Endothelial Cell-Specific Expression of Tumor Necrosis Factor- α from the KDR or E-Selectin Promoters Following Retroviral Delivery

Abstract

The tumor vasculature offers a target for anti-cancer gene therapy which has the advantages both of good accessibility to systemically delivered therapy and comparative homogeneity across solid tumor types. We aimed to develop retroviruses carrying endothelial-specific promoters for the delivery of genes to proliferating endothelial cells in vitro and to tumor endothelial cells in vivo. This paper reports the generation of such retroviral vectors and the level of expression of murine tumor necrosis factor-α (mTNF-α) cDNA following infection into endothelial cells and stromal fibroblasts. Retroviral vectors carrying mTNF-α have been generated whose expression is controlled either by the retroviral long terminal repeat or by 5′ proximal promoter sequences from the endothelial-specific kinase insert domain receptor (KDR)/VEGF receptor and E-Selectin promoters within the context of a self-inactivating (SIN) vector backbone. Both KDR and E-Selectin have been shown to be upregulated on tumor endothelium. A putative polyadenylation sequence AAATAAA within the E-Selectin promoter was mutated to permit faithful transmission of retroviral vectors carrying this promoter. We demonstrate a 10- to 11-fold increase in mTNF-α expression from promoter elements within sEND endothelioma cells as compared to NIH-3T3 fibroblasts. Suggestions for further improvements in vector design are discussed.

Overview summary

Tumor growth is critically dependent on angiogenesis. Targeting the proliferating tumor vasculature, therefore, offers a general strategy for anti-cancer gene therapy. This study describes the development and characterization of retroviral vectors carrying the kinase insert domain receptor (KDR) and E-Selectin promoters (whose genes are upregulated on tumor endothelium) directing the expression of tumor necrosis factor-α, which is toxic specifically for proliferating endothelial cells. The use of gene therapy vehicles using endothelial specific promoters may lead, in future, to novel therapeutic approaches to the treatment of cancer.