To confirm that the tumor growth inhibition induced by TRAIL-ATNCIL4rP was driven by its apoptosis-promoting activity, we used terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining to analyze apoptosis in tumor tissues from the mice that were treated as described above and euthanized on day 21 after the first injection. The gene discussed is TNFSF10; the disease is neoplasm.