Gene Summary

Gene:FGF23; fibroblast growth factor 23
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, HGNC, Ensembl, GeneCard, Gene
Protein:fibroblast growth factor 23
Source:NCBIAccessed: 31 August, 2019


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

Research Indicators

Publications Per Year (1994-2019)
Graph generated 31 August 2019 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 31 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (7)

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)

Singhi AD, George B, Greenbowe JR, et al.
Real-Time Targeted Genome Profile Analysis of Pancreatic Ductal Adenocarcinomas Identifies Genetic Alterations That Might Be Targeted With Existing Drugs or Used as Biomarkers.
Gastroenterology. 2019; 156(8):2242-2253.e4 [PubMed] Related Publications
BACKGROUND & AIMS: It has been a challenge to select treatment for patients with pancreatic ductal adenocarcinomas (PDACs) based on genome alterations. We performed targeted genomic profile analyses of a large number of PDACs to assess the full spectrum of actionable genomic alterations.
METHODS: We performed targeted genomic profile analyses of 3594 PDAC samples from an international cohort, including capture-based targeted genomic profiling of as many as 315 cancer-associated genes and intron regions of 28 genes that are rearranged in cancer cells. Tumor mutation burden (TMB) and microsatellite instability (MSI) status were also assessed. TMB was calculated across a 1.14-megabase region; TMB-high was defined as ≥20 mutations/megabase. MSI-high status was assigned based on analysis of 114 intron homopolymer loci.
RESULTS: KRAS, TP53, CDKN2A, and SMAD4 were the most frequently altered genes in PDAC. We found KRAS mutations in 88% of samples. Among PDACs without mutations in KRAS, we found alterations in genes whose products are in the mitogen-activated protein kinase signaling pathway and are candidate drug targets (actionable targets, n = 132; 4%), as well as gene fusions (n = 51), gene amplifications (n = 35), genes with missense mutations (n = 30), and genes that contain deletions (n = 16). Many of these encode proteins in receptor tyrosine kinase, RAS, or mitogen-activated protein kinase signaling pathways. Aside from TP53, alterations in genes encoding DNA damage repair proteins (BRCA and FANC) were detected in 14% of PDACs. Among PDACs evaluated for MSI (n = 2563) and TMB (n = 1021), MSI-high and/or TMB-high phenotypes were detected in 0.5% of samples. Alterations in FGF23, CCND2, PIK3CA, and FGF6 were more commonly detected in intraductal papillary mucinous neoplasm-associated PDACs.
CONCLUSIONS: In targeted genomic profile analyses of 3594 PDACs, we found 17% to contain genomic alterations that might make the tumor cells susceptible to currently used anticancer agents. We identified mutations in genes that could contribute to progression of intraductal papillary mucinous neoplasms into malignancies. These alterations might be used as biomarkers for early detection.

Li JR, Chiu KY, Ou YC, et al.
Alteration in serum concentrations of FGF19, FGF21, and FGF23 in patients with urothelial carcinoma.
Biofactors. 2019; 45(1):62-68 [PubMed] Related Publications
Fibroblast growth factors (FGF) 19, 21, and 23 have been reported as functional factors in human metabolic diseases and malignancies. We performed a prospective survey to compare circulating FGF levels in urothelial carcinoma (UC) patients and normal controls. Between 2016 and 2017, 39 patients with UC of the urinary bladder or upper urinary tract who received surgical intervention were included. All the serum samples were obtained before surgeries. The control group included 28 healthy volunteers. Analysis of the circulating FGF19, 21, and 23 levels among all 67 subjects, as well as a subgroup analysis of the 39 UC patients were performed. The median levels of serum FGF19, 21, and 23 in the UC patients were 84.2, 505.3, and 117.6 pg/mL, respectively, which were statistically different from levels found in the healthy controls (P = 0.015, <0.001 and < 0.001, respectively). In the subgroup analysis, the FGF19 and FGF21 levels were significantly higher in end-stage renal disease UC patients, while FGF21 was also higher in the UC patients with cardiovascular diseases and history of recurrent UC. In the receiver operating characteristic (ROC) curve analysis, FGF19, 21, and 23 were all significant predictors of UC [area under the curve (AUC)] 0.674, P = 0.015; AUC 0.918, P < 0.001; AUC 0.897, P < 0.001, respectively). In UC patients, serum FGF19 level was significantly lower, while FGF21 and 23 were significantly higher, than respective levels in healthy controls. All three markers may serve as good predictors of UC occurrence, and FGF21 level was associated with disease recurrence. © 2018 BioFactors, 45(1):62-68, 2019.

