Our data obtained in acid sphingomyelinase-deficient mice that were injected with Pan02 pancreas carcinoma cells suggests that not only the expression of the acid sphingomyelinase in tumor cells, but also the expression of the acid sphingomyelinase in host cells is mostly important for tumor progression, since in our orthotopic tumor model in knock-out mice, the acid sphingomyelinase is deficient in host cells, but not in the malignant tumor cells. The gene discussed is SMPD1; the disease is neoplasm.