A Bcr/Abl-independent, Lyn-dependent form of imatinib mesylate (STI-571) resistance is associated with altered expression of Bcl-2

J Biol Chem. 2004 Aug 13;279(33):34227-39. doi: 10.1074/jbc.M402290200. Epub 2004 Jun 2.

Abstract

The relationship between the Src kinase Lyn and Bcl-2 expression was examined in chronic myelogenous leukemia cells (K562 and LAMA84) displaying a Bcr/Abl-independent form of imatinib mesylate resistance. K562-R and LAMA-R cells that were markedly resistant to induction of mitochondrial dysfunction (e.g. loss of mitochondrial membrane potential, Bax translocation, cytochrome c, and apoptosis-inducing factor release) and apoptosis by imatinib mesylate exhibited a pronounced reduction in expression of Bcr/Abl, Bcl-x(L), and STAT5 but a striking increase in levels of activated Lyn. Whereas basal expression of Bcl-2 protein was very low in parental cells, imatinib-resistant cells displayed a marked increase in Bcl-2 mRNA and/or protein levels. Treatment of LAMA-R cells with the Src kinase inhibitor PP2 significantly reduced Lyn activation as well as Bcl-2 mRNA and protein levels. Transient or stable transfection of LAMA84 or K562 cells with a constitutively active Lyn (Y508F), but not with a kinase-dead mutant (K275D), significantly increased Bcl-2 protein expression and protected cells from lethality of imatinib mesylate. Ectopic expression of Bcl-2 protected K562 and LAMA84 cells from imatinib mesylate- and PP2-mediated lethality. Conversely, interference with Bcl-2 function by co-administration of the small molecule Bcl-2 inhibitor HA14-1 or down-regulation of Bcl-2 expression by small interfering RNA or antisense strategies significantly increased mitochondrial dysfunction and apoptosis induced by imatinib mesylate and the topoisomerase inhibitor VP-16 in LAMA-R cells. In marked contrast, these interventions had little effect in parental LAMA84 cells that display low basal levels of Bcl-2. Together, these findings indicate that activation of Lyn in leukemia cells displaying a Bcr/Abl-independent form of imatinib mesylate resistance plays a functional role in Bcl-2 up-regulation and provide a theoretical basis for the development of therapeutic strategies targeting Bcl-2 in such a setting.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Apoptosis
  • Apoptosis Inducing Factor
  • Benzamides
  • Blotting, Western
  • Cell Line
  • Cell Line, Tumor
  • Coloring Agents / pharmacology
  • Cytochromes c / metabolism
  • DNA, Complementary / metabolism
  • DNA-Binding Proteins / metabolism
  • Dose-Response Relationship, Drug
  • Down-Regulation
  • Drug Resistance, Neoplasm*
  • Enzyme Inhibitors / pharmacology
  • Flavoproteins / metabolism
  • Flow Cytometry
  • Fusion Proteins, bcr-abl / metabolism*
  • Humans
  • Imatinib Mesylate
  • K562 Cells
  • Membrane Potentials
  • Membrane Proteins / metabolism
  • Milk Proteins*
  • Mitochondria / metabolism
  • Mutation
  • Piperazines / pharmacology*
  • Protein Transport
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • Pyrimidines / pharmacology*
  • RNA Interference
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • STAT5 Transcription Factor
  • Tetrazolium Salts / pharmacology
  • Thiazoles / pharmacology
  • Trans-Activators / metabolism
  • Transfection
  • Up-Regulation
  • bcl-2-Associated X Protein
  • bcl-X Protein
  • src-Family Kinases / metabolism*

Substances

  • AG 1879
  • AIFM1 protein, human
  • Apoptosis Inducing Factor
  • BAX protein, human
  • BCL2L1 protein, human
  • Benzamides
  • Coloring Agents
  • DNA, Complementary
  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • Flavoproteins
  • Membrane Proteins
  • Milk Proteins
  • Piperazines
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • Pyrimidines
  • RNA, Messenger
  • STAT5 Transcription Factor
  • Tetrazolium Salts
  • Thiazoles
  • Trans-Activators
  • bcl-2-Associated X Protein
  • bcl-X Protein
  • Imatinib Mesylate
  • Cytochromes c
  • Fusion Proteins, bcr-abl
  • lyn protein-tyrosine kinase
  • src-Family Kinases
  • thiazolyl blue