Antimetastatic activity of lipopolysaccharide against a NK-resistant murine fibrosarcoma

An intravenous injection of bacterial lipopolysaccharide (LPS) into mice exerted prominent antimetastatic activities against a NK-resistant weakly immunogenic NFSa fibrosarcoma. The number of visible metastases in the lung was increased by a pretreatment of anti-asialoGM1 (asGM1) antibody or silica, but pretreatment of asGM1 antibody or silica scarcely affected the antimetastatic activities of LPS. The pulmonary retention of radiolabeled tumor cells showed that LPS accelerated the detachment of the tumor cells from the lung, and that this acceleration was not suppressed by anti-asGM1 antibody. Sialic acids of lung endothelial cell surface, essential components of various receptors, was diminished by the i.v. injection of LPS. These results suggested that the antimetastatic effect of LPS against NK-resistant NFSa cells was partly the result of modulations of lung endothelial cell surface.