Progress in managing children with achondroplasia.

INTRODUCTION: Achondroplasia is a heritable disorder of the skeleton that affects approximately 300,000 individuals worldwide. Until recently, treatment for this condition has been purely symptomatic. Efficacious treatment options for children are now approved or are in clinical trials. AREAS COVERED: This review discusses key advances in the therapeutic management of children with achondroplasia, including vosoritide, the first approved drug, and other emerging precision therapies. These include navepegritide, a long-acting form of C-type natriuretic peptide, and infigratinib, a tyrosine kinase receptor inhibitor, summarizing trial outcomes to date. EXPERT OPINION: The advent of the first approved precision therapy for achondroplasia in vosoritide has been a paradigm shifting advance for children affected by this condition. In addition to changing their natural growth history, it is hoped that it will decrease their medical complications and enhance functionality. These new treatment options highlight the importance of prompt prenatal identification and subsequent testing of a suspected fetus with achondroplasia and counseling of families. It is hoped that, in the near future, families will have the option to consider a range of effective targeted therapies that best suit their child with achondroplasia, starting from birth should they choose.

Promising horizons in achondroplasia along with the development of new drugs.

Achondroplasia (ACH) is a representative skeletal disorder characterized by rhizomelic shortened limbs and short stature. ACH is classified as belonging to the fibroblast growth factor receptor 3 (FGFR3) group. The downstream signal transduction of FGFR3 consists of STAT1 and RAS/RAF/MEK/ERK pathways. The mutant FGFR3 found in ACH is continuously phosphorylated and activates downstream signals, resulting in abnormal proliferation and differentiation of chondrocytes in the growth plate and cranial base synchondrosis. A patient registry has been developed and has contributed to revealing the natural history of ACH patients. Concerning the short stature, the adult height of ACH patients ranges between 126.7-135.2 cm for men and 119.9-125.5 cm for women in many countries. Along with severe short stature, foramen magnum stenosis and spinal canal stenosis are major complications: the former leads to sleep apnea, breathing disorders, myelopathy, hydrocephalus, and sudden death, and the latter causes pain in the extremities, numbness, muscle weakness, movement disorders, intermittent claudication, and bladder-rectal disorders. Growth hormone treatment is available for ACH only in Japan. However, the effect of the treatment on adult height is not satisfactory. Recently, the neutral endopeptidase-resistant CNP analogue vosoritide has been approved as a new drug for ACH. Additionally in development are a tyrosine kinase inhibitor, a soluble FGFR3, an antibody against FGFR3, meclizine, and the FGF2-aptamer. New drugs will bring a brighter future for patients with ACH.

Significance of the FGFR3 mutation in Chinese patients with bladder cancer.

Background: Bladder cancer (BC) is the 10th most common malignancy worldwide. The high recurrence rates of BC lead to significant treatment challenges. With the development of molecular biology techniques, research has shown that gene abnormalities are closely related to the occurrence and development of BC. This study analyzed the detection results of gene mutations in the tissue samples of BC patients and explored the relationship between fibroblast growth factor receptor 3 (FGFR3) and the prognosis and recurrence of BC. Methods: This study examined 82 Chinese patients with BC. Of these patients, 34 underwent radical cystectomy (RC), and 48 underwent transurethral resection with intravesical instillation. In addition, multi-gene panel targeted next-generation sequencing (NGS) of the samples was performed. Results: The mutational spectra revealed that C > T was the most common base substitution. Single nucleotide polymorphism (SNP) and deletion (DEL) were the common variant types in our cohort. The top 10 mutant genes were ROS1 (37%), PIK3CA (35%), FGFR3 (34%), BRAF (34%), ERBB2 (32%), ALK (27%), RET (27%), NTRK1 (24%), MET (23%), and EGFR (18%). FGFR3 mutations were detected more frequently in non-muscle-invasive bladder cancer (stages 0a, I) patients than in muscle-invasive bladder cancer (stage II, III, and IV) patients. The top 3 altered types of FGFR3 were p.Ser249Cys, p.Tyr375Cys, and p.Arg248Cys. Conclusions: This study examined the mutated types and frequency of FGFR3 and the prognosis of Chinese BC patients with FGFR mutations. We hope that our findings will enable clinical individualization strategies for BC patients to be optimized.

