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Elena Tassi, Kevin McDonnell,
Krissa A Gibby,
Jason U Tilan,
Sung E Kim,
David P Kodack,
Marcel O Schmidt,
Ghada M Sharif,
Christopher S Wilcox,
William J Welch,
G Ian Gallicano,
Michael D Johnson,
Anna T Riegel,
Anton Wellstein
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ABSTRACT: Fibroblast growth factors (FGFs) participate in embryonic development, in maintenance of tissue homeostasis in the adult, and in various diseases. FGF-binding proteins (FGFBP) are secreted proteins that chaperone FGFs stored in the extracellular matrix to their receptor, and can thus modulate FGF signaling. FGFBP1 (alias BP1, FGF-BP1, or HBp17) expression is required for embryonic survival, can modulate FGF-dependent vascular permeability in embryos, and is an angiogenic switch in human cancers. To determine the function of BP1 in vivo, we generated tetracycline-regulated conditional BP1 transgenic mice. BP1-expressing adult mice are viable, fertile, and phenotypically indistinguishable from their littermates. Induction of BP1 expression increased mouse primary fibroblast motility in vitro, increased angiogenic sprouting into subcutaneous matrigel plugs in animals and accelerated the healing of excisional skin wounds. FGF-receptor kinase inhibitors blocked these effects. Healing skin wounds showed increased macrophage invasion as well as cell proliferation after BP1 expression. Also, BP1 expression increased angiogenesis during the healing of skin wounds as well as after ischemic injury to hindlimb skeletal muscles. We conclude that BP1 can enhance FGF effects that are required for the healing and repair of injured tissues in adult animals.
American Journal Of Pathology 09/2011; 179(5):2220-32. · 4.89 Impact Factor
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ABSTRACT: FGFs modulate diverse biological processes including embryonic development. Secreted FGF-binding proteins (BPs) can release FGFs from their local extracellular matrix storage, chaperone them to their cognate receptors, and thus modulate FGF signaling. Here we describe 2 chicken BP homologs (chBP) that show distinct expression peaks at embryonic days E7.5 (chBP2) and E11.5 (chBP1), although their tissue distribution is similar (skin = intestine>lung>heart, liver). Embryos were grown ex ovo to monitor the phenotypic impact of a timed in vivo knockdown of expression peaks by microinjection of specific siRNAs targeted to either of the chBPs. Knockdown of peak expression of chBP2 caused embryonic lethality within <5 days. Surviving embryos showed defective ventral wall closure indicative of altered dorsoventral patterning. This defect coincided with reduced expression of HoxB7 but not HoxB8 that are involved in the control of thoracic/abdominal segment morphology. Also, MAPK phosphatase 3, a negative regulator of FGF signaling, and sonic hedgehog that can participate in feedback control of the FGF pathway were reduced, reflecting altered FGF signaling. Knockdown of the chBP1 expression peak caused embryonic lethality within <3 days although no distinct morphologic phenotype or pathways alterations were apparent. We conclude that BPs play a significant role in fine-tuning the complex FGF signaling network during distinct phases of embryonic development.
Proceedings of the National Academy of Sciences 05/2009; 106(21):8585-90. · 9.68 Impact Factor
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ABSTRACT: Fibroblast growth factor-binding proteins (FGF-BP) are secreted carrier proteins that release fibroblast growth factors (FGFs) from the extracellular matrix storage and thus enhance FGF activity. Here we have mapped the interaction domain between human FGF-BP1 and FGF-2. For this, we generated T7 phage display libraries of N-terminally and C-terminally truncated FGF-BP1 fragments that were then panned against immobilized FGF-2. From this panning, a C-terminal fragment of FGF-BP1 (amino acids 193-234) was identified as the minimum binding domain for FGF. As a recombinant protein, this C-terminal fragment binds to FGF-2 and enhances FGF-2-induced signaling in NIH-3T3 fibroblasts and GM7373 endothelial cells, as well as mitogenesis and chemotaxis of NIH-3T3 cells. The FGF interaction domain in FGF-BP1 is distinct from the heparin-binding domain (amino acids 110-143), and homology modeling supports the notion of a distinct domain in the C terminus that is conserved across different species. This domain also contains conserved positioning of cysteine residues with the Cys-214/Cys-222 positions in the human protein predicted to participate in disulfide bridge formation. Phage display of a C214A mutation of FGF-BP1 reduced binding to FGF-2, indicating the functional significance of this disulfide bond. We concluded that the FGF interaction domain is contained in the C terminus of FGF-BP1.
