Abstract IA1: Building molecules to guide anticancer therapy

Abstract

Abstract For clinical imaging, we need synthetic molecules with novel amplifying mechanisms for homing to diseased tissues. Activatable cell penetrating peptides (ACPPs) are polycationic cell penetrating peptides (CPPs) whose cellular uptake is minimized by a polyanionic inhibitory domain and then restored upon proteolysis of the peptide linker connecting the polyanionic and polycationic domains. Local activity of proteases able to cut the linker causes amplified retention in tissues and uptake into cells. ACPPs on dendrimers labeled with Cy5 and Gd-DOTA enable whole body magnetic resonance imaging (Olson et al (2010) PNAS 107: 4311–4316) followed by fluorescenceguided surgery. Such fluorescence guidance improves tumor-free survival in two animal models (Nguyen et al (2010) PNAS 107: 4317–4322). Contrast for tumor over normal tissues is amplified and accelerated when the polyanionic domain includes an acceptor of fluorescence resonance energy transfer (FRET), because loss of FRET (monitored either by multispectral emission or donor excited-state lifetime) instantly signals proteolysis without waiting for uncleaved substrate to wash out of normal tissues. Thrombin-cleavable ACPPs accumulate in atherosclerotic plaques, and their labeling intensity seems to correlate with progression towards rupture. Separately, we have developed fluorescent peptides that light up peripheral nerves to show surgeons where not to cut (Whitney et al (2011) Nature Biotech. 29: 352–356). Thus we believe that basic tumor biology and molecular design can help improve early detection and surgical resection, not just chemotherapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr IA1.