ligand Jagged1 or dominant-negative forms of Notch1 and Notch2 results in the appearance of an exaggerated fibroblast growth factor (FGF)-dependent transformed phenotype characterized by anchorage-independent growth in soft agar. Anchorage-independent growth exhibited by Notch-repressed NIH 3T3 cells may result from prolonged FGFR stimulation caused by both an increase in the expression of prototypic and oncogenic FGF gene family members and the nonclassical export of FGF1 into the extracellular compartment. Interestingly, FGF exerts a negative effect on Notch by suppressing CSL (CBF-1/RBP-Jk/KBF2 in mammals, Su(H) in Drosophila and Xenopus, and Lag-2 in Caenorhabditis elegans)-dependent transcription, and the ectopic expression of constitutively active forms of Notch1 or Notch2 abrogates FGF1 release and the phenotypic effects of FGFR stimulation. These data suggest that communication between the Notch and FGFR pathways may represent an important reciprocal autoregulatory mechanism for the regulation of normal cell growth.

Human umbilical vein endothelium-derived cells retain potential to differentiate into smooth muscle-like cells

Mouse embryonic stem-derived cells were recently shown to differentiate into endothelial and smooth muscle cells. In the present study, we investigated whether human umbilical vein endothelium-derived cells retain the potential to differentiate into smooth muscle cells. Examination of biochemical markers, including basic calponin, SM22alpha, prostaglandin E synthase, von Willebrand factor, and PECAM-1, as well as cell contractility, showed that whereas endothelium-derived cells cultured with fibroblast growth factor can be characterized as endothelial cells, when deprived of fibroblast growth factor, a significant fraction differentiates into smooth muscle-like cells. Reapplication of fibroblast growth factor reversed this differentiation. Activin A was up-regulated in fibroblast growth factor-deprived, endothelium-derived cells; moreover, the inhibitory effects of exogenous follistatin and overexpressed Smad7 on smooth muscle-like differentiation confirmed that the differentiation was driven by activin A signaling. These findings indicate that when deprived of fibroblast growth factor, human umbilical vein endothelium-derived cells are capable of differentiating into smooth muscle-like cells through activin A-induced, Smad-dependent signaling, and that maintenance of the endothelial cell phenotype and differentiation into smooth muscle-like cells are reciprocally controlled by fibroblast growth factor-1 and activin A.

FGF1 and VEGF Mediated Angiogenesis in KHT Tumor-Bearing Mice

Isotransplants of murine fibrosarcoma (KHT) cells were inoculated i.m. into the hind limbs of 6-8 week-old female C3H/HeJ mice. Intratumoral injection of FGF1 or VEGF proteins decreased hypoxic marker uptake in murine fibrosarcoma KHT. Reduction of tumor hypoxia did not correlate with mRNA expression of transcription factors in tumors. Likewise, there was no significant alteration in either apoptotic frequency or the mRNA levels of 10 apoptotic-related molecules in FGF1- or VEGF-treated tumors. mRNA expression for MCP-1, IL-1 beta, IL-18, and IL-1Ra, however, were decreased in the tumors following FGF1 or VEGF treatment. Among the normal tissues tested (brain, kidney, liver, spleen, and lung), basal mRNA levels for cytokines and chemokines varied. Intratumoral injection of FGF1 or VEGF (6 daily intra-tumor injections of 6 micrograms/mouse) did not alter most cytokine or chemokine mRNA expression in spleen and lung. In summary, alteration of tumor oxygenation by local administration of angiogenic growth factors may be mediated by cytokine/chemokine production in the tumor.

