α-Tocopheryl succinate induces cytostasis and apoptosis in osteosarcoma cells: the role of E2F1

α-Tocopheryl succinate (α-TOS), a redox-inactive analog of vitamin E, induces cell cycle arrest, differentiation, and triggers apoptosis. We examined the ability of α-TOS to induce cytostasis and/or apoptosis in two human osteosarcoma cell lines, which carry wild-type pRb but differ in the p53 status. In the wt-p53 cells, α-TOS induced apoptosis, which was associated with p53 activation and enhanced E2F1 expression. Mutant p53 cells failed to undergo apoptosis when challenged with α-TOS. The cell growth arrest after α-TOS treatment was associated with a reduced expression of E2F1. Knocking down E2F1 rendered the α-TOS-sensitive cells rather resistant to the apoptotic stimulus inducing a marked and prolonged cell growth arrest. We conclude that α-TOS induces cell growth arrest or apoptosis involving E2F1.