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 tetrahydrofuran (THF) was determined to be cytotoxic for three different cell 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 significantly reduced relative to THF-treated cells, and a similar reduction was achieved in HCT-15 cells with use of 5.8 mu M beta-carotene. These concentrations are in the range achieved in serum of individuals supplemented with beta-carotene at 30 mg/day. There was no beta-carotene cytotoxicity in the concentration range that characterizes serum of unsupplemented individuals. Vitamin E at >200 mu M was no cytotoxic and at higher concentrations slightly stimulated proliferation of all three cell lines. Exposure of cells to vitamin E did not diminish the cytotoxicity of beta-carotene, suggesting that the toxic effect of beta-carotene of exposure of cells to beta-carotene. interestingly, beta-carotene cytotoxicity decreased with increasing cell density. This density-dependent toxicity was attributable to a higher beta-carotene concentration per cell for cells plated at lower. densities. Thus toxicity of p-carotene for colon cancer cells is close, time, and cell density dependent and occurs in vitro at concentrations that can be achieved safely in humans.