Prognostic role of serum sialyl Lewisx (CD15s) in colorectal cancer.

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 > or = 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 > or =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.