PDF file - 622K, BT474/MUC1shRNA (A) and MCF-7/vector (B) cells were treated with fixed IC50 ratios of (i) GO-203 alone on days 0, 1, 2, 3 and 4, (ii) tamoxifen alone on days 0, 2 and 4 and (iii) the GO-203/tamoxifen combination. For tamoxifen-resistant BT-474/CshRNA and MCF-7/MUC1-C cells, tamoxifen was used at the half-maximal inhibitory concentrations obtained for the tamoxifen-sensitive BT-474/MUC1shRNA and MCF-7/vector cells, respectively. The multiple effect-level isobologram analyses are shown for the ED50 (X), ED75 (+) and ED90 (⊗) values.