Increased Red Cell Superoxide Dismutase Activity Is Associated with Cancer Risk: A Hidaka Cohort Study

Superoxide dismutase (SOD) catalyzes the highly reactive superoxide anion to form hydrogen peroxide, which facilitates cell proliferation and death. We investigated whether red cell SOD (R-SOD) activity is associated with an increased risk of cancer in a Japanese general population. We prospectively analyzed data from 1,921 participants (800 men and 1,121 women; age, 58.7 ± 14.7 years) in a Hidaka cohort study. After a median follow-up period of 10.9 years, 160 participants had developed cancer. The Cox proportional hazards model was used to estimate quartile-specific HRs and 95% confidential intervals (CI) for cancer risk. After adjustment for potential cancer risk factors including age, sex, current smoking habit, alcohol use, physical activities, body mass index, plasma immunoreactive insulin, and non-high-density lipoprotein cholesterol levels, we found a significant association between R-SOD activity and an increased risk of cancer (HR, 1.61; 95% CI, 1.03-2.52; P = 0.037). In analyses conducted separately by sex, a significant association was found in men (HR, 2.49; 95% CI, 1.35-4.59; P = 0.003) but not women (HR, 1.46; 95% CI, 0.70-3.05; P = 0.320). After excluding participants who developed cancer within 5 years of the baseline survey, the association was more evident in men (HR, 4.64; 95% CI, 1.88-11.45; P = 0.001). We found no association with cancer risk in women (HR, 1.01; 95% CI, 0.39-2.65; P = 0.983). Increased R-SOD activities were associated with an increased risk of cancer, particularly in men in this population.

Our study is the first to show that increased R-SOD activity is associated with a significantly higher cancer risk in men but not in women. Antioxidative enzymes such as SOD are essential for maintaining cellular redox balance. Their roles in cancer development and prevention are yet to be fully elucidated.