FGFR a promising druggable target in cancer: Molecular biology and new drugs

INTRODUCTION

The Fibroblast Growth Factor Receptor (FGFR) family consists of Tyrosine Kinase Receptors (TKR) involved in several biological functions. Recently, alterations of FGFR have been reported to be important for progression and development of several cancers. In this setting, different studies are trying to evaluate the efficacy of different therapies targeting FGFR.

AREAS COVERED

This review summarizes the current status of treatments targeting FGFR, focusing on the trials that are evaluating the FGFR profile as inclusion criteria: Multi-Target, Pan-FGFR Inhibitors and anti-FGF (Fibroblast Growth Factor)/FGFR Monoclonal Antibodies.

EXPERT OPINION

Most of the TKR share intracellular signaling pathways; therefore, cancer cells tend to overcome the inhibition of one tyrosine kinase receptor by activating another. The future of TKI (Tyrosine Kinase Inhibitor) therapy will potentially come from multi-targeted TKIs that target different TKR simultaneously. It is crucial to understand the interaction of the FGF-FGFR axis with other known driver TKRs. Based on this, it is possible to develop therapeutic strategies targeting multiple connected TKRs at once. One correct step in this direction is the reassessment of multi target inhibitors considering the FGFR status of the tumor. Another opportunity arises from assessing the use of FGFR TKI on patients harboring FGFR alterations.

Calreticulin is a secreted BMP antagonist, expressed in Hensen's node during neural induction

Hensen's node is the "organizer" of the avian and mammalian early embryo. It has many functions, including neural induction and patterning of the ectoderm and mesoderm. Some of the signals responsible for these activities are known but these do not explain the full complexity of organizer activity. Here we undertake a functional screen to discover new secreted factors expressed by the node at this time of development. Using a Signal Sequence Trap in yeast, we identify several candidates. Here we focus on Calreticulin. We show that in addition to its known functions in intracellular Calcium regulation and protein folding, Calreticulin is secreted, it can bind to BMP4 and act as a BMP antagonist in vivo and in vitro. Calreticulin is not sufficient to account for all organizer functions but may contribute to the complexity of its activity.

A computationally identified compound antagonizes excess FGF-23 signaling in renal tubules and a mouse model of hypophosphatemia

Fibroblast growth factor-23 (FGF-23) interacts with a binary receptor complex composed of α-Klotho (α-KL) and FGF receptors (FGFRs) to regulate phosphate and vitamin D metabolism in the kidney. Excess FGF-23 production, which causes hypophosphatemia, is genetically inherited or occurs with chronic kidney disease. Among other symptoms, hypophosphatemia causes vitamin D deficiency and the bone-softening disorder rickets. Current therapeutics that target the receptor complex have limited utility clinically. Using a computationally driven, structure-based, ensemble docking and virtual high-throughput screening approach, we identified four novel compounds predicted to selectively inhibit FGF-23-induced activation of the FGFR/α-KL complex. Additional modeling and functional analysis found that Zinc13407541 bound to FGF-23 and disrupted its interaction with the FGFR1/α-KL complex; experiments in a heterologous cell expression system showed that Zinc13407541 selectivity inhibited α-KL-dependent FGF-23 signaling. Zinc13407541 also inhibited FGF-23 signaling in isolated renal tubules ex vivo and partially reversed the hypophosphatemic effects of excess FGF-23 in a mouse model. These chemical probes provide a platform to develop lead compounds to treat disorders caused by excess FGF-23.

Fibroblast Growth Factor 21 Mediates Glycemic Regulation by Hepatic JNK

The cJun NH2-terminal kinase (JNK)-signaling pathway is implicated in metabolic syndrome, including dysregulated blood glucose concentration and insulin resistance. Fibroblast growth factor 21 (FGF21) is a target of the hepatic JNK-signaling pathway and may contribute to the regulation of glycemia. To test the role of FGF21, we established mice with selective ablation of the Fgf21 gene in hepatocytes. FGF21 deficiency in the liver caused marked loss of FGF21 protein circulating in the blood. Moreover, the protective effects of hepatic JNK deficiency to suppress metabolic syndrome in high-fat diet-fed mice were not observed in mice with hepatocyte-specific FGF21 deficiency, including reduced blood glucose concentration and reduced intolerance to glucose and insulin. Furthermore, we show that JNK contributes to the regulation of hepatic FGF21 expression during fasting/feeding cycles. These data demonstrate that the hepatokine FGF21 is a key mediator of JNK-regulated metabolic syndrome.

