Yi JF, Li YM, Liu T, He WT, Li X, Zhou WC, Kang SL, Zeng XT, Zhang JQ. Mn-SOD and CuZn-SOD polymorphisms and interactions with risk factors in gastric cancer. World J Gastroenterol 2010; 16(37): 4738-4746 [PMID: 20872977 DOI: 10.3748/wjg.v16.i37.4738]
Corresponding Author of This Article
Yu-Min Li, Professor, Key Laboratory of Digestive System Tumors, Gansu Province, Lanzhou University Second Hospital, Lanzhou 730000, Gansu Province, China. lym19621225@hotmail.com
Article-Type of This Article
Brief Article
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Jian-Feng Yi, Shi-Liang Kang, Xiang-Ting Zeng, The First College of Clinical Medicine of Lanzhou University, Lanzhou 730000, Gansu Province, China
Yu-Min Li, Tao Liu, Jun-Qiang Zhang, Key Laboratory of Digestive System Tumors, Gansu Province, Lanzhou University Second Hospital, Lanzhou 730000, Gansu Province, China
Wen-Ting He, Xun Li, Wen-Ce Zhou, Department of General Surgery, The First Hospital of Lanzhou University, Lanzhou 730000, Gansu Province, China
ORCID number: $[AuthorORCIDs]
Author contributions: Yi JF, Li YM, Liu T, He WT, Li X and Zhou WC designed the study; Yi JF, Kang SL, Zeng XT and Zhang JQ collected human subject blood samples, epidemiological data and performed the experiments; Yi JF performed the statistical analysis and wrote the paper; Li YM, Liu T and He WT wrote and revised the manuscript.
Supported by National Natural Science Foundation of China, No. 30870364
Correspondence to: Yu-Min Li, Professor, Key Laboratory of Digestive System Tumors, Gansu Province, Lanzhou University Second Hospital, Lanzhou 730000, Gansu Province, China. lym19621225@hotmail.com
Telephone: +86-931-8942744 Fax: +86-931-8942744
Received: May 14, 2010 Revised: July 15, 2010 Accepted: July 22, 2010 Published online: October 7, 2010
Abstract
AIM: To investigate the effects of superoxide dismutase (SOD) polymorphisms (rs4998557, rs4880), Helicobacter pylori (H. pylori) infection and environmental factors in gastric cancer (GC) and malignant potential of gastric precancerous lesions (GPL).
METHODS: Copper-zinc superoxide dismutase (SOD1, CuZn-SOD)-G7958A (rs4998557) and manganese superoxide dismutase (SOD2, Mn-SOD)-Val16Ala (rs4880) polymorphisms were genotyped by SNaPshot multiplex polymerase chain reaction (PCR) in 145 patients with GPL (87 cases of gastric ulcer, 33 cases of gastric polyps and 25 cases of atrophic gastritis), 140 patients with GC and 147 healthy controls. H. pylori infection was detected by immunoblotting analysis.
RESULTS: The SOD1-7958A allele was associated with a higher risk of gastric cancer [odds ratio (OR) = 3.01, 95% confidence intervals (95% CI): 1.83-4.95]. SOD2-16Ala/Val genotype was a risk factor for malignant potential of GPL (OR = 2.04, 95% CI: 1.19-3.49). SOD2-16Ala/- genotype increased the risk of gastric cancer (OR = 2.85, 95% CI: 1.66-4.89). SOD1-7958A/- genotype, SOD2-16Ala/- genotype, alcohol drinking, positive family history and type I H. pylori infection were associated with risk of gastric cancer, and there were additive interactions between the two genotypes and the other three risk factors. SOD2-16Ala/Val genotype and positive family history were associated with malignant potential of GPL and jointly contributed to a higher risk for malignant potential of GPL (OR = 7.71, 95% CI: 2.10-28.22). SOD1-7958A/- genotype and SOD2-16Ala/- genotype jointly contributed to a higher risk for gastric cancer (OR = 6.43, 95% CI: 3.20-12.91).
CONCLUSION: SOD1-7958A/- and SOD2-16Ala/-genotypes increase the risk of gastric cancer in Chinese Han population. SOD2-16Ala/-genotype is associated with malignant potential of GPL.
Citation: Yi JF, Li YM, Liu T, He WT, Li X, Zhou WC, Kang SL, Zeng XT, Zhang JQ. Mn-SOD and CuZn-SOD polymorphisms and interactions with risk factors in gastric cancer. World J Gastroenterol 2010; 16(37): 4738-4746
Gastric cancer (GC) is the second most common malignancy worldwide and 42% of the cases occur in China[1]. Gastric carcinogenesis is a complex multi-factor and multi-step process involving various environmental carcinogens, Helicobacter pylori (H. pylori) infection and genetic variants. The involvement of reactive oxygen species (ROS) in the pathogenesis of gastric malignancies is well known[2,3]. ROS are molecules or ions formed by the incomplete one-electron reduction of oxygen, including singlet oxygen, superoxides, peroxides, hydroxyl radical, and hypochlorous acid, which contribute to the microbicidal activity of phagocytes, regulation of signal transduction and gene expression, induce oxidative damage to nucleic acids, proteins and lipids, and affect membrane fluidity by altering the amounts of unsaturated fatty acids and proteins in the cell membrane[4]. ROS participates simultaneously in Ras-Raf-MEK1/2-ERK1/2 and the p38 mitogen-activated protein kinases (MAPK) signaling pathway that have inverse functions in tumorigenesis[4]. In addition, with aging, humans tend to have an increased affectability of lipid peroxides caused by ROS[5]. A recent research has indicated that ROS also plays a critical role in the energy dysfunction of mitochondria caused by ethanol induced gastric mucosal injury[6].
