UC San Diego

This dissertation aims to validate that molecular targeting with activatable cell penetrating peptides (ACPPs) and nerve-homing peptides (NHPs) improve imaging and therapeutic delivery techniques in order to combat the progression of cancer. ACPPs successfully identify and mediated therapeutic delivery to cancer cells and NHPs distinguish nerves from surrounding tissue, with the goal of reducing surgically related morbidity during tumor resection. ACPPs are protease sensitive peptides that once cleaved by their target enzyme become a powerful tool for probe retention and cellular uptake. When administered systemically, ACPPs provide significant contrast for both primary tumors and metastatic lesions. The first portion of this thesis focuses on ACPPs that are activated by matrix metalloproteinases (MMPs) because upregulation of these enzymes is well documented in tumorgenesis. However, substrate specificity, turnover and pharmacokinetic properties of the peptide can be improved. Multiple peptide constructs were tested with these goals in mind and the modification that yielded the best result was the addition of cyclic-RGD, a common ligand for integrins overexpressed in neovasculature. The combination of integrin and MMP targeting significantly enhanced tumor contrast and peptide uptake and provided the first results where ACPP mediated delivery improved the efficacy of a chemotherapeutic drug. ACPP targeting was also tested with Doxil, the FDA approved liposomal formulation of doxorubicin, and in vivo testing with this construct has laid the groundwork for translation of ACPP targeting to other nanoparticle therapeutics. Moving beyond MMPs, a novel phage display selection scheme identified an ACPP substrate sequence, RLQLKL, that was a target for tumor associated elastases. Further characterization of this probe revealed that is also a marker for macrophages that are involved in metastatic progression. Finally, NHPs provide significant nerve contrast when imaged in a surgical setting and can be combined with ACPPs to navigate tumor resection during fluorescent-guided surgery. The combination of these molecularly targeted peptides can facilitate the identification of cancer in vivo, increase the efficacy of chemotherapeutics and will lead to improvements in early detection and tumor resection, which are the ultimate cures for cancer