Fibroblast Growth Factor Receptor Tyrosine Research Articles

Slipped capital femoral epiphyses: A major on-target adverse event associated with FGFR tyrosine kinase inhibitors in pediatric patients.

Fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitors (TKIs) are increasingly being used off label in pediatrics. Long-term safety data are limited, and serious toxicities unique to pediatrics may emerge. In a retrospective analysis of patients less than 18years of age with recurrent/refractory FGFR altered gliomas treated with FGFR TKIs at MSKCC (n=7), we observed slipped capital femoral epiphyses in three of seven patients along with increased linear growth velocity. Clinicians should closely monitor bone health and have a low index of suspicion for serious orthopedic complications including slipped capital femoral epiphyses and inform patients of related risks as part of consent when treating with FGFR TKIs.

Gatekeeper mutations activate FGF receptor tyrosine kinases by destabilizing the autoinhibited state

Many types of human cancers are being treated with small molecule ATP-competitive inhibitors targeting the kinase domain of receptor tyrosine kinases. Despite initial successful remission, long-term treatment almost inevitably leads to the emergence of drug resistance mutations at the gatekeeper residue hindering the access of the inhibitor to a hydrophobic pocket at the back of the ATP-binding cleft. In addition to reducing drug efficacy, gatekeeper mutations elevate the intrinsic activity of the tyrosine kinase domain leading to more aggressive types of cancer. However, the mechanism of gain-of-function by gatekeeper mutations is poorly understood. Here, we characterized fibroblast growth factor receptor (FGFR) tyrosine kinases harboring two distinct gatekeeper mutations using kinase activity assays, NMR spectroscopy, bioinformatic analyses, and MD simulations. Our data show that gatekeeper mutations destabilize the autoinhibitory conformation of the DFG motif locally and of the kinase globally, suggesting they impart gain-of-function by facilitating the kinase's ability to populate the active state.

Prognostic implications of FGFR3high/Ki-67high in oral squamous cell carcinoma

ObjectiveFibroblast growth factor receptor 3 (FGFR3) is a member of the fibroblast growth factor receptor tyrosine kinase family. The prognosis and management stratification of oral squamous cell carcinoma (OSCC) are based on histology and other factors; however, immunohistochemical (IHC) markers that can detect OSCC that are more malignant and with a worse prognosis have not been adequately investigated. OSCC expresses activated FGFR3 signaling, which is not associated with prognosis. Currently, we explored the association between FGFR3 overexpression or the proliferation and histopathological hierarchy and stratum of risk. MethodsA total of 62 patients who had been diagnosed with OSCC at our department between January 2008 and December 2013 were included. The IHC expression of FGFR3 and Ki67 was analyzed in 45 (n = 37 tongue, 7 floor of mouth, 3 buccal mucosa) cases of OSCC. JMP14.2 was used for statistical analysis. ResultsA combined analysis of FGFR3high/Ki67high positivity resulted in a reduced mean overall survival (OS) of 67.3 months when comparing with all other combinations. In the multivariate analysis (MVA), high clinical stage (p = 0.036) and FGFR3high/Ki67high (p = 0.031) were significant independent risk factors for OS. ConclusionsWe identified FGFR3high/Ki67high OSCC as a subgroup that has a weak prognosis and OS. OSCC grading should probably be augmented by IHC staining, and tumors classified as having a worse prognosis require appropriate clinical surveillance.

FGF receptor inhibitor BGJ398 partially rescues osteoarthritis-like phenotype in older high molecular weight FGF2 transgenic mice via multiple mechanisms

