• Marc Hotfilder, Claudia Lanvers, Heribert Jürgens, Joachim Boos, and Josef Vormoor.
• University Children's Hospital Muenster, Department of Pediatric Hematology and Oncology, University of Muenster, Albert-Schweitzer-Str. 33, 48129 Muenster, Germany.
• Cancer Chemother. Pharmacol. 2002 Aug 1; 50 (2): 167-9.

PurposeIn order to determine whether Ewing tumour patients may be potential candidates for imatinib mesylate therapy, we analysed the expression of the currently known imatinib mesylate-sensitive tyrosine kinases and tested sensitivity to imatinib mesylate in a panel of eight Ewing tumour cell lines in vitro.MethodsExpression of the different tyrosine kinases was assessed by flow cytometry and RT-PCR. Sensitivity to imatinib mesylate was analysed using a standard MTT proliferation assay.ResultsFlow cytometric and RT-PCR analyses in a panel of eight Ewing tumour cell lines demonstrated expression of several imatinib mesylate-sensitive tyrosine kinases, including c-KIT, platelet-derived growth factor receptor, c-ABL and c-ARG. However, in the MTT proliferation assay, all eight Ewing tumour cell lines were found to be resistant to imatinib mesylate at concentrations ranging from 0.1 to 10 micro M.ConclusionsDespite the expression of imatinib mesylate-sensitive tyrosine kinases, Ewing tumour cells proved resistant to imatinib mesylate in vitro. This observation has implications for the selection of patients for experimental therapy with imatinib mesylate.

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