Quantifying tumor associated macrophages in breast cancer: a comparison of iron and fluorine-based MRI cell tracking.
Tumor associated macrophages (TAMs) are associated with tumor growth and metastasis. MRI can detect TAMs labeled with iron oxide (USPIO) or perfluorocarbon (PFC) agents. This study compared these two cell tracking approaches for imaging TAMs in vivo. 4T1 tumors were imaged with MRI at 4 days or 3 weeks post cell implantation after intravenous (i.v.) administration of either USPIO or PFC. Signal loss was detected within tumors at both time points post USPIO. Images acquired at 4 days demonstrated signal loss encompassing the entire tumor and around the periphery at 3 weeks. Number of black voxels suggested higher numbers of TAMs in the tumor at the later time point. After PFC administration, Fluorine-19 (19F) signal was detected in a similar spatial distribution as signal loss post USPIO.19F signal quantification revealed that the number of19F spins was not significantly different at the two time points, suggesting a similar number of TAMs were present in tumors but accumulated in different regions.19F signal was higher centrally in tumors at 4 days and heterogenous around the periphery at 3 weeks. This study revealed that19F-based cell tracking methods better represent TAM density and provides additional information not achievable with iron-based methods.
Robarts Research Institute, London, Ontario, Canada.|The Department of Medical Biophysics, Western University, London, Ontario, Canada.
Ashley V
AV
Makela
Robarts Research Institute, London, Ontario, Canada.|The Department of Medical Biophysics, Western University, London, Ontario, Canada.
Jeffrey M
JM
Gaudet
Robarts Research Institute, London, Ontario, Canada.|The Department of Medical Biophysics, Western University, London, Ontario, Canada.
Paula J
PJ
Foster
D000818:Animals; D001943:Breast Neoplasms / Q000000981:diagnostic imaging*; D058948:Cell Tracking / Q000379:methods*; D005260:Female; D005290:Ferric Compounds / Q000378:metabolism*; D005466:Fluorocarbons / Q000378:metabolism*; D008264:Macrophages / Q000276:immunology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008807:Mice, Inbred BALB C; D013194:Staining and Labeling / Q000379:methods*
D005290:Ferric Compounds; D005466:Fluorocarbons; C000499:ferric oxide