Fig. 5

RSV potentiates DOX-induced cytotoxicity and apoptosis in MDA-MB-231 breast cancer cells. A The combination index (CI) of RSV and DOX was determined for 48 h on MDA-MB-231 cells by CCK-8 cell viability assay. An isobologram was generated to represent the synergistic/antagonistic effect of each combination. B MDA-MB-231 cells were treated with DOX (0.5 to 25 μM) with or without RSV (25 μM) for 48 h, and cell viability was measured by CCK-8 assay. C MDA-MB-231 cells were treated with a low concentration of DOX (0.5 μM) in combination with increasing concentrations of RSV (25 to 50 μM) for 24 to 72 h, and cell viability was measured by CCK-8 assay. (n = 3 replicates; student-t test; *, p < 0.05; **; error bars represent mean ± SE). MDA-MB-231 cells were treated with DOX (0.5 μM) with or without RSV (50 to 100 μM) for 48 h. D The activity of caspase 3 and PARP cleavage was examined by Immunoblot. β-actin was used as a loading control. E Flow cytometry determined the apoptosis cell population of the sub-G1 phase, and the percentage of sub-G1 cell populations are listed (n = 3 replicates; student-t test; *, p < 0.05; **; error bars represent mean ± SE)