Transformation-Associated Changes in Sphingolipid Metabolism Sensitize Cells to Lysosomal Cell Death Induced by Inhibitors of Acid Sphingomyelinase

• Lysosomal ASM is an essential target of siramesine’s anticancer action
• Many clinically relevant drugs that inhibit ASM display potent anticancer activity
• ASM inhibition enhances lysosomal cell death and reduces multidrug resistance
• Altered sphingomyelin metabolism renders cancer cells sensitive to ASM inhibition

SummaryLysosomal membrane permeabilization and subsequent cell death may prove useful in cancer treatment, provided that cancer cell lysosomes can be specifically targeted. Here, we identify acid sphingomyelinase (ASM) inhibition as a selective means to destabilize cancer cell lysosomes. Lysosome-destabilizing experimental anticancer agent siramesine inhibits ASM by interfering with the binding of ASM to its essential lysosomal cofactor, bis(monoacylglycero)phosphate. Like siramesine, several clinically relevant ASM inhibitors trigger cancer-specific lysosomal cell death, reduce tumor growth in vivo, and revert multidrug resistance. Their cancer selectivity is associated with transformation-associated reduction in ASM expression and subsequent failure to maintain sphingomyelin hydrolysis during drug exposure. Taken together, these data identify ASM as an attractive target for cancer therapy.