SOD3 and lung cancer: EcSOD, encoded by SOD3 gene, as the only superoxide dismutase in extracellular space, has unique characteristics and functions in cell signal transduction due to the regionalization of ROS signal (3).Compared with the other two kinds of intracellular SOD, the inhibitory effect of EcSOD on tumor is relatively new, and SOD3 gene has not been investigated in lung cancer.