Superoxide dismutase (SOD) is a major antioxidant enzyme, which plays a vital role in clearance of ROS. Among the isoforms of SOD, copper-zinc superoxide dismutase (SOD1, CuZn-SOD) with copper (Cu) and zinc (Zn) in its catalytic center is localized in the intracellular cytoplasmic compartments, and manganese superoxide dismutase (SOD2, Mn-SOD) plays an important role as a primary mitochondria antioxidant enzyme[7]. In addition, many researches have shown that the activity and expression of SOD changed significantly in gastric cancer patients[2,8,9], which can either promote or suppress tumor formation in human gastric mucosa[10].
In recent years, host genetic factors are emerging as determinants of increasing risk for many cancers including GC[11,12]. Therefore, SOD genes are good candidates to evaluate the genetic susceptibility to gastric cancer. The gene polymorphism SOD2-Val16Ala (rs4880) has been evaluated widely for its association with various cancers including GC[13-18]. Moreover, Val16Ala significantly reduced SOD2 catalytic activity in hepatocytes[19]. However, there have been few studies on the correlations between SOD1 polymorphisms and cancer, and SOD1 polymorphisms have not been evaluated for its association with risk of gastric cancer.
Epidemiologic evidence has shown that gastric cancer is associated with H. pylori colonization[1,20]. H. pylori, which infects 50% of the world’s population, is a major factor in both the induction of atrophic gastritis and histological progression to gastric cancer. Bacterial virulence factors such as cytotoxin-associated protein (CagA), vacuolating cytotoxin (VacA), and others have been associated with higher risks for gastric cancer development[21,22]. H. pylori vacuolating cytotoxin VacA can induce cellular vacuolation in epithelial cells and efficiently block proliferation of T cells by inducing a G1/S cell cycle arrest[23], and CagA protein can promote signal transduction of oncogene and cell division[24]. H. pylori is also associated with ROS and SOD. It has been shown that H. pylori induced the production of intracellular ROS in gastric cells[25], resulting in changes in the activity and content of SOD[26,27]. H. pylori infection can also cause DNA oxidative damage by its main virulence CagA and VacA, which further implied the role of bacteria in tumorogenesis[28,29].
Gastric cancer is a multifactorial disease. Besides genetic susceptibility and H. pylori infection, gastric cancer is also associated with dietary and environmental factors[30]. It has been indicated that long-term massive alcoholic consumption could induce gastric mucosal injury such as hyperemia, edema and erosion, and promote bacterial multiplication and the synthesis of carcinogenic nitrosamines[31]. Smoking has also been found as a risk factor of gastric cancer[32]. In this study, we investigated the association between gastric cancer and the polymorphisms of SOD1-G7958A (rs4998557) and SOD2-Val16Ala (rs4880), and evaluated the relationship between gastric cancer and the epidemiological factors including age, sex, smoking, alcohol drinking, family history of gastric cancer and different types of H. pylori infection.
MATERIALS AND METHODS
Study population
From June 2007 to June 2009, 145 patients with gastric precancerous lesions (GPL) (87 cases of gastric ulcer, 33 cases of gastric polypus and 25 cases of atrophic gastritis), 140 patients with gastric cancer and 147 healthy controls were recruited from 3A grade hospitals in Hexi Region, Gansu Province of China. The recruiting criteria of cases include newly diagnosed, histopathologically confirmed and previously untreated patients in the oncology, gastroenterology and general surgery departments. Healthy controls were composed of 147 individuals who visited the outpatient department for physical examination, without tumors and gastrointestinal diseases. Subjects were informed of the detailed study protocol, and signed consent forms, and the study was approved by local ethics committees. A questionnaire given to each patient collected information on (1) demographic factors, such as age and sex; (2) smoking (at least one cigarette per day for 6 mo or longer) and alcohol drinking history (at least twice a week for 6 mo or longer and at least 100 g each time); and (3) family history of gastric cancer (first-degree relatives with gastric cancer including parents, brothers and sisters). Each subject was donated 3 mL peripheral vein blood in EDTA-K2 anticoagulative tube for DNA extraction and 2 mL serum for H. pylori infection test, and all specimens were kept frozen at -80°C.
Extraction of genomic DNA
Genomic DNA was extracted from the whole blood using Blood Genome DNA Extraction Kit (TaKaRa Bio, Dalian, China) according to the manufacturer’s instructions. Concentration and purity of DNA were determined by SP-721 spectrophotometer (Eppendorf, Hamburg, Geman) at A260 nm and A280 nm. Integrity of DNA was confirmed by 1% agarose electrophoresis. The DNA samples were diluted to 5-10 ng/μL for genotyping. DNA was stored at -80°C until use.
