title: An enzymatically activated fluorescence probe for targeted tumor imaging.
abstract: Beta-galactosidase is a widely used reporter enzyme, but although several substrates are available for in vitro detection, its application for in vivo optical imaging remains a challenge. To obtain a probe suitable for in vivo use, we modified our previously developed activatable fluorescence probe, TG-betaGal (J. Am. Chem. Soc. 2005, 127, 4888-4894), on the basis of photochemical and photophysical experiments. The new probe, AM-TG-betaGal, provides a dramatic fluorescence enhancement upon reaction with beta-galactosidase, and further hydrolysis of the ester moiety by ubiquitous intracellular esterases affords a hydrophilic product that is well retained within the cells without loss of fluorescence. We used a mouse tumor model to assess the practical utility of AM-TG-betaGal, after confirming that tumors in the model could be labeled with an avidin-beta-galactosidase conjugate. This conjugate was administered to the mice in vivo, followed by AM-TG-betaGal, and subsequent ex vivo fluorescence imaging clearly visualized intraperitoneal tumors as small as 200 microm. This strategy has potential clinical application, for example, in video-assisted laparoscopic tumor resection.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Mako
authors.initials: M
authors.lastname: Kamiya
authors.forename: Hisataka
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Hama
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Koyama
authors.forename: Marcelino
authors.initials: M
authors.lastname: Bernardo
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Nagano
authors.forename: Peter L
authors.initials: PL
authors.lastname: Choyke
authors.forename: Yasuteru
authors.initials: Y
authors.lastname: Urano
mesh_terms: D000818:Animals; D002460:Cell Line; D004950:Esterases / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D051379:Mice; D015394:Molecular Structure; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000201:enzymology* / Q000473:pathology*; D010084:Oxidation-Reduction; D013552:Swine; D001616:beta-Galactosidase / Q000378:metabolism*
chemical_list: D005456:Fluorescent Dyes; D004950:Esterases; D001616:beta-Galactosidase