Imatinib inhibits proliferation of Ewing tumor cells mediated by the stem cell factor/KIT receptor pathway, and sensitizes cells to vincristine and doxorubicin-induced apoptosis

Clin Cancer Res. 2004 Jan 15;10(2):751-61. doi: 10.1158/1078-0432.ccr-0778-03.

Abstract

Purpose and experimental design: The stem cell factor/KIT receptor loop may represent a novel target for molecular-based therapies of Ewing tumor. We analyzed the in vitro impact of KIT blockade by imatinib in Ewing tumor cell lines.

Results: KIT expression was detected in 4 of 4 Ewing tumor cell lines and in 49 of 110 patient samples (44.5%) by immunohistochemistry and/or Western blot analysis. KIT expression was stronger in Ewing tumors showing EWS-FLI1 nontype 1 fusions. Despite absence of c-kit mutations, constitutive and ligand-inducible phosphorylation of KIT was found in all tumor cell lines, indicating an active receptor. Treatment with KIT tyrosine kinase inhibitor imatinib (0.5-20 micro M) induced down-regulation of KIT phosphorylation and dose response inhibition of cell proliferation (IC(50), 12-15 micro M). However, imatinib administered alone at doses close to IC(50) for growth inhibition (10 micro M) did not induce a significant increase in apoptosis. We then analyzed if blockade of KIT loop through imatinib (10 micro M) was able to increase the antitumor in vitro effect of doxorubicin (DXR) and vincristine (VCR), drugs usually used in Ewing tumor treatment. Addition of imatinib decreased in 15-20 and 15-36% of the proliferative rate of Ewing tumor cells exposed to DXR and VCR, respectively, and increased in 15 and 30% of the apoptotic rate of Ewing tumor cells exposed to the same drugs.

Conclusions: Inhibition of Ewing tumor cell proliferation by imatinib is mediated through blockade of KIT receptor signaling. Inhibition of KIT increases sensitivity of these cells to DXR and VCR. This study supports a potential role for imatinib in the treatment of Ewing tumor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibiotics, Antineoplastic / pharmacology
  • Antineoplastic Agents / pharmacology
  • Antineoplastic Agents, Phytogenic / pharmacology
  • Apoptosis*
  • Benzamides
  • Blotting, Western
  • Bone Neoplasms / drug therapy*
  • Cell Division
  • Cell Line, Tumor
  • Dose-Response Relationship, Drug
  • Doxorubicin / pharmacology*
  • Enzyme Inhibitors / pharmacology
  • Flow Cytometry
  • Humans
  • Imatinib Mesylate
  • Immunohistochemistry
  • Indicators and Reagents / pharmacology
  • Inhibitory Concentration 50
  • Ligands
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases / metabolism
  • Phosphorylation
  • Piperazines / pharmacology*
  • Precipitin Tests
  • Propidium / pharmacology
  • Proto-Oncogene Proteins c-kit / metabolism
  • Pyrimidines / pharmacology*
  • RNA, Messenger / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sarcoma, Ewing / drug therapy*
  • Signal Transduction
  • Stem Cell Factor / biosynthesis*
  • Vincristine / pharmacology*

Substances

  • Antibiotics, Antineoplastic
  • Antineoplastic Agents
  • Antineoplastic Agents, Phytogenic
  • Benzamides
  • Enzyme Inhibitors
  • Indicators and Reagents
  • Ligands
  • Piperazines
  • Pyrimidines
  • RNA, Messenger
  • Stem Cell Factor
  • Propidium
  • Vincristine
  • Doxorubicin
  • Imatinib Mesylate
  • Proto-Oncogene Proteins c-kit
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Mitogen-Activated Protein Kinases