Biodistribution of 177Lu-octreotate and 111In-minigastrin in female nude mice transplanted with human medullary thyroid carcinoma GOT2

To be able to evaluate new radiopharmaceuticals and optimize diagnosticand therapeutic procedures, relevant animal models are required. The aim of thisstudy was to evaluate the medullary thyroid carcinoma GOT2 animal model by analyzingthe biodistribution of 177Lu-octreotate and 111In-minigastrin (MG0). BALB/c nudemice, subcutaneously transplanted with GOT2, were intravenously injected witheither 177Lu-octreotate or 111In-MG0, with or without excess of unlabeled humanminigastrin simultaneously with 111In-MG0. Animals were sacrificed 1-7 days afterinjection in the 177Lu-octreotate study and 1 h after injection of 111In-MG0.The activity concentrations in organs and tissues were determined and mean absorbeddoses from 177Lu were calculated. There was a specific tumor uptake of either177Lu-octreotate or 111In-MG0. 177Lu-octreotate samples showed high activity concentrationsin tissues expressing somatostatin receptors (SSTR). For both radiopharmaceuticalsthe highest activity concentrations were found in the kidneys. Compared to resultsfrom similar studies in mice with another MTC cell line (TT) the biodistributionwas favorable (higher tumor uptake) for the GOT2 model, while compared to otheranimal models expressing SSTR, the tumor uptake of 177Lu-octreotate was modest.In conclusion, the GOT2 animal model is a valuable model for evaluation and optimizationof diagnostic and therapeutic procedures using radiolabeled somatostatin, CCK2and gastrin analogues prior to clinical studies.