Antioxidant genes, diabetes and dietary antioxidants in association with risk of pancreatic cancer

Catalase C262T genetic variation and cancer susceptibility: A comprehensive meta-analysis with meta-regression and trial sequential analysis

Background

Several genetic association studies have analyzed the link between the catalase ( CAT) C262T variant and different cancers, but the findings remain controversial. Our research centered on establishing a comprehensive correlation between the C262T variant and different cancers.

Methods

This study was conducted using RevMan 5.4 software following the PRISMA 2020 guidelines. For this meta-analysis, 53 case-control studies (18,258 cases and 47,476 controls) were chosen.

Results

The analysis revealed that three genetic models were statistically linked ( P < 0.05) to overall cancer susceptibility in codominant model 2 (COD2): odds ratio (OR) = 1.16, COD3: OR = 1.21, recessive model (RM): OR = 1.20). After stratification by ethnicity, a significant link ( P < 0.05) was found in Caucasians (COD2: OR = 1.18, COD3: OR = 1.17, over-dominant model (ODM): OR = 1.19) and Asians (COD3: OR = 1.49). Subgroup analyses revealed a significant correlation ( P < 0.05) with blood-and-bone-marrow-related cancer, skin cancer, gastrointestinal-tract-related cancer, prostate cancer, and gynecologic cancer. Three genetic models in population-based controls (COD2: OR = 1.19, COD3: OR = 1.17, RM: OR = 1.19) and two genetic models in hospital-based controls (COD3: OR = 1.40, RM: OR = 1.24) were found to be significantly correlated ( P < 0.05) with cancer. Also, three genetic models for polymerase chain reaction-restriction fragment length polymorphism (COD3: OR = 1.46; RM: OR = 1.34, ODM: OR = 0.80) and three models for MALDI-TOF + MassARRAY (COD2: OR = 1.32, RM: OR = 1.26, allele model: OR = 1.14) genotyping methods showed significant association ( P < 0.05) with cancer. The meta-regression showed that the quality scores might be a source of significant heterogeneity under the COD2 model (coefficient = 0.176, P = 0.029). Trial sequential analysis also validated the adequacy of the sample size on overall findings.

Conclusion

Our results indicate that CAT C262T variant is associated with overall cancer susceptibility, especially in Caucasians and Asians. This variant may also be associated with blood-and-bone-marrow-related, GIT-related, prostate, skin, and gynecological cancers.

Association Between Antioxidant Nutrients, Oxidative Stress-Related Gene Polymorphism and Skeletal Fluorosis in Guizhou, China

Background

Oxidative stress plays an important role in the pathogenesis of endemic fluorosis. We analyzed associations between oxidative stress-related gene polymorphisms (PON1 rs662, CAT rs769217, rs2300182, and SOD2 rs11968525) and skeletal fluorosis, and examined potential gene–environment interactions with dietary vitamin C, vitamin E, zinc, and selenium intake.

Methods

A cross-sectional study was conducted in the Zhijin County, Guizhou Province of China. Skeletal fluorosis was identified according to the Chinese Diagnostic Criteria of Endemic Skeletal Fluorosis. Dietary information was assessed through face-to-face interviews by trained interviewers using a 75-item food frequency questionnaire. The genotype was detected by high throughput TaqMan-MGB RT-PCR technology. Odds ratios (ORs) and 95% CIs were calculated using an unconditional logistic regression model.

Results

Intake of vitamin E, zinc, and selenium was found to be inversely associated with the risk of skeletal fluorosis. The multivariable-adjusted ORs were 0.438 (95% CI: 0.268 to 0.715, P-trend < 0.001) for vitamin E, 0.490 (95% CI: 0.298 to 0.805, P-trend = 0.001) for zinc, and 0.532 (95% CI: 0.324 to 0.873, P-trend = 0.010) for selenium when comparing the highest with the lowest quartile. The relationship for vitamin C was not observed after adjustment for risk factors. Furthermore, participants with PON1 rs662 AA genotype had a significantly decreased risk of skeletal fluorosis compared with those with the GG genotype (OR = 0.438, 95% CI: 0.231 to 0.830). GG + AG genotype carriers were 2.212 times more likely to have skeletal fluorosis than AA carriers (OR = 2.212, 95% CI: 1.197 to 4.090). Compared with AA carriers, AG carriers had a 2.182 times higher risk of skeletal fluorosis (OR = 2.182, 95% CI: 1.143 to 4.163). Although we observed the risk of skeletal fluorosis was higher with a lower intake of antioxidant nutrients, the potential interactions between nutrient intake and genetic polymorphisms were not observed.

Conclusion

Participants with a higher intake of vitamin E, zinc, and selenium have a lower likelihood of skeletal fluorosis. In addition, the PON1 rs662 polymorphism is related to skeletal fluorosis.