We have used Basic Fibroblast Growth Factor (FGF2) transgenic mice as experimental models for human X-linked hypophosphatemia (XLH)-related degenerative osteoarthritis (OA) to investigate the pathogenesis of the disease and to test potential pharmacotherapies for treatment. This study tested the efficacy of BJG398, a small molecule fibroblast growth factor receptor tyrosine kinase (FGFRTK) inhibitor, to rescue the knee joint osteoarthritis phenotype in High Molecular Weight fibroblast growth factor 2 transgenic (HMWTgFGF2) mice. BJG398 was administered in vivo to 8-month-old female HMWTgFGF2 mice for six weeks. Histomorphometry, immunohistochemistry and micro-CT were used to examine the knee joints in BGJ398-treated and control mice. We assessed: Fibroblast Growth Factor 23 (FGF23) expression and FGFR1 activity; Matrix metalloproteinase 13 (MMP13) and Aggrecanase2 (ADAMTS5) expression; then signaling by SMAD1/5/8-pSMAD6, pERK1/2 and Runt-related transcription factor 2 (RUNX2). Using PrimePCR arrays, we identified a contributing role for major target genes in the TGFB/BMP2 signaling pathway that were regulated by BGJ398. BGJ398 inhibited HMWFGF2/FGF23-induced increase in bone morphogenic protein receptor-1, bone morphogenic protein-2 and 4 and Serine peptidase inhibitor, clade E, member 1. The results from Micro-CT and histology show BGJ398 treatment rescued the OA changes in subchondral bone and knee articular cartilage of HMWTgFGF2 mice. The gene expression and signal transduction results provide convincing evidence that HMWFGF2 generates OA through FGFRTK with characteristic downstream signaling that defines OA, namely: increased FGF23-FGFR1 activity with BMP-BMPR, activation of pSMAD1/5/8-RUNX2 and pERK signaling pathways, then upregulation of MMP13 and ADAMTS5 to degrade matrix. BGJ398 treatment effectively reversed these OA molecular phenotypes, providing further evidence that the OA generated by HMWFGF2 in the transgenic mice is FGFR-mediated and phenocopies the OA found in the Hyp mouse homolog of XLH with a spontaneous mutation in the Phex (phosphate regulating endopeptidase on the X chromosome) gene and human XLH-OA. Overall, the results obtained here explain how the pleotropic effects of FGF2 emanate from the different functions of HMW protein isoforms for cartilage and bone homeostasis, and the pathogenesis of XLH-degenerative osteoarthropathy. BGJ398 inhibits HMWFGF2-induced osteoarthritis via multiple mechanisms. These results provided important scientific evidence for the potential application of BGJ398 as a therapeutic agent for osteoarthritis in XLH.

The path to personalized treatment in advanced and metastatic biliary tract cancers: a review of new targeted therapies and immunotherapy.

To summarize targeted therapies and immunotherapy as treatment for advanced/metastatic biliary tract cancers and discuss ongoing clinical trials. For the first time since gemcitabine-cisplatin was set as the standard of care in first-line advanced/metastatic biliary tract cancers in the ABC-02 trial, the combination of durvalumab and gemcitabine-cisplatin has demonstrated a statistically significant improvement of median overall survival in the TOPAZ-1 phase 3 trial. The ABC-06 trial showed a significant increase of median overall survival for FOLFOX and active symptom control compared with active symptom control alone in second-line regardless of molecular and genetic alterations. However, faced with a heterogeneous cancer, patient prognosis remains poor, leaving room for new, personalized, treatment options such as targeted therapies. Efficacy of fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitors has been demonstrated in different phase 2 trials for previously treated intrahepatic cholangiocarcinomas harboring FGFR2 fusions. Ivosidenib increases significantly median progression-free survival in previously treated cholangiocarcinomas with isocitrate dehydrogenase-1 (IDH-1) mutation. Other targeted therapies are tested for tumors with HER2 amplifications/mutations, BRAFV600E mutations or KRASG12C mutations. In this review, we aim to follow the changes in the treatment of these tumors, moving from very few chemotherapy options to immunotherapy and targeted therapies in the context of molecular selection of biliary tract cancers subtypes.

Molecular mechanisms of the anti-cancer drug, LY2874455, in overcoming the FGFR4 mutation-based resistance

In recent years, many strategies have been used to overcome the fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitors (TKIs) resistance caused by different mutations. LY2874455 (or 6LF) is a pan-FGFR inhibitor which is identified as the most efficient TKI for all resistant mutations in FGFRs. Here, we perform a comparative dynamics study of wild type (WT) and the FGFR4 V550L mutant for better understanding of the 6LF inhibition mechanism. Our results confirm that the pan-FGFR inhibitor 6LF can bind efficiently to both WT and V550L FGFR4. Moreover, the communication network analysis indicates that in apo-WT FGFR4, αD–αE loop behaves like a switch between open and close states of the substrate-binding pocket in searching of its ligand. In contrast, V550L mutation induces the active conformation of the FGFR4 substrate-binding pocket through disruption of αD–αE loop and αG helix anti-correlation. Interestingly, 6LF binding causes the rigidity of hinge and αD helix regions, which results in overcoming V550L induced resistance. Collectively, the results of this study would be informative for designing more efficient TKIs for more effective targeting of the FGFR signaling pathway.