Effect of Metformin on Fibroblast Growth Factor-21 Levels in Patients with Newly Diagnosed Type 2 Diabetes

BACKGROUND

Fibroblast growth factor (FGF)-21 is an important regulator of glucose metabolism. In the present study, we investigated whether plasma levels of FGF-21 changed in patients with newly diagnosed type 2 diabetes mellitus (T2DM) and assessed the effects of metformin treatment on plasma FGF-21 levels.

MATERIALS AND METHODS

The plasma FGF-21 levels and the metabolic parameters of 226 patients with newly diagnosed T2DM and 100 sex- and age-matched normal glycemic tolerant (NGT) controls were measured. Seventy-four patients among of the 226 patients with T2DM were treated with metformin throughout the 12-week study period. The fasting plasma FGF-21 and high-sensitivity C-reactive protein (hs-CRP) levels were measured using enzyme-linked immunosorbent assay kits.

RESULTS

The patients with T2DM had significantly higher fasting plasma FGF-21 levels (302.2 pg/mL [range, 201.3-454.4 pg/mL] vs. 104.5 pg/mL [range, 71.6-185.6 pg/mL]; P < 0.00) and hs-CRP levels (2.63 ± 2.81 mg/L vs. 1.58 ± 2.16 mg/L; P < 0.00) than the NGT subjects. The fasting plasma hs-CRP and FGF-21 levels were significantly decreased in the T2DM group after metformin treatment compared with pretreatment (respectively, 2.56 ± 1.75 mg/L vs. 3.28 ± 1.89 mg/L [P < 0.05] and 232.6 pg/mL [range, 154.3-307.8 pg/mL] vs. 313.9 pg/mL [range, 227.7-474.2 pg/mL] [P < 0.01]).

CONCLUSIONS

In patients with T2DM, the plasma FGF-21 levels are increased but are significantly decreased after metformin treatment. Metformin may play a role in reducing the FGF-21 levels in patients with T2DM, likely through the amelioration of glucose-lipid metabolism and inflammation.

[Inhitibion of FGF23 activities as a possible new treatment for patients with FGF23-related hypophosphatemic diseases]

Excessive actions of fibroblast growth factor 23(FGF23)result in several kinds of hypophosphatemic rickets and osteomalacia. A combination of oral active vitamin D3 and phosphate is the current standard therapy for FGF23-related hypophosphatemia. However, these medications can lead to long-term complications, such as secondary hyperparathyroidism and renal impairment. Therefore, safer and more efficient therapy to correct excessive actions of FGF23 is needed. X-linked hypophosphatemic rickets(XLHR)is the most prevalent form of FGF23-related hypophosphatemia. The efficacy of anti-FGF23 antibody was confirmed in a Hyp mouse, a murine model of XLHR. A recent phase 1 double-blind, placebo-controlled study and the subsequent open-label phase 1/2 study in adults with XLHR showed the safety and the efficacy of human anti-FGF23 antibody, KRN23. KRN23 has a potential for effectively treating patients with XLHR and other types of FGF23-related hypophosphatemia as well.

Counter-regulatory paracrine actions of FGF-23 and 1,25(OH)2 D in macrophages

Mechanisms underlying the association between fibroblastic growth factor 23 (FGF-23) and inflammation are uncertain. We found that FGF-23 was markedly up-regulated in LPS/INF-γ-induced proinflammatory M1 macrophages and Hyp mouse-derived peritoneal macrophages, but not in IL-4-induced M2 anti-inflammatory macrophages. NF-КB and JAK/STAT1 pathways mediated the increased transcription of FGF-23 in response to M1 polarization. FGF-23 stimulated TNF-α, but not IL-6, expression in M0 macrophages and suppressed Arginase-1 expression in M2 macrophages through FGFR-mediated mechanisms. 1,25(OH)2 D stimulated Arginase-1 expression and inhibited FGF-23 stimulation of TNF-α. FGF-23 has proinflammatory paracrine functions and counter-regulatory actions to 1,25(OH)2 D on innate immune responses.

