Magnetic resonance imaging of nude mice with heterotransplanted high-grade squamous cell carcinomas - Use of a low-loaded, covalently bound Gd-Hsa conjugate as contrast agent with high tumor affinity

RATIONALE. Malignant tumors often show an increased uptake and metabolism of plasma proteins, especially albumin. OBJECTIVES.Determine whether the accumulation of low loaded Gd-albumin improves visualization of malignant tumors by MRI. METHODS. Twelve nude mice with heterotransplanted squamous cell carcinomas were studied. The signal intensity of tumor, blood, liver, kidney and muscle tissue was studied in MR images after application of Gd-albumin during a period of 144 hours. MRI results were histologically correlated after simultaneously injection of Gd- and fluorescein-labeled albumins In 9 nude mice. RESULTS. Although liver and kidney had a maximum increase In signal intensity within 30 minutes, tumors showed a delayed 51% increase in the 24 hours after application. Histologic and fluorescence evaluation demonstrated albumin localization in tumors predominantly in stroma and necroses. CONCLUSIONS. Gd-albumin is efficiently accumulated in SCC transplants. MRI with low loaded Gd-albumin may offer relevant opportunities for recognizing tumors sensitive to a therapy with cyostic drug-labeled albumins.