Application of 10BSH entrapped transferrin-PEG-liposome to boron neutron-capture therapy (BNCT) for solid tumor

The successful treatment of cancer by BNCT requires the selective concentration of 10B within malignant tumor cells. Intracellular targeting ability and cytotoxic effects of 10B entrapped TF-PEG-liposomes, in which TF is covalently linked to the distal terminal of PEG chains on the external surface of PEG-liposomes, were examined in Colon 26 tumor-bearing mice. TF-PEG-liposomes readily bound to tumor cells in vivo, and were internalized by receptor-mediated endocytosis. 10B-PEG-liposomes and 10B-TF-PEG-liposomes showed prolonged residence time in the circulation and low RES uptake in tumor-bearing mice, resulting in enhanced extravasation of the liposomes into the solid tumor tissue and reached high level of 10B content in tumor. After thermal neutron irradiation of mice injected with 10B-PEG-liposomes or 10B-TF-PEG-liposome, tumor growth was suppressed relative to controls. These results suggest that intravenous injection of 10B TF-PEG-liposome can increase the intracellular retention of 10B atoms, which were introduced by receptor mediated endocytosis after binding, causing tumor growth suppression in vivo upon thermal neutron irradiation. (author)