Combination of SEL with TAM inhibits growth of metastatic ER+ tumors in vivo. (A) SEL combination with TAM provides sustained tumor regression of MCF7-ESR1Y537S xenografts. A two-way ANOVA model was fitted to assess the time dependent contribution of ligand Vehicle (Veh), TAM) and inhibitor (Ctrl, 5 mg/kg SEL or 10 mg/kg SEL) treatment on tumor volume. When the main effects were statistically significant at p < 0.05, pairwise t-tests with a Bonferroni correction were employed to identify if treatment were statistically different from each other. * p < 0.05, ** p < 0.01, *** p <0.001, **** p < 0.0001. (B) Percentage body weight change of mice. (C) Histological analysis of tumors from (A). HE, ERα and XPO1 IHC stainings were performed. (D) Treatment with Fulv or Palb alone or in combination with SEL did not result in MCF7 ESR1Y537S tumor regression. (E) Comparison of percent tumor volume change compared to start day of treatments in experiments from (A).