Abstract: Objective To evaluate the role of Fibroblast growth factor 23 (FGF-23), matrix extracellular phosphoglycoprotein (MEPE) and secreted Frizzled related protein 4 (sFRP4) in pathogenesis of Tumor induced osteomalacia (TIO). Methods The mRNA expressions of FGF23, MEPE and sFRP4 were detected in 8 TIO tumors (T1-T8), 5 other mesenchymal tumors(C1-C5), 2 normal bone tissues(B1-B2), 2 normal muscle tissues(M1-M2), blood clotting and necrostic tissue of bone in a patient of hypophospatemic osteomalacia but not TIO (P1) using RT-PCR. The FGF23 protein expressions were analyzed in 8 TIO tumors using Western blot. Serum FGF23 (ELISA) and phosphate were measured before and after operation in 4 TIO (T1、3、4、7) and P1 patients. Results The mRNA of FGF23 and MEPE were expressed in TIO tumors abundantly. Some TIO tumors expressed sRP4 mRNA. 7/8 TIO tumors expressed various FGF23 protein in Western blot. Serum FGF23 in TIO patients were elevated, and went down after tumor resections in 2～24 hrs. The increase of serum phosphate was slower than FGF23 degression (in 3～10 days). Serum FGF23 was stably high in P1 patient without serum phosphate elevation. The expressions of FGF23 and MEPE mRNA were related (r＝0.884，P＜0.05). There was a positive relationship between FGF23 mRNA and protein expression (r＝0.921，P＜0.05). Conclusions FGF23 plays an important role in pathogenesis of TIO. MEPE may be involved in pathogenesis of TIO. The role of sFRP4 in pathogenesis of TIO is still need to be explored.

Key words: tumor induced osteomalacia, fibroblast growth factor 23, matrix extracellular phosphoglycoprotein, secreted frizzled related protein 4