Abstract 5706: Engineering of trans kingdom RNAi (tkRNAi) against gastrointestinal polyps

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Trans Kingdom RNAi (tkRNAi) is a technology where nonpathogenic bacteria synthesize and deliver shRNA. CEQ508 is our orally delivered tkRNAi clinical candidate for delivery to intestinal polyp cells in patients with Familial Adenomatous Polyposis. CEQ508 is an E. coli that has Δrnc and ΔdapA mutations engineered in its genome, harboring a plasmid called pMBV43 encoding invasin, listeriolysin O (LLO) and a shRNA expression cassette. It is the concerted expression of these elements that provides the specificity and high activity of the tkRNAi platform. The shRNA in CEQ508 targets β-catenin in cancerous polyp cells. CEQ508 expresses Yersinia pseudotuberculosis invasin enabling β1-integrin-dependent cellular internalization. Bacterial death due to phagosome action is enhanced by the cell-wall weakening ΔdapA attenuation. LLO expression provides for efficient intracellular release to the cytoplasm by lysis of the phagosome. The shRNA expression cassette allows for precise initiation and termination of the shRNA transcript, and Δrnc removes the only dsRNA-specific RNase (RNase III) from the E. coli genome, leading to significant accumulation of the expressed shRNA. Following Dicer processing and incorporation into RISC, cleavage of β-catenin mRNA induces death of the targeted cancerous cells. Thus, the tkRNAi approach allows effective local delivery of shRNA to mediate RNA interference. Since the “external” body surfaces such as GI tract, GU tract, upper respiratory tract and skin are colonized with bacterial species, this approach can be extended to other indications by the combination of genetic engineering of a carrier bacteria, expression of cell-specific targeting entities, and expression of one or more shRNA sequences against disease-relevant targets. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5706. doi:1538-7445.AM2012-5706