Novel Combination Therapies for the Treatment of Bladder Cancer.

Bladder cancer is the ninth most frequently diagnosed cancer world-wide and ranks 13th in cancer-related deaths. Two tremendous breakthroughs in bladder cancer therapy over the last decades are the approval of immune checkpoint inhibitors(ICIs)and the fibroblast growth factor receptor tyrosine kinase inhibitor (FGFR-TKI) erdafitinib for treating this deadly disease. Despite the beneficial effects of these approaches, the low response rate and the potential resistance of the cancer are major concerns. Hence, novel combination therapies to overcome these limitations have been investigated. In this context, combining immunotherapy with targeted drugs is an appealing therapeutic option to improve response and reduce the emergence of resistance in the management of bladder cancer. In this review, the rationale of using different therapeutic combinations is discussed according to the mechanistic differences, emphasizing the efficacy and safety based on evidence collected from preclinical and clinical studies. Finally, we highlight the limitations of these combinations and provide suggestions for further efforts in this challenging field.

Dermatologic Adverse Events Associated with Selective Fibroblast Growth Factor Receptor Inhibitors: Overview, Prevention, and Management Guidelines.

Fibroblast growth factor receptor (FGFR) tyrosine kinases, which are expressed on the cell membrane, are involved in a wide range of biological functions such as cell proliferation, survival, migration, and differentiation. The identification of FGFR fusions and other alterations in a wide range of solid tumors, including cholangiocarcinoma and bladder cancer, has resulted in the development of several selective FGFR inhibitors for use in these indications, for example, infigratinib, erdafitinib, derazantinib, pemigatinib, and futibatinib. In addition to the typical adverse events associated with tyrosine kinases, the FGFR inhibitors appear to give rise to a number of adverse events affecting the skin. Here we describe these skin events, which include the more common nail adverse events (e.g., onycholysis), palmar–plantar erythrodysesthesia syndrome, and stomatitis, as well as less common reactions such as calciphylaxis. This review aims to provide oncologists with an understanding of these dermatologic events and proposes guidelines for the management of treatment‐emergent dermatologic adverse events. Awareness of possible adverse events associated with specific drugs should allow physicians to educate patients as to what to expect and implement effective management plans at the earliest possible opportunity, thereby preventing premature discontinuation while maintaining patient quality of life.Implications for PracticeIdentification of fibroblast growth factor receptor (FGFR) aberrations in cholangiocarcinoma and bladder cancer led to development of selective FGFR inhibitors for these indications, based on clinical benefit and safety profiles. The most frequent adverse events (AEs) include those affecting skin, hair, and nails, a unique class effect of these agents. These are usually mild to moderate in severity. This work reviewed skin AEs reported with FGFR inhibitors and provides management guidelines for physicians, aiming to increase awareness of skin events and provide effective treatment strategies. Early intervention and effective management may improve treatment adherence, optimize outcomes, and improve quality of life.

Targeted Therapy in Metastatic Bladder Cancer: Present Status and Future Directions

The recommended treatment for metastatic urothelial carcinoma (mUC) patients is platinum-based chemotherapy. Although initial response rates are moderate, the vast majority of patients experience a relapse due to chemoresistance and eventually succumb to their disease. Furthermore, platinum-based chemotherapy is toxic and approximately 30% of mUC patients are unfit for chemotherapy. Thus, there is a clear unmet need for novel, more efficacious treatment options in mUC with a safer toxicity profile. To propel the advancement of novel treatment options, we present a summary of key signaling pathways and molecular mechanisms that are known to be involved in bladder cancer tumorigenesis with a focus on promising candidate druggable molecular targets and innovative targeted therapies currently under clinical investigation. Targetable alterations were mainly described in fibroblast growth factor receptor (FGFR) and epidermal growth factor receptor (ErbB) tyrosine kinase receptor (RTK) families, downstream pathways, and chromatin remodelers, which are major bladder cancer driver genes. Drugs targeting the FGFR family members are emerging as personalized treatment options for selected mUC patients with tumor-specific FGFR alterations. The pan-FGFR inhibitor, erdafitinib, was first-in-class to receive U.S. Food and Drug Administration (FDA) approval in 2019, while inhibitors of ErbB family members have shown less potential. Antibody-drug conjugates (ADCs) are a class of targeted therapeutics that deliver cytotoxic drugs in close proximity to cancer cells by targeting RTKs or other transmembrane proteins. Enfortumab vedotin is the first-in-class ADC that was FDA approved for the treatment of locally advanced or mUC in 2019.

