Using the recombinant IL-2 diphtheria toxin conjugate DAB(389)IL-2 (also known as denileukin diftitox and ONTAK), Dannull et al. demonstrated that DAB(389)IL-2 was capable of selectively eliminating CD25+  TReg cells from the PBMCs of cancer patients without inducing toxicity on other cellular subsets, and DAB(389)IL-2-mediated TReg depletion enhanced anti-tumor immune responses and significantly reduced the number of TReg cells present in the blood of cancer patients [48]. This evidence concerns the gene IL2 and cancer.