THE DEMONSTRATION OF HUMAN TUMORS ON NUDE-MICE USING GADOLINIUM-LABELED MONOCLONAL-ANTIBODIES FOR MAGNETIC-RESONANCE-IMAGING

RATIONAL AND OBJECTIVES. The authors describe the magnetic resonance imaging (MRI) of a tumor in a nude mouse tumor model by means of an antibody-polylysine (Gd-DTPA) conjugate. METHODS. The monoclonal antibody, (MAB) RA96, was coupled to a polymeric gadolinium complex after periodate oxidation. This polymer, which consists of a polylysine backbone and complexing DTPA subunits, complexes an average of 65 gadolinium ions. RESULTS. The immunoreactivity of the conjugates was reduced by an average of only 30% compared with the unbound MAB RA96. Biodistribution studies in nude mice with subcutaneously implanted human colon carcinomas (WiDr [specific] and HT29 [control]) revealed a tissue concentration in the specific tumor of 8.72% of the dose applied per gram despite the high molecular weight of the conjugates. CONCLUSIONS. This tissue concentration is sufficient to achieve tumor-specific signal enhancement in the WiDr tumor on MRI. The problem of the high doses of protein required for MRI and possible solutions are discussed.