Fibroblast growth factor receptor tyrosine kinases: molecular analysis and signal transduction

Senescent cells promote breast cancer cells motility by secreting GM-CSF and bFGF that activate the JNK signaling pathway

BACKGROUND

Cellular senescence can be induced in mammalian tissues by multiple stimuli, including aging, oncogene activation and loss of tumor suppressor genes, and various types of stresses. While senescence is a tumor suppressing mechanism when induced within premalignant or malignant tumor cells, senescent cells can promote cancer development through increased secretion of growth factors, cytokines, chemokines, extracellular matrix, and degradative enzymes, collectively known as senescence-associated secretory phenotype (SASP). Previous studies indicated that senescent cells, through SASP factors, stimulate tumor cell invasion that is a critical step in cancer cell metastasis.

METHODS

In the current study, we investigated the effect of senescent cells on the motility of breast cancer cells, which is another key step in cancer cell metastasis. We analyzed the motility of breast cancer cells co-cultured with senescent cells in vitro and metastasis of the breast cancer cells co-injected with senescent cells in orthotopic xenograft models. We also delineated the signaling pathway mediating the effect of senescent cells on cancer cell motility.

RESULTS

Our results indicate that senescent cells stimulated the migration of breast cancer cells through secretion of GM-CSF and bFGF, which in turn induced activation of the JNK pathway in cancer cells. More importantly, senescent cells promoted breast cancer metastasis, with a minimum effect on the primary tumor growth, in orthotopic xenograft mouse models.

CONCLUSIONS

These results have revealed an additional mechanism by which senescent cells promote tumor cell metastasis and tumor progression, and will potentially lead to identification of novel targets for cancer therapies that suppress metastasis, the major cause of cancer mortality.

FGF receptors mediate cellular senescence in the cystic fibrosis airway epithelium

The number of adults living with cystic fibrosis (CF) has already increased significantly because of drastic improvements in life expectancy attributable to advances in treatment, including the development of highly effective modulator therapy. Chronic airway inflammation in CF contributes to morbidity and mortality, and aging processes like inflammaging and cell senescence influence CF pathology. Our results show that single-cell RNA sequencing data, human primary bronchial epithelial cells from non-CF and CF donors, a CF bronchial epithelial cell line, and Cftr-knockout (Cftr-/-) rats all demonstrated increased cell senescence markers in the CF bronchial epithelium. This was associated with upregulation of fibroblast growth factor receptors (FGFRs) and mitogen-activated protein kinase (MAPK) p38. Inhibition of FGFRs, specifically FGFR4 and to some extent FGFR1, attenuated cell senescence and improved mucociliary clearance, which was associated with MAPK p38 signaling. Mucociliary dysfunction could also be improved using a combination of senolytics in a CF ex vivo model. In summary, FGFR/MAPK p38 signaling contributes to cell senescence in CF airways, which is associated with impaired mucociliary clearance. Therefore, attenuation of cell senescence in the CF airways might be a future therapeutic strategy improving mucociliary dysfunction and lung disease in an aging population with CF.

Coarse-Grained Model of Glycosaminoglycans for Biomolecular Simulations

Proteoglycans contain glycosaminoglycans (GAGs) which are negatively charged linear polymers made of repeating disaccharide units of uronic acid and hexosamine units. They play vital roles in numerous physiological and pathological processes, particularly in governing cellular communication and attachment. Depending on their sulfonation state, acetylation, and glycosidic linkages, GAGs belong to different families. The high molecular weight, heterogeneity, and flexibility of GAGs hamper their characterization at atomic resolution, but this may be circumvented via coarse-grained (CG) approaches. In this work, we report a CG model for a library of common GAG types in their isolated or proteoglycan-linked states compatible with version 2.2 (v2.2) of the widely popular CG Martini force field. The model reproduces conformational and thermodynamic properties for a wide variety of GAGs, as well as matching structural and binding data for selected proteoglycan test systems. The parameters developed here may thus be employed to study a range of GAG-containing biomolecular systems, thereby benefiting from the efficiency and broad applicability of the Martini framework.

The role of microglial activation on ischemic stroke: Modulation by fibroblast growth factors

Stroke is one of the devastating clinical conditions that causes death and permanent disability. Its occurrence causes the reduction of oxygen and glucose supply, resulting in events such as inflammatory response, oxidative stress, and apoptosis in the brain. Microglia are brain-resident immune cells in the central nervous system (CNS) that exert diverse roles and respond to pathological process after an ischemic insult. The discovery of fibroblast growth factors (FGFs) in mammals, resulted to the findings that they can treat experimental models of stroke in animals effectively. FGFs function as homeostatic factors that control cells and hormones involved in metabolism, and they also regulate the secretion of proinflammatory (M1) and anti-inflammatory (M2) cytokines after stroke. In this review, we outline current evidence of microglia activation in experimental models of stroke focusing on its ability to exacerbate damage or repair tissue. Also, our review sheds light on the pharmacological actions of FGFs on multiple targets to regulate microglial modulation and highlighted their theoretical molecular mechanisms to provide possible therapeutic targets, as well as their limitations for the treatment of stroke. DATA AVAILABILITY: Not applicable.

Roles of Fibroblast Growth Factors in the Axon Guidance

Fibroblast growth factors (FGFs) have been widely studied by virtue of their ability to regulate many essential cellular activities, including proliferation, survival, migration, differentiation and metabolism. Recently, these molecules have emerged as the key components in forming the intricate connections within the nervous system. FGF and FGF receptor (FGFR) signaling pathways play important roles in axon guidance as axons navigate toward their synaptic targets. This review offers a current account of axonal navigation functions performed by FGFs, which operate as chemoattractants and/or chemorepellents in different circumstances. Meanwhile, detailed mechanisms behind the axon guidance process are elaborated, which are related to intracellular signaling integration and cytoskeleton dynamics.

Characterization of fibroblast growth factor receptor 4 (FGFR4) from the red swamp crayfish Procambarus clarkii and its role in antiviral and antimicrobial immune responses

FGFRs involved multiple physiological processes, such as endocrine homeostasis, wound repair, and cellular behaviors including proliferation, differentiation and survival. In the present study, the homologs of fibroblast growth factor receptor 4 (FGFR4) were identified and characterized from the red swamp crayfish Procambarus clarkii for the first time. The full-length cDNAs of pcFGFR4 were 2878 bp with 2451 bp open reading frame (ORF), respectively. The deduced pcFGFR4 protein contained an immunoglobulin, two immunoglobulin C-2 Type, a transmembrane region and a catalytic domain. Real-time PCR analysis showed that pcFGFR4 were highly expressed in muscle and hemocyte. Moreover, the expression levels of pcFGFR4 in the hepatopancreas and hemocyte were positively stimulated after challenge with Aeromonas hydrophila and WSSV, implying the involvement of pcFGFR4 against bacterial and viral infections in innate immune responses. While pcFGFR4 were silenced in vivo, the expression levels of antimicrobial peptide (AMP) genes (pcALF1-5,8 and pcCrustin1-2) and NF-κB signaling components (pcDrosal and pcRelish) were significantly reduced. Additionally, NF-κB signaling could be markedly activated by overexpression of pcFGFR4 in HEK293T cells. Finally, our results indicated that pcFGFR4 regulated crayfish's innate immunity by modulating NF-κB signaling. These findings may provide new insights into pcFGFR4-mediated signaling cascades in crustaceans and provide a better understanding of crustacean innate immune system.

