Tumour-expressed CD43 (sialophorin) mediates tumour-mesothelial cell adhesion

Mesothelial cell intercellular adhesion molecule-1 (ICAM 1) has recently been shown to play a role in tumour cell adherence to the peritoneum. However, solid tumours poorly express its most ubiquitous ligand, beta(2) integrin. The aim of this study was to investigate the role of the beta(2) integrin subunit and CD43, a known ligand for ICAM 1, in the development of peritoneal metastases. beta(2) Integrin subunit and CD43 expression was assessed on a number of tumour cell lines. Adhesion of SW1222 and PSN-1 cells to human peritoneal mesothelial cells was investigated using a fluorometric assay incorporating an inhibitory antibody to beta(2) integrin and CD43. beta(2) Integrin expression was not inducible on these tumour cell lines, but Western blotting demonstrated CD43 expression in all the cancer cell lines examined and cell surface expression was confirmed by flow cytometry. The antiCD43 antibody significantly reduced adhesion of PSN-1 and SW1222 cells to HPMC, however beta(2) integrin inhibition did not reduce tumour cell adhesion. CD43 is expressed by a variety of carcinoma cell lines, and plays a role in tumour cellperitoneal adhesion probably via interactions with its putative ligand ICAM-1.