ENPP2 and neoplasm: In an SMase-independent manner, sphingomyelin can be degraded into sphingosylphosphorylcholine (SPC) and then further transformed into S1P by the actions of sphingomyelin deacylase and autotaxin (ATX), the latter of which is an ectonucleotide pyrophosphatase (phosphodiesterase with lysophospholipase D activity), originally identified as a tumor-regulatory factor for survival and proliferation14,15.