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BU-32: a novel proteasome inhibitor for breast cancer
Joseph K Agyin1, Bindu Santhamma, Hareesh B Nair
1Department of Biochemistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229, USA. agyinj@uthscsa.edu
Introduction:
Proteasome inhibition provides an attractive approach to cancer therapy and may have application in the treatment of breast cancer. However, results of recent clinical trials to evaluate the effect of the proteasome inhibitor Bortezomib (Velcade, also called PS-341) in metastatic breast cancer patients have shown limited activity when used as a single agent. This underscores the need to find new and more efficacious proteasome inhibitors. In this study, we evaluate the efficacy of the novel proteasome inhibitor BU-32 (NSC D750499-S) using in vitro and in vivo breast cancer models.
Methods:
We have recently synthesized a novel proteasome inhibitor (BU-32) and tested its growth inhibitory effects in different breast cancer cells including MCF-7, MDA-MB-231, and SKBR3 by in vitro cytotoxicity and proteasomal inhibition assays. The apoptotic potential of BU32 was tested using flow cytometry and analyzing cell cycle regulatory proteins. In vivo tumor xenograft studies for solid tumor as well as tumor metastasis were conducted using MDA-MB-231-GFP cells.
Results:
We report for the first time that BU-32 exhibits strong cytotoxicity in a panel of cell lines: MDA-MB-231 (IC50 = 5.8 nM), SKBR3 (IC50 = 5.7 nM) and MCF-7 cells (IC50 = 5.8 nM). It downregulates a wide array of angiogenic marker genes and upregulates apoptotic markers, including Bid and Bax. Incubation of MDA-MB-231 cells with BU-32 results in the accumulation of cell cycle inhibitor proteins p21 and p27 and stabilization of the tumor suppressor protein p53. Studies in in vivo solid tumor and metastasis models show significant effect with a 0.06 mg/kg dose of BU-32 and marked reduction in tumor burden in the skeleton.
Conclusions:
We have shown that BU-32 is effective in cultured breast cancer cells and in breast cancer xenografts. The results suggest its potential benefit in breast cancer treatment.
Insights
A novel proteasome inhibitor, BU-32, shows potent anti-cancer effects in breast cancer models. This compound effectively reduces tumor growth and metastasis, suggesting its potential as a new breast cancer therapeutic.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Proteasome inhibition is a promising cancer therapy strategy.
- Bortezomib (Velcade) has shown limited efficacy as a single agent in metastatic breast cancer.
- There is a need for novel, more effective proteasome inhibitors.
Purpose of the Study:
- To evaluate the efficacy of a novel proteasome inhibitor, BU-32 (NSC D750499-S).
- To assess BU-32's activity in in vitro and in vivo breast cancer models.
Main Methods:
- Cytotoxicity and proteasomal inhibition assays in MCF-7, MDA-MB-231, and SKBR3 breast cancer cells.
- Flow cytometry and cell cycle analysis to assess apoptotic potential.
- In vivo tumor xenograft studies for solid tumors and metastasis using MDA-MB-231-GFP cells.
Main Results:
- BU-32 demonstrated potent cytotoxicity against breast cancer cell lines (IC50 values around 5.8 nM).
- BU-32 downregulated angiogenic markers and upregulated apoptotic markers (Bid, Bax).
- BU-32 induced cell cycle arrest and stabilized p53; in vivo studies showed significant tumor burden reduction.
Conclusions:
- BU-32 is effective against cultured breast cancer cells and in vivo xenograft models.
- BU-32 exhibits significant anti-tumor and anti-metastatic effects.
- These findings suggest BU-32's potential as a beneficial agent for breast cancer treatment.
