β-carotene at high concentrations induces apoptosis by enhancing oxy-radical production in human adenocarcinoma cells

This is the first report demonstrating a relationship between apoptosis induction and changes of intracellular redox potential in the growth-inhibitory effects of high concentrations of beta -carotene in a tumor cell line. beta -Carotene inhibited the growth of human WiDr colon adenocarcinoma cells in a dose- and time-dependent manner, induced apoptosis, and blocked Bcl-2 expression. These effects were accompanied by an enhanced production of intracellular reactive oxygen species (ROS). The addition of the antioxidant alpha -tocopherol blocked both the pro-oxidant and the growth-inhibitory effects of the carotenoid. These findings suggest that beta -carotene may act as an inductor of apoptosis by its pro-oxidant properties. (C) 2001 Elsevier Science Inc.