Detection of H. pylori infection
Presence and type of H. pylori infection were tested with H. pylori antibody Immunoblotting Kit (Blot Biotech, Shenzhen, China) following the manufacturer’s instructions. Type I H. pylori infection was defined when either CagA or VacA was positive, or both were positive. Type II H. pylori infection was defined if ureases (UreA/UreB) were positive. Patients were defined as H. pylori negative if CagA, VacA and ureases were negative.
Genotyping of SOD polymorphisms
SOD1 G7958A and SOD2 Val16Ala (T201C) polymorphisms were determined by multiplex SNaPshot technology. PCR and single-base extension primers were designed using Primer3 software (http://frodo.wi.mit.edu/cgi-bin/primer3/primer3_http://www.cgi) (Table 1). Multiplex PCR was performed in a 20 μL reaction mixture containing 2 μL 10 × Buffer I, 1 U HotStarTaq polymerase (Qiagen, Dusseldorf, Geman), 0.3 mM dNTP, 3.0 mM MgCl2 (Qiagen), 2 μL each PCR primer, and 5 ng template DNA in a thermal cycler (Applied Biosystems, Foster City, USA). PCR conditions were 95°C for 15 min denaturation; 11 cycles at 94°C for 20 s, 65-0.5°C /cycle for 40 s, and 72°C for 100 s; 24 cycles at 94°C for 20 s, 59°C for 30 s, 72°C for 1.5 min; and 72°C for 2 min. PCR product was stored at 4°C. One U SAP (Promega, Madison, USA) and 1 U Exonuclease I (Epicentre, San Diego, USA) were added into 10 μL PCR product for purification at 37°C for 60 min, and 75°C for 15 min. SNaPshot analysis was performed in a volume of 10 μL containing 5 μL SNaPshot Multiplex Kit (Applied Biosystems), 2 μL multiplex PCR product, 1 μL single-base extension primer mix and 2 μL ddH2O. Extension reactions were performed in a thermal cycler (Applied Biosystems) at 96°C for 1min; 28 cycles at 96°C for 10 s, 50°C for 5 s, 60 °C for 30 s; and 60°C for 1 min. Extension product was stored at 4°C. One U SAP (Promega) was added into 2 μL extension product for purification at 37°C for 60 min, and 75°C for 15 min. Single-base extension products after purification were mixed with deionized formamide containing GeneScan 120 LIZ Size Standard, denatured at 95°C for 5 min and analyzed on an ABI Prism 3130XL genetic analyzer using GeneMapper 4.0 (Applied Biosystems).
For quality control, positive and negative controls and blinded duplicate samples were run. Alternative genotyping approaches were used as required to verify technical reliability and accuracy. Blinded repeat samples were run in 10% of the samples. A second scientist checked all laboratory interpretations independently.
Statistical analysis
Statistical analysis was performed using SPSS 15.0 (SPSS Inc., Chicago, IL, USA). Differences of measurement data and numeration data were assessed by single factor analysis of variance and Pearson χ2 test, respectively. Goodness-of-fit χ2 test was used to verify whether the distribution of SOD genotypes was in accordance with Hardy-Weinberg equilibrium. Non-conditional logistic regression analysis was performed to analyze the association of risk factors and genotypes of SOD with gastric cancer. According to the interaction model proposed by Khoury et al[33] and Ottman et al[34], we set up dummy variables in accordance with different genes-environmental exposure and analyzed genes-environment interaction in gastric cancer development by logistic regression. We determined the presence or absence of interactions by interaction coefficients (γ, γ=βeg/βe) (β, regressive coefficient; βeg, regressive coefficient when genetic and environmental factors coexist; βe, regressive coefficient when environmental factors exist alone) and judged the types of interaction by quantitative relationship of OReg (OR, odds ratio; OReg, OR when genetic and environmental factors coexist), ORe (ORe, OR when environmental factors exist alone) and ORg (ORg, OR when genes exist alone)[35-37]. Age and sex corrected odds ratios (ORs) with corresponding 95% confidence intervals (95% CI) and regressive coefficient (β) were calculated by logistic regression analysis. A P value of less than 0.05 was considered statistically significant.
RESULTS
Subject characteristics and analysis of risk factors for GC and malignant potential of GPL
The demographic characteristics and frequency distributions of smokers, alcohol drinkers and different types of H. pylori are shown in Table 2. There was no statistically significant difference among the three groups in terms of age, sex and smoking histories (P > 0.05). Alcohol drinking, positive family history and type I H. pylori infection were associated with an increased risk for GC development (OR = 3.29, 95% CI: 2.03-5.34; OR = 4.66, 95% CI: 2.33-9.32; OR = 4.86, 95% CI: 2.83-8.35, respectively). A positive family history was associated with an increased risk for malignant potential of GPL (OR = 1.99, 95% CI: 1.13-3.49).
Table 2 Demographic characteristics and risk factors for gastric cancer and malignant potential of gastric precancerous lesion.
