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Gene expression in 16q is associated with survival and differs between Sørlie breast cancer subtypes.

Wennmalm K, Calza S, Ploner A, Hall P, Bjöhle J, Klaar S, Smeds J, Pawitan Y, Bergh J

Department of Oncology and Pathology, Cancer Center Karolinska, Radiumhemmet, Karolinska Institutet and University Hospital, Stockholm, Sweden. Kristian.Wennmalm@cgb.ki.se

We have investigated the relationship between gene expression and chromosomal positions in 402 breast cancer patients. Using an overrepresentation approach based on Fisher's exact test, we identified disproportionate contributions of specific chromosomal positions to genes associated with survival. Our major finding is that the gene expression in the long arm of chromosome 16 stands out in its relationship to survival. This arm contributes 36 (18%) and 55 (11%) genes to lists negatively associated with recurrence-free survival (set to sizes 200 and 500). This is a highly disproportionate contribution from the 313 (2%) genes in this arm represented on the used Affymetrix U133A and B microarray platforms (Bonferroni corrected Fisher test: P < 2.2 x 10(-16)). We also demonstrate differential expression in 16q across tumor subtypes, which suggests that the ERBB2, basal, and luminal B tumors progress along a high grade-poor prognosis path, while luminal A and normal-like tumors progress along a low grade-good prognosis path, in accordance with a previously proposed model of tumor progression. We conclude that important biological information can be extracted from gene expression data in breast cancer by studying non-random connections between chromosomal positions and gene expression. This article contains Supplementary Material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat.

Published 13 November 2006 in Genes Chromosomes Cancer, 46(1): 87-97.
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