SPHK1 and breast cancer: It has been indicated that miR-515-5p can directly bind to 3′ UTR of sphingosine kinase 1 to inhibit breast cancer cell proliferation.29 Moreover, in non-small cell lung cancer, miR-515-5p was found to suppress cell migration, survival and metastasis by directly targeting MARK4 and CXCL6 respectively.30,31 These studies suggest that miR-515-5p may an effective biomarker in cancer therapy.