A platform for next-generation cancer therapies: multi-targeted nonviral vectors for site-specific gene delivery and expression

Abstract

Advances in genetics have empowered gene therapy as a cancer treatment, however there are many challenges to delivering genes specifically to target disease sites. Presented here is the development of a new non-viral gene delivery vehicle, consisting of branched polyethyleneimine (bPEI) condensed plasmid DNA polyplexes encapsulated within a PR_b functionalized stealth liposome, for the delivery of genes specifically to &alpha₅&beta₁ integrin overexpressing cancer cells. This new transfection agent mediated higher gene expression than non-targeted stealth liposomes and unencapsulated polyplexes in tissue culture. In a liver-metastatic colorectal cancer mouse model, PR_b functionalized stealth liposomes outperformed non-targeted stealth liposomes and was able to specifically transfect the tumor site while avoiding healthy tissues. In addition, a comparative investigation of the transfection mechanism of PR_b functionalized nanoparticles, DOTAP/DOPE lipoplexes, bPEI polyplexes and stealth liposomes was carried out in DLD-1 cells. Results demonstrated that PR_b functionalized nanoparticles were optimally balanced for the transfection of DLD-1 cells with high colloidal stability, fast integrin mediated internalization kinetics, caveolae mediated uptake and endosomal escape. To further increase the specificity of gene expression in cancer tissue, a new therapeutic plasmid DNA (pNF-&kappaB-DTA) was developed with expression of Diphtheria toxin fragment-A (DTA) gene regulated by the transcriptional activity of NF-&kappaB, which is a transcription factor upregulated in cancer. The multi-targeted gene delivery system formed by encapsulating pNF-&kappaB-DTA/bPEI polyplexes in PR_b functionalized stealth liposomes showed more specific gene expression in cancer cells versus healthy cells compared to either individually targeted system. Transfecting cancer cells using the multi-targeted gene delivery system resulted in a dose-dependent reduction of cellular protein expression and a dose-dependent increase in cytotoxicity. Our therapeutic delivery system specifically eradicated on average 70% of a variety of cancer cells while minimally affecting healthy cells. Moving forward, the modular nature of our non-viral delivery vehicle design can facilitate targeting novel pairs of extracellular receptors and upregulated transcription factors for applications beyond cancer gene therapy.