Mutations In Fibroblast Growth Factor Receptor Research Articles

The Effect of Activating Fibroblast Growth Factor Receptor 3 Mutations on Osteogenic Differentiation and Ectopic Bone Formation by Human Periosteal Derived Cells

Activating mutations in Fibroblast Growth Factor Receptor 3 (FGFR3) have previously been shown to cause skeletal dysplasias through their effect on growth plate chondrocytes. However, the effect of FGFR3 mutations on bone progenitor cells may differ. The objective of this study was to investigate the effect of specific activating FGFR3 mutations on ectopic in vivo bone formation by periosteal derived cells (PDCs) seeded on calcium phosphate/ collagen scaffolds. PDCs were isolated from hypochondroplasic (N540K mutation) and achondroplasic (G380R mutation) patients, along with age/sex matched controls. These cells were characterised in vitro for proliferation, osteogenic differentiation, FGFR3 signalling and in vivo bone formation. Subsequently, empirical modelling was used to find correlations between in vivo formed bone and in vitro cell behaviour. These data showed that in contrast to the G380R mutation, which produced no bone, the N540K mutation induced significant ectopic bone formation on specific carriers. This allowed correlation between percentage of induced bone formation to elevated in vitro proliferation and differentiation. Correlating osteogenic markers included Collagen type 1, alkaline phosphatase and osteocalcin. Enhanced proliferation was attributed to increased phosphorylation of Erk-1/2.

Mutational activation of FGFR3: no involvement in the development of renal cell carcinoma

Somatic point mutations in the fibroblast growth factor receptor 3 (FGFR3) gene have been identified in certain types of urological cancers, especially urothelial carcinoma of the bladder and the renal pelvis, and could be correlated with a favourable outcome. However, comprehensive data on the FGFR3 mutation status in renal cell carcinoma (RCC) are still missing. In order to investigate a possible role for FGFR3 mutations in renal cell carcinogenesis, we performed a sequence-based mutational analysis of FGFR3 in 238 primary RCC. The cohort obtained the common RCC subtypes including 101 clear cell, 50 papillary and 68 chromophobe RCC specimens. The analysed regions encompassed all FGFR3 point mutations previously described in epithelial tumours and other noncutaneous epithelial malignancies. No mutations were detected in any renal tumour type examined, and all cases showed wild-type sequence. Our results argue against an involvement of mutational activation of FGFR3 in the development of RCC. A recently described cystic renal dysplasia in a patient with thanatophoric dysplasia type 1 due to a germ line FGFR3 mutation might portend to an involvement of mutational FGFR3 activation in renal cyst formation, but this speculation needs further evaluation.

Sixteen years and counting: The current understanding of fibroblast growth factor receptor 3 (FGFR3) signaling in skeletal dysplasias

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.

FGFR2 alterations in endometrial carcinoma

Fibroblast growth factor receptor 2 (FGFR2) is a tyrosine kinase receptor involved in many biological processes such as embryogenesis, adult tissue homeostasis and cell proliferation. Mutations in FGFR2 have been reported in up to 10–12% of endometrial carcinomas identical to those found in congenital craniofacial disorders. Inhibition of FGFR2 could be a new therapeutic target in endometrial carcinoma. FGFR2 immunostaining was assessed in three tissue microarrays: one constructed from paraffin-embedded blocks of 60 samples of normal endometrium in different phases of menstrual cycle, and two tissue microarrays containing endometrial carcinoma samples (95 and 62 cases). FGFR2 expression was correlated with stage, histological type and grade as well as with immunostaining of PTEN, RASSF1A, estrogen and progesterone receptors, KI67, Cyclin D1, STAT-3 and SPRY2. FGFR2 mutations were assessed by PCR and direct sequencing, with DNA obtained from 31 paraffin-embedded endometrial carcinoma samples. In normal endometrium, FGFR2 expression was higher in the secretory than in the proliferative phase (P=0.001), with an inverse correlation with Ki67 (P=0.00032), suggesting a tumor-suppressor role for FGFR2 in normal endometrium. Cytoplasmic expression of FGFR2 was higher in endometrial carcinoma when compared with the atrophic endometrium from the same patients (P=0.0283), but was lower in comparison with normal endometrium from women in the menstrual cycle. Interestingly, nuclear staining was observed in some cases, and it was less frequent in endometrial carcinoma when compared with the adjacent atrophic endometrium (P=0.0465). There were no statistical differences when comparing superficial and myoinvasive endometrial carcinoma samples. Endometrioid endometrial carcinomas showed higher expression of FGFR2 than nonendometrioid endometrial carcinomas (fold change 2.56; P=0.0015). Grade III endometrioid endometrial carcinomas showed decreased FGFR2 expression when compared with grade II endometrioid endometrial carcinomas (P=0.0055). No differences were found regarding pathological stage. Two missense mutations of FGFR2 gene were detected in exons 6 and 11 (S252W and N549K, respectively; 6.45%). Results support the hypothesis that FGFR2 has a dual role in the endometrium, by inhibiting cell proliferation in normal endometrium during the menstrual cycle, but acting as an oncogene in endometrial carcinoma.

