Fig. 6. Cell viability and isobologram analysis of MCF-7 breast cancer cells treated with combinations of endoxifen and other compounds. Cell viability was analyzed using the EZ-Cytox assay. Isobologram analysis was performed using the CompuSyn program. The MCF-7 breast cancer cell line showed an antagonistic effect toward endoxifen with chrysophanol or rhein. CI, combination index. ^*P < 0.05, ^**P < 0.01.