This is most likely due to the known bystander effect of TRAIL expression: because TRAIL is cell surface‐bound ligand, it can affect neighboring cells, thereby causing apoptosis in more cells than were initially transfected.26 Conversely, the melanoma, breast cancer, and brain cancer cell lines used in this study showed lower TRAIL‐mediated killing rates than their transfection efficacy, indicating resistance to TRAIL. This evidence concerns the gene TNFSF10 and breast carcinoma.