Utilization of Unlabeled Probes for the Detection of Fibroblast Growth Factor Receptor 2 Exons 7 and 12 Mutations in Endometrial Carcinoma

Endometrial adenocarcinomas are associated with a variety of molecular abnormalities including microsatellite instability, Kirsten rat sarcoma viral oncogene homolog mutations, and phosphatase and tensin homolog inactivation. Recently, mutations in fibroblast growth factor receptor 2 (FGFR2) have been described but their frequency and clinicopathologic characteristics are incompletely known. To determine the frequency of mutations in FGFR2 exons 7 and 12, 43 adenocarcinomas of the endometrium were studied by high-resolution melting analysis utilizing unlabeled probes and sequencing. Three of 43 (7%) endometrial carcinomas harbored FGFR2 exon 7 mutations. All 3 mutations were S252W and occurred in endometrioid (type I) adenocarcinomas. Direct sequencing indicated that 2 of the S252W mutations were heterozygous, whereas 1 was presumably homozygous. No FGFR2 mutations were detected in exon 12. FGFR2 mutations occur in approximately 7% of adenocarcinomas of the endometrium. Only carcinomas of an endometrioid morphology contain FGFR2 mutations, and in our series all were S252W. FGFR2 exons 7 and 12 unlabeled DNA probes allow for easy screening of endometrial carcinoma for the 2 most common FGFR2 mutations (S252W and N550K). Identification of these mutations may have important implications in directed molecular therapy.

Effects of diadenosine tetraphosphate on FGF9-induced chloride flux changes in achondroplastic chondrocytes

Achondroplasia, the most common type of dwarfism, is characterized by a mutation in the fibroblast growth factor receptor 3 (FGFR3). Achondroplasia is an orphan pathology with no pharmacological treatment so far. However, the possibility of using the dinucleotide diadenosine tetraphosphate (Ap(4)A) with therapeutic purposes in achondroplasia has been previously suggested. The pathogenesis involves the constitutive activation of FGFR3, resulting in altered biochemical and physiological processes in chondrocytes. Some of these altered processes can be influenced by changes in cell volume and ionic currents. In this study, the action of mutant FGFR3 on chondrocyte size and chloride flux in achondroplastic chondrocytes was investigated as well as the effect of the Ap(4)A on these processes triggered by mutant FGFR3. Stimulation with the fibroblast growth factor 9 (FGF9), the preferred ligand for FGFR3, induced an enlarged achondroplastic chondrocyte size and an increase in the intracellular chloride concentration, suggesting the blockade of chloride efflux. Treatment with the Ap(4)A reversed the morphological changes triggered by FGF9 and restored the chloride efflux. These data provide further evidence for the therapeutic potential of this dinucleotide in achondroplasia treatment.

