Fig. 1

SOX9 localised in the nucleus is required for tamoxifen resistance. a Kaplan–Meier plot analysis of the correlation between the expression of SOX9 and survival rates in human breast cancer with public bioinformatics dataset (SOX9 low n = 1977, high n = 1974). b Western blot analysis of SOX9 protein of cytoplasmic and nuclear fractions from MDA-MB-231 and MCF-7 cells. c Comparison of SOX9 mRNA level in human breast cancer according to its sensitivities to tamoxifen by using GSE9195 cohort (ER⁺ breast cancer samples from women treated with adjuvant tamoxifen monotherapy, tamoxifen-sensitive n = 64 and tamoxifen-resistance n = 13). d Kaplan–Meier plot analysis of disease-free survival based on SOX9 mRNA levels by using GSE9195 cohort (ER⁺ breast cancer samples from women treated with adjuvant tamoxifen monotherapy, lower n = 39, higher n = 38). e Representative confocal images of immunofluorescence for SOX9 expression in MCF-7 and TAMR MCF-7 cells. Scale bar, 20 μm. f Western blot analysis for SOX9 protein in parental and TAMR MCF-7 cells. g Western blot for SOX9 protein in control and KO-SOX9 TAMR MCF-7 cells. h MTT assay of the growth rate in control or KO-SOX9 TAMR MCF-7 cells (lower). i Flow cytometric analysis of ALDH⁺ cells with control and SOX9-KO TAMR MCF-7 cells. j qRT-PCR of CD44, ALDH1A1 and SOX2 mRNA in TAMR MCF-7 cells with control or SOX9-KO. k Western blot analysis for CD44, ALDH1A1 and SOX2 proteins in TAMR MCF-7 cells with control or KO-SOX9. l MTT assay of growth rate after tamoxifen (1 μM) treatment in MCF-7 cells with SOX9 overexpression or vector control. m Western blot analysis for ERα C-MYC ABCG2 p21 and Bcl2 proteins in TAMR MCF-7 cells with control or KO-SOX9. n Western blot analysis of tamoxifen-resistance related signalling pathways in MCF-7 cells with control and SOX9-KO. Data are representative of means ± SEM of three independent experiments (unpaired t-test, *p < 0.05, **p < 0.01)