Here we show by analysis of tumor cross-sections doubly-immunostained with antibody to the endothelial selective cell surface marker MECA-32 (blue in Fig. 5A) and TUNEL for apoptosis (brown in Fig. 5A) that restoration of ASMase expression via Ad5H2E-PPE1(3x)-ASMase in endothelium of tumors transplanted in asmase−/− mice restores IR-induced apoptosis. This evidence concerns the gene SMPD1 and neoplasm.