Zhang Xuan, Timmermann Barbara, Samadi Abbas K, Cohen Mark S
Department of Surgery, University of Kansas School of Medicine, Kansas City, KS 66160, USA.
Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS 66045, USA.
ISRN Biochem. 2012 Sep 1;2012:707586. doi: 10.5402/2012/707586. eCollection 2012.
The purpose of this study was to examine the regulation of prosurvival factors heat shock factor 1 (HSF1) and breast cancer susceptibility gene 1 (BRCA1) by a natural withanolide withaferin A (WA) in triple negative breast cancer cell lines MDA-MB-231 and BT20. Western analysis was used to examine alternations in HSF1 and BRCA1 protein levels following WA treatment. A protein synthesis inhibitor cycloheximide and a proteasome inhibitor MG132 were used to investigate the mechanisms of HSF1 and BRCA1 regulation by WA. It was found that WA induced a dose-dependent decrease in HSF1 and BRCA1 protein levels. Further analysis showed that levels of HSF1 and BRCA1 proteins decreased rapidly after WA treatment, and this was attributed to WA-induced denaturation of HSF1 and BRCA1 proteins and subsequent degradation via proteasome-dependent, and protein-synthesis dependent mechanism. In summary, WA induces denaturation and proteasomal degradation of HSF1 and BRCA1 proteins. Further studies are warranted to examine the contribution of HSF1 and BRCA1 depletion to the anticancer effects of WA in breast cancer.
本研究的目的是检测天然睡茄内酯类化合物印度辣木宁A（WA）对三阴性乳腺癌细胞系MDA-MB-231和BT20中生存促进因子热休克因子1（HSF1）和乳腺癌易感基因1（BRCA1）的调控作用。采用蛋白质免疫印迹分析检测WA处理后HSF1和BRCA1蛋白水平的变化。使用蛋白质合成抑制剂放线菌酮和蛋白酶体抑制剂MG132来研究WA对HSF1和BRCA1的调控机制。结果发现，WA可诱导HSF1和BRCA1蛋白水平呈剂量依赖性降低。进一步分析表明，WA处理后HSF1和BRCA1蛋白水平迅速下降，这归因于WA诱导的HSF1和BRCA1蛋白变性，随后通过蛋白酶体依赖性和蛋白质合成依赖性机制降解。总之，WA可诱导HSF1和BRCA1蛋白变性和蛋白酶体降解。有必要进一步研究HSF1和BRCA1缺失对WA在乳腺癌中的抗癌作用的贡献。
