CASP9 and breast cancer: The same situation was also observed in MDA-MB-231 estrogen-independent breast cancer cells, where the percentage of the control group with active caspase 9 was 5.5 ± 1.0%, while it was 6.6 ± 1.1% (1.5 μM) and 7.0 ± 0.9% (3 μM) in cells treated with cisplatin.