Increasing cancer-specific gene expression by targeting overexpressed α₅β₁ integrin and upregulated transcriptional activity of NF-κB

We developed a modular multifunctional nonviral gene delivery system by targeting the overexpressed cancer surface receptor α₅β ₁ integrin and the upregulated transcriptional activity of the cancer resistance mediating transcription factor NF-κB, thereby introducing a new form of transcriptional targeting. NF-κB regulated therapy can improve specificity of gene expression in cancer tissue and also may offset NF-κB mediated cancer resistance. We delivered a luciferase gene under the control of an NF-κB responsive element (pNF-κB-Luc) encapsulated in a PR-b peptide functionalized stealth liposome that specifically targets the α₅β₁ integrin and achieved increased gene expression in DLD-1 colorectal cancer cells compared to BJ-fibroblast healthy cells in vitro. The multitargeted system was also able to differentiate between cancer cells and healthy cells better than either of the individually targeted systems. In addition, we constructed a novel cancer therapeutic plasmid by cloning a highly potent diphtheria toxin fragment A (DTA) expressing gene under the control of an NF-κB responsive element (pNF-κB-DTA). A dose-dependent reduction of cellular protein expression and increased cytotoxicity in cancer cells was seen when transfected with PR-b functionalized stealth liposomes encapsulating the condensed pNF-κB-DTA plasmid. Our therapeutic delivery system specifically eradicated close to 70% of a variety of cancer cells while minimally affecting healthy cells in vitro. Furthermore, the modular nature of the nonviral design allows targeting novel pairs of extracellular receptors and upregulated transcription factors for applications beyond cancer gene therapy.