Differential behavior of VEGF receptor expression and response to TNP-470 in two immortalized human endothelial cell lines

Angiogenesis consists of endothelial cell proliferation, migration and tube formation. It is useful to investigate endothelial cell behavior using imm ortalized endothelial cell lines. We characterized cell growth property, gr owth factor dependency and response to angioinhibitory drugs; TNP-470, stau rosporine, radicicol and genistein, using human umbilical vein endothelial cells (HUVECs) immortalized by human papilloma virus (HPV)-16 E6-E7, named HUVECs/E6-E7, and HUVECs/E6-E7 transformed by v-Ki-ras gene, named HUVECs/E 6-E7/ras. The dependency to vascular endothelial cell growth factor (VEGF) and basic fibroblast growth factor (bFGF) for cell proliferation decreased in HUVECs/E6-E7, but were restored in HUVECs/E6-E7/ras. Flow cytometric ana lysis demonstrated that a VEGF receptor KDR/flk-1 was down-regulated in HUV ECs/E6-E7 but not in HUVECs/E6-E7/ras. Expression of another VEGF receptor flt-1 was consistent in all cells including HUVECs, HUVECs/E6-E7 and HUVECs / E6-E7/ras. According to the analysis of the angioinhibitory drugs, HUVECs /E6-E7 was obviously resistant to TNP-470, but HUVECs/E6-E7/ras showed simi lar response compared to HUVECs which suggests that v-Ki-ras signaling path way is associated with VEGF receptor expression and make HUVECs/ E6-E7 sens itive to TNP-470 by modulating the signal transduction cascade. In conclusi on, HPV-16 E6-E7 and v-Ki-ras genes have unique growth properties and these immortalized cells are useful for investigating signal transduction pathwa ys of endothelial cells, and for screening of angioinhibitory drugs.