Large, Nested Variant of Urothelial Carcinoma Is Enriched with Activating Mutations in Fibroblast Growth Factor Receptor-3 among Other Targetable Mutations.

The large, nested variant of urothelial carcinoma (LNVUC) is characterized by bland histomorphology mimicking that of benign von Brunn nests. In the current study, we aimed to investigate the Fibroblast Growth Factor Receptor-3 (FGFR-3) activation and missense mutation in 38 cases, including 6 cases diagnosed with LNVUC and 32 with metastatic invasive urothelial carcinoma (UC). Initially, six formalin-fixed paraffin-embedded (FFPE) tissue samples of the LNVUC were subjected to whole-exome sequencing (WES), and then we performed targeted sequencing on 32 cases of metastatic invasive UC of various morphological subtypes, which were interrogated for the FGFR3. Our results revealed 3/6 (50%) LNVUC cases evaluated by WES in our study showed an activating mutation in FGFR-3, 33% showed an activating mutation in PIK3CA, and 17% showed activating mutation in GNAS or MRE11. Additionally, 33% of cases showed a truncating mutation in CDKN1B. All LNVUC in our study that harbored the FGFR-3 mutation showed additional activating or truncating mutations in other genes. Overall, 6/32 (18.75%) cases of random metastatic invasive UC showed missense mutations of the FGFR-3 gene. The LNVUC variant showed the higher incidence of FGFR-3 mutations compared to other types of mutations. Additionally, all LNVUC cases show additional activating or truncating mutations in other genes, thus being amenable to novel targeted therapy.

Frequent Telomerase Reverse Transcriptase Promoter and Fibroblast Growth Factor Receptor 3 Mutations Support the Precursor Nature of Papillary Urothelial Hyperplasia of the Urinary Bladder.

The precursor nature of papillary urothelial hyperplasia of the urinary bladder is uncertain. In this study, we investigated the telomerase reverse transcriptase (TERT) promoter and fibroblast growth factor receptor 3 (FGFR3) mutations in 82 patients with papillary urothelial hyperplasia lesions. Thirty-eight patients presented with papillary urothelial hyperplasia and concurrent noninvasive papillary urothelial carcinoma, and 44 patients presented with de novo papillary urothelial hyperplasia. The prevalence of the TERT promoter and FGFR3 mutations is compared between de novo papillary urothelial hyperplasia and those with concurrent papillary urothelial carcinoma. Mutational concordance between papillary urothelial hyperplasia and concurrent carcinoma was also compared. The TERT promoter mutations were detected in 44% (36/82) of papillary urothelial hyperplasia, including 23 (23/38, 61%) papillary urothelial hyperplasia with urothelial carcinoma and 13 (13/44, 29%) de novo papillary urothelial hyperplasia. The overall concordance of TERT promoter mutation status between papillary urothelial hyperplasia and concurrent urothelial carcinoma was 76%. The overall FGFR3 mutation rate of papillary urothelial hyperplasia was 23% (19/82). FGFR3 mutations were detected in 11 patients with papillary urothelial hyperplasia and concurrent urothelial carcinoma (11/38, 29%) and 8 patients with de novo papillary urothelial hyperplasia (8/44, 18%). Identical FGFR3 mutation status was detected in both papillary urothelial hyperplasia and urothelial carcinoma components in all 11 patients with FGFR3 mutations. Our findings provide strong evidence of a genetic association between papillary urothelial hyperplasia and urothelial carcinoma. High frequency of TERT promoter and FGFR3 mutations suggests the precursor role of papillary urothelial hyperplasia in urothelial carcinogenesis.

Lifetime impact of achondroplasia study in Europe (LIAISE): findings from a multinational observational study.