Journal of Biological Chemistry 02/2006; 281(2):1137-44. · 4.77 Impact Factor
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ABSTRACT: ancer metastasis, the spread of cancer from its primary location to secondary sites, heralds the progression to a fundamentally
distinct oncologic disease. Metastatic infiltration often disrupts the integrity and physiologic functioning of the target
organ, giving rise to the pain, morbidity, and mortality that make metastatic disease such a devastating illness.
12/2005: pages 244-253;
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ABSTRACT: Fibroblast growth factors (FGFs) have been implicated in a variety of physiologic and pathologic processes from embryonic development to tumor growth and angiogenesis. FGFs are immobilized in the extracellular matrix of different tissues and require release from this storage site to trigger a response. Secreted FGF-binding proteins (FGF-BPs) can release immobilized FGFs, enhance the activity of locally stored FGFs and can thus serve as an angiogenic switch molecule in cancer. Here, we report on the effect of human FGF-BP transgene expression in chicken embryos. To establish the transgenic model, plasmid-based reporter vectors expressing luciferase, beta-galactosidase or green fluorescent protein were introduced through different routes into 4- to 5-day-old embryos grown outside their egg shell on top of the yolk sac. This allows for easy manipulation and continuous observation of phenotypic effects. Expression of human FGF-BP induced dose-dependent vascular permeability, hemorrhage and embryonic lethality. Light and electron microscopic studies indicate that this hemorrhage results from compromised microvascular structure. An FGF-1 expression vector with an added secretory signal mimicked this vascular leakiness phenotype whereas wild-type FGF-1 required coexpression of a threshold amount of FGF-BP. This model is a powerful tool for real-time monitoring of the effects of transient transgene expression during embryogenesis.
Laboratory Investigation 07/2005; 85(6):747-55. · 3.64 Impact Factor
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ABSTRACT: Amplified in breast cancer 1 (AIB1, also known as ACTR, SRC-3, RAC-3, TRAM-1, p/CIP) is a member of the p160 nuclear receptor coactivator family involved in transcriptional regulation of genes activated through steroid receptors, such as estrogen receptor alpha (ER(alpha)). The AIB1 gene and a more active N-terminally deleted isoform (AIB1-Delta3) are overexpressed in breast cancer. To determine the role of AIB1-Delta3 in breast cancer pathogenesis, we generated transgenic mice with human cytomegalovirus immediate early gene 1 (hCMVIE1) promoter-driven over-expression of human AIB1/ACTR-Delta3 (CMVAIB1/ACTR-Delta3 mice). AIB1/ACTR-Delta3 transgene mRNA expression was confirmed in CMV-AIB1/ACTR-Delta3 mammary glands by in situ hybridization. These mice demonstrated significantly increased mammary epithelial cell proliferation (P < 0.003), cyclin D1 expression (P = 0.002), IGF-I receptor protein expression (P = 0.026), mammary gland mass (P < 0.05), and altered expression of CCAAT/enhancer binding protein isoforms (P = 0.029). At 13 months of age, mammary ductal ectasia was found in CMV-AIB1/ACTR-Delta3 mice, but secondary and tertiary branching patterns were normal. There were no changes in the expression patterns of either ER(alpha) or Stat5a, a downstream mediator of prolactin signaling. Serum IGF-I levels were not altered in the transgenic mice. These data indicate that overexpression of the AIB1/ACTR-Delta3 isoform resulted in altered mammary epithelial cell growth. The observed changes in cell proliferation and gene expression are consistent with alterations in growth factor signaling that are thought to contribute to either initiation or progression of breast cancer. These results are consistent with the hypothesis that the N-terminally deleted isoform of AIB1 can play a role in breast cancer development and/or progression.