Kanai T, Shiizaki K, Betsui H, et al.
A decreased soluble Klotho level with normal eGFR, FGF23, serum phosphate, and FEP in an ADPKD patient with enlarged kidneys due to multiple cysts.
CEN Case Rep. 2018; 7(2):259-263 [PubMed] Free Access to Full Article Related Publications
Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disorder. ADPKD is characterized clinically by the presence of multiple bilateral renal cysts that lead to chronic renal failure. The cysts evolve from renal tubular epithelial cells that express the Klotho gene. Notably, Klotho acts as a co-receptor for fibroblast growth factor 23 (FGF23); in this context, it induces phosphaturia and maintains serum phosphate at a normal level. Many reports have shown that decreases in the soluble Klotho level and increases in the FGF23 level are associated with glomerular filtration rate (GFR) decline, but a recent study observed these changes in patient with normal eGFR. It remains unclear whether the decrease in the Klotho level precedes the increase in FGF23. Here, we present an ADPKD patient with enlarged kidneys due to multiple cysts who had a decreased soluble Klotho level but a normal eGFR and a normal FGF23 level. The patient's serum phosphate level was normal, as was the fractional excretion of phosphate (FEP). This appears to be the first reported case to show a decreased soluble Klotho level plus normal eGFR, FGF23, and FEP. These results suggest that Klotho decreases before FGF23 increases and further suggest that Klotho is not required to maintain normal serum phosphate levels in ADPKD if the FEP and serum phosphate levels are normal.

Kinoshita Y, Fukumoto S
X-Linked Hypophosphatemia and FGF23-Related Hypophosphatemic Diseases: Prospect for New Treatment.
Endocr Rev. 2018; 39(3):274-291 [PubMed] Related Publications
Phosphate plays essential roles in many biological processes, and the serum phosphate level is tightly controlled. Chronic hypophosphatemia causes impaired mineralization of the bone matrix and results in rickets and osteomalacia. Fibroblast growth factor 23 (FGF23) is a bone-derived hormone that regulates phosphate metabolism. FGF23 excess induces hypophosphatemia via impaired phosphate reabsorption in the renal proximal tubules and decreased phosphate absorption in the intestines. There are several types of genetic and acquired FGF23-related hypophosphatemic diseases. Among these diseases, X-linked hypophosphatemia (XLH), which is caused by inactivating mutations in the phosphate-regulating endopeptidase homolog, X-linked (PHEX) gene, is the most prevalent form of genetic FGF23-related hypophosphatemic rickets. Another clinically relevant form of FGF23-related hypophosphatemic disease is tumor-induced osteomalacia (TIO), a paraneoplastic syndrome associated with FGF23-producing tumors. A combination of active vitamin D and phosphate salts is the current medical therapy used to treat patients with XLH and inoperative TIO. However, this therapy has certain efficacy- and safety-associated limitations. Several measures to inhibit FGF23 activity have been considered as possible new treatments for FGF23-related hypophosphatemic diseases. In particular, a humanized monoclonal antibody for FGF23 (burosumab) is a promising treatment in patients with XLH and TIO. This review will focus on the phosphate metabolism and the pathogenesis and treatment of FGF23-related hypophosphatemic diseases.

