1. ¹Laboratory of Cancer Genetics, Institute of Medical Technology, Tampere University Hospital and University of Tampere, University of Tampere, Tampere, FIN-33014, Finland
2. ²Department of Pathology, Tampere University Hospital, Tampere, FIN-33520, Finland

Correspondence: Professor A Kallioniemi, E-mail: anne.kallioniemi@uta.fi

Received 8 November 2006; Revised 24 January 2007; Accepted 20 February 2007; Published online 13 March 2007.

Abstract

Increased copy numbers of 17q23 chromosomal region have been shown to occur in different tumour types and to be associated with tumour progression and with poor prognosis. Several genes have earlier been proposed as potential oncogenes at this region largely on the grounds of cell lines studies. In this study, we performed a systematic gene expression survey on 26 primary breast tumours with known 17q23 amplification status by quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR). The 17q23 amplicon is restricted to an 5 MB region in breast cancer and contains 29 known genes. Our survey revealed a statistically significant (P<0.01) difference between the high level and no amplification groups in a set of eleven genes whereas no difference between the moderate and the non-amplified tumour groups were observed. Interestingly, these 11 genes were located adjacent to one another within a 1.56 Mb core region in which all except one of the genes were overexpressed. These data suggest that only high-level amplification at the 17q23 amplicon core leads to elevated gene expression in breast cancer. Moreover, our results highlight the fact that 17q23 amplicon carries multiple candidate genes and that this may be a more common event in gene amplification than previously thought.