Molecular Endocrinology 03/2005; 19(3):644-56. · 4.54 Impact Factor
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ABSTRACT: Regulation of phosphate (Pi) reabsorption occurs through the up- and downregulation of the renal type-II sodium Pi cotransporters (NaPi-2). Recently, renal NaPi2-type expression has been identified in areas of the brain. The present study determined whether brain NaPi-2 is regulated by dietary Pi and whether the behavioral and renal adaptations to low-dietary Pi are controlled centrally. NaPi-2-like expression in the third ventricle (3V) and amygdala of juvenile Wistar rats was regulated by dietary Pi, as in the kidneys. When cerebrospinal fluid (CSF) Pi concentration was elevated by 3V injections of Pi in rats fed low-Pi diet (LPD), the behavioral and renal adaptations to LPD were abolished. Most importantly, NaPi-2 expression was markedly reduced not only in the brain, but also renal proximal tubules, despite the low plasma Pi milieu. This was confirmed by the significant reduction in the transport maximum for Pi (from 8.1+/-0.2 in LPD + veh 3V to 1.7+/-0.1 micromol Pi/ml glomerular filtration rate in LPD + 3V Pi, P < 0.001). These findings indicate that NaPi-2-like transporters in the brain are regulated by both dietary Pi and CSF Pi concentrations, and most significantly, that the central Pi milieu can regulate renal NaPi-2 expression. We hypothesize that central 3V NaPi-2 transporters may act as Pi sensors and help regulate both brain and whole body Pi homeostasis.
American journal of physiology. Renal physiology 04/2004; 286(4):F647-52. · 3.68 Impact Factor
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ABSTRACT: In humans, HIV infection reduces growth hormone (GH) secretion contributing to AIDS wasting. In rats, the HIV envelope protein gp120 alone blocks GH secretion both in vitro and in vivo through GH-releasing hormone receptors. Peptide T, a modified octapeptide derived from gp120, normalizes GH secretion. We now report that an intravenous bolus of peptide T normalizes nocturnal GH secretion in two out of three children with AIDS. These results, coupled with the lack of toxicity of this experimental AIDS therapeutic, justify clinical trials for AIDS wasting and pediatric AIDS. A clinical and basic science update on peptide T appears in Current HIV Research.
Peptides 01/2003; 23(12):2279-81. · 2.43 Impact Factor
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ABSTRACT: Glioblastoma multiforme is the most common highly aggressive human brain cancer, and receptor tyrosine kinases have been implicated in the progression of this malignancy. We have recently identified anaplastic lymphoma kinase (ALK) as a tyrosine kinase receptor for pleiotrophin, a secreted growth factor that is highly expressed during embryonic brain development and in tumors of the central nervous system. Here we report on the contribution of pleiotrophin-ALK signaling to glioblastoma growth. We found ALK overexpressed in human glioblastoma relative to normal brain and detected ALK mRNA in glioblastoma cell lines. We reduced the endogenous ALK in glioblastoma cells by ribozyme targeting and demonstrated that this prevents pleiotrophin-stimulated phosphorylation of the anti-apoptotic protein Akt. Furthermore, this depletion of ALK reduced tumor growth of xenografts in athymic nude mice and prolonged survival of the animals because of increased apoptosis in the tumors. These findings directly implicate ALK signaling as a rate-limiting factor in the growth of glioblastoma multiforme and suggest potential utility of therapeutic targeting of ALK.
Journal of Biological Chemistry 05/2002; 277(16):14153-8. · 4.77 Impact Factor
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