Abstract 3423: The genomic evolution of prostate cancer under the selective pressure of anti-androgen therapy

Background The implementation of novel technologies such as array comparative genomic hybridization (aCGH) and next-generation sequencing has led to a deeper understanding of the genomic nature of cancer. However, these analyses have classically been done without respecting intra-tumor heterogeneity. Here, we applied a methodology that allows us analyzing the genomic profile of distinct tumor populations from individual tumors and their clonal evolution during the progression to castration-resistant disease, thus enabling the discovery of novel genetic alterations in the course of the development of therapy resistance. Methods Matched pre- and post- hormone treated fresh frozen and/or formalin fixed prostate cancer samples were selected from our biobank. Clonal tumor populations were flow-sorted according to their nuclear DNA content. Sorted tumor populations were subjected to whole genome CGH and to full exome sequencing analyses by the use of Agilent SurePrint 2x400k microarrays and the SureSelect All Exon Kit, respectively. Target aberrations were evaluated using a prostate cancer tissue micro array (TMA) and fluorescence in situ hybridization as well as immunohistochemistry. Results The de-convolution of the genomic evolution in the investigated tumors shows that genetic aberrations and mutations are newly occurring under the selective pressure of anti-androgen therapy. More importantly, judging on the temporal dynamics of changes in allelic frequencies, we cannot only observe events that become more abundant, but also cancer associated mutations that are negatively selected for. We are currently following up several of these targets, of which at least one shows significant association with overall survival and differences in its expression pattern between hormone naive and castration resistant cancer. Conclusions Genomic profiling of distinct clonal tumor populations during prostate cancer progression allows for analysis of intra-tumoral heterogeneity and the underlying clonal evolution. Importantly, this approach identifies genomic aberrations that were selected for under the pressure of hormone ablation therapy. Citation Format: Joel Roman Gsponer, Tanja Dietsche, Alexander Rufle, Thomas Lorber, Darius Juskevicius, Valeria Perrina, Elisabeth Lenkiewicz, Tobias Zellweger, Alexander Bachmann, Michael T. Barrett, Cyrill A. Rentsch, Christian Ruiz, Lukas Bubendorf. The genomic evolution of prostate cancer under the selective pressure of anti-androgen therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3423. doi:10.1158/1538-7445.AM2014-3423