All genotypes in the healthy controls were in Hardy-Weinberg equilibrium (P > 0.05). The frequencies of AG and AA genotypes in SOD1 were significantly higher in patients with GC than in healthy controls (P < 0.05), and the risk of gastric cancer in carriers with SOD1 A/- genotype was 3.01 folds higher (95% CI: 1.83-4.95) than in carriers with GG genotype. The frequencies of Val/Ala and Ala/Ala genotypes in SOD2 were significantly higher in patients with GC than in healthy controls (P < 0.05), and the risk of gastric cancer in carriers with SOD2 Ala/- genotype was 2.85 folds higher (95% CI: 1.66-4.89) than in carriers with Val/Val genotype. The malignant potential of GPL in carriers with SOD2 16Ala/Val and 16Ala/- genotypes was 2.04 folds (95% CI: 1.19-3.49) and 2.19 folds (95% CI: 1.30-3.68) higher than in those with Val/Val genotype, respectively (Table 3).
Table 3 Distribution of SOD1 G7958A and SOD2 Val16Ala polymorphisms.
Interaction of SOD2 Val16Ala and positive family history for malignant potential of GPL
A positive family history combined with SOD2 Ala/- genotype resulted in an increased risk for malignant potential of GPL (OR = 7.71, 95% CI: 2.10-28.22) (Table 4). The interaction coefficients (γ) was 2.96. SOD2 Ala/- genotype could generate the amplification effect on a positive family history, and the interaction accorded with the super-multiplication model.
Table 4 Interaction of family history and SOD2 Val16Ala for malignant potential of gastric precancerous lesion.
Family history
SOD2
GPL (%)
GC (%)
1OR(95% CI)
β
γ = βeg/βe
n = 145
n = 140
Negative
Val/Val
89 (61.4)
58 (41.4)
1.00
Negative
Ala/-
31 (21.4)
41 (29.3)
2.22 (1.24-3.97)
0.80
Positive
Val/Val
24 (16.6)
27 (19.3)
1.99 (1.03-3.84)
0.69
Positive
Ala/-
1 (0.7)
14 (10.0)
7.71 (2.10-28.22)
2.04
2.96
Interaction of SOD1 G7958A and environmental factors for gastric cancer development
Interaction 1: Alcohol drinking coexisted with SOD1 A/- genotype resulted in an increased risk for gastric cancer development (OR = 16.50, 95% CI: 6.67-40.86). The γ value was 1.20. SOD1 A/- genotype could generate the amplification effect on alcohol drinking.
Interaction 2: A positive family history coexisted with SOD1 A/- genotype resulted in an increased risk for gastric cancer development (OR = 15.56, 95% CI: 5.57-43.50). The γ value was 1.35. SOD1 A/- genotype could generate the amplification effect on a positive family history.
Interaction 3: Type I H. pylori infection coexisted with SOD1 A/- genotype resulted in an increased risk for gastric cancer development (OR = 10.71, 95% CI: 4.92-23.33). The γ value was 1.27. SOD1 A/- genotype could generate the amplification effect on type I H. pylori infection. All the interactions accorded with the additive model (Table 5).
Table 5 Interaction of SOD1 G7958A and environmental factors for gastric cancer development.
Interaction of SOD2 Val16Ala and environmental factors for gastric cancer development
Interaction 1: Alcohol drinking coexisted with SOD2 Ala/- genotype resulted in an increased risk for gastric cancer (OR = 9.46, 95% CI: 4.08-21.94). The γ value was 1.36. SOD2 Ala/- genotype could generate the amplification effect on alcohol drinking.
Interaction 2: A positive family history coexisted with SOD2 Ala/- genotype resulted in an increased risk for gastric cancer (OR = 12.86, 95% CI: 3.36-49.25). The γ value was 1.38. SOD2 Ala/- genotype could generate the amplification effect on a positive family history.
Interaction 3: Type I H. pylori infection coexisted with SOD1 A/- genotype SOD2 Ala/- genotype resulted in an increased risk for gastric cancer (OR, 9.07, 95% CI: 4.36-18.86). The γ value was 1.53. SOD1 A/- genotype could generate the amplification effect on type I H. pylori infection. All these interactions accorded with the additive model (Table 6).
Table 6 Interaction of SOD2 Val16Ala and environmental factors for gastric cancer development.
Factors
SOD2
HC (%)
GC (%)
1OR (95% CI)
β
γ = βeg/βe
n = 147
n = 140
Alcohol
No
Val/Val
89 (60.5)
33 (23.6)
1.00
No
Ala/-
11 (7.5)
21 (15.0)
4.89 (2.11-11.36)
1.59
Yes
Val/Val
34 (23.1)
52 (37.1)
5.26 (2.62-10.55)
1.66
Yes
Ala/-
13 (8.8)
34 (24.3)
9.46 (4.08-21.94)
2.25
1.36
Family history
Negative
Val/Val
114 (77.6)
58 (41.4)
1.00
Negative
Ala/-
21 (14.3)
41 (29.3)
3.90 (2.09-7.27)
1.36
Positive
Val/Val
9 (6.1)
27 (19.3)
6.34 (2.75-14.59)
1.85
Positive
Ala/-
3 (2.0)
14 (10.0)
12.86 (3.36-49.25)
2.55
1.38
Type I H. pylori
Negative
Val/Val
75 (51.0)
23 (16.4)
1.00
Negative
Ala/-
7 (4.8)
9 (6.4)
4.90 (1.59-15.08)
1.59
Positive
Val/Val
48 (32.7)
61 (43.6)
4.24 (2.30-7.09)
1.44
Positive
Ala/-
17 (11.6)
47 (33.6)
9.07 (4.36-18.86)
2.21
1.53
Gene-gene interaction for gastric cancer development
The combination of SOD1 A/- genotype and SOD2 Ala/- genotype resulted in an increased risk for gastric cancer (OR = 6.43, 95% CI: 3.20-12.91). The interaction accorded with the additive model (Table 7).