Fibroblast Growth Factor Receptor-3 (FGFR-3) Regulates Expression of Paneth Cell Lineage-specific Genes in Intestinal Epithelial Cells through both TCF4/β-Catenin-dependent and -independent Signaling Pathways

Fibroblast growth factor receptor-3 (FGFR-3) expression in the developing intestine is restricted to the undifferentiated epithelial cells within the lower portion of the crypt. We previously showed that mice lacking functional FGFR-3 have a significant decrease in the number of Paneth cells in the small intestine. Here, we used Caco2 cells to investigate whether FGFR-3 signaling can directly modulate expression of Paneth cell differentiation markers through its effects on TCF4/β-catenin or through other signaling pathways downstream of this receptor. Caco2 cells treated with FGFR-3 ligands or expressing FGFR-3(K650E), a constitutively active mutant, resulted in a significantly increased expression of genes characteristic of mature Paneth cells, including human α-defensins 5 and 6 (HD5 and HD6) and Paneth cell lysozyme, whereas enterocytic differentiation markers were reduced. Activation of FGFR-3 signaling sustained high levels of β-catenin mRNA expression, leading to increased TCF4/β-catenin-regulated transcriptional activity in Caco2 cells. Sustained activity of the TCF4/β-catenin pathway was required for the induction of Paneth cell markers. Activation of the MAPK pathway by FGFR-3 is also required for the induction of Paneth cell markers in addition to and independent of the effect of FGFR-3 on TCF4/β-catenin activity. These studies suggest that coordinate activation of multiple independent signaling pathways downstream of FGFR-3 is involved in regulation of Paneth cell differentiation.

Identification and characterization of an inhibitory fibroblast growth factor receptor 2 (FGFR2) molecule, up-regulated in an Apert Syndrome mouse model

AS (Apert syndrome) is a congenital disease composed of skeletal, visceral and neural abnormalities, caused by dominant-acting mutations in FGFR2 [FGF (fibroblast growth factor) receptor 2]. Multiple FGFR2 splice variants are generated through alternative splicing, including PTC (premature termination codon)-containing transcripts that are normally eliminated via the NMD (nonsense-mediated decay) pathway. We have discovered that a soluble truncated FGFR2 molecule encoded by a PTC-containing transcript is up-regulated and persists in tissues of an AS mouse model. We have termed this IIIa-TM as it arises from aberrant splicing of FGFR2 exon 7 (IIIa) into exon 10 [TM (transmembrane domain)]. IIIa-TM is glycosylated and can modulate the binding of FGF1 to FGFR2 molecules in BIAcore-binding assays. We also show that IIIa-TM can negatively regulate FGF signalling in vitro and in vivo. AS phenotypes are thought to result from gain-of-FGFR2 signalling, but our findings suggest that IIIa-TM can contribute to these through a loss-of-FGFR2 function mechanism. Moreover, our findings raise the interesting possibility that FGFR2 signalling may be a regulator of the NMD pathway.

Abstract 3589: Dovitinib (TKI258), a multikinase inhibitor of FGFR, PDGFR, and VEGFR tyrosine kinases, induces growth inhibition in endometrial carcinoma cells

Abstract Background: Endometrial carcinoma is the most common gynecological malignancy in the western world. Activating mutations of the fibroblast growth factor receptor 2 (FGFR2) have been described in 12-16% of endometrial cancers. Moreover, vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) and their receptors are involved in the neovascularization, invasiveness, and metastatic potential of endometrial cancer. Therefore, suppression of FGFR/VEGFR/PDGFR signaling by TKI258 may represent a novel approach for treatment of endometrial cancer. Experimental Design: The aims of this study were 1.) to assess the effect of TKI258 on tumor cell growth in two-dimensional (2D) and three-dimensional (3D) culture assays using a panel of 20 human endometrial cancer cell lines, 2.) to identify candidate molecular markers predicting sensitivity using baseline gene expression profiling and mutational analyses, and 3.) to determine the in vivo antineoplastic activity of TKI258 in endometrial cancer xenograft models. In addition, we screened 200 fresh frozen endometrial cancer specimens to comprehensively assess the distribution pattern of PI3K, PTEN, and FGFR mutations in endometrial cancer. Results: Concentration-dependent anti-proliferative effects of TKI285 using 2D assays were seen in all endometrial cancer cell lines tested, but varied significantly between individual cell lines (IC50 range: 0.42µM – 3.06 µM). The three most sensitive endometrial cancer cell lines demonstrated activating FGFR2 mutations (MFE296: N549K, IC50 0.42µM; AN3CA: N549K and K310R, IC50 0.50µM; MFE280: S252W, IC50 0.66µM). Assessment of TKI258 responses in 3D assays demonstrated similar results to those observed in 2D culture assays in that the 3 cell lines harboring FGFR2 mutations were the most sensitive to TKI258 achieving 100% growth inhibition at a concentration of 1µM. AN3CA and MFE296 endometrial cancer cells formed xenografts in nude mice and antitumor activity was studied in both models. Inhibition of p-FGFR, p-PDGFR, p-VEGFR-2, pAKT and p-ERK1/2 were observed. Comprehensive data on the pattern of PI3K, PTEN and FGFR mutations in endometrial cancer will be provided. Conclusion: TKI258 demonstrates significant antitumor activity in endometrial cancer cells with FGFR2 mutations. This study provides a strong rationale for the clinical evaluation of TKI258 in patients with endometrial cancer, specifically in those harboring FGFR2 mutations. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3589. doi:10.1158/1538-7445.AM2011-3589

