Abstract 227: Estrogen receptor-α and tumor initiating cells are novel targets of diallyl trisulfide in breast cancer cells

Abstract

Abstract Epidemiological studies suggest a protective role for Allium vegetables, such as garlic, against breast and other cancers. Diallyl trisulfide (DATS) is a promising oil-soluble anticancer metabolite generated after cutting or chewing of Allium vegetables. We have shown previously that DATS inhibits viability of human breast cancer cells (MCF-7 and MDA-MB-231) and a cell line derived from spontaneously developed tumor of a mouse mammary tumor virus-neu mouse by causing apoptosis induction. We also found that a non-tumorigenic normal human mammary epithelial cell line (MCF-10A) is resistant to cell death induction by DATS. Studies by others have demonstrated in vivo efficacy of DATS against MCF-7 xenografts in nude mice. The present study builds upon these observations and identifies novel targets of DATS in breast cancer cells. MCF-7 and T47D cells exposed to DATS exhibited downregulation of estrogen receptor-α (ER-α) protein, which peaked between 12 and 24 h post-treatment. Diallyl sulfide and diallyl disulfide analogs were relatively less effective in suppressing protein level of ER-α compared with DATS. The 17β-estradiol (E2)-induced expression of pS2, an ER-α target gene product, was also decreased in the presence of DATS. Downregulation of ER-α protein expression resulting from DATS treatment was accompanied by a decrease in nuclear level of ER-α, suppression of ER-α mRNA, and inhibition of ERE2e1b-luciferase reporter activity. Moreover, apoptotic cell death induced by DATS was partially but statistically significantly attenuated in the presence of E2 in MCF-7 cells as well as by overexpression of ER-α in MDA-MB-231 cells. DATS treatment inhibited breast cancer stem cell (bCSC) population as evidenced by flow cytometric analysis of CD44high/CD24low/epithelial specific antigen positive population, aldehyde dehydrogenase 1 activity, and mammosphere frequency in MCF-7 and SUM159 cells. Inhibition of bCSC by treatment with DATS was associated with downregulation of EZH2 and Kruppel-like factor 4 proteins in both MCF-7 and SUM159 cells. In conclusion, the present study identifies ER-α and bCSC as novel targets of DATS in mammary cancer cells. This study was supported by the grant RO1 CA113363-09 awarded by the National Cancer Institute. Citation Format: Eun-Ryeong Hahm, Su-Hyeong Kim, Shivendra V. Singh. Estrogen receptor-α and tumor initiating cells are novel targets of diallyl trisulfide in breast cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 227. doi:10.1158/1538-7445.AM2014-227