A new 5-gene signature predictive of risk of relapse in early breast cancer.

Abstract

546 Background: The aim of this study was look for the "core-genes" of published Signatures in order to find a simpler one Methods: To select candidate genes we used data of NCBI Gene Expression Omnibus (http://www.ncbi.nlm.nih.gov/geo/) including 408 breast cancer cases. Raw intensity data of Affymetrix HU133A and HU133B arrays of the two datasets (GSE1456 and GSE3494) were preprocessed using R/Bioconductor and the supercomputer Michelangelo ( www.litbio.org ). The candidate genes were selected from the “70-gene signature” (van 't Veer, Nature 2002), the “21-gene recurrence score” (Paik, NEJM 2004), the “two-gene–ratio model” (Ma, Cancer Cell 2004) and the “15-gene Insuline Resistence” signature (Gennari , JCO, Vol 25, No 18S, 2007: 10597), for a total of 98 genes.The 20 mRNA more significantly related to DFS were evaluated by quantitative reverse transcriptase PCR on 261 consecutive breast cancer cases, from paraffin embedded sections, split into a training (n 137) and a validation set (n 124). Results: The signature was developed on the training set and a multivariate stepwise Cox analysis selected 5 genes independently associated with DFS: FGF18 (HR=1.13, p=0.05) , BCL2 (HR=0.57, p=0.001), PRC1 (HR=1.51, p=0.001), MMP9 (HR=1.11, p=0.08), SERF1a (HR=0.83, p=0.007). These 5 genes were combined into a linear score weighted according to the coefficients of the Cox model, (0.125 FGF18 - 0.560 BCL2 + 0.409 PRC1 + 0.104 MMP9 - 0.188 SERF1A). The linear score was highly associated with DFS (HR=2.7, 95%CI=1.9-4.0, p<0.001). The signature was then evaluated on the validation set assessing the discrimination ability by a Kaplan Meier analysis, using the same cut offs classifying patients at low, medium or high risk of relapse as defined on the training set. The score resulted highly associated with DFS also in the validation set (p<0.001). Conclusions: Overexpression of BCL2 and SERF1A are related to a higher probability of relapse; overexpression of FGF18, PRC1 and MMP9 to a higher probability of survival without recurrence. The signature has a good discriminating ability and a further clinical validation is planned.