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 α₅β₁ 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 <i>in vitro</i>. 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 <i>in vitro</i>. 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