Oxidative stress enhances carcinogenesis due to DNA damage. Manganese superoxide dismutase (MnSOD) Val16Ala polymorphism has been recently associated with breast and prostate cancer. The role of oxidative stress in male breast cancer is poorly investigated due to the low prevalence of this neoplasia. We studied the relationship between prostate cancer (PC), male (MBC) and female breast cancer (FBC) and this polymorphism in a case-control study. Human genetic polymorphism Val16Ala of MnSOD was obtained from blood and paraffin-embedded tumor samples. The polymorphism was determined in 11 cases of MBC, 51 cases of PC, 89 cases of FBC and 372 age-adjusted healthy controls by polymerase chain reaction-restriction fragment length polymorphism techniques using restriction enzyme Hae III. Chi-square or Fisher test were used to compare the MnSOD frequency distribution. The observed genotypic frequencies of all samples were AA = 9.6% (n = 50), VV = 25.4% (n = 133) and AV = 64% (n = 340), all at Hardy-Weinberg equilibrium. Breast and prostate cancer risk was elevated in male and female patients with the Ala/Ala genotype compared to controls (p = 0.006, odds ratio = 2.5, 95% confidence interval 1.393-4.541). Even though the frequency of the Ala allele was low (9.6%) in the studied population, these data support the hypothesis that MnSOD and oxidative stress play a significant role in breast cancer risk both in males and females and also brings new information on the role of this polymorphism in prostate cancer. This is the first study which provides some evidence that genetic polymorphism in the MnSOD gene may be associated with an increased risk of male breast cancer. Studies with a larger sample size are needed to confirm the findings.

Oxidative stress has been related to aging. Recent evidences suggest that a genetic dimorphism that encodes for either alanine or valine in superoxide dismutase (SOD2) is involved with oxidative stress. However, the current literature is still controversial, and the potential role of the Ala16Val polymorphism in human aging needs to be established. Here we investigated the role of the SOD2 polymorphism in: a) age-related mortality, b) morbidity (breast and prostate cancer), c) immunological markers, and d) DNA damage in peripheral blood cells. We did not find an association between SOD2 polymorphisms and mortality. However, the AA genotype was associated with increased risk for prostate and breast cancer, immunosenescence profile, as well as DNA damage. These data suggest that SOD2 presents characteristics that support the free radical theory of aging.

The epidemiological impact of SOD2 imbalance on prostate cancer (PC) risk associated with genetic variations has previously been studied. However, we found no previous studies clarifying the nature of SOD2 effects on prostate cancer. Here, we performed integrated in vivo and in vitro protocols that analyzed the association between Ala16Val-SOD2 polymorphism and prostate cancer aggressiveness at the time of diagnosis and evaluated the effect of the imbalance on PC proliferation using the DU-145 PC cell line treated with paraquat and porphyrin. In the pharmacological model, paraquat was used to increase superoxide anion levels and porphyrin was the SOD2 analog. The results confirmed the impact of superoxide-hydrogen peroxide imbalance on PC cell biology since porphyrin decreased cell proliferation and both treatments modulated antioxidant genes. Therefore, our results corroborate previous suggestions that alteration of redox status could be exploited therapeutically in the treatment of PC.

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