Abstract 2164: Tenascin-C binding peptides for cancer targeting

Abstract

Abstract Extracellular matrix protein tenascin C (TNC) is strongly overexpressed in the stroma of many solid tumors. TNC expression is upregulated at the invasive front of tumors while being nearly undetectable in normal adult tissues. TNC-targeted humanized antibodies are undergoing clinical development for targeting compounds to solid tumors. Compared to antibodies, homing peptides may have more favorable extravasation and tumor penetration properties. We used in vitro T7 peptide display to identify peptides that bind to the alternatively spliced domain C of the large isoform of Tenascin-C (TNC FnIIIC). The selected phage pool showed 500-fold increase in binding to immobilized TNC FnIIIC. Candidate TNC FnIIIC-binding peptides (designated PL1- 3) were found to bind to TNC FnIII C protein, to the extracellular matrix extracted from PC3 prostate tumors and to cultured tumor cells known to overexpress TNC. To evaluate candidate peptides in vivo, we used mice bearing patient-derived xenografts of P3 glioma (R. Bjerkvig, Bergen, Norway), 4T1 breast tumors, and PC-3prostate carcinoma. A pool of the phages displaying TNC FnIIIC binding peptides, and a panel of phages displaying published tumor homing and control peptides was injected intravenously in tumor-bearing mice, and relative tumor homing and background in control tissues was determined for each phage using high-throughput sequencing (HTS) of phage genomic DNA. These studies demonstrated that among TNC FnIIIC targeting peptides, the PL3 peptide showed the best tumor homing and specificity profile. To evaluate the potential of the synthetic PL3 peptide for tumor targeting of nanoparticles, we coupled PL3 peptide to iron oxide nanoworms (IONW) - paramagnetic nanoparticles that are PEGylated to extend blood half-life, and have because of their elongated shape more effective targeting properties than spherical nanoparticles. 5 hours after intravenous administration of 7.5mg/kg of IONW in mice bearing PC3 prostate cancer xenografts, PL3-IONW but not control IONW showed a robust accumulation in tumor vasculature, and some extravasation into extravascular tumor tissue. Our data suggests that the newly identified TNC FnIIIC targeting peptide, PL3, may be used for payload delivery into tumor stroma. Currently, we are evaluating PL3-targeted IONWs as a MRI contrast agent and as carriers for cytotoxic compounds to TNC expressing tumors. Citation Format: Prakash Lingasamy, Allan Tobi, Hedi Hunt, Pille Säälik, Markko Salumäe, Tambet Teesalu, Tambet Teesalu. Tenascin-C binding peptides for cancer targeting. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2164.