Rapid tumor development and potent vascularization are independent events in carcinoma producing FGF-1 or FGF-2

FGF-1 and FGF-2 are pleiotropic growth factors for many cell types, operating through the activation of specific transmembrane FGF receptors (FGFRs). The role of these factors in tumor progression was investigated, with specific discrimination between their autocrine and non autocrine cellular activity. The rat bladder carcinoma NBT-II cells were engineered to produce FGF-1 or 18 kDa FGF-2 in the presence or absence of their specific receptor. Non-autocrine cells that produced FGF-1 or FGF-2 but lacked FGFRs were epithelial and reminiscent of the parental NBT-II cells. Whilst autocrine cells, which both constitutively produced and secreted the growth factor and expressed FGFRs, had a highly invasive mesenchymal phenotype. Correspondingly, the autocrine cells were highly tumorigenic in vivo compared to the parental and non-autocrine cells, which correlated with the increased production of uPAR and active uPA and increased in vitro invasive potential. Although all cells produced VEGF, only tumors derived from cells that produced FGF-1 or FGF-2 were highly vascularized, suggesting that these two growth factors could be involved in the angiogenic process by activating host endothelial cells. As a result of activation of the FGFR in autocrine cells, changes in cell morphology and an increase in the invasive and tumorigenic properties were observed, however no in vitro or in vivo differential functions between FGF-1 and FGF-2 could be identified in this system. In conclusion, our data demonstrates that rapid tumor development is not dependent upon increased tumor vascularization, suggesting that 'basal' angiogenesis, probably mediated by VEGF, is sufficient to support tumor growth.

Depletion of FGF acts as a lateral inhibitory factor in lung branching morphogenesis in vitro

Previous studies have shown that the interaction of positive and inhibitory signals plays a crucial role during lung branching morphogenesis. We found that in mesenchyme-free conditions, the lung epithelium exerted a lateral inhibitory effect on the neighbouring epithelium via depletion of fibroblast growth factor 1 (FGF1). Contrary to previous suggestions, bone morphogenetic protein 4 could not substitute for the inhibitory effect. Based on of this observation, we used a reaction-diffusion model of the substrate-depletion type to represent the initial phase of in vitro branching morphogenesis of lung epithelium, with depletion of FGF playing the role of lateral inhibitor. The model was able to account for the effects of the FGF1 concentration, extracellular matrix degradation and different subtypes of FGF on morphogenesis of the lung bud epithelia. These results suggest that the depletion of FGF may be a key regulatory component in initial phase of branching morphogenesis of the lung bud epithelium in vitro.

Down-modulation of monocyte transendothelial migration and endothelial adhesion molecule expression by fibroblast growth factor: reversal by the anti-angiogenic agent SU6668

Basic and acidic fibroblast growth factor (bFGF and aFGF, respectively) and vascular endothelial growth factor (VEGF) exert angiogenic actions and have a role in wound healing, inflammation, and tumor growth. Monocytes and endothelial cells are involved in these processes, but the effect of FGF and VEGF on monocyte-endothelial cell interactions has not been defined. We observed that monocyte adhesion to resting or cytokine (tumor necrosis factor-alpha or interleukin-1 alpha)-stimulated human umbilical vein endothelial cells (HUVECs) was markedly inhibited (40 to 65%) by culture (1 to 6 days) of HUVECs with aFGF or bFGF. Monocyte transendothelial migration induced by C5a and chemokines (MCP-1, SDF-1 alpha, RANTES, MIP-1 alpha) was also suppressed (by 50 to 75%) on bFGF-stimulated HUVECs. VEGF did not have these effects at the concentrations used (10 to 20 ng/ml), although like bFGF, it promoted HUVEC proliferation. Culture of HUVECs with bFGF and aFGF significantly down-regulated intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin expression on resting or tumor necrosis factor-alpha-stimulated HUVECs, but had no influence on platelet endothelial cell adhesion molecule (PECAM)-1 and VE-cadherin expression. bFGF also inhibited MCP-1 production by HUVECs. The inhibitory effects of bFGF on monocyte transendothelial migration and adhesion molecule expression were reversed by SU6668, an anti-angiogenic agent and bFGF receptor tyrosine kinase inhibitor. Our results suggest that bFGF and aFGF may suppress endothelial-dependent monocyte recruitment and thus have an anti-inflammatory action during angiogenesis in chronic inflammation but inhibit the immunoinflammatory tumor defense mechanism. However, SU6668 is an effective agent to prevent this down-regulatory action of bFGF on monocyte-endothelial cell interactions.

