Recombinant human IL-2 (rhIL-2, 15 kDa) produced in E. coli and refolded in vitro was included in all the in vivo experiments as an additional control because it is a well-characterized protein commonly used in our laboratory for this kind of experiment and known to have anti-tumor activity10, but its effects are not directly comparable to the ones exerted by the fusion protein. This evidence concerns the gene IL2 and neoplasm.