(628a) Synergistic Approaches to Enhance Transgene Expression Efficacy of Polymer-DNA Complexes

Low levels of transgene expression associated with non-viral vectors limits their development as safer alternatives to viral vectors for therapeutic gene delivery. In particular, various delivery barriers including DNA binding, cellular uptake, cytoplasmic trafficking, escape from degradative pathways, and nuclear entry result in low transgene expression levels inside cells. We outline a new approach for enhancing polymer-mediated transgene expression in which we synergistically combine engineering of new materials with simultaneous administration of small-molecule chemotherapeutic drugs. A parallel synthesis and high-throughput screening was first employed in order to identify cationic polymers that demonstrated higher transgene expression and lower cytotoxicity towards prostate cancer cells than a current polymer standard, 25-kDa polyethylene imine (pEI-25). Drugs that inhibit specific intracellular targets, which form transport barriers to nanoscale polymer-plasmid DNA complexes, were then investigated for enhancing the transgene expression following plasmid DNA delivery using high-efficacy polymers identified from the screen. In particular, chemotherapeutic mediators of intracellular trafficking and transcription, in particular cytoplasmic and nuclear histone deacetylase inhibitors (HDACi), were employed. In addition to HDACi, we recently employed chemotherapeutic mediators of cell cycle progression, which also led to a significant enhancement of polymer-mediated transgene expression. Synergistic use of high-efficacy polymers and intracellular target-specific chemotherapeutics is an attractive combination treatment strategy that can overcome low efficacies typically associated with non-viral gene delivery vectors and can accelerate their use in the clinic.