Docking protein SNT1 is a critical mediator of fibroblast growth factor signaling during Xenopus embryonic development

The docking protein SNT1/FRS2 (fibroblast growth factor receptor substrate 2) is implicated in the transmission of extracellular signals from several growth factor receptors to the mitogen-activated protein (MAP) kinase signaling cascade, but its biological function during development is not well characterized. Here, we show that the Xenopus homolog of mammalian SNT1/FRS-2 (XSNT1) plays a critical role in the appropriate formation of mesoderm-derived tissue during embryogenesis. XSNT1 has an expression pattern that is quite similar to the fibroblast growth factor receptor-1 (FGFR1) during Xenopus development. Ectopic expression of XSNT1 markedly enhanced the embryonic defects induced by an activated FGF receptor, and increased the MAP kinase activity as well as the expression of a mesodermal marker in response to FGF receptor signaling. A loss-of-function study using antisense XSNT1 morpholino oligonucleotides (XSNT-AS) shows severe malformation of trunk and posterior structures. Moreover, XSNT-AS disrupts muscle and notochord formation, and inhibits FGFR-induced MAP kinase activation. In ectodermal explants, XSNT-AS blocks FGFR-mediated induction of mesoderm and the accompanying elongation movements. Our results indicate that XSNT1 is a critical mediator of FGF signaling and is required for early Xenopus development.

Neither fibroblast growth factor-1 nor fibroblast growth factor-2 is an androgen receptor coactivator in androgen-resistant prostate cancer

We used rat prostate cancer cell stable transfectants that lacked either endogenous fibroblast growth factor (FGF)-1 secondary to constitutive expression of FGF-1 antisense RNA (aFa2-transfectants) or endogenous FGF-2 isoforms secondary to constitutive expression of FGF-2 antisense RNA (bFa9-transfectants) to examine the potential synergistic effects of mitogen and androgen as modulators of proliferation. During culture on 5% charcoal-stripped fetal bovine serum (CS-FBS), FGF-1 caused a 2- to 2.5-fold increase in the proliferation of aFa2-transfectants that lacked endogenous FGF-1 and retained full expression of FGF-2 isoforms. In marked constrast, bFa9-transfectants that lacked FGF-2 isoforms and retained full expression of FGF-1 died with exponential kinetics when cultured on either 5% CS-FBS or 5% FBS in the absence of FGF-2. However, FGF-2 promoted bFa9-transfectant survival and exponential proliferation during culture on either 5% CS-FBS or 5% FBS. The nonmetabolizable androgen R1881 did not affect proliferation of either the aFa2- transfectants, the bFa9-transfectants, or the parental prostate cancer cells used to generate these transfectants. Additionally, neither of the androgen receptor antagonists RU23908 or bicalutamide affected either FGF-1-mediated aFa2-transfectant proliferation or FGF-2-mediated bFa9-transfectant proliferation during culture on 5% CS-FBS. Notably, transient transfection analyses established R1881 concentration-dependent induction of chloramphenicol acetyltransferase activity in both aFa2-transfectants and bFa9-transfectants. Thus, the failure of either androgen or antiandrogen to affect either FGF-mediated or FGF-independent antisense-transfectant proliferation is not attributable to absence of functional androgen receptors. The results indicate that FGF effects in these androgen-resistant antisense transfectants do not involve either androgen-dependent or androgen-independent, mitogen-mediated androgen receptor activation. Our studies show that these rat prostate cancer cells are characterized by both retention of functional androgen receptors during development of androgen resistance and mitogen-mediated, autocrine or paracrine (or both) modulated proliferation. These are two prominent properties characteristic of advanced human prostate cancer.

