The microsomal epoxide hydrolase Tyr113His polymorphism: Association with risk of ovarian cancer

Functional significance has been demonstrated in vitro for the exon 3 T-->C Tyr113His amino acid substitution polymorphism of the microsomal epoxide hydrolase (EPHX) gene. The higher activity or fast TT genotype was previously reported to be associated with an increased risk of ovarian cancer, and this association may reflect enhanced activation of endogenous or exogenous substrates to more reactive and mutagenic derivatives. Components of cigarette smoke are examples of exogenous substrates subject to such bioactivation, and smoking exposure may thus modify the risk associated with the EPHX polymorphism. We examined 545 cases of epithelial ovarian cancer and 287 unaffected controls for this EPHXT-C genetic variant to investigate whether, in the Australian population, the TT genotype was associated with (i) specific ovarian tumor characteristics; (ii) risk of ovarian cancer, overall or for specific subgroups; and (iii) risk of ovarian cancer in smokers specifically. Genotyping was carried out using the Perkin-Elmer ABI Prism 7700 Sequence Detection System for fluorogenic polymerase chain reaction allelic discrimination. Stratification of the ovarian cancer cases according to tumor behavior (low malignant potential or invasive), grade, stage, and p53 immunohistochemical status failed to show any heterogeneity with respect to the genotype defined by the EPHX polymorphism. There was a suggestion of heterogeneity with respect to histologic subtype (P= 0.03), largely due to a decreased frequency of the TT genotype in endometrioid tumors. EPHX genotype distribution did not differ significantly between unaffected controls and ovarian cancer cases (overall, low malignant potential, or invasive) either overall or after stratification by smoking status. However, the TT genotype was associated with a decreased risk of invasive ovarian cancer of the endometrioid subtype specifically (age-adjusted odds ratio = 0.38, 95% confidence interval=0.17-0.87). The results suggest that the proposed EPHX-mediated bioactivation of components of cigarette smoke to mutagenic forms is unlikely to be involved in the etiology of ovarian cancer in general but that a greater rate of EPHX-mediated detoxification may decrease the risk of endometrioid ovarian cancer. (C) 2001 Wiley-Liss, Inc.

A single nucleotide polymorphism in the 5' untranslated region of RAD51 and risk of cancer among BRCA1/2 mutation carriers

RAD51 colocalizes with both BRCA1 and BRCA2, and genetic variants in RAD51 would be candidate BRCA1/2 modifiers. We searched for RAD51 polymorphisms by sequencing 20 individuals. We compared the polymorphism allele frequencies between female BRCA1/2 mutation carriers with and without breast or ovarian cancer and between population-based ovarian cancer cases with BRCA1/2 mutations to cases and controls without mutations. We discovered two single nucleotide polymorphisms (SNPs) at positions 135 g-->c and 172 g-->t of the 5' untranslated region. In an initial group of BRCA1/2 mutation carriers, 14 (21%) of 67 breast cancer cases carried a c allele at RAD51:135 g-->c, whereas 8 (7%) of 119 women without breast cancer carried this allele. In a second set of 466 mutation carriers from three centers, the association of RAD51:135 g-->c with breast cancer risk was not confirmed. Analyses restricted to the 216 BRCA2 mutation carriers, however, showed a statistically significant association of the 135 c allele with the risk of breast cancer (adjusted odds ratio, 3.2; 95% confidence limit, 1.4-40). BRCA1/2 mutation carriers with ovarian cancer were only about one half as likely to carry the RAD51:135 g-->c SNP. Analysis of the RAD51:135 g-->c SNP in 738 subjects from an Israeli ovarian cancer case-control study was consistent with a lower risk of ovarian cancer among BRCA1/2 mutation carriers with the c allele. We have identified a RAD51 5' untranslated region SNP that may be associated with an increased risk of breast cancer and a lower risk of ovarian cancer among BRCA2 mutation carriers. The biochemical basis of this risk modifier is currently unknown.

The human melanocortin-1 receptor locus: analysis of transcription unit, locus polymorphism and haplotype evolution

The complete sequence of the MCIR locus has been assembled, the coding region of the gene is intronless and placed within a 12 kb region flanked by the NULP1 and TUBB4 genes. The immediate promoter region has an E-box site with homology to the M-box consensus known to bind the microphthalmia transcription factor (MITF), however, promoter deletion analysis and transactivation studies have failed to show activation through this element by MITF. Polymorphism within the coding region, immediate 5' promoter region and a variable number tandem repeat (VNTR) minisatellite within the locus have been examined in a collection of Caucasian families and African individuals. Haplotype analysis shows linkage disequilibrium between the VNTR and MCIR coding region red hair variant alleles which can be used to estimate the age of these missense changes. Assuming a mean VNTR mutation rate of 1% and a star phylogeny, we estimate the Arg151Cys variant arose 7500 years before the present day, suggesting these variants may have arisen in the Caucasian population more recently than previously thought. (C) 2001 Published by Elsevier Science B.V.

The Cys282Tyr polymorphism in the HFE gene in Australian Parkinson's disease patients

Iron homeostasis is altered in Parkinson's disease (PD). The HFE protein is an important regulator of cellular iron homeostasis and variations within this gene can result in iron overload and the disorder known as hereditary haemochromatosis. We studied the Cys282Tyr single nucleotide polymorphism as a genetic risk factor for PD in two distinct and separately collected cohorts of Australian PD patients and controls. In the combined cohort comprising 438 PD patients and 485 control subjects, we revealed an odds ratio for possession of the 282Tyr allele of 0.61 (95% confidence interval, Cl = 0.42-0.90, P = 0.011) from univariate chi-squared and 0.59 (95% Cl = 0.39-0.90, P = 0.014) after logistic regression analyses (correcting for potential confounding factors). These results suggest that possession of the 282Tyr allele may offer some protection against the development of PD. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.

Variation in coumarin 7-hydroxylase activity associated with genetic polymorphism of cytochrome P450 2A6 and the body status of iron stores in adult Thai males and females

The relationships between catalytic activity of cytochrome P450 2A6 (CYP2A6), polymorphism of CYP2A6 gene, gender and levels of body iron stores were analysed in a sample group of 202 apparently healthy Thais, aged 1947 years. Eleven individuals were found to have high activity of CYP2A6, judged by the relatively large amounts (11.2-14.6 mg) of 7-hydroyxcoumarin (7-OHC) excreted 3 h following administration of 15 mg of coumarin. Ten individuals, however, did not excrete any 7-OHC. Of these 10, four were found to have no CYP2A6 gene (whole gene deletion; CYP2A6*4 allele). The frequency of the CYP2A6 alleles; *1A, *1B and *4 in the whole sample group was 52, 40 and 8% while the frequency of the CYP2A6 gene types; *1A/* 1A, *1A/* 1B, *1B/* 1B, *1A/* 4, *1BI* 4, *4/* 4 was 29, 41, 16, 7, 5 and 2%. Subjects having CYP2A6* 1A/* 1B gene-type group were found to have higher rates of coumarin 7-hydroxylation compared with those of the CYP2A6* 1B/* 1B and CYP2A6* 1A/* 4 gene types. The inter-individual variability in CYP2A6 catalytic activity was therefore attributed in part to the CYP2A6 genetic polymorphism. Variation in CYP2A6 activity in this sample group was not associated with gender but, interestingly, it did show an inverse association with plasma ferritin; an indicator of body iron stores. Higher rates of coumarin 7-hydroxylation were found in individuals with low body iron stores (plasma ferritin < 20 μg/l) compared with subjects having normal body iron store status. Subjects (n = 16) with iron overload (plasma ferritin > 300 mug/l) also tended to have elevated rates of coumarin 7-hydroxylation. These results suggest an increased CYP2A6 expression in subjects who have excessive body iron stores. Further investigations into the underlying factors that may lead to increased expression of CYP2A6 in association with abnormal body iron stores are currently in progress in our laboratory. Pharmacogenetics 12:241-249 (C) 2002 Lippincott Williams Wilkins.

Exploring complex fitness surfaces: Multiple ornamentation and polymorphism in male guppies

The sexual ornamentation used by male guppies to attract females comprises many components, each of which varies considerably among males. Although natural and sexual selection have been shown to contribute to divergence among populations in male sexual ornaments, the role of sexual selection in maintaining polymorphism within populations is less clear. We used both parametric quadratic regression and nonparametric projection pursuit regression techniques to reveal the major axes of non-linear sexual selection on male ornaments. We visualized the fitness surfaces defined by these axes using thin-plate splines to allow a direct comparison of the two methodologies. Identification of the major axes of selection and their visualization was critical in determining the form and strength of nonlinear selection. Both types of analysis revealed fitness surfaces comprising three peaks, suggesting that there is more than one way to make an attractive guppy. Disruptive selection may be an important process underlying the presence of multiple sexual ornaments and may contribute to the maintenance of the high levels of polymorphism in male sexual ornaments found in guppy populations.

Single-nucleotide polymorphism in the CD14 promoter and periodontal disease expression in a Japanese population

It has been reported that there is a relationship between a single-nucleotide polymorphism (SNP) in the promoter region of the CD 14 gene at position -159 (C-->T) and infectious diseases. The aim of the present study was to test the hypthesis that expression of this SNP correlates with periodontal disease in a Japanese population. The CD14 genotype was determined in 163 subjects with periodontitis and in 104 age- and gender-matched control subjects without periodontitis. The genotype distribution and allele frequency within the periodontitis patients were not significantly different from those of control subjects. There was, however, a significant difference in the genotype distribution between young patients (< 35 yrs) and older patients (greater than or equal to 35 yrs). These findings suggest that CD14-159C/T polymorphism is not related to the development of periodontitis in a Japanese population, but that, within the periodontitis subjects, expression of the SNP may be related to early disease activity.

Osteoarthritis of the hands, hips and knees in an Australian twin sample - Evidence of association with the aggrecan VNTR polymorphism

Age-related changes in the composition of the cartilage matrix may be associated with the development of osteoarthritis, a relatively late-onset disease characterised by the destruction of joint cartilage. In order to investigate whether differences in the VNTR polymorphic region of aggrecan affect cartilage functionality and therefore the development of osteoarthritis, we examined the aggrecan polymorphic genotypes of a sample of 134 Australian twins aged over 50 (including 34 monozygotic and 27 dizygotic twin pairs). Clinical measures of hand, hip and knee osteoarthritis, as well as self-reported bone and joint pain, were tested for association with the aggrecan polymorphism. The results were consistent with either a deleterious effect of allele 27, or a protective effect of alleles 25 and 28, providing some additional evidence for an association between the aggrecan VNTR polymorphism and osteoarthritis of the hands, hips and knees.

The role of melanocortin-1 receptor polymorphism in skin cancer risk phenotypes

We have examined melanocortin-1 receptor (MC1R) variant allele frequencies in the general population and in a collection of adolescent dizygotic and monozygotic twins to determine statistical associations of pigmentation phenotypes with increased skin cancer risk. This included hair and skin color, freckling, mole count and sun exposed skin reflectance. Nine variants were studied and designated as either strong R (OR = 63; 95% CI 32-140) or weak r (OR = 5; 95% CI 3-11) red hair alleles. Penetrance of each MC1R variant allele was consistent with an allelic model where effects were multiplicative for red hair but additive for skin reflectance. To assess the interaction of the brown eye color gene BEY2/OCA2 on the phenotypic effects of variant MC1R alleles we imputed OCA2 genotype in the twin collection. A modifying effect of OCA2 on MC1R variant alleles was seen on constitutive skin color, freckling and mole count. In order to study the individual effects of these variants on pigmentation phenotype we have established a series of human primary melanocyte strains genotyped for the MC1R receptor. These include strains which are MC1R wild-type consensus, variant heterozygotes, and homozygotes for strong R alleles Arg151Cys and Arg160Trp. Ultrastructural analysis demonstrated that only consensus strains contained stage III and IV melanosomes in their terminal dendrites whereas Arg151Cys and Arg160Trp homozygous strains contained only immature stage I and II melanosomes. Such genetic association studies combined with the functional analysis of MC1R variant alleles in melanocytic cells should provide a link in understanding the association between pigmentary phototypes and skin cancer risk.

Toxicological aspects of treatment to remove cyanobacterial toxins from drinking water determined using the heterozygous P53 transgenic mouse model

The presence of toxic cyanobacteria in drinking water reservoirs renders the need to develop treatment methods for the 'safe' removal of their associated toxins. Chlorine has been shown to successfully remove a range of cyanotoxins including microcystins, cylindrospermopsin and saxitoxins. Each cyanotoxin requires specific treatment parameters, particularly solution pH and free chlorine residual. However, currently there has not been any investigation into the toxicological effect of solutions treated for the removal of these cyanotoxins by chlorine. Using the P53(def) transgenic mouse model mate and female C57BL/6J hybrid mice were used to investigate potential cancer inducing effects from such oral dosing solutions. Both purified cyanotoxins and toxic cell-free extract cyanobacterial solutions were chlorinated and administered over 90 and 170 days (respectively) in drinking water. No increase in cancer was found in any treatment. The parent cyanotoxins, microcystins, cylindrospermopsin and saxitoxins were readily removed by chlorine. There was no significant increase in the disinfection byproducts trihalomethanes or haloacetic acids, levels found were well below guideline values. Histological examination identified no effect of treatment solutions except male mice treated with chlorinated cylindrospermopsin (as a cell free extract). In this instance 40% of males were found to have fatty vacuolation in their livers, cause unknown. It is recommended that further toxicology be undertaken on chlorinated cyanobacterial solutions, particularly for non-genotoxic carcinogenic compounds, for example the Tg. AC transgenic mouse model. (C) 2003 Elsevier Science Ltd. All rights reserved.

XRCC3 THR241MET polymorphism influence on nuclear buds frequency in exposed to formaldehyde

Formaldehyde (FA), also known as formalin, formal and methyl aldehydes, is a colorless, flammable, strong-smelling gas. It has an important application in embalming tissues and that result in exposures for workers in the pathology anatomy laboratories and mortuaries. Occupational exposure to FA has been shown to induce nasopharyngeal cancer and has been classified as carcinogenic to humans (group 1) on the basis of sufficient evidence in humans and sufficient evidence in experimental animals. Manifold in vitro studies clearly indicated that FA is genotoxic. FA induced various genotoxic effects in proliferating cultured mammalian cells. The cytokinesis-block micronucleus (CBMN) assay was originally developped as an ideal system form easuring micronucleus (MN), however it can also be used to measure nucleoplasmic bridges (NBP) and nuclear buds (NBUD). Over the past decade another unique mechanism of micronucleus formation, known as nuclear budding has emerged. NBUDS is considered as a marker of gene amplification and/or altered gene dosage because the nuclear budding process is the mechanism by which cells removed amplified and/excess DNA.

Effects of physical exercise training in DNA damage and repair - could the difference be in hOGG1 Ser326Cys polymorphism?

Acute physical exercise is associated with increased oxygen consumption, which could result in an increased formation of reactive oxygen species (ROS). ROS can react with several organic structures, namely DNA, causing strand breaks and a variety of modified bases in DNA. Physical exercise training seems to decrease the incidence of oxidative stress-associated diseases, and is considered as a key component of a healthy lifestyle. This is a result of exercise-induced adaptation, which has been associated with the possible increase in antioxidant activity and in oxidative damage repair enzymes, leading to an improved physiological function and enhanced resistance to oxidative stress (Radak et al. 2008). Human 8-oxoguanine DNA glycosylase 1 (hOGG1) is involved in the base excision repair (BER) pathway and encodes an enzyme responsible for removing the most common product of oxidative damage in DNA, 8-hydroxyguanine (8-OH-G). The genetic polymorphism of hOGG1 at codon 326 results in a serine (Ser) to cysteine (Cys) amino acid substitution (Ser326Cys). It has been suggested that the carriers of at least one hOGG1Cys variant allele exhibit lower 8-OH-G excision activity than the wild-type (Wilson et al. 2011). The aim of this study was to investigate the possible influence of hOGG1 Ser326Cys polymorphism on DNA damage and repair activity in response to 16 weeks of combined physical exercise training, in thirty healthy Caucasian men. Comet assay was carried out using peripheral blood lymphocytes and enabled the evaluation of DNA damage, both strand breaks and FPG-sensitive sites, and DNA repair activity. Genotypes were determined by PCR-RFLP analysis. The subjects with Ser/Ser genotype were considered as wild-type group (n=20), Ser/Cys and Cys/Cys genotype were analyzed together as mutant group (n=10). Regarding differences between pre and post-training in the wild-type group, the results showed a significant decrease in DNA strand breaks (DNA SBs) (p=0.002) and also in FPG-sensitive sites (p=0.017). No significant differences were observed in weight (p=0.389) and in lipid peroxidation (MDA) (p=0.102). A significant increase in total antioxidant capacity (evaluated by ABTS) was observed (p=0.010). Regarding mutant group, the results showed a significant decrease in DNA SBs (p=0.008) and in weight (p=0.028). No significant differences were observed in FPG-sensitive sites (p=0.916), in ABTS (p=0.074) and in MDA (p=0.086). No significant changes in DNA repair activity were observed in both genotype groups. This preliminary study suggests the possibility of different responses in DNA damage to physical exercise training, considering the hOGG1 Ser326Cys polymorphism.

Risk of colorectal cancer associated with the C677T polymorphism in 5,10-methylenetetrahydrofolate reductase in Portuguese patients depends on the intake of methyl-donor nutrients

Background: Polymorphisms located in genes involved in the metabolism of folate and some methyl-related nutrients are implicated in colorectal cancer (CRC). Objective: We evaluated the association of 3 genetic polymorphisms [C677T MTHFR (methylene tetrahydrofolate reductase), A2756G MTR (methionine synthase), and C1420T SHMT (serine hydroxymethyltransferase)] with the intake of methyl-donor nutrients in CRC risk. Design: Patients withCRC(n 196) and healthy controls (n 200) matched for age and sex were evaluated for intake of methyl-donor nutrients and the 3 polymorphisms. Results: Except for folate intake, which was significantly lower in patients (P 0.02), no differences were observed in the dietary intake of other methyl-donor nutrients between groups. High intake of folate ( 406.7 g/d) was associated with a significantly lower risk of CRC (odds ratio: 0.67; 95% CI: 0.45, 0.99). The A2756G MTR polymorphism was not associated with the risk of developing CRC. In contrast, homozygosity for the C677TMTHFRvariant (TT) presented a 3.0-fold increased risk of CRC (95% CI: 1.3, 6.7). Similarly, homozygosity for the C1420T SHMT polymorphism also had a 2.6-fold increased risk (95% CI: 1.1, 5.9) of developing CRC. When interactions between variables were studied, low intake of all methyl-donor nutrients was associated with an increased risk ofCRC in homozygous participants for the C677T MTHFR polymorphism, but a statistically significant interaction was only observed for folate (odds ratio: 14.0; 95% CI: 1.8, 108.5). No significant associations were seen for MTR or SHMT polymorphisms. Conclusion: These results show an association between the C677T MTHFR variant and different folate intakes on risk of CRC.