FGF23

Gene Summary

Gene:FGF23; fibroblast growth factor 23
Aliases: ADHR, FGFN, HYPF, HPDR2, PHPTC
Location:12p13.3
Summary:This gene encodes a member of the fibroblast growth factor family of proteins, which possess broad mitogenic and cell survival activities and are involved in a variety of biological processes. The product of this gene regulates phosphate homeostasis and transport in the kidney. The full-length, functional protein may be deactivated via cleavage into N-terminal and C-terminal chains. Mutation of this cleavage site causes autosomal dominant hypophosphatemic rickets (ADHR). Mutations in this gene are also associated with hyperphosphatemic familial tumoral calcinosis (HFTC). [provided by RefSeq, Feb 2013]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:fibroblast growth factor 23
HPRD
Source:NCBIAccessed: 27 August, 2015

Ontology:

What does this gene/protein do?
Show (19)
Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 27 August 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Glucuronidase
  • ras Proteins
  • Chromosome 12
  • Family
  • Amino Acid Substitution
  • Phosphates
  • Skin Cancer
  • Vitamin D
  • Hypophosphatemia, Familial
  • Signal Transduction
  • Republic of Korea
  • Base Sequence
  • Tumor Suppressor Proteins
  • Tumor Markers
  • DNA Mutational Analysis
  • Cancer Gene Expression Regulation
  • Nevus, Pigmented
  • Adolescents
  • Amino Acid Sequence
  • Pedigree
  • Hypophosphatemia
  • Sequence Alignment
  • Thymus Neoplasms
  • RTPCR
  • Infant
  • Neoplasms, Connective Tissue
  • Fibroblast Growth Factors
  • Serine
  • Calcinosis
  • Prostate Cancer
  • Thymoma and Thymic Carcinoma
  • Survival Rate
  • Osteomalacia
  • Mutation
  • Transfection
  • Zygote
  • Structural Homology, Protein
  • Single Nucleotide Polymorphism
  • Molecular Sequence Data
Tag cloud generated 27 August, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: FGF23 (cancer-related)

Lee JC, Jeng YM, Su SY, et al.
Identification of a novel FN1-FGFR1 genetic fusion as a frequent event in phosphaturic mesenchymal tumour.
J Pathol. 2015; 235(4):539-45 [PubMed] Related Publications
Phosphaturic mesenchymal tumours (PMTs) are uncommon soft tissue and bone tumours that typically cause hypophosphataemia and tumour-induced osteomalacia (TIO) through secretion of phosphatonins including fibroblast growth factor 23 (FGF23). PMT has recently been accepted by the World Health Organization as a formal tumour entity. The genetic basis and oncogenic pathways underlying its tumourigenesis remain obscure. In this study, we identified a novel FN1-FGFR1 fusion gene in three out of four PMTs by next-generation RNA sequencing. The fusion transcripts and proteins were subsequently confirmed with RT-PCR and western blotting. Fluorescence in situ hybridization analysis showed six cases with FN1-FGFR1 fusion out of an additional 11 PMTs. Overall, nine out of 15 PMTs (60%) harboured this fusion. The FN1 gene possibly provides its constitutively active promoter and the encoded protein's oligomerization domains to overexpress and facilitate the activation of the FGFR1 kinase domain. Interestingly, unlike the prototypical leukaemia-inducing FGFR1 fusion genes, which are ligand-independent, the FN1-FGFR1 chimeric protein was predicted to preserve its ligand-binding domains, suggesting an advantage of the presence of its ligands (such as FGF23 secreted at high levels by the tumour) in the activation of the chimeric receptor tyrosine kinase, thus effecting an autocrine or a paracrine mechanism of tumourigenesis.

Fukumoto S
Anti-fibroblast growth factor 23 antibody therapy.
Curr Opin Nephrol Hypertens. 2014; 23(4):346-51 [PubMed] Related Publications
PURPOSE OF REVIEW: The review is intended to provide an update on the expanding knowledge regarding diseases caused by the excess actions of fibroblast growth factor 23 (FGF23) and also on the new therapeutic measures for these diseases, with an emphasis on the anti-FGF23 antibody.
RECENT FINDINGS: FGF23 decreases serum phosphate and 1,25-dihydroxyvitamin D levels. After the cloning of FGF23, several hypophosphatemic diseases, including tumor-induced osteomalacia and X-linked hypophosphatemic rickets (XLHR), were shown to be caused by excess actions of FGF23. In addition, recent studies indicated that mutations in the family with sequence similarity 20, member C (FAM20C), HRAS and NRAS genes, also caused FGF23-related hypophosphatemic diseases. The inhibition of FGF23 production or activity is, theoretically, an ideal treatment for these hypophosphatemic diseases. The C-terminal fragment of FGF23, inhibitors of FGF receptor and extracellular signal-regulated kinase, and anti-FGF23 antibody were shown to inhibit FGF23 actions both in vitro and in vivo. A phase I clinical trial of anti-FGF23 antibody has shown that this antibody increases serum phosphate in patients with XLHR.
SUMMARY: These recent findings confirm that FGF23 has a pivotal role in phosphate metabolism. The inhibition of FGF23 production or activity is promising as a new therapy for FGF23-related hypophosphatemic diseases. Further studies are clearly necessary to establish the clinical utility and long-term safety of these measures.

Avitan-Hersh E, Tatur S, Indelman M, et al.
Postzygotic HRAS mutation causing both keratinocytic epidermal nevus and thymoma and associated with bone dysplasia and hypophosphatemia due to elevated FGF23.
J Clin Endocrinol Metab. 2014; 99(1):E132-6 [PubMed] Related Publications
INTRODUCTION: Epidermal nevus syndrome is a rare group of disorders characterized by the combination of congenital epidermal nevi and extracutaneous features, including skeletal, neurological, ocular, and other systemic findings. We report a case of keratinocytic epidermal nevus syndrome that includes a thymoma, bone dysplasia, and hypophosphatemia with elevated fibroblast growth factor 23 (FGF23) levels associated with postzygotic HRAS mutation.
CASE REPORT: A 14-year-old boy was admitted due to recent limping. The physical examination revealed multiple right-sided linear epidermal nevi along Blaschko's lines. Magnetic resonance imaging showed cystic lesions in cervical bones and thymoma, and x-ray examination showed cystic lesions in the hands. Biochemical studies demonstrated severe hypophosphatemia, normocalcemia, high normal PTH, low 25-hydroxyvitamin D and low 1,25-dihydroxyvitamin D levels. The serum FGF23 C-terminal level was normal, but the intact FGF23 level was found to be elevated. Genetic evaluation revealed a heterozygote mutation in the HRAS gene in both the keratinocytic epidermal nevus and thymoma but not in DNA extracted from blood lymphocytes, thus establishing the mutation as postzygotic.
DISCUSSION: Postzygotic mutations in HRAS lead to elevation of FGF23 levels, as found in mutated PHEX, FGF23, DMP1, and ENPP1 genes, which lead to hypophosphatemia.
CONCLUSION: An identical postzygotic HRAS mutation was shown to be present in both keratinocytic epidermal nevus and thymoma and to be associated with bone lesions and hypophosphatemia due to elevated FGF23 levels. These may all be related to the HRAS mutation.

