After MCF-7 and MDA-MB-231 cells treated with 5 mM NAC 2-h before 60 μM AMP treatment, GRP78 and CHOP expressions induced by AMP were attenuated in both breast cancer cells, compared with those treated with AMP alone (Figure 7A), suggesting that eliminating ROS accumulation by NAC could alleviate the ER stress. This evidence concerns the gene DDIT3 and breast cancer.