FGFR3 Heterodimerization in Achondroplasia, the Most Common Form of Human Dwarfism

The G380R mutation in the transmembrane domain of fibroblast growth factor receptor 3 (FGFR3) causes achondroplasia, the most common form of human dwarfism. Achondroplasia is a heterozygous disorder, and thus the affected individuals express both wild-type and mutant FGFR3. Yet heterodimerization in achondroplasia has not been characterized thus far. To investigate the formation of FGFR3 heterodimers in cellular membranes, we designed an FGFR3 construct that lacks the kinase domain, and we monitored the formation of inactive heterodimers between this construct and wild-type and mutant FGFR3. The formation of the inactive heterodimers depleted the pool of full-length receptors capable of forming active homodimers and ultimately reduced their phosphorylation. By analyzing the effect of the truncated FGFR3 on full-length receptor phosphorylation, we demonstrated that FGFR3 WT/G380R heterodimers form with lower probability than wild-type FGFR3 homodimers at low ligand concentration. These results further our knowledge of FGFR3-associated bone disorders.

Probing Skeletal Dysplasias Caused by Mutations of FGFR3 Using Qi-FRET

Fibroblast growth factor receptor 3 (FGFR3) is a member of the receptor tyrosine kinase (RTK) family. FGFR3 is a single pass transmembrane protein and is involved in cell signaling, regulation, and proliferation. Signals are mediated via the lateral dimerization of the transmembrane spanning proteins and their interactions with extracellular ligands. It is important for these signaling pathways to be tightly regulated. Several mutations in FGFR3 are known to result in unregulated activation and/or disruption of proper cellular functions leading to pathogenesis. For example, single point mutations in FGFR3 are implicated in diseases such as achondroplasia, a form of dwarfism, and thanatophoric dysplasia, which is a lethal form of skeletal dysplasia. We are currently probing the interaction of mutant versions of FGFR3 to determine how these interactions change relative to that of the wild type FGFR3. These interactions are quantified via QI-FRET. In this approach, CHO cell-derived plasma membrane vesicles are prepared to mimic the native environment for the expressed FGFR3 constructs, which are linked to fluorescent proteins for direct visualization. Two important attributes of this approach over conventional whole-cell imaging are the low background noise and the strong intensity of the obtained vesicles. This results in the ability to fit the intensity profile with a Gaussian distribution and facilitate automated processing of images such that large numbers of vesicles with varying protein concentrations can be analyzed. From which, changes in interactions between wild type and mutant FGFR3 can be quantitatively determined.

Effect of the G346E Mutation on FGFR3 Activation

Fibroblast Growth Factor Receptor 3 (FGFR3) plays an important role in signal transduction. The disturbance of its activation leads to pathologies, including genetic disorders such as Achondroplasia. A point mutation in FGFR3, G346E, was found to cause this genetic disorder but the physical-chemical basis behind the pathology remains unknown. We hypothesize that the G346E mutation causes achondroplasia by affecting FGFR3 activation. To test this hypothesis, we investigate the effect of the G346E mutation on FGFR3 phosphorylation in the presence and absence of the ligand FGF1, using Western Blots. In particular, we investigate how the mutation changes the activation propensity of FGFR3 by fitting the Western blot data to a physical-chemical model describing an apparent equilibrium between inactive monomers and active dimers.

