To exploit a ligand-direct approach, asparagine–glycine–arginine–human tumour necrosis factor (NGR–hTNF) has been genetically engineered by coupling the N-terminus of hTNF-α with the C-terminus of a tumour-homing NGR-peptide, which is a ligand of the aminopeptidase N (CD13) overexpressed by endothelial cells of newly formed human tumour blood vessels (Curnis et al, 2000; Corti and Ponzoni, 2004). This evidence concerns the gene RTN4R and neoplasm.