The anticlastogenicity of beta-carotene evaluated on human hepatoma cells

The efficiency of beta-carotene as a modulatory agent against clastogenicity induced by cyclophosphamide (CPA), an indirect-acting mutagen, and mitomycin C (MMC), a direct-acting mutagen, was evaluated in human hepatoma cells (Hep G2) using three different treatment regimes. Six doses of beta-carotene, 0.25, 0.5, 1.0, 2.0, 4.0 and 6.0 microM, were tested as pre-treatment, simultaneous treatment and pre- + simultaneous treatment. Since these cells are able to activate mutagens without any exogenous metabolizing system (S9 mix), some problems related to the use of S9 mix were eliminated. The data obtained show a statistically significant decrease in the frequency of micronuclei (MN) induced by CPA when the cells were treated with beta-carotene, for all treatments, and no effect of this provitamin on the clastogenicity of MMC was found. These results reinforce the anticlastogenicity of beta-carotene showing that its action is independent of the treatment regime used. On the other hand, the fact that beta-carotene had a protective action only on CPA-induced MN suggests an effect on activation of the promutagen and emphasizes the important utility of cell lines capable of metabolizing chemical mutagens, in such basic studies.