Lyn regulates BCR-ABL and Gab2 tyrosine phosphorylation and c-Cbl protein stability in imatinib-resistant chronic myelogenous leukemia cells.
Lyn kinase functions as a regulator of imatinib sensitivity in chronic myelogenous leukemia (CML) cells through an unknown mechanism. In patients who fail imatinib therapy but have no detectable BCR-ABL kinase mutation, we detected persistently activated Lyn kinase. In imatinib-resistant CML cells and patients, Lyn activation is BCR-ABL independent, it is complexed with the Gab2 and c-Cbl adapter/scaffold proteins, and it mediates persistent Gab2 and BCR-ABL tyrosine phosphorylation in the presence or absence of imatinib. Lyn silencing or inhibition is necessary to suppress Gab2 and BCR-ABL phosphorylation and to recover imatinib activity. Lyn also negatively regulates c-Cbl stability, whereas c-Cbl tyrosine phosphorylation is mediated by BCR-ABL. These results suggest that Lyn exists as a component of the BCR-ABL signaling complex and, in cells with high Lyn expression or activation, BCR-ABL kinase inhibition alone (imatinib) is not sufficient to fully disengage BCR-ABL-mediated signaling and suggests that BCR-ABL and Lyn kinase inhibition are needed to prevent or treat this form of imatinib resistance.
Pubmed ID: 18235045 RIS Download
Adaptor Proteins, Signal Transducing | Benzamides | Drug Resistance, Neoplasm | Enzyme Activation | Fusion Proteins, bcr-abl | Gene Silencing | Humans | Imatinib Mesylate | K562 Cells | Leukemia, Myelogenous, Chronic, BCR-ABL Positive | Multiprotein Complexes | Mutation | Phosphorylation | Piperazines | Protein Kinase Inhibitors | Proto-Oncogene Proteins c-cbl | Pyrimidines | Signal Transduction | src-Family Kinases