[Medical treatment of children with hypophosphataemic rickets]

Hypophosphataemic rickets is a rare, genetic disorder resulting in defect bone mineralisation and rickets. The current medical treatment consists of phosphate supplementation and alfacalcidol, but side effects such as secondary hyperparat-hyroidism and nephrocalcinosis are common. This treatment regimen often fails to prevent bone deformity and reduced final height. The rarity and complexity of these diseases call for centralised specialist care and international collaboration. Future medical treatment may be improved by addition of new promising experimental treatments.

Randomized trial of the anti-FGF23 antibody KRN23 in X-linked hypophosphatemia

BACKGROUND

X-linked hypophosphatemia (XLH) is the most common heritable form of rickets and osteomalacia. XLH-associated mutations in phosphate-regulating endopeptidase (PHEX) result in elevated serum FGF23, decreased renal phosphate reabsorption, and low serum concentrations of phosphate (inorganic phosphorus, Pi) and 1,25-dihydroxyvitamin D [1,25(OH)2D]. KRN23 is a human anti-FGF23 antibody developed as a potential treatment for XLH. Here, we have assessed the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and immunogenicity of KRN23 following a single i.v. or s.c. dose of KRN23 in adults with XLH.

METHODS

Thirty-eight XLH patients were randomized to receive a single dose of KRN23 (0.003-0.3 mg/kg i.v. or 0.1-1 mg/kg s.c.) or placebo. PK, PD, immunogenicity, safety, and tolerability were assessed for up to 50 days.

RESULTS

KRN23 significantly increased the maximum renal tubular threshold for phosphate reabsorption (TmP/GFR), serum Pi, and 1,25(OH)2D compared with that of placebo (P<0.01). The maximum serum Pi concentration occurred later following s.c. dosing (8-15 days) compared with that seen with i.v. dosing (0.5-4 days). The effect duration was dose related and persisted longer in patients who received s.c. administration. Changes from baseline in TmP/GFR, serum Pi, and serum 1,25(OH)2D correlated with serum KRN23 concentrations. The mean t1/2 of KRN23 was 8-12 days after i.v. administration and 13-19 days after s.c. administration. Patients did not exhibit increased nephrocalcinosis or develop hypercalciuria, hypercalcemia, anti-KRN23 antibodies, or elevated serum parathyroid hormone (PTH) or creatinine.

CONCLUSION

KRN23 increased TmP/GFR, serum Pi, and serum 1,25(OH)2D. The positive effect of KR23 on serum Pi and its favorable safety profile suggest utility for KRN23 in XLH patients. Trial registration. Clinicaltrials.gov NCT00830674. Funding. Kyowa Hakko Kirin Pharma, Inc.

High glucose represses β-klotho expression and impairs fibroblast growth factor 21 action in mouse pancreatic islets: involvement of peroxisome proliferator-activated receptor γ signaling

Circulating fibroblast growth factor 21 (FGF21) levels are elevated in diabetic subjects and correlate directly with abnormal glucose metabolism, while pharmacologically administered FGF21 can ameliorate hyperglycemia. The pancreatic islet is an FGF21 target, yet the actions of FGF21 in the islet under normal and diabetic conditions are not fully understood. This study investigated the effects of high glucose on islet FGF21 actions in a diabetic mouse model by investigating db/db mouse islet responses to exogenous FGF21, the direct effects of glucose on FGF21 signaling, and the involvement of peroxisome proliferator-activated receptor γ (PPARγ) in FGF21 pathway activation. Results showed that both adult db/db mouse islets and normal islets treated with high glucose ex vivo displayed reduced β-klotho expression, resistance to FGF21, and decreased PPARγ expression. Rosiglitazone, an antidiabetic PPARγ ligand, ameliorated these effects. Our data indicate that hyperglycemia in type 2 diabetes mellitus may lead to FGF21 resistance in pancreatic islets, probably through reduction of PPARγ expression, which provides a novel mechanism for glucose-mediated islet dysfunction.

