The localizations of Cu/Zn and Mn superoxide dismutase (SOD), which catalyzes the dismutation of superoxide radicals (O-2) to O2 and H2O2, were studied in 26 colo-rectal carcinomas by an immunohisto-chemical technique. We employed 10% formalin fixed paraffin embedded thin sections and used antihuman Cu/Zn- and Mn-SOD antibodies. The concentrations of both SODs in these tissues were also measured by a sandwich enzyme immunoassay technique. Both Cu/Zn and Mn SOD were more clearly immunohistochemically stained in cancer cells than in the normal mucosal layer of the large intestine. Among cancer tissues, both stained more clearly in many well-differentiated carcinomas. The concentration of Mn SOD was significantly elevated in cancer tissues, especially in well-differentiated malignancies. The ratio of the tissue concentration of Mn SOD to that of Cu/Zn SOD was also high in the well-differentiated carcinomas. Cu/Zn SOD changed its intra-cellular localization from a predominance in the basal portions of normal mucosal cells to a homogeneous distribution in the cytoplasm of cancer cells. In conclusion, both SODs appear to be related to tumor growth, and Mn SOD may play a role in the differentiation of colo-rectal carcinoma.
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