Role of the cytoskeleton in adhesion stabilization of human colorectal carcinoma cells to extracellular matrix components under dynamic conditions of laminar flow.

Adhesion stabilization of malignant cells in the microcirculation is necessary for successful metastasis formation. The adhesion of colon carcinoma cells to microcirculation extracellular matrix (ECM) components is mediated, in part, by integrins that can be intracellularly linked to cytoskeletal proteins. Thus the functional status of at least certain integrins can be regulated by complex interactions with cytosolic, cytoskeletal and membrane-bound proteins. Wall shear stress caused by fluid flow also influences cellular functions, such as cell morphology, cytoskeletal arrangements and cell signaling. Using a parallel plate laminar flow chamber dynamic adhesion of human HT-29 colon carcinoma cells to collagen was investigated and compared with cell adhesion under static conditions. Cells were pretreated with cytochalasin D, nocodazole, colchicine or acrylamide to disrupt actin filaments, microtubules or intermediate filaments. Disruption of actin filaments completely inhibited all types of adhesive interactions. In contrast, impairment of tubulin polymerization or disruption of intermediate filaments resulted in different effects on static and dynamic adhesion. Treatment with acrylamide did not interfere with dynamic cell adhesion, whereas under static conditions it partially reduced adhesion rates. Under dynamic conditions increased initial adhesive interactions between HT-29 cells and collagen were found after disruption of microtubules, and the adherent cells demonstrated extensive crawling on collagen surfaces. In contrast, under static adhesion disrupting microtubules did not affect cell adhesion rates. Cytochalasin D and acrylamide were found to inhibit Tyr-phosphorylation of FAK and paxillin, whereas microtubule disrupting agents at low but not high concentrations increased phosphorylation of these focal adhesion proteins. Our results revealed that cytoskeletal components appear to be involved in adhesion stabilization of HT-29 cells to ECM components, and hydrodynamic shear forces modulate this involvement. Tyr-phosphorylation of focal adhesion proteins, such as paxillin and FAK, appears to be a part of this cytoskeleton-mediated process.