In vivo imaging of proteolytic enzyme activity using a novel molecular reporter.

TitleIn vivo imaging of proteolytic enzyme activity using a novel molecular reporter.
Publication TypeJournal Article
Year of Publication2000
AuthorsTung CH, Mahmood U, Bredow S, Weissleder R
JournalCancer Res
Volume60
Issue17
Pagination4953-8
Date Published2000 Sep 01
ISSN0008-5472
KeywordsAnimals, Cathepsin D, Fluorescent Dyes, Image Processing, Computer-Assisted, Mice, Mice, Nude, Neoplasm Transplantation, Neoplasms, Experimental, Oligopeptides, Peptide Hydrolases, Polyethylenes, Polylysine, Rats, Reverse Transcriptase Polymerase Chain Reaction, Spectroscopy, Near-Infrared, Substrate Specificity, Tumor Cells, Cultured
Abstract

The single biggest challenge facing in vivo imaging techniques is to develop biocompatible molecular beacons that are capable of specifically and accurately measuring in vivo targets at the protein, RNA, or DNA level. Our efforts have focused on developing activatable imaging probes to measure specific enzyme activities in vivo. Using cathepsin D as a model target protease, we synthesized a long-circulating, synthetic graft copolymer bearing near-infrared (NIR) fluorochromes positioned on cleavable substrate sequences. In its native state, the reporter probe was essentially nonfluorescent at 700 nm due to energy resonance transfer among the bound fluorochromes (quenching) but became brightly fluorescent when the latter were released by cathepsin D. NIR fluorescence signal activation was linear over at least 4 orders of magnitude and specific when compared with scrambled nonsense substrates. Using matched rodent tumor models implanted into nude mice expressing or lacking the targeted protease, it could be shown that the former generated sufficient NIR signal to be directly detectable and that the signal was significantly different compared with negative control tumors. The developed probes should find widespread applications for real-time in vivo imaging of a variety of clinically relevant proteases, for example, to detect endogenous protease activity in disease, to monitor the efficacy of protease inhibitors, or to image transgene expression.

Alternate JournalCancer Res
PubMed ID10987312
Grant ListR21-DK55713-01 / DK / NIDDK NIH HHS / United States
Related Institute: 
Molecular Imaging Innovations Institute (MI3)

Weill Cornell Medicine
Department of Radiology
525 East 68th Street New York, NY 10065