Survival of Laryngeal Cancer Patients Depending on Zinc Serum Level and Oxidative Stress Genotypes

Stress contributes to various aspects of malignancy and could influence survival in laryngeal cancer patients. Among antioxidant mechanisms, zinc and the antioxidant enzymes superoxide dismutase 2, catalase and glutathione peroxidase 1 play a major role. The aim of this study was a prospective evaluation of the survival of patients with laryngeal cancer in relation to serum levels of zinc in combination with functional genotype differences of three key antioxidant enzymes. The study group consisted of 300 patients treated surgically for laryngeal cancer. Serum zinc levels and common polymorphisms in SOD2, CAT and GPX1 were analyzed. The risk of death in patients with the lowest zinc levels was increased in comparison with patients with the highest levels. Polymorphisms of antioxidant genes by themselves were not correlated with survival, however, serum zinc level impact on survival was stronger for SOD2 TC/TT and CAT CC variants. GPX1 polymorphisms did not correlate with zinc levels regarding survival. In conclusion, serum zinc concentration appears to be an important prognostic factor for survival of patients diagnosed with laryngeal cancer. When higher zinc levels were correlated with polymorphisms in SOD2 and CAT a further increase in survival was observed.

Genetic Variation in SOD1 Gene Promoter Ins/Del and Its Influence on Oxidative Stress in Beta Thalassemia Major Patients

Background: A genetic polymorphism of 50 bp insertion/deletion (Ins/Del) (rs 36232792) in the promoter region of the SOD1 was reported to influence the enzyme activity. The present study aimed to evaluate the status of this polymorphism of human peripheral blood cells and its association with SOD enzyme activity in beta-thalassemia major patients. Material and Methods: The study was carried out on 200 thalassemia major patients and 200 healthy controls healthy. The SOD1 genotypes were determined using a polymerase chain reaction (PCR)-based method. Serum SOD activity were assessed using SOD assay kit. In-silico analysis was assessed using loss-of-function (LoFtool) (PMID: 27563026). Results: No association was found between the insertion/deletion (Ins/Del) polymorphism and SOD enzyme activity in thalassemia major patients Conclusion: The results of this study indicated that the SOD enzyme activity is not affected by the 50 bp Ins/Del polymorphism of SOD1in thalassemia major patients. Further research with larger sample size and with other genes of antioxidant system is required.

Association between MnSOD Val16Ala Polymorphism and Cancer Risk: Evidence from 33,098 Cases and 37,831 Controls

Manganese superoxide dismutase (MnSOD) plays a critical role in the defense against reactive oxygen species. The association between MnSOD Val16Ala polymorphism and cancer risk has been widely studied, but the results are contradictory. To obtain more precision on the association, we performed the current meta-analysis with 33,098 cases and 37,831 controls from 88 studies retrieved from PubMed, Embase, Chinese National Knowledge Infrastructure (CNKI), and Wanfang databases. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of association. We found that the polymorphism was associated with an increased overall cancer risk (homozygous: OR = 1.09, 95% CI = 1.00-1.19; heterozygous: OR = 1.07, 95% CI = 1.02-1.12; dominant: OR = 1.08, 95% CI = 1.02-1.14; and allele comparison: OR = 1.06, 95% CI = 1.02-1.11). Stratification analysis further showed an increased risk for prostate cancer, Asians, Caucasians, population-based studies, hospital-based studies, low quality and high quality studies. However, the increased risk for MnSOD Val16Ala polymorphism among Asians needs further validation based on the false-positive report probability (FPRP) test. To summarize, this meta-analysis suggests that the MnSOD Val16Ala polymorphism is associated with significantly increased cancer risk, which needs further validation in single large studies.

Pancreatic cancer risk is modulated by inflammatory potential of diet and ABO genotype: a consortia-based evaluation and replication study

Diets with high inflammatory potential are suspected to increase risk for pancreatic cancer (PC). Using pooled analyses, we examined whether this association applies to populations from different geographic regions and population subgroups with varying risks for PC, including variation in ABO blood type. Data from six case-control studies (cases, n = 2414; controls, n = 4528) in the Pancreatic Cancer Case-Control Consortium (PanC4) were analyzed, followed by replication in five nested case-control studies (cases, n = 1268; controls, n = 4215) from the Pancreatic Cancer Cohort Consortium (PanScan). Two polymorphisms in the ABO locus (rs505922 and rs8176746) were used to infer participants' blood types. Dietary questionnaire-derived nutrient/food intake was used to compute energy-adjusted dietary inflammatory index (E-DII®) scores to assess inflammatory potential of diet. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using multivariable-adjusted logistic regression. Higher E-DII scores, reflecting greater inflammatory potential of diet, were associated with increased PC risk in PanC4 [ORQ5 versus Q1=2.20, 95% confidence interval (CI) = 1.85-2.61, Ptrend < 0.0001; ORcontinuous = 1.20, 95% CI = 1.17-1.24], and PanScan (ORQ5 versus Q1 = 1.23, 95% CI = 0.92-1.66, Ptrend = 0.008; ORcontinuous = 1.09, 95% CI = 1.02-1.15). As expected, genotype-derived non-O blood type was associated with increased PC risk in both the PanC4 and PanScan studies. Stratified analyses of associations between E-DII quintiles and PC by genotype-derived ABO blood type did not show interaction by blood type (Pinteraction = 0.10 in PanC4 and Pinteraction=0.13 in PanScan). The results show that consuming a pro-inflammatory diet and carrying non-O blood type are each individually, but not interactively, associated with increased PC risk.

