FGF23 and osteosarcoma: To gain further insight into the signal transduction pathway(s) employed by 1,25(OH)2D/VDR to induce FGF23, the kinetics of FGF23 mRNA enhancement by 1,25(OH)2D in UMR‐106 osteosarcoma cells (a cell line that exhibits osteocyte‐like character) was compared with that of other vitamin D‐induced genes such as cyp24a1 (Fig. S1A).