title: P-selectin activates integrin-mediated colon carcinoma cell adhesion to fibronectin.
abstract: During hematogenous cancer metastasis, tumor cells separate from a primary mass, enter the bloodstream, disperse throughout the body, migrate across vessel walls, and generate distant colonies. The later steps of metastasis superficially resemble leukocyte extravasation, a process initiated by selectin-mediated cell tethering to the blood vessel wall followed by integrin-mediated arrest and transendothelial migration. Some cancer cells express P-selectin ligands and attach to immobilized P-selectin, suggesting that these cells can arrest in blood vessels using sequential selectin- and integrin-mediated adhesion, as do leukocytes. We hypothesize that selectin binding may regulate subsequent integrin-mediated steps in metastasis. Using a model system of cultured Colo 320 human colon adenocarcinoma cells incubated with soluble P-selectin-IgG chimeric protein, we have found that P-selectin can stimulate activation of the alpha(5)beta(1) integrin resulting in a specific increase of adhesion and spreading of these cells on fibronectin substrates. P-selectin binding also induced activation of p38 mitogen-activated protein kinase (p38 MAPK) and phosphatidylinositol 3-kinase (PI3-K). PI3-K inhibitors blocked P-selectin-mediated integrin activation, cell attachment, and cell spreading. Inhibition of p38 MAPK activation blocked cell spreading, but not cell attachment. P-selectin binding also resulted in formation of a signaling complex containing PI3-K and p38 MAPK. These results suggest that P-selectin binding to tumor cells can activate alpha(5)beta(1) integrin via PI3-K and p38 MAPK signaling pathways leading to increased cell adhesion. We propose that P-selectin ligands are important tumor cell signaling molecules that modulate integrin-mediated cell adhesion in the metastatic process.
authors.affiliation: Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health Sciences, NIH, DHHS, Research Triangle Park, NC 27709, USA.
authors.forename: Merit E
authors.initials: ME
authors.lastname: Reyes-Reyes
authors.forename: Margaret D
authors.initials: MD
authors.lastname: George
authors.forename: John D
authors.initials: JD
authors.lastname: Roberts
authors.forename: Steven K
authors.initials: SK
authors.lastname: Akiyama
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism*; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000378:metabolism*; D004789:Enzyme Activation; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D039081:Integrin alpha5beta1 / Q000378:metabolism* / Q000502:physiology; D020935:MAP Kinase Signaling System; D019007:P-Selectin / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011485:Protein Binding; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D005353:Fibronectins; D039081:Integrin alpha5beta1; D019007:P-Selectin; D019869:Phosphatidylinositol 3-Kinases; D048051:p38 Mitogen-Activated Protein Kinases