연골무형성증(Achondroplasia)환자에서 폐쇄성 수면무호흡 증후군의 수술적 치료 1예

Achondroplasia is the most common form of dwarfism. It is inherited in an autosomal dominant pattern, usually caused by an missense mutation of FGFR3 (fibroblast growth factor receptor 3). Clinical features of achondroplasia are well known and include skull enlargement with narrowing of skull base and foramen magnum. These features may lead to respiratory disturbances such as sleep apnea. In this study, the authors experienced a case of operative treatment of obstructive sleep apnea syndrome in achondroplasia patent, we report this case with a literature review. (J Clinical Otolaryngol 2010;21:265-269)

Beyond the closed suture in apert syndrome mouse models: evidence of primary effects of FGFR2 signaling on facial shape at birth.

Apert syndrome is a congenital disorder caused mainly by two neighboring mutations on fibroblast growth factor receptor 2 (FGFR2). Premature closure of the coronal suture is commonly considered the identifying and primary defect triggering or preceding the additional cranial malformations of Apert phenotype. Here we use two transgenic mouse models of Apert syndrome, Fgfr2(+/S252W) and Fgfr2(+/P253R), to explore variation in cranial phenotypes in newborn (P0) mice. Results show that the facial skeleton is the most affected region of the cranium. Coronal suture patency shows marked variation that is not strongly correlated with skull dysmorphology. The craniofacial effects of the FGFR2 mutations are similar, but Fgfr2(+/S252W) mutant mice display significantly more severe dysmorphology localized to the posterior palate. Our results demonstrate that coronal suture closure is neither the primary nor the sole locus of skull dysmorphology in these mouse models for Apert syndrome, but that the face is also primarily affected.

Physical Basis behind Achondroplasia, the Most Common Form of Human Dwarfism

Fibroblast growth factor receptor 3 (FGFR3) is a receptor tyrosine kinase that plays an important role in long bone development. The G380R mutation in FGFR3 transmembrane domain is known as the genetic cause for achondroplasia, the most common form of human dwarfism. Despite many studies, there is no consensus about the exact mechanism underlying the pathology. To gain further understanding into the physical basis behind the disorder, here we measure the activation of wild-type and mutant FGFR3 in mammalian cells using Western blots, and we analyze the activation within the frame of a physical-chemical model describing dimerization, ligand binding, and phosphorylation probabilities within the dimers. The data analysis presented here suggests that the mutation does not increase FGFR3 dimerization, as proposed previously. Instead, FGFR3 activity in achondroplasia is increased due to increased probability for phosphorylation of the unliganded mutant dimers. This finding has implications for the design of targeted molecular treatments for achondroplasia.

Fibroblast Growth Factor Receptor 2 and Its Role in Caudal Appendage and Craniosynostosis

Caudal appendage is a rare but reported finding seen in association with craniosynostosis. We report a newborn with caudal appendage secondary to sacrococcygeal eversion, a cloverleaf skull, choanal atresia, and a heterozygous mutation of Y375C in the juxtamembrane domain (exon 11) of fibroblast growth factor receptor 2 (FGFR2). Further support of this association are 22 other cases of craniosynostosis with caudal appendage or sacrococcygeal eversion in the literature. Of these, 19 had detectable mutations in FGFR2; 5, the same mutation; and 5, a similar substitution of cysteine for serine. We hypothesize that the association of craniosynostosis and caudal appendage is due to abnormal expression of FGFR2 in the tail bud of a developing embryo based on animal models. Our case and those reported in the literature suggest that in patients with caudal appendage and craniosynostosis, FGRF2 analysis should include regions outside the commonly tested exons 8 and 10, particularly the juxtamembrane domain.