Inhibition of tumor angiogenesis and growth by a small-molecule multi-FGF receptor blocker with allosteric properties

Receptor tyrosine kinases (RTK) are targets for anticancer drug development. To date, only RTK inhibitors that block orthosteric binding of ligands and substrates have been developed. Here, we report the pharmacologic characterization of the chemical SSR128129E (SSR), which inhibits fibroblast growth factor receptor (FGFR) signaling by binding to the extracellular FGFR domain without affecting orthosteric FGF binding. SSR exhibits allosteric properties, including probe dependence, signaling bias, and ceiling effects. Inhibition by SSR is highly conserved throughout the animal kingdom. Oral delivery of SSR inhibits arthritis and tumors that are relatively refractory to anti-vascular endothelial growth factor receptor-2 antibodies. Thus, orally-active extracellularly acting small-molecule modulators of RTKs with allosteric properties can be developed and may offer opportunities to improve anticancer treatment.

Targeted anti-vascular therapies for ovarian cancer: current evidence

Ovarian cancer presents at advanced stage in around 75% of women, and despite improvements in treatments such as chemotherapy, the 5-year survival from the disease in women diagnosed between 1996 and 1999 in England and Wales was only 36%. Over 80% of patients with advanced ovarian cancer will relapse and despite a good chance of remission from further chemotherapy, they will usually die from their disease. Sequential treatment strategies are employed to maximise quality and length of life but patients eventually become resistant to cytotoxic agents. The expansion in understanding of the molecular biology that characterises cancer cells has led to the rapid development of new agents to target important pathways but the heterogeneity of ovarian cancer biology means that there is no predominant defect. This review attempts to discuss progress to date in tackling a more general target applicable to ovary cancer-angiogenesis.

Antagonizing retinoic acid and FGF/MAPK pathways control posterior body patterning in the invertebrate chordate Ciona intestinalis

Vertebrate embryos exploit the mutual inhibition between the RA and FGF signalling pathways to coordinate the proliferative elongation of the main body axis with the progressive patterning and differentiation of its neuroectodermal and paraxial mesodermal structures. The evolutionary history of this patterning system is still poorly understood. Here, we investigate the role played by the RA and FGF/MAPK signals during the development of the tail structures in the tunicate Ciona intestinalis, an invertebrate chordate belonging to the sister clade of vertebrates, in which the prototypical chordate body plan is established through very derived morphogenetic processes. Ciona embryos are constituted of few cells and develop according to a fixed lineage; elongation of the tail occurs largely by rearrangement of postmitotic cells; mesoderm segmentation and somitogenesis are absent. We show that in the Ciona embryo, the antagonism of the RA and FGF/MAPK signals is required to control the anteroposterior patterning of the tail epidermis. We also demonstrate that the RA, FGF/MAPK and canonical Wnt pathways control the anteroposterior patterning of the tail peripheral nervous system, and reveal the existence of distinct subpopulations of caudal epidermal neurons with different responsiveness to the RA, FGF/MAPK and canonical Wnt signals. Our data provide the first demonstration that the use of the antagonism between the RA and FGF signals to pattern the main body axis predates the emergence of vertebrates and highlight the evolutionary plasticity of this patterning strategy, showing that in different chordates it can be used to pattern different tissues within the same homologous body region.

Fibroblast growth factor 23: friend or foe in uremia?

Uremia is a complex metabolic state marked by derangement of many signaling molecules and metabolic intermediates; of these, the massively increased levels of FGF23 are among the most striking. It has remained unclear whether FGF23 is directly implicated in the pathogenesis of chronic kidney disease (CKD) and its complications, a consequence of other dysregulated pathways, or perhaps an adaptive - and thus desirable - response. In this issue of the JCI, Shalhoub et al. describe the chronic effects of antibody-mediated FGF23 neutralization in a CKD mouse model, shedding new light on this complicated story and moving us one step closer to understanding the role of FGF23 in CKD.

