Mechanisms Of Fibroblast Growth Factor Research Articles

The FGF-2-Derived Peptide FREG Inhibits Melanoma Growth In Vitro and In Vivo

Previous data report that fibroblast growth factor-2 (FGF-2)-derived peptide FREG potently inhibits FGF-2-dependent angiogenesis in vitro and in vivo. Here, we show that FREG inhibits up to 70% in vitro growth and invasion/migration of smooth muscle and melanoma cells. Such inhibition is mediated by platelet-derived growth factor-receptor-α (PDGF-Rα); in fact, proliferation and migration were restored upon PDGF-Rα neutralization. Further experiments demonstrated that FREG interacts with PDGF-Rα both in vitro and in vivo and stimulates its phosphorylation. We have previously shown that overexpressing PDGF-Rα strongly inhibits melanoma growth in vivo; we, therefore, hypothesized that PDGF-Rα agonists may represent a novel tool to inhibit melanoma growth in vivo. To support this hypothesis, FREG was inoculated intravenously (i.v.) in a mouse melanoma model and markedly inhibited pulmonary metastases formation. Immunohistochemical analyses showed less proliferation, less angiogenesis, and more apoptosis in metastasized lungs upon FREG treatment, as compared to untreated controls. Finally, in preliminary acute toxicity studies, FREG showed no toxicity signs in healthy animals, and neither microscopic nor macroscopic toxicity at the liver, kidney, and lungs level. Altogether, these data indicate that FREG systemic treatment strongly inhibits melanoma metastases development and indicate for the first time that agonists of PDGF-Rα may control melanoma both in vitro and in vivo.

Autocrine/Paracrine Action of Vitamin D on FGF23 Expression in Cultured Rat Osteoblasts

To explore the local mechanisms of fibroblast growth factor (FGF) 23 regulations, we examined the FGF23 expression patterns in an osteoblast culture model. The characteristics of cultured rat calvaria osteoblasts in half-confluence, confluence, osteoid deposition, and osteoid mineralization stages might reflect the proliferation, differentiation, maturation, and matrix mineralization stages, respectively. Compared with proliferating cells in half-confluence, FGF23 expression was upregulated by 7.5-fold at the mRNA level and 126% at the protein level in confluent differentiated cells as determined by real-time RT-PCR and Western blot analysis. Interestingly, mRNA levels of CYP27B1 (the gene coding for 1alpha-hydroxylase enzyme which catalyses the conversion of 1alpha,25-dihydroxyvitamin D, 1alpha,25[OH]2D, from its inactive form, 25-hydroxycholecalciferol, 25[OH]D) and CYP24A (the gene coding for 24-hydroxylase, a target gene of 1alpha,25[OH]2D) were significantly increased by twofold and 34-fold, respectively, in differentiated osteoblasts compared with proliferating cells. We next examined if the local production of 1alpha,25(OH)2D might contribute to the FGF23 upregulation. We cultured osteoblasts in serum-free medium with or without 25-(OH)D (the substrate of 1alpha-hydroxylase). FGF23 mRNA levels were increased in proliferating cells (16-fold) and in differentiated cells (28-fold) by the physiological dose of 25-(OH)D3 treatment. CYP27B1 was slightly but significantly upregulated and CYP24A was increased by 1,700-fold and 800-fold, respectively, in transcriptional levels. Because FGF23 was upregulated in confluent osteoblasts regardless of the presence or absence of 25-(OH)D in serum-free medium, we further examined the possible impact of cell communication on FGF23 expression. We treated osteoblasts with carbenoxolone, a gap junction Cx43 blocker in serum-free medium. The FGF23 mRNA level was reduced by 50% in confluent differentiated cells and slightly but not significantly reduced in half-confluent cells by carbenoxolone treatments. The results suggested that upregulation of FGF23 in differentiated osteoblast appeared to be due to increased autocrine/paracrine action of osteoblast-derived 1alpha,25(OH)2D and increased cell communication, which were identified in cultured rat calvaria osteoblasts. These results indicate that FGF23 expression was stimulated not only by circulating calcitriol but also by locally produced 1alpha,25(OH)2D. The local mechanisms of FGF23 expression remain to be characterized.

