S100A9 and hepatocellular carcinoma: To verify if S100A9 was associated with elevated ROS levels, HCC cells were treated with H2O2, N‐acetyl‐L‐cysteine (NAC, ROS scavenger),[21] or Mito‐tempo (intramitochondrial ROS scavenger)[22, 23] to change cellular or mitochondrial ROS levels.