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P6. Comparison of Three Antibodies for Immunohistochemical Detection of Epithelial Cell Adhesion Molecule (EpCAM)

Sofie Louise Hjorth Boye, Anne Kirstine Høyer-Nielsen, Søren Nielsen and Mogens Vyberg
Institute of Pathology, Aalborg University Hospital, Denmark.

Background: Epithelial Cell Adhesion Molecule (EpCAM) is a cell membrane associated protein expressed in simple, pseudostratified, and transitional epithelial cells, and in basal cells of mucosal squamous epithelium. Carcinomas are often associated with EpCAM-overexpression, while non-epithelial neoplasias rarely express EpCAM.  As a divergence EpCAM was recently claimed to occur in 90% of gliomas1. The aim of this study was to detect EpCAM expression in epithelial and non-epithelial neoplasias with three different antibodies in optimal protocol settings.

Materials and methods: Tissue microarrays (TMAs) with 21 normal tissues and 46 neoplasias were used to identify optimal protocols on DAKO Autostainer for anti-EpCAM antibodies SPM491, Ber-Ep4 and Ab71916. These were applied on TMAs with 64 epithelial and 113 non-epithelial neoplasias including 85 gliomas. H-scores for membrane staining reactions were calculated and the neoplasias classified based on the highest score: H-score 0-10, non-expressor; 11-100, low expressor; 101-200, intermediate expressor; 201-300, high expressor. Background staining was registered.

Results: Apart from two seminomas and a B-cell lymphoma, membraneous EpCAM was only detected in epithelial neoplasias. For 50 high expressor neoplasias, mean H-scores with SPM491, Ber-Ep4, and Ab71916 were 289, 274, and 193, respectively. For 11 intermediate expressor neoplasias, mean H-scores were 165, 87, and 25 respectively. For three low expressor neoplasias, mean H-scores were 83, 8, and 2 respectively. All epithelial neoplasias were positive with SPM491, two was false negative with Ber-Ep4 and three with Ab71916. None of the gliomas expressed EpCAM. Faint but widespread background staining was mainly seen with Ab71916.

Conclusion: SPM491 provided 100% sensitivity for detection of EpCAM in epithelial neoplasias followed by Ber-Ep4 (97%) and Ab71916 (95%).The latter provided the lowest H-score and poorest signal-to-nosie ratio. Gliomas do not express EpCAM.

1 Chen X et al. The overexpression of epithelial cell adhesion molecule (EpCAM) in glioma. J Neurooncol. 2014 Aug;119(1):39-47. doi: 10.1007/s11060-014-1459-5. Epub 2014 Jun 7. PubMed PMID: 24906438.
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