Abstract 3543: Ligand-directed and transcription-based molecular imaging and treatment of cancer
Authors: Dobroff Andrey S. , Eckhardt Bedrich L. , Salmeron Carolina C. , Cimino Daniel F. , Arap Wadih , Pasqualini Renata 
Published: August 2015

Abstract
Inflammatory breast cancer (IBC) is a rare and aggressive disease that progresses rapidly, often in a matter of weeks or months. In the United States, IBC accounts for 1 to 5 percent of all breast cancers diagnosed per year. Due to the lack of reliable and effective detection methods, IBC can be difficult to diagnose and thus, it is more likely to have metastasized by the time it is identified. Specific delivery of drugs and/or imaging agents to tumors takes advantage of dynamic molecular addresses on the surface of tumor cells and the tumor vasculature through inherent receptor/ligand interactions. By using a combinatorial phage display library in vivo (consisting of more than 1×109unique CX(7/8)C amino acid residues) we identified an unique peptide sequence - WIFPWIQL - that mediates targeting to breast cancer metastasis. We further validated that the WIFPWIQL peptide specifically binds to the stress-response 78 kDa glucose-regulated protein (GRP78), expressed at the cell surface of IBC tumors. GRP78 expression is elevated with breast cancer progression, and correlates with metastatic disease in IBC. Using near infrared (NIR) fluorescent-tagged phage variants and/or antibody fragments, we demonstrate WIFPIWIQL specifically targets breast tumors in vivo. As a therapeutic approach, we coupled a toxic apoptotic moiety D(KLAKLAK)2 - to the WIFPWIQL peptide to create BMTP-78. BMTP-78 is cytotoxic to cultured IBC cells in vitro. Furthermore, BMTP-78 prevents the growth of IBC tumor xenografts, reduces tumor burden and mitigates metastasis in breast cancer pre-clinical models. Taking into consideration that phage particles can be adapted to transduce mammalian cells by targeting a specific receptor, we developed a unique phage-based targeted vector by combining genomic elements from adeno-associated virus (AAV) and an M13-derived phage (P) - termed AAVP. AAVP chimeras are able to deliver reporter genes that can be used to image, diagnose and treat pre-clinical breast cancer. In our initial in vivo assessment, AAVP particles harboring the tumor targeting peptide, WIFPWIQL, delivered the Herpes Simplex Virus thymidine kinase gene (HSVtk) driven by the CMV promoter, to EF43.fgf-4 mouse mammary tumors after a single intravenous injection. Positron emission tomography (PET) studies demonstrated WIFPIWIQL-targeted AAVP-HSKtk tumors could be non-invasively imaged. More importantly, transcriptional targeting of AAVP vectors was achieved by replacing the CMV promoter with a human GRP78 promoter that selectively controls transgene expression and allows molecular imaging of breast tumors in real time. Taken together, our data presents a GRP78 receptor/ligand system that can be used to specifically image and target breast tumors. Our findings infer potential clinical applications of AAVP for targeted detection and eradication of IBC tumors via a GRP78-targeted mechanism in a disease for which no effective treatment currently exists.
Citation Format: Andrey S. Dobroff, Bedrich L. Eckhardt, Carolina C. Salmeron, Daniel F. Cimino, Wadih Arap, Renata Pasqualini. Ligand-directed and transcription-based molecular imaging and treatment of cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3543. doi:10.1158/1538-7445.AM2015-3543