Figure 3

α-TEA alone and in combination with TAM induces apoptosis in TAMR cell lines. (a) TAM-sensitive MCF-7/parental cells and TAMR MCF-7/TAMR and MCF-7/HER-2 cells were treated with 10, 20, and 40 μM α-TEA for 1 day. Apoptosis was determined with Annexin V/PI. (b) MCF-7/TAMR and MCF-7/HER-2 cells were treated with 10 or 20 or 30 μM α-TEA, 0.5 or 1 or 1.5 μM TAM, and in combination for 1 day. Apoptosis was determined with annexin V/PI/FACS assay. (c) MCF-7/TAMR and MCF-7/HER-2 cells were treated separately and in combination with 20 μM α-TEA and 1 μM TAM for 1 day. Western blot analyses were performed to determine cleaved (c-) forms of caspases-8, 9, and PARP. Data in (a) and (b) are depicted as mean ± SD of three individual experiments. *Significantly different in comparison with TAM and α-TEA alone; P < 0.05. Data in (c) are representative of three individual experiments. α-TEA, RRR-α-tocopherol ether-linked acetic acid analogue; HER-2, epidermal growth-factor receptor-2 ErbB-2; TAM, tamoxifen; TAMR, tamoxifen resistant; MCF-7/HER-2, clone 18 MCF-7 cells overexpressing HER-2; MCF-7/TAMR, acquired tamoxifen-resistant MCF-7.