Distant metastasis is one of the main obstacles to cancer treatment.Overexpression of S1PR1 in malignant tumors enhances cell invasion and migration activity,mediates EMT and induces lymphangiogenesis and angiogenesis via activation of its downstream signaling pathways,eventually results in the occurrence of tumor metastasis.S1PR1 is also closely related to generation of acquired radiotherapy resistance.This article discusses the roles of S1PR1 in tumor metastasis and radiotherapy resistance.