Journal Article

The role of the cytoskeleton in differentially regulating pressure-mediated effects on malignant colonocyte focal adhesion signaling and cell adhesion

Vijayalakshmi Thamilselvan and Marc D. Basson

in Carcinogenesis

Volume 26, issue 10, pages 1687-1697
Published in print October 2005 | ISSN: 0143-3334
Published online May 2005 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgi135
The role of the cytoskeleton in differentially regulating pressure-mediated effects on malignant colonocyte focal adhesion signaling and cell adhesion

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Increased extracellular pressure stimulates colon cancer cell adhesion by activating focal adhesion kinase (FAK) and Src. We investigated the role of the cytoskeleton in pressure-induced inside-out FAK and Src phosphorylation and pressure-stimulated adhesion. We perturbed actin polymerization with phalloidin, cytochalasin D and latrunculin B, and microtubule organization with colchicine and paclitaxol. We compared the effects of these agents on pressure-induced SW620 and human primary colon cancer cell adhesion and inside-out FAK/Src activation with outside-in adhesion-dependent FAK/Src activation. Cells pretreated with cytoskeletal inhibitors were subjected to 15 mmHg increased pressure and allowed to adhere to collagen I coated plates or prevented from adhesion to pacificated plates for 30 min. Phalloidin, cytochalasin D, latrunculin B and colchicine pretreatment completely prevented pressure-stimulated and significantly inhibited basal SW620 cell adhesion. Taxol did not inhibit pressure-induced colon cancer cell adhesion, but significantly lowered basal adhesion. Cytochalasin D and colchicine had similar effects in pressure-stimulated primary human malignant colonocytes. Phalloidin, cytochalasin D, latrunculin B and colchicine prevented pressure-induced SW620 FAK phosphorylation but not Src phosphorylation. FAK phosphorylation in response to collagen I adhesion was significantly attenuated but not completely prevented by these inhibitors. Although Src phosphorylation was not increased on adhesion, the cytoskeleton disrupting agents significantly lowered basal Src phosphorylation in adherent cells. These results suggest that both cytoskeleton-dependent FAK activation and cytoskeleton-independent Src activation may be required for extracellular pressure to stimulate colon cancer cell adhesion. Furthermore, the cytoskeleton plays a different role in pressure-activated FAK and Src signaling than in FAK and Src activation in adherent cells. We, therefore, hypothesize that cytoskeletal interactions with focal adhesion signals mediate the effects of extracellular pressure on colon cancer cell adhesion.

Keywords: ELISA, enzyme linked immunosorbent assay; ECM, extracellular matrix; F-actin, filamentous actin; FAK, focal adhesion kinase; NF-kappaB, nuclear factor kappaB; PBS, phosphate buffered saline

Journal Article.  8676 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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