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 Pselectin, 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 α 5 β 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 α 5 β 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.

Cell-surface nucleolin is a signal transducing P-selectin binding protein for human colon carcinoma cells

“…This selectin-mediated integrin activation results from at least two distinct intracellular signaling pathways-the p38 MAPK and the PI 3-K pathways -that are linked by a p38 MAPK-PI 3-K signaling complex [27]. These results suggest that P-selectin binding to specific receptors on cancer cells can activate signals that regulate tumor cell adhesion and possibly proliferation.…”

“…Colo-320 HSR human colon adenocarcinoma cells were obtained from the American Type Culture Collection (Rockville, MD) and were cultured as described [27]. Cell lysates for biochemical analyses and flow cytometric analyses were described previously [27].…”

“…Cell lysates for biochemical analyses and flow cytometric analyses were described previously [27]. All protein concentrations were determined using the BCA assay (Pierce, Rockford, IL).…”

“…Adhesion assays were carried out essentially as described [27]. Briefly, 96-well tissue culture clusters (Costar, Corning, NY) were coated by overnight incubation at 4°C with 20 μg/ml Pselectin-IgG-Fc in PBS or 10 μg/ml protein G (Pierce) in 50 mM Na 2 CO 3 /NaHCO 3 , pH 9.5.…”

Liver Membrane Proteome Glycosylation Changes in Mice Bearing an Extra-hepatic Tumor

“…Glycosylation is known to play a role in cancer carcinogenesis and metastasis in many common cancers, and it has been shown to affect the function of many membrane proteins such as CD44 (19), matrix metalloproteinases (MMPs) (20 -22), selectins (23) and cadherins (24) on cancer cells. Glycosyltransferases are a group of enzymes that catalyze the addition of monosaccharides to core proteins.…”