Thioredoxin (Trx), a small redox protein, is overexpressed in a number of tumors, however, its roles in tumor cells were not defined well. To investigate the effect of Trx, we transfected Trx or antisense Trx vectors into HT1080 cells. Trx-overexpressed HT1080 cells induced migration of endothelial cells through Flt-1 vascular endothelial growth factor (VEGF) receptor type-1. However, the migration was reduced by overexpression of antisense-Trx. To understand the relationship between Trx and hypoxia-induced angiogenesis, we observed the expression level of VEGF and hypoxia-inducible factor-1α (HIF-1α) after transfection of Trx. Overexpression of Trx also caused a significant increase of VEGF in protein and RNA levels under normoxic and hypoxic conditions. Moreover, transfection of Trx caused a dramatic increase in HIF-1α protein level under hypoxic condition. However, transfection of antisense-Trx markedly decreased HIF-1α and VEGF expression compared with controls. In addition, HIF-1α was not translocated from cytoplasm to nucleus in antisense-Trx overexpressing HT1080 cells. Further, we could detect the association of HIF-1α and pVHL in antisense-Trx transfectant HT1080 cells. Taken together, we suggest that Trx plays an important role in angiogenesis and, therefore, antisense-Trx might be applicable to the inhibition of tumor angiogenesis through the induction of pVHL-mediated HIF-1α degradation.

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