SMPD1 and neoplasm: Similar to BAEC, tumor endothelial cells isolated to homogeneity showed rapid ASMase activation (not shown) and formation of platforms enriched in ceramide (Fig. 1) in 40±4% of the total population at 2 min post 15 Gy (the 50% tumor control dose for MCA/129 fibrosarcomas), compared to 11±3% of unstimulated controls (P<0.05).