MicroRNA expression in a phosphaturic mesenchymal tumour

Case Report: Unexplained Mild Hypophosphatemia and Very High Serum FGF23 Concentrations

Fibroblast growth factor (FGF)23 is one of the major regulators of phosphate homeostasis. Hypophosphatemia can lead to muscle weakness, fatigue, and osteomalacia. In the setting of hypophosphatemia, serum FGF23 can be measured to differentiate between FGF23-mediated and non-FGF23-mediated renal phosphate wasting. C-terminal FGF23 (cFGF23) assays detect both cFGF23 and intact FGF23 (iFGF23). Circulating FGF23 is regulated by 1.25-dihydroxy-vitamin D, parathyroid hormone (PTH), serum phosphate, and serum calcium but also by, for example, iron status, inflammation, erythropoietin, and hypoxia-inducible-factor-1-α. We present the case of a 48-year-old woman with unexplained mild hypophosphatemia, very high cFGF23, and normal iFGF23. The patient proved to have an iron deficiency. Iron deficiency alters the iFGF23-to-cFGF23 ratio. After initiation of iron treatment, cFGF23 strongly decreased. This case report illustrates the limitation of cFGF23 assays and urges clinicians to be aware that cFGF23 concentrations do not necessarily reflect iFGF23 concentrations and that alternative causes for its elevation should be considered (eg, iron deficiency). © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

A Normal FGF23 Does Not Preclude Tumor-Induced Osteomalacia

Tumor-induced osteomalacia (TIO) is a rare cause of impaired bone mineralization mediated by the osteocyte-derived, phosphaturic hormone: fibroblast growth factor 23 (FGF23). The case is presented of a previously healthy 45-year-old man who developed fragility fractures at multiple sites (initially metatarsals, eventually ribs, hips, spine, scapula, and sacrum) resulting in rapid functional deterioration, weakness, and the inability to bear weight and ambulate without a walker. Workup for secondary causes of bone loss was negative except for mild hypogonadotropic hypogonadism with normal pituitary MRI and hypophosphatemia that persisted despite aggressive supplementation. Testosterone was initiated but discontinued 6 months later because of deep vein thrombosis and pulmonary embolism, likely provoked by his new sedentary state, in addition to smoking history and possibly testosterone usage. Serum FGF23 was nonelevated at 138 mRU/mL (44-215). A genetic panel for OI variants was negative for a causal mutation. At the age of 48, 3 years after his initial fracture, he was referred to our academic endocrine clinic. We ruled out additional mutations that lead to hypophosphatemic rickets, including phosphate-regulating endopeptidase homolog, X-linked. PET/CT looking for a potential TIO locus revealed uptake in the left suprapatellar recess. Biopsy was consistent with a phosphaturic mesenchymal tumor. FGF23 was repeated for a preoperative baseline and now found to be elevated at 289 mRU/mL. In retrospect, it is likely that the initial level was inappropriately elevated for the degree of hypophosphatemia. After resection, he experienced marked improvement in physical function, decreased pain, and resolution of renal phosphate wasting. The principals of establishing a robust clinical diagnosis of TIO should be emphasized, excluding other entities and avoiding pitfalls in the interpretation of laboratory testing. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Risk Factors Associated With Altered Circulating Micro RNA -125b and Their Influences on Uremic Vascular Calcification Among Patients With End-Stage Renal Disease

Background

MicroRNA‐125b (miR‐125b) has been shown to regulate vascular calcification (VC), and serum miR‐125b levels are a potential biomarker for estimating the risk of uremic VC status. However, it is unknown whether clinical features, including chronic kidney disease–mineral bone disorder molecules, affect serum miR‐125b levels.

