Myeloperoxidase -463 (G-->A) polymorphism associated with lower risk of lung cancer

The Genetic Changes of Hepatoblastoma

Hepatoblastoma is the most common malignant liver cancer in childhood. The etiology of hepatoblastoma remains obscure. Hepatoblastoma is closely related to genetic syndromes, hinting that hepatoblastoma is a genetic predisposition disease. However, no precise exposures or genetic events are reported to hepatoblastoma occurrence. During the past decade, significant advances have been made in the understanding of etiology leading to hepatoblastoma, and several important genetic events that appear to be important for the development and progression of this tumor have been identified. Advances in our understanding of the genetic changes that underlie hepatoblastoma may translate into better patient outcomes. Single nucleotide polymorphisms (SNPs) have been generally applied in the research of etiology's exploration, disease treatment, and prognosis assessment. Here, we reviewed and discussed the molecular epidemiology, especially SNPs progresses in hepatoblastoma, to provide references for future studies and promote the study of hepatoblastoma's etiology.

Association between MPO-463G > A polymorphism and cancer risk: evidence from 60 case-control studies

BACKGROUND

Though a number of studies have been conducted to explore the association between myeloperoxidase (MPO)-463G > A polymorphism and cancer risk, the results remain inconsistent. Therefore, we performed a meta-analysis to derive a more systematic estimation of this relationship.

METHOD

Relevant studies were searched by PubMed, EMBASE, CNKI, Google Scholar, Ovid, and Cochrane library prior to December 2015. The strength of the association between MPO-463G > A polymorphism and cancer risk was estimated by odds ratios (OR) with 95% confidence interval (95%CI). Cumulative analysis was used to evaluate the stability of results through time.

RESULTS

The current analysis consisted of 16,858 cases and 21,756 controls from 60 studies. Pooled results showed that MPO-463G > A polymorphism were associated with the overall decreased cancer susceptibility in all the genetic models included in this study (additive model: OR = 0.84, 95%CI = 0.76-0.94; allele genetic model: OR = 0.90, 95%CI = 0.840-0.954; recessive genetic model: OR = 0.89, 95%CI = 0.83-0.95). However, in the stratified analysis of cancer type, the significant results were only found in lung cancer (dominant model: OR = 0.93, 95%CI = 0.87-0.99) and digestive system cancer groups (dominant model: OR = 0.67 0.53-0.84; allele frequency model = 0.71, 95%CI = 0.57-0.87), but not in the blood system cancer or breast cancer group. When we further stratified the digestive system cancer group into digestive tract and digestive gland cancer groups, results showed a significant association between allele A of MPO-463G > A and digestive gland cancer in all the genetic models (allele frequency model: OR = 0.63, 95%CI = 0.40-0.99; additive model: OR = 0.41, 95%CI = 0.23-0.73; recessive model: OR = 0.51, 95%CI = 0.29-0.89; dominant model: OR = 0.58, 95%CI = 0.35-0.96), digestive tract cancers in allele frequency model (OR = 0.75, 95%CI = 0.59-0.95), and dominant model (OR = 0.72, 95%CI = 0.56-0.92). When stratified by ethnicity, results demonstrated that the genotype A might be a protect factor for both Caucasians and Asians. In group analysis according to source of controls, significant results were found in population from hospital in all the genetic models. In cumulative analysis, result of allele contrast showed a declining trend and increasingly narrower 95% overall, while the inclination toward non-significant association with lung cancer risk.

CONCLUSIONS

This meta-analysis suggested that MPO-463G > A polymorphism was associated with the overall reduced cancer susceptibility significantly. It might be a more reliable predictor of digestive system cancer instead of lung cancer, blood system cancer, and breast cancer. In cumulative analysis, the stable trend indicated that evidence was sufficient to show the association between MPO-463G > A polymorphism and cancer risk.

HapMap-based study on the association between MPO and GSTP1 gene polymorphisms and lung cancer susceptibility in Chinese Han population

AIM

Myeloperoxidase (MPO) and glutathione S-transferase pi 1 (GSTP1) are important carcinogen-metabolizing enzymes. The aim of this study was to investigate the association between the common polymorphisms of MPO and GSTP1 genes and lung cancer risk in Chinese Han population.

METHODS

A total of 266 subjects with lung cancer and 307 controls without personal history of the disease were recruited in this case control study. The tagSNPs approach was used to assess the common polymorphisms of MOP and GSTP1 genes and lung cancer risk according to the disequilibrium information from the HapMap project. The tagSNP rs7208693 was selected as the polymorphism site for MPO, while the haplotype-tagging SNPs rs1695, rs4891, rs762803 and rs749174 were selected as the polymorphism sites for GSTP1. The gene polymorphisms were confirmed using real-time PCR, cloning and sequencing.

RESULTS

The four GSTP1 haplotype-tagging SNPs rs1695, rs4891, rs762803 and rs749174, but not the MPO tagSNP rs7208693, exhibited an association with lung cancer susceptibility in smokers in the overall population and in the studied subgroups. When Phase 2 software was used to reconstruct the haplotype for GSTP1, the haplotype CACA (rs749174+rs1695 + rs762803+rs4891) exhibited an increased risk of lung cancer among smokers (adjust odds ratio 1.53; 95%CI 1.04-2.25, P=0.033). Furthermore, diplotype analyses demonstrated that the significant association between the risk haplotype and lung cancer. The risk haplotypes co-segregated with one or more biologically functional polymorphisms and corresponded to a recessive inheritance model.