Delayed bone age due to a dual effect of FGFR3 mutation in Achondroplasia

Achondroplasia (ACH), the most common form of human dwarfism is caused by a mutation in the Fibroblast Growth Factor Receptor 3 (FGFR3) gene, resulting in constitutive activation of the receptor. Typical radiological features include shortening of the tubular bones and macrocephaly, due to disruption of endochondral ossification. Consequently, FGFR3 has been described as a negative regulator of bone growth. Studying a large cohort of ACH patients, a delay in bone age was observed shortly after birth (for boys p = 2.6 × 10 −9 and for girls p = 1.2 × 10 −8). This delay was no longer apparent during adolescence. In order to gain further insight into bone formation, bone development was studied in a murine model of chondrodysplasia ( Fgfr3 Y367C/+ ) from birth to 6 weeks of age. Delayed bone age was also observed in Fgfr3 Y367C/+ mice at 1 week of age followed by an accelerated secondary ossification center formation. A low level of chondrocyte proliferation was observed in the normal growth plate at birth, which increased with bone growth. In the pathological condition, a significantly high level of proliferative cells was present at birth, but exhibited a transient decrease only to rise again subsequently. Histological and in situ analyses suggested the altered endochondral ossification process may result from delayed chondrocyte differentiation, disruption of vascularization and osteoblast invasion of the femur. All these data provide evidence that FGFR3 regulates normal chondrocyte proliferation and differentiation during bone growth and suggest that constitutive activation of the receptor disrupts both processes. Therefore, the consequences of FGFR3 activation on the physiological process of bone development appear to be dependent on spatial and temporal occurrence. In conclusion, these observations support the notion that FGFR3 has a dual effect, as both a negative and a positive regulator of the endochondral ossification process during post-natal bone development.

Osteoglophonic dysplasia: A ‘common’ mutation in a rare disease

Osteoglophonic dysplasia or osteoglophonic dwarfism (OGD, OMIM#166250) is a rare skeletal disorder caused by mutations in fibroblast growth factor receptor 1 (FGFR1)(1,2). It is inherited as an autosomal dominant trait. OGD is characterized by gross stunting of stature associated with profound craniofacial abnormalities (3,4). We presented a 12-year old Chinese girl diagnosed with OGD. Her parents and other siblings are otherwise normal. This patient has short stature i.e. her height was 102 centimetres, which was well below the 3rd percentile for her age and corresponded to the 50th percentile for a 4 year-old girl. She was dysmorphic as she had mandibular prognathism, midfacial hypoplasia, hypertelorism, right eye hypertropia, an everted nose with a depressed nasal bridge. [Figure 1] She also had brachydactyly with a single palmar crease and there was fusion of the proximal interphalangeal joints in all four limbs. Her skeletal survey showed rhizomelic shortening of the humerus and femur bilaterally, short metacarpals with fusion of the proximal and middle phalanx, enlargement of the metaphysis of the distal femur bilaterally and anterior beaking of her lumbar vertebral body. Her skull was of abnormal configuration with presence of craniosynostosis, small midface and prognathic mandible. Another striking feature was she presented with giant cell lesions of her right maxilla and left mandible. Figure 1 Facial features showing mandibular prognathism, midfacial hypoplasia and everted nose with a depressed nasal bridge Blood investigations revealed normal serum calcium and phosphate (2.22 mmol /L, 1.33 mmol/L respectively), normal alkaline phosphatase at 167 U/L [normal 130-560 U/L], normal parathyroid hormone level, a 7.57 pmol/L and fibroblast growth factor 23 (FGF23) at 74 pg/ml (this value was at the upper end of normal for adults as to date, there is no relevant data for children). Mutation analysis of the FGFR1 gene revealed a heterozygous mutation c.1141C>T in exon 10 [based on the FGFR1 transcript variant 1 mRNA ({type:entrez-nucleotide,attrs:{text:NM_023110,term_id:105990521,term_text:NM_023110}}NM_023110)]. [Figure 2] This mutation results in a cysteine-to-arginine change (Cys381Arg) in the FGFR1 transmembrane domain (1). Figure 2 Heterozygous mutation c.1141C>T of FGFR1 in exon 10 The FGFRs are part of a tyrosine kinase receptor family; they comprise an extracellular ligand-binding domain, a single transmembrane domain, and an intracellular tyrosine kinase region (2). FGFR1 and FGFR2 mutations cause syndromes involving craniosynostosis whereas FGFR3 mutations are associated with dwarfing syndromes such as achondroplasia and hypochondroplastic dwarfism (1). OGD is caused by activating mutations in a highly conserved domain of FGFR1 and shares characteristics with both the craniosynostosis and dwarfing syndromes (1). In our patient, molecular analysis of FGFR1 revealed a missense mutation (c.1141C>T) in exon 10 resulting in a substitution of cysteine 381 to arginine. This substitution creates an unpaired cysteine residue and may disrupt disulfide bonding required for proper dimerization of FGFR1. To date, mutations have been reported in only 6 other OGD patients (1,2). Our patient’s mutation has been reported in two of these 6 patients, which indicates that Cys381Arg may be a ‘common’ mutation in this rare disorder (1,2). One of the two reported patients was the index case who was first described by Beighton (3); the other one was patient 4, described in 2005 by White et al (1). Both these patients showed similar radiological features to ours, including metaphyseal lucencies affecting the long bones with anterior beaking of the vertebral bodies. The other similarity was their serum phosphate and FGF23 levels were at normal levels. However, our patient displayed pathological features of giant cell lesions in her maxilla and mandible. This lesion was also shown in one of the six previously reported OGD cases but, with different type of mutation (N330I).

