Cadherin switching in ovarian cancer progression

The roles of the cadherins in the progression of ovarian cancer to the late stages of the disease state when malignant cells have disseminated within the peritoneal cavity remain poorly understood. In view of these observations, we have undertaken a comprehensive survey of the cadherin subtypes present in normal ovarian surface epithelium and peritoneum and in the tumors and peritoneal effusions of women diagnosed with Stage I or Stage II primary ovarian cancer using a degenerate cloning strategy for sequences highly conserved among this family of cell adhesion molecules. On the basis of the nucleotide sequences of the resultant PCR products, multiple cadherin subtypes (E-, N-, P-cadherin, and cadherin-4, -6, and -11) were found to be present in these normal and malignant tissues and cells. P-cadherin was determined to be the predominant cadherin subtype in normal peritoneum, peritoneal effusions and Stage II tumor masses. An increase in P-cadherin mRNA and protein expression levels in ovarian tumor masses with progression to later stages of the disease state was confirmed by Northern and Western blot analysis, respectively. In addition, we have determined that the cadherin-associated protein, known as beta-catenin, is expressed in normal peritoneum, ovarian tumors and malignant cell effusions obtained from women with Stage I or Stage II cancer. Immunoprecipitation studies demonstrated that P-cadherin was capable of interacting with beta-catenin in these normal and malignant tissues and cells. Collectively, these findings suggest that the regulated expression of P-cadherin/beta-catenin complexes in ovarian tumor cells may represent a key step in disease progression.