title: Pressure activates colon cancer cell adhesion by inside-out focal adhesion complex and actin cytoskeletal signaling.
abstract: OBJECTIVE
  Few circulating tumor cells implant or cause metastasis. We hypothesized that venous or lymphatic pressure or iatrogenic pressure during resection activates signals governing malignant colonocyte adhesion.
  
  
  METHODS
  We studied the effect of 15 mm Hg increased pressure for 30 minutes on adhesion of primary human colon cancer cells and SW620 colonocytes to collagen and endothelial cells. We modulated integrin affinity with extracellular cations. We assessed binding affinity by detachment assay; integrin surface expression by flow cytometry; and focal adhesion kinase (FAK), Src, and extracellular signal-regulated kinase (ERK) activation by Western analysis and Src in vitro kinase assay. We inhibited Src (PP2), FAK (small RNA interference, SiRNA, or FRNK transfection), MEK (PD98059), PKC (calphostin C), and actin destabilization (phalloidin).
  
  
  RESULTS
  Pressure and manganese stimulated primary and SW620 colonocyte adhesion to collagen. Pressure also stimulated SW620 adhesion to endothelial monolayers. Pressure strengthened SW620 binding force to matrix without changing integrin surface expression. Pressure activated SW620 FAK and Src, but not ERK. Manganese did not. Calcium-inhibited adhesion but stimulated FAK (but not Src). PP2 prevented pressure activation of Src, Src phosphorylation of FAK576, and pressure-stimulated adhesion but not FAK397 autophosphorylation. FRNK transfection or FAK SiRNA also prevented pressure-stimulated adhesion. FAK SiRNA ablated pressure-activated FAK397, Src, and FAK576 phosphorylation. Neither Src nor FAK inhibition blocked cation effects. Phalloidin prevented pressure-stimulated adhesion. PD98059 or calphostin C did not.
  
  
  CONCLUSIONS
  In contrast to divalent cations, extracellular pressure may increase integrin affinity and promote colon cancer adhesion via actin dependent inside-out FAK and Src signals. This mechanotransduced pathway may regulate metastasizing tumor cell adhesion.
authors.affiliation: Department of Surgery, John D. Dingell VA Medical Center, Detroit, MI 48201, USA.
authors.forename: Vijayalakshmi
authors.initials: V
authors.lastname: Thamilselvan
authors.forename: Marc D
authors.initials: MD
authors.lastname: Basson
mesh_terms: D000199:Actins / Q000037:antagonists & inhibitors / Q000502:physiology*; D000818:Animals; D001011:Aorta / Q000166:cytology*; D002448:Cell Adhesion / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D024042:Collagen Type I; D003110:Colonic Neoplasms / Q000473:pathology / Q000503:physiopathology*; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology; D004789:Enzyme Activation / Q000187:drug effects; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D016023:Integrins / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010590:Phalloidine / Q000494:pharmacology; D011312:Pressure; D011505:Protein-Tyrosine Kinases / Q000378:metabolism / Q000502:physiology*; D011743:Pyrimidines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: C412373:AG 1879; D000199:Actins; D024042:Collagen Type I; D016023:Integrins; D011743:Pyrimidines; D034741:RNA, Small Interfering; D010590:Phalloidine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C496052:Ptk2 protein, rat; D019061:src-Family Kinases; D020928:Mitogen-Activated Protein Kinases