Department of Pharmacology & Chemical Biology, University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, 2.32A Hillman Cancer Center Research Pavilion, 5117 Centre Avenue, Pittsburgh, PA 15213, USA.
Breast Cancer Res Treat. 2012 Aug;134(3):1067-79. doi: 10.1007/s10549-012-2043-3. Epub 2012 Apr 4.
Benzyl isothiocyanate (BITC) is a promising anticancer constituent of edible cruciferous vegetables with in vivo efficacy against chemically induced as well as oncogene-driven breast cancer in experimental rodents. However, the mechanism underlying anticancer effect of BITC is not fully understood. This study was undertaken to determine the role of Notch signaling in anticancer responses to BITC as this pathway is often hyperactive in human breast cancer. Exposure of MCF-7, MDA-MB-231, and SUM159 human breast cancer cells to pharmacologic concentrations of BITC (2.5 and 5 μM) resulted in cleavage (activation) of Notch1, Notch2, and Notch4, which was accompanied by induction of γ-secretase complex components Presenilin1 and/or Nicastrin. The BITC-mediated cleavage of Notch was associated with its transcriptional activation as revealed by RBP-Jk and Hes-1A/B luciferase reporter assays. Inhibition of cell migration or cell viability resulting from BITC exposure was not influenced by pharmacological suppression of Notch1 using a γ-secretase inhibitor or RNA interference of Notch1 as well as Notch4. On the other hand, the BITC-mediated inhibition of cell migration, but not cell viability, was significantly augmented by siRNA and shRNA knockdown of Notch2 protein. Furthermore, the BITC-mediated inhibition of MDA-MB-231 xenograft growth in vivo was associated with a significant increase in nuclear levels of cleaved Notch2 and Hes-1 proteins. In conclusion, the results of this study indicate that (a) BITC treatment activates Notch2 in cultured and xenografted human breast cancer cells, and (b) Notch2 activation impedes inhibitory effect of BITC on cell migration.
苄基异硫氰酸酯 (BITC) 是一种有前途的抗癌成分，存在于可食用的十字花科蔬菜中，对实验动物的化学诱导和致癌基因驱动的乳腺癌具有体内疗效。然而，BITC 抗癌作用的机制尚未完全阐明。本研究旨在确定 Notch 信号通路在 BITC 抗癌反应中的作用，因为该通路在人类乳腺癌中通常过度活跃。用药理浓度的 BITC（2.5 和 5 μM）处理 MCF-7、MDA-MB-231 和 SUM159 人乳腺癌细胞，导致 Notch1、Notch2 和 Notch4 的裂解（激活），同时诱导 γ-分泌酶复合物成分早老素 1 和/或 Nicastrin。BITC 介导的 Notch 裂解与 Notch 的转录激活有关，如 RBP-Jk 和 Hes-1A/B 荧光素酶报告基因检测所揭示的。用 γ-分泌酶抑制剂抑制 Notch1 或 Notch1 和 Notch4 的 RNA 干扰对 BITC 引起的细胞迁移或细胞活力抑制没有影响。另一方面，通过 siRNA 和 shRNA 敲低 Notch2 蛋白，显著增强了 BITC 介导的细胞迁移抑制，但对细胞活力抑制没有影响。此外，BITC 介导的 MDA-MB-231 异种移植物在体内生长的抑制与 Notch2 蛋白裂解和 Hes-1 蛋白核水平的显著增加有关。总之，本研究结果表明：（a）BITC 处理激活了培养和异种移植的人乳腺癌细胞中的 Notch2；（b）Notch2 激活阻碍了 BITC 对细胞迁移的抑制作用。
