Figure 1.

Establishment of 4-OHT resistant BC cell lines. (A) the IC₅₀ values of 4-OHT on MCF-7/4-OHT or T47D/4-OHT cells examined by CCK-8 assays; (B) the apoptosis levels of MCF-7 and T47D cells detected by flow cytometry after 4 μM and 8 μM 4-OHT, respectively; (C) the apoptosis levels of BC cells assessed by Caspase-3 activity kit; (D) the cytotoxicity of 4-OHT to BC cells determined by a LDH kit; (E) colony formation of BC cells tested by colony formation assays; (F) number of S-phase cells detected by EdU assays. Data are displayed in the form of mean ± SD. All experiments were repeated three times. In panel (A) two-way ANOVA along with Tukey’s multiple comparison was applied, while in panel (B–F) one-way ANOVA along with Tukey’s multiple comparison was used. *p < 0.05, **p < 0.01.

Abbreviations: BC, breast cancer; 4-OHT, 4-hydroxytamoxifen; CCK-8, cell counting kit-8; LDH, lactose dehydrogenase; EdU, 5-ethynyl-2ʹ-deoxyuridine; SD, standard deviation; ANOVA, analysis of variance.