Curcumin inhibits superoxide dismutase-induced epithelial-to-mesenchymal transition via the PI3K/Akt/NF-κB pathway in pancreatic cancer cells

Curcumin is a natural polyphenol compound derived from turmeric. It possesses multiple pharmacological properties, including antioxidant, anti-inflammatory and anti-tumor progression properties. Our recent study demonstrated that superoxide dismutase (SOD)-dependent production of hydrogen peroxide (H2O2) promoted the invasive and migratory activity of pancreatic cancer cells. However, whether curcumin suppresses SOD-induced cancer progression and the related mechanisms remains unclear. Since epithelial‑to-mesenchymal transition (EMT) plays a key role in tumor metastasis, the aim of the present study was to examine whether curcumin intervenes with SOD-induced EMT in pancreatic cancer and the underlying mechanism. The human pancreatic cancer cells BxPC-3 and Panc-1 were exposed to SOD in the presence or absence of curcumin, catalase (CAT, a scavenger of H2O2), or LY 294002 [a phosphoinositide-3 kinase (PI3K) inhibitor]. Intracellular reactive oxygen species (ROS) and H2O2 were evaluated by 2,7-dichlorodihydrofluorecein diacetate and H2O2 assay, respectively. The activation of p-Akt and p-nuclear factor (NF)-κB were examined by western blotting. The migratory and invasive abilities of pancreatic cancer cells were tested by the wound healing and Transwell invasion assays. The expression of E-cadherin, N-cadherin and vimentin (EMT-related genes) were measured by reverse transcription-quantitative polymerase chain reaction and western blotting at the mRNA and protein levels, respectively. The findings of the present study demonstrated that curcumin decreased SOD-induced production of ROS and H2O2 in BxPC-3 and Panc-1 cells. Curcumin was able to suppress SOD-induced invasion and migration, and it also regulated the expression of the above‑mentioned EMT-related genes and cell morphology. SOD-induced cell invasion was also inhibited by catalase and LY 294002. Furthermore, the levels of p-Akt and p-NF-κB caused by SOD could be offset by treatment with curcumin and LY 294002. To summarize, these results demonstrated that curcumin was able to prevent SOD-driven H2O2-induced pancreatic cancer metastasis by blocking the PI3K/Akt/NF-κB signaling pathway. The use of curcumin to inhibit the H2O2/Akt/NF-κB axis may be a promising therapeutic approach to the treatment of patients with pancreatic cancer.

Association between glutathione peroxidase-1 (GPX1) Rs1050450 polymorphisms and cancer risk

Glutathione peroxidase (GPX), one of the antioxidant enzymes, exerts a vital role in reducing oxidative damage. GPX1 Pro198Leu (rs1050450) polymorphism has been reported in the development of several cancers, while the results were inconsistent. We thus conducted this meta-analysis to identify the association between GPX1 (rs1050450) polymorphism and cancer risk. 52 eligible publications with 60 case-control studies were included, with 21,296 cancer patients and 30,346 controls. The results in total population suggested there was a significant association between GPX1 (rs1050450) polymorphism and cancer susceptibility in part genetic models (TT vs CT+CC: OR = 1.15, 95% CI = 1.01-1.32, P = 0.042; TT vs CC: OR = 1.15, 95% CI = 1.00-1.31, P = 0.044; T vs C: OR = 1.09, 95% CI = 1.01-1.17, P = 0.02). The stratified analysis by cancer types suggested a positive correlation between GPX1 (rs1050450) polymorphism and the development of bladder cancer (TT+CT vs CC: OR = 1.72, 95% CI = 1.09-2.70, P = 0.019; TT vs CT+CC: OR = 3.56, 95% CI = 1.42-8.94, P = 0.007; TT vs CC: OR = 3.75, 95% CI = 1.41-9.94, P = 0.008; T vs C: OR = 1.941, 95% CI = 1.17-3.22, P = 0.01) as well as head and neck cancer (TT vs CT+CC: OR = 2.19, 95% CI = 1.39-3.46, P = 0.001) and brain cancer (TT+CT vs CC: OR = 1.19, 95% CI = 1.03-1.37, P = 0.018). These results support that GPX1 (rs1050450) polymorphism might be a candidate marker for cancer risk with type-specific effects.

Superoxide Dismutases in Pancreatic Cancer

The incidence of pancreatic cancer is increasing as the population ages but treatment advancements continue to lag far behind. The majority of pancreatic cancer patients have a K-ras oncogene mutation causing a shift in the redox state of the cell, favoring malignant proliferation. This mutation is believed to lead to nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation and superoxide overproduction, generating tumorigenic behavior. Superoxide dismutases (SODs) have been studied for their ability to manage the oxidative state of the cell by dismuting superoxide and inhibiting signals for pancreatic cancer growth. In particular, manganese superoxide dismutase has clearly shown importance in cell cycle regulation and has been found to be abnormally low in pancreatic cancer cells as well as the surrounding stromal tissue. Likewise, extracellular superoxide dismutase expression seems to favor suppression of pancreatic cancer growth. With an increased understanding of the redox behavior of pancreatic cancer and key regulators, new treatments are being developed with specific targets in mind. This review summarizes what is known about superoxide dismutases in pancreatic cancer and the most current treatment strategies to be advanced from this knowledge.

Genetic Polymorphisms in SOD (rs2070424, rs7880) and CAT (rs7943316, rs1001179) Enzymes Are Associated with Increased Body Fat Percentage and Visceral Fat in an Obese Population from Central Mexico

BACKGROUND AND AIMS

Oxidative disturbance is an important factor involved in the etiology of comorbidities associated with obesity. Genetic polymorphisms such as SOD1 -251A>G, SOD2 47 C>T, CAT -21A>T and CAT -262 C>T have been described to alter the activity of antioxidant enzymes. The aim of the present work was to analyze the association of the mentioned SNPs with obesity and their relationship with anthropometric and clinical variables in this group.

