Beta-carotene is accumulated, metabolized, and possibly converted to retinol in human breast carcinoma cells (MCF-7)

The aims of the present study were to investigate the uptake, accumulation, and metabolism of beta-carotene by the human breast carcinoma cell line MCF-7. Beta-carotene uptake was time- and dose-dependent, and independent of cell polarity. Beta-carotene accumulation in cells was linear as a function of its concentration in medium (1.3-4.1 micromol/L). It was accompanied by increasing amounts of retinol, which accumulated in cells following a sigmoid pattern, and by other four putative metabolites. Beta-apocarotenals, epoxides, endoperoxides, retinal, retinoic acid, and retinyl esters were not detected in cell extracts. Beta-carotene and its metabolites did not induce alterations in cell morphology or subcellular localization of epithelial mucins. Beta-carotene and retinol were released from cells that had previously accumulated beta-carotene, and were further incubated in beta-carotene- and retinol-free medium, but intracellular retinol content remained constant whereas beta-carotene decreased. In conclusion, beta-carotene added to culture medium in physiological concentrations (1-6 micromol/L) is taken up and metabolized in MCF-7 cells, and is possibly converted to retinol.