Due to their structural similarity to the sphingoid bases,FBs interfere with the de novo biosynthesis of ceramideand sphingolipid metabolism by specifically inhibiting sph-ingosine N-acyltransferase (ceramide synthase). Ceramidesynthase inhibition leads to accumulation of the sphingoidbases (sphinganine and sphingosine) in tissues that exert proapoptotic, cytotoxic, and growth inhibitory effects [40].