METHODS

The study included 416 Mexican women (208 normal weight, NW and 208 subjects with obesity, OB). Dietary intake, anthropometric, biochemical and clinical features were evaluated and then analyzed in function of the genotypes.

RESULTS

The mutated carriers (GA+GG) of SOD -251 were significantly higher in the OB group (0.24) compared to the NW group (0.08). The other SNPs showed no differences compared with control group. When comparing carrier mutated subjects with obesity vs. wild-type obese participants with the SNPs SOD1 -251, SOD2 47 and CAT -262, the carriers showed a significantly (p <0.05) higher value in body fat percentage. Also, carriers of SOD2 47 and CAT-262 showed significantly higher values (p = 0.002) and (p = 0.01), respectively, when visceral fat was compared between groups. Systolic blood pressure was significantly higher (p = 0.02) in carriers of mutated CAT-21.

CONCLUSION

SOD1 -251A>G is associated with obesity independent of the presence of diabetes or dyslipidemia. Mutated obese carries of SOD1 -251, SOD2 47 and CAT -262 are associated with a higher distribution of fat in comparison with obese wild-type carriers.

Genetic polymorphisms of superoxide dismutase-1 A251G and catalase C-262T with the risk of colorectal cancer

Oxidative stress is significant in numerous types of disease including cancer. To protect cells and organs against reactive oxygen species (ROS), the body has evolved an antioxidant protection system that involved in the detoxification of ROS. Single nucleotide polymorphisms (SNP) of anti-oxidative enzymes may dramatically change the activity of the encoded proteins; therefore, certain alleles can be established as risk factors for some kind of multi-factorial diseases including cancer. In present study we investigate the possible association between polymorphisms of superoxide dismutase 1 (SOD1, OMIM: 147450) and catalase (CAT, OMIM: 115500) genes and the risk of colorectal cancer (CRC). The study included 204 colorectal cancer patients and 239 healthy control group matched for gender and age. Genotyping of SOD1 A251G and CAT C-262T were done by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) method. There was no significant association between CAT C-262T polymorphism and susceptibility to CRC (P>0.05). The carries of the G allele of SOD1 significantly showed higher prevalence in CRC patients compared with the control group (OR=1.84, 95% CI=1.13-2.98, P=0.013). We assessed the effect of combination of genotypes of the study polymorphisms on the risk of CRC. We found that the combination of AG+GG (SOD1) and CC (CAT) increases the risk of developing CRC (OR=2.38, 95% CI=1.25-4.52, P=0.008).

Two common functional catalase gene polymorphisms (rs1001179 and rs794316) and cancer susceptibility: evidence from 14,942 cancer cases and 43,285 controls

Recent studies have focused on the associations of catalase polymorphisms with various types of cancer, including cervical and prostate cancers. However, the results were inconsistent. To obtain a more reliable conclusion, we evaluated the relationship between the two common catalase gene polymorphisms (rs1001179 and rs794316) and cancer risk by a meta-analysis. Our meta-analysis included 37 published studies involving 14,942 cancer patients and 43,285 cancer-free controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the cancer risk. The results demonstrated that the rs1001179 polymorphism was associated with an increased cancer risk in the recessive and homozygote models (TT vs. CC: OR = 1.19, P = 0.01; TT vs. CT+CC: OR = 1.19, P <0.001). Furthermore, stratified analyses revealed a significant association between the rs1001179 polymorphism and prostate cancer in all models except the homozygote comparison. An association of the rs794316 polymorphism with cancer risk was detected in two genetic models (TT vs. AA: OR = 1.34, 95% CI = 1.03-1.74, P <0.001; TT vs. AT+AA: OR = 1.39, 95% CI = 1.09-1.77, P = 0.01). Additional well-designed studies with large samples should be performed to validate our results.

Hydrogen peroxide mediates hyperglycemia-induced invasive activity via ERK and p38 MAPK in human pancreatic cancer

Diabetes mellitus and pancreatic cancer are intimately related, as approximately 85% of pancreatic cancer patients suffer from glucose intolerance or even diabetes. In this study, we evaluate the underlying mechanism by which hyperglycemia modulates the invasive potential of cancer cells and contributes to their enhanced metastatic behavior. Here we show that hyperglycemia increases the hydrogen peroxide (H2O2) concentration through up-regulation of manganese superoxide dismutase (SOD2) expression, which further activates the ERK and p38 MAPK pathways, as well as the transcription factors NF-κB and AP-1, in a time-dependent manner. The invasion of pancreatic cancer cells resulting from the activation of the H2O2/MAPK axis under high glucose conditions is effectively inhibited by PD 98059 (ERK inhibitor), SB 203580 (p38 MAPK inhibitor), polyethylene glycol-conjugated catalase (PEG-CAT), or the siRNA specific to SOD2. In addition, streptozotocin-treated diabetic nude mice exhibit a stronger tumor invasive ability in renal capsule xenografts which could be suppressed by PEG-CAT treatment. Furthermore, the integrated optical density (IOD) of SOD2 and uPA stainings is higher in the tumor tissues of pancreatic cancer patients with diabetes compared with pancreatic cancer patients with euglycemia. Taken together, our results demonstrate that hyperglycemia enhances cell invasive ability through the SOD2/H2O2/MAPK axis in human pancreatic cancer. Thus, SOD2/H2O2/MAPK axis may represent a promising therapeutic target for pancreatic cancer patients combined with diabetes mellitus.

