Susceptibility to arsenic-induced hyperkeratosis and oxidative stress genes myeloperoxidase and catalase

Prenatal arsenic exposure alters keratinocyte stem cell fate through persistent activation of IGF2R-MAPK cascade leading to aggravated skin carcinogenesis in mice offspring

Chronic exposure to arsenic (As) promotes skin carcinogenesis in humans and potentially disturbs resident stem cell dynamics, particularly during maternal and early life exposure. In the present study, we demonstrate how only prenatal arsenic exposure disturbs keratinocyte stem cell (KSC) conditioning using a BALB/c mice model. Prenatal As exposure alters the normal stemness (CD34, KRT5), differentiation (Involucrin), and proliferation (PCNA) program in skin of offspring with progression of age as observed at 2, 10, and 18 weeks. Primary KSCs isolated from exposed animal at Day-2 showed increased survival (Bax:Bcl-xL, TUNEL assay), proliferation (BrdU), and differentiation (KRT5, Involucrin) potential through the activation of pro-carcinogenic IGF2R-MAPK cascade (IGF2R-G(α)q-MEK1-ERK1/2). This was associated with reduced enrichment of histone H3K27me3 and its methylase, EZH2 along with increased binding of demethylase, KDM6A at Igf2r promoter. Altered KSCs conditioning through disturbed Igf2r imprint contributed to impaired proliferation and differentiation and an aggravated tumor response in offspring.

A review of pharmacogenetic studies in the Bangladeshi population

Pharmacogenetics (PGx)-guided prescribing is an evidence-based precision medicine strategy. Although the past two decades have reported significant advancements in both the quality and quantity of PGx research studies, they are seldom done in developing countries like Bangladesh. This review identified and summarized PGx studies conducted in the Bangladeshi population by searching PubMed and Google Scholar. Additionally, a quality evaluation of the identified studies was also carried out. Eleven PGx studies were identified that looked at the effects of genetic variants on blood thinners (CYP2C9, VKORC1, and ITGB3), cancer drugs (TPMT, MTHFR, DPYD, ERCC1, GSTP1, XPC, XRCC1, TP53, XPD, and ABCC4), statins (COQ2, CYP2D6, and CYP3A5), and prednisolone (ABCB1, CYP3A5, and NR3C1) in the Bangladeshi population. Most studies were of low to moderate quality. Although the identified studies demonstrated the potential for PGx testing, the limited PGx literature in the Bangladeshi population poses a significant challenge in the widespread implementation of PGx testing in Bangladesh.

The Genetic Diversity and Dysfunctionality of Catalase Associated with a Worse Outcome in Crohn's Disease

Chronic gut inflammation in Crohn’s disease (CD) is associated with an increase in oxidative stress and an imbalance of antioxidant enzymes. We have previously shown that catalase (CAT) activity is permanently inhibited by CD. The purpose of the study was to determine whether there is any relationship between the single nucleotide polymorphisms (SNPs) in the CAT enzyme and the potential risk of CD associated with high levels of oxidative stress. Additionally, we used protein and regulation analyses to determine what causes long-term CAT inhibition in peripheral white mononuclear cells (PWMCs) in both active and inactive CD. We first used a retrospective cohort of 598 patients with CD and 625 age-matched healthy controls (ENEIDA registry) for the genotype analysis. A second human cohort was used to study the functional and regulatory mechanisms of CAT in CD. We isolated PWMCs from CD patients at the onset of the disease (naïve CD patients). In the genotype-association SNP analysis, the CAT SNPs rs1001179, rs475043, and rs525938 showed a significant association with CD (p < 0.001). Smoking CD patients with the CAT SNP rs475043 A/G genotype had significantly more often penetrating disease (p = 0.009). The gene expression and protein levels of CAT were permanently reduced in the active and inactive CD patients. The inhibition of CAT activity in the PWMCs of the CD patients was related to a low concentration of CAT protein caused by the downregulation of CAT-gene transcription. Our study suggests an association between CAT SNPs and the risk of CD that may explain permanent CAT inhibition in CD patients together with low CAT gene and protein expression.

Gender difference in arsenic biotransformation is an important metabolic basis for arsenic toxicity

BACKGROUND

Arsenic metabolism enzymes can affect the toxic effects of arsenic. However, the effects of different genders on the metabolites and metabolic enzymes in liver arsenic metabolism is still unclear. This study analyzed the gender differences of various arsenic metabolites and metabolic enzymes and further explored the effects of gender differences on arsenic metabolism in liver tissues of rats.

METHODS

Rats were treated with high/medium/low doses of iAs³⁺ or iAs⁵⁺. Liver pathological changes were observed with electron microscopy. The monomethyl aracid (MMA) and dimethyl aracid (DMA) was determined by high performance liquid chromatography-hydride generation atomic fluorescence spectroscopy. S-adenosylmethionine (SAM), arsenate respiratory reductase (ARR), nicotinamide adenine dinucleotide (NAD), purine nucleoside phosphorylase (PNP), pyruvate kinase (PK), and myeloperoxidase (MPO) SAM, ARR, NAD, PNP, PK, and MPO were determined by enzyme-linked immunoassay. RT-qPCR was used to determine Arsenic (+ 3 oxidation state) methyltransferase (AS3MT).

RESULTS

The iAs³⁺ and iAs⁵⁺ at high doses induced pathological changes in the liver, such as increased heterochromatin and lipid droplets. Compared within the same group, MMA and DMA were statistically significant in iAs^{3 +} high, iAs^{3 +} medium and iAs⁵⁺ low dose groups (P < 0.05). MMA of male rats in iAs³⁺ high and medium groups was higher than that of female rats, and the DMA of male rats was lower than that of female rats. As3MT mRNA in the male iAs³⁺ high group was higher than that of females. Besides, compared between male and female, only in iAS³⁺ low dose, iAS³⁺ medium dose, iAS⁵⁺ low dose, and iAS⁵⁺ medium dose groups, there was significant difference in SAM level (P < 0.05). Compared within the same group, male rats had significantly higher PNP and ARR activities while lower PK activity than female rats (P < 0.05). Between the male and female groups, only the iAS³⁺ high dose and medium dose group had a statistically significant difference (P < 0.05). The NAD activity of females in iAS³⁺ high dose group was higher than that of males.

CONCLUSION

The gender differences in the arsenic metabolism enzymes may affect the biotransformation of arsenic, which may be one of the important mechanisms of arsenic toxicity of different sexes and different target organs.

Association of arsenic-induced cardiovascular disease susceptibility with genetic polymorphisms

Inorganic arsenic (iAs) exposure has been reported to have an impact on cardiovascular diseases (CVD). However, there is not much known about the cardiac tissue injury of CVD patients in relation to iAs exposure and potential role of single nucleotide polymorphisms (SNPs) of genes related to iAs metabolism, oxidative stress, endothelial dysfunction and inflammation which may play important roles in such CVD cases. In this dual center cross-sectional study, based on the exclusion and inclusion criteria, we have recruited 50 patients out of 270, who came from known arsenic-affected and- unaffected areas of mainly Chittagong, Dhaka and Rajshahi divisions of Bangladesh and underwent open-heart surgery at the selected centers during July 2017 to June 2018. We found that the patients from arsenic affected areas contained significantly higher average iAs concentrations in their urine (6.72 ± 0.54 ppb, P = 0.028), nail (529.29 ± 38.76 ppb, P < 0.05) and cardiac tissue (4.83 ± 0.50 ppb, P < 0.05) samples. Patients' age, sex, BMI, hypertension and diabetes status adjusted analysis showed that patients from arsenic-affected areas had significantly higher iAs concentration in cardiac tissue (2.854, 95%CI 1.017-8.012, P = 0.046) reflecting higher cardiac tissue injury among them (1.831, 95%CI 1.032-3.249, P = 0.039), which in turn allowed the analysis to assume that the iAs exposure have played a vital role in patients' disease condition. Adjusted analysis showed significant association between urinary iAs concentration with AA (P = 0.012) and AG (P = 0.034) genotypes and cardiac iAs concentration with AA (P = 0.017) genotype of AS3MT rs10748835. The AG genotype of AS3MT rs10748835 (13.333 95%CI 1.280-138.845, P = 0.013), AA genotype of NOS3 rs3918181 (25.333 95%CI 2.065-310.757, P = 0.002), GG genotype of ICAM1 rs281432 (12.000 95%CI 1.325-108.674, P = 0.010) and AA genotype of SOD2 rs2758331 (13.333 95%CI 1.280-138.845, P = 0.013) were found significantly associated with CVD patients from arsenic-affected areas. Again, adjusted analysis showed significant association of AA genotype of AS3MT rs10748835 with CVD patients from arsenic affected areas. In comparison to the reference genotypes of the selected SNPs, AA of AS3MT 10748835, AG of NOS3 rs3918181 and AC of rs3918188, GG of ICAM1 rs281432, TT of VCAM1 rs3176867, AA of SOD2 rs2758331 and GT of APOE rs405509 significantly increased odds of cardiac tissue injury of CVD patients from arsenic affected areas. The results showed that the selected SNPs played a susceptibility role towards cardiac tissue iAs concentration and injury among CVD patients from iAs affected areas.

Joint effects of genomic markers and urinary methylation capacity associated with inorganic arsenic metabolism on the occurrence of cancers among residents in arseniasis-endemic areas: A cohort subset with average fifteen-year follow-up

Background

Chronic exposure to inorganic arsenic results in many cancers in susceptible persons. The metabolism of inorganic arsenic and genomic susceptibility are thought to be associated with cancer occurrence.

Methods

This study aims to examine the interaction of genomic susceptibility markers and urinary methylation capacity indicators involved in inorganic arsenic metabolism with all-cancer occurrence. This study conducted a follow-up on 96 residents to determine their urinary inorganic arsenic metabolites and genomic assay from an arseniasis area. Among them, 24 cancer developed. Multivariable Cox proportional hazards model was used to determine and estimate the candidate independent variables for cancer development.

Results

The residents with high inorganic arsenic exposure, high primary methylation index (PMI; MMA/InAs) (but lower secondary methylation index (SMI)), and non-heterogeneity type of genomic markers, including GSTO1, AS3MT, and MPO, tend to develop cancers. Subjects with higher PMI are at higher risk of developing cancers (HR = 1.66; 95% CI = 1.30–2.12). Cancer occurrence was greater among the CC type of GSTO1 (HR = 3.33; 95% CI = 1.11–10.00), CC type of AS3MT (HR = 19.21; 95% CI = 1.16–318.80), and AA type of MPO (HR = 13.40; 95% CI = 1.26–142.40). After adjusting confounders, a mutually moderating effect was revealed between genomic markers and methylation capacity on cancer occurrence.

Conclusions

This study found the hypermethylation responses to inorganic arsenic exposure and an array of genomic markers may increase the susceptibility of a wide range of organ cancers. The findings indicated a high-risk arsenic-exposed population to develop cancers. The phenotype of arsenic metabolism and genomic polymorphism suggested a potential preventive strategy for arsenic carcinogenesis.

Environmental arsenic exposure: From genetic susceptibility to pathogenesis

More than 200 million people in 70 countries are exposed to arsenic through drinking water. Chronic exposure to this metalloid has been associated with the onset of many diseases, including cancer. Epidemiological evidence supports its carcinogenic potential, however, detailed molecular mechanisms remain to be elucidated. Despite the global magnitude of this problem, not all individuals face the same risk. Susceptibility to the toxic effects of arsenic is influenced by alterations in genes involved in arsenic metabolism, as well as biological factors, such as age, gender and nutrition. Moreover, chronic arsenic exposure results in several genotoxic and epigenetic alterations tightly associated with the arsenic biotransformation process, resulting in an increased cancer risk. In this review, we: 1) review the roles of inter-individual DNA-level variations influencing the susceptibility to arsenic-induced carcinogenesis; 2) discuss the contribution of arsenic biotransformation to cancer initiation; 3) provide insights into emerging research areas and the challenges in the field; and 4) compile a resource of publicly available arsenic-related DNA-level variations, transcriptome and methylation data. Understanding the molecular mechanisms of arsenic exposure and its subsequent health effects will support efforts to reduce the worldwide health burden and encourage the development of strategies for managing arsenic-related diseases in the era of personalized medicine.

Individual susceptibility to arsenic-induced diseases: the role of host genetics, nutritional status, and the gut microbiome

Arsenic (As) contamination in water or food is a global issue affecting hundreds of millions of people. Although As is classified as a group 1 carcinogen and is associated with multiple diseases, the individual susceptibility to As-related diseases is highly variable, such that a proportion of people exposed to As have higher risks of developing related disorders. Many factors have been found to be associated with As susceptibility. One of the main sources of the variability found in As susceptibility is the variation in the host genome, namely, polymorphisms of many genes involved in As transportation, biotransformation, oxidative stress response, and DNA repair affect the susceptibility of an individual to As toxicity and then influence the disease outcomes. In addition, lifestyles and many nutritional factors, such as folate, vitamin C, and fruit, have been found to be associated with individual susceptibility to As-related diseases. Recently, the interactions between As exposure and the gut microbiome have been of particular concern. As exposure has been shown to perturb gut microbiome composition, and the gut microbiota has been shown to also influence As metabolism, which raises the question of whether the highly diverse gut microbiota contributes to As susceptibility. Here, we review the literature and summarize the factors, such as host genetics and nutritional status, that influence As susceptibility, and we also present potential mechanisms of how the gut microbiome may influence As metabolism and its toxic effects on the host to induce variations in As susceptibility. Challenges and future directions are also discussed to emphasize the importance of characterizing the specific role of these factors in interindividual susceptibility to As-related diseases.

Association between arsenic metabolism gene polymorphisms and arsenic-induced skin lesions in individuals exposed to high-dose inorganic arsenic in northwest China

Individuals in a given environment contaminated with arsenic have different susceptibilities to disease, which may be related to arsenic metabolism, age, gender, genetics and other factors. This study recruited 850 subjects, including 331 cases and 519 controls, from populations exposed to high levels of arsenic in drinking water in northwest China. Genotypes were determined using a custom-by-design 48-Plex SNPscan^TM kit. The results indicated that subjects who carried at least one C allele for GSTO1 rs11191979 polymorphism, at least one A allele for GSTO1 rs2164624, at least one A allele for GSTO1 rs4925, the AG genotype for GSTO2 rs156697, the AG genotype or at least one G allele for GSTO2 rs2297235 or the GG genotype or at least one G allele for PNP rs3790064 had an increased risk of arsenic-related skin lesions. In addition, the haplotype CT between rs4925 and rs11191979 appeared to confer a high risk of arsenic-included skin lesions (OR = 1.377, 95% CI = 1.03–1.84), as did the haplotype GCG among rs156697, rs157077 and rs2297235 (OR = 2.197, 95% CI = 1.08–4.44). The results showed that the variants of GSTO1, GSTO2 and PNP render the susceptible toward developing arsenic-induced skin lesions in individuals exposed to high-dose inorganic arsenic in northwest China.

Evaluation of the quality of life in patients with arsenic keratosis

BACKGROUND

Chronic exposure to inorganic arsenic is an important public health problem and leads to hyperpigmentation, hyperkeratosis, Bowen's disease and non-melanoma skin cancers in humans. Arsenic keratosis is the most common skin change that is associated with arsenic exposure. It may be an indicator of arsenic induced health hazards.

OBJECTIVE

To determine the needs of patients with arsenic keratosis by evaluating the impact of disease on the quality of life with respect to treatment and provide rehabilitation services.

METHODS

A total of 47 subjects with arsenic hyperkeratosis, were enrolled in this crossover study. The demographics, smoking status and the presence of chronic diseases diagnosed by the physician were recorded. Weight and height of the subjects were measured and BMI was calculated. The patients were asked to respond the visual analogue scale and EuroQoL-5D scales for assessing the pain and quality of life impairment associated with arsenic hyperkeratosis.

RESULTS

In the study group, moderate to severe problems were reported in 78.7% of patients for pain/uncomfortable condition domains and in 91.5% in anxiety/depression domains. Lower quality of life was reported in those with associated chronic disorders, at an advanced age, in thin patients and in those with severe lesions.

CONCLUSION

According to our knowledge, our study is the first one measuring the quality of life in patients with arsenic keratosis in the literature. By this study, we tried to underline the guidance of health services to be developed towards the needs of patients and the need for the development of new health policies by determining the requirements of these patients.

Impact of sodium arsenite on chromosomal aberrations with respect to polymorphisms of detoxification and DNA repair genes

Arsenic compounds can increase production of reactive oxygen species. Reactive oxygen species can induce double-strand breaks in DNA, which is a cause of chromosome aberrations (CAs). This study was conducted to determine the association between arsenic exposure and polymorphisms of genes involved in detoxification (glutathione S-transferase T1 [GSTT1], glutathione S-transferase M1 [GSTM1], glutathione S-transferase O2 [GSTO2], catalase [CAT], and NAD(P)H quinone oxidoreductase1 [NQO1]) as well as nonhomologous end joining DNA repair genes (XRCC4, XRCC5, and XRCC6) with induction of chromosomal aberrations. The participants consisted of 123 healthy males who were genotyped using polymerase chain reaction-based methods. Primary cultures of whole blood were treated with sodium arsenite (NaAsO(2); iAs(III); at final concentration 1 µmol/L), mitomycin C (at final concentration 60 ηg/mL; as positive control), or untreated. For each culture, mitotic index (MI), chromatid breaks (CBs), CAs, and total percentage of aberrant cells were determined. The levels of CB and percentage of aberrant cells were significantly higher in the TT genotype of CAT (C-262T polymorphism) than the CC genotype. The CB value in samples with GSTM1 active genotype was significantly higher than the null genotype. The MI in samples with TT genotype of NQO1 (C609T polymorphism) was significantly higher than MI in samples having CC and CT genotypes. There was no association between MI, CB, CA, and percentage of aberrant cells and polymorphisms of XRCC4, XRCC5, and XRCC6.

Human catalase, its polymorphisms, regulation and changes of its activity in different diseases

Catalase (CAT) is a well-studied enzyme that plays an important role in protecting cells against the toxic effects of hydrogen peroxide. In human, it has been implicated in different physiological and pathological conditions. This review summarizes the information available on the function and role of CAT polymorphisms in pathogenesis of various pathophysiological states as well as on the regulation of CAT gene expression. Numerous studies have described the CAT polymorphisms and their link with various diseases. Changes in the CAT levels were reported in many different diseases and polymorphisms in the CAT gene were shown to be associated with different pathophysiological states, e.g. hypertension, diabetes mellitus, insulin resistance, dyslipidaemia, asthma, bone metabolism or vitiligo. Regulation of the CAT gene expression plays an important role in the levels of CAT. The catalase gene expression is regulated by various mechanisms involving e.g. peroxisome proliferator-activated receptor γ (PPARγ), tumour necrosis factor α (TNF-α), p53 protein and hypermethylation of CpG islands in the catalase promoter. Transcription of the CAT gene is mainly influenced by the -262 C/T and -844 A/G polymorphisms. A common polymorphism -262 C/T in the promoter region has been found to be associated with altered CAT activities. Apart from genetic factors, the activities of CAT may be affected by age, seasonal variations, physical activity, or a number of chemical compounds. Future investigations are necessary to elucidate the role of CAT in pathogenesis of oxidative stress-related diseases.

Frequency of polymorphism -262 c/t in catalase gene and oxidative damage in Slovak children with bronchial asthma

INTRODUCTION

Bronchial asthma is a complex disease in which genetic factors, environmental factors and oxidative damage are responsible for the initiation and modulation of disease progression. If antioxidant mechanisms fail, reactive oxygen species damage the biomolecules followed by progression of the disease. Catalase is one of the most important endogenous enzymatic antioxidants. In the present study, we examined the hypothesis that increased oxidative damage and polymorphism in the CAT gene (-262 promoter region, C/T) are associated with childhood bronchial asthma.

PATIENTS AND METHODS

Genotyping of the polymorphisms in the CAT gene in healthy (249) and asthmatic children (248) was performed using polymerase chain reaction-restriction fragment length polymorphism. Markers of oxidative damage: content of sulfhydryl groups and thiobarbituric acid-reactive substances were determined by spectrophotometry in children.

RESULTS

The TT genotype of catalase was more frequent among the asthmatic patients (22.6%) than in healthy children (4.8%) (odds ratio=5.63; 95% confidence interval=2.93-10.81, P<.001). The amount of sulfhydryl groups decreased significantly and conversely, the content of thiobarbituric acid-reactive substances increased significantly in bronchial asthma and in catalase TT genotype compared to other catalase genotypes of this gene.

CONCLUSIONS

These results suggest that catalase polymorphism might participate in development of bronchial asthma and in enhanced oxidative damage in asthmatic children. Genetic variation of enzymatic antioxidants may modulate disease risk.

Catalase has a key role in protecting cells from the genotoxic effects of monomethylarsonous acid: a highly active metabolite of arsenic

Although it is widely known that arsenic-contaminated drinking water causes many diseases, arsenic's exact mode of action (MOA) is not fully understood. Induction of oxidative stress has been proposed as an important key event in the toxic MOA of arsenic. The authors' studies are centered on identifying a reactive species involved in the genotoxicity of arsenic using a catalase (CAT) knockout mouse model that is impaired in its ability to breakdown hydrogen peroxide (H2 O2 ). The authors assessed the induction of DNA damage using the Comet assay following exposure of mouse Cat(+/) (+) and Cat(-) (/) (-) primary splenic lymphocytes to monomethylarsonous acid (MMA(III) ) to identify the potential role of H2 O2 in mediating cellular effects of this metalloid. The results showed that the Cat(-) (/) (-) lymphocytes are more susceptible to MMA(III) than the Cat(+/) (+) lymphocytes by a small (1.5-fold) but statistically significant difference. CAT activity assays demonstrated that liver tissue has approximately three times more CAT activity than lymphocytes. Therefore, Comet assays were performed on primary Cat(+/) (+) , Cat(+/) (-) , and Cat(-) (/) (-) hepatocytes to determine if the Cat(-) (/) (-) cells were more susceptible to MMA(III) than lymphocytes. The results showed that the Cat(-) (/) (-) hepatocytes exhibit higher levels of DNA strand breakage than the Cat(+/) (+) (approximately fivefold) and Cat(+/) (-) (approximately twofold) hepatocytes exposed to MMA(III) . Electron spin resonance using 5,5-dimethyl-1-pyrroline-N-oxide as the spin-trap agent detected the generation of ·OH via MMA(III) when H2 O2 was present. These experiments suggest that CAT is involved in protecting cells against the genotoxic effects of the ·OH generated by MMA(III) .

Trace elements and carcinogenicity: a subject in review

Cancer is known to be a multi-step process, which involves different stages including initiation, promotion, progression and metastasis. Chemical carcinogens including most trace elements can change any of these processes to induce their carcinogenic effects. Various studies confirm that cancer arises from the accumulation of irreversible DNA damage, which results from multiple mutations in critical genes in the body organ. Chemical carcinogens most often directly or after xenobiotic metabolism, act as genotoxic causes to induce DNA damage. Genotoxic carcinogen refers to a group of chemicals capable of producing cancer by directly altering the genetic material of target cells. Other carcinogens are however classified as non-genotoxic, which represents chemicals that are capable of producing cancer by some secondary mechanism not related to direct gene damage. They act as tumor promoters, endocrine-modifiers, receptor mediators, immunosuppressant, or inducers of tissue-specific toxicity and inflammatory responses. The diversity of modes of action, of non-genotoxic carcinogens, the tissue and species specificity and the absence of genotoxicity makes it extremely hard to predict their carcinogenic potential. The roles of trace metals (some of which are either genotoxic or non-genotoxic) in cancer development and inhibition have a complex character and have raised many questions because of their essential and toxic effects on people's health. Trace metals such as cadmium, nickel, arsenic, beryllium and chromium (VI) have been recognized as human or animal carcinogens by International Agency for Research on Cancer (IARC). The Carcinogenic capability of these metals depends mainly on factors such as oxidation states and chemical structures. The oxidative concept in metal carcinogenesis proposes that complexes formed by these metals, in vivo, in the vicinity of DNA, catalyze redox reactions, which in turn oxidize DNA. The most significant effect of reactive oxygen species in the carcinogenesis progression is DNA damage, which results in DNA lesions like strand breaks and the sister-chromatid exchange. This article reviews the carcinogenicity of various trace elements.

Efficient tumorigenesis by mutation-induced failure to terminate microRNA-mediated adaptive hyperplasia

Seven current contending cancer theories consider different sets of critical events as sufficient for tumorigenesis. These theories, most recently the microRNA dysregulation (MRD) theory, have overlapping attributes and extensive empirical support, but also some discrepancies, and some do not address both benign and malignant tumorigenesis. By definition, the most efficient tumorigenic pathways will dominate under conditions that selectively activate those pathways. The MRD theory provides a mechanistic basis to combine elements of the current theories into a new hypothesis that: (i) tumors arise most efficiently under stress that induces and sustains either protective or regenerative states of adaptive hyperplasia (AH) that normally are epigenetically maintained unless terminated; and (ii) if dysregulated by a somatic mutation that prevents normal termination, these two AH states can generate benign and malignant tumors, respectively. This hypothesis, but not multistage cancer theory, predicts that key participating AH-stem-cell populations expand markedly when triggered by stress, particularly chronic metabolic or oxidative stress, mechanical irritation, toxic exposure, wounding, inflammation, and/or infection. This hypothesis predicts that microRNA expression patterns in benign vs. malignant tumor tissue will correlate best with those governing protective vs. regenerative AH in that tissue, and that tumors arise most efficiently inmutagen-exposed stem cells that either happen to be in, or incidentally later become recruited into, an AH state.

Oxidative stress and skin cancer: an overview

Skin is the largest body organ that serves as an important environmental interface providing a protective envelope that is crucial for homeostasis. On the other hand, it is a major target for toxic insult by a broad spectrum of physical and chemical agents that are capable of altering its structure and function. There are a large number of dietary contaminants and drugs can manifest their toxicity in skin. These environmental toxicants or their metabolites are inherent oxidants and/or directly or indirectly drive the production of a variety of reactive oxidants also known as reactive oxygen species. These are short-lived entities that are continuously generated at low levels during the course of normal aerobic metabolism. These are believed to activate proliferative and cell survival signaling that can alter apoptotic pathways that may be involved in the pathogenesis of a number of skin disorders. The skin possesses an array of antioxidant defense mechanisms that interact with toxicants to obviate their deleterious effect. The "antioxidant power" of a food is an expression of its capability both to defend the human organism from the action of the free radicals and to prevent degenerative disorders. Plants like olive trees have their own built-in protection against the oxidative damage of the sun, and these built-in protectors function as cell protectors in our own body. Although many antioxidants have shown substantive efficacy in cell culture systems and in animal models of oxidant injury, unequivocal confirmation of their beneficial effects in human populations has proven elusive.

Gene expression of normal human epidermal keratinocytes modulated by trivalent arsenicals

Chronic exposure to inorganic arsenic (iAs) is associated with the development of benign and malignant human skin lesions including nonmelanoma skin cancers. The precise arsenical form(s) responsible for this carcinogenic effect are unknown, although trivalent inorganic arsenic (iAs(III)) and two of its toxic metabolites, monomethylarsonous acid (MMA(III)) and methylarsinous acid (DMA(III)), are attractive candidates. In an effort to better understand and compare their toxic effects in the skin, we compared the global gene expression profiles of normal human epidermal keratinocytes (NHEKs) exposed to varying noncytotoxic/slightly cytotoxic concentrations of iAs(III), MMA(III), and DMA(III) for 24 h. Exposure to each arsenical treatment group exhibited a dose effect in the number of altered genes and the magnitude of expression change in NHEKs. The most significant gene expression changes associated with iAs(III) and MMA(III) exposure were consistent with several key events believed to be important to As-driven skin carcinogenesis, namely induction of oxidative stress, increased transcript levels of keratinocyte growth factors, and modulation of MAPK and NF-κB pathways. At both comparable arsenical concentrations and comparable NHEK toxicity, greater potential carcinogenic effects were observed in MMA(III)-exposed NHEKs than those exposed to iAs(III), including involvement of more proinflammatory signals and increased transcript levels of more growth factor genes. In contrast, none of these above-mentioned transcriptional trends were among the most significantly altered functions in the DMA(III) treatment group. This study suggests the relative capacity of each of the tested arsenicals to drive suspected key events in As-mediated skin carcinogenesis is MMA(III) > iAs(III) with little contribution from DMA(III).

Blood selenium, glutathione peroxidase activity and antioxidant supplementation of subjects exposed to arsenic via drinking water

This work investigated serum selenium (Se) and glutathione peroxidase (GPx) levels in 25 Croatian subjects exposed to high levels of As from drinking water (median As level in urine: 620.74μg/g creatinine) and 25 controls (32.98μg/g creatinine). The exposed group had lower (p<0.001) median serum Se and GPx levels (Se: 82.34μg/l vs 59.02μg/l; GPx: 45.99U/g hemoglobin vs 38.38U/g hemoglobin). A subsample of 20 exposed subjects took part in a 2-month antioxidant supplementation trial which increased median GPx activity from 30.71 to 40.98U/g hemoglobin (p=0.041) and reduced total urinary As median from 680.15 to 501.96μg/g creatinine (p=0.051). The effect of selected catalase (-262C>T) and GPx1 (-593C>T) gene polymorphisms was also examined. The low Se status and GPx activity may heighten risk of adverse health effects, especially in genetically predisposed individuals. The outcome of antioxidant treatment indicates modulation of As metabolism and oxidative stress, relevance of which needs further research.

CAT C-262T and GPX1 Pro198Leu polymorphisms in a Turkish population

Oxidative stress is believed to play an important role in the pathogenesis of considerable number of complex diseases. The antioxidant enzymes catalase (CAT) and glutathione peroxidase (GPX) are important components of cell defense against oxidative stress, and polymorphisms in the genes which regulate their expression may contribute to differences in susceptibility of individuals to oxidative damage caused by reactive oxygen species. The aim of this study was to assess the distribution of CAT C-262T and GPX1 Pro198Leu genotypic variants in a Turkish population. Genotyping analyses of CAT and GPX1 were conducted in 250 unrelated, healthy volunteers by the PCR-RFLP assay. The allele frequencies were 0.784 (C) and 0.216 (T) for CAT and 0.636 (C) and 0.364 (T) for GPX1 Pro198Leu. The genotype frequencies were 0.632 (CC), 0.304 (CT), and 0.064 (TT) for CAT and 0.416 (CC), 0.44 (CT), and 0.144 (TT) for GPX1 Pro198Leu. The genotype frequencies did not deviate from Hardy-Weinberg equilibrium. The results are compared with those of other reported populations. They showed marked ethnic group differences.

Analysis of genomic dose-response information on arsenic to inform key events in a mode of action for carcinogenicity

A comprehensive literature search was conducted to identify information on gene expression changes following exposures to inorganic arsenic compounds. This information was organized by compound, exposure, dose/concentration, species, tissue, and cell type. A concentration-related hierarchy of responses was observed, beginning with changes in gene/protein expression associated with adaptive responses (e.g., preinflammatory responses, delay of apoptosis). Between 0.1 and 10 microM, additional gene/protein expression changes related to oxidative stress, proteotoxicity, inflammation, and proliferative signaling occur along with those related to DNA repair, cell cycle G2/M checkpoint control, and induction of apoptosis. At higher concentrations (10-100 microM), changes in apoptotic genes dominate. Comparisons of primary cell results with those obtained from immortalized or tumor-derived cell lines were also evaluated to determine the extent to which similar responses are observed across cell lines. Although immortalized cells appear to respond similarly to primary cells, caution must be exercised in using gene expression data from tumor-derived cell lines, where inactivation or overexpression of key genes (e.g., p53, Bcl-2) may lead to altered genomic responses. Data from acute in vivo exposures are of limited value for evaluating the dose-response for gene expression, because of the transient, variable, and uncertain nature of tissue exposure in these studies. The available in vitro gene expression data, together with information on the metabolism and protein binding of arsenic compounds, provide evidence of a mode of action for inorganic arsenic carcinogenicity involving interactions with critical proteins, such as those involved in DNA repair, overlaid against a background of chemical stress, including proteotoxicity and depletion of nonprotein sulfhydryls. The inhibition of DNA repair under conditions of toxicity and proliferative pressure may compromise the ability of cells to maintain the integrity of their DNA.

Global Gene Expression Profiling of Hyperkeratotic Skin Lesions from Inner Mongolians Chronically Exposed to Arsenic

The skin is an organ that is highly sensitive to chronic arsenic (As) exposure. Skin lesions such as hyperkeratoses (HKs) are common early manifestations of arsenicosis in humans. HKs can be precursor lesions of nonmelanoma skin cancers (NMSCs), but the driving forces behind their formation and how they may ultimately progress to NMSCs are unknown. The goal of this study was to examine the global gene expression profiles of As-related HKs in an effort to better understand gene expression changes that are potentially associated with early stages of As carcinogenesis. HK biopsies were removed from individuals living in an arsenicosis-endemic region in Inner Mongolia who had been exposed to high As levels in their drinking water for >20 years. Gene expression profiling was performed on RNA isolated from 7 individuals in this group and from 4 lesion-free skin samples from healthy individuals. Consistent with the pathological characteristics of the HK lesions, major functional categories and known canonical pathways represented by altered transcripts include those involved in development, differentiation, apoptosis, proliferation, and stress response. The results of this study may help define a signature profile of gene expression changes associated with long-term As exposure in the skin.

Association of AS3MT polymorphisms and the risk of premalignant arsenic skin lesions

Exposure to naturally occurring inorganic arsenic (iAs), primarily from contaminated drinking water, is considered one of the top environmental health threats worldwide. Arsenic (+3 oxidation state) methyltransferase (AS3MT) is the key enzyme in the biotransformation pathway of iAs. AS3MT catalyzes the transfer of a methyl group from S-adenosyl-L-methionine to trivalent arsenicals, resulting in the production of methylated (MAs) and dimethylated arsenicals (DMAs). MAs is a susceptibility factor for iAs-induced toxicity. In this study, we evaluated the association of the polymorphism in AS3MT gene with iAs metabolism and with the presence of arsenic (As) premalignant skin lesions. This is a case-control study of 71 cases with skin lesions and 51 controls without skin lesions recruited from a iAs endemic area in Mexico. We measured urinary As metabolites, differentiating the trivalent and pentavalent arsenical species, using the hydride generation atomic absorption spectrometry. In addition, the study subjects were genotyped to analyze three single nucleotide polymorphisms (SNPs), A-477G, T14458C (nonsynonymus SNP; Met287Thr), and T35587C, in the AS3MT gene. We compared the frequencies of the AS3MT alleles, genotypes, and haplotypes in individuals with and without skin lesions. Marginal differences in the frequencies of the Met287Thr genotype were identified between individuals with and without premalignant skin lesions (p=0.055): individuals carrying the C (TC+CC) allele (Thr) were at risk [odds ratio=4.28; 95% confidence interval (1.0-18.5)]. Also, individuals with C allele of Met287Thr displayed greater percentage of MAs in urine and decrease in the percentage of DMAs. These findings indicate that Met287Thr influences the susceptibility to premalignant As skin lesions and might be at increased risk for other adverse health effects of iAs exposure.

Well water arsenic exposure, arsenic induced skin-lesions and self-reported morbidity in Inner Mongolia

Residents of the Bayingnormen region of Inner Mongolia have been exposed to arsenic-contaminated well water for over 20 years, but relatively few studies have investigated health effects in this region. We surveyed one village to document exposure to arsenic and assess the prevalence of arsenic-associated skin lesions and self-reported morbidity. Five-percent (632) of the 12,334 residents surveyed had skin lesions characteristics of arsenic exposure. Skin lesions were strongly associated with well water arsenic and there was an elevated prevalence among residents with water arsenic exposures as low as 5 μg/L-10 μg/L. The presence of skin lesions was also associated with self-reported cardiovascular disease.

Genetic variations associated with interindividual sensitivity in the response to arsenic exposure

People are exposed to arsenic compounds environmentally, occupationally or therapeutically. In some areas, where arsenic is present in high proportions in the drinking water, this exposure represents an important health concern. Chronic exposure to arsenic leads to hyperkeratosis and loss of skin pigmentation, as well as to significant increases of different types of cancer in skin, lung, bladder and liver; in addition, other pathologies, such as vascular diseases, hepatotoxicity and diabetes, have also been related to arsenic exposure. Since high interindividual variability is observed among people exposed to equivalent doses, genetic susceptibility factors have been postulated to be involved. When inorganic arsenic enters into the body it undergoes metabolic conversion, in a process where methylation plays a crucial role. Trivalent forms, both inorganic and organic, are the most toxic and genotoxic and, for this reason, metabolic variations owing to variant alleles in genes involved in such a process have been the aim of several studies. Genes involved in other mechanisms, such as antioxidant defense and DNA-repair lesions, among others, have also been the subject of association studies. A survey of those studies related to individual susceptibility is summarized here. Results with genes involved in folate one-carbon metabolism and in arsenic transport across the cell membrane provide promising data for future studies.

NQO1, MPO, and the risk of lung cancer: a HuGE review

The aim of this study is to summarize the available molecular epidemiologic studies of lung cancer and metabolic genes, such as NAD(P)H quinone reductase 1 (NQO1) and myeloperoxidase (MPO). NQO1 plays a dual role in the detoxification and activation of procarcinogens whereas MPO has Phase I activity by converting lipophilic carcinogens into hydrophilic forms. Variant genotypes of both NQO1 Pro187 Ser and MPO G-463A polymorphisms may be related to low enzyme activity. The Pro/Ser and Ser/Ser genotypes combined of NQO1 was significantly associated with decreased risk of lung cancer in Japanese [random effects odds ratio (OR) = 0.70, 95% confidence interval (CI) = 0.56-0.88] among whom the variant allele is common. The variant genotype of MPO was associated with decreased risk of lung cancer among Caucasians (random effects OR = 0.70, 95% CI = 0.47-1.04). Gene-environment interactions in both polymorphisms may be hampered by inaccurate categorization of tobacco exposure. Evidence on gene-gene interactions is extremely limited. As lung cancer is a multifactorial disease, an improved understanding of such interactions may help identify individuals at risk for developing lung cancer. Such a study should include larger sample size and other polymorphisms in the metabolism of tobacco-derived carcinogens and address interactions with smoking status. The effects of polymorphisms are best represented by their haplotypes. In future studies on lung cancer, the development of haplotype-based approaches will facilitate the evaluation of haplotypic effects, either for selected polymorphisms physically close to each other or for multiple genes within the same drug-metabolism pathway.

Pseudoxanthoma elasticum: genetic variations in antioxidant genes are risk factors for early disease onset

BACKGROUND

Pseudoxanthoma elasticum (PXE) is a rare hereditary disorder characterized by progressive calcification and fragmentation of elastic fibers in connective tissues. PXE is caused by mutations in the ABCC6 gene, which encodes the membrane transporter multidrug resistance-associated protein 6. Chronic oxidative stress was recently suggested to play a crucial role in the pathogenesis of the disease. Our aim was to investigate the association of PXE with genetic variation in genes coding for antioxidant enzymes.

METHODS

We used restriction fragment length polymorphism and allele-specific PCR analyses to evaluate the distribution of single-nucleotide polymorphisms in the genes encoding catalase (CAT), superoxide dismutase 2 (SOD2), and glutathione peroxidase 1 (GPX1) in DNA samples from 117 German PXE patients and 117 healthy age- and sex-matched control individuals.

RESULTS

The investigated genetic variants had previously been shown to affect the activities of these antioxidant enzymes. We found a correlation between genotype and age of disease onset for polymorphisms in CAT (c.-262C>T), SOD2 (c.47C>T), and GPX1 (c.593C>T). Furthermore, the age of disease onset was inversely correlated with the number of mutated alleles, indicating a cumulative effect on the time of disease onset [mean (SD) age of 40.9 (13.6) years, 32.4 (16.3) years, and 25.7 (15.9) years for carriers of 0, 1-2, and >2 mutated alleles, respectively; P = 0.03].

CONCLUSION

Our findings demonstrate that increased oxidative stress due to activity-affecting polymorphisms in genes encoding antioxidant enzymes leads to earlier PXE onset.

Socioeconomic status and risk for arsenic-related skin lesions in Bangladesh

OBJECTIVES

Arsenic contamination of groundwater is a severe public health crisis in Bangladesh, where the population is exposed to arsenic in drinking water through tube wells used for groundwater collection. In this study, we explored the association between socioeconomic status and arsenic toxicity.

METHODS

We used baseline data from 11438 men and women who were recruited into the Health Effects of Arsenic Longitudinal Study (HEALS), a prospective cohort study on the health effects of arsenic exposure in Bangladesh. We conducted analyses with logistic regression and generalized estimating equations.

RESULTS

We found a strong dose-response association with all measures of arsenic exposure and skin lesions. We also found that the effect of arsenic was modified by land ownership on a multiplicative scale, with an increased risk among non-land owners associated with well water arsenic (P=.04) and urinary total arsenic concentrations (P=.03).

CONCLUSIONS

Our study provides insight into potentially modifiable host characteristics and identifies factors that may effectively target susceptible population subgroups for appropriate interventions.

Genotype-activity relationship for Mn-superoxide dismutase, glutathione peroxidase 1 and catalase in humans

OBJECTIVES

This study examined the association between genetic polymorphisms and enzyme activity for antioxidant enzymes that share a common detoxification pathway: manganese superoxide dismutase (MnSOD), glutathione peroxidase-1 (GPX1) and catalase.

METHODS

MnSOD, GPX1, and catalase activities were measured in isolated erythrocytes of 231 healthy, non-smoking student volunteers (55% women, ages 17-21, majority Asian or Caucasian). DNA from blood clots was genotyped by Taqman PCR (C47T : MnSOD and C593T : GPX1) and standard PCR (-262C>T : catalase). Associations between genotype and enzyme activity were analyzed by multiple linear regression, adjusted for baseline factors including gender and ethnicity.

RESULTS

Minor allele frequencies ranged from 13% for catalase (T) to 18% for GPX1 (T), and 33% for MnSOD(C) with significant variation between ethnicities. Median GPX1 activity was 13.2 U/g Hb with a six-fold difference between lowest and highest levels. Catalase activity ranged eight-fold (median: 86.3 k/g Hb), while median MnSOD activity was 2.8 U/mg Hb with a 56-fold range of values. MnSOD enzyme activity was 15% higher in females than males (95%CI : -1%, 32%), and 33% higher in CT or TT individuals (C47T) versus CC individuals (95%CI : 7-59%). On average, catalase activity was 18.1 k/g Hb lower for TT subjects (-262C>T) versus CC subjects (95% CI: -32.3, -4.0). All enzyme activities were correlated (r=0.3-0.4, P<0.001).

CONCLUSIONS

Interindividual variability of antioxidant enzyme activity in healthy young adults was partially explained by significant associations with three known genetic polymorphisms, and was further modified by gender and ethnicity. A substantial component of this variability may be attributable to differences in diet, environmental exposures, and additional genetic factors.

Associations between catalase phenotype and genotype: modification by epidemiologic factors

Catalase is an endogenous antioxidant enzyme that neutralizes hydrogen peroxide and is induced by oxidative challenge. A -262C --> T polymorphism in the promoter region of the gene (CAT) is associated with risk of several conditions related to oxidative stress. We sought to determine the functional effects of the CAT polymorphism on enzyme activity in erythrocytes and the potential modifying effects of demographic and lifestyle factors on genotype/phenotype relationships, using specimens and data from controls from breast and prostate cancer studies in Arkansas (n = 420). There was a dose-response reduction in catalase activity by genotype, with geometric means of 115.4 units/mg hemoglobin for those with CC genotypes, 82.1 units/mg for those with CT genotypes, and 73.5 units/mg for those with TT genotypes. Associations were only observed among Caucasians (P < 0.0001), with no effects among African Americans (P = 0.91), and were stronger among women than men, although numbers in stratified analyses were small. Differences in catalase activity by genotype were most pronounced among those in the highest tertiles of consumption of fruits and vegetables (-35%, P = 0.003), with weaker relationships among those who were lower consumers (-21.8%, P = 0.16). Among those with CC genotypes, there was no change in activity by consumption, but there were notable decreases in activity by tertiles of consumption for those with at least one T allele. These data indicate that the CAT -262C --> T polymorphism predicts a portion of catalase phenotype, which may be limited to Caucasians. Associations between genotype and phenotype were modified by dietary factors, illustrating the biochemical complexity of studies of genetic polymorphisms and disease risk.

Arsenic in the aetiology of cancer

Arsenic, one of the most significant hazards in the environment affecting millions of people around the world, is associated with several diseases including cancers of skin, lung, urinary bladder, kidney and liver. Groundwater contamination by arsenic is the main route of exposure. Inhalation of airborne arsenic or arsenic-contaminated dust is a common health problem in many ore mines. This review deals with the questions raised in the epidemiological studies such as the dose-response relationship, putative confounders and synergistic effects, and methods evaluating arsenic exposure. Furthermore, it describes the metabolic pathways of arsenic, and its biological modes of action. The role of arsenic in the development of cancer is elucidated in the context of combined epidemiological and biological studies. However, further analyses by means of molecular epidemiology are needed to improve the understanding of cancer aetiology induced by arsenic.

Effects of sodium arsenite on catalase activity, gene and protein expression in HaCaT cells

The objective of this research work is to study the effects of sodium arsenite on activity, mRNA and protein expression of catalase (CAT) in established human cell lines of keratinocytes (HaCaT). Based on the AlamarBlue assay, we found that a high level (100 micromol/l) of sodium arsenite inhibited cell viability. The reactive oxygen species (ROS) content in cells was increased in all treated cultures dose-dependently. CAT activity, mRNA expression and protein levels were decreased by 5-20 micromol/l of sodium arsenite. It is highly suggestive that CAT gene expression and protein levels are affected by arsenic.

Association of CAT polymorphisms with catalase activity and exposure to environmental oxidative stimuli

We tested the hypotheses that catalase activity is modified by CAT single nucleotide polymorphisms (SNPs) (-262;-844), and by their interactions with oxidant exposures (coal dusts, smoking), lymphotoxin alpha (LTA, NcoI) and tumor necrosis factor (TNF, -308) in 196 miners. Erythrocyte catalase, superoxide dismutase, and glutathione peroxidase activities were measured. The CAT -262 SNP was related to lower catalase activity (104, 87 and 72 k/g hemoglobin for CC, CT and TT, respectively, p < 0.0001). Regardless of CAT SNPs, the LTA NcoI but not the TNF-308 SNP was associated with catalase activity (p = 0.04 and p = 0.8). CAT -262 T carriers were less frequent in highly exposed miners (OR = 0.39 [0.20-0.78], p = 0.007). In CAT -262 T carriers only, catalase activity decreased with high dust exposure (p = 0.01). Haplotype analyses (combined CAT SNPs) confirm these results. Results show that CAT -262 and LTA NcoI SNPs, and interaction with coal dust exposure, influenced catalase activity.

Associations between breast cancer risk and the catalase genotype, fruit and vegetable consumption, and supplement use

Observed weak or null associations between fruit and vegetable intake and breast cancer risk could be due to heterogeneity in endogenous antioxidant capabilities. The authors evaluated potential relations between a functional polymorphism in catalase, an antioxidant enzyme, and breast cancer risk, particularly in relation to fruit and vegetable intake and supplement use. Women (1,008 cases and 1,056 controls) in the Long Island Breast Cancer Study Project (1996-1997) were interviewed, completed a food frequency questionnaire, and provided blood for genotyping. The high-activity catalase CC genotype was associated with an overall 17% reduction in risk of breast cancer compared with having at least one variant T allele (odds ratio = 0.83, 95% confidence interval: 0.69, 1.00). Vegetable and, particularly, fruit consumption contributed to the decreased risk associated with the catalase CC genotype. Associations were more pronounced among women who did not use vitamin supplements, with a significant multiplicative interaction (p(interaction) = 0.02) for the CC genotype and high fruit intake (odds ratio = 0.59, 95% confidence interval: 0.38, 0.89), and there was no association among supplement users. These results indicate the importance of diet, rather than supplement use, in concert with endogenous antioxidant capabilities, in the reduction of breast cancer risk. CC genotypes were prevalent in approximately 64% of controls; thus, the preventive potential for fruit consumption has widespread implications.

Cancer chemopreventive effects of Pinus Maritima bark extract on ultraviolet radiation and ultraviolet radiation-7,12,dimethylbenz(a)anthracene induced skin carcinogenesis of hairless mice

The bark extract of Pinus Maritima (PBE), a rich in phenolic acids, polyphenols and in particular flavonoids mixture, was examined for skin cancer preventive action that was evaluated in two different experimental animal tumor models induced by ultraviolet radiation (UVR) and combination of UVR with 7,12-dimethylbenz[a]anthracene. Significant decrease in the number of animals bearing tumors and the number of tumors per animal was observed in the PBE treated animals. In the same time significant increase in the viability of these animals was also observed. Furthermore, PBE delayed the appearance of tumors. These results provide strong evidence about the preventive anticancer activity of this extract on non-melanoma skin cancer and its protective effect not only from UVR, but also from more potent carcinogenic agents.

Polymorphisms in Genes Related to Oxidative Stress (MPO, MnSOD, CAT) and Survival After Treatment for Breast Cancer

The proximate cause of cancer cell death by radiation therapy and a number of therapeutic agents is through generation of reactive oxygen species, resulting in DNA damage as well as mitochondrial membrane disruption, triggering the apoptotic cascade. Because mitochondrial manganese superoxide dismutase catalyzes conversion of superoxide radicals to H2O2, with catalase neutralizing H2O2 and myeloperoxidase converting H2O2 to highly reactive hypochlorous acid, we hypothesized that gene variants could impact the efficacy of treatment for breast cancer and improve survival. Women who were treated with radiation and/or chemotherapy for incident breast cancer at the Arkansas Cancer Research Center from 1985 to 1996 were identified. DNA was extracted from paraffin-embedded normal tissue (n = 279), and MnSOD, CAT, and MPO genotypes were determined using mass spectrometry. Cox proportional hazards models were adjusted for age, race, stage with node status, and estrogen receptor and progesterone receptor status. Women who were homozygous for MPO G alleles, associated with increased transcription, had better survival (hazard ratio, 0.60; 95% confidence interval, 0.38-0.95; P = 0.03) than those with common alleles. Both CAT TT and MnSOD CC genotypes were associated with nonsignificant reduced hazard of death. When we combined genotypes associated with higher levels of reactive oxygen species for MnSOD and MPO, women with MnSOD CC and MPO GG genotypes had a 3-fold decrease in hazard of death (hazard ratio, 0.33; 95% confidence interval, 0.13-0.80; P = 0.01). These data indicate that gene variants that impact oxidative stress modify prognosis after treatment for breast cancer.

Gene-nutrient interactions in cancer etiology

Relationships between dietary components and cancer risk are often unclear, and the results from epidemiologic studies are inconsistent. While some inconsistencies could be due to study design issues, we propose that genetic heterogeneity of study populations could mask associations. In this report, we review the literature regarding meat consumption and risk of colon, breast, and prostate cancers, particularly in relation to phenotypes and genotypes for enzymes that metabolize food-borne promutagens. The role of consumption of fruits and vegetables, as well as the role of genetic variants in oxidative stress genes, in the risk of breast cancer are also discussed.