Glucagon-like peptide 1 and fibroblast growth factor-21 in non-alcoholic steatohepatitis: An experimental to clinical perspective

Non-alcoholic steatohepatitis (NASH) is a progressive form of Non-alcoholic fatty liver disease (NAFLD), which slowly progresses toward cirrhosis and finally leads to the development of hepatocellular carcinoma. Obesity, insulin resistance, type 2 diabetes mellitus and the metabolic syndrome are major risk factors contributing to NAFLD. Targeting these risk factors is a rational option for inhibiting NASH progression. In addition, NASH could be treated with therapies that target the metabolic abnormalities causing disease pathogenesis (such as de novo lipogenesis and insulin resistance) as well with medications targeting downstream processes such as cellular damage, apoptosis, inflammation, and fibrosis. Glucagon-like peptide (GLP-1), is an incretin hormone dysregulated in both experimental and clinical NASH, which triggers many signaling pathways including fibroblast growth factor (FGF) that augments NASH pathogenesis. Growing evidence indicates that GLP-1 in concert with FGF-21 plays crucial roles in the conservation of glucose and lipid homeostasis in metabolic disorders. In line, GLP-1 stimulation improves hepatic ballooning, steatosis, and fibrosis in NASH. A recent clinical trial on NASH patients showed that the upregulation of FGF-21 decreases liver fibrosis and hepatic steatosis, thus improving the pathogenesis of NASH. Hence, therapeutic targeting of the GLP-1/FGF axis could be therapeutically beneficial for the remission of NASH. This review outlines the significance of the GLP-1/FGF-21 axis in experimental and clinical NASH and highlights the activity of modulators targeting this axis as potential salutary agents for the treatment of NASH.

Negative regulation of receptor tyrosine kinases by ubiquitination: Key roles of the Cbl family of E3 ubiquitin ligases

Receptor tyrosine kinases (RTKs) serve as transmembrane receptors that participate in a broad spectrum of cellular processes including cellular growth, motility, differentiation, proliferation, and metabolism. Hence, elucidating the regulatory mechanisms of RTKs involved in an assortment of diseases such as cancers attracts increasing interest from researchers. Members of the Cbl family ubiquitin ligases (c-Cbl, Cbl-b and Cbl-c in mammals) have emerged as negative regulators of activated RTKs. Upon activation of RTKs by growth factors, Cbl binds to RTKs via its tyrosine kinase binding (TKB) domain and targets them for ubiquitination, thus facilitating their degradation and negative regulation of RTK signaling. RTKs such as epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGF), fibroblast growth factor receptor (FGFR) and hepatocyte growth factor receptor (HGFR) undergo ubiquitination upon interaction with Cbl family members. In this review, we summarize the current knowledge related to the negative regulation of RTKs by Cbl family proteins.

Posttranslational Modification Defects in Fibroblast Growth Factor Receptor 1 as a Reason for Normosmic Isolated Hypogonadotropic Hypogonadism

Some mutations in FGFR1 affect the sense of smell while others do not, resulting in Kallmann syndrome (KS) and normosmic isolated hypogonadotropic hypogonadism (nIHH), respectively. The underlying mechanism is still unclear. FGFR1 variants are found in less than 10% of patients with KS and nIHH, and among them, only some have undergone functional analysis. Thus, the correlation between the phenotype and genotype cannot be clearly verified. This study reports a case of nIHH and explores the potential mechanism of the FGFR1 gene in the pathogenesis of nIHH. A preschooler with cryptorchidism, micropenis, strabismus, and hypopsia is described. As he had a normal sense of smell, he was diagnosed with nIHH. A de novo mutation in FGFR1 (c.2008G>A) was detected in the patient along with a novel variant in CEP290 (c.964G>A) inherited from his mother. We present compelling in vitro evidence that this FGFR1 mutation-induced posttranslational modification defect, including defective glycosylation and impaired trans-autophosphorylation, along with the final reduction in expression, could lead to impairment of the receptor and abnormal signaling and eventually result in developmental abnormalities and inhibition of GnRH neuron release. The identification of an additional variant suggests that CEP290 might play a potential role in GnRH development.

STAU1 selectively regulates the expression of inflammatory and immune response genes and alternative splicing of the nerve growth factor receptor signaling pathway

Double‑stranded RNA‑binding protein Staufen homolog 1 (STAU1) is a highly conserved multifunctional double‑stranded RNA‑binding protein, and is a key factor in neuronal differentiation. RNA sequencing was used to analyze the overall transcriptional levels of the upregulated cells by STAU1 and control cells, and select alternative splicing (AS). It was determined that the high expression of STAU1 led to changes in the expression levels of a variety of inflammatory and immune response genes, including IFIT2, IFIT3, OASL, and CCL2. Furthermore, STAU1 was revealed to exert a significant regulatory effect on the AS of genes related to the 'nerve growth factor receptor signaling pathway'. This is of significant importance for neuronal survival, differentiation, growth, post‑damage repair, and regeneration. In conclusion, overexpression of STAU1 was associated with immune response and regulated AS of pathways related to neuronal growth and repair. In the present study, the whole transcriptome of STAU1 expression was first analyzed, which laid a foundation for further understanding the key functions of STAU1.

Fibroblast Growth Factor (FGF) Signaling Protects Against Acute Pancreatitis-Induced Damage by Modulating Inflammatory Responses

BACKGROUND Acute pancreatitis (AP) is a symptom of sudden pancreas inflammation, which causes patients severe suffering. In general, fibroblast growth factor (FGF) levels are increased and amylase and lipase activities are elevated during AP pathogenesis, but protein concentration are low. However, the mechanism through which FGF signaling regulates AP pathogenesis remains elusive. MATERIAL AND METHODS The concentrations of PGE2, TNF-alpha, sCRP, FGF1, and FGF2 in the serum samples of the AP group and healthy control group were detected by enzyme-linked immunosorbent assay. In addition, IkappaBalpha and p-IkappaBalpha levels were analyzed in the serum samples. Subsequently, the AP rat model was established, and FGF1, FGF2, anti-FGF1, and anti-FGF2 antibodies and Bay11-7082 were injected into AP rats. TNF-alpha, PAI-1 JNK, p-JNK, IkappaBalpha, and p-IkappaBalpha levels were also examined. RESULTS Results showed that levels of PGE2, TNF-alpha, sCRP, p-IkappaBalpha, FGF1, and FGF2, as well as amylase and lipase activity were increased in patients with AP compared with those in healthy people. In addition, protein concentrations were lower in patients with AP than in the healthy group. Activation of FGF signaling by injecting FGF1 or FGF2 also inhibited AP-induced inflammation response in the pancreas and increased amylase and lipase activities, as well as protein concentration. However, the injection of FGF1 and FGF2 antibodies accelerated AP-mediated inflammation responses in the serum. In addition, Bay11-7082 injection inhibited AP activation of inflammation response and amylase and lipase activities. Protein concentration were also increased in AP rats. CONCLUSIONS FGF signaling protects against AP-mediated damage by inhibition of AP-activating inflammatory responses.

miR-671-5p Blocks The Progression Of Human Esophageal Squamous Cell Carcinoma By Suppressing FGFR2

Esophageal cancer is the eighth most common malignant tumor worldwide, of which esophageal squamous cell carcinoma (ESCC) is the dominant histological subtype. A drug shortage for ESCC therapy triggered us to explore the roles of fibroblast growth factor receptor 2 (FGFR2) and its upstream regulator miR-671-5p in ESCC progression. We compared the levels of FGFR2 and miR-671-5p between human ESCC tissues and their matched normal esophageal tissues and found an association between higher levels of FGFR2 and lower levels of miR-671-5p in ESCC tissues. High levels of FGFR2 resulted in the activation of the ERK and AKT pathways and a promotion of ESCC progression. High levels of miR-671-5p specifically reduced the expression of FGFR2 and suppressed ESCC progression in both in vitro and in vivo models. Therefore, suppressing FGFR2 and enhancing miR-671-5p expression may be the right approaches for ESCC therapy.

