(392b) Trafficking of Nanoparticles to Intracellular Aggresome-Like Strucutres: Implications for Non-Viral Gene Delivery

Nanoscale therapeutics, including nonviral gene delivery systems, have been investigated for a variety of cancer cell types. However, the efficacy of these therapeutics is compromised by cancer cell resistance mechanisms. The inefficient sub-cellular delivery of nanoparticles is of particular relevance to nanoscale therapeutics. Consequently, investigations into the role of cancer cell phenotype in the cellular uptake, intracellular sorting, transport, and sub-cellular localization can lead to improved efficacies of nanoscale therapeutics.

Here we show that phenotypic differences in human prostate cancer cells lead to dramatic differences in intracellular sorting and localization of exogenous nanomaterials including nanoparticles (quantum dots), polymer:DNA, and polymer:siRNA complexes. These nanoparticles demonstrate a punctated intracellular localization throughout the cytoplasm in PC3 cells. In contrast, the materials were taken up by clathrin-mediated endocytosis and trafficked along microtubules, resulting in their localization in aggresome-like compartments in PC3-PSMA cells (sub-clones of PC3 cells retrovirally transduced to stably express PSMA receptors).

We hypothesized that localization of polymer:DNA complexes in aggresome-like compartments was a major barrier to the transport of genes to the nucleus and therefore, is responsible for low transfection efficacies. We have recently generated polymers that show increased transfection efficacies and lower cytotoxicities than polyethyleneimine, a current standard for polymer-mediated gene delivery. Intracellular trafficking studies indicated co-localization of quantum dots and polymer:plasmid DNA polylexes in juxtanuclear aggresome-like structures in PC3-PSMA cells. Confocal microscopy studies were carried out to characterize the nature of the aggresome-like compartment. In contrast, QDs and polyplexes colocalized in punctate vesciles throughout the cytoplasm of PC3 cells. Comparison between PC3 and PC3-PSMA cells indicated higher transfection efficacies in PC3 cells compared to PC3-PSMA cells, which correlated with the formation of aggresome-like structures. Strategies for overcoming this intracellular barrier to gene and siRNA delivery were investigated. Our results provide a platform to understand mechanisms behind the resistance of certain cancer cell types to gene and siRNA delivery and describe opportunities for overcoming these resistance mechanisms for nanoscale therapeutics.