Figure 2. ERα inhibits breast cancer metastasis in vivo and in vitro.

MCF-7-luc2 (control) or CRISPR/Cas9-mediated ESR1-deleted MCF-7-luc2 cells (Cas9-ERα) were injected via tail veins into nude mice (n=5). (a) Bioluminescence imaging of the control or the Cas9-ERα group at different time points was used to evaluate tumour progression in the lung. The lung metastases were determined using H&E staining. (b) Luciferase counts of the metastasis sites of mice on week 4. MDA-MB-231-luc2 (control) or ERα-overexpressing MDA-MB-231-luc2 (ERα) cells were injected into nude mice to generate xenograft models (n=5). (c) Bioluminescence imaging at different time points was used to evaluate tumour progression. (d) Luciferase counts of the primary tumours of mice at different time points. (e) Representative images of mice on week 4 are shown after shielding the primary tumour. The lymphatic metastases were determined with H&E staining. (f) The lifetimes of mice injected with control or ERα-overexpressing cells. (g) A transwell assay (top) was performed to determine the effect of ERα on cell invasion by gain or loss of ERα in MDA-MB-231 or MCF-7 cells (n=3). The expression of ERα (bottom) in different groups of MDA-MB-231 or MCF-7 cells was detected by western blotting. (h) A transwell assay (top) was performed to determine the effect of fulvestrant on the invasive capability of MCF-7 cells (n=3). The expression of ERα (bottom) in MCF-7 cells that were processed with fulvestrant of different concentrations was detected by western blotting. (i) A transwell assay (top) was performed to determine the invasive capability of parental MCF-7 and MR cells (n=3). The expression of ERα (bottom) was detected by western blotting. (b,d,g–i) Graphs show mean±s.e.m. **P<0.01,***P<0.001. (b,d,g,i) Unpaired t-test; (f) log-rank test; (g,h) analysis of variance (ANOVA) with Dunnett t-test.