Impaired fibroblast growth factor receptor (FGFR) signaling is associated with many human conditions, including growth disorders, degenerative diseases, and cancer. Current FGFR therapeutics are based on chemical inhibitors of FGFR tyrosine kinase activity (TKIs). However, FGFR TKIs are limited in their target specificity as they generally inhibit all FGFRs and other receptor tyrosine kinases. In the search for specific inhibitors of human FGFR1, we identified VZ23, a DNA aptamer that binds to FGFR1b and FGFR1c with a KD of 55 nM and 162 nM, respectively, but not to the other FGFR variants (FGFR2b, FGFR2c, FGFR3b, FGFR3c, FGFR4). In cells, VZ23 inhibited the activation of downstream FGFR1 signaling and FGFR1-mediated regulation of cellular senescence, proliferation, and extracellular matrix homeostasis. Consistent with the specificity toward FGFR1 observed in vitro, VZ23 did not inhibit FGFR2-4 signaling in cells. We show that the VZ23 inhibits FGFR1 signaling in the presence of cognate fibroblast growth factor (FGF) ligands and its inhibitory activity is linked to its capacity to form unusual G-quadruplex structure. Our data suggest that targeting FGFR1 with DNA aptamers could be an effective alternative to TKIs for treating impaired FGFR1 signaling in human craniosynostoses.

• Keywords
• DNA aptamer, FGFR signaling, FGFR1, MT: Oligonucleotides: Therapies and Applications, craniosynostosis, extracellular domain, inhibitor, skeletal dysplasia,
• Publication type
• Journal Article MeSH

Achondroplasia is the most common form of human dwarfism caused by mutations in the FGFR3 receptor tyrosine kinase. Current therapy begins at 2 years of age and improves longitudinal growth but does not address the cranial malformations including midface hypoplasia and foramen magnum stenosis, which lead to significant otolaryngeal and neurologic compromise. A recent clinical trial found partial restoration of cranial defects with therapy starting at 3 months of age, but results are still inconclusive. The benefits of achondroplasia therapy are therefore controversial, increasing skepticism among the medical community and patients. We used a mouse model of achondroplasia to test treatment protocols aligned with human studies. Early postnatal treatment (from day 1) was compared with late postnatal treatment (from day 4, equivalent to ~5 months in humans). Animals were treated with the FGFR3 inhibitor infigratinib and the effect on skeleton was thoroughly examined. We show that premature fusion of the skull base synchondroses occurs immediately after birth and leads to defective cranial development and foramen magnum stenosis in the mouse model to achondroplasia. This phenotype appears significantly restored by early infigratinib administration when compared with late treatment, which provides weak to no rescue. In contrast, the long bone growth is similarly improved by both early and late protocols. We provide clear evidence that immediate postnatal therapy is critical for normalization of skeletal growth in both the cranial base and long bones and the prevention of sequelae associated with achondroplasia. We also describe the limitations of early postnatal therapy, providing a paradigm-shifting argument for the development of prenatal therapy for achondroplasia.

The article provides clear evidence that achondroplasia should be treated immediately after birth, not only to increase height (appendicular growth), but more importantly to prevent defective cranial skeletogenesis and associated severe neurological complications. Although later treatment promotes growth of the long bones (achondroplasia patients grow taller), the defective head skeleton that forms before and/or early after birth cannot be restored if therapy is not started immediately after birth. We also describe the limitations of postnatal treatment and make a strong case for the development of prenatal therapy for achondroplasia, which appears necessary for a comprehensive treatment of this condition.

• Keywords
• Fgfr3, achondroplasia, fibroblast growth factor, infigratinib, postnatal, treatment,
• MeSH
• Achondroplasia * pathology   drug therapy   MeSH
• Skull pathology   drug effects   MeSH
• Humans MeSH
• Disease Models, Animal * MeSH
• Mice MeSH
• Receptor, Fibroblast Growth Factor, Type 3 * genetics   metabolism   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Receptor, Fibroblast Growth Factor, Type 3 * MeSH

The FGF system is the most complex of all receptor tyrosine kinase signaling networks with 18 FGF ligands and four FGFRs that deliver morphogenic signals to pattern most embryonic structures. Even when a single FGFR is expressed in the tissue, different FGFs can trigger dramatically different biological responses via this receptor. Here we show both quantitative and qualitative differences in the signaling of one of the FGF receptors, FGFR1c, in response to different FGFs. We provide an overview of the recent discovery that FGFs engage in biased signaling via FGFR1c. We discuss the concept of ligand bias, which represents qualitative differences in signaling as it is a measure of differential ligand preferences for different downstream responses. We show how FGF ligand bias manifests in functional data in cultured chondrocyte cells. We argue that FGF-ligand bias contributes substantially to FGF-driven developmental processes, along with known differences in FGF expression levels, FGF-FGFR binding coefficients and differences in FGF stability in vivo.