Meng QH, Xu E, Hildebrandt MA, et al.
Genetic variants in the fibroblast growth factor pathway as potential markers of ovarian cancer risk, therapeutic response, and clinical outcome.
Clin Chem. 2014; 60(1):222-32 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The fibroblast growth factor (FGF) and FGF receptor (FGFR) axis plays a critical role in tumorigenesis, but little is known of its influence in ovarian cancer. We sought to determine the association of genetic variants in the FGF pathway with risk, therapeutic response, and survival of patients with ovarian cancer.
METHODS: We matched 339 non-Hispanic white ovarian cancer cases with 349 healthy controls and genotyped them for 183 single-nucleotide polymorphisms (SNPs) from 24 FGF (fibroblast growth factor) and FGFR (fibroblast growth factor receptor) genes. Genetic associations for the main effect, gene-gene interactions, and the cumulative effect were determined.
RESULTS: Multiple SNPs in the FGF-FGFR axis were associated with an increased risk of ovarian cancer. In particular, FGF1 [fibroblast growth factor 1 (acidic)] SNP rs7727832 showed the most significant association with ovarian cancer (odds ratio, 2.27; 95% CI, 1.31-3.95). Ten SNPs were associated with a reduced risk of ovarian cancer. FGF18 (fibroblast growth factor 18) SNP rs3806929, FGF7 (fibroblast growth factor 7) SNP rs9920722, FGF23 (fibroblast growth factor 23) SNP rs12812339, and FGF5 (fibroblast growth factor 5) SNP rs3733336 were significantly associated with a favorable treatment response, with a reduction of risk of nonresponse of 40% to 60%. Eleven SNPs were significantly associated with overall survival. Of these SNPs, FGF23 rs7961824 was the most significantly associated with improved prognosis (hazard ratio, 0.55; 95% CI, 0.39-0.78) and was associated with significantly longer survival durations, compared with individuals with the common genotype at this locus (58.1 months vs. 38.0 months, P = 0.005). Survival tree analysis revealed FGF2 rs167428 as the primary factor contributing to overall survival.
CONCLUSIONS: Significant associations of genetic variants in the FGF pathway were associated with ovarian cancer risk, therapeutic response, and survival. The discovery of multiple SNPs in the FGF-FGFR pathway provides a molecular approach for risk assessment, monitoring therapeutic response, and prognosis.

Dërmaku-Sopjani M, Kolgeci S, Abazi S, Sopjani M
Significance of the anti-aging protein Klotho.
Mol Membr Biol. 2013; 30(8):369-85 [PubMed] Related Publications
The Klotho gene was identified as an 'aging suppressor' in mice. Overexpression of the Klotho gene extends lifespan and defective Klotho results in rapid aging and early death. Both the membrane and secreted forms of Klotho have biological activity that include regulatory effects on general metabolism and a more specific effect on mineral metabolism that correlates with its effect on aging. Klotho serves as a co-receptor for fibroblast growth factor (FGF), but it also functions as a humoral factor that regulates cell survival and proliferation, vitamin D metabolism, and calcium and phosphate homeostasis and may serve as a potential tumor suppressor. Moreover, Klotho protects against several pathogenic processes in a FGF23-independent manner. These processes include cancer metastasis, vascular calcification, and renal fibrosis. This review covers the recent advances in Klotho research and discusses novel Klotho-dependent mechanisms that are clinically relevant in aging and age-related diseases.

Kim HJ, Kim KH, Lee J, et al.
Single nucleotide polymorphisms in fibroblast growth factor 23 gene, FGF23, are associated with prostate cancer risk.
BJU Int. 2014; 114(2):303-10 [PubMed] Related Publications
OBJECTIVE: To determine whether sequence variants within the FGF23 gene are associated with the risk of developing prostate cancer in a Korean population.
PATIENTS AND METHODS: Five common single nucleotide polymorphisms (SNPs) in the FGF23 gene were assessed in 272 patients with prostate cancer and 173 control subjects with benign prostatic hyperplasia. Single-locus analyses were conducted using conditional logistic regression. In addition, we performed a haplotype analysis for the five FGF23 SNPs tested.
RESULTS: Three SNPs in the FGF23 gene (rs11063118, rs13312789 and rs7955866) were associated with an increased risk of prostate cancer in our study population. Odds ratios for homozygous variants vs wild-type variants ranged from 1.68 (95% confidence interval [CI]: 1.15-2.46) to 1.79 (95% CI: 1.16-2.75).
CONCLUSION: This is the first study showing that genetic variations in FGF23 increase prostate cancer susceptibility.

Lim YH, Ovejero D, Sugarman JS, et al.
Multilineage somatic activating mutations in HRAS and NRAS cause mosaic cutaneous and skeletal lesions, elevated FGF23 and hypophosphatemia.
Hum Mol Genet. 2014; 23(2):397-407 [PubMed] Free Access to Full Article Related Publications
Pathologically elevated serum levels of fibroblast growth factor-23 (FGF23), a bone-derived hormone that regulates phosphorus homeostasis, result in renal phosphate wasting and lead to rickets or osteomalacia. Rarely, elevated serum FGF23 levels are found in association with mosaic cutaneous disorders that affect large proportions of the skin and appear in patterns corresponding to the migration of ectodermal progenitors. The cause and source of elevated serum FGF23 is unknown. In those conditions, such as epidermal and large congenital melanocytic nevi, skin lesions are variably associated with other abnormalities in the eye, brain and vasculature. The wide distribution of involved tissues and the appearance of multiple segmental skin and bone lesions suggest that these conditions result from early embryonic somatic mutations. We report five such cases with elevated serum FGF23 and bone lesions, four with large epidermal nevi and one with a giant congenital melanocytic nevus. Exome sequencing of blood and affected skin tissue identified somatic activating mutations of HRAS or NRAS in each case without recurrent secondary mutation, and we further found that the same mutation is present in dysplastic bone. Our finding of somatic activating RAS mutation in bone, the endogenous source of FGF23, provides the first evidence that elevated serum FGF23 levels, hypophosphatemia and osteomalacia are associated with pathologic Ras activation and may provide insight in the heretofore limited understanding of the regulation of FGF23.

