A. MDA-MB-435 and MDA-MB-468 cells were transfected with an MCL-1 overexpression vector or mock vector. The effect of transfection on the levels of miR-101 expression was determined by qRT-PCR. **p < 0.01 vs. control. B. MDA-MB-435 cells were transfected with miR-101 mimics, miR-101 inhibitors, a MCL-1 overexpression vector, MCL-1 siRNA or a combination. The expression of MCL-1 mRNA was detected by qRT-PCR. C. MDA-MB-435 cells were transfected with miR-101 mimics, miR-101 inhibitors, an MCL-1 overexpression vector, MCL-1 siRNA or a combination. The apoptotic cells were evaluated by Annexin V-FITC and propidium iodine staining and then analyzed by FACS. D. MDA-MB-435 cells were transfected with miR-101 mimics, miR-101 inhibitors, an MCL-1 overexpression vector, MCL-1 siRNA or a combination. Mitochondrial membrane potential (MMP, Δψm) was determined at 48 h post-transfection. Green indicates apoptosis. E. MDA-MB-435 cells were transfected with miR-101 mimics, miR-101 inhibitors, a MCL-1 overexpression vector, MCL-1 siRNA or a combination. Cleaved caspase-3 and cleaved PRAP protein expression was evaluated by Western blot.