Assessment of the VEGF, bFGF, aFGF and IL8 angiogenic activity in urinary bladder carcinoma, using the mice cutaneous angiogenesis test

Development of new blood vessels in solid tumors depends on changes in equilibrium between angiogenic stimulators and inhibitors. Overexpression of angiogenic growth factors has been shown in bladder carcinoma. The 'mice cutaneous angiogenesis test' is a good method for assessment of the total angiogenic potential of bladder cancer tissue. The analysis of the levels of proangiogenic factors could be useful for the choice of properly directed angiogenesis inhibitors. The aim of our study was to investigate the influence of blocking some angiogenic factors on the angiogenic activity of bladder cancer tissue. Tumor tissue obtained from 12 patients with invasive bladder carcinoma was used. Cancer tissue homogenates were incubated in the presence of specific antibodies against VEGF, bFGF, Il-8 and aFGF. Cytokine levels were determined using the ELISA test. Cutaneous angiogenesis assay in Balb/c mice was performed to detect the angiogenic activity of the tumor tissue. VEGF, bFGF and Il-8 were present in all examined cancer tissues (aFGF level was not estimated). Cytokine concentration and angiogenic activity of bladder cancer tissue showed individual variation. There was no correlation between the cytokines content in tumor tissue and the ability of this tissue to induce angiogenesis. Absorption caused significant reduction in cytokines level. The reduction of angiogenic activity was observed in the cancer tissue of 1 patient after VEGF absorption, in 3 patients' tissue homogenates after incubation with anti-aFGF and in 2 patients' homogenates after bFGF absorption. There was no reduction of angiogenic activity after Il-8 absorption.

Acidic fibroblast growth factor overexpression partially protects 3T3 fibroblasts from apoptosis induced by synthetic retinoid CD437

Retinoids are proapoptotic compounds with therapeutic potential for treating cancer. We evaluated the apoptotic effect of the novel retinoid CD437, and particularly its relationship to Akt and acidic fibroblast growth factor (aFGF). We hypothesized that the novel synthetic retinoid CD437 would exert its apoptotic effect by reducing the activity of Akt. We further hypothesized that aFGF would protect against CD437 apoptosis by preserving the activity of Akt. Initially we demonstrated that CD437 produces apoptotic cell death in NIH 3T3 fibroblasts, and that this effect is attenuated in fibroblasts transfected to express aFGF. Next we assessed Akt activity and showed that phospho-Akt is significantly reduced in 3T3 cells exposed to CD437. We showed that this effect is less pronounced in aFGF transfected 3T3 cells. Furthermore, we observed that the addition of exogenous aFGF to 3T3 cells significantly increases Akt phosphorylation. These findings tend to confirm our hypothesis that reduction in Akt activation is a mechanism involved in the apoptotic effect of the retinoid CD437, and that preservation of Akt phosphorylation occurs in response to aFGF and appears to explain the partially protective effect of aFGF for 3T3 cells vis a vis CD437.

Acidic fibroblast growth factor attenuates the cytotoxic effects of peroxynitrite in primary human osteoblast precursors

BACKGROUND

Skeletal injury and associated ischemia and inflammation induce the generation of pro-oxidants such as peroxynitrite (ONOO-), which has been demonstrated to induce apoptosis in several cell lines. Fibroblast growth factor (FGF-1) is important for coordinating osteogenesis and angiogenesis of osseous repair. In vitro studies were performed examining the effect of FGF-1 on human osteoblast progenitor stromal stem (HSS) cell proliferation, differentiation, and response to ONOO-.

METHODS

HSS cells were isolated and growth kinetics determined in the presence and absence of FGF-1. The effect of FGF-1 on HSS cell expression of osteoblast-specific osteopontin and osteocalcin mRNA and protein was examined by reverse transcriptase polymerase chain reaction and Western blot techniques. To determine the sensitivity of HSS cells to ONOO- in the absence and presence of FGF-1 pretreatment, cells were exposed to varying concentrations of the oxidant and examined for cell death using quantitative fluorescence staining with fluorescein diacetate and propidium diacetate.

RESULTS

Treatment of HSS cells with FGF-1 significantly enhanced cellular growth rates by 5 days (4.6 x 105 cells/mL vs. 3.1 x 105 cells/mL) and induced expression of both osteopontin and osteocalcin mRNA and protein. Exposure of HSS cells to ONOO- resulted in a dose- and time-dependent delayed cell death that was more characteristic of apoptosis than necrosis. Pretreatment of HSS cells with FGF-1 prevented ONOO- mediated apoptosis.

