|  | α-TEA:TAM | CIc |  |  |
|---|
| Â | Ratiob | ED50 | ED75 | ED90 | Mean + SDd | Â |
MCF-7/TAMR | 20:1 | 0.59 | 0.59 | 0.59 | 0.59 ± 0.00 | Synergisma |
MCF-7/HER-2 | 20:1 | 0.68 | 0.80 | 0.94 | 0.81 ± 0.13 | Synergisma |
- aMCF-7/TAMR and MCF-7/HER-2 human breast cancer cells were treated with different concentrations of α-TEA and TAM alone and in combinations for 24 hours. Apoptosis was determined as described in Material and Methods. bThe ratio for concentrations used in combination treatments were determined from data in Figure 3b and c. cFor each combination treatment, a combination index (CI) was calculated by using methods as described previously and by using the commercially available software (CalcuSyn; Biosoft, Manchester, United Kingdom). dThe mean ± standard deviation (SD) is calculated from the CI values of effective dosages (EDs) that produced 50%, 75%, and 90% apoptosis. eCI values <1.0 indicate synergism; CI values of 1.0 indicate additive effect; and CI values >1.0 indicate antagonism. α-TEA, RRR-α-tocopherol ether-linked acetic acid analogue; MCF-7/HER-2, clone 18 MCF-7 cells overexpressing HER-2; MCF-7/TAMR, acquired tamoxifen-resistant MCF-7; mER, membrane estrogen receptor; TAM, tamoxifen.