BACKGROUND: Achondroplasia, caused by a pathogenic variant in the fibroblast growth factor receptor 3 gene, is the most common skeletal dysplasia. The Lifetime Impact of Achondroplasia Study in Europe (LIAISE; NCT03449368) aimed to quantify the burden of achondroplasia among individuals across a broad range of ages, including adults. METHODS: Demographic, clinical and healthcare resource use data were collected from medical records of achondroplasia patients enrolled in 13 sites across six European countries in this retrospective, observational study. Descriptive statistics or event rates per 100 person-years were calculated and compared across age groups as well as by history of limb lengthening. Patient-reported outcomes (quality of life [QoL], pain, functional independence, work productivity and activity impairments) were evaluated using questionnaires at the time of enrolment. An exploratory analysis investigated correlations between height (z-score or centimetres) and patient-reported outcomes. RESULTS: Overall, 186 study patients were included, with a mean age of 21.7 ± 17.3 years (range 5.0-84.4). At least one complication or surgery was reported for 94.6% and 72.0% of patients, respectively, at a rate of 66.6 and 21.5 events per 100 person-years. Diverse medical and surgical complications were reported for all ages in a bimodal distribution, occurring more frequently in the youngest and oldest age groups. A total of 40 patients had previously undergone limb lengthening (capped at 20% per the study protocol). The most frequent surgery types varied by age, in line with complication profiles. Healthcare resource use was high across all age groups, especially among the youngest and oldest individuals, and did not differ substantially according to history of limb lengthening. Compared to general population values, patients reported impaired QoL particularly for physical functioning domains. In addition, patients reported difficulty carrying out daily activities independently and pain starting in childhood. Patient height correlated with multiple patient-reported outcomes. CONCLUSIONS: The findings of this study suggest that, across an individual's lifetime, achondroplasia is associated with multisystem complications, reduced QoL and functionality, and increased pain. These results highlight the large amount of healthcare resources that individuals with achondroplasia require throughout their lifespans and provide novel insights into current achondroplasia management practices across Europe. Trial registration ClinicalTrials.gov, NCT03449368, Submitted 14 December 2017 - prospectively registered, https://clinicaltrials.gov/ct2/show/record/NCT03449368.

High expression of FGFR3 predicts a better prognosis for patients with non-small cell lung cancer in a Chinese population.

Background: This study sought to examine the expression and mutation status of fibroblast growth factor receptor 3 (FGFR3) in non-small cell lung cancer (NSCLC) tissues and explore the prognostic potential of FGFR3 in NSCLC. Methods: Immunohistochemistry (IHC) was used to evaluate the FGFR3 protein expression of 116 NSCLC tissues. Sanger sequencing was used to examine the mutation status of exons 7, 10, and 15 in FGFR3. A Kaplan­Meier survival analysis was conducted to evaluate the association between the expression level of FGFR3 and the overall survival (OS) and disease-free survival (DFS) of NSCLC patients. Univariate and multivariate Cox analyses were conducted to examine the association between the risk score and clinical features. Results: FGFR3 was immunoreactive in 26 of the 86 NSCLC cases. Further, FGFR3 was positively expressed in 84.6% of the lung adenocarcinoma (AC) cases and 15.4% of the lung squamous cell carcinoma (SCC) cases. FGFR3 mutations were detected in 2 NSCLC patients (2/72, 2.8%), who both harbored the T450M mutation, a novel mutation in exon 10 of FGFR3. In NSCLC, a high expression of FGFR3 was positively correlated with gender, smoking, histology type, T stage, and the epidermal growth factor receptor (EGFR) mutation (P<0.05). FGFR3 expression was also correlated with better OS and DFS. The multivariate analysis revealed that FGFR3 served as an independent prognostic factor (P=0.024) for the OS of NSCLC patients. Conclusions: This study showed that FGFR3 was highly expressed in NSCLC tissues, and the frequency rate for the FGFR3 mutation at T450 M in NSCLC tissues was low. The survival analysis suggested that FGFR3 may be a useful prognostic biomarker in NSCLC.

Emerging therapies for Achondroplasia: changing the rules of the game.

