As suggested in previous studies, the over-expression of HDACs is an obvious mechanism that results in the drug resistance of leukemia.16,17 Furthermore, HDAC2 has been reported to be highly expressed in K562-R cells resistant to IM as compared to K562 cells sensitive to IM, indicating that HDAC2 may play a critical role in developing IM resistance.20 Previous studies suggest that CAY10683 combined with IM treatment reverses the IM resistance of CML. The gene discussed is HDAC2; the disease is leukemia.