Biodistribution and γ imaging of 125I-labeled goat anti-human IgG polyclonal antibody in nude mice bearing human colon cancer xenografts

The possibility of IgG secreted from tumor cells as a target for radioimmunoimaging and targeted therapy of cancers were investigated. Goat anti-human IgG polyclonal anti- body (GAHG) was radioiodinated using Iodogen method, and the in vitro stability and pharmacokinetics were evaluated. The biodistribution and γ imaging of 125I-GAHG were performed in nude mice bearing HT-29 human colon cancer xenografts. 125I-GAHG showed good in vitro stability, and its blood clearance was defined as a two-compartment model, with T1/2α and T1/2β were 1.19 h and 43.99 h, respectively. The tumor uptake of 125I-GAHG was higher than that of 125I-labeled normal goat IgG control (125I-GIgG). 125I-GAHG showed good tumor retention when injecting via intra-tumor. In the biodistribution study, the highest tumor uptake of 125I-GAHG was 6.71±2.19%ID/g at 72 h postinjection and the T/NT increased along with the postinjection time. The results show that 125I-GAHG have good tumor-specific uptake which may provide a novel idea for radioimmunoimaging and targeted therapy of cancers. (authors)