Nodakenin Induces ROS-Dependent Apoptotic Cell Death and ER Stress in Radioresistant Breast Cancer

Angelica gigas exerts powerful anti-tumor and anti-cancer effects in various cancer cell types. However, there have been few studies regarding the anti-cancer effect of nodakenin, a bioactive compound of Angelica gigas, in vivo and in vitro on breast cancers. I found that nodakenin, in a concentration-dependent manner, inhibits breast cancer cell viability and decreases the tumor volume in mice. Additionally, nodakenin induces caspase-3-dependent apoptosis in breast cancer cells; however, the combination of Z-VAD-FMK and nodakenin suppresses the caspase-3-dependent apoptotic cell death. Furthermore, nodakenin mediates apoptotic cell death via the PERK-mediated signaling pathway and calcium (Ca(2+)) release, and nodakenin combined with thapsigargin induces synergistic cell death by inhibiting sarco/endoplasmic reticulum (ER) Ca(2+)-ATPase. However, knockdown of PERK or CHOP inhibits Ca(2+) generation and caspase-dependent apoptosis in nodakenin-treated breast cancer cells. Nodakenin induces ROS and Ca(2+) generation, ER stress, and apoptotic cell death; however, the knockdown of Nox4 inhibits ROS generation and ER stress- and caspase-dependent apoptotic cell death. In addition, nodakenin combined with radiation overcomes radioresistance in radioresistant breast cancer cells by suppressing epithelial–mesenchymal transition phenotypes, including the decrease in E-cadherin and the increase in N-cadherin and vimentin. Therefore, these findings indicate that nodakenin may be a novel therapeutic strategy for breast cancers.