Tumor-targeted gene delivery: an attractive strategy to use highly active effector molecules in cancer treatment.

We have developed surface-shielded ligand-polycation based gene delivery systems which are able to target gene expression to distant tumors after systemic application. Tumor-specific targeting is achieved by (1) incorporation of cell-binding ligands; and (2) shielding of the complexes from non-specific interactions with blood components and non-target cells. Shielding of polycation/DNA complexes can be achieved by coating with either polyethylene glycol or by incorporating the ligand transferrin at high densities. Following systemic application, surface-shielded DNA complexes coding for a highly active, yet highly toxic cytokine, tumor necrosis factor-alpha (TNFalpha), localized gene expression to distant tumors, resulting in hemorrhagic tumor necrosis and inhibition of tumor growth. TNFalpha activity was confined to the tumor without systemic TNF-related toxicity. These results indicate that targeted gene delivery may be an attractive strategy to use highly potent molecules in cancer treatment.