Fig 1: Treatment of CXCR1/2 inhibitor, repertaxin could reduce tamoxifen resistance. (a) The dosage-dependent effect of repertaxin on cell viability of MCF-10A. Non-cancerous breast epithelial cell line MCF-10A was used. The cells were treated with different concentrations of repertaxin for 96 h. MTT assay was performed. Results were shown as mean ± SD from 5 independent experiments. One-way ANOVA was employed. Bonferroni’s multiple comparison test was employed to determine the significance between 0 nM and other concentrations. Repertaxin could reduce tamoxifen resistance in (b) MCF-7-BQ, (c) ZR-75-BQ and (d) LCC2. The cells were co-treated with 4 µM of 4-OHT and 0.1 µM of repertaxin for 14 days. Clonogenic assay was performed. 0.01% crystal violet was used to stain the colonies. Results were shown as mean ± SD from 4 independent experiments. Student’s t-test was employed to determine statistical significance between DMSO and repertaxin treated groups. *** represents p < 0.001. (e) Repertaxin could suppress AKT and ERK1/2 activation on BQ overexpressing cells. MCF-7, MCF-7-BQ, ZR-75 and ZR-75-BQ cells were treated with 0.1 µM of repertaxin for 48 h. Western blot was used to determine the expression of the protein candidates. GAPDH was used as the loading control.