Immunohistochemical expression pattern of RIP5, FGFR1, FGFR2 and HIP2 in the normal human kidney development

AIM

Present study analyses the co-localisation of RIP5 with FGFR1, FGFR2 and HIP2 in the developing kidney, as RIP5 is a major determinant of urinary tract development, downstream of FGF-signaling.

METHODS

Paraffin embedded human kidney tissues of 16 conceptuses between the 6th-22th developmental week were analysed using double-immunofluorescence method with RIP5/FGFR1/FGFR2 and HIP2 markers. Quantification of positive cells were performed using Kruskal-Wallis test.

RESULTS

In the 6th week of kidney development RIP5 (89.6%) and HIP2 (39.6%) are strongly expressed in the metanephric mesenchyme. FGFR1 shows moderate/strong expression in the developing nephrons (87.3%) and collecting ducts (70.5%) (p < 0.05). RIP5/FGFR1 co-localized at the marginal zone and the ureteric bud with predominant FGFR1 expression. FGFR2 (26.1%) shows similar expression pattern as FGFR1 (70.5%) in the same kidney structures. RIP5/FGFR2 co-localized at the marginal zone and the collecting ducts (predominant expression of FGFR2). HIP2 is strongly expressed in collecting ducts (96.7%), and co-localized with RIP5. In 10th week, RIP5 expression decrease (74.2%), while the pattern of expression of RIP5 and FGFR1 in collecting ducts (33.4% and 91.9%) and developing nephrons (21.9% and 32.4%) (p < 0.05) is similar to that in the 6th developmental week. Ureter is moderately expressing RIP5 while FGFR1 is strongly expressed in the ureteric wall. FGFR2 is strongly expressed in the collecting ducts (84.3%) and ureter. HIP2 have 81.1% positive cells in the collecting duct. RIP5/FGFR1 co-localize in collecting ducts and Henley's loop.

CONCLUSIONS

The expression pattern of RIP5, FGFR1, FGFR2 and HIP2 in the human kidney development might indicate their important roles in metanephric development and ureteric muscle layer differentiation through FGF signaling pathways.

The Inhibitory Effect of Propylene Glycol Alginate Sodium Sulfate on Fibroblast Growth Factor 2-Mediated Angiogenesis and Invasion in Murine Melanoma B16-F10 Cells In Vitro

Melanoma is one of the most malignant and aggressive types of cancer worldwide. Fibroblast growth factor 2 (FGF2) is one of the critical regulators of melanoma angiogenesis and metastasis; thus, it might be an effective anti-cancer strategy to explore FGF2-targeting drug candidates from existing drugs. In this study, we evaluate the effect of the marine drug propylene glycol alginate sodium sulfate (PSS) on FGF2-mediated angiogenesis and invasion. The data shows that FGF2 selectively bound to PSS with high affinity. PSS inhibited FGF2-mediated angiogenesis in a rat aortic ring model and suppressed FGF2-mediated invasion, but not the migration of murine melanoma B16-F10 cells. The further mechanism study indicates that PSS decreased the expression of activated matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9), and also suppressed their activity. In addition, PSS was found to decrease the level of Vimentin in B16-F10 cells, which is known to participate in the epithelial-mesenchymal transition. Notably, PSS did not elicit any changes in cancer cell viability. Based on the results above, we conclude that PSS might be a potential drug to regulate the tumor microenvironment in order to facilitate the recovery of melanoma patients.

Genetic Causes of Craniosynostosis: An Update

In 1993, Jabs et al. were the first to describe a genetic origin of craniosynostosis. Since this discovery, the genetic causes of the most common syndromes have been described. In 2015, a total of 57 human genes were reported for which there had been evidence that mutations were causally related to craniosynostosis. Facilitated by rapid technological developments, many others have been identified since then. Reviewing the literature, we characterize the most common craniosynostosis syndromes followed by a description of the novel causes that were identified between January 2015 and December 2017.

Heparan Sulfate Domains Required for Fibroblast Growth Factor 1 and 2 Signaling through Fibroblast Growth Factor Receptor 1c

A small library of well defined heparan sulfate (HS) polysaccharides was chemoenzymatically synthesized and used for a detailed structure-activity study of fibroblast growth factor (FGF) 1 and FGF2 signaling through FGF receptor (FGFR) 1c. The HS polysaccharide tested contained both undersulfated (NA) domains and highly sulfated (NS) domains as well as very well defined non-reducing termini. This study examines differences in the HS selectivity of the positive canyons of the FGF12-FGFR1c2 and FGF22-FGFR1c2 HS binding sites of the symmetric FGF2-FGFR2-HS2 signal transduction complex. The results suggest that FGF12-FGFR1c2 binding site prefers a longer NS domain at the non-reducing terminus than FGF22-FGFR1c2 In addition, FGF22-FGFR1c2 can tolerate an HS chain having an N-acetylglucosamine residue at its non-reducing end. These results clearly demonstrate the different specificity of FGF12-FGFR1c2 and FGF22-FGFR1c2 for well defined HS structures and suggest that it is now possible to chemoenzymatically synthesize precise HS polysaccharides that can selectively mediate growth factor signaling. These HS polysaccharides might be useful in both understanding and controlling the growth, proliferation, and differentiation of cells in stem cell therapies, wound healing, and the treatment of cancer.

FGFR-associated craniosynostosis syndromes and gastrointestinal defects

Craniosynostosis is a relatively common birth defect characterized by the premature fusion of one or more cranial sutures. Examples of craniosynostosis syndromes include Crouzon (CS), Pfeiffer (PS), and Apert (AS) syndrome, with clinical characteristics such as midface hypoplasia, hypertelorism, and in some cases, limb defects. Mutations in Fibroblast Growth Factor Receptor-2 comprise the majority of known mutations in syndromic forms of craniosynostosis. A number of clinical reports of FGFR-associated craniosynostosis patients and mouse mutants have been linked to gastrointestinal tract (GIT) disorders, leading to the hypothesis of a direct link between FGFR-associated craniosynostosis syndromes and GIT malformations. We conducted an investigation to determine GIT symptoms in a sample of FGFR-associated craniosynostosis syndrome patients and a mouse model of CS containing a mutation (W290R) in Fgfr2. We found that, compared to the general population, the incidence of intestinal/bowel malrotation (IM) was present at a higher level in our sample population of patients with FGFR-associated craniosynostosis syndromes. We also showed that the mouse model of CS had an increased incidence of cecal displacement, suggestive of IM. These findings suggest a direct relationship between FGFR-related craniosynostosis syndromes and GIT malformations. Our study may shed further light on the potential widespread impact FGFR mutations on different developmental systems. Based on reports of GIT malformations in children with craniosynostosis syndromes and substantiation with our animal model, GIT malformations should be considered in any child with an FGFR2-associated craniosynostosis syndrome. © 2016 Wiley Periodicals, Inc.

