SPHK1 and cancer: Not only has elevated SPHK1 in cancer tissues been implicated in disease progression, but systemic SPHK1 has been implicated in promoting metastasis through a feedback mechanism whereby systemic S1P, signalling through tumour cell S1P2 receptors, suppresses the expression of the protein breast carcinoma metastasis suppressor 1, which inhibits metastasis [100].