S1PR1 and breast cancer: Moreover, FTY720, which is phosphorylated to form FTY720-phosphate and, in turn, is an agonist of four sphingosine-1-phosphate receptors, induces growth arrest and apoptosis in leukaemia, bladder, prostate, breast cancer, and glioma cells and prevents tumour growth and metastasis in mouse breast cancer cells in vitro and in vivo [162–165,167].