Feng S, Dakhova O, Creighton CJ, Ittmann M
Endocrine fibroblast growth factor FGF19 promotes prostate cancer progression.
Cancer Res. 2013; 73(8):2551-62 [PubMed] Free Access to Full Article Related Publications
Prostate cancer is the most common visceral malignancy and the second leading cause of cancer deaths in US men. There is broad evidence that fibroblast growth factor (FGF) receptors are important in prostate cancer initiation and progression, but the contribution of particular FGFs in this disease is not fully understood. The FGF family members FGF19, FGF21, and FGF23 comprise a distinct subfamily that circulate in serum and act in an endocrine manner. These endocrine FGFs require α-Klotho (KL) and/or β-Klotho (KLB), two related single-pass transmembrane proteins restricted in their tissue distribution, to act as coreceptors along with classic FGF receptors (FGFR) to mediate potent biologic activity. Here we show that FGF19 is expressed in primary and metastatic prostate cancer tissues, where it functions as an autocrine growth factor. Exogenous FGF19 promoted the growth, invasion, adhesion, and colony formation of prostate cancer cells at low ligand concentrations. FGF19 silencing in prostate cancer cells expressing autocrine FGF19 decreased invasion and proliferation in vitro and tumor growth in vivo. Consistent with these observations, KL and/or KLB were expressed in prostate cancer cells in vitro and in vivo, raising the possibility that additional endocrine FGFs may also exert biologic effects in prostate cancer. Our findings support the concept that therapies targeting FGFR signaling may have efficacy in prostate cancer and highlight FGF19 as a relevant endocrine FGF in this setting.

Leaf DE, Pereira RC, Bazari H, Jüppner H
Oncogenic osteomalacia due to FGF23-expressing colon adenocarcinoma.
J Clin Endocrinol Metab. 2013; 98(3):887-91 [PubMed] Free Access to Full Article Related Publications
CONTEXT: Oncogenic osteomalacia, a paraneoplastic syndrome associated with hypophosphatemia due to increased urinary phosphate excretion, is caused by excessive synthesis and secretion of fibroblast growth factor 23 (FGF23), a phosphaturic hormone that is normally produced by osteocytes. Most cases of oncogenic osteomalacia have been associated with benign tumors of bone or soft tissue; however, whether malignant neoplasms can also produce and secrete FGF23 is currently unknown.
OBJECTIVE: The aim was to determine whether a malignant neoplasm could cause oncogenic osteomalacia through excessive production and secretion of FGF23.
SETTING: We describe an 80-year-old woman with stage IV colon adenocarcinoma who presented with severe hypophosphatemia (0.4 mg/dL; reference, 2.6-4.5 mg/dL).
RESULTS: Fractional excretion of phosphate was 34% (reference, <5% in the setting of hypophosphatemia), and plasma levels of FGF23 were highly elevated at 674 RU/mL (reference, <180 RU/mL). Immunohistochemical analysis of the patient's tumor showed strong staining for FGF23. Genetic analyses revealed a point mutation in the KRAS gene.
CONCLUSIONS: We present the first case in which a malignant neoplasm is documented to produce and secrete FGF23, leading to renal phosphate-wasting. Oncogenic osteomalacia should be considered in the differential diagnosis for patients with a malignant tumor who present with hypophosphatemia.

Saini RK, Kaneko I, Jurutka PW, et al.
1,25-dihydroxyvitamin D(3) regulation of fibroblast growth factor-23 expression in bone cells: evidence for primary and secondary mechanisms modulated by leptin and interleukin-6.
Calcif Tissue Int. 2013; 92(4):339-53 [PubMed] Free Access to Full Article Related Publications
Fibroblast growth factor-23 (FGF23) is a circulating hormone that acts to correct hyperphosphatemic states by inhibiting renal phosphate reabsorption and to prevent hypervitaminosis D by feedback repressing 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) biosynthesis. FGF23 gene expression in the osteoblast/osteocyte is induced by the nuclear vitamin D receptor (VDR) bound to 1,25(OH)2D3, but cycloheximide sensitivity of this induction suggests that it may occur largely via secondary mechanisms requiring cooperating transcription factors. We therefore sought to identify 1,25(OH)2D3-regulated transcription factors that might impact FGF23 expression. Although neither leptin nor interleukin-6 (IL-6) alone affects FGF23 expression, leptin treatment was found to potentiate 1,25(OH)2D3 upregulation of FGF23 in UMR-106 cells, whereas IL-6 treatment blunted this upregulation. Genomic analyses revealed conserved binding sites for STATs (signal transduction mediators of leptin and IL-6 action) along with transcription factor ETS1 in human and other mammalian FGF23 genes. Further, STAT3, STAT1, ETS1, and VDR mRNAs were induced in a dose-dependent manner by 1,25(OH)2D3 in UMR-106 cells. Bioinformatic analysis identified nine potential VDREs in a genomic interval containing human FGF23. Six of the putative VDREs were capable of mediating direct transcriptional activation of a heterologous reporter gene when bound by a 1,25(OH)2D3-liganded VDR complex. A model is proposed wherein 1,25(OH)2D3 upregulates FGF23 production directly via multiple VDREs and indirectly via induction of STAT3, ETS1, and VDR transcription factors that are then activated via cell surface and intracellular signaling to cooperate in the induction of FGF23 through DNA looping and generation of euchromatin architecture.

Kuro-o M
Klotho in health and disease.
Curr Opin Nephrol Hypertens. 2012; 21(4):362-8 [PubMed] Related Publications
PURPOSE OF REVIEW: The klotho gene was originally identified as a putative aging-suppressor gene in mice that extended life span when overexpressed and induced a premature aging syndrome when disrupted. Subsequently, it became clear that the Klotho family of membrane proteins function as obligate co-receptors for endocrine fibroblast growth factors (FGFs) that regulate various metabolic processes. This review focuses on the Klotho-FGF23 endocrine system that maintains phosphate (Pi) homeostasis, and discusses the mechanism of action and the potential contribution of Klotho deficiency to acute kidney injury (AKI), chronic kidney disease (CKD) and cancer.
RECENT FINDINGS: Klotho functions as a receptor for the phosphaturic hormone FGF23. Klotho deficiency induces resistance to FGF23 and predisposition to Pi retention, which represents a critical feature of pathophysiology of CKD. The extracellular domain of Klotho protein is subject to ectodomain shedding and released into the blood and urine. Secreted Klotho functions as a humoral factor that inhibits AKI, vascular calcification, renal fibrosis, and cancer metastasis in an FGF23-independent manner.
SUMMARY: Various factors that affect Klotho expression have been identified. Prevention of Klotho decline and supplementation of Klotho can be a novel therapeutic strategy for many age-related diseases.

