Activity and protein level of CuZnSOD and MnSOD in benign and malignant liver tumors

Objectives: Superoxide dismutase (SOD) is a key antioxidant enzyme, responsible for scavenging of superoxide anion – a precursor of all reactive oxygen species (ROS). ROS are implicated in many pathologies, particularly in tumor disease. The aim of our work was to evaluate SOD isoformsʹ activity and protein level changes in liver tumors. Design and methods: Materials were obtained from patients with liver tumors and with liver cirrhosis diagnosed by routine histopathological examination. Activity and protein level of SOD were determined by means of the Beauchamp and Fridovich assay and by Western blot analysis. Results: Decreased activity of CuZnSOD and MnSOD and distinct differences in SOD isoformsʹ protein expression in liver cirrhosis were found. Results also showed higher protein level and activity of SOD isoforms in liver malignant tumors than in benign ones. Conclusions: Malignant tumors have a better antioxidant system than benign ones. Moreover, weakening of antioxidant mechanisms and accumulation of oxidative damage in cirrhotic liver could initiate liver carcinogenesis.