Our previous study suggests the involvement of acidosis-induced ROS production in breast cancer cells, leading to activation of NF-κB.13 As the present study reveals that both GSH and NAC suppress the acidosis-induced ERK activation, and subsequently inhibit nuclear localization of NF-κB, it may suggest that ROS acts at the upstream of ERK. The gene discussed is NFKB1; the disease is breast carcinoma.