Autocrine/paracrine action of Vitamin D on FGF23 expression in cultured rat osteoblasts

To explore the local mechanisms of fibroblast growth factor (FGF) 23 regulations, we examined the FGF23 expression patterns in an osteoblast culture model. The characteristics of cultured rat calvaria osteoblasts in half-confluence, confluence, osteoid deposition, and osteoid mineralization stages might reflect the proliferation, differentiation, maturation, and matrix mineralization stages, respectively. Compared with proliferating cells in half-confluence, FGF23 expression was upregulated by 7.5-fold at the mRNA level and 126% at the protein level in confluent differentiated cells as determined by real-time RT-PCR and Western blot analysis. Interestingly, mRNA levels of CYP27B1 (the gene coding for 1α-hydroxylase enzyme which catalyses the conversion of 1α,25-dihydroxyvitamin D, 1α,25[OH]2D, from its inactive form, 25-hydroxycholecalciferol, 25[OH]D) and CYP24A (the gene coding for 24-hydroxylase, a target gene of 1α,25[OH]2D) were significantly increased by twofold and 34-fold, respectively, in differentiated osteoblasts compared with proliferating cells. We next examined if the local production of 1α,25(OH)2D might contribute to the FGF23 upregulation. We cultured osteoblasts in serum-free medium with or without 25-(OH)D (the substrate of 1α-hydroxylase). FGF23 mRNA levels were increased in proliferating cells (16-fold) and in differentiated cells (28-fold) by the physiological dose of 25-(OH)D3 treatment. CYP27B1 was slightly but significantly upregulated and CYP24A was increased by 1,700-fold and 800-fold, respectively, in transcriptional levels. Because FGF23 was upregulated in confluent osteoblasts regardless of the presence or absence of 25-(OH)D in serum-free medium, we further examined the possible impact of cell communication on FGF23 expression. We treated osteoblasts with carbenoxolone, a gap junction Cx43 blocker in serum-free medium. The FGF23 mRNA level was reduced by 50% in confluent differentiated cells and slightly but not significantly reduced in half-confluent cells by carbenoxolone treatments. The results suggested that upregulation of FGF23 in differentiated osteoblast appeared to be due to increased autocrine/paracrine action of osteoblast-derived 1α,25(OH)2D and increased cell communication, which were identified in cultured rat calvaria osteoblasts. These results indicate that FGF23 expression was stimulated not only by circulating calcitriol but also by locally produced 1α,25(OH)2D. The local mechanisms of FGF23 expression remain to be characterized.

Fibroblast growth factors in epithelial repair and cytoprotection.

Growth factors are polypeptides that stimulate the division of certain cell types at low concentrations. Fibroblast growth factor (FGF) 7 (FGF-7) and its homologue FGF-10 act specifically on various types of epithelial cells including keratinocytes of the skin, intestinal epithelial cells and hepatocytes. In addition, FGF-7 and FGF-10 have been shown to be more than growth factors: they can protect epithelial cells from damaging effects induced, for example, by radiation and oxidative stress. Therefore, they are currently in clinical trials for the treatment of oral mucositis, a severe side-effect of cancer therapy characterized by painful inflammation and ulceration of the oral epithelium. To gain insight into the mechanisms of FGF-7/FGF-10 action in epithelial cells, we searched for genes that are regulated by these growth factors. Indeed, we identified genes that help us to explain the mechanisms that underlie the effects of FGF-7. Most interestingly, several genes were identified that are likely to mediate the cytoprotective effect of FGF-7 for epithelial cells in vitro and possibly also in injured and diseased tissues in vivo.

Fibroblast growth factor-1-inducible gene FR-17 encodes a nonmuscle alpha-actinin isoform.

Polypeptide growth factor binding to cell surface receptors activates a cytoplasmic signaling cascade that ultimately promotes the expression of specific nuclear genes. As an approach to investigate the molecular mechanism of fibroblast growth factor (FGF)-1 mitogenic signaling, we have begun to identify and characterize FGF-1-inducible genes in murine NIH 3T3 cells. Here we report that one of these genes, termed FGF-regulated (FR)-17, is predicted to encode a nonmuscle isoform of alpha-actinin, an actin cross-linking protein found along microfilaments and in focal adhesion plaques. FGF-1 induction of alpha-actinin mRNA expression is first detectable at 2 h after mitogen addition and is dependent on the novo RNA and protein synthesis. Maximal alpha-actinin mRNA expression, corresponding to an approximately nineteenfold level of induction, is present after 12 h of FGF-1 stimulation. Western blot analysis indicated that FGF-1-stimulated cells also produce an increased amount of alpha-actinin protein. The FGF-1-related mitogen FGF-2, calf serum, several of the polypeptide growth factors present in serum, and the tumor promoter phorbol myristate acetate can also induce alpha-actinin mRNA expression. Finally, nonmuscle alpha-actinin mRNA is expressed in vivo in a tissue-specific manner, with relatively high levels detected in adult mouse intestine and kidney. These results indicate that nonmuscle alpha-actinin is a serum-, polypeptide growth factor-, and tumor promoter-inducible gene in mouse fibroblasts.