Table 7 Interaction of SOD1 G7958A and SOD2 Val16Ala for gastric cancer development.
Genotype
HC (%)
GC (%)
1OR (95% CI)
P
SOD1
SOD2
n = 147
n = 140
GG
Val/Val
72 (49.0)
31 (22.1)
1.00
A/-
Val/Val
50 (34.0)
54 (38.6)
2.54 (1.43-4.52)
0.002
GG
Ala/-
7 (4.8)
8 (5.7)
2.69 (0.89-8.14)
0.079
A/-
Ala/-
18 (12.2)
47 (33.6)
6.43 (3.20-12.91)
< 0.001
DISCUSSION
Reactive oxygen species (ROS) can damage DNA in the form of mutations, deletions, gene amplification and rearrangements, which may cause programmed cell death, or activation of several proto-oncogenes and/or inactivation of some tumor suppressor genes[16]. SOD, as a major antioxidant enzyme, plays a vital role in clearance of ROS. Previous studies have shown that the expression and activity of SOD played a role in the promotion or suppression of tumor formation in human gastric mucosa[10], and SOD2-Val16Ala polymorphism has been evaluated widely for its association with various cancers including gastric cancer[13-18].
In our study, we found that SOD2-Val16Ala polymorphism was associated with gastric cancer susceptibility and malignant potential of GPL. SOD2-Ala/- genotype carriers had a nearly 3-fold and 2-fold increased risk for developing gastric cancer and malignant potential of GPL compared with Val/Val genotype carriers. The results were in agreement with other studies on tumors such as adult brain tumors[38], prostate cancer[7], breast cancer[39], lung cancer[40] and pancreatic cancer[41]. Contrary to our results, the polymorphism of SOD2-Val16Ala was not found to be associated with gastric cancer in a Polish case-control study[18]. It implies that the distribution of polymorphism varies among different regions and races. However, a further study with a larger sample size and geographic range is needed.
SOD1 polymorphisms have been rarely evaluated for its association with risk of cancer occurrence. They were not found to be associated with the risk of breast cancer[16] and prostate cancer[7]. We found for the first time that the SOD1-7958A/- genotype was a risk factor for gastric cancer development. Subjects carrying 7958A/- genotype had a 3-fold increased risk for developing gastric cancer compared with carriers with G/G genotype, but no association was found between the 7958A/- genotype and malignant potential of GPL. SOD1-G7958A polymorphism could be a susceptible biomarker for gastric cancer. Our results may provide a new target for gene-targeted therapy of gastric cancer.
Gastric carcinogenesis is a complex multi-factor and multi-step process involving interactions of various environmental carcinogens, bacterial and genetic variants. To our knowledge, there has been no study on the interactions between SOD1 and SOD2 polymorphisms and environmental factors, and gene-gene interactions of SOD1 and SOD2 in gastric cancer. In our study, we found that carriers with a positive family history of gastric cancer had a 2-fold increased risk for malignant potential of GPL. The combination of a positive family history and SOD2-16Ala/- genotype contributed to a higher risk for malignant potential of GPL. Meanwhile, we also found that alcohol drinking, a positive family history and type I H. pylori infection were significantly associated with gastric cancer, and there were additive interactions with SOD1-7958A/- genotype and SOD2-16Ala/- genotype for gastric carcinogenesis. H. pylori infection could result in changes in the activity and content of SOD[26,27] and DNA oxidative damage by its main virulence CagA and VacA[28,29]. Therefore, the interaction of H. pylori infection and the polymorphisms of SOD1 and SOD2 exists theoretically. Our results suggested that gastric carcinogenesis resulted from combined action of gene and environment but not the unitary effect of gene or environment. Similar to our previous researches, we found that CagA+H. pylori infection was a definite risk factor for gastric cancer and that CagA+H. pylori infection combined with 762Ala/Ala genotype in PARP-1 contributed to a higher risk for gastric cancer[42]. Therefore, the interaction of gene-environment has played a role in the gastric carcinogenesis. We also found that there was an interaction between SOD1-7958A/- genotype and SOD2-16Ala/- genotype in gastric carcinogenesis, which had a 6-fold increased risk for gastric cancer development. This discovery has practical implications for gene therapy, and confirms the importance of gene-gene interaction in targeted therapy for cancer.
