Cell Adhesion and Proteolytic Potential in OSCC

Northwestern University, Evanston IL

Investigators

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Abstract

DESCRIPTION: (provided by applicant) The invasive behavior of oral squamous cell carcinoma (OSCC) requires coordinated cellular events including dissociation of cell-cell contacts, integrin-mediated basement membrane attachment and detachment, extracellular matrix (ECM) proteolysis, changes in cytoskeletal dynamics and the acquisition of a migratory phenotype. In the previous funding period, we have focused on the contribution of proteolytic processing of the ECM component laminin-5 (LN5) to regulation of motility. LN5 engages both the alpha 3 beta 1 and alpha 6 beta 4 integrins and, in contrast to the majority of ECM components, staining for LN5 persists in OSCC lesions. Production of ECM-degrading matrix metalloproteinases (MMPs) is an early event in malignant progression. ProMMP-2 is a soluble proteinase that is activated post-translationally at the cell/matrix interface by membrane type 1 MMP (MT1-MMP). Inactive proMT1-MMP is processed intracellularly by furin and the mature enzyme plays a dual role by cleaving both matrix proteins and proMMP-2. Relative to the normal oral mucosa, expression of both MMP-2 and MT1-MMP is enhanced in OSCC lesions. Further, we have previously demonstrated that alpha 3 beta 1 integrin aggregation promotes proMMP-2 processing via an MT1-MMP-dependent mechanism. However, cellular regulation of furin-mediated proMT1-MMP zymogen activation in OSCC and the effect of alpha 6 beta 4 integrin aggregation have not been addressed. Altered expression of E-cadherin, a transmembrane protein that promotes cell-cell contact, is also associated with OSCC progression. Our preliminary data suggest that E-cadherin engagement can differentially regulate both the expression and activation of proMMP-2. Together these preliminary results support the hypothesis that proteinase expression and subsequent tumor cell behavior may be regulated on a cellular level via the engagement of cell-matrix and cell-cell adhesion molecules. Adhesion molecules also regulate changes in cytoskeletal dynamics that accompany motility; however the effect of direct alteration of cytoskeletal structure using mechanical force and the impact on proteinase expression in OSCC is unknown. The overall goal of Project 2 is to assess the mechanistic link between acquisition of proteolytic potential and induction of migratory and invasive behavior. To achieve this goal, we will evaluate the effect of integrin aggregation on membrane proteinase expression and trafficking, examine the mechanism of E-cadherin-mediated regulation of proteolytic potential, assess the potential correlation between proteinase expression and cytoskeletal dynamics, and elucidate the contribution of proteolytic activity to motility and invasion.