Methods and Results

Patients receiving chronic dialysis for ≥3 months were recruited from different institutes. Serum miR‐125b and chronic kidney disease–mineral bone disorder effectors, including intact parathyroid hormone, 25‐OH‐D, fibroblast growth factor‐23, osteoprotegerin, and fetuin‐A, were quantified. We used multivariate regression analyses to identify factors associated with low serum miR‐125b levels and an area under receiver operating characteristic curve curve to derive optimal cutoffs for factors exhibiting close associations. Further regression analyses evaluated the influence of miR‐125b on VC risk. Among 223 patients receiving chronic dialysis (mean age, 67.3 years; mean years of dialysis, 5.2), 54 (24.2%) had high serum miR‐125b levels. Osteoprotegerin (P=0.013), fibroblast growth factor‐23 (P=0.006), and fetuin‐A (P=0.036) were linearly associated with serum miR‐125b levels. High osteoprotegerin levels independently correlated with high serum miR‐125 levels. Adding serum miR‐125b levels and serum osteoprotegerin levels (≥400 pg/mL) into models estimating the risk of uremic VC increased the area under receiver operating characteristic curve values (for models without miR‐125b/osteoprotegerin, with miR‐125b, and both: 0.74, 0.79, and 0.81, respectively).

Conclusions

Serum osteoprotegerin levels ≥400 pg/mL and serum miR‐125b levels synergistically increased the accuracy of estimating VC risk among patients receiving chronic dialysis. Taking miR‐125b and osteoprotegerin levels into consideration when estimating VC risk may be recommended.

Competitive endogenous RNA network identifies four long non-coding RNA signature as a candidate prognostic biomarker for lung adenocarcinoma

BACKGROUND

Lung adenocarcinoma (LUAD) is the most commonly histological subtype of lung cancer (LC) and the prognoses of the majority of LUAD patients are still very poor. The present study aimed at integrating long non-coding RNA (lncRNA), microRNA (miRNA) and messenger RNA (mRNA) expression data to construct lncRNA-miRNA-mRNA competitive endogenous RNA (ceRNA) network and identify importantly potential lncRNA signature in ceRNA network as a candidate prognostic biomarker for LUAD patients.

METHODS

lncRNA, miRNA and mRNA expression data as well as clinical characteristics of LUAD patients were retrieved from The Cancer Genome Atlas (TCGA) database. Differentially expressed lncRNAs (DElncRNAs), differentially expressed mRNAs (DEmRNAs) and differentially expressed miRNA (DEmiRNA) between LUAD and normal lung tissues samples were analyzed. A lncRNA-miRNA-mRNA ceRNA network was constructed and the biological functions of DEmRNAs in ceRNA network were analyzed using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Univariate and multivariate Cox regression analyses of DElncRNAs in ceRNA network were implemented to predict the overall survival (OS) in LUAD patients. The receiver operating characteristic (ROC) analysis was used to evaluate the performance of multivariate Cox regression model.

RESULTS

A total of 1,664 DElncRNAs, 120 DEmiRNAs and 2,503 DEmRNAs was identified between LUAD and normal lung tissues samples. A lncRNA-miRNA-mRNA ceRNA network including 140 DElncRNAs, 33 DEmiRNAs and 57 DEmRNAs was established. Kaplan-Meier (KM) [Log-rank (LR) test] and univariate regression analysis of those 140 DElncRNAs revealed that 7 DElncRNAs (LINC00518, UCA1, NAV2-AS2, MED4-AS1, SYNPR-AS1, AC011483.1, AP002478.1) were simultaneously identified to be associated with OS of LUAD patients. A multivariate Cox regression analysis of those 7 DElncRNAs showed that a group of 4 DElncRNAs including AP002478.1 (Cox P=4.66E-03), LINC00518 (Cox P=2.34E-04), MED4-AS1 (Cox P=6.42E-03) and NAV2-AS2 (Cox P=6.66E-02) had significantly prognostic value in OS of LUAD patients. The cumulative risk score indicated that the 4-lncRNA signature was significantly associated with OS of LUAD patients (P=0). The area under the curve (AUC) of the 4-lncRNA signature related with 3-year survival was 0.669.

CONCLUSIONS

The present study provides novel insights into the lncRNA-related regulatory mechanisms in LUAD, and identifying 4-lncRNA signature may serve as a candidate prognostic biomarker in predicting the OS of LUAD patients.