Withaferin a suppresses estrogen receptor-α expression in human breast cancer cells.

We have shown previously that withaferin A (WA), a promising anticancer constituent of Ayurvedic medicine plant Withania somnifera, inhibits growth of MCF-7 and MDA-MB-231 human breast cancer cells in culture and MDA-MB-231 xenografts in vivo by causing apoptosis. However, the mechanism of WA-induced apoptosis is not fully understood. The present study was designed to systematically determine the role of tumor suppressor p53 and estrogen receptor-α (ER-α) in proapoptotic response to WA using MCF-7, T47D, and ER-α overexpressing MDA-MB-231 cells as a model. WA treatment resulted in induction as well as increased S15 phosphorylation of p53 in MCF-7 cells, but RNA interference of this tumor suppressor conferred modest protection at best against WA-induced apoptosis. WA-mediated growth inhibition and apoptosis induction in MCF-7 cells were significantly attenuated in the presence of 17β-estradiol (E2). Exposure of MCF-7 cells to WA resulted in a marked decrease in protein levels of ER-α (but not ER-β) and ER-α regulated gene product pS2, and this effect was markedly attenuated in the presence of E2. WA-mediated down-regulation of ER-α protein expression correlated with a decrease in its nuclear level, suppression of its mRNA level, and inhibition of E2-dependent activation of ERE2e1b-luciferase reporter gene. Ectopic expression of ER-α in the MDA-MB-231 cell line conferred partial but statistically significant protection against WA-mediated apoptosis, but not G2/M phase cell cycle arrest. Collectively, these results indicate that WA functions as an anti-estrogen, and the proapoptotic effect of this promising natural product is partially attenuated by p53 knockdown and E2-ER-α.

Hahm ER ，Lee J ，Huang Y ，Singh SV ... -  《-》

Withaferin A inhibits experimental epithelial-mesenchymal transition in MCF-10A cells and suppresses vimentin protein level in vivo in breast tumors.

We have shown previously that withaferin A (WA), a bioactive component of the medicinal plant Withania somnifera, inhibits growth of cultured and xenografted human breast cancer cells and prevents breast cancer development and pulmonary metastasis incidence in a transgenic mouse model. The present study was undertaken to determine if the anticancer effect of WA involved inhibition of epithelial-mesenchymal transition (EMT). Experimental EMT induced by exposure of MCF-10A cells to tumor necrosis factor-α (TNF-α) and transforming growth factor-β1 (TGF-β) was partially reversed by treatment with WA but not by its structural analogs withanone or withanolide A. Combined TNF-α and TGF-β treatments conferred partial protection against MCF-10A cell migration inhibition by WA. Inhibition of TNF-α and TGF-β-induced MCF-10A cell migration by WA exposure was modestly attenuated by knockdown of E-cadherin protein. MCF-7 and MDA-MB-231 cells exposed to WA exhibited sustained (MCF-7) or transient (MDA-MB-231) induction of E-cadherin protein. On the other hand, the level of vimentin protein was increased markedly after 24 h treatment of MDA-MB-231 cells with WA. WA-induced apoptosis was not affected by vimentin protein knockdown in MDA-MB-231 cells. Protein level of vimentin was significantly lower in the MDA-MB-231 xenografts as well as in MMTV-neu tumors from WA-treated mice compared with controls. The major conclusions of the present study are that (a) WA treatment inhibits experimental EMT in MCF-10A cells, and (b) mammary cancer growth inhibition by WA administration is associated with suppression of vimentin protein expression in vivo.

Lee J ，Hahm ER ，Marcus AI ，Singh SV ... -  《-》

Down-regulation of estrogen receptor-alpha and rearranged during transfection tyrosine kinase is associated with withaferin a-induced apoptosis in MCF-7 breast cancer cells.

Zhang X ，Mukerji R ，Samadi AK ，Cohen MS ... -  《BMC Complementary and Alternative Medicine》

Withaferin A causes FOXO3a- and Bim-dependent apoptosis and inhibits growth of human breast cancer cells in vivo.

Stan SD ，Hahm ER ，Warin R ，Singh SV ... -  《-》

Autophagy fails to alter withaferin A-mediated lethality in human breast cancer cells.

Hahm ER ，Singh SV 《-》