melanoma cells. By expanding the current armamentarium of AC inhibitors, these results should facilitate future efforts to unravel the biology of AC and the therapeutic potential of its inhibition. Acid ceramidase (AC) is a lysosomal cysteine amidase responsible for the cleavage of ceramide into sphingosine, which is then phosphorylated to sphingosine 1-phosphate. AC regulates the intracellular levels