title: In vivo molecular imaging of cancer with a quenching near-infrared fluorescent probe using conjugates of monoclonal antibodies and indocyanine green.
abstract: Near-infrared (NIR) fluorophores have several advantages over visible fluorophores, including improved tissue penetration and lower autofluorescence; however, only indocyanine green (ICG) is clinically approved. Its use in molecular imaging probes is limited because it loses its fluorescence after protein binding. This property can be harnessed to create an activatable NIR probe. After cell binding and internalization, ICG dissociates from the targeting antibody, thus activating fluorescence. ICG was conjugated to the antibodies daclizumab (Dac), trastuzumab (Tra), or panitumumab (Pan). The conjugates had almost no fluorescence in PBS but became fluorescent after SDS and 2-mercaptoethanol, with a quenching capacity of 10-fold for 1:1 conjugates and 40- to 50-fold for 1:5 conjugates. In vitro microscopy showed activation within the endolysosomes in target cells. In vivo imaging in mice showed that CD25-expressing tumors were specifically visualized with Dac-ICG. Furthermore, tumors overexpressing HER1 and HER2 were successfully characterized in vivo by using Pan-ICG(1:5) and Tra-ICG(1:5), respectively. Thus, we have developed an activatable NIR optical probe that "switches on" only in target cells. Because both the antibody and the fluorophore are Food and Drug Administration approved, the likelihood of clinical translation is improved.
authors.affiliation: Molecular Imaging Program, Center for Cancer Research, National Cancer Institute/NIH, 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: Peter L
authors.initials: PL
authors.lastname: Choyke
authors.forename: Hisataka
authors.initials: H
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000077561:Daclizumab; D005456:Fluorescent Dyes; D007074:Immunoglobulin G; D007208:Indocyanine Green; D053645:Interleukin-2 Receptor alpha Subunit / Q000032:analysis; D051379:Mice; D008856:Microscopy, Fluorescence; D009374:Neoplasms, Experimental / Q000473:pathology; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis; D013050:Spectrometry, Fluorescence; D013055:Spectrophotometry, Infrared
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000077561:Daclizumab; D005456:Fluorescent Dyes; D007074:Immunoglobulin G; D007208:Indocyanine Green; D053645:Interleukin-2 Receptor alpha Subunit; D018719:Erb-b2 Receptor Tyrosine Kinases; C524056:Erbb2 protein, mouse