Suppression of pulmonary metastasis in murine B16 melanoma cells by transfection of a sialidase cDNA.

A cytosolic sialidase cDNA was transfected into a highly metastatic and invasive cell line, B16-BL6, derived from the murine B16 melanoma. Stable transfection of a cytosolic sialidase expression vector yielded 4 transfectants with high content of the exogenous sialidase protein as well as enzyme activity. These transfectants exhibited markedly decreased experimental pulmonary metastasis, invasiveness in collagen gels and cell motility on colloidal gold-coated glass plates but no change in cell attachment to fibronectin, collagen type VI or laminin. To cast light on the underlying mechanisms, cellular constituents of the transfectants were analyzed. Sialidase over-expression did not lead to any significant changes in cell surface carbohydrates or intracellular glycoproteins, as revealed by lectin flow cytometry and lectin blotting, respectively. Thin layer chromatography of intracellular glycolipids, however, revealed decreased ganglioside GM3 and increased lactosylceramide as major changes.