FGF1 and FGF2 mutations in preeclampsia and related features

BACKGROUND

Fibroblast growth factor (FGF) 1 and FGF2 were previously linked with preeclampsia (PE), possibly through altering decidual and placental FGFR2 expression. Since common variation in FGF1 and FGF2 might influence FGF1 and FGF2 activity, this study evaluated whether common FGF1 and FGF2 variants are linked with PE and associated features.

METHODS

The association between FGF1 rs34011 and FGF2 rs2922979 SNPs and PE were tested in 300 women with PE, and 300 age-matched control women.

RESULTS

The allelic distribution of FGF1 rs34011 (P < 0.001) but not FGF2 rs2922979, variants were significantly different between PE cases and control women. Marginal association of FGF2 rs2922979 was seen after controlling for key covariates. Setting homozygous major allele genotype (1/1) as reference, significantly higher frequencies of heterozygous rs345011, and reduced frequency of heterozygous rs2922979 genotype carriers were seen in PE cases; the distribution of the remaining genotypes were comparable between cases and controls. Carriage of rs2922979 minor allele correlated with fasting glucose (P = 0.02), while the presence of rs34011 minor allele was not correlated with PE-associated features.

CONCLUSIONS

Our study suggests that the genetic variants of FGF1 rs34011, more so than FGF2 rs2922979, may play a role in PE pathogenesis in Tunisian women. These findings need confirmation in other ethnic populations.

Help-me signaling: Non-cell autonomous mechanisms of neuroprotection and neurorecovery

Self-preservation is required for life. At the cellular level, this fundamental principle is expressed in the form of molecular mechanisms for preconditioning and tolerance. When the cell is threatened, internal cascades of survival signaling become triggered to protect against cell death and defend against future insults. Recently, however, emerging findings suggest that this principle of self-preservation may involve not only intracellular signals; the release of extracellular signals may provide a way to recruit adjacent cells into an amplified protective program. In the central nervous system where multiple cell types co-exist, this mechanism would allow threatened neurons to "ask for help" from glial and vascular compartments. In this review, we describe this new concept of help-me signaling, wherein damaged or diseased neurons release signals that may shift glial and vascular cells into potentially beneficial phenotypes, and help remodel the neurovascular unit. Understanding and dissecting these non-cell autonomous mechanisms of self-preservation in the CNS may lead to novel opportunities for neuroprotection and neurorecovery.

Insights into the development of molecular therapies for craniosynostosis

For the past 2 decades, clinical and basic science researchers have gained significant insights into the molecular and genetic pathways associated with common forms of craniosynostosis. This has led to invaluable information for families and physicians in their attempts to understand the heterogeneity of craniosynostosis. Genetic mutations have been identified in the fibroblast growth factor receptors (FGFRs) as well as in other targets, including TWIST1, BMP, and RUNX2. Greater understanding of these and other pathways has led to the development of innovative approaches for applying medical therapies to the treatment of craniosynostosis, in particular by maintaining suture patency. In this article, the authors discuss the molecular pathophysiological mechanisms underlying various forms of craniosynostosis. They also highlight recent developments in the field of molecular craniosynostosis research with the hope of identifying targets for medical therapies that might augment the results of surgical intervention.

Nanoplex-Mediated Codelivery of Fibroblast Growth Factor and Bone Morphogenetic Protein Genes Promotes Osteogenesis in Human Adipocyte-Derived Mesenchymal Stem Cells

This study highlights the importance of transfection mediated coordinated bone morphogenetic protein 2 (BMP-2) and fibroblast growth factor 2 (FGF-2) signaling in promoting osteogenesis. We employed plasmids independently encoding BMP-2 and FGF-2 complexed with polyethylenimine (PEI) to transfect human adipose derived mesenchymal stem cells (hADMSCs) in vitro. The nanoplexes were characterized for size, surface charge, in vitro cytotoxicity, and transfection ability in hADMSCs. A significant enhancement in BMP-2 protein secretion was observed on day 7 post-transfection of hADMSCs with PEI nanoplexes loaded with both pFGF-2 and pBMP-2 (PEI/(pFGF-2+pBMP-2)) versus transfection with PEI nanoplexes of either pFGF-2 alone or pBMP-2 alone. Osteogenic differentiation of transfected hADMSCs was determined by measuring osteocalcin and Runx-2 gene expression using real time polymerase chain reactions. A significant increase in the expression of Runx-2 and osteocalcin was observed on day 3 and day 7 post-transfection, respectively, by cells transfected with PEI/(pFGF-2+pBMP-2) compared to cells transfected with nanoplexes containing pFGF-2 or pBMP-2 alone. Alizarin Red staining and atomic absorption spectroscopy revealed elevated levels of calcium deposition in hADMSC cultures on day 14 and day 30 post-transfection with PEI/(pFGF-2+pBMP-2) compared to other treatments. We have shown that codelivery of pFGF-2 and pBMP-2 results in a significant enhancement in osteogenic protein synthesis, osteogenic marker expression, and subsequent mineralization. This research points to a new clinically translatable strategy for achieving efficient bone regeneration.

Overexpression of miR-100 inhibits growth of osteosarcoma through FGFR3

Osteosarcoma (OS) is a prevalent, fast growing cancer. Identification of molecular regulation of OS growth may result in development of a novel therapy. Previous studies have highlighted a role of microRNAs (miRNAs) in the regulation of the carcinogenesis of OS, whereas the underlying mechanisms are not completely understood. Moreover, a role of miR-100 in the growth control of OS is not clear. Here we reported significantly higher levels of fibroblast growth factor receptor 3 (FGFR3) and significantly lower levels of miR-100 in the OS specimen, compared to those in the paired normal bone tissues. Bioinformatics analysis and luciferase reporter assay suggest that miR-100 binds to the 3'UTR of FGFR3 mRNA to prevent its translation. To prove it, we modified miR-100 levels in OS cells. We found that overexpression of miR-100 in OS cells decreased FGFR3 protein levels, whereas inhibition of miR-100 increased FGFR3 protein levels, without affecting FGFR3 transcripts. Moreover, overexpression of miR-100 suppressed the OS growth in vitro and in vivo, while inhibition of miR-100 significantly increased OS growth. Taken together, our data demonstrate that miR-100 may inhibit the growth of OS through FGFR3.

Hyaluronan/RHAMM interactions in mesenchymal tumor pathogenesis: role of growth factors

Fibrosarcoma belongs to the sarcoma cancer group, which are spindle cell malignancies of mesenchymal origin, and owe their name to the predominant cell line that is present within the tumor. The extracellular matrix (ECM) is a complicated structure that surrounds and supports cells within tissues. Its main components are proteoglycans, collagens, glycoproteins, hyaluronan (HA), and several matrix-degrading enzymes. During cancer progression, significant changes can be observed in the structural and mechanical properties of ECM components. The ECM provides a physical scaffold to which tumor cells attach and migrate. Thus, it is required for key cellular events such as cell motility, adhesion, proliferation, invasion, and metastasis. Importantly, fibrosarcomas were shown to have a high content and turnover of ECM components including HA, proteoglycans, collagens, fibronectin, and laminin. In this review, we will focus on the HA component of fibrosarcoma ECM and critically discuss its role and involved mechanisms during fibrosarcoma pathogenesis.

