Fig. 1
ERX-11 and palbociclib synergistically reduce the growth of ER+ and endocrine therapy-resistant BCa cells. a Equal numbers of MCF-7 cells were treated with ERX-11 (250 nM), palbociclib (50 nM), or in combination, and clonogenic (survival) assays were performed after 14 days. ZR-75 (b), T-47D (c), MCF-7/LTLT (d), and MCF-7/TamR (e) cells were stimulated with E2 (10−8 M) or androstenedione (10 −8 M) for 7 days in the presence or absence of ERX-11 (0.5 μM), palbociclib (0.5 μM), or in combination, and the cell viability was measured by MTT assay. ZR-75 (f) and MCF-7 (g) cells were stimulated with E2 (10−8 M) for 7 days in the presence or absence of ERX-11 (31 nM), abemaciclib (31 nM), ribociclib (31 nM), or combination, and the cell viability was measured by MTT assay. The combination index (CI) was determined by the Chou-Talalay method, CI < 1 indicates synergism (*p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001)