Inhibition of imatinib-mediated apoptosis by the caspase-cleaved form of the tyrosine kinase Lyn in chronic myelogenous leukemia cells

Leukemia. 2009 Aug;23(8):1500-6. doi: 10.1038/leu.2009.60. Epub 2009 Apr 2.

Abstract

Once cleaved by caspases, the Lyn tyrosine kinase (LynDeltaN) is relocalized from the plasma membrane to the cytoplasm of apoptotic cells, but the function of such a cleavage is incompletely understood. We evaluated the effect of LynDeltaN overexpression on imatinib sensitivity of the chronic myelogenous leukemia (CML) cell line K562. Therefore, we generated stable cells that express plasmids encoding LynDeltaN or its catalytically inactive counterpart LynDeltaNKD. We established that Lyn is cleaved in imatinib-treated parental K562 cells in a caspase-dependent manner. Lyn cleavage also occurred following BCR-ABL silencing by specific short hairpin RNA (sh-RNA). Imatinib-induced apoptosis was abrogated in LynDeltaN-overexpressing cells, but not in cells overexpressing its inactive counterpart. Conversely, the overexpression of LynDeltaN failed to affect the differentiation of K562 cells. Importantly, the protective effect of LynDeltaN was suppressed by two inhibitors of Lyn activity. LynDeltaN also inhibits imatinib-mediated caspase-3 activation in the small proportion of nilotinib-resistant K562 cells overexpressing Lyn that can engage an apoptotic program upon imatinib stimulation. Finally, Lyn knockdown by sh-RNA altered neither imatinib-mediated apoptosis nor differentiation. Taken together, our data show that the caspase-cleaved form of Lyn exerts a negative feedback on imatinib-mediated CML cell apoptosis that is entirely dependent on its kinase activity and likely on the BCR-ABL pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / antagonists & inhibitors*
  • Antineoplastic Agents / pharmacology
  • Apoptosis / drug effects*
  • Benzamides
  • Caspase 3 / metabolism*
  • Caspase 9 / genetics
  • Caspase 9 / metabolism*
  • Caspase Inhibitors
  • Enzyme Activation
  • Erythropoiesis / drug effects
  • Fusion Proteins, bcr-abl / antagonists & inhibitors
  • Fusion Proteins, bcr-abl / physiology
  • Humans
  • Imatinib Mesylate
  • Indoles / pharmacology
  • K562 Cells / drug effects
  • K562 Cells / enzymology
  • K562 Cells / pathology
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / enzymology*
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / pathology
  • Neoplasm Proteins / antagonists & inhibitors
  • Neoplasm Proteins / chemistry
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / physiology*
  • Piperazines / antagonists & inhibitors*
  • Protein Kinase Inhibitors / antagonists & inhibitors*
  • Protein Kinase Inhibitors / pharmacology
  • Pyrimidines / antagonists & inhibitors*
  • Pyrimidines / pharmacology
  • RNA Interference
  • RNA, Small Interfering / pharmacology
  • Recombinant Fusion Proteins / physiology
  • Signal Transduction / drug effects
  • Structure-Activity Relationship
  • Sulfonamides / pharmacology
  • src-Family Kinases / antagonists & inhibitors
  • src-Family Kinases / chemistry
  • src-Family Kinases / genetics
  • src-Family Kinases / physiology*

Substances

  • AG 1879
  • Antineoplastic Agents
  • Benzamides
  • Caspase Inhibitors
  • Indoles
  • Neoplasm Proteins
  • Piperazines
  • Protein Kinase Inhibitors
  • Pyrimidines
  • RNA, Small Interfering
  • Recombinant Fusion Proteins
  • SU 6656
  • Sulfonamides
  • Imatinib Mesylate
  • Fusion Proteins, bcr-abl
  • lyn protein-tyrosine kinase
  • src-Family Kinases
  • CASP3 protein, human
  • Caspase 3
  • Caspase 9