Overexpression of the cell adhesion molecules DDR1, claudin 3, and Ep-CAM in metaplastic ovarian epithelium and ovarian cancer

Purpose: A better understanding of the molecular pathways underlying the development of epithelial ovarian cancer (EOC) is critical to identify ovarian tumor markers for use in diagnostic or therapeutic applications. The aims of this study were to integrate the results from 14 transcript profiling studies of EOC to identify novel biomarkers and to examine their expression in early and late stages of the disease. Experimental Design: A database incorporating genes identified as being highly up-regulated in each study was constructed. Candidate tumor markers were selected from genes that overlapped between studies and by evidence of surface membrane or secreted expression. The expression patterns of three integral membrane proteins, discoidin domain receptor 1 (DDR1), claudin 3 (CLDN3), and epithelial cell adhesion molecule, all of which are involved in cell adhesion, were evaluated in a cohort of 158 primary EOC using immunohistochemistry. Results: We confirmed that these genes are highly over-expressed in all histological subtypes of EOC compared with normal ovarian surface epithelium, identifying DDR1 and CLDN3 as new biomarkers of EOC. Furthermore, we determined that these genes are also expressed in ovarian epithelial inclusion cysts, a site of metaplastic changes within the normal ovary, in borderline tumors and in low-grade and stage cancer. A trend toward an association between low CLDN3 expression and poor patient outcome was also observed. Conclusions: These results suggest that up-regulation of DDR1, CLDN3, and epithelial cell adhesion molecule are early events in the development of EOC and have potential application in the early detection of disease.