Evaluation of Boron Neutron Capture Therapy for treating canine oral malignant melanoma

Boron neutron capture therapy (BNCT) is a particle therapy that selectively kills cancer cells by using the boron neutron capture reaction (BNCR). The average life expectancy of companion animals, such as dogs and cats, is increasing. In this study, we used metastatic lymph node with the primary site of the oral mucosa (LMeC), a type of canine melanoma cell line, to investigate the applicability of BNCT to canine melanoma. We treated LMeC cells with L-BPA (BPA), incubated them for 3 h, and then analyzed the intracellular boron concentration. LMeC took up boron and the boron concetration reached the same level as the added concentration. BPA-containing LMeC cells were irradiated with thermal neutron beam at the Kyoto University Research Reactor, and the cell-survival fraction and DNA damage were compared with the gamma-ray irradiation results. The survival curves for the neutron-irradiated BPA+ were linear as were those for high-linear energy transfer radiation. In the linear-quadratic model, the survival fraction at an absorbed dose of approximately 3 Gy was approximately 25 % lower in the neutron irradiated BPA+ than in the gamma-ray-irradiated cells. The number of foci indicating DNA damage was significantly increased after neutron irradiation to BPA+ than after gamma-ray irradiation. These results indicated that LMeC cells take up sufficient boron and undergo efficient cell death by (n,α) with thermal reactions.