Sphingosine-1-phosphate / sphingosine-1-phosphate receptor 2 signaling induces COX-2 expression in Wilms tumor

Purpose—Cyclooxygenase-2 (COX-2) has been reported to be ubiquitously expressed in Wilms tumor, the most common malignant renal tumor in children. However, the regulation mechanism of COX-2 expression remains unexplored. Materials and Methods—Quantitative real-time PCR and western blot analysis were performed to detect COX-2 mRNA and protein expression in WiT49 cells upon the stimulation by sphingosine-1-phosphate (S1P) as well as S1P2 and COX-2 mRNA expression in 10 fresh frozen Wilms tumor tissues and their matched normal tissues. Overexpression, blockade and downregulation of S1P2 were performed using adenoviral transduction, S1P2 antagonist JTE-013 and siRNA transfection, respectively. The level of prostaglandin E2 (PGE2) in WiT49 cells was determined by gas chromatography/mass spectrometry. Results—S1P induced COX-2 mRNA and protein expression in WiT49 cells in a concentrationdependent manner. Overexpression of S1P2 in WiT49 cells led to a significant increase in COX-2 mRNA and protein expression as well as subsequent PGE2 synthesis. In addition, pretreatment of those cells overexpressing S1P2 with S1P2 selective antagonist JTE-013 completely blocked S1Pinduced COX-2 protein expression. In accordance with these results, silencing of S1P2 in WiT49 cells downregulated S1P-induced COX-2 expression. Further research on 10 Wilms tumor specimens found that S1P2 mRNA was greatly increased in Wilms tumor. Conclusions—S1P induced COX-2 expression in Wilms tumor, and this effect was mediated by S1P2. This finding extends the biological function of S1P2 and provides the biochemical basis for the development of inhibitors targeting S1P/COX-2 signaling pathway.