The Role of Catalase C262T Gene Polymorphism in the Susceptibility and Survival of Cancers

Catalase (CAT), one antioxidant enzyme, may provide resistance against many diseases. Many previous studies reported predictive and prognostic values of CAT C262T polymorphism in cancers, with divergent results. This study aimed to summarize the overall relationships between CAT C262T polymorphism and cancer risk or survival. A total of 27 eligible publications were included in susceptibility analysis, while 8 publications contained survival outcomes. The results revealed significant relationship between CAT C262T polymorphism and cancer risk(TT + CT vs CC: OR = 1.05, 95%CI = 1.00–1.10, P = 0.036), subgroup analyses indicated the CAT C262T polymorphism was significantly correlated with an increased risk for prostate cancer (TT vs CC + CT: OR = 1.43, 95%CI = 1.20–1.70, P < 0.001) and increased risk among Caucasians (TT vs CC + CT: OR = 1.19, 95%CI = 1.09–1.31, P < 0.001), while no associations between the polymorphism and Asian or mixed population were established. In the survival analysis, no interactions were identified between this polymorphism and cancer survival (TT + CT vs CC: HR = 1.37, 95%CI = 0.70–2.70, P = 0.36). In conclusion, the CAT C262T polymorphismmay be a candidate markerfor cancer risk with type-specific and population-specific effects but not a fine prognostic factor for cancer survival.

Superoxide dismutase promotes the epithelial-mesenchymal transition of pancreatic cancer cells via activation of the H2O2/ERK/NF-κB axis

Our previous study revealed that superoxide dismutase (SOD)-dependent production of reactive oxygen species (ROS) was able to increase the invasive ability of pancreatic cancer cells. However, the underlying mechanisms by which SOD enhances metastasis are still not fully elucidated. As epithelial-mesenchymal transition (EMT) is a key player in tumor metastasis, the aim of this study was to evaluate whether SOD affects EMT in pancreatic cancer cells and the related mechanism. Human pancreatic cancer cells BxPC-3 and Panc-1 were utilized to examine the level of hydrogen peroxide (H2O) in the absence or presence of SOD and catalase (CAT). The activation of phospho-ERK and phospho-NF-κB were measured by western blot analysis. Wound healing assay and transwell invasion assay were used to detect the migratory and invasive potential of cancer cells. The EMT-related factors, E-cadherin, N-cadherin and vimentin were detected by QT-PCR and western blot analysis. The results of present study showed that SOD not only increased cell migration and invasion in pancreatic cancer, but also mediated the expression of EMT-related factors and cell morphology. In addition, the levels of phospho-ERK and phospho-NF-κB were induced by SOD which could be counter-balanced by both CAT treatment and PD 98059 (an ERK inhibitor). Taken together, these data indicate that SOD promotes the invasive and migratory activity of pancreatic cancer. Blocking the H2O2/ERK/NF-κB axis might be a novel strategy for the treatment of this severe malignancy.

Genetics and Genetic Testing in Pancreatic Cancer

Genetic testing of germline DNA is used in patients suspected of being at risk of pancreatic ductal adenocarcinoma (PDAC) to better define the individual's risk and to determine the mechanism of risk. A high genetic risk increases the pretest probability that a biomarker of early cancer is a true positive and warrants further investigation. The highest PDAC risk is generally associated with a hereditary predisposition. However, the majority of PDAC results from complex, progressive gene-environment interactions that currently fall outside the traditional risk models. Over many years, the combination of inflammation, exposure to DNA-damaging toxins, and failed DNA repair promote the accumulation of somatic mutations in pancreatic cells; PDAC risk is further increased by already present oncogenic germline mutations. Predictive models and new technologies are needed to classify patients into more accurate and mechanistic PDAC risk categories that can be linked to improved surveillance and preventative strategies.

Gene-by-Environment Interactions in Pancreatic Cancer: Implications for Prevention

Pancreatic cancer (PC) has been estimated to have higher incidence and correspondingly higher mortality rates in more developed regions worldwide. Overall, the age-adjusted incidence rate is 4.9/10(5) and age-adjusted mortality rate is at 4.8/10(5). We review here our current knowledge of modifiable risk factors (cigarette smoking, obesity, diet, and alcohol) for PC, genetic variants implicated by genome-wide association studies, possible genetic interactions with risk factors, and prevention strategies to provide future research directions that may further our understanding of this complex disease. Cigarette smoking is consistently associated with a two-fold increased PC risk. PC associations with dietary intake have been largely inconsistent, with the potential exception of certain unsaturated fatty acids decreasing risk and well-done red meat or meat mutagens increasing risk. There is strong evidence to support that obesity (and related measures) increase risk of PC. Only the heaviest alcohol drinkers seem to be at an increased risk of PC. Currently, key prevention strategies include avoiding tobacco and excessive alcohol consumption and adopting a healthy lifestyle. Screening technologies and PC chemoprevention are likely to become more sophisticated, but may only apply to those at high risk. Risk stratification may be improved by taking into account gene environment interactions. Research on these modifiable risk factors is key to reducing the incidence of PC and understanding who in the population can be considered high risk.