Berglund JA, Gafni RI, Wodajo F, et al.
Tumor-induced osteomalacia in association with PTEN-negative Cowden syndrome.
Osteoporos Int. 2018; 29(4):993-997 [PubMed] Related Publications
Tumor-induced osteomalacia (TIO) is a rare paraneoplastic condition in which phosphaturic mesenchymal tumors (PMTs) secrete high levels of fibroblast growth factor 23 (FGF23) into the circulation. This results in renal phosphate wasting, hypophosphatemia, muscle weakness, bone pain, and pathological fractures. Recent studies suggest that fibronectin-fibroblast growth factor receptor 1 (FN1-FGFR1) translocations may be a driver of tumorigenesis. We present a patient with TIO who also exhibited clinical findings suggestive of Cowden syndrome (CS), a rare autosomal dominant disorder characterized by numerous benign hamartomas, as well as an increased risk for multiple malignancies, such as thyroid cancer. While CS is a clinical diagnosis, most, but not all, harbor a mutation in the tumor suppressor gene PTEN. Genetic testing revealed a somatic FN1-FGFR1 translocation in the FGF23-producing tumor causing TIO; however, a germline PTEN mutation was not identified. To our knowledge, this is the first reported case of concurrent TIO and CS.

Yamada Y, Kinoshita I, Kenichi K, et al.
Histopathological and genetic review of phosphaturic mesenchymal tumours, mixed connective tissue variant.
Histopathology. 2018; 72(3):460-471 [PubMed] Related Publications
AIMS: Phosphaturic mesenchymal tumour, mixed connective tissue variant (PMT-MCT), is a tumour of uncertain differentiation, characterised by 'smudgy/grungy' calcification and vitamin D-resistant phosphaturic osteomalacia. Fibroblast growth factor (FGF)23 is recognised as a reliable marker of PMT-MCT, but quantitative evaluation has never been performed. We reviewed cases of tumour-associated osteomalacia or histologically definitive PMT-MCT without osteomalacia using histological, immunohistochemical and genetic methods and evaluated the diagnostic significance of these findings.
METHODS AND RESULTS: A total of 19 tumours from 14 cases diagnosed previously as PMT-MCT were retrieved, on which immunohistochemical staining, reverse transcription-polymerase chain reaction (RT-PCR) and fluorescence in-situ hybridisation (FISH) analysis were performed. Histologically, fibrous capsule, calcification and giant cell reaction tended to be observed in soft-tissue PMT-MCT, while PMT-MCT of bone and multiple PMT-MCT showed an infiltrative growth pattern. The immunohistochemical results were as follows: the tumour cells were positive for FGF23 (nine of 12, 75%), FGFR1 (11 of 11, 100%), CD56 (12 of 14, 85.7%) and E26 oncogene homologue (ERG) (5 of 13, 38.4%). The sole malignant tumour was positive for p53. FGF23 mRNA was detected in seven of 14 formalin-fixed paraffin-embedded (FFPE) specimens and all five frozen specimens by RT-PCR. The level of FGF23 mRNA, which was determined by real-time PCR, varied among the phosphaturic cases. Two of 17 tumours were positive for FGFR1 gene rearrangement.
CONCLUSIONS: It was considered that PMT-MCT is a histopathological entity with or without phosphaturia, with varying levels of FGF23 mRNA, and with or without fibronectin 1 (FN1)-FGFR1 fusion gene. The authors propose that the histology of PMT-MCT differs depending on its location, such as bone or soft tissue, which could complicate the differential diagnosis.

