Superoxide dismutase activity and superoxide dismutase-1 gene methylation in normal and tumoral human breast tissues

MARTHA S. BIANCHI; NÉSTOR O. BIANCHI; ALEJANDRO DANIEL BOLZAN

CANCER GENETICS AND CYTOGENETICS

ELSEVIER SCIENCE INC

Año: 1992 vol. 59 p. 26 - 29

0165-4608

The superoxide dismutase (SOD) activities in normal and tumor breast tissues from 14 human females were determined by the epinephrine autoxidation assay. SOD levels showed a marked interindividual variability in normal and malignant cells. However, each donor had a higher SOD activity in cancer than in normal tissue samples. In three cases in which Mn- and CuZnSOD activities were determined, it was found that tumoral increases in SOD were due to increases in both enzymatic forms. Therefore, it seems reasonable to assume a similar situation for all cases in our series. The level of DNA methylation in the SOD-1 gene was assessed in the first four donors. The four cases exhibited full methylation of SOD-1 genes corresponding to normal as well as to cancer cells. It is concluded that the variability in CuZnSOD activities is not related with the state of methylation of the SOD-1 gene. MspI restriction fragment polymorphisms between DNA samples from normal and malignant cells were detected in the four DNA donors. This phenomenon may be due to point mutations changing the frequency of MspI sites or to methylation of the external C in CCGG sequences.