The role of sialylated Lewis antigens on hematogenous metastases of human pancreas carcinoma cell lines in vivo.

Previous studies have shown that sialyl Lewis a (SLea) and sialyl Lewis x (SLex) correlated to hematogenous metastasis of human cancers. Although SLea/SLex and E-selectin act as a set of adhesion molecules in vitro, it is not clear whether the in vivo correlation is exclusively mediated by the adhesion function. To address this issue, we investigated whether or not the role of SLea/SLex antigens on hematogenous metastasis to the liver in SCID mice was exclusively mediated by adhesion by using antibodies for these antigens and SLea/SLEx-negative, human pancreas adenocarcinoma cell line PCI-6. The absence of SLea/SLex expression was supported by the absent flow cytometric detection of the antigens as well as by the absent attachment augmentation to activated endothelial cells. PCI-6 cells are xenotransplantable to nude and SCID mice and produce vascular endothelial cell growth factor (VEGF) in a significant amount. PCI-6 cells, 1 x 10(6), were injected into the spleens of SCID mice, and resultant liver metastases were evaluated six weeks later. We observed an inhibitory effect on the establishment and growth of metastatic colonies when anti-SLea or anti-SLex antibody was administered. This indicates that SLea/x antigens have an important in vivo role, even in the metastasis of SLea/SLex-negative tumor cells. This implies that there may be an in vivo function of SLea/x antigens other than that of the attachment between tumor and endothelial cells.