Ocular Adverse Effects of Infigratinib, a New Fibroblast Growth Factor Receptor Tyrosine Kinase Inhibitor

Fibroblast growth factor receptors (FGFRs) are expressed in all major organs, including the eye (Fig S1, available at www.aaojournal.org).1 Fibroblast growth factor receptor tyrosine kinase inhibitors (TKIs) are under investigation, targeting various cancer types.1 Furthermore, 2 FGFR-TKIs have recently been Food and Drug Administration-approved for treating advanced urothelial carcinoma and cholangiocarcinoma. Fibroblast growth factor receptor inhibition commonly leads to hyperphosphatemia, fatigue, stomatitis, alopecia, nail changes, dry eye, and blurred vision.

Progress in Treatment of Advanced Squamous Cell Lung Cancer

肺癌是世界及中国发病率和死亡率第一的恶性肿瘤，肺鳞癌因其独特的临床表现、病理表现及基因突变特征，在诊治中与肺腺癌的区别显著，在临床研究中也作为单独的类型进行探索。除了肺鳞癌常表现为高龄、中央型肿瘤、诊断分期晚、合并症多，其往往少有驱动基因突变使得靶向治疗难以在肺鳞癌患者中获益，但是对于肺鳞癌的靶向治疗探索并未停止，包括纤维母细胞生长因子受体-酪氨酸激酶抑制剂和细胞周期蛋白依赖性激酶4和6抑制剂等新药在肺鳞癌患者中进行了多项I期研究。但随着免疫治疗的发展，鳞癌患者因其基因突变复杂，肿瘤突变负荷高等特点，免疫治疗联合化疗终于使肺鳞癌患者的预后有所改善。本文旨在从化疗、靶向治疗、抗血管治疗及免疫治疗几方面综述近年来晚期肺鳞癌的治疗进展。

A comparative analysis of fibroblast growth factor receptor signalling during Xenopus development.

The fibroblast growth factor (FGF) signalling system of vertebrates is complex. In common with other vertebrates, secreted FGF ligands of the amphibian Xenopus signal through a family of four FGF receptor tyrosine kinases (fgfr1, 2, 3 and 4). A wealth of previous studies has demonstrated important roles for FGF signalling in regulating gene expression during cell lineage specification in amphibian development. In particular, FGFs have well-established roles in regulating mesoderm formation, neural induction and patterning of the anteroposterior axis. However, relatively little is known regarding the role of individual FGFRs in regulating FGF-dependent processes in amphibian development. In this study we make use of synthetic drug inducible versions of Xenopus Fgfr1, 2 and 4 (iFgfr1, 2 and 4) to undertake a comparative analysis of their activities in the tissues of the developing embryo. We find that Xenopus Fgfr1 and 2 have very similar activities. Both Fgfr1 and Fgfr2 are potent activators of MAP kinase ERK signalling, and when activated in the embryo during gastrula stages regulate similar cohorts of transcriptional targets. In contrast, Fgfr4 signalling in naïve ectoderm and neuralised ectoderm activates ERK signalling only weakly compared to Fgfr1/2. Furthermore, our analyses indicate that in Xenopus neural tissue the Fgfr4 regulated transcriptome is very different from that of Fgfr1. We conclude that signalling downstream of Fgfr1 and 2 regulates similar processes in amphibian development. Interestingly, many of the previously identified canonical transcriptional targets of FGF regulation associated with germ layer specification and patterning are regulated by Fgfr1/Fgfr2 signalling. In contrast, the downstream consequences of Fgfr4 signalling are different, although roles for Fgfr4 signalling in lineage specification and anteroposterior patterning are also indicated.

Cell signaling molecules in hydra: insights into evolutionarily ancient functions of signaling pathways.

