Role of antioxidants in lung cancer

Abstract

Lung cancer is a major health problem.  In Thailand, it is the second most common in men and the fourth in women. Srinagarind cancer unit statistical data (2005) revealed that lung cancer is the second and the fifth in men and women admitted to Srinagarind hospital. Lung cancer can be classified into 2 groups, small cell lung cancer and non-small cell lung cancer. It can be treated by operation, chemotherapy and radiotherapy. The major cause of lung cancer is smoking which causes free radical formation in the body. However, our body has antioxidant systems, both non-enzyme system e.g. b-carotene, lycopene, vitamin E, vitamin C and enzyme system e.g. glutathione peroxidase (GPx) which has selenium as a cofactor, intracellular superoxide dismutase (SOD), extracellular superoxide dismutase (EC-SOD) and paraoxonase I (PON I). The b-carotene experiments (ATBC and CARET in the Finnish and American, respectively) showed that antioxidants may act as prooxidant in smokers.  In animal model, b-carotene could decrease incidence of lung cancer in ferret depending on time and dosage. Lycopene supplementation influenced on cell proliferation and apoptosis pathway. However, lycopene supplementation is better for prostate cancer patients than lung cancer patients. Vitamin E decreases lung tumor in mice, its derivatives decrease inflammation and adaptation of Src gene. Vitamin C combined with N-acetylcystein decreased cell variability and malignant cells. It also activated lung cancer in chromium treated cells. Selenium has a chemopreventive role. GPx level was increased in lung cancer patients. SOD was higher in smoking group than non-smoking one. EC-SOD decreased inflammation, lung fibrosis and lung damage in animal. PON I level was lower in lung cancer patients than in normal people due to responded lipid peroxidation. However, combined supplementation may be a good alternative by which further study is required regarding the impact of these antioxidants in biological system, which includes beneficial as well as toxic health effect.