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Biological activity of a novel
tyrosine kinase inhibitor of the 2-phenylaminopyrimidine class, Imatinib
(STI571, Gleevec), on human glioblastoma cells
Huan Ren, Alf Giese, Tingchang Chou, Steven Pelech, Nikolai
Rainov.
University of Liverpool,Harbin Medical Univ.,
China, Liverpool, UK; University Hospital Eppendorf, Hamburg, Germany; Memorial
Sloan-Kettering Cancer Center, New York, NY; Kinexus Corp., Vancouver, Canada;
Department of Neuroscience, University of Liverpool, and Dept. Immunology,
Harbin Medical Univ., China, Liverpool, UK
Objectives.
Imatinib mesylate
belongs to a novel class of molecularly targeted drugs, tyrosine kinase signal
transduction inhibitors, and is currently in phase II/III clinical trials for
leukemia and other human malignancies.
The aim of this study was to investigate the mechanisms of action of Imatinib on
malignant glioma in cell culture.
Methods.
Human and rodent glioblastoma cell lines were
investigated for expression of PDGF receptors / ligands by RT-PCR.
Tumor cells were incubated with Imatinib, Temozolomide (TMZ), or a combination
of both drugs, and toxicity was measured by microplate MTT assays.
Synergy was evaluated by the Chou-Talalay method.
Colony formation assays were carried out, and flow cytometry was used to analyze
tumor cell cycle progression and cell death induced by Imatinib.
Migration of glioma cells treated with Imatinib was quantified by monolayer
migration assays.
Immunoblot-based differential protein kinase profiling was performed on glioma
cells after long-term treatment with Imatinib, and compared with controls.
Results.
PDGF-AA and PDGF-BB ligands were expressed in
all glioma cell lines, while PDGFR-a and PDGFR-b were not detectable in some
cell lines.
TMZ acted synergistically with Imatinib in T98G cells.
All other cell lines were less sensitive against Imatinib than T98G cells and
displayed no linear dose-toxicity relationship and no synergy of Imatinib and
TMZ.
Imatinib at 10 microM partly inhibited the proliferation and colony formation of
human glioma cells.
Higher doses induced rapid cell death by apoptosis and necrosis.
The migration ability of glioma cells was significantly reduced at Imatinib
concentrations of 5-15 microM.
Multi-immunoblot protein kinase profiling indicated that long-term treatment
with Imatinib resulted in significant down-regulation (69-44% of control) of
casein kinase 2, protein tyrosine kinase 2, Janus kinases 1 and 2, and
extracellular-regulated kinase 3, and in strong up-regulation (113-303% of
control) of cyclin dependent kinases (cdk) 1 and 4, S6 kinase p70, and protein
kinase C.
Conclusions.
The tyrosine kinase inhibitor Imatinib shows
considerable activity against malignant glioma cells in cell culture.
It inhibits tumor cell proliferation and migration, and is apparently able at
higher doses to down-regulate some protein kinases, including PDGFR-a and
PDGF-b.
Imatininb effects are not abolished by the absence of PDGF-a or PDGF-b receptors
in some cell lines, and evidence is presented that Imatinib toxicity is mediated
by inhibition of additional protein kinases.
Copyright © 2003 American Association for Cancer Research. All rights reserved.
Source: http://aacr03.agora.com/planner/displayabstract.asp?presentationid=6791
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