Estrogen mediated epithelial proliferation in the uterus is directed by stromal Fgf10 and Bmp8a

To define endometrial stromal-derived paracrine mediators that participate in estradiol-17β (E2)-induced epithelial proliferation, microarray analysis of gene expression was carried out in mouse uterine epithelial-stromal co-culture systems under the condition of E2 or vehicle (control). Our results demonstrated gene alteration by E2: in epithelial cells, we found up-regulation of 119 genes and down-regulation of 28 genes, while in stroma cells we found up-regulation of 144 genes and down-regulation of 184 genes. A functional enrichment analysis of the upregulated epithelial genes implicated them for proliferation, while upregulated stromal genes were associated with extracellular functions. Quantitative RT-PCR and in situ hybridization results confirmed differential gene expression in both cell cultures and ovariectomized uteri after the above treatments. Based on our identification of stromal secretory factors, we found evidence that suppression by siRNA specifically for Bmp8a and/or Fgf10 in the stromal layer caused significant inhibition of proliferation by E2 in the co-culture system, suggesting Bmp8a and Fgf10 act as paracrine mediators during E2-dependent control of uterine proliferation. The localization of receptors and receptor activation signaling in epithelial cells in both the co-culture system and uteri was consistent with their involvement in ligand-receptor signaling. Interestingly, loss of Bmp8a or Fgf10 also caused abrogation of E2-regulated epithelial receptor signaling in co-culture systems, suggesting that stroma-derived Fgf10 and Bmp8a are responsible for epithelial communication. Overall, stromal Fgf10 and Bmp8a serve as potential paracrine factors for E2-dependent regulation of epithelial proliferation in the uterus.

Activation of FGF receptor signaling promotes invasion of non-small-cell lung cancer

The molecular regulation of metastasis of non-small-cell lung cancer (NSCLC) remains not completely defined. Here we showed significant higher MMP26 in the resected NSCLC than adjacent healthy tissue from the patients. Moreover, a strong correlation between MMP26 and the phosphorylated fibroblast growth factor receptor 1 (FGFR1) was detected. To examine the causal relationship between activated FGFR signaling and MMP26, we studied a human NSCLC cell line, A549. We found that FGF1-induced FGFR1 phosphorylation in A549 cells activated MMP26, resulting in an increase in cancer invasiveness. Inhibition of FGFR1 phosphorylation abolished FGF1-stimulated MMP26 activation, suggesting that activation of FGFR signaling pathway in NSCLC promotes cancer metastasis through MMP26. To define the signal transduction cascades downstream of FGFR1 activation for MMP26 activation, we used specific inhibitors for PI3K, ERK/MAPK, and JNK, respectively, to the FGF1-stimulated A549 cells. We found that only inhibition of JNK significantly decreased the activation of MMP26 in response to FGF1 stimulation, suggesting that activation of FGFR1 signaling may activate JNK to activate MMP26 in NSCLC. Our study thus highlights FGFR signaling pathway and MMP26 as novel therapeutic targets for NSCLC therapy.

mTORC1 and FGFR1 signaling in fibrolamellar hepatocellular carcinoma

Fibrolamellar hepatocellular carcinoma, or fibrolamellar carcinoma, is a rare form of primary liver cancer that afflicts healthy young men and women without underlying liver disease. There are currently no effective treatments for fibrolamellar carcinoma other than resection or transplantation. In this study, we sought evidence of mechanistic target of rapamycin complex 1 (mTORC1) activation in fibrolamellar carcinoma, based on anecdotal reports of tumor response to rapamycin analogs. Using a tissue microarray of 89 primary liver tumors, including a subset of 10 fibrolamellar carcinomas, we assessed the expression of phosphorylated S6 ribosomal protein (P-S6), a downstream target of mTORC1, along with fibroblast growth factor receptor 1 (FGFR1). These results were extended and confirmed using an additional 13 fibrolamellar carcinomas, whose medical records were reviewed. In contrast to weak staining in normal livers, all fibrolamellar carcinomas on the tissue microarray showed strong immunostaining for FGFR1 and P-S6, whereas only 13% of non-fibrolamellar hepatocellular carcinomas had concurrent activation of FGFR1 and mTORC1 signaling (P<0.05). When individual samples were stratified according to staining intensity (scale 0-4), the average score in fibrolamellar carcinomas was 2.46 for FGFR1 and 3.77 for P-S6, compared with 0 and 0, respectively, in non-tumor liver. Immunoblot analyses of fibrolamellar carcinomas revealed high mTORC1 activities relative to AKT activities accompanied by reduced TSC2 expression, which was not observed in non-fibrolamellar hepatocellular carcinomas. Our findings provide evidence for mTORC1 activation and FGFR1 overexpression in human fibrolamellar carcinoma, and support the use of FGFR1 inhibitors and rapamycin analogs in the treatment of patients with unresectable fibrolamellar carcinoma.

Versatility of Homogeneous Time-Resolved Fluorescence Resonance Energy Transfer Assays for Biologics Drug Discovery

Identification of potential lead antibodies in the drug discovery process requires the use of assays that not only measure binding of the antibody to the target molecule but assess a wide range of other characteristics. These include affinity ranking, measurement of their ability to inhibit relevant protein-protein interactions, assessment of their selectivity for the target protein, and determination of their species cross-reactivity profiles to support in vivo studies. Time-resolved fluorescence resonance energy transfer is a technology that offers the flexibility for development of such assays, through the availability of donor and acceptor fluorophore-conjugated reagents for detection of multiple tags or fusion proteins. The time-resolved component of the technology reduces potential assay interference, allowing screening of a range of different crude sample types derived from the bacterial or mammalian cell expression systems often used for antibody discovery projects. Here we describe the successful application of this technology across multiple projects targeting soluble proteins and demonstrate how it has provided key information for the isolation of potential therapeutic antibodies with the desired activity profile.

Inhibition of fibroblast growth factor receptor signaling impairs metastasis of hepatocellular carcinoma

The molecular mechanism underlying metastasis of hepatocellular carcinoma (HCC) remains elusive. Here, we showed that matrix metalloproteinase (MMP) 7 and MMP26 levels are significantly higher in the resected HCC than in the adjacent healthy hepatic cells from the patients. Moreover, a strong correlation of the levels of MMP7 or MMP26 with the phosphorylated fibroblast growth factor receptor 2 (FGFR2) was detected. To prove a causal link between the activation of FGFR signaling pathway and expression of MMP7 and MMP26, we used two human HCC lines, HepG2 and HuH-7, to study the underlying molecular basis. We found that FGF1-induced FGFR2 phosphorylation in either line resulted in significant activation of MMP7 and MMP26 and consequently an increase in cancer invasiveness. Inhibition of FGFR2 phosphorylation in HCC abolished FGF1-stimulated MMP7 and MMP26 expression, suggesting that activation of the FGFR signaling pathway in HCC may promote cancer metastasis by inducing MMP7 and MMP26 expression. To define the signal transduction cascades downstream of FGFR2 activation for MMP7 and MMP26 activation, we applied specific inhibitors for phosphatidylinositol-3 kinase (PI3K), extracellular signal-related kinase/mitogen-activated protein kinase (ERK/MAPK), and Jun N-terminal kinase (JNK), respectively, to the FGF1-stimulated HCC cells. We found that only inhibition of JNK significantly decreased the activation of MMP26 in response to FGF1 stimulation, and only inhibition of PI3K significantly decreased the activation of MMP7 in response to FGF1 stimulation, suggesting that the activation of the FGFR2 signaling may activate PI3K to activate MMP7 and activate JNK to activate MMP26, in HCC. Our study thus highlights the FGFR2 signaling pathway and MMP7 and MMP26 as novel therapeutic targets for HCC.