Chronic inhibition of ERK1/2 signaling improves disordered bone and mineral metabolism in hypophosphatemic (Hyp) mice

The X-linked hypophosphatemic (Hyp) mouse carries a loss-of-function mutation in the phex gene and is characterized by hypophosphatemia due to renal phosphate (Pi) wasting, inappropriately suppressed 1,25-dihydroxyvitamin D [1,25(OH)₂D] production, and rachitic bone disease. Increased serum fibroblast growth factor-23 concentration is responsible for the disordered metabolism of Pi and 1,25(OH)₂D. In the present study, we tested the hypothesis that chronic inhibition of fibroblast growth factor-23-induced activation of MAPK signaling in Hyp mice can reverse their metabolic derangements and rachitic bone disease. Hyp mice were administered the MAPK inhibitor, PD0325901 orally for 4 wk. PD0325901 induced a 15-fold and 2-fold increase in renal 1α-hydroxylase mRNA and protein abundance, respectively, and thereby higher serum 1,25(OH)₂D concentrations (115 ± 13 vs. 70 ± 16 pg/ml, P < 0.05), compared with values in vehicle-treated Hyp mice. With PD0325901, serum Pi levels were higher (5.1 ± 0.5 vs. 3 ± 0.2 mg/dl, P < 0.05), and the protein abundance of sodium-dependent phosphate cotransporter Npt2a, was greater than in vehicle-treated mice. The rachitic bone disease in Hyp mice is characterized by abundant unmineralized osteoid bone volume, widened epiphyses, and disorganized growth plates. In PD0325901-treated Hyp mice, mineralization of cortical and trabecular bone increased significantly, accompanied by a decrease in unmineralized osteoid volume and thickness, as determined by histomorphometric analysis. The improvement in mineralization in PD0325901-treated Hyp mice was confirmed by microcomputed tomography analysis, which showed an increase in cortical bone volume and thickness. These findings provide evidence that in Hyp mice, chronic MAPK inhibition improves disordered Pi and 1,25(OH)₂D metabolism and bone mineralization.

Decrease in circulating fibroblast growth factor 21 after an oral fat load is related to postprandial triglyceride-rich lipoproteins and liver fat

BACKGROUND

Elevated levels of circulating fibroblast growth factor 21 (FGF21) are commonly encountered in type 2 diabetes, dyslipidemia, and non-alcoholic fatty liver disease, all of which share exaggerated postprandial lipemia as a common proatherogenic feature. How FGF21 responds to an oral fat load in man is unknown.

METHODS

We measured liver fat contents and subcutaneous and visceral fat volumes in 47 healthy subjects, who also underwent an oral fat load with measurements of plasma FGF21 and free fatty acid (FFA). Triglyceride (TG), apolipoprotein B-48 (apoB-48), and apoB-100 concentrations were measured in triglyceride-rich lipoprotein (TRL) fractions.

RESULTS

When compared with fasting levels, the concentration of FGF21 decreased significantly at 4 h (P < 0.05) and tended to return to fasting levels at 8 h after an oral fat load. Fasting and postprandial FGF21 correlated significantly with liver fat as well as with TRLs in the chylomicron and especially in very low-density lipoprotein 1 (VLDL1) and VLDL2 fractions representing remnant particles, but not with FFA. Subjects with increased liver fat (>5%, n = 12) showed impaired suppression of FGF21 at 4 h (P < 0.05) and at 8 h (P=0.01) and demonstrated higher postprandial TG area under the curve in plasma and TRL fractions (P ≤ 0.032) compared with those with normal liver fat (≤ 5%, n = 35).

CONCLUSIONS

We observed a significant decrease of FGF21 concentration after an oral fat load. Fasting and postprandial FGF21 levels were closely related to large VLDL and remnants, but not to plasma FFA. Our pilot findings suggest that the postprandial accumulation of TRL remnants and liver fat may modulate postprandial FGF21 levels.

Exenatide decreases hepatic fibroblast growth factor 21 resistance in non-alcoholic fatty liver disease in a mouse model of obesity and in a randomised controlled trial

AIMS/HYPOTHESIS

Systemic fibroblast growth factor (FGF)21 levels and hepatic FGF21 production are increased in non-alcoholic fatty liver disease patients, suggesting FGF21 resistance. We examined the effects of exenatide on FGF21 in patients with type 2 diabetes and in a diet-induced mouse model of obesity (DIO).

METHODS

Type 2 diabetes mellitus patients (n = 24) on diet and/or metformin were randomised (using a table of random numbers) to receive additional treatment consisting of pioglitazone 45 mg/day or combined therapy with pioglitazone (45 mg/day) and exenatide (10 μg twice daily) for 12 months in an open label parallel study at the Baylor Clinic.