• Keywords
• Bias, FGF, FGFR, Signaling,
• MeSH
• Chondrocytes metabolism   MeSH
• Fibroblast Growth Factors * metabolism   MeSH
• Humans MeSH
• Ligands MeSH
• Receptor, Fibroblast Growth Factor, Type 1 * metabolism   MeSH
• Receptors, Fibroblast Growth Factor * metabolism   MeSH
• Signal Transduction * MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Fibroblast Growth Factors * MeSH
• Ligands MeSH
• Receptor, Fibroblast Growth Factor, Type 1 * MeSH
• Receptors, Fibroblast Growth Factor * MeSH

The differential signaling of multiple FGF ligands through a single fibroblast growth factor (FGF) receptor (FGFR) plays an important role in embryonic development. Here, we use quantitative biophysical tools to uncover the mechanism behind differences in FGFR1c signaling in response to FGF4, FGF8, and FGF9, a process which is relevant for limb bud outgrowth. We find that FGF8 preferentially induces FRS2 phosphorylation and extracellular matrix loss, while FGF4 and FGF9 preferentially induce FGFR1c phosphorylation and cell growth arrest. Thus, we demonstrate that FGF8 is a biased FGFR1c ligand, as compared to FGF4 and FGF9. Förster resonance energy transfer experiments reveal a correlation between biased signaling and the conformation of the FGFR1c transmembrane domain dimer. Our findings expand the mechanistic understanding of FGF signaling during development and bring the poorly understood concept of receptor tyrosine kinase ligand bias into the spotlight.

• Keywords
• FGFR, biased signaling, molecular biophysics, none, signal transduction, structural biology,
• MeSH
• Fibroblast Growth Factors * MeSH
• Phosphorylation MeSH
• Humans MeSH
• Ligands MeSH
• Receptor, Fibroblast Growth Factor, Type 1 genetics   MeSH
• Signal Transduction * MeSH
• Pregnancy MeSH
• Bias MeSH
• Check Tag
• Humans MeSH
• Pregnancy MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• FGFR1 protein, human MeSH Browser
• Fibroblast Growth Factors * MeSH
• Ligands MeSH
• Receptor, Fibroblast Growth Factor, Type 1 MeSH

Many tyrosine kinase inhibitors (TKIs) have failed to reach human use due to insufficient activity in clinical trials. However, the failed TKIs may still benefit patients if their other kinase targets are identified by providing treatment focused on syndromes driven by these kinases. Here, we searched for novel targets of AZD1480, an inhibitor of JAK2 kinase that recently failed phase two cancer clinical trials due to a lack of activity. Twenty seven human receptor tyrosine kinases (RTKs) and 153 of their disease-associated mutants were in-cell profiled for activity in the presence of AZD1480 using a newly developed RTK plasmid library. We demonstrate that AZD1480 inhibits ALK, LTK, FGFR1-3, RET and TRKA-C kinases and uncover a physical basis of this specificity. The RTK activity profiling described here facilitates inhibitor repurposing by enabling rapid and efficient identification of novel TKI targets in cells.

• Keywords
• AZD1480, drug repurposing, in-cell profiling, inhibitor, receptor tyrosine kinase,
• Publication type
• Journal Article MeSH

The short rib polydactyly syndromes (SRPS) are a group of recessively inherited, perinatal-lethal skeletal disorders primarily characterized by short ribs, shortened long bones, varying types of polydactyly and concomitant visceral abnormalities. Mutations in several genes affecting cilia function cause SRPS, revealing a role for cilia function in skeletal development. To identify additional SRPS genes and discover novel ciliary molecules required for normal skeletogenesis, we performed exome sequencing in a cohort of patients and identified homozygosity for a missense mutation, p.E80K, in Intestinal Cell Kinase, ICK, in one SRPS family. The p.E80K mutation abolished serine/threonine kinase activity, resulting in altered ICK subcellular and ciliary localization, increased cilia length, aberrant cartilage growth plate structure, defective Hedgehog and altered ERK signalling. These data identify ICK as an SRPS-associated gene and reveal that abnormalities in signalling pathways contribute to defective skeletogenesis.

