Evaluation of the genotoxic effects of the boron neutron capture reaction in human melanoma cells using the cytokinesis block micronucleus assay

The present work reports on the genotoxicity of the boron neutron capture ( BNC) reaction in human metastatic melanoma cells (A2058) assessed by the cy tokinesis block micronucleus assay (CBMN) using p-borono-L-phenylalanine (B PA) as the boron delivery agent. Different concentrations of BPA (0.48, 1.2 and 2.4 mM) and different fluences of thermal neutrons were studied. Subst antial genotoxic potential of alpha and lithium particles generated inside or near the malignant cell by the BNC reaction was observed in a dose-respo nse manner as measured by the frequency of micronucleated binucleated melan oma cells and by the number of micronuclei (MN) per binucleated cell. The d istribution of the number of MN per micronucleated binucleated cell was als o studied. The BNC reaction clearly modifies this distribution, increasing the frequency of micronucleated cells with 2 and, especially, less than or equal to3 MN and conversely decreasing the frequency of micronucleated cell s with 1 MN. A decrease in cell proliferation was also observed which corre lated with MN formation. A discrete genotoxic and anti-proliferative contri bution from both thermal neutron irradiation and BPA was observed and shoul d be considered secondary. Additionally, V79 Chinese hamster cells (chromos omal aberrations assay) and human lymphocytes (CBMN assay) incubated with d ifferent concentrations of BPA alone did not show any evidence of genotoxic ity. The presented results reinforce the usefulness of the CBMN assay as an alternative method for assessment of the deleterious effects induced by hi gh LET radiation produced by the BNC reaction in human melanoma cells.