The catalase C-262T gene polymorphism and cancer risk: a systematic review and meta-analysis

Many studies suggest that catalase C-262T gene polymorphism is associated with cancer risk, but with inconsistent results. This study aimed to summarize the overall association between catalase C-262T polymorphism and cancer risk. Literature search was performed in PubMed, Embase, and other databases, studies regarding the association between catalase C-262T polymorphism and cancer risk were identified, and data were retrieved and analyzed by using Review Manager 5.0.24 and STATA 12.0. A total of 18 publications with 22 case-control studies, including 9777 cancer patients and 12,223 controls, met the inclusion criteria. Meta-analysis results showed significant association between catalase C-262 T polymorphism and cancer risk (TT vs CT + CC: odds ratio [OR] = 1.17, 95% confidence interval [CI] = 1.03-1.31, P = 0.01). Subgroup analyses stratified by cancer types suggested the catalase C-262T polymorphism was significantly associated with an increased prostate cancer risk (TT vs CT + CC: OR = 1.61, 95% CI = 1.17-2.22, P = 0.004); for subgroup analyses stratified by ethnicity, no associations between this polymorphism and Asians or whites were identified (CT + TT vs CC: OR = 1.11, 95% CI = 0.98-1.26, P = 0.09 for whites; OR = 1.19, 95% CI = 0.78-1.80, P = 0.42 for Asians). In summary, the catalase C-262T polymorphism may be a risk factor for cancer with cancer type-specific effects. Further studies should be performed to confirm these findings.

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.

Polymorphisms in metabolism/antioxidant genes may mediate the effect of dietary intake on pancreatic cancer risk

OBJECTIVES

A source of variation for inconsistent dietary-pancreatic cancer associations may be individuals carrying constitutional metabolism/antioxidant gene variants that differentially benefit compared to homozygous individuals. Seventy-six tag single-nucleotide polymorphisms were genotyped in 13 candidate genes to test differential associations with pancreatic adenocarcinoma.

METHODS

A clinic-based case-control design was used to rapidly ascertain 251 cases and 970 frequency matched controls who provided blood samples and completed a 144-item food frequency questionnaire. Single-nucleotide polymorphisms were evaluated using a dominant genetic model and dietary categories split on controls' median intake. Logistic regression was used to calculate odds ratios and 95% confidence intervals, adjusted for potential confounders.

RESULTS

Significant increased associations (Bonferroni corrected P ≤ 0.0007) were observed for carriers of greater than or equal to 1 minor allele for rs3816257 (glucosidase, α; acid [GAA]) and lower intake of deep-yellow vegetables (1.90 [1.28-2.83]); and carriers of no minor allele for rs12807961 (catalase [CAT]) and high total grains intake (2.48 [1.50-4.09]), whereas those with greater than or equal to 1 minor allele had a decreasing slope (across grains). The reference group was no minor alleles with low dietary intake.

CONCLUSIONS

Interindividual variation in metabolism/antioxidant genes could interact with dietary intake to influence pancreatic cancer risk.

Overview on how oncogenic Kras promotes pancreatic carcinogenesis by inducing low intracellular ROS levels

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease without clearly known disease causes. Recent epidemiological and animal studies suggest that the supplementation of dietary antioxidants (e.g., vitamins C and E) decreases cancer risk, implying that increased reactive oxygen species (ROS) may play a role in pancreatic carcinogenesis. However, oncogenic Kras mutations (e.g., Kras^G12D), which are present in more than 90% of PDAC, have been proven to foster low intracellular ROS levels. Here, oncogenic Kras activates expression of a series of anti-oxidant genes via Nrf2 (nuclear factor, erythroid derived 2, like 2) and also mediates an unusual metabolic pathway of glutamine to generate NADPH. This can then be used as the reducing power for ROS detoxification, leading collectively to low ROS levels in pancreatic pre-neoplastic cells and in cancer cells. In adult stem cells and cancer stem cells, low ROS levels have been associated with the formation of a proliferation-permissive intracellular environment and with perseverance of self-renewal capacities. Therefore, it is conceivable that low intracellular ROS levels may contribute significantly to oncogenic Kras-mediated PDAC formation.

