Genetic approaches to the therapy of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a devastating malignancy originating from hepatocytes. There is an urgent need for novel therapeutic approaches. Currently explored gene therapy systems have not yet achieved significant survival benefits. The aim of this thesis was the development and evaluation of novel genetic approaches to this malignancy. The results of this thesis show that the only non-conjugated gene delivery system achieving significant intratumoral transgene expression is direct injection. Systemic gene delivery systems based upon Tf-shielded, polyethylenimine (PEI) based polyplexes and stabilized plasmid lipid particles (SPLP) do achieve efficient intratumoral transgene expression levels comparable to direct intratumoral injection, but their use is limited by their low intratumoral biodistribution. Further, this study shows that the use of non-viral replicon vectors based on the autonomously replicating parvoviruses minute virus of mice (pMVM) is feasible. In contrast to its viral equivalent, it allows expansion of its genome size to >106% and avoids immunogenicity. It maintains its tumorselectivity, but loses its cytotoxicity. The results of this thesis show that the Edmonston strain of measles virus (MV-Edm) efficiently infects human HCC cell lines resulting in syncytia formation followed by apoptotic cell death. The use of recombinant MV-Edm expressing marker genes allows non-invasive tracking of MV-Edm infection and kinetics. Treatment of mice bearing subcutaneous human HCC xenografts with recombinant MV-Edm resulted in significant survival benefits and tumor regression in up to one third of animals