Suppression of tumor growth and downregulation of platelet-derived endothelial cell growth factor/thymidine phosphorylase in tumor cells by angiogenesis inhibitor TNP-470

We in investigated the effects of the angiogenesis inhibitor TNP-470 on hum an lung squamous cell carcinoma cell lines H226B and H226Br both in vivo an d in vitro, H226B was established from human lung squamous cell carcinoma a nd H226Br was established from a brain metastatic lesion of H226B in nude m ice. Nude mice inoculated with these cells mere treated with 30 mg/kg of TN P-470 subcutaneously every other day. At this dose, TNP-470 only significan tly suppressed the growth of H226Br tumor, but not H226B tumor. Attempts to use a high dose of TNP-470 (100 mg/kg) resulted in a severe loss of body w eight. Immunohistochemical studies showed marked tumor vascularization in H 226Br tumor, but the formation of new blood vessels was suppressed by 30 mg /kg of TNP-470. Investigation of the mechanism of anti-angiogenic effects o f TNP-470 in vivo showed that the expression and the activity of platelet-d erived endothelial cell growth factor/thymidine phosphorylase (PD-ECGF/dThd Pase) in H226Br tumor was significantly suppressed by 30 mg/kg of TNP-470. Furthermore, TNP-470 inhibited cell growth of cultured H226Br dose-dependen tly at concentrations of greater than or equal to 1 mu g/ml. Immunoblot ana lysis revealed H226Br cells gave a stronger PD-ECGF signal than H226B cells , and the expression of PD-ECGF/dThdPase in H226Br mas also suppressed by t reatment with TNP-470 at greater than or equal to 0.1 mu g/ml. No change in basic fibroblast growth factor (bFGF) or vascular endothelial growth facto r (VEGF) was noted in these cell lines, Our results suggested that TNP-470 acts, at least in part, by downregulation of PD-ECGF/dThdPase in this cell line.