We have previously shown that ligand-mediated delivery of a toxin kills proliferating cells bering cognate receptors. Basic fibroblast growth factor (FGF2) fused to a ribosome inhibiting protein, saporin, targets smooth muscle cells (SMC) in the injured arterial wall, and inhibits intimal hyperplasia in rat, rabbit, and dog models of arterial injury. Killing within the neointima and media is FGF receptor dependent. To increase targeting specificity to only the proliferating cells within the lesion, and not to extravascular targets, we plan to investigate FGF2- mediated delivery of DNA into SMC. If the DNA contains an upstream transcriptional control element preferentially active in proliferating arterial SMC, a second layer of selectivity would be introduced to eliminate unwanted toxicity toward other proliferating cell types expressing FGF receptors. Therefore, we will develop constructs of FGF2 with DNA for reporter genes and saporin, using an SMC alpha-actin promoter. We will investigate (1) optimal targeting of the DNA to FGF receptor bearing cultured SMC, (2) in vivo selectivity in FGF receptor and SMC alpha-actin containing vascular cells following intravenous injection, and (3) whether saporin DNA, when delivered by FGF2 under the control of the SMC alpha-actin promoter, can reduce intimal hyperplasia in the injured rabbit arterial wall.
The proposed studies are designed to develop highly specific anti-proliferative agents for the treatment of vascular restenosis and vascular graft stenosis. The therapeutic construct to be evaluated targets FGF receptor bearing smooth muscle cells within the vascular injury. FGF2 delivers into these cells the DNA encoding the cytotoxic protein saporin, under the control of a tissue- specific promoter. Therapeutic specificity is increased by decreasing toxicities in other tissues containing FGF receptors since the tissue specific promoter is not activated in these tissues. These studies will provide in vivo proof-of-concept for ligand-mediated gene delivery as a broad-based platform for design of other anti-proliferative agents to treat cardiovascular diseases.
