Figure 3

Target validation of CIP2A. A, Ectopic expression of CIP2A protected MDA-MB-231 (left) and MDA-MB-468 (right) cells from the apoptotic effect of bortezomib. Note that MDA-MB-231 and MDA-MB-468 cells with ectopic expression of CIP2A also had constitutively higher expression of p-Akt compared to wild-type cell clones. Columns, mean (n = 3); bars, SD; *P < 0.05. Cells were transfected with CIP2A and were selected for eight weeks by G-418. Analysis of apoptotic cells was performed by flow cytometry after cells were sequentially exposed to DMSO or bortezomib 500 nM for 36 hours. B, Downregulation of CIP2A by siRNA increased bortezomib-induced apoptosis in MCF-7 cells. Columns, mean (n = 3); bars, SD; *P < 0.05. Cells were transfected with either control (scrambled siRNA) or CIP2A siRNA for 48 h oursand then exposed to bortezomib at 1000 nM for 36 hours. CIP2A, cancerous inhibitor of PP2A; DMSO, dimethyl sulfoxide; SiRNA, small interfering RNA; SD, standard deviation.