Imanishi Y, Hashimoto J, Ando W, et al.
Matrix extracellular phosphoglycoprotein is expressed in causative tumors of oncogenic osteomalacia.
J Bone Miner Metab. 2012; 30(1):93-9 [PubMed] Related Publications
Oncogenic osteomalacia (OOM), or tumor-induced osteomalacia, is a rare disease characterized by renal phosphate wasting and osteomalacia. It arises due to the secretion of fibroblast growth factor 23 (FGF-23) from causative tumors. Matrix extracellular phosphoglycoprotein (MEPE) is predominantly expressed in odontoblasts, osteoblasts, and osteocytes. Although the presence of MEPE mRNA has been reported in some OOM tumors, little is known about the prevalence of MEPE expression in OOM tumors. In this study, the expression of MEPE and FGF-23 in OOM tumors was investigated at the transcriptional and translational levels. Eleven causative OOM tumors were analyzed by quantitative real-time reverse transcription-polymerase chain reaction and immunohistochemistry for MEPE and FGF-23 expression. Hemangiopericytomas and giant cell tumors, pathological diagnoses that are common in cases of OOM, were obtained from non-osteomalacic patients and analyzed as controls. The gene expression level of FGF23 and MEPE in OOM tumors was 10(4)- and 10(5)-times higher, respectively, than in non-OOM tumors. Immunohistochemical staining revealed that FGF-23 protein was expressed in all OOM tumors, and MEPE was expressed in 10 out of 11 OOM tumors. Thus, MEPE expression was common in OOM tumors, similar to FGF-23. These results indicate that, in addition to the hypophosphatemic effects of FGF-23, MEPE or the MEPE-derived acidic serine aspartate-rich MEPE-associated motif peptide may contribute to decreased bone mineralization in OOM patients.

Abramovitz L, Rubinek T, Ligumsky H, et al.
KL1 internal repeat mediates klotho tumor suppressor activities and inhibits bFGF and IGF-I signaling in pancreatic cancer.
Clin Cancer Res. 2011; 17(13):4254-66 [PubMed] Related Publications
PURPOSE: Klotho is a transmembrane protein which can be shed, act as a circulating hormone and modulate the insulin-like growth factor (IGF)-I and the fibroblast growth factor (FGF) pathways. We have recently identified klotho as a tumor suppressor in breast cancer. Klotho is expressed in the normal pancreas and both the IGF-I and FGF pathways are involved in pancreatic cancer development. We, therefore, undertook to study the expression and activity of klotho in pancreatic cancer.
EXPERIMENTAL DESIGN: Klotho expression was studied using immunohistochemistry and quantitative RT-PCR. Effects of klotho on cell growth were assessed in the pancreatic cancer cells Panc1, MiaPaCa2, and Colo357, using colony and MTT assays and xenograft models. Signaling pathway activity was measured by Western blotting.
RESULTS: Klotho expression is downregulated in pancreatic adenocarcinoma. Overexpression of klotho, or treatment with soluble klotho, reduced growth of pancreatic cancer cells in vitro and in vivo, and inhibited activation of the IGF-I and the bFGF pathways. KL1 is a klotho subdomain formed by cleavage or alternative splicing. Compared with the full-length protein, KL1 showed similar growth inhibitory activity but did not promote FGF23 signaling. Thus, its administration to mice showed favorable safety profile.
CONCLUSIONS: These studies indicate klotho as a potential tumor suppressor in pancreatic cancer, and suggest, for the first time, that klotho tumor suppressive activities are mediated through its KL1 domain. These results suggest the use of klotho or KL1 as potential strategy for the development of novel therapeutic interventions for pancreatic cancer.

Itoh N
Hormone-like (endocrine) Fgfs: their evolutionary history and roles in development, metabolism, and disease.
Cell Tissue Res. 2010; 342(1):1-11 [PubMed] Free Access to Full Article Related Publications
Fibroblast growth factors (Fgfs) are proteins with diverse functions in development, repair, and metabolism. The human Fgf gene family with 22 members can be classified into three groups, canonical, intracellular, and hormone-like Fgf genes. In contrast to canonical and intracellular Fgfs identified in invertebrates and vertebrates, hormone-like Fgfs, Fgf15/19, Fgf21, and Fgf23, are vertebrate-specific. The ancestral gene of hormone-like Fgfs was generated from the ancestral gene of canonical Fgfs by gene duplication early in vertebrate evolution. Later, Fgf15/19, Fgf21, and Fgf23 were generated from the ancestral gene by genome duplication events. Canonical Fgfs act as autocrine/paracrine factors in an Fgf receptor (Fgfr)-dependent manner. In contrast, hormone-like Fgfs act as endocrine factors in an Fgfr-dependent manner. Canonical Fgfs have a heparin-binding site necessary for the stable binding of Fgfrs and local signaling. In contrast, hormone-like Fgfs acquired endocrine functions by reducing their heparin-binding affinity during their evolution. Fgf15/19 and Fgf23 require βKlotho and αKlotho as cofactors, respectively. However, Fgf21 might physiologically require neither. Hormone-like Fgfs play roles in metabolism at postnatal stages, although they also play roles in development at embryonic stages. Fgf15/19 regulates bile acid metabolism in the liver. Fgf21 regulates lipid metabolism in the white adipose tissue. Fgf23 regulates serum phosphate and active vitamin D levels. Fgf23 signaling disorders caused by hereditary diseases or tumors result in metabolic disorders. In addition, serum Fgf19 or Fgf21 levels are significantly increased by metabolic disorders. Hormone-like Fgfs are newly emerging and quite unique in their evolution and function.

Ichikawa S, Baujat G, Seyahi A, et al.
Clinical variability of familial tumoral calcinosis caused by novel GALNT3 mutations.
Am J Med Genet A. 2010; 152A(4):896-903 [PubMed] Free Access to Full Article Related Publications
The GALNT3 gene encodes GalNAc-T3, which prevents degradation of the phosphaturic hormone, fibroblast growth factor 23 (FGF23). Biallelic mutations in either GALNT3 or FGF23 result in hyperphosphatemic familial tumoral calcinosis or its variant, hyperostosis-hyperphosphatemia syndrome. Tumoral calcinosis is characterized by the presence of ectopic calcifications around major joints, whereas hyperostosis-hyperphosphatemia syndrome is characterized by recurrent long bone lesions with hyperostosis. Here we investigated four patients with hyperphosphatemia and clinical manifestations including tumoral calcinosis and/or hyperostosis-hyperphosphatemia syndrome to determine underlying genetic cause and delineate phenotypic heterogeneity of these disorders. Mutational analysis of FGF23 and GALNT3 in these patients revealed novel homozygous mutations in GALNT3. Although the presence of massive calcifications, cortical hyperostosis, or dental anomalies was not shared by all patients, all had persistent hyperphosphatemia. Three of the patients also had inappropriately normal 1,25-dihyroxyvitamin D [1,25(OH)(2)D] and confirmed low circulating intact FGF23 concentrations. The four novel GALNT3 mutations invariably resulted in hyperphosphatemia as a result of low intact FGF23, but other clinical manifestations were variable. Therefore, tumoral calcinosis and hyperostosis-hyperphosphatemia syndrome represent a continuous spectrum of the same disease caused by increased phosphate levels, rather than two distinct disorders.

