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. This evidence concerns the gene HDAC2 and chronic myelogenous leukemia, BCR-ABL1 positive.