S1PR1 and osteosarcoma: Our data (in vitro, enzymatic assessment of SphK1 activity in tumors and SphK1 and/or S1P1 expression in tissues) suggest that SphK1/S1P signaling might represent a potential target to investigate in osteosarcoma patients, considering that the therapeutic drug FTY720 (also known as fingolimod, and marketed by Novartis as GilenyaTM) is already used in clinic for multiple sclerosis and is now being considered for repurposing in cancer.