Imaging of Vx-2 rabbit tumors with αvβ3-integrin-targeted 111In nanoparticles

Earlier tumor detection can improve 5-year survival of patients, particularly among those presenting with cancers less than I cm in diameter. alpha(v)beta(3)-Targeted In-111 nanoparticles (NP) were developed and studied for detection of tumor angiogenesis. Studies were conducted in New Zealand white rabbits implanted 12 days earlier with Vx-2 tumor. alpha(v)beta(3)-Targeted In-111/NP bearing similar to 10. In-111/NP vs. similar to 1 In-111/NP nuclide payloads were compared to nontargeted radiolabeled control particles. In vivo competitive binding studies were used to assess ligand-targeting specificity. alpha(v)beta(3)-Integrin-targeted NP with similar to 10 In-111/NP provided better (p < 0.05) tumor-to-muscle ratio contrast (6.3 +/- 0.2) than similar to 1 In-111/NP (5.1 +/- 0.1) or nontargeted particles with similar to 10 In-111/NP (3.7 +/- 0.1) over the initial 2-hr postinjection. At 18 hr, mean tumor activity in rabbits receiving alpha(v)beta(3)-integrin-targeted NP was 4-fold higher than the nontargeted control. Specificity of the NP for the tumor neovasculature was supported by in vivo competition studies and by fluorescence microscopy of alpha(v)beta(3)-targeted fluorescent-labeled NP. Biodistribution studies revealed that the primary clearance organ in rabbits as a %ID/g tissue was the spleen. Circulatory half-life (t(1/2 beta)) was estimated to be similar to 5 hr using a 2-compartment model. alpha(v)beta(3)-Targeted In-111 perfluorocarbon NP may provide a clinically useful tool for sensitively detecting angiogenesis in nascent tumors, particularly in combination with secondary high-resolution imaging modalities, such as MRI. (c) 2007 Wiley-Liss, Inc.