Abstract 2768: Single molecule approach detects significant mutation heterogeneity at the androgen receptor locus in prostate tumors

Abstract

Abstract Studying the impact of genomic instability in cancer has been traditionally performed with PCR-based techniques. PCR-based methods may underestimate the total number of somatic mutations present in heterogeneous tumor genomes. Using standard PCR based methods we identified many missense somatic mutations of the DNA repair polymerase genes pol beta, pol eta and pol kappa in 30 prostate tumors. However, using a single molecule random cloning/sequencing method we uncovered a very high frequency of somatic alterations in prostate tumors: 0.52 somatic alterations per Kb of genomic DNA sequence (which corresponds to 1.8 million alterations per tumor cell genome). We then examined the somatic alteration frequency present in exon 2 of the androgen receptor (AR) gene, an established “driver” gene in prostate tumor progression. Exon 2 of the AR gene includes part of the DNA binding domain of this trancription factor. We report a similarly high somatic alteration frequency (including 50 missense AR mutations) and extreme AR mutation heterogeneity in prostate cancer patients with Gleason scores 5-9. Each somatic mutation was present in 1-5% of the tumor clones. Thus most of these “driver” mutations are not detectable by direct sequencing of a PCR product. All four cysteine residues that comprise the first Zinc-finger (Zf1) of the AR DNA-binding domain (the only zinc finger present in exon 2) had missense mutations in these patients (including recurrent mutations). In fact, we found missense or stop codon mutations of almost all Zf1 residues in these tumors. Some of these mutations have been shown to confer higher oncogenic transformation potential and hormone promiscuity to the androgen receptor. These data provide a molecular basis for the understanding of both a) the impact of genomic instability and b) anti-androgen drug resistance during prostate cancer progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2768. doi:10.1158/1538-7445.AM2011-2768