Integrin receptors and ECM proteins involved in preferential adhesion of colon carcinoma cells to lung cells

To assess the putative role of extracellular matrix (ECM) proteins on lung cells interacting with integrin receptors on colon carcinoma cells, an in vitro adhesion assay was used to investigate these factors. Tumor necrosis factor (TNF)-α treatment of fetal lung cell line MRC 9, upregulated expression of ECM proteins and also supported enhanced adhesion of PTC colon carcinoma cells. Antibodies to ECM proteins significantly blocked this enhanced adhesion of PTC cells. Similarly, antibody blocking of β1 and β2 integrin receptors on PTC cells revealed the integrin receptors involved in this enhanced adhesion. β1 integrin receptors like α2β1, α4β1 and α5β1 on PTC cells were found interacting with their ECM ligands like fibronectin and laminin on TNF-α stimulated MRC 9 cells. Interestingly, PTC cells were found to constitutively express αLβ2, which is normally expressed by leukocytes. The data from the present study indicates that expression of multiple β1 and β2 integrins by colon carcinoma cells putatively allows these cells to successfully adhere to secondary sites like lungs.