(A) S100A8 plasmid is constructed and tested by Western blotting. (B) Knockdown of S100A8 in MCF7 cells and tested by Western Blot. (C) MCF7 cells were transfected SiNC, SiHRD1, SiS100A8 and co-transfected SiHRD1 and SiS100A8 respectively, followed by treatment of 5 μM Tamoxifen. After 48 h, SRB assay played. (D) MCF7/Tam cells were transfected Vector, HRD1, S100A8 and co-transfected HRD1 and S100A8 respectively, followed by treatment of 10 μmol/l Tamoxifen. After 48 h, SRB assay played. (E) MCF7 cells were transfected SiNC and SiHRD1 respectively for 24 h followed by treatment of 5 μmol/l Tamoxifen. After 48 h, the flow cytometry played. (F) MCF7/Tam cells were transfected Vector and HRD1 plasmid respectively for 24 h followed by treatment of 10 μmol/l Tamoxifen. After 48 h, the flow cytometry was performed. All graphs show means ± S.D. of three independent experiments. **P < 0.05, compare to Si-NC or vector; #P < 0.05, compare to Si-NC or vector + Tamoxifen; &P < 0.05, compare to Si-HRD1 or HRD1 + Tamoxifen.