SMPD1 and neoplasm: To further prove the notion that a downregulation of the acid sphingomyelinase in the tumor tissue regulates tumor progression and to discriminate the role of the acid sphingomyelinase in malignant vs. non-malignant tumor cells in PDAC progression, we established orthotopic pancreas cancers in wild-type mice and in acid sphingomyelinase-deficient mice.