CONCLUSION

The common polymorphisms of the GSTP1 gene may be the candidates for SNP markers for lung cancer susceptibility in Chinese Han population.

An association between MPO -463 G/A polymorphism and type 2 diabetes

Myeloperoxidase (MPO) is an enzyme which is a member of the haem-peroxidase superfamily and plays a role in production of reactive oxygen species. The most common polymorphism in the promoter region of MPO gene is -463 G/A. It was shown that carrying the GG genotype means increased activity of the gene approximately 2-3-fold compared to GA and AA genotypes. It was found that hyperglycaemia, modified oxidized proteins and increased advanced glycosylated end products (AGE) are related to oxidative stress in diabetes. Under the hyperglycaemic conditions, production of reactive oxygen radical is elevated in smooth muscle endothelial cells, mesengial and tubular endothelial cells. Especially, elevated lipid oxidation plays an important role in pathogenesis of diabetic complications such as cardiovascular complications. We examined the MPO -463 G/A polymorphism by using the PCR-RFLP method in 145 type 2 diabetic patients and 151 healthy controls. We observed that the AA genotype and A allele were protective variants against type 2 diabetes and the GG genotype was a risk factor for diabetes. While we studied the relationship between genotypes and biochemical parameters, we found that patients with the A allele had decreased serum cholesterol, triglyceride, VLDL levels and body mass index. We suggest that the MPO gene has an important role in pathogenesis of type 2 diabetes because of the increased frequency of GG genotype, which is related to increased activity and oxidant capacity of MPO in the patients.

Association between MPO 463G>A polymorphism and risk of lung cancer: a meta-analysis

There is a possible association between myeloperoxidase (MPO) 463G>A polymorphism and risk of lung cancer, but previous studies report conflicting results. We performed a meta-analysis of available molecular epidemiologic studies to comprehensively assess the association between MPO 463G>A polymorphism and risk of lung cancer. A systemic literature search was performed in Pubmed, Embase, and Wanfang databases for molecular epidemiologic studies on the association MPO 463G>A polymorphism and risk of lung cancer on March 16, 2013. The pooled odds ratios (ORs) with their 95% confidence interval (95% CI) were calculated to assess the strength of the association. Twenty-six individual case-control studies with a total of 18,433 subjects (7,752 cases and 10,681 controls) were finally included into the meta-analysis. Overall, MPO 463G>A polymorphism was significantly associated with decreased risk of lung cancer under two main genetic comparison models (for A versus G, OR = 0.91, 95 % CI 0.83-0.99, P = 0.035; for AG/AA versus GG, OR = 0.90, 95% CI 0.81-0.99, P = 0.029). Meta-analysis of studies with high quality also showed that MPO 463G>A polymorphism was significantly associated with decreased risk of lung cancer under two main genetic comparison models (for A versus G, OR = 0.91, 95% CI 0.83-0.99, P = 0.035; for AG/AA versus GG, OR = 0.90, 95% CI 0.80-0.99, P = 0.048). Subgroup analysis by ethnicity further showed that there was a significant association between MPO 463G>A polymorphism and decreased risk of lung cancer in Caucasians but not in Asians. The meta-analysis suggests that MPO 463G>A polymorphism is associated with decreased risk of lung cancer, especially in Caucasians.

Association between myeloperoxidase G-463A polymorphism and lung cancer risk

Many epidemiologic studies have investigated the association between myeloperoxidase (MPO) G-463A polymorphism and lung cancer risk, but the results were controversial. We performed a meta-analysis of 25 studies on MPO polymorphism and lung cancer risk published before July 2013. The allele of A was found to be associated with decreased risk of lung cancer compared with G allele (OR, 0.90; 95% CI, 0.82-0.98) in the general population. The significant association remained in the comparison between AA + AG and GG (OR, 0.92; 95% CI, 0.87-0.98). When it was stratified according to Asian population, the association between MPO polymorphism and lung cancer risk was further strengthened. However, no associations were found in the Caucasian population. This meta-analysis has demonstrated that MPO polymorphism might contribute to individual's susceptibility to lung cancer in Asian population. Caucasian authors could re-investigate the association between MPO polymorphism and lung cancer risk with more specific participants. Future studies focusing on interactions between combined genes and environmental risk factors are warranted.

The MPO-463G>A polymorphism and lung cancer risk: a meta-analysis based on 22 case-control studies

Background

Myeloperoxidase (MPO) is an endogenous oxidant enzyme that produces reactive oxygen species (ROS) and may be involved in lung carcinogenesis. The MPO−463G>A polymorphism influences MPO transcription and has been associated with lung cancer susceptibility. However, the association between the MPO−463G>A polymorphism and lung cancer risk remains controversial.

Method

To investigate the effect of this polymorphism on lung cancer susceptibility, we performed a meta-analysis based on 22 published case–control studies including 7,520 patients with lung cancer and 8,600 controls. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association.

