Application of boron-entrapped stealth liposomes to inhibition of growth of tumour cells in the in vivo boron neutron-capture therapy model

Tumour cell destruction in boron neutron-capture therapy (BNCT) is due to the nuclear reaction between 10B and thermal neutrons. It is necessary for effective BNCT therapy to accumulate 10B atoms in the tumour cells. The delivery system consisted of polyethylene-glycol (PEG) binding liposomes (DPPC/cholesterol/DSPC-PEG2000) with an entrapped 10B-compound and we evaluated the cytotoxic effects of intravenously injected 10B-PEG-liposomes on human pancreatic carcinoma xenografts in nude mice with thermal neutron irradiation. After thermal neutron irradiation of mice injected with 10B-PEG-liposomes, growth of AsPC-1 tumours was suppressed relative to controls. Injection of 10B-PEG-liposomes caused the greatest tumour suppression with thermal neutron irradiation in vivo. These results suggest that intravenous injection of 10B-PEG-liposomes can increase the retention of 10B atoms by tumour cells, causing suppression of tumour growth in vivo, after thermal neutron irradiation.