INTRODUCTION: Achondroplasia is the most common genetic cause of disproportionate short stature, affecting over 360,000 individuals. Serious complications contributing to significant morbidity in affected individuals include cranio-cervical junction compression and obstructive sleep apnea. Current clinically available treatments are predominantly symptomatic and associated with variable outcomes. We summarize the new precision investigational products that are currently in Phase 2 and Phase 3 clinical trials for the treatment of individuals with achondroplasia. AREAS COVERED: Fibroblast growth factor receptor 3 (FGFR3), a membrane-spanning tyrosine kinase receptor, binds various fibroblast growth factors (FGF) to regulate the normal process of endochondral bone growth. Gain of FGFR3 function in individuals with achondroplasia results in inhibition of normal endochondral ossification. A greater understanding of these molecular pathways through animal models has led to the development of several targeted therapies being tested in children, which we discuss in this review. EXPERT OPINION: The last decade has been game-changing in terms of new precision therapies for children with achondroplasia that have the potential to fundamentally change the natural history of this condition. The next decade will see how these therapies compare, if they might be used in combination, and evaluate the balance of their long-term benefits and harms.

Lifetime impact of achondroplasia: Current evidence and perspectives on the natural history.

Achondroplasia, the most common form of disproportionate short stature, is caused by a variant in the fibroblast growth factor receptor 3 (FGFR3) gene. Advances in drug treatment for achondroplasia have underscored the need to better understand the natural history of this condition. This article provides a critical review and discussion of the natural history of achondroplasia based on current literature evidence and the perspectives of clinicians with extensive knowledge and practical experience in managing individuals with this diagnosis. This review draws evidence from recent and ongoing longitudinal natural history studies, supplemented with relevant cross-sectional studies where longitudinal research is lacking, to summarize the current knowledge on the nature, incidence, chronology, and interrelationships of achondroplasia-related comorbidities across the lifespan. When possible, data related to adults are presented separately from data specific to children and adolescents. Gaps in knowledge regarding clinical care are identified and areas for future research are recommended and discussed.

Clinical characterisation of sensory neuropathy with anti-FGFR3 autoantibodies.

OBJECTIVE: Sensory neuropathies (SNs) are often classified as idiopathic even if immunological mechanisms can be suspected. Antibodies against the intracellular domain of the fibroblast growth factor receptor 3 (FGFR3) possibly identify a subgroup of SN affecting mostly the dorsal root ganglion (DRG). The aim of this study was to identify the frequency of anti-FGFR3 antibodies and the associated clinical pattern in a large cohort of patients with SN. METHODS: A prospective, multicentric, European and Brazilian study included adults with pure SN. Serum anti-FGRF3 antibodies were analysed by ELISA. Detailed clinical and paraclinical data were collected for each anti-FGFR3-positive patient and as control for anti-FGFR3-negative patients from the same centres ('center-matched'). RESULTS: Sixty-five patients out of 426 (15%) had anti-FGFR3 antibodies, which were the only identified autoimmune markers in 43 patients (66%). The neuropathy was non-length dependent in 89% and classified as sensory neuronopathy in 64%, non-length-dependent small fibre neuropathy in 17% and other neuropathy in 19%. Specific clinical features occurred after 5-6 years of evolution including frequent paresthesia, predominant clinical and electrophysiological involvement of the lower limbs, and a less frequent mixed large and small fibre involvement. Brazilians had a higher frequency of anti-FGFR3 antibodies than Europeans (36% vs 13%, p<0.001), and a more frequent asymmetrical distribution of symptoms (OR 169, 95% CI 3.4 to 8424). CONCLUSIONS: Anti-FGFR3 antibodies occur in a subgroup of SN probably predominantly affecting the DRG. Differences between Europeans and Brazilians could suggest involvement of genetic or environmental factors.

The correlation between adiponectin and FGF9 in depression disorder.

