Fibroblast growth factor receptor 4: the missing link between chronic kidney disease and FGF23-induced left ventricular hypertrophy?

Serum phosphorus and the regulatory hormone fibroblast growth factor 23 have been strongly linked to cardiovascular morbidity and mortality in patients with chronic kidney disease. A recent study identified fibroblast growth factor receptor 4 as the primary receptor mediating the effect of fibroblast growth factor 23 on left ventricular hypertrophy, providing new mechanistic insights and a potential therapeutic target to reduce cardiovascular morbidity in chronic kidney disease.

Screening a novel FGF3 antagonist peptide with anti-tumor effects on breast cancer from a phage display library.

Accumulating evidence has suggested that fibroblast growth factor 3 (FGF3) is expressed in breast cancer and correlates with the stage and grade of the disease. In the present study, a specific FGF3­binding peptide (VLWLKNR, termed FP16) was isolated from a phage display heptapeptide library with FGF3. The peptide FP16 contained four identical (WLKN) amino acids and demonstrated high homology to the peptides of the 188­194 (TMRWLKN) site of the high­affinity FGF3 receptor fibroblast growth factor receptor 2. Functional analyses indicated that FP16 mediated significant inhibition of FGF3­induced cell proliferation, arrested the cell cycle at the G0/G1 phase by increasing proliferation­associated protein 2G4, suppressing cyclin D1 and proliferating cell nuclear antigen, and inhibited the FGF3­induced activation of extracellular signal­regulated kinase 1/2 and Akt kinase. Taken together, these results demonstrated that the peptide FP16, acting as an FGF3 antagonist, is a promising therapeutic agent for the treatment of breast cancer.

A mutation in cnot8, component of the Ccr4-not complex regulating transcript stability, affects expression levels of developmental regulators and reveals a role of Fgf3 in development of caudal hypothalamic dopaminergic neurons.

While regulation of the activity of developmental control genes at the transcriptional level as well as by specific miRNA-based degradation are intensively studied, little is known whether general cellular mechanisms controlling mRNA decay may contribute to differential stability of mRNAs of developmental control genes. Here, we investigate whether a mutation in the deadenylation dependent mRNA decay pathway may reveal differential effects on developmental mechanisms, using dopaminergic differentiation in the zebrafish brain as model system. In a zebrafish genetic screen aimed at identifying genes controlling dopaminergic neuron development we isolated the m1061 mutation that selectively caused increased dopaminergic differentiation in the caudal hypothalamus, while other dopaminergic groups were not affected. Positional cloning revealed that m1061 causes a premature stop codon in the cnot8 open reading frame. Cnot8 is a component of the Ccr4-Not complex and displays deadenylase activity, which is required for removal of the poly (A) tail in bulk mRNA turnover. Analyses of expression of developmental regulators indicate that loss of Cnot8 activity results in increased mRNA in situ hybridization signal levels for a subset of developmental control genes. We show that in the area of caudal hypothalamic dopaminergic differentiation, mRNA levels for several components of the FGF signaling pathway, including Fgf3, FGF receptors, and FGF target genes, are increased. Pharmacological inhibition of FGF signaling or a mutation in the fgf3 gene can compensate the gain of caudal hypothalamic dopaminergic neurons in cnot8m1061 mutants, indicating a role for Fgf3 in control of development of this dopaminergic population. The cnot8m1061 mutant phenotype provides an in vivo system to study roles of the Cnot8 deadenylase component of the mRNA decay pathway in vertebrate development. Our data indicate that attenuation of Cnot8 activity differentially affects mRNA levels of developmental control genes.

Targeting FGFR with dovitinib (TKI258): preclinical and clinical data in breast cancer.

PURPOSE: Fibroblast growth factor receptor 1 (FGFR1) and FGFR2 amplifications are observed in approximately 10% of breast cancers and are related to poor outcomes. We evaluated whether dovitinib (TKI258), an inhibitor of FGFR1, FGFR2, and FGFR3, presented antitumor activity in FGFR-amplified breast cancers. EXPERIMENTAL DESIGN: Preclinical activity of dovitinib was evaluated in both breast cancer cell lines and an FGFR1-amplified xenograft model (HBCx2). Dovitinib was then evaluated in a phase II trial that included 4 groups of patients with human EGF receptor 2-negative metastatic breast cancer on the basis of FGFR1 amplification and hormone receptor (HR) status. FGFR1 amplification was assessed by silver in situ hybridization. Preplanned retrospective analyses assessed predictive value of FGFR1, FGFR2, and FGF3 amplifications by quantitative PCR (qPCR). RESULTS: Dovitinib monotherapy inhibits proliferation in FGFR1- and FGFR2-amplified, but not FGFR-normal, breast cancer cell lines. Dovitinib also inhibits tumor growth in FGFR1-amplified breast cancer xenografts. Eighty-one patients were enrolled in the trial. Unconfirmed response or stable disease for more than 6 months was observed in 5 (25%) and 1 (3%) patient(s) with FGFR1-amplified/HR-positive and FGFR1-nonamplified/HR-positive breast cancer. When qPCR-identified amplifications in FGFR1, FGFR2, or FGF3 were grouped to define an FGF pathway-amplified breast cancer in HR-positive patients, the mean reduction in target lesions was 21.1% compared with a 12.0% increase in patients who did not present with FGF pathway-amplified breast cancer. CONCLUSION: Dovitinib showed antitumor activity in FGFR-amplified breast cancer cell lines and may have activity in breast cancers with FGF pathway amplification.

FGF3/FGF4 amplification and multiple lung metastases in responders to sorafenib in hepatocellular carcinoma.

UNLABELLED: The response rate to sorafenib in hepatocellular carcinoma (HCC) is relatively low (0.7%-3%), however, rapid and drastic tumor regression is occasionally observed. The molecular backgrounds and clinico-pathological features of these responders remain largely unclear. We analyzed the clinical and molecular backgrounds of 13 responders to sorafenib with significant tumor shrinkage in a retrospective study. A comparative genomic hybridization analysis using one frozen HCC sample from a responder demonstrated that the 11q13 region, a rare amplicon in HCC including the loci for FGF3 and FGF4, was highly amplified. A real-time polymerase chain reaction-based copy number assay revealed that FGF3/FGF4 amplification was observed in three of the 10 HCC samples from responders in which DNA was evaluable, whereas amplification was not observed in 38 patients with stable or progressive disease (P = 0.006). Fluorescence in situ hybridization analysis confirmed FGF3 amplification. In addition, the clinico-pathological features showed that multiple lung metastases (5/13, P = 0.006) and a poorly differentiated histological type (5/13, P = 0.13) were frequently observed in responders. A growth inhibitory assay showed that only one FGF3/FGF4-amplified and three FGFR2-amplified cancer cell lines exhibited hypersensitivity to sorafenib in vitro. Finally, an in vivo study revealed that treatment with a low dose of sorafenib was partially effective for stably and exogenously expressed FGF4 tumors, while being less effective in tumors expressing EGFP or FGF3. CONCLUSION: FGF3/FGF4 amplification was observed in around 2% of HCCs. Although the sample size was relatively small, FGF3/FGF4 amplification, a poorly differentiated histological type, and multiple lung metastases were frequently observed in responders to sorafenib. Our findings may provide a novel insight into the molecular background of HCC and sorafenib responders, warranting further prospective biomarker studies.