A Highly Specific, Tissue-Permeable Inhibitor of Gli Transcription Factors

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DESCRIPTION (provided by applicant): Aberrant signaling of the Hedgehog (Hh) pathway is heavily linked to the formation and progression of basal cell carcinomas (BCC), a skin cancer that affects 3 in 10 Caucasians. The standard treatment of BCC involves surgical excision of the entire tumor, but this procedure can leave heavy scarring. Researchers have been studying alternate therapy options that act by chemically inhibiting the Hh pathway. Most therapies so far inhibit smoothened (Smo), an upstream member of the Hh pathway, but the pathway later develops resistance. Thus, the proposed project aims to target Gli proteins, a set of zinc finger transcription factors (TFs) that act as the terminal step in the Hh pathway. Professor Meade's lab has developed a series of cobalt(III)-Schiff base (Co(III)-sb) complexes that are highly specific and irreversible inhibitors of zinc finger TFs. By conjugating Co(III)-sb to the Gli targe binding sequence (5'-GACCACCCA-3') to make Co(III)-Gli, highly specific and potent inhibition of Gli proteins is anticipated. This proposal additionally seeks to attach fluorescently modified Co(III)-Gli inhibitor to a gold nanoparticle (AuNP), making "Au-Gli-Co." This will allow for: 1) topical delivery of the Gli inhibitor, 2) localized delivery, since Co(III)-Gli can be released fro the AuNP by inducing with light, and 3) facile visualization and tracking of the fluorescent active agent in vitro and in vivo. The first objective of the proposal is to synthesize and characterize the unique Au-Gli-Co particle. Co(III)-Gli will be attached to the AuNP using DNA hybridization methods. It can become dehybridized (and therefore released) from the AuNP using near-infrared light, which causes AuNP plasmon resonance and generates heat. The second and third objectives are to validate Hh pathway inhibition in vitro and in vivo. Cellular experiments will be performed on two cells lines to determine the inhibitor's efficacy and specificity for targeting Gli. A 3D raft cultre model will be used to assess tissue penetration and cellular delivery. In vivo experiments will determine the ability of the agent to treat BCC tumors after topical application and laser activation. A mouse model that expresses Hh-mediated BCC tumors upon induction with tamoxifen will be used. This proposal meets the long-range research and funding plans of the NIAMS. The project involves the development of a new skin cancer treatment with the use of small molecules, in addition to proposing an efficient and controlled system of transcutaneous drug delivery. It could have application in treating early or later stage BCC. Like many skin diseases, BCC tends to garner less attention than more aggressive cancers, but the successful implementation of this project would have significant implications in improving patients' quality of life.