GPX1 gene Pro200Leu polymorphism, erythrocyte GPX activity, and cancer risk

A meta-analysis was conducted to assess the effect of glutathione peroxidase1 (GPX1) gene Pro200Leu (rs1050450) polymorphism on cancer risk. A comprehensive search was performed to identify all studies on the association of GPX1 gene Pro200Leu polymorphism with cancer risk. The fixed or random effect pooled measure was selected based on homogeneity test among studies. Heterogeneity among studies was evaluated using the I (2). Potential sources of between-study heterogeneity were explored by meta-regression and the sensitivity analysis. Publication bias was estimated using Egger's linear regression test. 35 published articles with 36 results were identified involving 16,920 cases and 19,946 controls. Results from the articles that both obeyed Hardy-Weinberg equilibrium in controls and met high quality design, showed no significant association of GPX1 gene Pro200Leu polymorphism with cancer risk in any of dominant (OR = 1.05, 95 %CI = 0.98-1.12), recessive (OR = 1.04 (0.95-1.13), and TT versus CC (OR = 1.05, 95 %CI = 0.97-1.15) models, and the findings were consistent considering the stratified analysis by cancer type. However, multivariate-adjusted ORs from articles that both obeyed Hardy-Weinberg equilibrium in controls and met high quality design, showed a significant association considering dominant (OR = 1.22, 95 %CI = 1.06-1.41), TT versus CC (OR = 1.16, 95 %CI = 1.02-1.32) models, and a marginally significant association was found considering TC versus CC (OR = 1.11, 95 %CI = 0.99-1.25) model. And compared with the CC genotype, the erythrocyte GPX activity was significantly lower for TT genotype: the standardized mean difference (SMD) = -0.37, 95 %CI = (-0.624, -0.118), and CT genotype: SMD = -0.19, 95 %CI = (-0.37, -0.002). The association of GPX1 gene Pro200Leu polymorphism with cancer risk might be influenced by confounders.

Associations of GSTM1 and GSTT1 polymorphisms with pancreatic cancer risk: evidence from a meta-analysis

Glutathione S-transferases (GSTs), including glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1), are multifunctional enzymes which play vital roles in the detoxification of a variety of carcinogens. The genetic polymorphisms of GSTM1 and GSTT1 have been implicated in pancreatic cancer risk, but the results of published studies remain conflicting. Thus, a meta-analysis was conducted to estimate the effect of GSTM1 and GSTT1 polymorphisms on the risk of developing pancreatic cancer. A comprehensive search was performed in the PubMed, Embase, Web of Science, and Wanfang databases to identify the available studies on the associations of GSTM1 and GSTT1 polymorphisms with pancreatic cancer risk. The pooled odds ratio (OR) with its corresponding 95 % confidence interval (95 % CI) was used to estimate the associations. Stratified analyses by ethnicity and sensitivity analyses were performed to further identify the relationships. Overall, the null genotype of GSTT1 was associated with an increased risk of pancreatic cancer (OR = 1.61, 95 % CI 1.06-2.44, P OR = 0.025), but similar association was not found between the null genotype of GSTM1 and pancreatic cancer risk. Besides, a significant association of GSTT1 polymorphism with pancreatic cancer risk was identified in Asians (OR = 2.58, 95 % CI 1.67-3.98, P OR < 0.001), but not in Caucasians (OR = 1.16, 95 % CI 0.94-1.43, P OR = 0.170). Sensitivity analyses by sequential omission of individual study confirmed the stability of our results. Meta-analysis of available data thus far shows that the null genotype of GSTT1 is a risk factor for pancreatic cancer, particularly in the Asian population. The currently available data are not sufficient enough to identify the association between the GSTM1 polymorphism and pancreatic cancer risk.

Catalase polymorphisms and metabolic diseases

PURPOSE OF REVIEW

This review summarizes our current understanding of the implication of catalase polymorphisms in the occurrence, control and comorbidities of metabolic diseases.

RECENT FINDINGS

Whatever impaired glucose tolerance, insulin resistance on diabetes and whatever their occurrence or implications, the studies taken together converge toward the hypothesis that catalase polymorphisms play a role in glucose disorders. -262C/T and -844A>G single nucleotide polymorphisms are associated to hypertension susceptibility and/or onset. Concerning dyslipidemia, very recent studies requiring confirmation report a -262C/T implication. Finally, a role of catalase polymorphisms in bone metabolism is described.

SUMMARY

Plethora of studies on catalase SNPs and their link with diseases exist. It is now clear that genetic variations in the catalase gene and its promoter are putative risk factors for metabolic disease. The question of how these polymorphisms actively play a role in various metabolisms remains unanswered. Further functional studies are required in order to gain a deeper insight into the direct role of catalase.

GPx-1 polymorphism (rs1050450) contributes to tumor susceptibility: evidence from meta-analysis

PURPOSE

Accumulating evidences implicate the selenium-containing cytosolic glutathione peroxidase, GPx-1, as a determinant of cancer risk and a mediator of the chemopreventive properties of selenium. Since the identification of a well-characterized functional polymorphism named Pro198Leu (rs1050450 C>T) in GPx-1, abundant studies have evaluated the association between Pro198Leu polymorphism and tumor risk in diverse population. But, the available results are conflicting.

METHODS

To derive a more precise estimation, we performed a meta-analysis based on 14,372 cases with different tumor types and 18,081 controls from 31 published case-control studies. Published literature from PubMed was retrieved. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to estimate the strength of the association.

RESULTS

Overall, the results indicated that individuals who carried variant Leu allele (Pro/Leu and Leu/Leu) were associated with an increased cancer risk [odds ratio (OR) = 1.12, 95% confidence interval (CI) = 1.02-1.23] in a dominant genetic model. In further subgroup analyses, the increased risk of cancer was observed in subgroup of Asians and sample size more than 500 subjects.

CONCLUSION

These results suggest that the GPx-1 Pro198Leo polymorphism contributes to cancer susceptibility through a disturbed antioxidant balance.

Genetic polymorphisms of superoxide dismutases, catalase, and glutathione peroxidase in age-related cataract

PURPOSE

The antioxidant enzymes pathway is considered the most important pathway involved in the repair of reactive oxygen species (ROS)-induced damage. Therefore, we investigate the possible association between polymorphisms of Cu/Zn superoxide dismutase (SOD1), catalase (CAT), and glutathione peroxidase (GPX) genes and age -related cataract development.