Bergwitz C, Banerjee S, Abu-Zahra H, et al.
Defective O-glycosylation due to a novel homozygous S129P mutation is associated with lack of fibroblast growth factor 23 secretion and tumoral calcinosis.
J Clin Endocrinol Metab. 2009; 94(11):4267-74 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Homozygous mutations in fibroblast growth factor (FGF23) have recently been described as the genetic cause of one form of hyperphosphatemic tumoral calcinosis (HFTC). However, it remained unclear to date how these mutations lead to loss of biologically active FGF23 in the circulation.
METHODS: We here report a novel homozygous mutation, c.385T>C in FGF23 exon 2, which changes codon 129 from serine to proline (S129P) in a previously described individual affected by HFTC. The S129P mutation as well as two known FGF23 mutations, S71G and S129F, were introduced into an expression vector encoding wild-type (wt) human (h) FGF23 to yield [P129]hFGF23, [F129]hFGF23, and [G71]hFGF23; whole lysates, glycoprotein fractions, and conditioned media from HEK293 and COS-7 cells expressing these constructs were subjected to Western blot analysis using affinity-purified goat anti-hFGF23(51-69) and anti-hFGF23(206-222) antibodies.
RESULTS: We detected 25- and 32-kDa protein species in total lysates of HEK293 cells expressing wt-hFGF23. The 32-kDa band, representing O-glycosylated hFGF23, was not detectable in the glycoprotein fraction of lysates from HEK293 cells expressing [P129]hFGF23, and in comparison with wt-FGF23 only small amounts of [P129]hFGF23 were secreted into the medium. Similar results were obtained for cells expressing [G71]hFGF23 and [F129]hFGF23.
CONCLUSION: Our data for the first time directly show that FGF23 mutations associated with HFTC impair O-glycosylation in vitro resulting in poor secretion of the mutant hormone thereby explaining the characteristic hyperphosphatemic phenotype of homozygous carriers in vivo.

Krejci P, Prochazkova J, Bryja V, et al.
Molecular pathology of the fibroblast growth factor family.
Hum Mutat. 2009; 30(9):1245-55 [PubMed] Free Access to Full Article Related Publications
The human fibroblast growth factor (FGF) family contains 22 proteins that regulate a plethora of physiological processes in both developing and adult organism. The mutations in the FGF genes were not known to play role in human disease until the year 2000, when mutations in FGF23 were found to cause hypophosphatemic rickets. Nine years later, seven FGFs have been associated with human disorders. These include FGF3 in Michel aplasia; FGF8 in cleft lip/palate and in hypogonadotropic hypogonadism; FGF9 in carcinoma; FGF10 in the lacrimal/salivary glands aplasia, and lacrimo-auriculo-dento-digital syndrome; FGF14 in spinocerebellar ataxia; FGF20 in Parkinson disease; and FGF23 in tumoral calcinosis and hypophosphatemic rickets. The heterogeneity in the functional consequences of FGF mutations, the modes of inheritance, pattern of involved tissues/organs, and effects in different developmental stages provide fascinating insights into the physiology of the FGF signaling system. We review the current knowledge about the molecular pathology of the FGF family.

Bahrami A, Weiss SW, Montgomery E, et al.
RT-PCR analysis for FGF23 using paraffin sections in the diagnosis of phosphaturic mesenchymal tumors with and without known tumor induced osteomalacia.
Am J Surg Pathol. 2009; 33(9):1348-54 [PubMed] Related Publications
Phosphaturic mesenchymal tumors of the mixed connective tissue type (PMTMCT) are extremely rare, histologically distinctive neoplasms, which cause tumor-induced osteomalacia (TIO) in most cases through the elaboration of a phosphaturic hormone, fibroblast growth factor-23 (FGF23). Rarely, identical tumors without known TIO may be observed. We studied a large group of PMTMCT for expression of FGF23, using a novel reverse transcription polymerase chain reaction (RT-PCR) assay for FGF23 in formalin-fixed, paraffin-embedded tissues. Twenty-nine PMTMCT (17 with and 12 without TIO) and 23 non-PMTMCT (16 various mesenchymal tumors, including 5 chondromyxoid fibroma, 8 chondroblastoma, 1 hemangiopericytoma, 1 aneurysmal bone cyst, and 1 high grade sarcoma; 5 carcinomas; and 2 non-neoplastic tissues) were retrieved. Total RNA was extracted from formalin-fixed, paraffin-embedded sections for RT-PCR analysis. FGF23 was amplified using 3 sets of primers that spanned the intron/exon boundaries to amplify the 3 exons of FGF23 gene (140, 125, and 175 bp). The housekeeping gene phosphoglycerokinase (189 bp) was coamplified to check the RNA quality. Sixteen of 17 (94%) PMTMCT with TIO were FGF23-positive. Nine of 12 (75%) PMTMCT without TIO were FGF23-positive. Two chondromyxoid fibroma and 1 aneurysmal bone cyst were positive; all other non-PMTMCT were negative. We conclude that RT-PCR for FGF23 is a sensitive and specific means of confirming the diagnosis of PMTMCT both in patients with and without TIO. FGF23 gene expression was present in more than 90% of PMTMCT with known TIO, confirming the role of FGF23 in this syndrome. Rare FGF23-negative PMTMCT with known TIO likely express other phosphaturic hormones (eg, frizzled-related protein 4). Our finding of expression of FGF23 in 75% of histologically identical tumors without known TIO confirms the reproducibility of the diagnosis of PMTMCT, even in the absence of known phosphaturia.