Agaimy A, Michal M, Chiosea S, et al.
Phosphaturic Mesenchymal Tumors: Clinicopathologic, Immunohistochemical and Molecular Analysis of 22 Cases Expanding their Morphologic and Immunophenotypic Spectrum.
Am J Surg Pathol. 2017; 41(10):1371-1380 [PubMed] Related Publications
Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm of uncertain histogenesis that has been linked to tumor-induced osteomalacia (TIO) since 1959. The neoplastic cells produce increased amount of FGF23 which results in TIO via uncontrolled renal loss of phosphate (phosphaturia), and consequently diminished bone mineralization. To date, ∼300 cases have been reported. Although there is increasing evidence that PMT can be diagnosed by reproducible histopathologic features, firm diagnosis has been often restricted to cases associated with TIO and, hence, diagnosis of "nonphosphaturic variants" remained challenging. Recently, FGFR1/FN1 gene fusions were detected in roughly half of cases. We herein reviewed the clinicopathologic features of 22 PMTs (15 cases not published before), stained them with an extended immunohistochemical marker panel and examined them by fluorescence in situ hybridization for FGFR1 gene fusions. Patients were 12 males and 9 females (one of unknown sex) aged 33 to 83 years (median: 52 y). Lesions affected the soft tissues (n=11), bones (n=6), sinonasal tract (n=4), and unspecified site (n=1). Most lesions originated in the extremities (9 in the lower and 4 in the upper extremities). Acral sites were involved in 10 patients (6 foot/heel, 3 fingers/hands, and 1 in unspecified digit). Phosphaturia and TIO were recorded in 10/11 and 9/14 patients with detailed clinical data, respectively. Limited follow-up (5 mo to 14 y; median: 16 mo) was available for 14 patients. Local recurrence was noted in one patient and metastasis in another patient. Histologically, 11 tumors were purely of conventional mixed connective tissue type, 3 were chondromyxoid fibroma-like, 2 were hemangio-/glomangiopericytoma-like with giant cells, and 1 case each angiomyolipoma-like and reparative giant cell granuloma-like. Four tumors contained admixture of patterns (predominantly cellular with variable conventional component). Immunohistochemistry showed consistent expression of CD56 (11/11; 100%), ERG (19/21; 90%), SATB2 (19/21; 90%), and somatostatin receptor 2A (15/19; 79%), while other markers tested negative: DOG1 (0/17), beta-catenin (0/14), S100 protein (0/14), and STAT6 (0/7). FGFR1 fluorescence in situ hybridization was positive in 8/17 (47%) evaluable cases. These results add to the phenotypic delineation of PMT reporting for the first time consistent expression of SATB2 and excluding any phenotypic overlap with solitary fibrous tumor or sinonasal glomangiopericytoma. The unifying immunophenotype of the neoplastic cells irrespective of the histologic pattern suggests a specific disease entity with diverse morphotypes/variants rather than different neoplasms unified by TIO.

Kamiya N, Yamaguchi R, Aruwajoye O, et al.
Targeted Disruption of NF1 in Osteocytes Increases FGF23 and Osteoid With Osteomalacia-like Bone Phenotype.
J Bone Miner Res. 2017; 32(8):1716-1726 [PubMed] Related Publications
Neurofibromatosis type 1 (NF1, OMIM 162200), caused by NF1 gene mutations, exhibits multi-system abnormalities, including skeletal deformities in humans. Osteocytes play critical roles in controlling bone modeling and remodeling. However, the role of neurofibromin, the protein product of the NF1 gene, in osteocytes is largely unknown. This study investigated the role of neurofibromin in osteocytes by disrupting Nf1 under the Dmp1-promoter. The conditional knockout (Nf1 cKO) mice displayed serum profile of a metabolic bone disorder with an osteomalacia-like bone phenotype. Serum FGF23 levels were 4 times increased in cKO mice compared with age-matched controls. In addition, calcium-phosphorus metabolism was significantly altered (calcium reduced; phosphorus reduced; parathyroid hormone [PTH] increased; 1,25(OH)

