ICAM-1 mediated peritoneal carcinomatosis, a target for therapeutic intervention

Development of peritoneal metastasis is a significant issue in the treatment of abdominal cancers. Primary interaction between tumour cells and the mesothelium is a vital step in initiating this process. Our aim was to determine the role of the intercellular adhesion molecule-1 (ICAM-1) in mesothelial-tumour adhesion and the effectiveness of therapeutic intervention. Mesothelial cells were derived from omental tissue. ICAM-1 expression in resting state, in the presence of TNF-alpha or after the application of heparin or hyaluronan was determined by flow cytometry. Functional effects on tumour adhesion to a mesothelial monolayer were determined via a Calcein-AM in vitro adhesion assay. In vivo studies were performed utilising 30 WAG/rij rats, which underwent mini-laparotomy with the injection of 1x10(5) CC513 tumour cells intraperitoneally. Tumour growth was assessed macroscopically and microscopically by two independent examiners. Mesothelial cells expressed high level of ICAM-1, which was up-regulated by the presence of TNF-alpha. The introduction of heparin caused a decrease in ICAM-1 expression, however hyaluronan did not affect the expression. A significant decrease in tumour-mesothelial cell adhesion in vitro and complete aberration of tumour growth in vivo was observed with heparin application. In vitro studies showed utilisation of high molecular weight hyaluronan, which was more limited in vivo. These data imply that heparin may be used as a potential therapeutic through a defined molecular mechanism both in vitro and in vivo. Hyaluronan appears to function as a barrier and hence may be unreliable in blocking peritoneal recurrence.