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Cancer Genes and Genomics

Amplification of KIT, PDGFRA, VEGFR2, and EGFR in Gliomas

¹ Laboratory of Molecular Oncology, Biomedicum Helsinki; ² Department of Pathology, Helsinki University Central Hospital (HUSLAB) and University of Helsinki; ³ Molecular Cancer Biology Program, University of Helsinki, Biomedicum Helsinki; ⁴ Institute of Medical Technology, University of Tampere, Finland; and ⁵ Department of Oncology, Helsinki University Central Hospital, Helsinki, Finland

Requests for reprints: Marjut Puputti, Laboratory of Molecular Oncology, Biomedicum, Room B426b, Haartmaninkatu 8, P.O. Box 700, FIN-00029 Helsinki, Finland. Phone: 358-9-471-71831; Fax: 358-9-471-71834. E-mail: Marjut.Puputti{at}hus.fi

Receptor tyrosine kinase aberrations are implicated in the genesis of gliomas. We investigated expression and amplification of KIT, PDGFRA, VEGFR2, and EGFR in 87 gliomas consisting of astrocytomas, anaplastic astrocytomas, oligodendrogliomas, or oligoastrocytomas in tumor samples collected at the time of the diagnosis and in samples of the same tumors at tumor recurrence. Gene amplifications were investigated using either chromogenic in situ hybridization or fluorescence in situ hybridization, and protein expression using immunohistochemistry. In samples collected at glioma diagnosis, KIT and PDGFRA amplifications were more frequent in anaplastic astrocytomas than in astrocytomas, oligodendrogliomas, and oligoastrocytomas [28% versus 5% (P = 0.012) and 33% versus 2% (P = 0.0008), respectively]. VEGFR2 amplifications occurred in 6% to 17% of the gliomas at diagnosis, and EGFR amplifications in 0% to 12%. Amplified KIT was more frequently present in recurrent gliomas than in newly diagnosed gliomas (P = 0.0066). KIT amplification was associated with KIT protein expression and with presence of PDGFRA and EGFR amplifications both at the time of the first glioma diagnosis and at tumor recurrence, and with VEGFR2 amplification at tumor recurrence. Three (4%) primary gliomas and 10 (14%) recurrent gliomas that were evaluable for coamplification of KIT, PDGFRA, and VEGFR2 showed amplification of at least two of these genes; the amplicon contained amplified KIT in all 13 cases. In conclusion, besides glioblastoma, amplified KIT, PDGFRA, and VEGFR may also occur in lower-grade gliomas and in their recurrent tumors. It is currently not known whether specific tyrosine kinase inhibitors are effective in the treatment of such gliomas. (Mol Cancer Res 2006;4(12):927–34)