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Figure 1 | Breast Cancer Research

Figure 1

From: CIP2A is a target of bortezomib in human triple negative breast cancer cells

Figure 1

Differential apoptotic effects and similar proteasome inhibition induced by bortezomib in breast cancer cells. A, Dose- and time-escalation effects of bortezomib (50 nM, 100 nM and 500 nM) on apoptosis in five breast cancer cell lines (HCC-1937, MDA-MB-231, MDA-MB-468, MCF-7 and MDA-MD-453). Cells were exposed to bortezomib at the indicated doses for 12, 24 and 36 hours. Apoptotic cells were determined by flow cytometry. Columns, mean (n = 3); bars, SD; *P < 0.05. B, Bortezomib exerted an efficient and similar dose-dependent effect on proteasome inhibition as measured by proteasome activity assays in the five breast cancer cell lines. Cells were exposed to bortezomib at the indicated doses for 24 hours before measurement of proteasome activity. Columns, mean (n = 3); bars, SD; *P < 0.05. C, Bortezomib increased cytoplasmic protein levels of IκB-α, a cellular inhibitor of NF-κB and a known proteasome substrate, both in sensitive (HCC-1937, MDA-MB-231 and MDA-MB-468) and resistant (MCF-7 and MDA-MB-453) cells, suggesting similar proteasome inhibition in all these cells. Cells were treated with DMSO or 500 nM bortezomib at the indicated time point. Cytoplasmic extracts were prepared and assayed for IκB-α by western blot. Data are representative of three independent experiments. DMSO, dimethyl sulfoxide; SD, standard deviation.

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