[1065] Expression of ERG Protein in Human Tumors Using a Highly Specific Anti-ERG Monoclonal Antibody

Oksana Yaskiv, Brian Rubin, Huiying He, Paula Carver, Cristina Magi-Galluzzi, Ming Zhou. North Shore LIJ Laboratories, Lake Success, NY; Cleveland Clinic, Cleveland, OH; Cancer Biology and Glickman Urological Institute, Cleveland, OH

Background: ERG protein expression, as the result of TMPRSS:ERG gene rearrangement in prostate cancer (PCa) and endogenous expression in vascular endothelial cells, is considered highly specific for both PCa and vascular lesions. However, only one study using a mouse anti-ERG antibody investigated the ERG protein expression in other human tissue and tumors. In this study, we studied the ERG expression using a different rabbit anti-ERG monoclonal antibody that is widely used for diagnosis and research of prostate carcinoma.
Design: ERG (Rabbit anti-ERG monoclonal antibody; clone EPR 3864, Epitomics) immunoreactivity was assessed on a tissue microarray comprising epithelial tumors (335 cases), vascular lesions (125 cases) and other non-vascular mesenchymal tumors (82 cases). Vascular endothelial cells were used as an internal positive control with assigned staining score of “strong positive”. The expression of ERG protein in tumor cells was scored as negative, weak, moderate and strong.
Results: ERG protein expression was detected in 37% of prostatic adenocarcinoma, 100% of benign vascular tumors (84% strong and 16% moderate staining) and 100% of malignant vascular tumors (85% strong and 15% moderate staining). Additionally, we found moderate positivity in 40% (6/15) of grade I meningiomas, predominantly in fibrous type (5/6, 83%) and transitional type (1/2, 50%). These ERG-positive meningiomas were also positive for Fli-1. Other epithelial and non-epithelial tumors showed absence of ERG expression.
Conclusions: We characterized the ERG protein expression in a wide range of human tumors using a rabbit anti-ERG monoclonal antibody. Such knowledge is important for its clinical use as a prostate carcinoma and vascular specific immunohistochemical maker. ERG protein is detected in approximately 40% of prostate carcinomas and not in any other epithelial tumors. Therefore, a positive ERG immunostain supports the prostatic origin of the epithelial tumors. In addition, positive ERG immunostains are highly sensitive and specific for vascular and lymphatic endothelial cells and therefore can be used in the work-up of benign and malignant vascular lesions. Furthermore, about 40% of meningiomas are also positive for ERG immunohistochemically, probably due to cross-reactivity with Fli-1.
Category: Genitourinary (including renal tumors)

Monday, March 19, 2012 1:00 PM

Poster Session II # 156, Monday Afternoon


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