Balenga N, Azimzadeh P, Hogue JA, et al.
Orphan Adhesion GPCR GPR64/ADGRG2 Is Overexpressed in Parathyroid Tumors and Attenuates Calcium-Sensing Receptor-Mediated Signaling.
J Bone Miner Res. 2017; 32(3):654-666 [PubMed] Related Publications
Abnormal feedback of serum calcium to parathyroid hormone (PTH) secretion is the hallmark of primary hyperparathyroidism (PHPT). Although the molecular pathogenesis of parathyroid neoplasia in PHPT has been linked to abnormal expression of genes involved in cell growth (e.g., cyclin D1, retinoblastoma, and β-catenin), the molecular basis of abnormal calcium sensing by calcium-sensing receptor (CaSR) and PTH hypersecretion in PHPT are incompletely understood. Through gene expression profiling, we discovered that an orphan adhesion G protein-coupled receptor (GPCR), GPR64/ADGRG2, is expressed in human normal parathyroid glands and is overexpressed in parathyroid tumors from patients with PHPT. Using immunohistochemistry, Western blotting, and coimmunoprecipitation, we found that GPR64 is expressed on the cell surface of parathyroid cells, is overexpressed in parathyroid tumors, and physically interacts with the CaSR. By using reporter gene assay and GPCR second messenger readouts we identified Gαs, 3',5'-cyclic adenosine monophosphate (cAMP), protein kinase A, and cAMP response element binding protein (CREB) as the signaling cascade downstream of GPR64. Furthermore, we found that an N-terminally truncated human GPR64 is constitutively active and a 15-amino acid-long peptide C-terminal to the GPCR proteolysis site (GPS) of GPR64 activates this receptor. Functional characterization of GPR64 demonstrated its ability to increase PTH release from human parathyroid cells at a range of calcium concentrations. We discovered that the truncated constitutively active, but not the full-length GPR64 physically interacts with CaSR and attenuates the CaSR-mediated intracellular Ca

Lee JC, Su SY, Changou CA, et al.
Characterization of FN1-FGFR1 and novel FN1-FGF1 fusion genes in a large series of phosphaturic mesenchymal tumors.
Mod Pathol. 2016; 29(11):1335-1346 [PubMed] Related Publications
Phosphaturic mesenchymal tumors typically cause paraneoplastic osteomalacia, chiefly as a result of FGF23 secretion. In a prior study, we identified FN1-FGFR1 fusion in 9 of 15 phosphaturic mesenchymal tumors. In this study, a total of 66 phosphaturic mesenchymal tumors and 7 tumors resembling phosphaturic mesenchymal tumor but without known phosphaturia were studied. A novel FN1-FGF1 fusion gene was identified in two cases without FN1-FGFR1 fusion by RNA sequencing and cross-validated with direct sequencing and western blot. Fluorescence in situ hybridization analyses revealed FN1-FGFR1 fusion in 16 of 39 (41%) phosphaturic mesenchymal tumors and identified an additional case with FN1-FGF1 fusion. The two fusion genes were mutually exclusive. Combined with previous data, the overall prevalence of FN1-FGFR1 and FN1-FGF1 fusions was 42% (21/50) and 6% (3/50), respectively. FGFR1 immunohistochemistry was positive in 82% (45/55) of phosphaturic mesenchymal tumors regardless of fusion status. By contrast, 121 cases of potential morphologic mimics (belonging to 13 tumor types) rarely expressed FGFR1, the main exceptions being solitary fibrous tumors (positive in 40%), chondroblastomas (40%), and giant cell tumors of bone (38%), suggesting a possible role for FGFR1 immunohistochemistry in the diagnosis of phosphaturic mesenchymal tumor. With the exception of one case reported in our prior study, none of the remaining tumors resembling phosphaturic mesenchymal tumor had either fusion type or expressed significant FGFR1. Our findings provide insight into possible mechanisms underlying the pathogenesis of phosphaturic mesenchymal tumor and imply a central role of the FGF1-FGFR1 signaling pathway. The novel FN1-FGF1 protein is expected to be secreted and serves as a ligand that binds and activates FGFR1 to achieve an autocrine loop. Further study is required to determine the functions of these fusion proteins.

