Focal Adhesion Kinase (FAK) reguliert Zelladhäsion von HT-29 Kolon-Karzinomzellen an extrazellulärer Matrix unter hydrodynamischen Flowbedingungen

Abstract

Important regulatory signals for tumor cell adhesion to extracellular matrix components often involve integrin-mediated signal transduction. Focal adhesion kinase (FAK) is an important part of integrin-related focal adhesion plaques and adhesion-mediated signal transduction. Under laminar flow conditions shear forces can modify various cellular functions, including phosphorylation events and cytoskeletal alterations involved in signal transduction. Therefore, the involvement of FAK in integrin-mediated cell adhesion to extracellular matrix components was investigated. In addition, the effects of hydrodynamic shear forces on the Tyr-phosphorylation status of FAK were examined. Human HT-29 colon carcinoma cells, where the expression of FAK was reduced using antisense oligonucleotides, were used to study cell adhesion to collagen in a parallel plate laminar flow chamber or under static conditions. Wall shear adhesion threshold, dynamic adhesion rate and adhesion stabilization rate were determined to differentiate initial adhesion events from adhesion stabilization. These dynamic adhesion properties were compared to static adhesion in microtiterplate assays. If HT-29 cells were exposed to different levels of hydrodynamic shear forces, Tyr-phosphorylation of FAK was increased, dependent on the wall shear stress used. Reduced expression of FAK interfered with early adhesion events to collagen and adhesion stabilization under flow conditions, but not with static cell adhesion. FAK appears to be involved in early events of integrin-mediated adhesion stabilization of HT-29 cells under dynamic conditions of fluid flow. This kinase can take part in the establishment and maintainance of definitive adhesive interactions to extracellular matrix components that enable adherent tumor cells to resist fluid shear forces. The tyrphosphorylation status of FAK may facilitate this regulatory function in human colon carcinoma cells.