title: In vivo visualization and ex vivo quantification of murine breast cancer cells in the mouse brain using MRI cell tracking and electron paramagnetic resonance.
abstract: Cell tracking could be useful to elucidate fundamental processes of cancer biology such as metastasis. The aim of this study was to visualize, using MRI, and to quantify, using electron paramagnetic resonance (EPR), the entrapment of murine breast cancer cells labeled with superparamagnetic iron oxide particles (SPIOs) in the mouse brain after intracardiac injection. For this purpose, luciferase-expressing murine 4 T1-luc breast cancer cells were labeled with fluorescent Molday ION Rhodamine B SPIOs. Following intracardiac injection, SPIO-labeled 4 T1-luc cells were imaged using multiple gradient-echo sequences. Ex vivo iron oxide quantification in the mouse brain was performed using EPR (9 GHz). The long-term fate of 4 T1-luc cells after injection was characterized using bioluminescence imaging (BLI), brain MRI and immunofluorescence. We observed hypointense spots due to SPIO-labeled cells in the mouse brain 4 h after injection on T2 *-weighted images. Histology studies showed that SPIO-labeled cancer cells were localized within blood vessels shortly after delivery. Ex vivo quantification of SPIOs showed that less than 1% of the injected cells were taken up by the mouse brain after injection. MRI experiments did not reveal the development of macrometastases in the mouse brain several days after injection, but immunofluorescence studies demonstrated that these cells found in the brain established micrometastases. Concerning the metastatic patterns of 4 T1-luc cells, an EPR biodistribution study demonstrated that SPIO-labeled 4 T1-luc cells were also entrapped in the lungs of mice after intracardiac injection. BLI performed 6 days after injection of 4 T1-luc cells showed that this cell line formed macrometastases in the lungs and in the bones. Conclusively, EPR and MRI were found to be complementary for cell tracking applications. MRI cell tracking at 11.7 T allowed sensitive detection of isolated SPIO-labeled cells in the mouse brain, whereas EPR allowed the assessment of the number of SPIO-labeled cells in organs shortly after injection.
authors.affiliation: Louvain Drug Research Institute, Biomedical Magnetic Resonance Research Group, Université catholique de Louvain, Brussels, Belgium.
authors.forename: Pierre
authors.initials: P
authors.lastname: Danhier
authors.forename: Julie
authors.initials: J
authors.lastname: Magat
authors.forename: Philippe
authors.initials: P
authors.lastname: Levêque
authors.forename: Géraldine
authors.initials: G
authors.lastname: De Preter
authors.forename: Paolo E
authors.initials: PE
authors.lastname: Porporato
authors.forename: Caroline
authors.initials: C
authors.lastname: Bouzin
authors.forename: Bénédicte F
authors.initials: BF
authors.lastname: Jordan
authors.forename: Gladys
authors.initials: G
authors.lastname: Demeur
authors.forename: Vincent
authors.initials: V
authors.lastname: Haufroid
authors.forename: Olivier
authors.initials: O
authors.lastname: Feron
authors.forename: Pierre
authors.initials: P
authors.lastname: Sonveaux
authors.forename: Bernard
authors.initials: B
authors.lastname: Gallez
mesh_terms: D000818:Animals; D001921:Brain / Q000473:pathology*; D045744:Cell Line, Tumor; D058948:Cell Tracking / Q000379:methods*; D003911:Dextrans / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005260:Female; D007267:Injections; D008163:Luminescent Measurements; D008168:Lung / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D015674:Mammary Neoplasms, Animal / Q000473:pathology*; D008807:Mice, Inbred BALB C; D009206:Myocardium / Q000378:metabolism; D009928:Organ Specificity; D012235:Rhodamines / Q000378:metabolism; D013194:Staining and Labeling; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D003911:Dextrans; D058185:Magnetite Nanoparticles; D012235:Rhodamines; C065507:ferumoxides; C029773:rhodamine B
keywords: MRI; cancer; cell tracking; electron paramagnetic resonance; iron oxide particles; metastasis