Significance of superoxide dismutase (SOD) in human colorectal cancer tissue: correlation with malignant intensity.

The significance of superoxide dismutase (SOD) activity in colorectal cancer tissue was determined from the aspect of the antioxidant defense system. SOD activity and thiobarbituric acid reactive substance were measured in the tumor, in tissues adjacent to the tumor, and in regions that appeared normal, and the results were analyzed in terms of various histopathological factors (stage of disease, depth of invasion, venous invasion, etc.). DNA ploidy pattern and cell proliferation in cancer tissue were also measured, and the results analyzed in relation to SOD activity. SOD activity in cancer tissue was higher than in the other two regions. SOD activity in cancer tissue increased with the progression of stage, and changed with the depth of invasion. There was a significant difference in SOD activity between patients with venous invasion and those in whom this was absent. Stepwise regression analysis suggested that venous invasion was the most significant factor influencing SOD activity. The proliferation index was high in cancer tissue with low SOD activity. The incidence of aneuploidy was high in cancer with high SOD activity, whereas the incidence of diploidy was high in cancer with low SOD activity. These results suggest that elucidation of the antioxidant system in cancer tissue can provide us with a better strategy for cancer treatment.