In summary, gastric carcinogenesis involves a variety of factors including genetic factors, environmental factors and gene-environment and gene-gene interactions. SOD1-7958A/- genotype, SOD2-16Ala/- genotype, alcohol drinking, a positive family history of gastric cancer, and type I H. pylori infection could be risk factors for gastric cancer in Chinese Han population, and there were positive gene-gene and gene-environment interactions. The effects of the interactions contributed to a higher risk for gastric cancer. Therefore, control of alcohol drinking and eradication of H. pylori infection may help lower the incidence of gastric cancer to a certain extent.
Because the sample size and risk factors investigated were limited in our study, and the genetic and environmental factors involved in carcinogenesis are numerous and complex, our conclusion remains to be further confirmed by studies of larger sample size on more risk factors among different races and regions so as to determine whether the SOD1-G7958A and SOD2-Val16Ala polymorphisms would be a susceptible biomarker for gastric cancer, and to evaluate whether there are interactions between gene and environment. In addition, Ala variant of SOD2 significantly reduced SOD2 catalytic activity in hepatocytes[19] and allows more efficient SOD2 to import into the mitochondrial matrix and generates more active SOD2 compared with the Val variant[43]. Thus, the Ala variant of SOD2 may increase the risk of gastric cancer by altering the activity or content of SOD2 to lower the ability of scavenging ROS. However, the carcinogenic mechanism of SOD1-7958A/- variant in gastric cancer is still unclear. As SOD1-G7958A is located in intron 1 of SOD1 gene, we imagine that the 7958A/- variant may cause gastric carcinogenesis by regulating the expression and alternative splicing of SOD1. This hypothesis remains to be further elucidated by detecting the expression levels of SOD1 and function analysis.
COMMENTS
Background
Gastric cancer (GC) is the second most common malignancy worldwide. Epidemiological evidences show that gastric carcinogenesis results from gene-environmental interactions. Superoxide dismutases (SOD) are major antioxidant enzymes, which play vital roles in clearance of reactive oxygen species (ROS) in vivo and can either promote or suppress tumor formation in human gastric mucosa. There have been few studies on the relationship between gene polymorphisms of SOD and GC in Chinese Han population and interactions between SOD polymorphisms and environmental factors in GC.
Research frontiers
In this study, the authors investigated the associations between gene polymorphisms of SOD and GC, evaluated the relationship between GC and the epidemiological factors including age, sex, smoking, alcohol drinking, family history of gastric cancer and different types of H. pylori infection, and analyzed gene-environmental and gene-gene interactions according to the interaction model.
Innovations and breakthroughs
This study showed that copper-zinc superoxide dismutase (SOD1)-7958A/- genotype and manganese superoxide dismutase (SOD2, Mn-SOD)-16Ala/- genotype, alcohol drinking, a positive family history of gastric cancer, and type I H. pylori infection were correlated with increased risk of GC in Chinese Han population. The gene-gene and gene-environment interactions contributed to a higher risk for GC.
Applications
This study showed that gene-environmental interactions play a great role in the gastric carcinogenesis, and control of alcohol drinking and eradication of H. pylori infection may contribute to a decreased incidence of GC to a certain extent.
Terminology
SODs are major antioxidant enzymes, which play vital roles in clearance of ROS. SOD1 with copper (Cu) and zinc (Zn) in their catalytic center are localized in intracellular cytoplasmic compartments. SOD2 plays an important role as a primary mitochondria antioxidant enzyme. The activity and expression of SOD change significantly in gastric cancer patients, which can either promote or suppress tumor formation in human gastric mucosa.
Peer review
The paper showed that SOD1 2809A/- genotype, SOD2 16Ala/- genotype, alcohol, positive family history and type I H. pylori infection were associated with risk of gastric cancer in Chinese Han population, and there were gene-gene and gene-environment interactions for gastric cancer development. SOD2 Ala/- genotype and a positive family history were risk factors for malignant potential of GPL, and there was a super-multiplication interaction. The described polymorphisms are novel with important scientific merit, but expanding the study with the mentioned aspects may improve the results.
Footnotes
Peer reviewers: Mitsuyoshi Urashima, MD, PhD, MPH, Division of Molecular Epidemiology, Jikei University School of Medicine, 3-25-8 Nishi-shimbashi, Minato-ku, Tokyo 105-8461, Japan; Ferenc Sipos, MD, PhD, Cell Analysis Laboratory, 2nd Department of Internal Medicine, Semmelweis University, Szentkirályi u. 46., Budapest 1088, Hungary
Monari M, Trinchero A, Calabrese C, Cattani O, Serrazanetti GP, Foschi J, Fabbri A, Zahlane D, Di Febo G, Tonini V. Superoxide dismutase in gastric adenocarcinoma: is it a clinical biomarker in the development of cancer?Biomarkers. 2006;11:574-584.
[PubMed] [DOI][Cited in This Article: ]
Wang J, Lü YY. Mitochondrial DNA 4977-bp deletion correlated with reactive oxygen species production and manganese superoxidedismutase expression in gastric tumor cells.Chin Med J (Engl). 2009;122:431-436.
[PubMed] [DOI][Cited in This Article: ]
Pan JS, Hong MZ, Ren JL. Reactive oxygen species: a double-edged sword in oncogenesis.World J Gastroenterol. 2009;15:1702-1707.
