Diverse carotenoids protect against chemically induced neoplastic transformation

Publisher Website
Google Scholar
Abstract
The ability of diverse carotenoids to inhibit methylchol-anthrene-induced transformation of 10T1/2 cells has been investigated. When delivered using tetrahydrofuran as a novel solvent, all carotenoids were absorbed by cultured cells. When continuously administered to methyicholanthrene-treated cultures 7 days after removal of the carcinogen, cantha xanthin, β-carotene, α-carotene and lycopene inhibited the production of transformed foci in a dose-dependent manner in the above order of potency. This activity was not associated with drug toxicity or antiproliferative effects. Reniera purpurin and bixin did not, inhibit transformation at concentrations ≤10-5 M. Lutein was inhibitory at 10-5 M, but was inactive at lower concentrations. Because of differences in stability in culture medium (α-carotene < β carotene < canthaxanthin < lycopene < lutein) and structure, cellular levels of drug differed up to 8-fold after administration of identical concentrations of compounds. Carotenoids with polar groups achieved highest cellular levels, however cellular uptake did not correlate with activity. For example, lutein, the most polar and most stable, reached the highest concentration in cells yet required a concentration of 10-5 M for activity in the transformation assay, while a- carotene, the least stable and least concentrated by cells, was comparably active at 3 × 10-6 M. α-Tocopherol, a potent lipid-phase antioxidant, was as active as lycopene in the transformation assay but at a 10-fold higher concentration did not approach the activity of β-carotene or canthaxanthin. Because the most potent of the carotenoids tested (I.e. β carotene, α-carotene, canthaxanthin) all have the potential for conversion to retinoids (though this has never been demonstrated In mammals for canthaxanthin), it is suggested that these compounds have two components to their action; one related to their antioxidant properties, the other to their pro-vitamin A activities.

This publication has 0 references indexed in Scilit: