MnSOD gene polymorphism association with steroid-dependent cancer.

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.

Inhibition of the rat breast cytosolic bioactivation of ethanol to acetaldehyde by some plant polyphenols and folic acid.

There is a well-established association between alcohol consumption and breast cancer risk. About 4% of the breast cancers in developed countries are estimated to be attributable to drinking alcohol. The mechanism of tumor promotion by alcohol remains unknown. Recent studies from our laboratory and others showed the ability of mammary tissue to bioactivate ethanol to mutagenic/carcinogenic acetaldehyde and free radicals. Xanthine oxidoreductase (XOR) is an enzyme involved in those biotransformation processes. In the present study, we provide evidence of the ability of different natural polyphenols and of folic acid derivatives to inhibit the biotransformation of alcohol to acetaldehyde by rat breast cytosolic XOR. Folic acid and dihydrofolic acid, at concentrations of 10 microM, inhibited 100% and 84%, respectively, of the cytosolic acetaldehyde formation. Thirty-five polyphenols were tested in these initial experiments: ellagic acid, myricetin, quercetin, luteolin, and apigenin inhibited 79-95% at 10 microM concentrations. The remaining polyphenols were either less potent or noninhibitory of acetaldehyde formation at similar concentrations in these screening tests. Results are relevant to the known preventive effects of folic acid against alcohol-induced breast cancer and to their potential preventive actions if added to foods or alcoholic beverages.

Cellular distribution of phosphofructokinase activity and implications to metabolic regulation in human breast cancer.

Neoplastic cells generally present profound changes in glucose metabolism. The mechanisms underlying such process are numerous and all may involve altered cellular hormonal responses. Here we report the first evidence that cellular location of phosphofructokinase activity in human breast cancer tissues is different from the one observed in control tissues and that this phenomenon may be involved in the increased glycolytic flux observed in those cells. Through co-sedimentation techniques, we observed that 60% of phosphofructokinase activity in neoplastic tissues is located in an actin-enriched fraction, against 36% in control tissues. Additionally, metastatic tumor tissues presented a two fold increase in this particulate activity when compared to non-metastatic tumor samples. We propose that the alteration in cellular distribution of phosphofructokinase activity in human breast cancer tissues is a mechanism associated to the process of cell transformation and may be a consequence of the altered hormonal milieu observed in several types of cancer.

Cytosolic xanthine oxidoreductase mediated bioactivation of ethanol to acetaldehyde and free radicals in rat breast tissue. Its potential role in alcohol-promoted mammary cancer.

Epidemiological evidence links alcohol intake with increased risk in breast cancer. Not all the characteristics of the correlation can be explained in terms of changes in hormonal factors. In this work, we explore the possibility that alcohol were activated to acetaldehyde and free radicals in situ by xanthine dehydrogenase (XDh) and xanthine oxidase (XO) and/or aldehyde oxidase (AO). Incubation of cytosolic fraction with xanthine oxidoreductase (XDh+XO) (XOR) cosubstrates (e.g. NAD+, hypoxanthine, xanthine, caffeine, theobromine, theophylline or 1,7-dimethylxanthine) significantly enhanced the biotransformation of ethanol to acetaldehyde. The process was inhibited by allopurinol and not by pyrazole or benzoate or desferrioxamine and was not accompanied by detectable formation of 1HEt. However, hydroxylated aromatic derivatives of PBN were detected, suggesting either that hydroxyl free radicals might be formed or that XOR might catalyze aromatic hydroxylation of PBN. No bioactivation of ethanol to acetaldehyde was detectable when a cosubstrate of AO such as N-methylnicotinamide was included in cytosolic incubation mixtures. Results suggest that bioactivation of ethanol in situ to a carcinogen, such as acetaldehyde, and potentially to free radicals, might be involved in alcohol breast cancer induction. This might be the case, particularly also in cases of a high consumption of purine-rich food (e.g. meat) or beverages or soft drinks containing caffeine.

[Tyrosine-protein kinase activity in breast neoplasm. Comparison with activity obtained in benign diseases and in normal tissues]. / Actividad de tirosina-protein-quinasas en cáncer de mama. Comparación con la actividad obtenida en patologías benignas y en tejidos normales.

Tyrosine protein kinase (TPK) activity is associated to malignant cellular transformation. This work compares TPK activity in 27 surgical biopsy samples of mammary carcinoma, 10 samples of fibroadenomas, 13 samples of fibrocystic breast disease and 27 samples of normal mammary tissue. TPK activity was determined in tissue homogenates using (Val5) angiotensin II as exogenous substrate. In samples of mammary carcinoma, TPK activity was 33.86 +/- 31.98 pmol P32/mg protein/30 min. This value was significantly higher that those observed in fibrocystic disease (3.92 +/- 2.35), fibroadenomas (13.86 +/- 10.9) and normal tissue (3.56 +/- 3.02).

Actividad de tirosina-proteina-quinasas en cáncer de mama: comparación con la actividad obtenida en patologías benognas y en tejidos normales / Tyrosina-protein-kinase activity in breath cancer: comparison between benign pathologies and normal tissues activity

Tyrosine protein kinase (TPK) activity is associated to malignant cellular transformation. This work compares TPK activity in 27 surgical biopsy samples of mammary carcinoma, 10 samples of normal mammary tissue. TPK activity was determined in tissue homogenates using (Val5) angiotensin II as exogenous substrate. In samples of mammary carcinoma, TPK activity was 33.86 ñ 31.98 pmol P32/mg protein/30 min. This value was significantly higher that those observed in fibrocystic disease (3.92 ñ 2.35), fibroadenomas (13.86 ñ 10.9) and normal tissue (3.56 ñ 3.02)

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

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.

Actividad de glutation s-transferasas durante el desarrollo de la placenta y glándula mamaria en ratas: efecto de la nutrición materna / Activity of glutathione s-transferase during the development of placenta and mammary glands in rats: effect of maternal nutrition

Se estudian los cambios en la actividad de glutatión S-transferasas (GSHTr) durante el desarrollo de la glándula mamaria y crecimiento de placenta y el efecto de la nutrición materna en estos cambios, durante la preñez y lactancia en ratas. Ratas hembras vírgenes se someten a una restricción dietética alimentándolas desde los 50 días de edad y durante la preñez y lactancia con el 50% (g/100 gramos rata) de la ingesta voluntaria de un grupo control de la misma edad, de una dieta preparada con caseína al 25% suplementada con 0,3% de DL Metionina. A los 16 ó 18 ó 20 días de preñez ó 5- día de lactancia se sacrifican en cada oportunidad 15 ratas de cada grupo control (C) y desnutridas (D) y se les extraen las placentas y las glándulas mamarias inguinales y abdominales. Se estudian en glándulas y órgano la actividad de GSHTr. Los resultados informan que el avance de la preñez disminuyó la actividad de GSHTr en placenta, pero mantuvo con una ligera elevación la actividad en glándulas mamaria. La lactogénesis estimuló dramáticamente la actividad de GSHTr en glándula mamaria; pero la desnutrición crónica materna deprimió la actividad en esta glándula durante la preñez y lactancia. Se discuten los resultados en relación al bajo efecto protector de los tejidos maternos de rata desnutrida contra los efectos tóxicos de substancias que pueden ser transferidos a través de la leche materna