• MeSH
• Cilia genetics   pathology   MeSH
• Exome genetics   MeSH
• Infant MeSH
• Skeleton abnormalities   growth & development   MeSH
• Humans MeSH
• MAP Kinase Signaling System MeSH
• Abnormalities, Multiple genetics   physiopathology   MeSH
• Protein Serine-Threonine Kinases genetics   MeSH
• Hedgehog Proteins genetics   MeSH
• Pedigree MeSH
• Sequence Analysis, DNA MeSH
• Signal Transduction MeSH
• Short Rib-Polydactyly Syndrome genetics   pathology   MeSH
• Pregnancy MeSH
• Check Tag
• Infant MeSH
• Humans MeSH
• Pregnancy MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• CILK1 protein, human MeSH Browser
• Protein Serine-Threonine Kinases MeSH
• Hedgehog Proteins MeSH

Fibroblast growth factors (FGFs) deliver extracellular signals that govern many developmental and regenerative processes, but the mechanisms regulating FGF signaling remain incompletely understood. Here, we explored the relationship between intrinsic stability of FGF proteins and their biological activity for all 18 members of the FGF family. We report that FGF1, FGF3, FGF4, FGF6, FGF8, FGF9, FGF10, FGF16, FGF17, FGF18, FGF20, and FGF22 exist as unstable proteins, which are rapidly degraded in cell cultivation media. Biological activity of FGF1, FGF3, FGF4, FGF6, FGF8, FGF10, FGF16, FGF17, and FGF20 is limited by their instability, manifesting as failure to activate FGF receptor signal transduction over long periods of time, and influence specific cell behavior in vitro and in vivo. Stabilization via exogenous heparin binding, introduction of stabilizing mutations or lowering the cell cultivation temperature rescues signaling of unstable FGFs. Thus, the intrinsic ligand instability is an important elementary level of regulation in the FGF signaling system.

• MeSH
• Chondrosarcoma genetics   metabolism   pathology   MeSH
• Circular Dichroism MeSH
• Fibroblast Growth Factors chemistry   classification   genetics   metabolism   MeSH
• Rats MeSH
• Humans MeSH
• Mutation genetics   MeSH
• Mutant Proteins chemistry   metabolism   MeSH
• Tumor Cells, Cultured MeSH
• Bone Neoplasms genetics   metabolism   pathology   MeSH
• Breast Neoplasms genetics   metabolism   pathology   MeSH
• Cell Proliferation * MeSH
• Signal Transduction * MeSH
• Protein Stability MeSH
• Temperature MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Fibroblast Growth Factors MeSH
• Mutant Proteins MeSH

Cancer is a major public health problem worldwide. In the United States alone, 1 in 4 deaths is due to cancer and for 2013 a total of 1,660,290 new cancer cases and 580,350 cancer-related deaths are projected. Comprehensive profiling of multiple cancer genomes has revealed a highly complex genetic landscape in which a large number of altered genes, varying from tumor to tumor, impact core biological pathways and processes. This has implications for therapeutic targeting of signaling networks in the development of treatments for specific cancers. The NFκB transcription factor is constitutively active in a number of hematologic and solid tumors, and many signaling pathways implicated in cancer are likely connected to NFκB activation. A critical mediator of NFκB activity is TGFβ-activated kinase 1 (TAK1). Here, we identify TAK1 as a novel interacting protein and target of fibroblast growth factor receptor 3 (FGFR3) tyrosine kinase activity. We further demonstrate that activating mutations in FGFR3 associated with both multiple myeloma and bladder cancer can modulate expression of genes that regulate NFκB signaling, and promote both NFκB transcriptional activity and cell adhesion in a manner dependent on TAK1 expression in both cancer cell types. Our findings suggest TAK1 as a potential therapeutic target for FGFR3-associated cancers, and other malignancies in which TAK1 contributes to constitutive NFκB activation.

