As part of its antitumoral action in leukaemic cells, APL inhibits the activity of ornithine decarboxylase (ODC), an enzyme responsible for polyamine biosynthesis and involved in cellular transformation (Paasinen-Sohns and Holtta, 1997; Erba et al, 1999; Iwata et al, 1999), and causes a reduction in vascular endothelial growth factor (VEGF) secretion and downregulation of its receptor, VEGFR-1 (flt-1), involved in the process of vascularisation and growth of certain tumours (Taraboletti et al, 2002; Broggini et al, 2003). This evidence concerns the gene ODC1 and neoplasm.