Katoh M
FGFR inhibitors: Effects on cancer cells, tumor microenvironment and whole-body homeostasis (Review).
Int J Mol Med. 2016; 38(1):3-15 [PubMed] Free Access to Full Article Related Publications
Fibroblast growth factor (FGF)2, FGF4, FGF7 and FGF20 are representative paracrine FGFs binding to heparan-sulfate proteoglycan and fibroblast growth factor receptors (FGFRs), whereas FGF19, FGF21 and FGF23 are endocrine FGFs binding to Klotho and FGFRs. FGFR1 is relatively frequently amplified and overexpressed in breast and lung cancer, and FGFR2 in gastric cancer. BCR-FGFR1, CNTRL-FGFR1, CUX1-FGFR1, FGFR1OP-FGFR1, MYO18A-FGFR1 and ZMYM2-FGFR1 fusions in myeloproliferative neoplasms are non-receptor-type FGFR kinases, whereas FGFR1-TACC1, FGFR2-AFF3, FGFR2-BICC1, FGFR2-PPHLN1, FGFR3-BAIAP2L1 and FGFR3-TACC3 fusions in solid tumors are transmembrane-type FGFRs with C-terminal alterations. AZD4547, BGJ398 (infigratinib), Debio-1347 and dovitinib are FGFR1/2/3 inhibitors; BLU9931 is a selective FGFR4 inhibitor; FIIN-2, JNJ-42756493, LY2874455 and ponatinib are pan-FGFR inhibitors. AZD4547, dovitinib and ponatinib are multi-kinase inhibitors targeting FGFRs, colony stimulating factor 1 receptor (CSF1R), vascular endothelial growth factor (VEGF)R2, and others. The tumor microenvironment consists of cancer cells and stromal/immune cells, such as cancer-associated fibroblasts (CAFs), endothelial cells, M2-type tumor-associating macrophages (M2-TAMs), myeloid-derived suppressor cells (MDSCs) and regulatory T cells. FGFR inhibitors elicit antitumor effects directly on cancer cells, as well as indirectly through the blockade of paracrine signaling. The dual inhibition of FGF and CSF1 or VEGF signaling is expected to enhance the antitumor effects through the targeting of immune evasion and angiogenesis in the tumor microenvironment. Combination therapy using tyrosine kinase inhibitors (FGFR or CSF1R inhibitors) and immune checkpoint blockers (anti-PD-1 or anti-CTLA-4 monoclonal antibodies) may be a promising choice for cancer patients. The inhibition of FGF19-FGFR4 signaling is associated with a risk of liver toxicity, whereas the activation of FGF23-FGFR4 signaling is associated with a risk of heart toxicity. Endocrine FGF signaling affects the pathophysiology of cancer patients who are prescribed FGFR inhibitors. Whole-genome sequencing is necessary for the detection of promoter/enhancer alterations of FGFR genes and rare alterations of other genes causing FGFR overexpression. To sustain the health care system in an aging society, a benefit-cost analysis should be performed with a focus on disease-free survival and the total medical cost before implementing genome-based precision medicine for cancer patients.

Tajima S, Fukayama M
Fibroblast growth factor receptor 1 (FGFR1) expression in phosphaturic mesenchymal tumors.
Int J Clin Exp Pathol. 2015; 8(8):9422-7 [PubMed] Free Access to Full Article Related Publications
Phosphaturic mesenchymal tumor (PMT) has been elucidated as a cause of tumor-induced osteomalacia (TIO) associated with mesenchymal neoplasm. TIO is associated with the production of phosphatonins, such as fibroblast growth factor 23 (FGF23), which participate in phosphate homeostasis. Fibroblast growth factor receptor 1 (FGFR1) is a known receptor of FGF23, and it was recently found that the fibronectin 1 (FN1)-FGFR1 fusion gene is present in 60% of PMT cases. Immunohistochemical evaluation of FGFR1 expression in PMT has not been reported till date. We analyzed 11 cases of PMT in this study and found that 36% of cases (4/11 cases) exhibited cytoplasmic and membranous staining with strong intensity, and 64% of cases (7/11 cases) exhibited cytoplasmic dot-like staining with moderate to weak intensity. The aforementioned 36% of cases may reflect the presence of the FN1-FGFR1 fusion gene, as the FN1 promoter enhances FGFR1 expression. Although FGFR1 signaling increases FGF23 expression in an autocrine/paracrine loop, FGF23 serum level does not correlate with FGFR1 membranous expression (staining with strong intensity). Thus, we speculate that important factors other than FGFR1 are involved in the tumor biology of PMTs overexpressing FGF23.

