SPHK1 and ovarian cancer: Immunoblotting of whole cell lysates (WCLs) and EVs isolated from four ovarian cancer cell lines (HeyA8, OVCAR5, NIH‐OVCAR3, and OVCAR4) demonstrated that SPHK1 isoform 2 was highly expressed in the secreted EVs compared to the WCLs of all four cell lines (Figure1A).