In addition, the anti-metabolite cancer drug, 6-mercaptopurine used to treat leukemia, could induce NR4A2 and NR4A3 through binding to AF-1 domain at the N-terminal of the latter; however, how it induced NR4A2 remains to be further researched (Ordentlich et al., 2003). This evidence concerns the gene NR4A2 and leukemia.