title: Noninvasive optical imaging of cysteine protease activity using fluorescently quenched activity-based probes.
abstract: We have generated a series of quenched near-infrared fluorescent activity-based probes (qNIRF-ABPs) that covalently target the papain-family cysteine proteases shown previously to be important in multiple stages of tumorigenesis. These 'smart' probes emit a fluorescent signal only after covalently modifying a specific protease target. After intravenous injection of NIRF-ABPs into mice bearing grafted tumors, noninvasive, whole-body imaging allowed direct monitoring of cathepsin activity. Importantly, the permanent nature of the probes also allowed secondary, ex vivo biochemical profiling to identify specific proteases and to correlate their activity with whole-body images. Finally, we demonstrate that these probes can be used to monitor small-molecule inhibition of protease targets both biochemically and by direct imaging methods. Thus, NIRF-ABPs are (i) potentially valuable new imaging agents for disease diagnosis and (ii) powerful tools for preclinical and clinical testing of small-molecule therapeutic agents in vivo.
authors.affiliation: Department of Pathology, Stanford University School of Medicine, 300 Pasteur Dr., Stanford, California 94305, USA.
authors.forename: Galia
authors.initials: G
authors.lastname: Blum
authors.forename: Georges
authors.initials: G
authors.lastname: von Degenfeld
authors.forename: Milton J
authors.initials: MJ
authors.lastname: Merchant
authors.forename: Helen M
authors.initials: HM
authors.lastname: Blau
authors.forename: Matthew
authors.initials: M
authors.lastname: Bogyo
mesh_terms: D000818:Animals; D002403:Cathepsins / Q000032:analysis* / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D003952:Diagnostic Imaging / Q000379:methods*; D004591:Electrophoresis, Polyacrylamide Gel; D005456:Fluorescent Dyes / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008856:Microscopy, Fluorescence; D009369:Neoplasms / Q000473:pathology / Q000648:ultrastructure; D012680:Sensitivity and Specificity; D013997:Time Factors; D051598:Whole Body Imaging / Q000379:methods*