Reversible modulation of cell-cell adhesion, cell-matrix adhesion, and proteolytic activity plays a critical role in remodeling of the neoplastic ovarian epithelium during metastasis, implicating cadherins, integrins, and proteinases in i.p. metastatic dissemination of epithelial ovarian carcinoma (EOC). Aberrant epithelial differentiation is an early event in ovarian carcinogenesis; thus, in contrast to most carcinomas that lose E-cadherin expression with progression, E-cadherin is abundant in primary EOC. Metastasizing EOCs engage in integrin-mediated adhesion to submesothelial interstitial collagens and express matrix metalloproteinases (MMP) that facilitate collagen invasion, thereby anchoring secondary lesions in the submesothelial matrix. As metalloproteinases have also been implicated in E-cadherin ectodomain shedding, the current study was undertaken to model the effects of matrix-induced integrin clustering on proteinase-catalyzed E-cadherin ectodomain shedding. Aggregation of collagen-binding integrins induced shedding of an 80-kDa E-cadherin ectodomain [soluble E-cadherin (sE-cad)] in a MMP- and Src kinase-dependent manner, and sE-cad was prevalent in ascites from ovarian cancer patients. Expression of MMP-9 was elevated by integrin aggregation, integrin-mediated ectodomain shedding was inhibited by a MMP-9 function blocking antibody, and incubation of cells with exogenous MMP-9 catalyzed E-cadherin ectodomain shedding. In contrast to other tumors wherein sE-cad is released into the circulation, EOC tumors maintain direct contact with sE-cad–rich ascites at high concentration, and incubation of EOC cells with physiologically relevant concentrations of recombinant sE-cad disrupted adherens junctions. These data support a novel mechanism for posttranslational modification of E-cadherin function via MMP-9 induction initiated by cell-matrix contact and suggest a mechanism for promotion of EOC metastatic dissemination. [Cancer Res 2007;67(5):2030–9]