Magnetic resonance imaging at 1.5 T with immunospecific contrast agent in vitro and in vivo in a xenotransplant model.
OBJECTIVE
Demonstrating the feasibility of magnetic resonance imaging (MRI) at 1.5 T of ultrasmall particle iron oxide (USPIO)-antibody bound to tumor cells in vitro and in a murine xenotransplant model.


METHODS
Human D430B cells or Raji Burkitt lymphoma cells were incubated in vitro with different amounts of commercially available USPIO-anti-CD20 antibodies and cell pellets were stratified in a test tube. For in vivo studies, D430B cells and Raji lymphoma cells were inoculated subcutaneously in immunodeficient mice. MRI at 1.5 T was performed with T1-weighted three-dimensional fast field echo sequences (17/4.6/13 degrees ) and T2-weighted three-dimensional fast-field echo sequences (50/12/7 degrees ). For in vivo studies MRI was performed before and 24 h after USPIO-anti-CD20 administration.


RESULTS
USPIO-anti-CD20-treated D430B cells, showed a dose-dependent decrease in signal intensity (SI) on T2*-weighted images and SI enhancement on T1-weighted images in vitro. Raji cells showed lower SI changes, in accordance to the fivefold lower expression of CD20 on Raji with respect to D430B cells. In vivo 24 h after USPIO-anti-CD20 administration, both tumors showed an inhomogeneous decrease of SI on T2*-weighted images and SI enhancement on T1-weighted images.


CONCLUSIONS
MRI at 1.5 T is able to detect USPIO-antibody conjugates targeting a tumor-associated antigen in vitro and in vivo.
Baio
G
G
DICMI Radiologia, University of Genova, Largo Rosanna Benzi 8, 16100, Genoa, Italy.
Fabbi
M
M
de Totero
D
D
Ferrini
S
S
Cilli
M
M
Derchi
L E
LE
Neumaier
C E
CE
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000276:immunology; D045744:Cell Line, Tumor; D003287:Contrast Media; D003911:Dextrans; D004195:Disease Models, Animal; D016503:Drug Delivery Systems / Q000379:methods; D052203:Ferrosoferric Oxide; D007089:Image Enhancement / Q000379:methods*; D007501:Iron; D008223:Lymphoma / Q000276:immunology / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D058185:Magnetite Nanoparticles; D051379:Mice; D010087:Oxides; D000069283:Rituximab; D014183:Transplantation, Heterologous
D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010087:Oxides; C097921:ferumoxtran-10; D000069283:Rituximab; D007501:Iron; D052203:Ferrosoferric Oxide