Mutagenic effect of boronophenylalanine and borocaptate in neutron capture therapy

To investigate the mutagenic effect in BNCT, CHO cells were incubated for 2 hours or 20 hours in culture medium with borocaptate sodium (BSH: Na2B12H11SH), or boronophenylalanine (BPA) prior exposure to neutrons from the heavy water facility of the Kyoto University Research Reactor (KUR) and the occurrence of mutations at the HPRT locus was measured. The mutagenicity of BSH and BPA was almost similar to the mutagenicity of 10B-boric acid at the same 10B concentration when cells were irradiated by iso-survival neutron dose. Pre-incubation to BSH for 20 hours caused an increase both in the cell killing effect and mutagenic effect in boron neutron capture therapy (BNCT) compared with pre-incubation to BSH for 2 hours. However, pre-incubation to BPA for 20 hours caused an increase in the cell killing effect but induced a decrease in mutagenic effect in BNCT compared with pre-incubation to BPA for 2 hours. (author)