[Boron neutron capture therapy of human gastric cancer by boron-containing immunoliposomes under thermal neutron irradiation].

Boron neutron capture therapy (BNCT) is based on the nuclear reaction yielding high LET Li-7 and alpha particles when boron-10 is irradiated with thermal neutrons. (Et4N)2(10)B10H10 was entrapped in 40 nm liposomes coating the monoclonal antibody, MGb 2, against human gastric cancer. There were 1.4 x 10(4) 10B atoms encapsulated and 20 molecules of MGb 2 incorporated per liposomes ELISA indicated that the immunoreactivity of antibodies on liposomes retained 80%. Preferred binding to human gastric cancer cell line SGC-7901 was observed as many as 15.1 x 10(9) 10B atoms/tumor cell, 38-fold more than that to normal human embryonic lung cell line SL 7. The fluorescent immunoliposome-stained tumor cells showed membrane-fluorescence while SL 7 cells showed no obvious fluorescence. Irradiated with thermal neutrons (0.025 eV, 3.12 x 10(11)n/cm2, gamma-ray 0.84 Gy), 10B-containing immunoliposomes pretreated SGC-7901 cells survived 27%, significantly lower than non-irradiated cells or non-pretreated cells with irradiation (P less than 0.001). The results demonstrated that boron-containing immunoliposomes could bind selectively and deliver sufficient amount of boron-10 to the target tumor cells.