Fig. 7. Cell viability and isobologram analysis with drug combination between endoxifen and other compounds in ZR75-1 breast cancer cell line Cell viability analyzed by EZ-Cytox assay. Isobologram analysis was used to Compusyn program. ZR 75-1 breast cancer cell line showed antagonistic effect between endoxifen and chysophanol or rhein. CI, combination index. ^*P < 0.05, ^**P < 0.01.