Epithelial ovarian carcinoma is an highly malignant disease, primarily because the majority of patients presents with advanced intraperitoneal metastasis. Exfoliated tumor cells induce disruption of the peritoneal mesothelium and exposure of the collagen-rich submesothelial extracellular matrix (ECM), to which tumor cells subsequently adhere and invade. Ovarian cancer cells adhere avidly to this matrix, facilitated by an interaction between matrix-associated collagen and the cell surface alpha2beta1 integrin. Following adhesion, invading cells secrete proteolytic enzymes including matrix metalloproteinases (MMPs) which initiate degradation of extracellular matrix molecules that act as a barrier to invasion. MMPs are synthesized as latent (pro-) enzymes which, upon activation, catalyze cleavage of a variety of ECM proteins, thus promoting tumor cell migration and invasion. Relative to the normal ovary, ovarian cancer cells and tissues overexpress proMMP-2 (gelatinase A) and pro-membrane type-1 MMP (proMT1-MMP). ProMT1-MMP is processed intracellularly and the mature enzyme plays a dual role as an interstitial collagenase and by activating latent MMP-2. Culturing ovarian cancer cells in 3-dimensional collagen gels induces activation of latent MMP-2 via an MT1-MMP-dependent mechanism, suggesting that multivalent alpha2beta1 ligation regulates subsequent matrix proteolysis. Furthermore, active MMP-2 binds to the ovarian cancer cells surface and leads to enhanced cellular invasion. Based on these observations, it is our working hypothesis that a functional link between adhesion and proteolysis regulates ovarian cancer cell invasive and metastatic behavior. Specifically, we hypothesize that a multivalent ligation of the alpha2beta1 integrin transduces signals leading to increased activation of both proMT1-MMP and proMMP-2, resulting in enhanced ECM degradation and increased invasive activity. The proposed experiments are designed to test the functional link between cell-matrix adhesion, enhanced proteolytic capacity, and increased tumor cell invasion. Initial experiments will address the physical parameters of integrin engagement required for MMP processing. Additional studies will mechanistically evaluate MT1-MMP biochemistry and enzymology, as well as regulation of MT1-MMP expression by lysophosphatidic acid. The functional contribution of increased pericellular MMP activity to invasion/metastasis will also be evaluated. The long-term goal of the proposed research is to identify a strategy by which to block alpha2beta1-mediated intraperitoneal adhesion without induction of matrix degrading proteinases. This approach may uncouple adhesion and proteolysis and thereby terminate progression of the metastatic cascad.
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