Sheffer M, Bacolod MD, Zuk O, et al.
Association of survival and disease progression with chromosomal instability: a genomic exploration of colorectal cancer.
Proc Natl Acad Sci U S A. 2009; 106(17):7131-6 [PubMed] Free Access to Full Article Related Publications
During disease progression the cells that comprise solid malignancies undergo significant changes in gene copy number and chromosome structure. Colorectal cancer provides an excellent model to study this process. To indentify and characterize chromosomal abnormalities in colorectal cancer, we performed a statistical analysis of 299 expression and 130 SNP arrays profiled at different stages of the disease, including normal tissue, adenoma, stages 1-4 adenocarcinoma, and metastasis. We identified broad (> 1/2 chromosomal arm) and focal (< 1/2 chromosomal arm) events. Broad amplifications were noted on chromosomes 7, 8q, 13q, 20, and X and broad deletions on chromosomes 4, 8p, 14q, 15q, 17p, 18, 20p, and 22q. Focal events (gains or losses) were identified in regions containing known cancer pathway genes, such as VEGFA, MYC, MET, FGF6, FGF23, LYN, MMP9, MYBL2, AURKA, UBE2C, and PTEN. Other focal events encompassed potential new candidate tumor suppressors (losses) and oncogenes (gains), including CCDC68, CSMD1, POLR1D, and PMEPA1. From the expression data, we identified genes whose expression levels reflected their copy number changes and used this relationship to impute copy number changes to samples without accompanying SNP data. This analysis provided the statistical power to show that deletions of 8p, 4p, and 15q are associated with survival and disease progression, and that samples with simultaneous deletions in 18q, 8p, 4p, and 15q have a particularly poor prognosis. Annotation analysis reveals that the oxidative phosphorylation pathway shows a strong tendency for decreased expression in the samples characterized by poor prognosis.

Lammoglia JJ, Mericq V
Familial tumoral calcinosis caused by a novel FGF23 mutation: response to induction of tubular renal acidosis with acetazolamide and the non-calcium phosphate binder sevelamer.
Horm Res. 2009; 71(3):178-84 [PubMed] Related Publications
Hyperphosphatemic familial tumoral calcinosis (HFTC) is an uncommon disease characterized by periarticular calcifications produced by the deposition of amorphous extraosseous calcifications of hydroxyapatite. It is associated with hyperphosphatemia due to increased tubular phosphate reabsorption, despite normal renal function and normal plasma PTH levels. The disease can be caused by inactivating mutations in either the fibroblast growth factor 23 (FGF23) gene, the UDP-N-acetyl-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3) gene or in human KLOTHO (KL) gene. Herein, we describe a Caucasian 3-year-old girl with tumoral calcinosis who presented with elevated serum phosphorus levels and a large calcified mass at her left elbow which led to ulceration of the skin. Treatment with the phosphate binder sevelamer and the carbonic anhydrase inhibitor acetazolamide successfully reduced the serum phosphate levels and led to a reduction of the calcified mass. This medical management has not been described previously. Her 7-month-old sister also had elevated serum phosphate levels, but did not have ectopic calcifications. Sequencing analysis revealed a novel homozygous FGF23 missense mutation (c.367G>T, p.Gly123Trp) in both siblings while the parents were carriers of the mutation.

Ichikawa S, Imel EA, Kreiter ML, et al.
A homozygous missense mutation in human KLOTHO causes severe tumoral calcinosis.
J Clin Invest. 2007; 117(9):2684-91 [PubMed] Free Access to Full Article Related Publications
Familial tumoral calcinosis is characterized by ectopic calcifications and hyperphosphatemia due to inactivating mutations in FGF23 or UDP-N-acetyl-alpha-D-galactosamine:polypeptide N-acetylgalactosaminyltransferase 3 (GALNT3). Herein we report a homozygous missense mutation (H193R) in the KLOTHO (KL) gene of a 13-year-old girl who presented with severe tumoral calcinosis with dural and carotid artery calcifications. This patient exhibited defects in mineral ion homeostasis with marked hyperphosphatemia and hypercalcemia as well as elevated serum levels of parathyroid hormone and FGF23. Mapping of H193R mutation onto the crystal structure of myrosinase, a plant homolog of KL, revealed that this histidine residue was at the base of the deep catalytic cleft and mutation of this histidine to arginine should destabilize the putative glycosidase domain (KL1) of KL, thereby attenuating production of membrane-bound and secreted KL. Indeed, compared with wild-type KL, expression and secretion of H193R KL were markedly reduced in vitro, resulting in diminished ability of FGF23 to signal via its cognate FGF receptors. Taken together, our findings provide what we believe to be the first evidence that loss-of-function mutations in human KL impair FGF23 bioactivity, underscoring the essential role of KL in FGF23-mediated phosphate and vitamin D homeostasis in humans.

Williams K, Flanagan A, Folpe A, et al.
Lymphatic vessels are present in phosphaturic mesenchymal tumours.
Virchows Arch. 2007; 451(5):871-5 [PubMed] Related Publications
Oncogenic osteomalacia (OO) is an acquired form of hypophosphataemic osteomalacia, which is associated most commonly with the development of a benign phosphaturic mesenchymal tumour mixed connective tissue type (PMTMCT). PMTMCTs are generally well vascularised tumours, and many have in the past been classified as haemangiomas and haemangiopericytomas. Although these tumours show some morphological variation, it has been proposed that they represent a distinct histopathological entity. Our aim in this study was to determine by immunohistochemistry the vascular profile of PMTMCT. Using monoclonal antibodies directed against several vascular markers, including the lymphatic endothelial cell antigens LYVE 1 and podoplanin, we found that PMTMCTs, in contrast to haemangiomas and haemangiopericytomas, contain lymphatic vessels. Taken with previous observations that PMTMCTs overexpress FGF23 and other gene products, this finding provides further evidence that most osteomalacia associated mesenchymal tumours represent a discrete pathological entity.

Topaz O, Indelman M, Chefetz I, et al.
A deleterious mutation in SAMD9 causes normophosphatemic familial tumoral calcinosis.
Am J Hum Genet. 2006; 79(4):759-64 [PubMed] Free Access to Full Article Related Publications
Familial tumoral calcinosis (FTC) is a rare autosomal recessive disorder characterized by the progressive deposition of calcified masses in cutaneous and subcutaneous tissues, which results in painful ulcerative lesions and severe skin and bone infections. Two major types of FTC have been recognized: hyperphosphatemic FTC (HFTC) and normophosphatemic FTC (NFTC). HFTC was recently shown to result from mutations in two different genes: GALNT3, which codes for a glycosyltransferase, and FGF23, which codes for a potent phosphaturic protein. To determine the molecular cause of NFTC, we performed homozygosity mapping in five affected families of Jewish Yemenite origin and mapped NFTC to 7q21-7q21.3. Mutation analysis revealed a homozygous mutation in the SAMD9 gene (K1495E), which was found to segregate with the disease in all families and to interfere with the protein expression. Our data suggest that SAMD9 is involved in the regulation of extraosseous calcification, a process of considerable importance in a wide range of diseases as common as atherosclerosis and autoimmune disorders.