• MeSH
• Apoptosis MeSH
• Cell Adhesion MeSH
• Phosphorylation MeSH
• Immunoprecipitation MeSH
• Real-Time Polymerase Chain Reaction MeSH
• Humans MeSH
• MAP Kinase Kinase Kinases genetics   metabolism   MeSH
• RNA, Messenger genetics   MeSH
• Multiple Myeloma genetics   metabolism   pathology   MeSH
• Biomarkers, Tumor genetics   metabolism   MeSH
• Tumor Cells, Cultured MeSH
• Urinary Bladder Neoplasms genetics   metabolism   pathology   MeSH
• NF-kappa B genetics   metabolism   MeSH
• Peptide Fragments MeSH
• Reverse Transcriptase Polymerase Chain Reaction MeSH
• Cell Proliferation MeSH
• Receptor, Fibroblast Growth Factor, Type 3 genetics   metabolism   MeSH
• Oligonucleotide Array Sequence Analysis MeSH
• Signal Transduction MeSH
• Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization MeSH
• Gene Expression Profiling MeSH
• Two-Hybrid System Techniques MeSH
• Transforming Growth Factor beta genetics   metabolism   MeSH
• Tyrosine metabolism   MeSH
• Blotting, Western MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• FGFR3 protein, human MeSH Browser
• MAP kinase kinase kinase 7 MeSH Browser
• MAP Kinase Kinase Kinases MeSH
• RNA, Messenger MeSH
• Biomarkers, Tumor MeSH
• NF-kappa B MeSH
• Peptide Fragments MeSH
• Receptor, Fibroblast Growth Factor, Type 3 MeSH
• Transforming Growth Factor beta MeSH
• Tyrosine MeSH

In 1994, the field of bone biology was significantly advanced by the discovery that activating mutations in the fibroblast growth factor receptor 3 (FGFR3) receptor tyrosine kinase (TK) account for the common genetic form of dwarfism in humans, achondroplasia (ACH). Other conditions soon followed, with the list of human disorders caused by FGFR3 mutations now reaching at least 10. An array of vastly different diagnoses is caused by similar mutations in FGFR3, including syndromes affecting skeletal development (hypochondroplasia [HCH], ACH, thanatophoric dysplasia [TD]), skin (epidermal nevi, seborrhaeic keratosis, acanthosis nigricans), and cancer (multiple myeloma [MM], prostate and bladder carcinoma, seminoma). Despite many years of research, several aspects of FGFR3 function in disease remain obscure or controversial. As FGFR3-related skeletal dysplasias are caused by growth attenuation of the cartilage, chondrocytes appear to be unique in their response to FGFR3 activation. However, the reasons why FGFR3 inhibits chondrocyte growth while causing excessive cellular proliferation in cancer are not clear. Likewise, the full spectrum of molecular events by which FGFR3 mediates its signaling is just beginning to emerge. This article describes the challenging journey to unravel the mechanisms of FGFR3 function in skeletal dysplasias, the extraordinary cellular manifestations of FGFR3 signaling in chondrocytes, and finally, the progress toward therapy for ACH and cancer.

• MeSH
• Chondrocytes metabolism   pathology   MeSH
• Cartilage abnormalities   metabolism   MeSH
• Fibroblast Growth Factors genetics   metabolism   MeSH
• Phosphatidylinositol 3-Kinases genetics   metabolism   MeSH
• Bone and Bones abnormalities   metabolism   MeSH
• Skin metabolism   pathology   MeSH
• Genes, Lethal MeSH
• Humans MeSH
• MAP Kinase Signaling System genetics   MeSH
• Cell Communication MeSH
• Mutation MeSH
• Skin Neoplasms genetics   metabolism   pathology   MeSH
• Natriuretic Peptide, C-Type genetics   metabolism   MeSH
• Osteochondrodysplasias genetics   metabolism   pathology   MeSH
• Cell Proliferation MeSH
• Receptor, Fibroblast Growth Factor, Type 3 * genetics   metabolism   MeSH
• Gene Expression Regulation MeSH
• Signal Transduction MeSH
• STAT1 Transcription Factor genetics   metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• FGFR3 protein, human MeSH Browser
• Fibroblast Growth Factors MeSH
• Phosphatidylinositol 3-Kinases MeSH
• Natriuretic Peptide, C-Type MeSH
• Receptor, Fibroblast Growth Factor, Type 3 * MeSH
• STAT1 protein, human MeSH Browser
• STAT1 Transcription Factor MeSH