Downregulation of Epidermal Growth Factor Receptor Expression Contributes to α-TEA's Proapoptotic Effects in Human Ovarian Cancer Cell Lines

RRR-alpha-tocopherol derivative alpha-TEA (RRR-alpha-tocopherol ether-linked acetic acid analog) has been shown to be a potent antitumor agent both in vivo and in vitro. In this study, we investigated the effects of alpha-TEA on the expression of epidermal growth factor receptor (EGFR) family members, ErbB1, 2 and 3, and the role of ErbB 2 and 3 in alpha-TEA-induced apoptosis and suppression of Akt, FLIP and survivin in the cisplatin-sensitive (A2780S) and -resistant (A2780/CP70R) human ovarian cancer cell lines. Data show that alpha-TEA's ability to induced apoptosis was associated with reduced expression of ErbB1 (cisplatin-resistant cells), 2 and 3 (both cell types) and reduced levels of the phosphorylated (active) form of Akt; as well as, reduced levels of FLIP and survivin proteins in both cell types. Ectopic overexpression and siRNA knockdown studies showed that ErbB2, ErbB3, Akt, FLIP and survivin are involved in alpha-TEA-induce apoptosis and that alpha-TEA downregulates FLIP and survivin via suppression of pAkt, which is mediated by ErbB2 and ErB3. Thus, alpha-TEA is a potent pro-apoptotic agent for both cisplatin-sensitive and -resistant ovarian cancer cell lines in cell culture and it produces cell death, at least in part, by downregulation of members of the EGFR family.