RESULTS

Twenty-one patients completed the entire study and were included in the analysis. Pioglitazone treatment (n = 10) reduced hepatic fat as assessed by magnetic resonance spectroscopy, despite a significant increase in body weight (Δ = 3.7 kg); plasma FGF21 levels did not change (1.9  ±  0.6 to 2.2  ±  0.6 ng/ml [mean ± SEM]). However, combined pioglitazone and exenatide therapy (n = 11) was associated with a significant reduction of FGF21 levels (2.3  ±  0.5 to 1.1  ±  0.3 ng/ml) and a greater decrease in hepatic fat. Besides weight gain observed in the pioglitazone-treated patients, lower extremity oedema was observed as a side effect in two of the ten patients. Three patients who received pioglitazone and exenatide combination therapy complained of significant nausea that was self-limiting and did not require them to leave the study. In DIO mice, exendin-4 for 4 weeks significantly reduced hepatic triacylglycerol content, decreased hepatic FGF21 protein and mRNA, and enhanced phosphorylation of hepatic AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase, although no significant difference in weight and body fat was observed. Hepatic FGF21 correlated inversely with hepatic AMPK phosphorylation

CONCLUSIONS/INTERPRETATION

In type 2 diabetes mellitus, combined pioglitazone and exenatide therapy is associated with a reduction in plasma FGF21 levels, as well as a greater decrease in hepatic fat than that achieved with pioglitazone therapy. In DIO mice, exendin-4 treatment reduces hepatic triacylglycerol and FGF21 protein, and enhances hepatic AMPK phosphorylation, suggesting an improvement of hepatic FGF21 resistance.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT 01432405.

FGF signaling pathway in the developing chick lung: expression and inhibition studies

Background

Fibroblast growth factors (FGF) are essential key players during embryonic development. Through their specific cognate receptors (FGFR) they activate intracellular cascades, finely regulated by modulators such as Sprouty. Several FGF ligands (FGF1, 2, 7, 9, 10 and 18) signaling through the four known FGFRs, have been implicated in lung morphogenesis. Although much is known about mammalian lung, so far, the avian model has not been explored for lung studies.

Methodology/Principal Findings

In this study we provide the first description of fgf10, fgfr1-4 and spry2 expression patterns in early stages of chick lung development by in situ hybridization and observe that they are expressed similarly to their mammalian counterparts. Furthermore, aiming to determine a role for FGF signaling in chick lung development, in vitro FGFR inhibition studies were performed. Lung explants treated with an FGF receptor antagonist (SU5402) presented an impairment of secondary branch formation after 48 h of culture; moreover, abnormal lung growth with a cystic appearance of secondary bronchi and reduction of the mesenchymal tissue was observed. Branching and morphometric analysis of lung explants confirmed that FGFR inhibition impaired branching morphogenesis and induced a significant reduction of the mesenchyme.

Conclusions/Significance

This work demonstrates that FGFRs are essential for the epithelial-mesenchymal interactions that determine epithelial branching and mesenchymal growth and validate the avian embryo as a good model for pulmonary studies, namely to explore the FGF pathway as a therapeutic target.

Fibroblast growth factor 21 as a possible endogenous factor inhibits apoptosis in cardiac endothelial cells

BACKGROUND

Fibroblast growth factor 21 (FGF21) is a new member of FGF super family that is an important endogenous regulator for systemic glucose and lipid metabolism. This study aimed to explore whether FGF21 reduces atherosclerotic injury and prevents endothelial dysfunction as an independent protection factor.

METHODS

The present study was designed to investigate the changes of FGF21 levels induced by oxidized-low density lipoprotein (ox-LDL), and the changes of apoptosis affected by regulating FGF21 expression. The FGF21 mRNA levels of cultured cardiac microvascular endothelial cells (CMECs) were determined by real time-PCR and the protein concentration in culture media was detected by enzyme-linked immunosorbent assay. We analyzed the different expression levels of untreated controls and CMECs incubated with ox-LDL, and the changes of CMECs apoptosis initiated by the enhancement or suppression of FGF21 levels.