Results

Overall, there was no evidence for significant association between MPO−463G>A polymorphism and lung cancer susceptibility (for AA versus GG: OR = 0.91, 95%CI = 0.67–1.24; for GA versus GG: OR = 0.87, 95% CI = 0.78–0.98; for AA/GA versus GG: OR = 0.90, 95% CI = 0.80–1.01; for AA versus GA/GG: OR = 0.96, 95% CI = 0.72–1.28). In the stratified analyses by ethnicity, source of controls and smoking status, we also did not find any significant association between them.

Conclusions

In summary, this meta-analysis suggests MPO−463G>A polymorphism may not be a risk factor for developing lung cancer. However, further prospective well-designed population-based studies with larger sample size are expected to validate the results.

Common genetic variants in the myeloperoxidase and paraoxonase genes and the related cancer risk: a review

Modern approaches in health care are moving toward the model of "personalized medicine." Today, current research in molecular biology and medicine is focused on developing genomic markers with predictive, therapeutic, and prognostic significance. One of the most widespread and significant genomic markers is the single nucleotide polymorphism (SNP), which represents a variation in DNA sequence when a single nucleotide differs between members of a biological species or paired chromosomes in an individual. Antioxidant defense enzymes break down dangerous reactive compounds, called reactive oxygen species, and prevent DNA strand from carcinogen-specific mutations. It is well known that inherited variations in genes that encode antioxidant defense enzymes may modulate individual susceptibility to cancer. In our previous study we have determined the predictive significance of several SNPs of superoxide dismutase (SOD) and glutathione peroxidase gene families in the context of cancer risk. The present review includes a summary and discussion of the current findings evaluating the role of SNPs of the myeloperoxidase (MPO) and paraoxanase (PON) genes in cancer occurrence and development. We suggest that rs2333227 (MPO_ -463G/A) and rs854560 polymorphisms have a great predictive significance; they could probably be utilized as cancer predictors in the future. Also, we recommend further in-depth research for rs11079344 (MPO), rs8178406 (MPO), rs2243828 (MPO), rs662 (PON1), rs705379 (PON1), and PON1_304A/G polymorphisms. These SNPs may become significant cancer-associated biomarkers.

The MPO -463G>A polymorphism and cancer risk: a meta-analysis based on 43 case-control studies

Myeloperoxidase (MPO) is an endogenous oxidant enzyme that generates reactive oxygen species and plays an important role in the aetiology of cancer. The MPO -463G>A polymorphism influences MPO transcription and has been implicated in cancer risk. However, results from published studies on the association between the MPO -463G>A polymorphism and risk of cancer are conflicting. To derive a more precise estimation of association between the MPO -463G>A polymorphism and risk of cancer, we performed a meta-analysis based on 43 case-control studies, including a total of 14 171 cancer cases and 17 319 controls. We used odds ratios (ORs) with 95% confidence intervals (CIs) to assess the strength of the association. Overall, individuals with the -463A allele had a 0.93-fold lower cancer risk in a dominant model (OR = 0.93, 95% CI = 0.87-1.00). In the stratified analyses, we observed a similar association in European populations (heterozygote comparison: OR = 0.90, 95% CI = 0.82-0.99) and hospital-based studies (dominant model: OR = 0.88, 95% CI = 0.79-0.99). When stratified by cancer type, however, no significant association was found. The results suggested that the MPO -463A allele does not contribute to the development of cancer. Additional well-designed large studies are required to validate these findings in different populations.

[A meta analysis on the relationship between myeloperoxidase G-463A genetic polymorphisms and lung cancer susceptibility]

BACKGROUND AND OBJECTIVE

The relationship between myeloperoxidase G-463A genetic polymorphisms and lung cancer susceptibility has been studied extensively. However, the outcomes are not consistent. The aim of this study is to evaluate the relationship between myeloperoxidase genetic polymorphisms and lung cancer susceptibility by meta analysis.

METHODS

Documents published were retrieved through databases associated with the study. Taking into account the possibilities of heterogeneity of the studies, a statistical test for heterngeneity was performed. The odds ratio and 95% CI were used to evaluate the risks. The meta analysis was applied with RevMan software 4.2, and the forest plot and funnel plot of meta analysis were worked out.

RESULTS

A total of 5 381 cases and 5 827 controls from studies for Caucasian and a total of 1 558 cases and 1 755 controls from studies for East Asians were included. For Caucasian the pooled OR was 0.91 (95% CI: 0.81-1.02); For East Asians, the pooled OR is 0.83 (95% CI: 0.63-1.09). Publication bias exits in the study for Caucasian, but not for East Asians.

CONCLUSION

The results of this study indicated that the polymorphism of myeloperoxidase G-463A was not significantly associated with the lung cancer risk for Caucasian or East Asians. However, further studies for the East Asians is needed for the few subjects.

