Prognostic Role of Serum Sialyl Lewisx (CD15s) in Colorectal Cancer

Abstract

Objective: Sialyl Lewis^x (sLe^x) is one ligand for E selectin (CD62E), a glycoprotein that is expressed on activated endothelial cells. Adhesion mediated by endothelial E selectin and sLe^x expressed on human tumor cells could be relevant for the development of metastases. The aim of this study was to investigate whether or not a correlation exists between pre-operative levels of ganglioside serum sLe^x and disease-free interval and survival in colorectal cancer patients. Patients and Methods: Thirty Duke’s B and 52 Duke’s C patients undergoing resection for colorectal cancer were studied. The median follow-up time was 34.8 months. A pool of 57 sera from normal subjects was used as an Internal Normal Standard (INS). sLe^x analyses were performed by a thin layer chromatography (TLC) immunostaining technique. Results were expressed as the ratio (R) between bands of INS and bands from each neoplastic serum. Results: The median R value was 0.80 in normal subjects, 0.70 in Duke’s B patients and 1.0 in Duke’s C patients. No significant differences were detected between sLe^x concentrations in sera from normal and neoplastic subjects (p = 0.1). Using an arbitrary cutoff of R = 0.9, the mean disease-free interval in the whole series was 47.4 months for R <0.9 and 126.0 months for R ≧ 0.9 (p = 0.04). The survival time was 76.8 months for patients with R values <0.9 and 156.3 months for patients with R values ≧0.9 (p = 0.1). Conclusions: High serum levels of ganglioside sLe^x significantly correlate with a favorable prognosis and with a lower occurrence of metastases. It is conceivable that soluble sLe^x may compete with membrane-bound sLe^x in the course of interactions between activated endothelium and tumor cells that have reached the circulation.