Soluble N‐cadherin in human biological fluids

Classical cadherins such as E‐, P‐ and N‐cadherin are transmembrane proteins that mediate cell–cell adhesion, and are important in embryogenesis, maintenance of tissue integrity and cancer. Proteolytic shedding of the extracellular domain results in the generation of soluble E‐, P‐ or N‐cadherin ectodomains. Circulating soluble E‐ and P‐cadherin have been described in the serum, and elevated levels were detected in cancer patients when compared with healthy persons. Here we report the presence of soluble N‐cadherin, a 90‐kD protein fragment, in the serum of both healthy persons and cancer patients, using a direct ELISA and immunoprecipitation. A correlation was found between prostate specific antigen and soluble N‐cadherin, and significantly elevated levels were detected in prostate cancer follow‐up patients. The N‐cadherin protein is neo‐expressed by carcinomas of the prostate, and is responsible for epithelial to fibroblastic transition. This is reflected by the higher concentrations of soluble N‐cadherin in prostate cancer patients than in healthy persons. © 2006 Wiley‐Liss, Inc.