title: Fluorophore-quencher based activatable targeted optical probes for detecting in vivo cancer metastases.
abstract: In vivo molecularly targeted fluorescence imaging of tumors has been proposed as a strategy for improving cancer detection and management. Activatable fluorophores, which increased their fluorescence by 10-fold after binding tumor cells, result in much higher target to background ratios than conventional fluorophores. We developed an in vivo targeted activatable optical imaging probe based on a fluorophore-quencher pair, bound to a targeting moiety. With this system, fluorescence is quenched by the fluorophore-quencher interaction outside cancer cells, but is activated within the target cells by dissociation of the fluorophore-quencher pair. We selected the TAMRA (fluorophore)-QSY7 (quencher) pair and conjugated it to either avidin (targeting the D-galactose receptor) or trastuzumab (a monoclonal antibody against the human epithelial growth factor receptor type2 (HER2/neu)) and evaluated their performance in mouse models of cancer. Two probes, TAMRA-QSY7 conjugated avidin (Av-TM-Q7) and trastuzumab (Traz-TM-Q7) were synthesized. Both demonstrated better than similar self-quenching probes. In vitro fluorescence microscopic studies of SHIN3 and NIH/3T3/HER2+ cells demonstrated that Av-TM-Q7 and Traz-TM-Q7 produced high intracellular fluorescent signal. In vivo imaging with Av-TM-Q7 and Traz-TM-Q7 in mice enabled the detection of small tumors. This molecular imaging probe, based on a fluorophore-quencher pair conjugated to a targeting ligand, successfully detected tumors in vivo due to its high activation ratio and low background signal. Thus, these activatable probes, based on the fluorophore-quencher system, hold promise clinically for "see and treat" strategies of cancer management.
authors.affiliation: Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 10 Center Drive, Bethesda, Maryland 20892-1088, USA.
authors.forename: Mikako
authors.initials: M
authors.lastname: Ogawa
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kosaka
authors.forename: Michelle R
authors.initials: MR
authors.lastname: Longmire
authors.forename: Yasuteru
authors.initials: Y
authors.lastname: Urano
authors.forename: Peter L
authors.initials: PL
authors.lastname: Choyke
authors.forename: Hisataka
authors.initials: H
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D061067:Antibodies, Monoclonal, Humanized; D001360:Avidin / Q000737:chemistry / Q000378:metabolism; D041702:BALB 3T3 Cells; D005260:Female; D005456:Fluorescent Dyes / Q000737:chemistry; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000556:secondary*; D051379:Mice; D008819:Mice, Nude; D008856:Microscopy, Fluorescence; D041681:NIH 3T3 Cells; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D012235:Rhodamines / Q000737:chemistry; D014162:Transfection; D000068878:Trastuzumab
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D001360:Avidin; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D011956:Receptors, Cell Surface; D012235:Rhodamines; D000068878:Trastuzumab; C114557:5-carboxytetramethylrhodamine succinimidyl ester; C485184:enhanced green fluorescent protein; C039707:galactose receptor; C521811:herceptin-rhodamine green conjugate