SPHK1 and breast cancer: S1P is known to regulate various cellular processes that are involved in cancer: SphK1 maintains tumor cell survival and promotes the progression of hormone-independent prostate and breast cancer [19, 20]; SphK1 overexpression stimulates Ras-dependent mechanisms that transform fibroblasts into fibrosarcoma; in estrogen receptor-positive breast cancer, high tumoral SphK1 expression is associated with poorer survival and shorter times to disease recurrence; and S1P promotes tumor neovascularization and induces inflammation involved in cancer progression [21].