[995] Prevalence and Patterns of ERG Expression in Matched Cohorts of African-Americans and Caucasian-Americans with Prostate Cancer

Philip A Rosen, David Pfister, Denise Young, Gyorgy Petrovics, Albert Dobi, Yongmei Chen, David G McLeod, Shiv Srivastava, Isabell A Sesterhenn. Walter Reed National Military Medical Center, Bethesda, MD; Center for Prostate Disease Research, Bethesda, MD; University Hospital, Rheinisch-Westfälische Technische University, Aachen, Germany; Joint Pathology Center, Silver Spring, MD

Background: The 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 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.
Design: Matched for age, Gleason and pathologic stage were 91 AA and 91 CA CaP patients. All underwent radical prostatectomy between 1993 and 2010. Whole mount prostate specimens were used for the immunohistochemical detection of the ERG oncoprotein by a monoclonal antibody (clone 9FY). Individual foci of tumors were noted as either positive or negative. ERG staining data was linked to clinico-pathologic data. Biochemical recurrence was defined as at least 2 PSA's of 0.2 ng/mL or higher at least 8 weeks from surgery.
Results: Comparing CA to AA CaP patients, more had at least one focus of tumor that was ERG (+) (64.8% vs. 45.0%; p = 0.0073), more had ERG (+) index tumors (61.8% vs. 28.2%; p <0.001) and a higher percentage of individual tumor foci were ERG (+) (42.1% vs. 26.0%; p <0.001). There was a trend towards increased biochemical recurrence in CA CaP patients with ERG (+) index tumors.
Conclusions: Between matched cohorts, ERG expression is more prevalent among CA CaP patients. 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.
Category: Genitourinary (including renal tumors)

Monday, March 19, 2012 1:00 PM

Poster Session II # 175, Monday Afternoon


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