The mechanism of imatinib resistance in the CML-iPSCs. (A) The expression profile of BCR-ABL transcript during hematopoietic differentiation. The expression levels of BCR-ABL in the CML-iPSCs were compared with those of primary CML samples (CML_1 and CML_2), CML-iPSC–derived CD34⁺ hematopoietic cells (CML-HC_1 and CML-HC_2), and normal iPSC (nor-iPS). The expression level of the mean in the primary CML sample was set at 1. (B) BCR-ABL signaling was estimated in the CML-iPSCs after imatinib (IM) treatment. The phosphorylation state of ERK1/2, AKT, JNK, and STAT5, which are the essential for the survival of BCR-ABL (+) hematopoietic progenitors (CD34⁺CD45⁺), were evaluated after imatinib treatment in CML-iPSCs. These were the representative data from 3 independent experiments. (C-D) LY294002 and U0126 (10μM) were added to the culture of CML iPSCs to inhibit AKT and ERK, respectively with or without imatinib. (C) After 4 hours of culture, each inhibitor decreased the phosphorylation of ERK or AKT as expected. (D) The attached cell numbers after treatment with specific AKT or ERK inhibitor were shown. These were the representative data from 3 independent experiments.