METHODS

The study included 415 cataract patients (121 patients with cortical, 109 with nuclear, 59 with posterior subcapsular, and 126 with mixed type) and 386 healthy control group of similar age. Genotyping of SOD1-251A/G, CAT-21A/T, and GPX1-198C/T was done by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) method. Differences in the frequencies were estimated using the χ(2) test and risk was estimated with an unconditional logistic regression after adjusting for age and gender.

RESULTS

SOD1 G/G genotype frequency was significantly higher in cataract patients (p=0.012, OR=1.642, 95% CI=1.129-2.389). SOD1 A/A genotypes (p=0.001, OR=0.613, 95% CI=0.461-0.817) seem to have a protective role against cataract, and the G allele (p=0.001, OR=1.479, 95% CI=1.208-1.810) plays a dangeous effect against in the development of cataract. In CAT-21A/T and GPX1-198C/T polymorphisms, there were no significant differences in the variant homozygous frequencies in patients compared to controls (p=0.226, OR=1.358, 95% CI=0.839-2.199; p=0.521, OR=1.205, 95% CI=0.726-2.001, respectively). Stratification by the subtypes revealed that association between SOD polymorphism and cataract was in cortical and mixed type cataract. The genotype frequency of the GG and AA of SOD1-251A/G was significantly different in cortical and mixed type cataract group (p=0.031; OR: 1.805, 95% CI: 1.076-3.026; p=0.002; OR: 2.229, 95% CI: 1.364-3.645; p=0.026; OR: 0.608, 95% CI: 0.396-0.933; p=0.001; OR: 0.474, 95% CI: 0.305-0.734, respectively) compared to healthy controls.

CONCLUSIONS

Results suggest that the G/G genotype of the SOD1-251A/G polymorphism may be associated with an increased risk of cataract. However, in CAT-21A/T and GPX1-198C/T polymorphisms, there were no significant differences in the variant homozygous frequencies in patients compared to controls.

Sequence variants in antioxidant defense and DNA repair genes, dietary antioxidants, and pancreatic cancer risk

To investigate whether polymorphisms in genes related to oxidative stress act alone or in combination with antioxidants to modulate pancreatic cancer risk. Cases (n=189), ages ≥ 20 years, were ascertained in 1994-1998 from all hospitals in the Twin Cities and the Mayo Clinic. Controls (n=486) were randomly selected from the general population and frequency matched to cases by age and sex. After adjustment for confounders, individuals who were homozygous or heterozygous for the variant allele of SOD2 polymorphism (Ala16Val, rs4880) experienced a 43% lower risk than those who were homozygous for the wild-type allele [OR (95% CI): 0.57 (0.37, 0.89)]. Conversely, an increased risk was observed for the variant allele of hOGG1 polymorphism (Ser326Cys, rs1052133) compared with the wild-type allele [OR (95% CI) for Ser/Cys or Cys/Cys vs. Ser/Ser: 1.57 (1.04, 2.39)]. The protective effect of the variant allele of SOD2 was more pronounced among subjects with a low dietary intake (<median) of lutein/ zeaxanthin, lycopene, α-carotene, and α-tocopherol [OR (95% CI): 0.46 (0.27, 0.81), 0.42 (0.23, 0.75), 0.47 (0.26, 0.85), and 0.48 (0.27, 0.87), respectively]. Individual variations in the capacity to defend against oxidative stress and to repair oxidative DNA damage influence pancreatic cancer risk, and some of these genetic effects are modified by dietary antioxidants.

Glucose metabolism gene variants modulate the risk of pancreatic cancer

Long-term type 2 diabetes is a known risk factor for pancreatic cancer (PC). We hypothesized that genetic variants in glucose metabolism modify individual susceptibility to PC, especially those associated with diabetes. We retrospectively genotyped 26 single-nucleotide polymorphisms of 5 glucose metabolism genes: glucokinase (GCK), glutamine-fructose-6-phosphate transaminase 1 (GFPT1), glucose phosphate isomerase (GPI), hexokinase 2 (HK2), and O-linked N-acetylglucosamine transferase (OGT) in a case-control study of PC conducted at MD Anderson during 2004 to 2010. Initial genotyping was conducted in 706 patients with PC and 706 cancer-free controls by using the Sequenom method. A HK2 genotype (R844K) with low frequency of homozygous variant was further examined in additional 948 patients and 476 controls. In the combined set of 1,654 cases and 1,182 controls, we showed a significant association of the HK2 R844K GA/AA genotype with reduced PC risk (OR = 0.78; 95% CI, 0.64-0.94; P = 0.009) and a significant interaction with diabetes (P(interaction) < 0.001). The HK2 R844K GA/AA genotype was associated with a reduced risk of PC among nondiabetic individuals (OR = 0.68; 95% CI, 0.56-0.83) but with increased risk among diabetic patients (OR = 3.69; 95% CI, 2.34-5.82). These risk associations remained statistically significant when the analysis was restricted to whites or after exclusion of recent onset diabetes. No significant main effect of other genes or significant interaction of genotype with other risk factors was observed. The findings show a potential role of HK2 gene, alone or in interaction with diabetes, in modifying the risk of PC.