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 microM 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 microM 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 microM was not 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 is not due to prooxidant activity. Percent cytotoxicity was increased by extending the duration 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 beta-carotene for colon cancer cells is dose, time, and cell density dependent and occurs in vitro at concentrations that can be achieved safely in humans.
Iftikhar
S
S
Department of Medicine, Columbus Cabrini Hospital, Chicago, IL 60614, USA.
Lietz
H
H
Mobarhan
S
S
Frommel
T O
TO
D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D002851:Chromatography, High Pressure Liquid; D003110:Colonic Neoplasms / Q000473:pathology*; D005663:Furans; D006801:Humans; D012995:Solubility; D014407:Tumor Cells, Cultured; D014810:Vitamin E / Q000008:administration & dosage / Q000494:pharmacology; D019207:beta Carotene / Q000008:administration & dosage / Q000494:pharmacology*
D005663:Furans; D019207:beta Carotene; D014810:Vitamin E; C018674:tetrahydrofuran