[PubMed] [DOI][Cited in This Article: ]
Yildirim Z, Kiliç N, Ozer C, Babul A, Take G, Erdogan D. Effects of taurine in cellular responses to oxidative stress in young and middle-aged rat liver.Ann N Y Acad Sci. 2007;1100:553-561.
[PubMed] [DOI][Cited in This Article: ]
Pan JS, He SZ, Xu HZ, Zhan XJ, Yang XN, Xiao HM, Shi HX, Ren JL. Oxidative stress disturbs energy metabolism of mitochondria in ethanol-induced gastric mucosa injury.World J Gastroenterol. 2008;14:5857-5867.
[PubMed] [DOI][Cited in This Article: ]
Kang D, Lee KM, Park SK, Berndt SI, Peters U, Reding D, Chatterjee N, Welch R, Chanock S, Huang WY. Functional variant of manganese superoxide dismutase (SOD2 V16A) polymorphism is associated with prostate cancer risk in the prostate, lung, colorectal, and ovarian cancer study.Cancer Epidemiol Biomarkers Prev. 2007;16:1581-1586.
[PubMed] [DOI][Cited in This Article: ]
Czeczot H, Scibior D, Skrzycki M, Podsiad M. [Antioxidant barrier in patients with gastric cancer--preliminary study].Pol Merkur Lekarski. 2005;19:521-525.
[PubMed] [DOI][Cited in This Article: ]
Hwang TS, Choi HK, Han HS. Differential expression of manganese superoxide dismutase, copper/zinc superoxide dismutase, and catalase in gastric adenocarcinoma and normal gastric mucosa.Eur J Surg Oncol. 2007;33:474-479.
[PubMed] [DOI][Cited in This Article: ]
Monari M, Foschi J, Calabrese C, Liguori G, Di Febo G, Rizzello F, Gionchetti P, Trinchero A, Serrazanetti GP. Implications of antioxidant enzymes in human gastric neoplasms.Int J Mol Med. 2009;24:693-700.
[PubMed] [DOI][Cited in This Article: ]
Con SA, Takeuchi H, Con-Chin GR, Con-Chin VG, Yasuda N, Con-Wong R. Role of bacterial and genetic factors in gastric cancer in Costa Rica.World J Gastroenterol. 2009;15:211-218.
[PubMed] [DOI][Cited in This Article: ]
Mitrunen K, Sillanpää P, Kataja V, Eskelinen M, Kosma VM, Benhamou S, Uusitupa M, Hirvonen A. Association between manganese superoxide dismutase (MnSOD) gene polymorphism and breast cancer risk.Carcinogenesis. 2001;22:827-829.
[PubMed] [DOI][Cited in This Article: ]
Cai Q, Shu XO, Wen W, Cheng JR, Dai Q, Gao YT, Zheng W. Genetic polymorphism in the manganese superoxide dismutase gene, antioxidant intake, and breast cancer risk: results from the Shanghai Breast Cancer Study.Breast Cancer Res. 2004;6:R647-R655.
[PubMed] [DOI][Cited in This Article: ]
Cebrian A, Pharoah PD, Ahmed S, Smith PL, Luccarini C, Luben R, Redman K, Munday H, Easton DF, Dunning AM. Tagging single-nucleotide polymorphisms in antioxidant defense enzymes and susceptibility to breast cancer.Cancer Res. 2006;66:1225-1233.
[PubMed] [DOI][Cited in This Article: ]
Oestergaard MZ, Tyrer J, Cebrian A, Shah M, Dunning AM, Ponder BA, Easton DF, Pharoah PD. Interactions between genes involved in the antioxidant defence system and breast cancer risk.Br J Cancer. 2006;95:525-531.
[PubMed] [DOI][Cited in This Article: ]
Hung RJ, Boffetta P, Brennan P, Malaveille C, Gelatti U, Placidi D, Carta A, Hautefeuille A, Porru S. Genetic polymorphisms of MPO, COMT, MnSOD, NQO1, interactions with environmental exposures and bladder cancer risk.Carcinogenesis. 2004;25:973-978.
[PubMed] [DOI][Cited in This Article: ]
Martin RC, Lan Q, Hughes K, Doll MA, Martini BD, Lissowska J, Zatonski W, Rothman N, Hein DW. No apparent association between genetic polymorphisms (-102 C>T) and (-9 >C) in the human manganese superoxide dismutase gene and gastric cancer(1).J Surg Res. 2005;124:92-97.
[PubMed] [DOI][Cited in This Article: ]
Martin RC, Li Y, Liu Q, Jensen NS, Barker DF, Doll MA, Hein DW. Manganese superoxide dismutase V16A single-nucleotide polymorphism in the mitochondrial targeting sequence is associated with reduced enzymatic activity in cryopreserved human hepatocytes.DNA Cell Biol. 2009;28:3-7.
[PubMed] [DOI][Cited in This Article: ]
Covacci A, Telford JL, Del Giudice G, Parsonnet J, Rappuoli R. Helicobacter pylori virulence and genetic geography.Science. 1999;284:1328-1333.
