Cell-cell adhesion in the normal ovary and ovarian tumors of epithelial origin; an exception to the rule.

Cells are held together either by direct cell-cell contact or adhesion to extra-cellular matrix. Cell-cell adhesion in epithelial cell sheets consists of junctions, i.e. tight-, adherens- and gap-junctions. The adherens junctions, which are build up by the cadherin/catenin complex, are the main topic of this review, especially the aspect of its role in ovarian tumor biology. The ovarian surface epithelium is the origin for approximately 90% of the malignant ovarian tumors. The tumors arise from the inclusion cysts, localized in the ovarian stroma and grow solid, cystic or in mixed formations. Intra-abdominal spread of the ovarian cancer is common and this is a process that theoretically could be closely connected with impaired cell-cell adhesion. However, as we stand today, descriptive and functional studies on the cadherin-catenin complex and its cell signaling role in ovarian tumorigenesis reveals data that suggests a conversion of the mesothelial-like cells of the ovarian surface to a more epithelial phenotype with normal cell-cell adhesion prior to tumor differentiation. In later stages, invasive ovarian tumors still strongly express several cadherins, which are contrary to many other tumors, i.e. prostate and thyroid adenocarcinomas.