A HUMAN NEUROBLASTOMA XENOGRAFT MODEL FOR 125-I-METAIODOBENZYLGUANIDINE BIODISTRIBUTION STUDIES

We developed an animal model to evaluate the 125-I-metaiodobenzylguani dine (125-I-mIBG) biodistribution in tumor bearing mice. Six weeks old nude-atimic mice were subcutaneously injected with 30 x 10(6) cells o f the human neuroblastoma (NB) cell line SH-SY5Y. TE-671, a rhabdomyos arcoma cell line, was used as a control tumor without a specific mIBG uptake mechanism. In order to prevent possible tumor rejection mediate d by NK activity the anti asialo GM1 antiserum was administered intrap eritoneally once a week for 4 weeks. The maximum anti asialo mediated effect was obtained by administering the first dose the same day as th e cell implant. In this group of animals by 9 weeks 98% of mice had a measurable tumor. We have utilized this model to evaluate the biodistr ibution of 125-I-mIBG given as two different formulations: standard pr eparation with a specific activity of 84 mCi/mg and the no carrier add ed (n.c.a.) formulation with a specific activity of approximatelly 8,0 00 mCi/mg. Our preliminary results indicate that the biodistribution o f the two different formulations in the various organs are similar. Th erefore it appears that n.c.a. mIBG should not cause an increased toxi city in possible normal target organs such as heart or adrenals. Addit ional experiments will be performed in this model to ascertain if ther e is a potential advantage of the clinical use of n.c.a. mIBG over the standard preparation.