Karrman K, Andersson A, Björgvinsdóttir H, et al.
Deregulation of cyclin D2 by juxtaposition with T-cell receptor alpha/delta locus in t(12;14)(p13;q11)-positive childhood T-cell acute lymphoblastic leukemia.
Eur J Haematol. 2006; 77(1):27-34 [PubMed] Related Publications
OBJECTIVES: The t(12;14)(p13;q11)--a recurrent translocation in childhood T-cell acute lymphoblastic leukemia (T-ALL)--has very recently been molecularly characterized in one case, which displayed overexpression of the cyclin D2 gene (CCND2).
PATIENTS AND METHODS: We have characterized two pediatric t(12;14)-positive T-ALLs using fluorescence in situ hybridization (FISH), cDNA microarray, and real-time polymerase chain reaction (PCR).
RESULTS: FISH revealed breakpoints (BPs) in the T-cell receptor alpha/delta locus (14q11) and in the vicinity of the CCND2 gene at 12p13. To investigate the expression of genes in 12p13, cDNA microarray analysis was performed. Expression data for eight genes, including CCND2, surrounding the 12p BP were compared with those in other T-ALLs. The t(12;14)-positive T-ALL displayed an increased expression of CCND2 compared to the controls, whereas the expression of the other genes was similar in all T-ALLs. Expression of CCND2 and two additional genes (PARP11 and FGF23), close to the 12p BP, was investigated with real-time PCR of the two t(12;14)-positive cases and four controls. Neither PARP11 nor FGF23 displayed expression differences among the T-ALLs, whereas CCND2 was clearly overexpressed in both t(12;14)-positive cases as compared to the mean expression level in the controls.
CONCLUSION: We have confirmed, in two additional cases, that the recurrent T-ALL-associated t(12;14) results in overexpression of cyclin D2. The t(12;14) is the first neoplasia-associated translocation shown to result in overexpression of cyclin D2. Furthermore, it is the first example of a T-cell neoplasm with a targeted deregulation of a member of a cyclin-encoding gene family.

Araya K, Fukumoto S, Backenroth R, et al.
A novel mutation in fibroblast growth factor 23 gene as a cause of tumoral calcinosis.
J Clin Endocrinol Metab. 2005; 90(10):5523-7 [PubMed] Related Publications
CONTEXT: Tumoral calcinosis is a disease characterized by ectopic calcification and hyperphosphatemia due to enhanced renal tubular phosphate reabsorption. Fibroblast growth factor (FGF)23 was identified as a responsible factor in hypophosphatemic diseases caused by renal phosphate leak.
OBJECTIVE: The objective of the study was to analyze the involvement of FGF23 in the development of tumoral calcinosis.
DESIGN: Serum FGF23 level was evaluated in a patient with tumoral calcinosis by two kinds of ELISA: full-length assay that detects only full-length FGF23 with phosphate-lowering activity and C-terminal assay that measures full-length as well as C-terminal fragment of FGF23. FGF23 gene was analyzed by direct sequencing of PCR products, and mutant FGF23 was analyzed by Western blotting after expression in mammalian cells.
PATIENTS: A family of tumoral calcinosis patients were studied.
RESULTS: Serum FGF23 was extremely high when measured by C-terminal assay. In contrast, it was low normal by full-length assay. Analysis of FGF23 gene detected a serine to phenylalanine mutation in codon 129. No wild-type allele of this codon was found in the patient. The brother of the proband showed the same base change. When this mutant FGF23 was expressed in vitro, full-length and N-terminal fragments were barely detectable by Western blotting, whereas C-terminal fragment with the same molecular weight as that from wild-type FGF23 could be detected.
CONCLUSION: The production and serum level of C-terminal fragment of FGF23 are increased in this patient with tumoral calcinosis. Together with the recent similar report of FGF23 mutation, impaired action of full-length FGF23 seems to result in tumoral calcinosis.

Carpenter TO, Ellis BK, Insogna KL, et al.
Fibroblast growth factor 7: an inhibitor of phosphate transport derived from oncogenic osteomalacia-causing tumors.
J Clin Endocrinol Metab. 2005; 90(2):1012-20 [PubMed] Related Publications
Oncogenic osteomalacia (OO), a tumor-associated phosphate-wasting syndrome, provides an opportunity to identify regulators of renal phosphate homeostasis. We established cultures from OO-associated tumors. Conditioned medium from these cultures inhibited phosphate uptake in renal tubular epithelial cells. We then compared RNA from tumor-derived cultures expressing inhibitory activity with RNA from tumor-derived cultures in which inhibitory activity was not evident and identified candidate mRNAs specifically expressed by cultures inhibiting renal phosphate transport. Testing of identified candidates revealed that one protein, fibroblast growth factor 7 (FGF7), was a potent and direct inhibitor of phosphate uptake in vitro. A neutralizing monoclonal antibody to FGF7 reversed FGF7-dependent phosphate transport inhibition and inhibitory activity in conditioned medium from tumor cell cultures. Immunoassay revealed abundant FGF7 in inhibitory conditioned medium and minimal amounts in nonconditioned medium or conditioned medium with no phosphate transport inhibitory activity. Furthermore, only small amounts of FGF23 were present in inhibitory conditioned medium, comparable to concentrations found in conditioned medium with no phosphate transport inhibitory activity. Thus, FGF7 was specifically identified when selecting for in vitro phosphate transport inhibitory activity of tumor-derived cultures and was confirmed as a potent inhibitor of phosphate transport. Finally, FGF7 message was confirmed in PCR products of mRNA extracted from fragments of each tumor. Members of the FGF family (other than FGF23) are expressed by OO-associated tumors and may play a role in mediating this syndrome.

