IN-VITRO BETA-CAROTENE TOXICITY FOR HUMAN COLON-CANCER CELLS

Experiments were conducted to determine the effect of beta-carotene on human colon cancer cells in vitro. beta-Carotene solubilized in tetra hydrofuran (THF) was determined to be cytotoxic for three different ce ll lines: LS 180, SW 620, and HCT-15. The number of LS 180 and SW 620 cells surviving treatment with 2.9 mu M beta-carotene was significantl y reduced relative to THF-treated cells, and a similar reduction was a chieved in HCT-15 cells with use of 5.8 mu M beta-carotene. These conc entrations are in the range achieved in serum of individuals supplemen ted with beta-carotene at 30 mg/day. There was no beta-carotene cytoto xicity in the concentration range that characterizes serum of unsupple mented individuals. Vitamin E at >200 mu M was no cytotoxic and at hig her concentrations slightly stimulated proliferation of all three cell lines. Exposure of cells to vitamin E did not diminish the cytotoxici ty of beta-carotene, suggesting that the toxic effect of beta-carotene of exposure of cells to beta-carotene. interestingly, beta-carotene c ytotoxicity decreased with increasing cell density. This density-depen dent toxicity was attributable to a higher beta-carotene concentration per cell for cells plated at lower. densities. Thus toxicity of p-car otene for colon cancer cells is close, time, and cell density dependen t and occurs in vitro at concentrations that can be achieved safely in humans.