Abstract 6: Expression profiling of laser micro dissected prostate cancer cells delineates genes associated with biochemical recurrence after radical prostatectomy.
Authors: Mortensen Martin M. , Høyer Søren , Sørensen Karina D. , Borre Michael , Ørntoft Torben , Dyrskjøt Lars 
Published: August 2014

Abstract
A distinct feature of localized prostate cancer (PC) is the high prevalence of indolent cancer. This feature raises the dilemma of treatment in this group of patients since a large part of this group will not benefit from surgery. Finding markers of progression to help guide treatment decision will have a great impact on the management of localized prostate cancer. In this study we performed genome-wide expression profiling of 40 cancer samples and 10 samples of normal prostate tissue with the intent to find transcripts that delineate aggressive and indolent cancer. Twenty-four patients with biochemical recurrence (BR) after radical prostatectomy and 16 patients with at least 5-year recurrence free survival were included. Tissue and clinical data have been collected prospectively in the Aarhus PC-project. All prostate samples were fresh frozen and cancer lesions were laser micro dissected. Nugen pico RNA amplification system was used for amplification and Affymetrix U133 plus 2.0 whole genome expression arrays were used. A publicly available PC gene expression dataset was used for validation (GEO accession number GSE10645). Supervised analysis comparing recurrent and non-recurrent disease resulted in only 4 transcripts that reached significance following correction for multiple testing. Next, we therefore performed unsupervised hierarchical cluster analysis in order to discover molecular subgroups associated with aggressiveness of the disease. One sample cluster showed an overrepresentation of recurrent cases (p=0.022, chi2 test) and a cluster of 64 genes showed high expression levels in the group of patient with aggressive disease and low expression in the group of patient with non-aggressive disease. Eighteen of these genes were included in the gene panel tested in the validation set, in which 13 also showed significant association with BR after prostatectomy. Multivariate analysis of IGFBP3 in the validation samples showed an OR of 1.9 (p=0.002), SFRP4 OR=2.1 (p=0.009) and MSR1 OR=2.4 (p=0.014). Using Gene Set Enrichment Analysis we demonstrated that several previously identified molecular signatures associated with aggressiveness were significantly enriched in the molecular subgroup containing tumors from patients with aggressive disease. We have identified novel candidate markers associated with BR after radical prostatectomy and the findings have been successfully validated in an independent patient cohort. Currently, we are using TMAs for additional validation of our markers, and these results will be presented at the meeting. Following further independent validation, these candidate markers may guide treatment decisions for patients with localized prostate cancer in the future.
Citation Format: Martin M. Mortensen, Søren Høyer, Karina D. Sørensen, Michael Borre, Torben Ørntoft, Lars Dyrskjøt. Expression profiling of laser micro dissected prostate cancer cells delineates genes associated with biochemical recurrence after radical prostatectomy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 6. doi:10.1158/1538-7445.AM2013-6