Bai X, Miao D, Li J, et al.
Transgenic mice overexpressing human fibroblast growth factor 23 (R176Q) delineate a putative role for parathyroid hormone in renal phosphate wasting disorders.
Endocrinology. 2004; 145(11):5269-79 [PubMed] Related Publications
Fibroblast growth factor 23 (FGF23) is a recently characterized protein likely involved in the regulation of serum phosphate homeostasis. Increased circulating levels of FGF23 have been reported in patients with renal phosphate-wasting disorders, but it is unclear whether FGF23 is the direct mediator responsible for the decreased phosphate transport at the proximal renal tubules and the altered vitamin D metabolism associated with these states. To examine this question, we generated transgenic mice expressing and secreting from the liver human FGF23 (R176Q), a mutant form that fails to be degraded by furin proteases. At 1 and 2 months of age, mice carrying the transgene recapitulated the biochemical (decreased urinary phosphate reabsorption, hypophosphatemia, low serum 1,25-dihydroxyvitamin D(3)) and skeletal (rickets and osteomalacia) alterations associated with these disorders. Unexpectantly, marked changes in parameters of calcium homeostasis were also observed, consistent with secondary hyperparathyroidism. Moreover, in the kidney the anticipated alterations in the expression of hydroxylases associated with vitamin D metabolism were not observed despite the profound hypophosphatemia and increased circulating levels of PTH, both major physiological stimuli for 1,25-dihydroxyvitamin D(3) production. Our findings strongly support the novel concept that high circulating levels of FGF23 are associated with profound disturbances in the regulation of phosphate and vitamin D metabolism as well as calcium homeostasis and that elevated PTH levels likely also contribute to the renal phosphate wasting associated with these disorders.

Ward LM, Rauch F, White KE, et al.
Resolution of severe, adolescent-onset hypophosphatemic rickets following resection of an FGF-23-producing tumour of the distal ulna.
Bone. 2004; 34(5):905-11 [PubMed] Related Publications
Oncogenic hypophosphatemic osteomalacia (OHO) is an uncommon hypophosphatemic syndrome characterized by bone pain, proximal muscle weakness and rickets. It has been postulated that OHO results from overproduction of a humoral phosphaturic factor by an occult tumour. Recently, some OHO tumours have been shown to elaborate fibroblast growth factor-23 (FGF-23), which causes renal phosphate wasting when administered to mice. The purpose of this study was to undertake detailed investigations to confirm the diagnosis of OHO in a pediatric patient and to document the biochemical, radiographic and bone histological phenotype before and after tumour removal. We describe an 11-year-old, previously healthy girl with significant pain and functional disability associated with hypophosphatemic rickets. Circulating 1,25-(OH)(2) vitamin D was very low (14 pM; N: 40-140) while the FGF-23 serum level was markedly elevated [359.5 reference units (RU)/ml, N: 33-105]. An iliac bone biopsy revealed severe osteomalacia, but periosteocytic lesions, as are typical for X-linked hypophosphatemic rickets, were not seen. Sequence analyses of the PHEX and FGF23 genes were normal. A radiographic skeletal survey revealed a small exostosis of the left, distal ulnar metaphysis. A tumour was subsequently removed from this site and the pathology was consistent with benign, fibro-osseous tissue. Serum FGF-23 was normal when measured at 7 h post-operatively, while serum phosphate reached the low-normal range at 16 days following surgery. An iliac bone biopsy taken 5 months after the operation showed improvement, but not yet resolution, of the osteomalacia. Biochemical parameters of bone and mineral metabolism suggested that complete resolution of the osteomalacia was not achieved until 12 months following surgery. One year after tumour removal, the patient was pain-free and had resumed a normal level of activity. The rapid normalization of FGF-23 levels following removal of a benign tumour and the subsequent improvement in the biochemical and histological parameters of bone and mineral metabolism suggest that FGF-23 played a key role in this girl's disease.

Katoh M
WNT and FGF gene clusters (review).
Int J Oncol. 2002; 21(6):1269-73 [PubMed] Related Publications
Mouse mammary tumor virus (MMTV) is a retrovirus, activating Wnt genes (Wnt1/int-1, Wnt3/int-4, Wnt10b), Fgf genes (Fgf3/int-2, Fgf4, Fgf8) and other genes (Notch4/int-3, Eif3s6/int-6) due to proviral integration. Among 19 WNT genes, WNT3 and WNT14B genes are clustered in human chromosome 17q21, WNT3A and WNT14 in human chromosome 1q42, WNT10A and WNT6 in human chromosome 2q35, and WNT10B and WNT1 in human chromosome 12q13. Among 22 FGF genes, FGF19, FGF4 and FGF3 genes are clustered in human chromosome 11q13, while FGF23 and FGF6 in human chromosome 12p13. WNT and FGF gene clusters are conserved between the human genome and the mouse genome. Activation of mouse Wnt or Fgf genes due to proviral integration of MMTV occurs in 5 out of 13 clustered genes, and in 1 out of 28 solitary genes (p=0.0033), which clearly indicates that mouse Wnt or Fgf gene clusters are recombination hot spots associated with carcinogenesis. Recombination results in retroviral integration as well as in chromosomal translocation, gene amplification and deletion during carcinogenesis. The CCND1-FGF19-FGF4-FGF3 gene cluster in human chromosome 11q13 is amplified in breast cancer, squamous cell carcinoma of head and neck, and bladder tumors, and is also translocated in parathyroid tumors and B-cell lymphoma. WNT gene clusters on human chromosome 1q42, 2q35, 12q13, and 17q21 as well as FGF gene cluster on human chromosome 12p13 might be amplified or translocated in human cancer just like FGF gene cluster on human chromosome 11q13.

Fukumoto S, Yamashita T
Fibroblast growth factor-23 is the phosphaturic factor in tumor-induced osteomalacia and may be phosphatonin.
Curr Opin Nephrol Hypertens. 2002; 11(4):385-9 [PubMed] Related Publications
PURPOSE OF REVIEW: Three hypophosphatemic diseases, X-linked dominant hypophosphatemic rickets/osteomalacia (XLH), autosomal dominant hypophosphatemic rickets/osteomalacia (ADHR) and tumor-induced rickets/osteomalacia (TIO), show very similar clinical features including hypophosphatemia due to renal phosphate wasting. Because of some evidence that XLH and TIO are caused by a humoral mechanism, the presence of a phosphate-regulating hormone, phosphatonin, was hypothesized. The causative factor of TIO has been thought to be a strong candidate for phosphatonin. In this review, we summarize recent findings concerning a humoral factor which causes TIO, and discuss the nature of phosphatonin.
RECENT FINDINGS: The PHEX gene and fibroblast growth factor (FGF)-23 were identified as responsible genes for XLH and ADHR, respectively. In addition, FGF-23 was cloned as a gene abundantly expressed in a responsible tumor for TIO and was shown to reproduce almost all characteristics of TIO when overexpressed in mice. Furthermore, FGF-23 was proteolytically processed between Arg(179) and Ser(180), and all mutations found in ADHR existed in this proteolytic consensus site. Mutant FGF-23 proteins were resistant to the processing and seem to have somehow increased biological activity. There is not yet enough evidence that FGF-23 is phosphatonin, and the relation between PHEX and FGF-23 is unclear.
SUMMARY: FGF-23 plays important roles in the development of hypophosphatemic diseases. These findings will certainly contribute to the development of new diagnostic and therapeutic maneuvers for hypophosphatemic diseases.

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