Apoptosis-inducing high (.)NO concentrations are not sustained either in nascent or in developed cancers

Nitric oxide ((.)NO) induces apoptosis at high concentrations by S-nitrosating proteins such as glyceraldehyde-3-phosphate dehydrogenase. This literature analysis revealed that failure to sustain high (.)NO concentrations is common to all cancers. In cervical, gastric, colorectal, breast, and lung cancer, the cause of this failure is the inadequate expression of inducible nitric oxide synthase (iNOS), resulting from the inhibition of iNOS expression by TGF-beta1 at the mRNA level. In bladder, renal, and prostate cancer, the reason for the insufficient (.)NO levels is the depletion of arginine, resulting from arginase overexpression. Arginase competes with iNOS for arginine, catalyzing its hydrolysis to ornithine and urea. In gliomas and ovarian sarcomas, low (.)NO levels are caused by inhibition of iNOS by N-chlorotaurine, produced by infiltrating neutrophils. Stimulated neutrophils express myeloperoxidase, catalyzing H2O2 oxidation of Cl- to HOCl, which N-chlorinates taurine at its concentration of 19 mM in neutrophils. In squamous cell carcinomas of the skin, ovarian cancers, lymphomas, Hodgkin's disease, and breast cancers, low (.)NO concentrations arise from the inhibition of iNOS by N-bromotaurine, produced by eosinophil-peroxidase-expressing infiltrating eosinophils. Eosinophil peroxidase catalyzes the H2O2 oxidation of Br- to HOBr, which N-brominates taurine to N-bromotaurine at its concentration of 15 mM in eosinophils. In microvascularized tumors, the (.)NO concentration is further depleted; (.)NO is rapidly consumed by red blood cells (RBCs) through S-nitrosation of RBC glutathione and hemoglobin, and by oxidation to nitrate by RBC oxyhemoglobin. Angiogenesis-inhibiting antibodies are currently used to treat cancers; their mode of action is not, as previously thought, reduction of the tumor O2 or nutrient supply. They actually decrease the loss of (.)NO to RBCs.

Myeloperoxidase and superoxide dismutase polymorphisms are associated with an increased risk of developing pancreatic adenocarcinoma

BACKGROUND

Pancreatic cancer risk has been linked to chronic pancreatitis and periodontitis, suggesting a role for inflammation in disease etiology. Myeloperoxidase (MPO) and superoxide dismutase (SOD2) are enzymes that regulate reactive oxygen species and contain recognized single nucleotide polymorphisms (SNPs) that confer altered enzyme activity.

METHODS

One hundred twenty-two patients with pancreatic cancer and 331 age- and sex-matched controls were analyzed for polymorphisms of the MPO - guanine 463 adenine (-G463A) and the SOD2 alanine (Ala)-to-valine (Val) polymorphism at codon 16 (Ala16Val) genes. Cases and controls were analyzed for associations between these polymorphisms, adjusting for sex, age, history of alcohol use and smoking history.

RESULTS

The variant A allele of MPO -G463A was associated with a lower risk of pancreatic cancer (adjusted odds ratio [OR] for pancreatic cancer, 0.57; 95% confidence interval [95% CI], 0.4-0.9; P = .02). The SOD2 homozygous variant genotype (Val/Val) was associated with a greater risk of pancreatic cancer (adjusted OR, 1.96; 95% CI, 1.0-3.8; P = .04). Compared with individuals who carried both low-risk alleles (A/- and Ala/-), significantly more cases than controls carried both high-risk genotypes (G/G and Val/Val; adjusted OR, 4.31; 95% CI, 1.8-10; P = .001), or 1 high-risk genotype (adjusted OR, 1.96; 95% CI, 1.1-3.4; P = .01).

CONCLUSIONS

Polymorphisms of the inflammatory pathway genes MPO -G463A and SOD2 Ala16Val are associated with elevated pancreatic cancer risk. Oxidative stress may play an important role in pancreatic cancer carcinogenesis.

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.

Polymorphism of selected enzymes involved in detoxification and biotransformation in relation to lung cancer

Available data indicate that there are significant differences in individual susceptibility to lung cancer within the human population. It is believed to be underlie by inherited genetic predispositions related to the genetic polymorphism of several enzymes involved in the detoxification and xenobiotic metabolism. In this review, we collect and discuss the evidence reported up to date on the association between lung cancer and genetic polymorphism of cytochromes P450, N-acetyltransferase, glutathione S-transferases, microsomal epoxide hydrolase, NAD(P)H:quinone oxidoreductase, myeloperoxidase and glutathione peroxidase. All these genes might appear to be candidates for lung cancer susceptibility genes, nevertheless, the present state of the art still offers only a limited explanation of the link between such polymorphisms and increased risk of lung cancer.

Factores etiológicos del cáncer de pulmón: fumador activo, fumador pasivo, carcinógenos medioambientales y factores genéticos

Every year, in Spain 18,000 new cases of lung cancer (LC) are diagnosed. Approximately, 80-90% LC in men and women are directly attributable to tobacco abuse. Cigarette smoke contains over 300 chemicals, 40 of which are known to be potent carcinogens. In the last decade, as in Spain, prevalence of smoking in women has generally increased in the European Union. LC risk can be substantially reduced after smoking cessation, yet never reaches baseline. On the other hand, environmental tobacco smoke exposure (passive smoking) in nonsmokers appears to have a significantly increased risk of LC. An updated of etiology factors of LC, risk related to duration as well as intensity of smoking, relationship between environmental tobacco smoke exposure and LC risk, genetic predisposition and a variety of occupational and environmental exposures implicated as potential risk factors for the development of LC will be reviewed here.

Myeloperoxidase G-463A polymorphism and lung cancer: a HuGE genetic susceptibility to environmental carcinogens pooled analysis

Myeloperoxidase is a phase I metabolic enzyme that converts the metabolites of benzo[a]pyrene from tobacco smoke into highly reactive epoxides. A polymorphism in the promoter region of myeloperoxidase (463G-->A) has been found to be inversely associated with lung cancer; differences in the association with age and gender have been suggested. We conducted a pooled analysis of individual data from 10 studies (3688 cases and 3874 controls) from the Genetic Susceptibility to Environmental Carcinogens database. The odds ratio for lung cancer was 0.88 (95% confidence interval: 0.80-0.97) for the AG variant of myeloperoxidase G-463A polymorphism, and 0.71 (95% confidence interval: 0.57-0.88) for the AA variant after adjusting for smoking, age, gender, and ethnicity. The inverse association between lung cancer and myeloperoxidase G-463A polymorphism was equally found in males and females (odds ratio for the AA genotype 0.73 [95% confidence interval: 0.56-0.96] and 0.67 [95% confidence interval: 0.46-0.98], respectively), without differences in the association according to age in the two genders. The myeloperoxidase G-463A polymorphism was significantly protective in "ever" smokers but not in "never" smokers. Myeloperoxidase is a key enzyme in tobacco-induced carcinogenesis.

Biosynthesis, processing, and sorting of human myeloperoxidase

Exclusively synthesized by normal neutrophil and monocyte precursor cells, myeloperoxidase (MPO) functions not only in host defense by mediating efficient microbial killing but also can contribute to progressive tissue damage in chronic inflammatory states such as atherosclerosis. The biosynthetic precursor, apoproMPO, is processed slowly in the ER, undergoing cotranslational N-glycosylation, transient interactions with the molecular chaperones calreticulin and calnexin, and heme incorporation to generate enzymatically active proMPO that is competent for export into the Golgi. After exiting the Golgi the propeptide is removed prior to final proteolytic processing in azurophil granules, resulting in formation of a symmetric MPO homodimer linked by a disulfide bond. Some proMPO escapes granule targeting and becomes constitutively secreted to the extracellular environment. Although the precise mechanism is unknown, the pro-segment is required for normal processing and targeting, as propeptide-deleted MPO precursor is either degraded or constitutively secreted. Characterizing the molecular consequences of naturally occurring mutations that cause inherited MPO deficiency provides unique insight into the structural determinants of MPO involved in biosynthesis, processing and targeting.

After Helsinki: a multidisciplinary review of the relationship between asbestos exposure and lung cancer, with emphasis on studies published during 1997-2004

Despite an extensive literature, the relationship between asbestos exposure and lung cancer remains the subject of controversy, related to the fact that most asbestos-associated lung cancers occur in those who are also cigarette smokers: because smoking represents the strongest identifiable lung cancer risk factor among many others, and lung cancer is not uncommon across industrialised societies, analysis of the combined (synergistic) effects of smoking and asbestos on lung cancer risk is a more complex exercise than the relationship between asbestos inhalation and mesothelioma. As a follow-on from previous reviews of prevailing evidence, this review critically evaluates more recent studies on this relationship--concentrating on those published between 1997 and 2004--including lung cancer to mesothelioma ratios, the interactive effects of cigarette smoke and asbestos in combination, and the cumulative exposure model for lung cancer induction as set forth in The Helsinki Criteria and The AWARD Criteria (as opposed to the asbestosis-->cancer model), together with discussion of differential genetic susceptibility/resistance factors for lung carcinogenesis by both cigarette smoke and asbestos. The authors conclude that: (i) the prevailing evidence strongly supports the cumulative exposure model; (ii) the criteria for probabilistic attribution of lung cancer to mixed asbestos exposures as a consequence of the production and end-use of asbestos-containing products such as insulation and asbestos-cement building materials--as embodied in The Helsinki and AWARD Criteria--conform to, and are further consolidated by, the new evidence discussed in this review; (iii) different attribution criteria (e.g., greater cumulative exposures) are appropriate for chrysotile mining/milling and perhaps for other chrysotile-only exposures, such as friction products manufacture, than for amphibole-only exposures or mixed asbestos exposures; and (iv) emerging evidence on genetic susceptibility/resistance factors for lung cancer risk as a consequence of cigarette smoking, and potentially also asbestos exposure, suggests that genotypic variation may represent an additional confounding factor potentially affecting the strength of association and hence the probability of causal contribution in the individual subject, but at present there is insufficient evidence to draw any meaningful conclusions concerning variation in asbestos-mediated lung cancer risk relative to such resistance/susceptibility factors.

Myeloperoxidase: friend and foe

Neutrophilic polymorphonuclear leukocytes (neutrophils) are highly specialized for their primary function, the phagocytosis and destruction of microorganisms. When coated with opsonins (generally complement and/or antibody), microorganisms bind to specific receptors on the surface of the phagocyte and invagination of the cell membrane occurs with the incorporation of the microorganism into an intracellular phagosome. There follows a burst of oxygen consumption, and much, if not all, of the extra oxygen consumed is converted to highly reactive oxygen species. In addition, the cytoplasmic granules discharge their contents into the phagosome, and death of the ingested microorganism soon follows. Among the antimicrobial systems formed in the phagosome is one consisting of myeloperoxidase (MPO), released into the phagosome during the degranulation process, hydrogen peroxide (H2O2), formed by the respiratory burst and a halide, particularly chloride. The initial product of the MPO-H2O2-chloride system is hypochlorous acid, and subsequent formation of chlorine, chloramines, hydroxyl radicals, singlet oxygen, and ozone has been proposed. These same toxic agents can be released to the outside of the cell, where they may attack normal tissue and thus contribute to the pathogenesis of disease. This review will consider the potential sources of H2O2 for the MPO-H2O2-halide system; the toxic products of the MPO system; the evidence for MPO involvement in the microbicidal activity of neutrophils; the involvement of MPO-independent antimicrobial systems; and the role of the MPO system in tissue injury. It is concluded that the MPO system plays an important role in the microbicidal activity of phagocytes.

Genotoxicity of tobacco smoke and tobacco smoke condensate: a review

This report reviews the literature on the genotoxicity of mainstream tobacco smoke and cigarette smoke condensate (CSC) published since 1985. CSC is genotoxic in nearly all systems in which it has been tested, with the base/neutral fractions being the most mutagenic. In rodents, cigarette smoke induces sister chromatid exchanges (SCEs) and micronuclei in bone marrow and lung cells. In humans, newborns of smoking mothers have elevated frequencies of HPRT mutants, translocations, and DNA strand breaks. Sperm of smokers have elevated frequencies of aneuploidy, DNA adducts, strand breaks, and oxidative damage. Smoking also produces mutagenic cervical mucus, micronuclei in cervical epithelial cells, and genotoxic amniotic fluid. These data suggest that tobacco smoke may be a human germ-cell mutagen. Tobacco smoke produces mutagenic urine, and it is a human somatic-cell mutagen, producing HPRT mutations, SCEs, microsatellite instability, and DNA damage in a variety of tissues. Of the 11 organ sites at which smoking causes cancer in humans, smoking-associated genotoxic effects have been found in all eight that have been examined thus far: oral/nasal, esophagus, pharynx/larynx, lung, pancreas, myeoloid organs, bladder/ureter, uterine cervix. Lung tumors of smokers contain a high frequency and unique spectrum of TP53 and KRAS mutations, reflective of the PAH (and possibly other) compounds in the smoke. Further studies are needed to clarify the modulation of the genotoxicity of tobacco smoke by various genetic polymorphisms. These data support a model of tobacco smoke carcinogenesis in which the components of tobacco smoke induce mutations that accumulate in a field of tissue that, through selection, drive the carcinogenic process. Most of the data reviewed here are from studies of human smokers. Thus, their relevance to humans cannot be denied, and their explanatory powers not easily dismissed. Tobacco smoke is now the most extreme example of a systemic human mutagen.

MPO and SOD2 polymorphisms, gender, and the risk of non-small cell lung carcinoma

Manganese superoxide dismutase (SOD2) and myeloperoxidase (MPO) are polymorphic enzymes involved in reactive oxidative species metabolism. In this case-control study (830 non-small cell lung carcinoma (NSCLC) patients; 1119 controls) we evaluated whether the MPO -G463A polymorphism (associated with a novel estrogen receptor binding site) modifies the association between the SOD2 Ala16Val polymorphism and NSCLC risk differently by gender. For women carrying the MPO variant genotypes, the adjusted odds ratio of the SOD2 polymorphism (Val/Val vs. Ala/Ala) was 3.26 (95% CI, 1.55-6.83). No associations were found in men or in women carrying the MPO GG wildtype genotype.

Myeloperoxidase (MPO) −463G→A Reduces MPO Activity and DNA Adduct Levels in Bronchoalveolar Lavages of Smokers

The myeloperoxidase (MPO) −463G→A genetic polymorphism is associated with a reduced risk for lung cancer, but the underlying mechanism is not yet elucidated. Therefore, the impact of this polymorphism on MPO activity and lipophilic DNA adducts was studied in respectively bronchoalveolar lavage (BAL) fluid and cells, from 106 smoking Caucasian lung patients. MPO activity was determined spectrophotometrically, aromatic DNA adducts by 32P-postlabeling and MPO genotypes by RFLP analysis. Frequencies of MPO −463AA (13%), MPO −463AG (36%), and MPO −463GG (51%) were in line with earlier observations. MPO activity/neutrophil was lower in MPO −463AA (median 0.04 pU/cell) than in MPO −463AG (median 0.07 pU/cell) and MPO −463GG (median 0.14 pU/cell; P = 0.059) individuals. DNA adducts in BAL cells were measured in 11 MPO −463AA subjects and equal numbers of MPO −463AG and MPO −463GG subjects matched for smoking, age, gender, and clinical diagnosis. DNA adduct levels in MPO −463AA individuals (median 0.62 adducts/108 nucleotides) were lower than in MPO −463AG (median 1.51 adducts/108 nucleotides) and MPO −463GG (median 3.26 adducts/108 nucleotides; P = 0.003) subjects. Overall, no significant correlation was observed between amount of inhaled tar/day and DNA adduct levels. However, correlations improved considerably on grouping according to the MPO genotype; MPO −463AA subjects were the least responsive (R2 = 0.73, slope = 0.4, P = 0.01) followed by MPO −463AG subjects (R2 = 0.70, slope = 1.3, P = 0.01) and MPO −463GG patients (R2 = 0.67, slope = 2.8, P = 0.02). These data demonstrate that MPO −463AA/AG genotypes are associated with (a) reduced MPO activity in BAL fluid and (b) reduced smoking-related DNA adduct levels in BAL cells in a gene-dose manner. These data provide a plausible biological explanation for the reduced risk for lung cancer as observed in MPO −463AA/AG compared with MPO −463GG subjects.