Regulation of metastasis of pediatric multiple myeloma by MMP13

The molecular mechanism underlying metastasis of pediatric multiple myeloma (MM) remains elusive. Here, we showed that the levels of MMP13 are significantly higher in MM from young patients than those from adult patients. Moreover, a strong correlation of the MMP13 and phosphorylated fibroblast growth factor receptor 4 (FGFR4) levels was detected in MM from young patients. To prove a causal link between activation of fibroblast growth factor receptors (FGFR) signaling pathway and MMP13 expression, we used a human MM line, RPMI-8226 (8226), to study the underlying molecular basis. We found that FGF1-induced FGFR4 phosphorylation in 8,226 cells resulted in significant activation of MMP13, and consequently, an increase in cancer invasiveness. FGFR4 inhibition in 8,226 cells abolished FGF1-stimulated MMP13 expression, suggesting that activation of FGFR signaling pathway in MM may promote cancer metastasis by inducing MMP13 expression. To define the signaling cascades downstream of FGFR4 activation for MMP13 activation, we applied specific inhibitors for PI3K, Jun N-terminal kinase (JNK), and ERK/MAPK, respectively, to the FGF1-stimulated 8,226 cells. We found that only inhibition of ERK1/2 significantly decreased the activation of MMP13 in response to FGF stimulation, suggesting that activation of FGFR signaling may activate ERK/MAPK, rather than JNK or PI3K pathway to activate MMP13 expression in 8,226 cells. Our study thus highlights FGFR4 signaling pathway and MMP13 as novel therapeutic targets for MM.

Fibroblast growth factor-based signaling through synthetic heparan sulfate blocks copolymers studied using high cell density three-dimensional cell printing

Four well-defined heparan sulfate (HS) block copolymers containing S-domains (high sulfo group content) placed adjacent to N-domains (low sulfo group content) were chemoenzymatically synthesized and characterized. The domain lengths in these HS block co-polymers were ~40 saccharide units. Microtiter 96-well and three-dimensional cell-based microarray assays utilizing murine immortalized bone marrow (BaF3) cells were developed to evaluate the activity of these HS block co-polymers. Each recombinant BaF3 cell line expresses only a single type of fibroblast growth factor receptor (FGFR) but produces neither HS nor fibroblast growth factors (FGFs). In the presence of different FGFs, BaF3 cell proliferation showed clear differences for the four HS block co-polymers examined. These data were used to examine the two proposed signaling models, the symmetric FGF2-HS2-FGFR2 ternary complex model and the asymmetric FGF2-HS1-FGFR2 ternary complex model. In the symmetric FGF2-HS2-FGFR2 model, two acidic HS chains bind in a basic canyon located on the top face of the FGF2-FGFR2 protein complex. In this model the S-domains at the non-reducing ends of the two HS proteoglycan chains are proposed to interact with the FGF2-FGFR2 protein complex. In contrast, in the asymmetric FGF2-HS1-FGFR2 model, a single HS chain interacts with the FGF2-FGFR2 protein complex through a single S-domain that can be located at any position within an HS chain. Our data comparing a series of synthetically prepared HS block copolymers support a preference for the symmetric FGF2-HS2-FGFR2 ternary complex model.

Targeting tumor micro-environment for design and development of novel anti-angiogenic agents arresting tumor growth

Angiogenesis: a process of generation of new blood vessels has been proved to be necessary for sustained tumor growth and cancer progression. Inhibiting angiogenesis pathway has long been remained a significant hope for the development of novel, effective and target orientated antitumor agents arresting the tumor proliferation and metastasis. The process of neoangiogenesis as a biological process is regulated by several pro- and anti-angiogenic factors, especially vascular endothelial growth factor, fibroblast growth factor, epidermal growth factor, hypoxia inducible factor 1 and transforming growth factor. Every endothelial cell destined for vessel formation is equipped with receptors for these angiogenic peptides. Moreover, numerous other angiogenic cytokines such as platelet derived growth factor (PGDF), placenta growth factor (PGF), nerve growth factor (NGF), stem-cell factor (SCF), and interleukins-2, 4, 6 etc. These molecular players performs critical role in regulating the angiogenic switch. Couple of decade's research in molecular aspects of tumor biology has unraveled numerous structural and functional mysteries of these angiogenic peptides. In present article, a detailed update on the functional and structural peculiarities of the various angiogenic peptides is described focusing on structural opportunities made available that has potential to be used to modulate function of these angiogenic peptides in developing therapeutic agents targeting neoplastic angiogenesis. The data may be useful in the mainstream of developing novel anticancer agents targeting tumor angiogenesis. We also discuss major therapeutic agents that are currently used in angiogenesis associated therapies as well as those are subject of active research or are in clinical trials.

Fibroblast growth factor-2 signaling in neurogenesis and neurodegeneration

Fibroblast growth factor-2 (FGF2), also known as basic FGF, is a multi-functional growth factor. One of the 22-member FGF family, it signals through receptor tyrosine kinases encoding FGFR1-4. FGF2 activates FGFRs in cooperation with heparin or heparin sulfate proteoglycan to induce its pleiotropic effects in different tissues and organs, which include potent angiogenic effects and important roles in the differentiation and function of the central nervous system (CNS). FGF2 is crucial to development of the CNS, which explains its importance in adult neurogenesis. During development, high levels of FGF2 are detected from neurulation onwards. Moreover, developmental expression of FGF2 and its receptors is temporally and spatially regulated, concurring with development of specific brain regions including the hippocampus and substantia nigra pars compacta. In adult neurogenesis, FGF2 has been implicated based on its expression and regulation of neural stem and progenitor cells in the neurogenic niches, the subventricular zone (SVZ) and the subgranular zone (SGZ) of the hippocampal dentate gyrus. FGFR1 signaling also modulates inflammatory signaling through the surface glycoprotein CD200, which regulates microglial activation. Because of its importance in adult neurogenesis and neuroinflammation, manipulation of FGF2/FGFR1 signaling has been a focus of therapeutic development for neurodegenerative disorders, such as Alzheimer's disease, multiple sclerosis, Parkinson's disease and traumatic brain injury. Novel strategies include intranasal administration of FGF2, administration of an NCAM-derived FGFR1 agonist, and chitosan-based nanoparticles for the delivery of FGF2 in pre-clinical animal models. In this review, we highlight current research towards therapeutic interventions targeting FGF2/FGFR1 in neurodegenerative disorders.

