Effects of vascular endothelial growth factor and E-selectin on angiogenesis in the murine metastatic RCT sarcoma

The relationship between vascular endothelial growth factor (VEGF) and induction of angiogenesis in high-metastatic RCT(+) or low-metastatic RCT(-) clones of the poorly differentiated murine RCT sarcoma was investigated. The association with E-selectin in VEGF-induced angiogenesis was also evaluated. RCT(+) cells produced significantly larger amounts of VEGF than RCT(-) cells. In a tube formation assay with murine lung microvascular endothelial (MLE) cells, conditioned medium from RCT(+) cells showed a significantly greater effect on tube formation than that from RCT(-) cells. Induction of tube formation was suppressed by anti-mouse VEGF monoclonal antibody. Furthermore, anti-mouse E-selectin monoclonal antibody suppressed the tube formation induced by recombinant mouse VEGF. In a flow-cytometric analysis, the expression of E-selectin on MLE cells was upregulated after pretreatment with conditioned medium from RCT(+) and RCT(-) cells. Conditioned medium from RCT(+) cells induced a higher expression of E-selectin compared to medium from RCT(-) cells. Anti-VEGF monoclonal antibody prevented the upregulation of E-selectin by the RCT cell-conditioned medium. These findings suggest that E-selectin plays an important role in the angiogenesis induced by VEGF. VEGF derived from tumor cells may enhance angiogenesis by upregulating the expression of E-selectin on vascular endothelial cells.