[PubMed] [DOI][Cited in This Article: ]
Gebert B, Fischer W, Weiss E, Hoffmann R, Haas R. Helicobacter pylori vacuolating cytotoxin inhibits T lymphocyte activation.Science. 2003;301:1099-1102.
[PubMed] [DOI][Cited in This Article: ]
Higashi H, Tsutsumi R, Muto S, Sugiyama T, Azuma T, Asaka M, Hatakeyama M. SHP-2 tyrosine phosphatase as an intracellular target of Helicobacter pylori CagA protein.Science. 2002;295:683-686.
[PubMed] [DOI][Cited in This Article: ]
Park JH, Kim TY, Jong HS, Kim TY, Chun YS, Park JW, Lee CT, Jung HC, Kim NK, Bang YJ. Gastric epithelial reactive oxygen species prevent normoxic degradation of hypoxia-inducible factor-1alpha in gastric cancer cells.Clin Cancer Res. 2003;9:433-440.
[PubMed] [DOI][Cited in This Article: ]
Bulbuloglu E, Inanc F, Bakaris S, Kantarceken B, Cetinkaya A, Cağlar R, Ilhami TK, Kilinc M. Association of adenosine deaminase, superoxide dismutase, and catalase activities with Helicobacter pylori.Dig Dis Sci. 2005;50:2296-2299.
[PubMed] [DOI][Cited in This Article: ]
Kidd M, Lastovica AJ, Atherton JC, Louw JA. Conservation of the cag pathogenicity island is associated with vacA alleles and gastroduodenal disease in South African Helicobacter pylori isolates.Gut. 2001;49:11-17.
[PubMed] [DOI][Cited in This Article: ]
Nan HM, Park JW, Song YJ, Yun HY, Park JS, Hyun T, Youn SJ, Kim YD, Kang JW, Kim H. Kimchi and soybean pastes are risk factors of gastric cancer.World J Gastroenterol. 2005;11:3175-3181.
[PubMed] [DOI][Cited in This Article: ]
Franke A, Teyssen S, Singer MV. Alcohol-related diseases of the esophagus and stomach.Dig Dis. 2005;23:204-213.
[PubMed] [DOI][Cited in This Article: ]
Ladeiras-Lopes R, Pereira AK, Nogueira A, Pinheiro-Torres T, Pinto I, Santos-Pereira R, Lunet N. Smoking and gastric cancer: systematic review and meta-analysis of cohort studies.Cancer Causes Control. 2008;19:689-701.
[PubMed] [DOI][Cited in This Article: ]
Khoury MJ, Wagener DK. Epidemiological evaluation of the use of genetics to improve the predictive value of disease risk factors.Am J Hum Genet. 1995;56:835-844.
[PubMed] [DOI][Cited in This Article: ]
Taioli E, Zocchetti C, Garte S. Models of interaction between metabolic genes and environmental exposure in cancer susceptibility.Environ Health Perspect. 1998;106:67-70.
[PubMed] [DOI][Cited in This Article: ]
Clayton D, McKeigue PM. Epidemiological methods for studying genes and environmental factors in complex diseases.Lancet. 2001;358:1356-1360.
[PubMed] [DOI][Cited in This Article: ]
Rajaraman P, Hutchinson A, Rothman N, Black PM, Fine HA, Loeffler JS, Selker RG, Shapiro WR, Linet MS, Inskip PD. Oxidative response gene polymorphisms and risk of adult brain tumors.Neuro Oncol. 2008;10:709-715.
[PubMed] [DOI][Cited in This Article: ]
Bica CG, da Silva LL, Toscani NV, Zettler CG, Gottlieb MG, Alexandre CO, Graudenz MS, Mânica da Cruz IB. Polymorphism (ALA16VAL) correlates with regional lymph node status in breast cancer.Cancer Genet Cytogenet. 2010;196:153-158.
[PubMed] [DOI][Cited in This Article: ]
Zejnilovic J, Akev N, Yilmaz H, Isbir T. Association between manganese superoxide dismutase polymorphism and risk of lung cancer.Cancer Genet Cytogenet. 2009;189:1-4.
[PubMed] [DOI][Cited in This Article: ]
Wheatley-Price P, Asomaning K, Reid A, Zhai R, Su L, Zhou W, Zhu A, Ryan DP, Christiani DC, Liu G. Myeloperoxidase and superoxide dismutase polymorphisms are associated with an increased risk of developing pancreatic adenocarcinoma.Cancer. 2008;112:1037-1042.
[PubMed] [DOI][Cited in This Article: ]
Zhang Q, Li Y, Li X, Zhou W, Shi B, Chen H, Yuan W. PARP-1 Val762Ala polymorphism, CagA+ H. pylori infection and risk for gastric cancer in Han Chinese population.Mol Biol Rep. 2009;36:1461-1467.
[PubMed] [DOI][Cited in This Article: ]
Sutton A, Imbert A, Igoudjil A, Descatoire V, Cazanave S, Pessayre D, Degoul F. The manganese superoxide dismutase Ala16Val dimorphism modulates both mitochondrial import and mRNA stability.Pharmacogenet Genomics. 2005;15:311-319.
[PubMed] [DOI][Cited in This Article: ]
