Abstract 2614: Distinguished features of ERG oncoprotein expression among matched cohorts of African-American and Caucasian-American prostate cancer patients

Abstract

Abstract Introduction and Objective: The ETS-related gene (ERG) proto-oncogene is frequently overexpressed in prostate cancer (CaP) as a result of a genomic rearrangement that places ERG under the control of the androgen-dependent TMPRSS2 promoter. The initial report of quantitative ERG mRNA expression in micro-dissected prostate tumor cells showed significantly higher ERG expression in CaP of Caucasian-Americans (CA) patients vs. African-American (AA) patients (Petrovics et al, Oncogene, 2005). Recent studies (Magi-Galluzzi et al, Prostate, 2011; Elliott et al, USCAP Mtg., 2011) have also shown higher frequency of ERG rearrangement or ERG oncoprotein expression in CaP of CA patients. We evaluate the frequency and pattern of the ERG oncoprotein expression in prostate tumors of matched CA and AA CaP patients to better understand the biological basis for differences in prostate cancer between the two populations. Methods: Ninety one AA and 91 CA CaP patients were matched for age, Gleason score and pathologic stage. All underwent radical prostatectomy between 1993 and 2010. Whole mount prostate specimens were used for the immunohistochemical detection of the ERG oncoprotein by a highly specific ERG monoclonal antibody (clone 9FY). Individual foci of tumors were reported as either positive or negative. ERG staining data was linked to clinico-pathologic data. Biochemical recurrence was defined as two serum PSA measurements of 0.2 ng/mL or higher at least 8 weeks from surgery. Results: A higher percentage of CA (61.8%) than AA (28.2%) CaP patients had ERG positive index tumors and had at least one focus of tumor positive for ERG. A higher percentage of overall tumor foci were also positive for ERG in CA than AA CaP patients. There was high concordance of ERG positive prostatic intra-epitheilal neoplasia (PIN) and ERG positive CaP in both AA and CA patients. Conclusions: ERG expression is more prevalent among CA than AA CaP patients in matched cohorts. Differences in the pattern of ERG expression in CaP and differing trends in biochemical recurrence between CA and AA patients with ERG (+) index tumors suggest a dominant clonal selection of ERG-positive tumors in CA patients. These differences in ERG expression have the potential to delineate biological distinctions of CaP in the two patient populations. Acknowledgement: This study was supported in part by USU-CPDR and NIH grant CA162383 to SS. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2614. doi:1538-7445.AM2012-2614