Radiobiological response of U251MG, CHO-K1 and V79 cell lines to accelerator-based boron neutron capture therapy

In the current article, we provide in vitro efficacy evaluation of a unique accelerator-based neutron source, constructed at the Budker Institute of Nuclear Physics (Novosibirsk, Russian Federation), for boron neutron capture therapy (BNCT), which is particularly effective in the case of invasive cancers. U251MG, CHO-K1 and V79 cells were incubated and irradiated in various concentrations of boric acid with epithermal neutrons for 2-3 h in a plexiglass phantom, using 2.0 MeV proton energy and 1.5-3.0 mA proton current, resulting in a neutron fluence of 2.16 x 10(12) cm(-2). The survival curves of cells loaded with boron were normalized to those irradiated without boron (to exclude the influence of the fast neutron and gamma dose components) and fit to the linear-quadratic (LQ) model. Colony formation assays showed the following cell survival rates (means +/- SDs): CHO-K1: 0.348 +/- 0.069 (10 ppm), 0.058 +/- 0.017 (20 ppm), 0.018 +/- 0.005 (40 ppm); V79: 0.476 +/- 0.160 (10 ppm), 0.346 +/- 0.053 (20 ppm), 0.078 +/- 0.015 (40 ppm); and U251MG: 0.311 +/- 0.061 (10 ppm), 0.131 +/- 0.022 (20 ppm), 0.020 +/- 0.010 (40 ppm). The difference between treated cells and controls was significant in all cases (P < 0.01) and confirmed that the neutron source and irradiation regimen were sufficient for control over cell colony formation. We believe our study will serve as a model for ongoing in vitro experiments on neutron capture therapy to advance in this area for further development of accelerator-based BNCT into the clinical phase.