Lithium salts cytotoxicity and accumulation in melanoma cells in vitro

Boron neutron capture therapy is a perspective selective technology for the destruction of cancer cells, while the use of lithium instead of boron may represent a new and promising vector for the development of neutron capture therapy (NCT). The aim of the study was a comparative assessment of the cytotoxicity of various lithium salts, as well as an analysis of the accumulation of lithium in tumor cells in vitro to determine the possibility of using lithium in NCT. The cytotoxicity of lithium salts was determined using MTT-test and colony forming assay on human fibroblasts BJ-5ta, human skin melanoma SK-Mel-28, and mouse skin melanoma B16 cell lines. An assessment of lithium concentration in cells was performed using inductively coupled plasma atomic emission spectrometry. Our results showed that three different lithium salts at a concentration of 40 μg/ml are not toxic for both tumor and normal cells. The highest uptake values were obtained on murine melanoma B16 cells when exposed to lithium carbonate (0.8 μg/10⁶ cells); however, human melanoma SK-Mel-28 cells effectively accumulated both lithium carbonate and lithium citrate (about 0.46 μg/10⁶ cells for two salts). Thus, our results demonstrate a range of non-toxic doses of lithium salts and a high uptake of lithium by tumor cells, which indicates the possibility to use the lithium in NCT.