RESULTS

The secretion levels of FGF21 mRNA and protein were significantly upregulated in CMECs incubated with ox-LDL. Furthermore, FGF21 levels increased by 200 µmol/L bezafibrate could reduce CMECs apoptosis, and inhibit FGF21 expression by shRNA induced apoptosis (P < 0.05).

CONCLUSIONS

FGF21 may be a signal of injured target tissue, and may play physiological roles in improving the endothelial function at an early stage of atherosclerosis and in stopping the development of coronary heart disease.

Fibroblast growth factor signalling: from development to cancer

Fibroblast growth factors (FGFs) and their receptors control a wide range of biological functions, regulating cellular proliferation, survival, migration and differentiation. Although targeting FGF signalling as a cancer therapeutic target has lagged behind that of other receptor tyrosine kinases, there is now substantial evidence for the importance of FGF signalling in the pathogenesis of diverse tumour types, and clinical reagents that specifically target the FGFs or FGF receptors are being developed. Although FGF signalling can drive tumorigenesis, in different contexts FGF signalling can mediate tumour protective functions; the identification of the mechanisms that underlie these differential effects will be important to understand how FGF signalling can be most appropriately therapeutically targeted.

Regulation of neural specification from human embryonic stem cells by BMP and FGF

Inhibition of bone morphogenetic protein (BMP) signaling is required for vertebrate neural induction, and fibroblast growth factors (FGFs) may affect neural induction through phosphorylation at the linker region of Smad1, thus regulating BMP signaling. Here we show that human embryonic stem cells efficiently convert to neuroepithelial cells in the absence of BMP antagonists, or even when exposed to high concentrations of exogenous BMP4. Molecular and functional analyses revealed multiple levels of endogenous BMP signaling inhibition that may account for the efficient neural differentiation. Blocking FGF signaling inhibited neural induction, but did not alter the phosphorylation of the linker region of Smad1, suggesting that FGF enhances human neural specification independently of BMP signaling.

Sprouty4, an FGF inhibitor, displays cyclic gene expression under the control of the notch segmentation clock in the mouse PSM

BACKGROUND

During vertebrate embryogenesis, somites are generated at regular intervals, the temporal and spatial periodicity of which is governed by a gradient of fibroblast growth factor (FGF) and/or Wnt signaling activity in the presomitic mesoderm (PSM) in conjunction with oscillations of gene expression of components of the Notch, Wnt and FGF signaling pathways.

PRINCIPAL FINDINGS

Here, we show that the expression of Sprouty4, which encodes an FGF inhibitor, oscillates in 2-h cycles in the mouse PSM in synchrony with other oscillating genes from the Notch signaling pathway, such as lunatic fringe. Sprouty4 does not oscillate in Hes7-null mutant mouse embryos, and Hes7 can inhibit FGF-induced transcriptional activity of the Sprouty4 promoter.

CONCLUSIONS

Thus, periodic expression of Sprouty4 is controlled by the Notch segmentation clock and may work as a mediator that links the temporal periodicity of clock gene oscillations with the spatial periodicity of boundary formation which is regulated by the gradient of FGF/Wnt activity.

Anti-angiogenic active immunotherapy: a new approach to cancer treatment

Tumor angiogenesis plays an important role in tumor growth, aggression and metastasis. Many molecules have been demonstrated as positive regulators of angiogenesis, including vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), epidermal growth factor (EGF), and others. In recent years, significant progress has been made in the research on anti-angiogenic strategies for tumor therapies. In this review, anti-angiogenic active immunotherapies for tumors based on vaccination with xenogeneic homologous molecules and non-xenogeneic homologous molecules are discussed.

The first steps towards hearing: mechanisms of otic placode induction

The entire inner ear, together with the neurons that innervate it, derive from a simple piece of ectoderm on the side of the embryonic head the otic placode. In this review, we describe the current state of the field of otic placode induction. Several lines of evidence suggest that all craniofacial sensory organs, including the inner ear, derive from a common "pre-placodal region" early in development. We review data showing that assumption of a pre-placodal cell state correlates with the competence of embryonic ectoderm to respond to otic placode inducing signals, such as members of the fibroblast growth factor (FGF) family. We also review evidence for FGF-independent signals that contribute to the induction of the otic placode. Finally, we review recent evidence suggesting that Wnt signals may act after FGF signaling to mediate a cell fate decision between otic placode and epidermis.