Combined effect of MPO, GSTM1 and GSTT1 polymorphisms on chromosome aberrations and lung cancer risk

The role of myeloperoxidase (MPO), and glutathione S-transferase mu and theta (GSTM1 and GSTT1) genetic polymorphisms on lung cancer risk was investigated in 110 Caucasian patients and 119 matched controls. Single genotype variants were not significantly associated with lung cancer risk. However, inheritance of the combined GSTM1 and GSTT1 null genotypes showed a significant increase in risk (crude OR = 2.32, 95% CI = 1.01-6.04). Based on adjustment by age, gender and smoking history, the MPO GA interacted with the presence of GSTM1 and GSTT1 genotypes to significantly reduce the risk (OR = 0.17, 95% CI = 0.03-0.98). From the chromosome aberration (CA) study in a subgroup of 79 patients and 69 matched controls, patients had significantly more CA than the controls. Among the patients, GSTM1 null was associated with a significant increase of CA and MPO AA was associated with a significant decrease of CA compared to their respective wild-type genotypes. After stratifying by smoking history (< or = and > 40 pack-years) and genotype, patients still had significantly more CA than the respective controls in most genotype categories. This indicates that the patients had additional contributing factors such as other susceptibility genes and/or different styles of smoking compared with the controls. In conclusion, our study indicates that CA is a useful biomarker to show the functional characteristics of genotypes and the interactive effects from combined genotypes. Therefore, our study strengthens the combined use of genotype and biomarkers for genetic susceptibility to environmental cancer.

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

Chronic exposure to inorganic arsenic is known to cause non-melanocytic skin and internal cancers in humans. We examined whether genetic susceptibility, as determined by single nucleotide polymorphisms -463G-->A and -262C-->T in the oxidative stress genes myeloperoxidase (MPO) and catalase (CAT), respectively, are associated with the risk of arsenic-induced hyperkeratotic skin lesions-precursors of skin cancer-in a case-control study in Bangladesh. Carriers of the susceptible MPO and CAT genotypes were at elevated risk (OR 2.1 and 95% CI 0.7-6.2 for MPO; OR 1.9 and 95% CI 0.8-4.7 for CAT) of hyperkeratosis after adjustment for arsenic exposure and other covariates. Subjects carrying the high-risk MPO genotype and with high arsenic exposure were at almost six times (OR 5.8; 95% CI 1.1-30.1) elevated risk of developing hyperkeratosis as compared to those carrying the low-risk genotype and with low arsenic exposure. Similarly, highly exposed subjects carrying the high-risk CAT genotype were at more than four times (OR 4.6; 95% CI 1.4-15.6) elevated risk of developing hyperkeratosis as compared to those carrying the low-risk genotype and with low arsenic exposure. Our findings, although based on small numbers, suggest that the oxidative stress genes MPO and CAT may influence the risk of arsenic-induced premalignant hyperkeratotic skin lesions.

Myeloperoxidase (MPO) genotype and lung cancer histologic types: the MPO -463 A allele is associated with reduced risk for small cell lung cancer in smokers

MPO participates in the metabolic activation of tobacco carcinogens such as PAHs. A frequent MPO -463 G-->A polymorphism in the promoter region reduces MPO transcription and has been correlated with >4-fold lower benzo[a]pyrene-DNA adduct levels in the skin of coal tar-treated patients. Four of 7 case-control studies found significantly reduced lung cancer risk associated with the A allele. Due to their different etiologies, we examined whether the MPO genotype affects histologic lung cancer types differentially. A case-control study was conducted in 625 ever-smoking lung cancer patients, including 228 adenocarcinomas, 224 SCCs, 135 SCLCs and 340 ever-smoking hospital controls. MPO genotyping was performed by capillary PCR followed by fluorescence-based melting curve analysis. Combining the MPO -463 (G/A+A/A) genotypes, a protective effect approaching significance (OR = 0.75, 95% CI 0.55-1.01) was observed when comparing all lung cancer cases to controls. Among histologic types of lung cancer, a weak protective effect was found for both adenocarcinoma (OR = 0.81, CI 0.55-1.19) and SCC (OR = 0.82, CI 0.56-1.21); a stronger and significant effect was found for SCLC (OR = 0.58, CI 0.36-0.95; p = 0.029). Our results also suggest that the MPO genotype varies among inflammatory nonmalignant lung diseases. In conclusion, our results emphasize the need for a separate analysis of lung cancer histologic types and an adjustment for inflammatory nonmalignant lung diseases in future MPO-related studies. We confirm that the MPO -463 A variant affords a protective effect against lung cancer risk in smokers, which was strongest for SCLC patients.

