Contributions of MET activation to BCR-ABL1 tyrosine kinase inhibitor resistance in chronic myeloid leukemia cells.

Resistance to the breakpoint cluster region-abelson 1 (BCR-ABL1) tyrosine kinase inhibitor (TKI) imatinib poses a major problem when treating chronic myeloid leukemia (CML). Imatinib resistance often results from a secondary mutation in BCR-ABL1. However, in the absence of a mutation in BCR-ABL1, the basis of BCR-ABL1-independent resistance must be elucidated. To gain insight into the mechanisms of BCR-ABL1-independent imatinib resistance, we performed an array-based comparative genomic hybridization. We identified various resistance-related genes, and focused on MET. Treatment with a MET inhibitor resensitized K562/IR cells to BCR-ABL1 TKIs. Combined treatment of K562/IR cells with imatinib and a MET inhibitor suppressed extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) activation, but did not affect AKT activation. Our findings implicate the MET/ERK and MET/JNK pathways in conferring resistance to imatinib, providing new insights into the mechanisms of BCR-ABL1 TKI resistance in CML.