The selective cytotoxic effect of carotenoids and α-Tocopherol on human cancer cell lines in vitro

Abstract

This study compares the toxic effects of the carotenoids, β-carotene and canthaxanthin, and α-tocopherol (vitamin E) on human tumor cells and their normal counterparts in vitro. Seven different malignant cell lines were examined: oral carcinoma (two cell lines), breast (two cell lines), lung carcinoma (two cell lines), and malignant melanoma. The in vitro cell culture assays showed a consistent morphologic change in the affected tumor cells following treatment with carotenoid or vitamin E. A rounding of the tumor cells and eventual lifting off the tissue culture plate were observed. These changes were apparent after 1 to 5 hours of treatment depending on the tumor cell line. Associated with these observable cellular changes were quantitative reductions in proliferation ( 3H-thymidine proliferation) and succinic dehydrogenase activity (MTT assay). In addition, there was a noticeable change in protein expression, with an increased expression of a 70-kD protein following treatment with β-carotene. This protein was associated with tumor cells showing a decrease in proliferation (oral carcinoma, malignant melanoma), but not with normal keratinocytes or melanocytes. These studies substantiate a selective cytotoxic effect on human tumor cell growth by carotenoids and α-tocopherol in vitro, and may provide an explanation of the therapeutic activity of these agents and their possible use in the treatment of premalignancy or early oral carcinoma.