Adiponectin (ADPN) and fibroblast growth factor 9 (FGF9) has been reported as anti-depressive and pro-depressive factor, respectively. However, it is unknown whether there is directly interaction between ADPN and FGF9 in depression. The present study aims to investigate the correlation between ADPN and FGF9 in depression disorder. Firstly, the decreased level of ADPN and the increased level of FGF9 in plasma of depressive patients compared with non-depressive subjects were observed. Furthermore, these is a significant negative correlation between the ratio of ADPN to FGF9 and the total score of Hamilton Depression Scale in total investigated subjects. The similar changes of ADPN and FGF9 were also observed in elder adiponectin gene knockout (Adipo-/-) mice with an increasing trend to depressive-like behaviors. Secondly, the decreasing level of ADPN and increasing level of FGF9 in plasma and hippocampus tissues were observed in chronic unpredictable mild stress (CUMS)-induced depression in ICR mice with significant depressive-like behaviors and hippocampus damage, which attenuated by injection of recombinant ADPN or FGF9 antibody into lateral ventricle. In Adipo-/- mice, injection of FGF9 antibody into lateral ventricle also attenuated CUMS-induced depressivelike behaviors. The protein expression of FGF receptor 3 (FGFR3), the main receptor of FGF9, was significantly down-regulated in hippocampus tissues of CUMS-treated mice, which could be attenuated by treatment with either recombinant ADPN or anti-FGF9. In summary, the present results suggest that ADPN maybe a key negative regulator of FGF9/FGFR3 in depressive disorder and the dysfunction of ADPN-FGF9 pathway plays a key role in stress-induced depression.

Activated FGFR3 prevents subchondral bone sclerosis during the development of osteoarthritis in transgenic mice with achondroplasia.

The purpose of this study is to investigate the morphometric changes of the subchondral bone during the development of osteoarthritis (OA) in transgenic mice with achondroplasia (Fgfr3ach ) carrying a heterozygous gain-of-function mutation in Fgfr3. Two OA models (spontaneously developed with age: The aging model, and surgically induced by destabilization of the medial meniscus: The DMM model) were established. Articular cartilage, epiphysis, and metaphysis of the knee joint were histologically and morphometrically compared between wild-type mice, and Fgfr3ach mice in both OA models. Articular cartilage degeneration was scored according to the Osteoarthritis Research Society International (OARSI) scoring system. Several morphometric parameters including bone mineral density (BMD), bone volume/tissue volume (BV/TV), trabecular bone thickness (Tb.Th), and subchondral bone thickness in the medial tibial plateau (MTP) (Sb.Th med) were quantified by micro-computed tomography (CT). In the aging model, although there were no significant differences in the OARSI score between wild-type mice and Fgfr3ach mice, Sb.Th med and Tb.Th in the epiphysis significantly increased in wild-type mice. In the DMM model, the OARSI score of the medial compartment was significantly lower in Fgfr3ach mice than in wild-type mice. BMD, BV/TV, and Tb.Th in the epiphysis increased in wild-type mice and unchanged in Fgfr3ach mice, and the Sb.Th med was significantly larger in wild-type mice after surgery. Subchondral sclerosis, which preceded the cartilage degeneration, was inhibited in Fgfr3ach mice. Activated FGFR3 signaling prevented sclerotic changes of the subchondral bone and subsequent cartilage degeneration. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:300-308, 2018.

Identification of a novel mutation in the FGFR3 gene in a Chinese family with Hypochondroplasia.

BACKGROUND: Hypochondroplasia (HCH; OMIM 146000) is a common autosomal dominant skeletal dysplasia characterized by disproportionate short stature, short extremities, relative macrocephaly, and lumbar lordosis. Because of its clinical and genetic heterogeneity, gene mutational analysis is particularly important in diagnosis and the phenotypes may be ameliorated if diagnosed early. MATERIALS AND METHODS: In this study, we examined a Chinese family with HCH, performed an inductive analysis of their clinical features and radiographic results, and applied targeted exome sequencing (TES) technology to perform a molecular diagnosis. RESULTS: The proband and his mother all presented disproportionate short stature, short, stubby extremities, unchanged interpedicular distances from L1-L5, and short iliac bones, with a 'fish mouth-shaped' sciatic notch. The mother received induced abortion recently because an ultrasound showed short femur length of her fetus at 24-week gestation. Eventually, a novel heterozygous mutation (c.1145G>A) in FGFR3 was identified by TES in the proband, his mother, and her fetus; this causes the substitution of glycine with aspartic acid in codon 382. CONCLUSIONS: In this study, we diagnosed a Chinese pedigree with HCH based on clinical data, radiographic features, and genetic testing results. Our results extend the genetic mutation spectrum of FGFR3 and demonstrate that TES is an effective method for the diagnosis of skeletal dysplasia in clinical practices.

Molecular therapeutic strategies for FGFR3 gene-related skeletal dysplasia.

The FGFR3 gene encodes fibroblast growth factor receptor 3 protein, a negative regulator of chondrogenesis. Gain-of-function mutations result in constitutively activated FGFR3, leading to aberrant signal transduction, and accounting for inhibition of chondrocyte proliferation and differentiation. Generally, these pathogenic mutations maintain FGFR3 in an active state and cause diverse phenotypes in patients with skeletal dysplasia. For decades, studies have revealed the molecular mechanisms of constitutively activated FGFR3 and relevant therapeutic strategies. By modulating the FGFR3-induced signalling pathway with methods such as blocking binding between ligands and receptors, blocking tyrosine kinase activities, or antagonising the FGFR3 downstream signalling pathway, these strategies offer the possibility to ameliorate FGFR3 gene-related skeletal dysplasia phenotypes. In this review, we describe the mechanisms of potential therapeutic targets and underlying regulators and then systematically review molecular therapeutic strategies for FGFR3 gene-related skeletal dysplasia based on current knowledge.

Overexpression of miR-100 inhibits growth of osteosarcoma through FGFR3.

Osteosarcoma (OS) is a prevalent, fast growing cancer. Identification of molecular regulation of OS growth may result in development of a novel therapy. Previous studies have highlighted a role of microRNAs (miRNAs) in the regulation of the carcinogenesis of OS, whereas the underlying mechanisms are not completely understood. Moreover, a role of miR-100 in the growth control of OS is not clear. Here we reported significantly higher levels of fibroblast growth factor receptor 3 (FGFR3) and significantly lower levels of miR-100 in the OS specimen, compared to those in the paired normal bone tissues. Bioinformatics analysis and luciferase reporter assay suggest that miR-100 binds to the 3'UTR of FGFR3 mRNA to prevent its translation. To prove it, we modified miR-100 levels in OS cells. We found that overexpression of miR-100 in OS cells decreased FGFR3 protein levels, whereas inhibition of miR-100 increased FGFR3 protein levels, without affecting FGFR3 transcripts. Moreover, overexpression of miR-100 suppressed the OS growth in vitro and in vivo, while inhibition of miR-100 significantly increased OS growth. Taken together, our data demonstrate that miR-100 may inhibit the growth of OS through FGFR3.

Increased first-trimester nuchal translucency associated with thanatophoric dysplasia type 1.

Thanatophoric dysplasia (TD) is the most frequent form of lethal skeletal dysplasia. Prenatal diagnosis is commonly accomplished in the second-trimester scan, but occasionally TD is found to be associated with increased nuchal translucency (NT) at first-trimester screening for aneuploidies. TD may not be clearly distinguished from the other skeletal dysplasias. A definite diagnosis can be established by molecular genetic analysis to find out the abnormal mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. We reported a case of TD type 1 detected by first-trimester NT measurement, and confirmed by molecular analysis of FGFR3 gene using high-resolution melting analysis.

Prevalence of Mutations in the FGFR3 Gene in Individuals with Idiopathic Short Stature.

FGFR3 (fibroblast growth factor receptor 3) is a gene responsible for the most common form of osteodysplasia, achondroplasia, which results in extreme short stature. An allelic disorder, hypochondroplasia, however, presents with a much milder phenotype and is sometimes indistinguishable from idiopathic short stature. In this study, in order to test the possibility of the mildest end of hypochondroplasia being labeled as idiopathic short stature and the possibility of polymorphism of FGFR3 acting as one of the stature genes of normal individuals, we examined the prevalence of sequence alterations of the FGFR3 gene among individuals diagnosed clinically with idiopathic short stature. Sequencing analysis of all exons of the FGFR3 gene on 54 individuals with idiopathic short stature did not reveal any sequence variations related to the stature of the individuals. These results suggest that hidden hypochondroplasia among idiopathic short stature individuals is not a common occurrence and the contribution of polymorphism of the FGFR3 gene as a determinant of stature in normal individuals is small if any.