title: In vivo stable tumor-specific painting in various colors using dehalogenase-based protein-tag fluorescent ligands.
abstract: In vivo fluorescence cancer imaging is an important tool in understanding tumor growth and therapeutic monitoring and can be performed either with endogenously produced fluorescent proteins or with exogenously introduced fluorescent probes bound to targeting molecules. However, endogenous fluorescence proteins cannot be altered after transfection, thus requiring rederivation of cell lines for each desired color, while exogenously targeted fluorescence probes are limited by the heterogeneous expression of naturally occurring cellular targets. In this study, we adapted the dehalogenase-based protein-Tag (HaloTag) system to in vivo cancer imaging, by introducing highly expressed HaloTag receptors (HaloTagR) in cancer cells coupled with a range of externally injected fluorophore-conjugated dehalogenase-reactive reactive linkers. Tumor nodules arising from a single transfected cell line were stably labeled with fluorescence varying in emission spectra from green to near-infrared. After establishing and validating a SHIN3 cell line stably transfected with HaloTagR (HaloTagR-SHIN3), in vivo spectral fluorescence imaging studies were performed in live animals using a peritoneal dissemination model. The tumor nodules arising from HaloTagR-SHIN3 could be successfully labeled by four different fluorophore-conjugated HaloTag-ligands each emitting light at different wavelengths. These fluorophores could be alternated on serial imaging sessions permitting assessment of interval growth. Fluorescence was retained in histological specimens after fixation. Thus, this tagging system proves versatile both for in vivo and in vitro imaging without requiring modification of the underlying cell line. Thus, this strategy can overcome some of the limitations associated with the use of endogenous fluorescent proteins and exogenous targeted optical agents in current use.
authors.affiliation: Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, NIH, Bldg. 10, Room 1B40, MSC 1088, 10 Center Drive, Bethesda, Maryland 20892-1088, USA.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kosaka
authors.forename: Mikako
authors.initials: M
authors.lastname: Ogawa
authors.forename: Peter L
authors.initials: PL
authors.lastname: Choyke
authors.forename: Natasha
authors.initials: N
authors.lastname: Karassina
authors.forename: Cesear
authors.initials: C
authors.lastname: Corona
authors.forename: Mark
authors.initials: M
authors.lastname: McDougall
authors.forename: David T
authors.initials: DT
authors.lastname: Lynch
authors.forename: Clifford C
authors.initials: CC
authors.lastname: Hoyt
authors.forename: Richard M
authors.initials: RM
authors.lastname: Levenson
authors.forename: Georgyi V
authors.initials: GV
authors.lastname: Los
authors.forename: Hisataka
authors.initials: H
authors.lastname: Kobayashi
mesh_terms: D000818:Animals; D001665:Binding Sites; D045744:Cell Line, Tumor; D003952:Diagnostic Imaging / Q000379:methods*; D004724:Endoscopy; D005260:Female; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000032:analysis*; D015870:Gene Expression; D006801:Humans; D008024:Ligands; D051379:Mice; D010051:Ovarian Neoplasms / Q000175:diagnosis* / Q000473:pathology; D011506:Proteins / Q000032:analysis* / Q000235:genetics*; D014162:Transfection
chemical_list: D005456:Fluorescent Dyes; D008024:Ligands; D011506:Proteins