Hydra, a Cnidarian believed to have been evolved about 60 million years ago, has been a favorite model for developmental biologists since Abraham Trembley introduced it in 1744. However, the modern renaissance in research on hydra was initiated by Alfred Gierer when he established a hydra laboratory at the Max Plank Institute in Göttingen in the late 1960s. Several signaling mechanisms that regulate development and pattern formation in vertebrates, including humans, have been found in hydra. These include Wnt, BMP, VEGF, FGF, Notch, and RTK signaling pathways. We have been using hydra to understand the evolution of cell signaling for the past several years. In this article, I will summarize the work on cell signaling pathways in hydra with emphasis on our own work. We have identified and characterized, for the first time, the hydra homologs of the BMP inhibitors Noggin and Gremlin, the vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF) and several receptor tyrosine kinases (RTKs). Our work, along with that of others, clearly demonstrates that these pathways arose early in evolution to carry out functions that were often quite different from their functions in more complex animals. Apart from providing insights into morphogenesis and pattern formation in adult, budding and regenerating hydra, these findings bring out the utility of hydra as a model system to study evolutionarily ancient, in contrast to recently acquired, functions of various biological molecules.

A miRNA Panel Predicts Sensitivity of FGFR Inhibitor in Lung Cancer Cell Lines

PurposeTo test whether a microRNA (miRNA) panel may serve as an alternative biomarker of fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitor sensitivity in lung cancer. MethodsHistologically diverse lung cancer cell lines were submitted to assays for ponatinib and AZD4547 sensitivity. miRNAs, FGFR1 messenger RNA, gene copy number, and protein expression were detected by real-time quantitative PCR, fluorescence in-situ hybridization, and immunoblotting in 34 lung cancer cell lines. ResultsAmong 34 cell lines, 14 exhibited ponatinib sensitivity and 20 exhibited AZD4547 sensitivity (drug concentration causing 50% inhibition values < 100 nmol/L). A total of 39 of the 377-miRNA set were initially identified from the 4 paired ponatinib-sensitive or -insensitive cell lines to have at least an 8-fold differential expression and then were detected in all the 34 cell lines. A predictive panel of 3 miRNAs (let-7c, miRNA155, and miRNA218) was developed that had an area under the curve (AUC) of 0.886 with a sensitivity of 71.4% and specificity of 77.3% to predict response to ponatinib. The miRNA panel performed similar to FGFR1 protein expression (AUC = 0.864) and messenger RNA expression (AUC = 0.939), and better than FGFR1 amplification (AUC = 0.696). Furthermore, we validated this panel using data for sensitivity to AZD4547 in the cell line cohort with an AUC of 0.931 and a sensitivity of 73.3% and specificity of 76.2%, respectively. ConclusionThe developed miRNA panel (let-7c, miRNA155, and miRNA218) may be useful in predicting response to FGFR tyrosine kinase inhibitors, either ponatinib or AZD4547 in lung cancer cell lines, and warrants further validation in the clinical setting.

Nintedanib inhibits macrophage activation and ameliorates vascular and fibrotic manifestations in the Fra2 mouse model of systemic sclerosis

BackgroundNintedanib is an inhibitor targeting platelet-derived growth factor receptor, fibroblast growth factor receptor and vascular endothelial growth factor receptor tyrosine kinases that has recently been approved for the treatment of...

Abstract CT057: Phase 2, open-label, multicenter study to evaluate the efficacy and safety of INCB054828 in patients with myeloid/lymphoid neoplasms with fibroblast growth factor receptor 1 (FGFR1) rearrangement