Green D, Dalmay T, Fraser WD
Role of miR-140 in embryonic bone development and cancer.
Clin Sci (Lond). 2015; 129(10):863-73 [PubMed] Related Publications
Bone is increasingly viewed as an endocrine organ with key biological functions. The skeleton produces hormones and cytokines, such as FGF23 and osteocalcin, which regulate an extensive list of homoeostatic functions. Some of these functions include glucose metabolism, male fertility, blood cell production and calcium/phosphate metabolism. Many of the genes regulating these functions are specific to bone cells. Some of these genes can be wrongly expressed by other malfunctioning cells, driving the generation of disease. The miRNAs are a class of non-coding RNA molecules that are powerful regulators of gene expression by suppressing and fine-tuning target mRNAs. Expression of one such miRNA, miR-140, is ubiquitous in chondrocyte cells during embryonic bone development. Activity in cells found in the adult breast, colon and lung tissue can silence genes required for tumour suppression. The realization that the same miRNA can be both normal and detrimental, depending on the cell, tissue and time point, provides a captivating twist to the study of whole-organism functional genomics. With the recent interest in miRNAs in bone biology and RNA-based therapeutics on the horizon, we present a review on the role of miR-140 in the molecular events that govern bone formation in the embryo. Cellular pathways involving miR-140 may be reactivated or inhibited when treating skeletal injury or disorder in adulthood. These pathways may also provide a novel model system when studying cancer biology of other cells and tissues.

Feng S, Wang J, Zhang Y, et al.
FGF23 promotes prostate cancer progression.
Oncotarget. 2015; 6(19):17291-301 [PubMed] Free Access to Full Article Related Publications
Prostate cancer is the most common cancer in US men and the second leading cause of cancer deaths. Fibroblast growth factor 23 (FGF23) is an endocrine FGF, normally expressed by osteocytes, which plays a critical role in phosphate homeostasis via a feedback loop involving the kidney and vitamin D. We now show that FGF23 is expressed as an autocrine growth factor in all prostate cancer cell lines tested and is present at increased levels in prostate cancer tissues. Exogenous FGF23 enhances proliferation, invasion and anchorage independent growth in vitro while FGF23 knockdown in prostate cancer cell lines decreases these phenotypes. FGF23 knockdown also decreases tumor growth in vivo. Given that classical FGFs and FGF19 are also increased in prostate cancer, we analyzed expression microarrays hybridized with RNAs from of LNCaP cells stimulated with FGF2, FGF19 or FGF23. The different FGF ligands induce overlapping as well as unique patterns of gene expression changes and thus are not redundant. We identified multiple genes whose expression is altered by FGF23 that are associated with prostate cancer initiation and progression. Thus FGF23 can potentially also act as an autocrine, paracrine and/or endocrine growth factor in prostate cancer that can promote prostate cancer progression.

Suvannasankha A, Tompkins DR, Edwards DF, et al.
FGF23 is elevated in multiple myeloma and increases heparanase expression by tumor cells.
Oncotarget. 2015; 6(23):19647-60 [PubMed] Free Access to Full Article Related Publications
Multiply myeloma (MM) grows in and destroys bone, where osteocytes secrete FGF23, a hormone which affects phosphate homeostasis and aging. We report that multiple myeloma (MM) cells express receptors for and respond to FGF23. FGF23 increased mRNA for EGR1 and its target heparanase, a pro-osteolytic factor in MM. FGF23 signals through a complex of klotho and a classical FGF receptor (FGFR); both were expressed by MM cell lines and patient samples. Bone marrow plasma cells from 42 MM patients stained positively for klotho, while plasma cells from 8 patients with monoclonal gammopathy of undetermined significance (MGUS) and 6 controls were negative. Intact, active FGF23 was increased 2.9X in sera of MM patients compared to controls. FGF23 was not expressed by human MM cells, but co-culture with mouse bone increased its mRNA. The FGFR inhibitor NVP-BGJ398 blocked the heparanase response to FGF23. NVP-BGJ398 did not inhibit 8226 growth in vitro but significantly suppressed growth in bone and induction of the osteoclast regulator RANK ligand, while decreasing heparanase mRNA. The bone microenvironment provides resistance to some anti-tumor drugs but increased the activity of NVP-BGJ398 against 8226 cells. The FGF23/klotho/heparanase signaling axis may offer targets for treatment of MM in bone.

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.

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