Low activity of manganese superoxide dismutase (MnSOD) in blood of lung cancer patients with smoking history: relationship to oxidative stress.

Lung cancer is the primary cause of cancer death in the world. Although it is well established that tobacco smoke causes lung cancer, not all smokers develop lung cancer. Manganese superoxide dismutase (MnSOD), a major determinant of antioxidants in matrix mitochondria, plays a pivotal role in eliminating anion superoxide free radical generated from the tobacco smoke. The aim of this study was to analyze the enzyme activity of MnSOD in blood of lung cancer patients with a smoking history in relationship to oxidative stress. Samples were taken from leukocyte cells of 20 lung cancer patients in Persahabatan Hospital Jakarta. Control groups included 50 healthy smokers and 50 non smokers, all aged over 40 years. The MnSOD activity determined biochemically based on the inhibition of xanthin oxidase, of lung cancer patients was lower than the control group's (p<0.001). Plasma MDA levels, determined by reaction with thiobarbituric acid (TBA), were not significantly different (p=0.479), whereas plasma carbonyl levels were elevated (p=0.003). Free radical production in lung cancer patients thus appeared high. Smoker controls also tended to exhibit lower MnSOD and higher carbonyl radicals than their non-smoking counterparts. Continue cigarette smoke exposure may increase production of ROS and bring about a reduction of MnSOD, which could play a role in lung cancer development.