Abstract Background: Dysregulation of FGFR signaling is strongly implicated in the establishment and progression of many cancers; rearrangements in chromosome 8p11 leading to activation of FGFR1 have been associated with rare but aggressive myeloid and lymphoid neoplasms with eosinophilia. INCB054828 is a novel, selective, orally administered inhibitor of FGFR1, FGFR2, and FGFR3 tyrosine kinase activities (AACR 2015; Abstract 771). Methods: This open-label, single-arm, phase 2 study will evaluate the efficacy and safety of INCB054828 monotherapy in patients with myeloid/lymphoid neoplasms with FGFR1 rearrangement (Table; NCT03011372). Eligible patients are ≥18 years of age, have documented lymphoid or myeloid neoplasm with 8p11 rearrangement known to lead to FGFR1 activation and have an Eastern Cooperative Oncology Group performance status ≤2. In addition, patients must not be candidates for stem cell transplant (or must have relapsed after transplant and delayed lymphocyte infusion); must have progressed on ≥1 prior anticancer treatment; must not be eligible for other disease-modifying therapies. Patients will self-administer INCB054828 orally, once-daily at a starting dose of 13.5 mg on a 21-day cycle (2 wks on; 1 wk off); treatment will continue until disease progression or unacceptable toxicity occurs. The primary endpoint will be overall clinical benefit rate (proportion of patients with complete or partial response, complete hematologic response, cytogenetic response, marrow response [see Table for response criteria], or clinical benefit). Secondary endpoints will include duration of response/clinical benefit, progression-free survival, overall survival, and safety. The study is currently recruiting (planned enrollment, n~46); primary analysis is expected in January 2019. Study DesignScreen for eligibility criteria and patient characteristics• Documented lymphoid/myeloid neoplasm with 8p11 rearrangement known to lead to FGFR1 activation• Not candidates for stem cell transplantation (or have relapsed after transplantation and delayed lymphocyte infusion); progression on ≥1 prior anticancer treatment; not suitable for other disease-modifying therapies• Eastern Cooperative Oncology Group performance status ≤2• Adequate hepatic function (total bilirubin ≤1.5 × upper limit of normal [ULN; ≤2.5 × ULN for Gilbert syndrome or disease involving liver]; aminotransferases &amp;lt;2.5 × ULN [&amp;lt;5 × ULN with disease involving liver])• Adequate renal function (creatinine clearance ≥30 mL/min; serum phosphate &amp;gt;institutional ULN; serum calcium within institutional normal range)• Life expectancy ≥12 weeksEnroll and initiate INCB054828 treatment• Oral once daily dosing: 21-day (2-weeks-on/1-week-off) cycleStart disease assessment* after cycle 2• Stable disease/partial or complete response → continue treatment on 21-day cycle• Disease progression → discontinue treatment; safety and survival follow-up*Bone marrow (BM) aspirates every 3 cycles starting from cycle 2 day 1 until month 12; then every 12 cycles until month 24 for patients with confirmed complete cytogenetic response; then every 12 months until disease progression or end of treatment. Response criteria are:• Complete response (CR): presence of all the following (1) bone marrow: ≤5% myeloblasts; 0% lymphoblasts; (2) peripheral blood: WBC ≤10x109/L; Hgb ≥11 g/dL; ≥100×109/L platelets ≤450×109/L; neutrophils ≥1.0×109/L; blasts 0%; neutrophil precursors ≤2%; monocytes ≤1×109/L; eosinophils ≤0.5×109/L; (3) prior extramedullary disease completely resolved• Complete cytogenetic response (CCyR): no 8p11 translocations• Complete hematologic response (CHR): see (2) under CR• Complete marrow response (CMR): see (1) under CR Citation Format: Srdan Verstovsek, Alessandro Rambaldi, Ekaterine Asatiani, Christine F. Lihou, Huiling Zhen, Andreas Hochhaus. Phase 2, open-label, multicenter study to evaluate the efficacy and safety of INCB054828 in patients with myeloid/lymphoid neoplasms with fibroblast growth factor receptor 1 (FGFR1) rearrangement [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT057. doi:10.1158/1538-7445.AM2017-CT057

Elucidation of a four-site allosteric network in fibroblast growth factor receptor tyrosine kinases.

Receptor tyrosine kinase (RTK) signaling is tightly regulated by protein allostery within the intracellular tyrosine kinase domains. Yet the molecular determinants of allosteric connectivity in tyrosine kinase domain are incompletely understood. By means of structural (X-ray and NMR) and functional characterization of pathogenic gain-of-function mutations affecting the FGF receptor (FGFR) tyrosine kinase domain, we elucidated a long-distance allosteric network composed of four interconnected sites termed the 'molecular brake', 'DFG latch', 'A-loop plug', and 'αC tether'. The first three sites repress the kinase from adopting an active conformation, whereas the αC tether promotes the active conformation. The skewed design of this four-site allosteric network imposes tight autoinhibition and accounts for the incomplete mimicry of the activated conformation by pathogenic mutations targeting a single site. Based on the structural similarity shared among RTKs, we propose that this allosteric model for FGFR kinases is applicable to other RTKs.

Fibroblast growth factors as tissue repair and regeneration therapeutics.