Genetic polymorphism in myeloperoxidase but not GSTM1 is associated with risk of lung squamous cell carcinoma in a Chinese population

Myeloperoxidase (MPO), an enzyme derived from neutrophils, metabolically activates a wide range of carcinogens, whereas glutathione S-transferase M1 (GSTM1) detoxifies various electrophilic metabolites. A -463G-->A polymorphism in the promoter region of the MPO gene diminishes the expression of MPO and has been consistently shown to be associated with reduced risk of lung cancer in different ethnic populations. In our study, we have assessed the role of this polymorphism in lung cancer risk in a Chinese population. Genotypes of MPO and GSTM1 were determined by PCR-SSCP and multiplex PCR in 314 patients with lung cancer and 320 frequency-matched controls. The allele frequency for MPO -463A was found to be 0.155 in controls and 0.114 in cases. Subjects with the MPO -463GG genotype were at an increased risk of squamous cell carcinoma (SCC) of the lung compared to those having at least one -463A variant allele (adjusted odds ratio [OR] 2.35; 95% confidence interval [CI] 1.40-3.94). Stratified analysis suggested an interaction between heavy smoking (> or =26 pack-years) and the MPO-463GG genotype. The adjusted OR of lung SCC for those having MPO-463GG genotype and smoked > or =26 pack-years was 20.50 (95% CI 5.58-75.33) compared to 6.22 (95% CI 1.72-22.47) for those smoked > or =26 pack-years but having at least one variant A allele (p = 0.023, test for homogeneity). This effect of the MPO polymorphism was not observed in lung adenocarcinoma. GSTM1 deletion was quite common in both controls (49.4%) and cases (50.3%) but was not associated with risk of lung cancer alone or in combination with the MPO polymorphism. Our results confirm the previous reports showing that the variant A allele of MPO has a protective effect against risk of lung cancer.

DNA adduct burden and tobacco carcinogenesis

DNA adducts associated with tobacco smoking could provide a marker of biologically effective dose of tobacco carcinogens and improve individual cancer risk prediction. A significant number of clinical and epidemiologic studies have reported associations of increased DNA adduct levels with the occurrence of the prevalent tobacco related cancers including cancer of the lung, head and neck, and bladder. The inducibility of DNA adducts following in vitro treatments using blood lymphocytes also appears to be a risk factor in the development of lung and head and neck cancer. Corroborative evidence pointing to the importance of DNA adducts in tobacco carcinogenesis include numerous studies showing associations of tobacco smoke exposure with the induction of DNA adducts in humans in vivo. Further effort is necessary, however, to more fully characterize the dose-response relationship between smoking and DNA adducts in exposed target and surrogate tissues. The relationship between gene polymorphisms thought to modify tobacco-related cancer risk and DNA adduct levels is complex. Results of some DNA adduct studies (both in vitro and in vivo) appear inconsistent with the epidemiologic findings. This is evident for polymorphisms involving both carcinogen metabolism (e.g. GSTP1) and DNA repair (e.g. XRCC1). Molecular studies of human tumors suggest associations of p53 mutation with DNA adducts and have revealed correlations of DNA adduct levels with somatic alterations (e.g. 3p21 LOH) that are thought to occur at the very earliest stages of tobacco carcinogenesis. More research is needed to assess the relationship between endogenous sources of DNA adducts and tobacco smoke exposure and the relative oncogenic effects of chemically stable versus unstable DNA adducts. Many potentially fruitful new avenues of cancer research are emerging that integrate DNA adduct analyses with assessments of smoking, genetics, diet and ambient air quality. These investigations aim to understand the multifactorial nature of interindividual variability in response to tobacco carcinogens. As these trends continue a variety of innovative study designs and approaches will become important in human populations.

The myeloperoxidase gene in Alzheimer's disease: a case-control study and meta-analysis

Myeloperoxidase (MPO) presence has been demonstrated in microglia associated with senile plaques, and contributes to Alzheimer's disease (AD) pathology through oxidation-induced damage. Recently, a functional biallelic (G/A) polymorphism in the promotor region (-463) of the MPO gene has been associated with susceptibility to AD, but the reports of this association have been inconsistent. A case-control study utilizing a clinically well-defined group of 315 sporadic AD patients and 327 control subjects was performed to test this association. The current study does not demonstrate any significant difference in MPO genotype or allele frequencies between AD patients and controls. A meta-analysis of all studies available gave a non-significant (P=0.83) odds ratio of 1.02 for the MPO GG genotype. Our study in the Spanish population as well as the meta-analysis argue against the hypothesis that the MPO gene is causally related to AD.

Arylamine N-acetyltransferases and drug response

Arylamine N-acetyltransferases (NATs) play an important role in the interaction of competing metabolic pathways determining the fate of and response to xenobiotics as therapeutic drugs, occupational chemicals and carcinogenic substances. Individual susceptibility for drug response and possible adverse drug reactions are modulated by the genetic predisposition (manifested for example, by polymorphisms) and the phenotype of these enzymes. For all drugs metabolized by NATs, the impact of different in vivo enzyme activities is reviewed with regard to therapeutic use, prevention of side effects and possible indications for risk assessment by phenotyping and/or genotyping. As genes of NATs are susceptibility genes for multifactorial adverse effects and xenobiotic-related diseases, risk prediction can only be made possible by taking the complexity of events into consideration.