Stat3-targeted therapies overcome the acquired resistance to vemurafenib in melanomas

Vemurafenib (PLX4032), a selective inhibitor of Braf, has been approved by the US Food and Drug Administration for the treatment of unresectable or metastatic melanoma in patients with Braf(V600E) mutations. Many patients treated with vemurafenib initially display dramatic improvement, with decreases in both risk of death and tumor progression. Acquired resistance, however, rapidly arises in previously sensitive cells. We attempted to overcome this resistance by targeting the signal transducer and activator of transcription 3 (STAT3)-paired box homeotic gene 3 (PAX3)-signaling pathway, which is upregulated, owing to fibroblast growth factor 2 (FGF2) secretion or increased kinase activity, with the Braf(V600E) mutation. We found that activation of Stat3 or overexpression of PAX3 induced resistance to vemurafenib in melanoma cells. In addition, PAX3 or Stat3 silencing inhibited the growth of melanoma cells with acquired resistance to vemurafenib. Furthermore, treatment with the Stat3 inhibitor, WP1066, resulted in growth inhibition in both vemurafenib-sensitive and -resistant melanoma cells. Significantly, vemurafenib stimulation induced FGF2 secretion from keratinocytes and fibroblasts, which might uncover, at least in part, the mechanisms underlying targeting Stat3-PAX3 signaling to overcome the acquired resistance to vemurafenib. Our results suggest that Stat3-targeted therapy is a new therapeutic strategy to overcome the acquired resistance to vemurafenib in the treatment of melanoma.

Fibroblast growth factor receptors, developmental corruption and malignant disease

Fibroblast growth factors (FGF) are a family of ligands that bind to four different types of cell surface receptor entitled, FGFR1, FGFR2, FGFR3 and FGFR4. These receptors differ in their ligand binding affinity and tissue distribution. The prototypical receptor structure is that of an extracellular region comprising three immunoglobulin (Ig)-like domains, a hydrophobic transmembrane segment and a split intracellular tyrosine kinase domain. Alternative gene splicing affecting the extracellular third Ig loop also creates different receptor isoforms entitled FGFRIIIb and FGFRIIIc. Somatic fibroblast growth factor receptor (FGFR) mutations are implicated in different types of cancer and germline FGFR mutations occur in developmental syndromes particularly those in which craniosynostosis is a feature. The mutations found in both conditions are often identical. Many somatic FGFR mutations in cancer are gain-of-function mutations of established preclinical oncogenic potential. Gene amplification can also occur with 19-22% of squamous cell lung cancers for example having amplification of FGFR1. Ontologic comparators can be informative such as aberrant spermatogenesis being implicated in both spermatocytic seminomas and Apert syndrome. The former arises from somatic FGFR3 mutations and Apert syndrome arises from germline FGFR2 mutations. Finally, therapeutics directed at inhibiting the FGF/FGFR interaction are a promising subject for clinical trials.

Species-specific biological effects of FGF-2 in articular cartilage: implication for distinct roles within the FGF receptor family

Existing literature demonstrates that fibroblast growth factor-2 (FGF-2) exerts opposing, contradictory biological effects on cartilage homeostasis in different species. In human articular cartilage, FGF-2 plays a catabolic and anti-anabolic role in cartilage homeostasis, driving homeostasis toward degeneration and osteoarthritis (OA). In murine joints, however, FGF-2 has been identified as an anabolic mediator as ablation of the FGF-2 gene demonstrated increased susceptibility to OA. There have been no previous studies specifically addressing species-specific differences in FGF-2-mediated biological effects. In this study, we provide a mechanistic understanding by which FGF-2 exerts contradictory biological effects in human versus murine tissues. Using human articular cartilage (ex vivo) and a medial meniscal destabilization (DMM) animal model (in vivo), species-specific expression patterns of FGFR receptors (FGFRs) are elucidated between human and murine articular cartilage. In the murine OA model followed by intra-articular injection of FGF-2, we further correlate FGFR profiles to changes in behavioral pain perception, proteoglycan content in articular cartilage, and production of inflammatory (CD11b) and angiogenic (VEGF) mediators in synovium lining cells. Our results suggest that the fundamental differences in cellular responses between human and murine tissues may be secondary to distinctive expression patterns of FGFRs that eventually determine biological outcomes in the presence of FGF-2. The complex interplay of FGFRs and the downstream signaling cascades induced by FGF-2 in human cartilage should add caution to the use of this particular growth factor for biological therapy in the future.

WITHDRAWN: Interaction of FGF1 with a novel anti-angiogenic drug SSR128129E

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Characterization of FGF receptor expression in human neutrophils and their contribution to chemotaxis

Several members of the fibroblast growth factor (FGF) family are potent endothelial cell (EC) mitogens and angiogenic factors, and their activities can be mediated by four tyrosine kinase receptors (FGFR1–4). In addition, FGFs can induce the release of inflammatory mediators by ECs and the expression of adhesion molecules at their surface, thereby favoring the recruitment and transvascular migration of inflammatory cells such as neutrophils. Neither the expression nor the biological activities that could be mediated by FGFRs have been investigated in human neutrophils. By biochemical and cytological analyses, we observed that purified circulating human neutrophils from healthy individuals expressed varying levels of FGFRs in their cytosol and at their cytoplasmic membrane. FGFR-2 was identified as the sole cell surface receptor, with FGFR-1 and -4 localizing in the cytosol and FGFR-3 being undetectable. We assessed the capacity of FGF-1 and FGF-2 to induce neutrophil chemotaxis in a modified Boyden microchamber and observed that they increase neutrophil transmigration at 10−10 and 10−9 M and by 1.77- and 2.34-fold, respectively, as compared with PBS-treated cells. Treatment with a selective anti-FGFR-2 antibody reduced FGF-1-mediated chemotaxis by 75% and abrogated the effect of FGF-2, while the blockade of FGFR-1 and -4 partially inhibited (15–40%) FGF-chemotactic activities. In summary, our data are the first to report the expression of FGF receptors in human neutrophils, with FGF-1 and FGF-2 promoting neutrophil chemotaxis mainly through FGFR-2 activation.

FGF23 induces left ventricular hypertrophy

Chronic kidney disease (CKD) is a public health epidemic that increases risk of death due to cardiovascular disease. Left ventricular hypertrophy (LVH) is an important mechanism of cardiovascular disease in individuals with CKD. Elevated levels of FGF23 have been linked to greater risks of LVH and mortality in patients with CKD, but whether these risks represent causal effects of FGF23 is unknown. Here, we report that elevated FGF23 levels are independently associated with LVH in a large, racially diverse CKD cohort. FGF23 caused pathological hypertrophy of isolated rat cardiomyocytes via FGF receptor-dependent activation of the calcineurin-NFAT signaling pathway, but this effect was independent of klotho, the coreceptor for FGF23 in the kidney and parathyroid glands. Intramyocardial or intravenous injection of FGF23 in wild-type mice resulted in LVH, and klotho-deficient mice demonstrated elevated FGF23 levels and LVH. In an established animal model of CKD, treatment with an FGF-receptor blocker attenuated LVH, although no change in blood pressure was observed. These results unveil a klotho-independent, causal role for FGF23 in the pathogenesis of LVH and suggest that chronically elevated FGF23 levels contribute directly to high rates of LVH and mortality in individuals with CKD.