NF449 Is a Novel Inhibitor of Fibroblast Growth Factor Receptor 3 (FGFR3) Signaling Active in Chondrocytes and Multiple Myeloma Cells

The FGFR3 receptor tyrosine kinase represents an attractive target for therapy due to its role in several human disorders, including skeletal dysplasias, multiple myeloma, and cervical and bladder carcinomas. By using molecular library screening, we identified a compound named NF449 with inhibitory activity toward FGFR3 signaling. In cultured chondrocytes and murine limb organ culture, NF449 rescued FGFR3-mediated extracellular matrix loss and growth inhibition, which represent two major cellular phenotypes of aberrant FGFR3 signaling in cartilage. Similarly, NF449 antagonized FGFR3 action in the multiple myeloma cell lines OPM2 and KMS11, as evidenced by NF449-mediated reversal of ERK MAPK activation and transcript accumulation of CCL3 and CCL4 chemokines, both of which are induced by FGFR3 activation. In cell-free kinase assays, NF449 inhibited the kinase activity of both wild type and a disease-associated FGFR3 mutant (K650E) in a fashion that appeared non-competitive with ATP. Our data identify NF449 as a novel antagonist of FGFR3 signaling, useful for FGFR3 inhibition alone or in combination with inhibitors that target the ATP binding site.

Molecular Grade (FGFR3/MIB-1) and EORTC Risk Scores Are Predictive in Primary Non–Muscle-Invasive Bladder Cancer

BackgroundThe European Organization for Research and Treatment of Cancer (EORTC) risk scores are not validated in an independent patient population. Molecular grade (mG) based on fibroblast growth factor receptor 3 (FGFR3) gene mutation status and MIB-1 expression was proposed as an alternative to pathologic grade in bladder cancer (BCa) [1]. ObjectiveTo validate the EORTC risk score and to determine its relation to mG in a series with long-term follow-up as well as to determine reproducibility of pathologic grade and mG. Design, setting, and participantsIn this multicenter study, we included 230 patients with primary non–muscle-invasive BCa (NMIBC). MeasurementsFour uropathologists reviewed the slides. FGFR3 mutation status was examined by two assays. MIB-1 was assessed by immunohistochemistry. The EORTC risk scores for recurrence and progression were determined. Multivariable analyses were used to find prognostic factors. Results and limitationsMedian follow-up was 8.62 yr (interquartile range: 6.6–11.8). FGFR3 mutations were significantly related to favorable disease parameters, whereas altered MIB-1 was frequently seen with pT1, high grade, and high EORTC risk scores. EORTC risk scores were significant in multivariable analyses for recurrence and progression. In multivariable analyses for progression and disease-specific survival, the mG had independent significance. The addition of mG to the multivariable model for progression increased the predictive accuracy from 74.9% to 81.7% (p<0.001; Mantel-Haenszel test). The mG (89%) was more reproducible than the pathologic grade (41–74%). ConclusionsWe validated the EORTC risk scores for primary NMIBC in a clinical and biomarker setting. Next to EORTC risk score, mG proved highly reproducible and predictive. Our long-term results justify an independent prospective analysis of mG and EORTC risk scores.