[1027] ERG Protein Expression in Localized, Metastatic and Castration Resistant Prostate Cancer: A Comparative Immunhistochemistry and Fluorescent In-Situ Hybridization Study

Liang Hong Teng, Cheng Wang, Kiril Trpkov, Asli Yilmaz, Louis R Begin, Shuhong Liu, Michael Dolph, Tarek A Bismar. Calgary Laboratory Services and University of Calgary, Calgary, AB, Canada; McGill University and Hôpital du Sacré-Coeur de Montréal, Montreal, QC, Canada

Background: ERG gene rearrangements have been reported as the most common gene rearrangement in prostate cancer (PCA). Recently, some reports suggested that ERG protein expression is reflective of genomic ERG rearrangements but that ERG protein expression could also be detected in benign prostate tissue, albeit at a weak level.
Design: We characterize ERG protein expression in comparison to genomic ERG gene rearrangement in PCA using immunohistochemistry (IHC)and fluorescence in situ hybridization (FISH) to assess the potential diagnostic and prognostic value of anti-ERG antibody in the clinical setting. Two hospital-based cohorts including 344 patients, representing benign, high-grade prostatic intraepithelial neoplasia (HGPIN), localized, metastatic and castration resistant PCA were evaluated.
Results: ERG protein expression was detected in 6.8% (2/29) of HGPIN cases, 46.3% (190/410) in localized PCA, 36.1% (13/36) in lymph node metastatic PCA and 37.2% (181/486) in castration resistant PCA cases. In a subgroup of PCA demonstrating foamy-gland morphology, ERG protein expression was detected in only 18.6% (16/86). ERG protein expression and ERG gene rearrangements showed an overall consistency rate of 90.6% (714/788) in the evaluable cores (p<0.0001). The rates of ERG consistency were 100% in the benign glands and HGPIN and 96.1% (270/281) in localized PCA. The consistency rates were lower in the node metastatic and castration resistant PCA groups 76.9% (20/26) and 85% (323/380), respectively (p<0.001).
Conclusions: ERG protein expression appears to be exclusive for the neoplastic prostatic epithelium and showed high concordance between IHC and FISH in localized prostate cancer, suggesting a potential role as a biomarker for prostate cancer diagnosis. We found significantly lower consistency rates of ERG expression between IHC and FISH in lymph node metastatic and castration resistant PCA which limits its value in these setting. The novel observation of lower rates of ERG protein expression in foamy gland PCA may suggest potential differences for this pattern of PCA at the molecular level.
Category: Genitourinary (including renal tumors)

Monday, March 19, 2012 1:00 PM

Poster Session II # 166, Monday Afternoon

 

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