Regulation of serum 1,25(OH)2 vitamin D3 levels by fibroblast growth factor 23 is mediated by FGF receptors 3 and 4

Fibroblast growth factor 23 (FGF23) is a phosphaturic hormone implicated in the pathogenesis of several hypophosphatemic disorders. FGF23 causes hypophosphatemia by decreasing the expression of sodium phosphate cotransporters (NaPi-2a and NaPi-2c) and decreasing serum 1,25(OH)(2)Vitamin D(3) levels. We previously showed that FGFR1 is the predominant receptor for the hypophosphatemic actions of FGF23 by decreasing renal NaPi-2a and 2c expression while the receptors regulating 1,25(OH)(2)Vitamin D(3) levels remained elusive. To determine the FGFRs regulating 1,25(OH)(2)Vitamin D(3) levels, we studied FGFR3(-/-)FGFR4(-/-) mice as these mice have shortened life span and are growth retarded similar to FGF23(-/-) and Klotho(-/-) mice. Baseline serum 1,25(OH)(2)Vitamin D(3) levels were elevated in the FGFR3(-/-)FGFR4(-/-) mice compared with wild-type mice (102.2 ± 14.8 vs. 266.0 ± 34.0 pmol/l; P = 0.001) as were the serum levels of FGF23. Administration of recombinant FGF23 had no effect on serum 1,25(OH)(2)Vitamin D(3) in the FGFR3(-/-)FGFR4(-/-) mice (173.4 ± 32.7 vs. 219.7 ± 56.5 pmol/l; vehicle vs. FGF23) while it reduced serum 1,25(OH)(2)Vitamin D(3) levels in wild-type mice. Administration of FGF23 to FGFR3(-/-)FGFR4(-/-) mice resulted in a decrease in serum parathyroid hormone (PTH) levels and an increase in serum phosphorus levels mediated by increased renal phosphate reabsorption. These data indicate that FGFR3 and 4 are the receptors that regulate serum 1,25(OH)(2)Vitamin D(3) levels in response to FGF23. In addition, when 1,25(OH)(2)Vitamin D(3) levels are not affected by FGF23, as in FGFR3(-/-)FGFR4(-/-) mice, a reduction in PTH can override the effects of FGF23 on renal phosphate transport.

Highly sulfated nonreducing end-derived heparan sulfate domains bind fibroblast growth factor-2 with high affinity and are enriched in biologically active fractions

Human fibroblast growth factor-2 (FGF2) regulates cellular processes including proliferation, adhesion, motility, and angiogenesis. FGF2 exerts its biological function by binding and dimerizing its receptor (FGFR), which activates signal transduction cascades. Effective binding of FGF2 to its receptor requires the presence of heparan sulfate (HS), a linear polysaccharide with N-sulfated domains (NS) localized at the cell surface and extracellular matrix. HS acts as a platform facilitating the formation of a functional FGF-FGFR-HS ternary complex. Crystal structures of the signaling ternary complex revealed two conflicting architectures. In the asymmetrical model, two FGFs and two FGFRs bind a single HS chain. In contrast, the symmetrical model postulates that one FGF and one FGFR bind to the free end of the HS chain and dimerization require these ends to join, bringing the two half-complexes together. In this study, we screened a hexasaccharide HS library for compositions that are able to bind FGF2. The library was composed primarily of NS domains internal to the HS chain with minor presence of non-reducing end (NRE) NS. The binders were categorized into low versus high affinity binders. The low affinity fraction contained primarily hexasaccharides with low degree of sulfation that were internal to the HS chains. In contrast, the high affinity bound fraction was enriched in NRE oligosaccharides that were considerably more sulfated and had the ability to promote FGFR-mediated cell proliferation. The results suggest a role of the NRE of HS in FGF2 signaling and favor the formation of the symmetrical architecture on short NS domains.

Aryl Extensions of Thienopyrimidinones as Fibroblast Growth Factor Receptor 1 Kinase Inhibitors

Optimization of thienopyrimidinone derivatives as FGFR1 kinase inhibitors is being pursued. The present results confirm predictions of computational modeling that an aryl subtituent can be introduced at the 2-position in strucure 3. The substituent is anticipated to project deeper into the binding site and provide opportunities for enhanced activity and selectivity. The most potent analog reported here, 13, has a 4-hydroxyphenyl substituent and yields an IC(50) of 6 μM for inhibition of phosphorylation by FGFR1 kinase. It was also found that the western anisole-containing substituent in 3 can be replaced by a propionic acid group with no loss in potency and with potentially significant gains in pharmacologically relevant properties.

Growth factor mediated signaling in pancreatic pathogenesis

Functionally, the pancreas consists of two types of tissues: exocrine and endocrine. Exocrine pancreatic disorders mainly involve acute and chronic pancreatitis. Acute pancreatitis typically is benign, while chronic pancreatitis is considered a risk factor for developing pancreatic cancer. Pancreatic carcinoma is the fourth leading cause of cancer related deaths worldwide. Most pancreatic cancers develop in the exocrine tissues. Endocrine pancreatic tumors are more uncommon, and typically are less aggressive than exocrine tumors. However, the endocrine pancreatic disorder, diabetes, is a dominant cause of morbidity and mortality. Importantly, different growth factors and their receptors play critical roles in pancreatic pathogenesis. Hence, an improved understanding of how various growth factors affect pancreatitis and pancreatic carcinoma is necessary to determine appropriate treatment. This chapter describes the role of different growth factors such as vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF), platelet derived growth factor (PDGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), and transforming growth factor (TGF) in various pancreatic pathophysiologies. Finally, the crosstalk between different growth factor axes and their respective signaling mechanisms, which are involved in pancreatitis and pancreatic carcinoma, are also discussed.

Immobilization and bioactivity evaluation of FGF-1 and FGF-2 on powdered silicon-doped hydroxyapatite and their scaffolds for bone tissue engineering

Fibroblast growth factors (FGFs) are polypeptides that control the proliferation and differentiation of various cell types including osteoblasts. FGFs are also strong inducers of angiogenesis, necessary to obtain oxygen and nutrients during tissue repair. With the aim to incorporate these desirable FGF biological properties into bioceramics for bone repair, silicon substituted hydroxyapatites (Si-HA) were used as materials to immobilize bioactive FGF-1 and FGF-2. Thus, the binding of these growth factors to powdered Si-HA and Si-HA scaffolds was carried out efficiently in the present study and both FGFs maintained its biological activity on osteoblasts after its immobilization. The improvement of cell adhesion and proliferation onto Si-HA scaffolds suggests the potential utility of these FGF/scaffolds for bone tissue engineering.

Molecular level interaction of the human acidic fibroblast growth factor with the antiangiogenic agent, inositol hexaphosphate

Acidic fibroblast growth factor (FGF1) regulates a wide array of important biological phenomena such as angiogenesis, cell differentiation, tumor growth, and neurogenesis. Generally, FGFs are known for their strong affinity for the glycosaminoglycan heparin, as a prerequisite for recognition of a specific tyrosine kinase on the cell surface and are responsible for the cell signal transduction cascade. Inositol hexaphosphate (IP6) is a natural antioxidant and is known for its antiangiogenic role, in addition to its ability to control tumor growth. In the present study, we investigated the interaction of IP6 with the acidic fibroblast growth factor (FGF1) using various biophysical techniques including isothermal calorimetry, circular dichroism, and multidimensional NMR spectroscopy. Herein, we have reported the three-dimensional solution structure of the FGF1-IP6 complex. These data show that IP6 binds FGF1 and enhances its thermal stability. In addition, we also demonstrate that IP6 acts as an antagonist to acidic fibroblast growth factor by inhibiting its receptor binding and subsequently decreasing the mitogenic activity. The inhibition likely results in the ability of IP6 to antagonize the angiogenic and mitogenic activity of FGF1.