Cell communication is central to the integration of cell function required for the development and homeostasis of multicellular animals. Proteins are an important currency of cell communication, acting locally (auto-, juxta-, or paracrine) or systemically (endocrine). The fibroblast growth factor (FGF) family contributes to the regulation of virtually all aspects of development and organogenesis, and after birth to tissue maintenance, as well as particular aspects of organism physiology. In the West, oncology has been the focus of translation of FGF research, whereas in China and to an extent Japan a major focus has been to use FGFs in repair and regeneration settings. These differences have their roots in research history and aims. The Chinese drive into biotechnology and the delivery of engineered clinical grade FGFs by a major Chinese research group were important enablers in this respect. The Chinese language clinical literature is not widely accessible. To put this into context, we provide the essential molecular and functional background to the FGF communication system covering FGF ligands, the heparan sulfate and Klotho co-receptors and FGF receptor (FGFR) tyrosine kinases. We then summarise a selection of clinical reports that demonstrate the efficacy of engineered recombinant FGF ligands in treating a wide range of conditions that require tissue repair/regeneration. Alongside, the functional reasons why application of exogenous FGF ligands does not lead to cancers are described. Together, this highlights that the FGF ligands represent a major opportunity for clinical translation that has been largely overlooked in the West.

Fibroblast growth factor receptor 3 protein is overexpressed in oral and oropharyngeal squamous cell carcinoma

Fibroblast growth factor receptor 3 (FGFR3) is a member of the fibroblast growth factor receptor tyrosine kinase family. It has been identified as a promising therapeutic target in multiple types of cancer. We have investigated FGFR3 protein expression and FGFR3 gene copy-numbers in a single well-documented cohort of oral and oropharyngeal squamous cell carcinoma. Tissue microarray sets containing 452 formalin-fixed paraffin-embedded tissues were immunohistochemically stained with an anti-FGFR3 antibody and hybridized with a FGFR3 fluorescence in situ hybridization probe. FGFR3 protein expression was correlated with clinicopathological and survival data, which were retrieved from electronic medical records. FGFR3 mRNA data of 522 head and neck squamous cell carcinoma (HNSCC) were retrieved from The Cancer Genome Atlas (TCGA). Fibroblast growth factor receptor 3 (FGFR3) protein was overexpressed in 48% (89/185) of oral and 59% (124/211) of oropharyngeal squamous cell carcinoma. Overexpression of FGFR3 protein was not related to overall survival or disease-free survival in oral (HR[hazard ratio]: 0.94; 95% CI: 0.64-1.39; P=0.77, HR: 0.94; 95% CI: 0.65-1.36; P=0.75) and oropharyngeal squamous cell carcinoma (HR: 1.21; 95% CI: 0.81-1.80; P=0.36, HR: 0.42; 95% CI: 0.79-1.77; P=0.42). FGFR3 mRNA was upregulated in 3% (18/522) of HNSCC from the TCGA. The FGFR3 gene was gained in 0.6% (1/179) of oral squamous cell carcinoma but no amplification was found in oral and oropharyngeal squamous cell carcinoma. In conclusion, FGFR3 protein is frequently overexpressed in oral and oropharyngeal squamous cell carcinoma. Therefore, it may serve as a potential therapeutic target for FGFR3-directed therapies in oral and oropharyngeal squamous cell carcinoma.

FAIMS and Phosphoproteomics of Fibroblast Growth Factor Signaling: Enhanced Identification of Multiply Phosphorylated Peptides.

We have applied liquid chromatography high-field asymmetric waveform ion mobility spectrometry tandem mass spectrometry (LC-FAIMS-MS/MS) and liquid chromatography tandem mass spectrometry (LC-MS/MS) to the investigation of site-specific phosphorylation in fibroblast growth factor (FGF) signaling. We have combined a SILAC approach with chemical inhibition by SU5402 (an FGF receptor tyrosine kinase inhibitor) and dasatinib (a Src family kinase inhibitor). The results show that incorporation of FAIMS within the workflow results in (a) an increase in the relative proportion of phosphothreonine and phosphotyrosine sites identified, (b) an increase in phosphopeptide identifications from precursors with charge states ≥ +3 (with an associated increase in peptide length), and (c) an increase in the identification of multiply phosphorylated peptides. Approximately 20% of the phosphorylation sites identified via the FAIMS workflow had not been reported previously, and over 80% of those were from multiply phosphorylated peptides. Moreover, FAIMS provided access to a distinct set of phosphorylation sites regulated in response to SU5402 and dasatinib. The enhanced identification of multiply phosphorylated peptides was particularly striking in the case of sites regulated by SU5402. In addition to providing a compelling example of the complementarity of FAIMS in phosphoproteomics, the results provide a valuable resource of phosphorylation sites for further investigation of FGF signaling and trafficking.