CONCLUSION

In vitro, treatment of HSS cells with FGF-1 stimulates cell growth and induces expression of differentiation markers specific to osteoblasts. FGF-1 treatment renders osteoblast precursors resistant to the cytotoxic effects of ONOO-. These results suggest that FGF-1 promotes the progression of bone repair mechanisms by increasing the population of osteoblasts and imparting protection to the cell line from the hostile inflammatory environment.

Fibroblast growth factors: an epigenetic mechanism of broad spectrum resistance to anticancer drugs

Based on the observation that removal of tumors from metastatic organs reversed their chemoresistance, we hypothesized that chemoresistance is induced by extracellular factors in tumor-bearing organs. By comparing chemosensitivity and proteins in different tumors (primary vs. metastases) and different culture systems (tumor fragment histocultures vs. monolayer cultures derived from the same tumor), we found elevated levels of acidic (aFGF) and basic (bFGF) fibroblast growth factors in the conditioned medium (CM) of solid and metastatic tumors. These CM induced broad spectrum resistance to drugs with diverse structures and action mechanisms (paclitaxel, doxorubicin, 5-fluorouracil). Inhibition of bFGF by mAb and its removal by immunoprecipitation resulted in complete reversal of the CM-induced chemoresistance, whereas inhibition/removal of aFGF resulted in partial reversal. Using CM that had been depleted of aFGF and/or bFGF and subsequently reconstituted with respective human recombinant proteins, we found that bFGF but not aFGF induced chemoresistance whereas aFGF amplified the bFGF effect. aFGF and bFGF fully accounted for the CM effect, indicating these proteins as the underlying mechanism of the chemoresistance. The FGF-induced resistance was not due to reduced intracellular drug accumulation or altered cell proliferation. We further showed that an inhibitor of aFGF/bFGF (suramin) enhanced the in vitro and in vivo activity of chemotherapy, resulting in shrinkage and eradication of well established human lung metastases in mice without enhancing toxicity. These results indicate elevated levels of extracellular aFGF/bFGF as an epigenetic mechanism by which cancer cells elude cytotoxic insult by chemotherapy, and provide a basis for designing new treatment strategies.

Adenovirus-mediated acidic fibroblast growth factor gene transfer induces angiogenesis in the nonischemic rabbit heart

Most patients with severe coronary artery disease have normal baseline myocardial blood flow. Therefore, interventions aimed at inducing therapeutic angiogenesis in these patients should cause new blood vessel growth in the heart in the absence of chronic ischemia. It was examined whether adenovirus-mediated gene transfer of recombinant, secreted acidic fibroblast growth factor (sp+aFGF(1-154)), next to a major epicardial artery, may induce neovascularization and reduce the risk region for myocardial infarction upon coronary ligation near the injection site. Fifteen days prior to coronary artery occlusion, rabbits were treated with intramyocardial injections of AdCMV.sp+aFGF(1-154), the control vector AdCMV.NLSbetagal (1 x 10(9) plaque-forming units), or saline. Messenger RNA transcripts for aFGF(1-154) were present up to 12 days after injection in the tissues exposed to AdCMV.aFGF(1-154). Following coronary artery occlusion rabbits treated with AdCMV. sp+aFGF(1-154) showed a 50% reduction of the risk region for myocardial infarction (P < 0.01 vs control). Histologic analysis showed a twofold increase in length density of intramural coronary arterioles (P < 0.01 vs control) and a 17% increase in length density of the capillary network (P < 0.001) in the myocardium exposed to AdCMV.sp+aFGF(1-154). Thus, gene therapy with AdCMV. sp+aFGF(1-154) can induce angiogenesis in the absence of chronic ischemia. The newly formed collateral blood vessels provide an anatomical basis for the reduction in the risk region for myocardial infarction upon subsequent occlusion of the coronary artery in proximity of the site where angiogenesis was induced.