Suppression of ganglioside GD3 expression in a rat F-11 tumor cell line reduces tumor growth, angiogenesis, and vascular endothelial growth factor production

Ganglioside GD3 is overexpressed in many types of tumors and may be associated with tumor progression and the development of metastatic potential. In our previous study (G. Zeng et al., Biochemistry, 38: 8762-8769, 1999), we established a subclone of the rat dorsal root ganglion-derived F-11 cells in which the expression of ganglioside GD3 was inhibited by stable transfection of the antisense vector against CMP-NeuAc: GM3 α2-8 sialyltransferase (GD3-synthase) gene. This cell line exhibits markedly reduced rate of tumor growth in vivo. Here, we further characterized the antisense-transfected cell line, and the results showed that these cells formed small, minimally vascularized tumors exhibiting extensive necrosis. In vivo Matrigel assay revealed reduced vascularization and low hemoglobin content in the antisense xenografts. Significantly fewer new vessels were found on the antisense xenografts and the skin around them than those on/around the xenografts formed by the sense-transfected and untransfected F-11 cells. The hemoglobin content of the antisense xenografts was much lower than that of the xenografts formed by the control cells. The reduced angiogenesis in the antisense xenografts was correlated with a decrease in vascular endothelial growth factor (VEGF) production. The expression of VEGF was suppressed in the antisense xenografts and the conditioned culture media of the antisense-transfected F-11 cells as determined by Western blotting analysis. This was further confirmed by immunohistochemistry of the tumors using antibodies against VEGF and platelet/endothelial cell adhesion molecule (PECAM-1). Therefore, our results demonstrate that reduced tumor growth in nude mice by suppression of GD3-synthase expression in F-11 cells results from minimal angiogenesis of the tumors through down-regulation of the VEGF expression, which indicates an important role for GD3 in tumor angiogenesis.