Human colonic cancer cells synthesize and adhere to laminin-5.: Their adhesion to laminin-5 involves multiple receptors among which is integrin α2β1

In the mature gut, laminin-5 is expressed at the basal aspect of the differentiating epithelial cells. In vitro, we show that three more or less differentiated human colonic cancer HT29 cell lines produce and deposit laminin-5; they predominantly synthesize and secrete the 440 kDa form of laminin-5 that comprises the unprocessed 155 kDa gamma 2 chain, as determined by immunoprecipitation analysis. In contrast, the highly differentiated colon carcinoma Caco-2 cells produce almost no laminin-5, Using anti-integrin antibodies, we show that adhesion of the two colonic cancer cell lines to laminin-5 is mediated by multiple integrin receptors including those for alpha 3 beta 1, alpha 6 beta 1 and alpha 6 beta 4 integrins like in other cell types. In addition, the implication of integrin alpha 2 beta 1 in this adhesion process is demonstrated for the first time. This has been shown by cell adhesion inhibition experiments, solid phase assays and confocal analysis. Together with previous in situ observations, these data provide a baseline knowledge for the understanding of the regulation of laminin-5 in normal and pathological intestine.