DNA adducts, genetic polymorphisms, and K-ras mutation in human pancreatic cancer

Dissecting the multifaceted roles of autophagy in cancer initiation, growth, and metastasis: from molecular mechanisms to therapeutic applications

Autophagy is a cytoplasmic defense mechanism that cells use to break and reprocess their intracellular components. This utilization of autophagy is regarded as a savior in nutrient-deficient and other stressful conditions. Hence, autophagy keeps contact with and responds to miscellaneous cellular tensions and diverse pathways of signal transductions, such as growth signaling and cellular death. Importantly, autophagy is regarded as an effective tumor suppressor because regular autophagic breakdown is essential for cellular maintenance and minimizing cellular damage. However, paradoxically, autophagy has also been observed to promote the events of malignancies. This review discussed the dual role of autophagy in cancer, emphasizing its influence on tumor survival and progression. Possessing such a dual contribution to the malignant establishment, the prevention of autophagy can potentially advocate for the advancement of malignant transformation. In contrast, for the context of the instituted tumor, the agents of preventing autophagy potently inhibit the advancement of the tumor. Key regulators, including calpain 1, mTORC1, and AMPK, modulate autophagy in response to nutritional conditions and stress. Oncogenic mutations like RAS and B-RAF underscore autophagy's pivotal role in cancer development. The review also delves into autophagy's context-dependent roles in tumorigenesis, metastasis, and the tumor microenvironment (TME). It also discusses the therapeutic effectiveness of autophagy for several cancers. The recent implication of autophagy in the control of both innate and antibody-mediated immune systems made it a center of attention to evaluating its role concerning tumor antigens and treatments of cancer.

An Extensive Review on Preclinical and Clinical Trials of Oncolytic Viruses Therapy for Pancreatic Cancer

Chemotherapy resistance and peculiar tumor microenvironment, which diminish or mitigate the effects of therapies, make pancreatic cancer one of the deadliest malignancies to manage and treat. Advanced immunotherapies are under consideration intending to ameliorate the overall patient survival rate in pancreatic cancer. Oncolytic viruses therapy is a new type of immunotherapy in which a virus after infecting and lysis the cancer cell induces/activates patients’ immune response by releasing tumor antigen in the blood. The current review covers the pathways and molecular ablation that take place in pancreatic cancer cells. It also unfolds the extensive preclinical and clinical trial studies of oncolytic viruses performed and/or undergoing to design an efficacious therapy against pancreatic cancer.

Anti-human serum albumin autoantibody may be involved in the pathogenesis of autoimmune bullous skin diseases

Although effective immunological diagnostic systems for autoimmune bullous skin diseases (AIBD) have been established, there are still unidentified cutaneous autoantigens. The purpose of this study is to investigative whether anti-human serum albumin (HSA) autoantibodies exist in AIBD sera and their potential pathogenesis. By immunoprecipitation-immunoblotting, immunofluorescence assay, anti-HSA autoantibodies could be detected in AIBD sera; by ELISAs, positive rates of AIBD sera for IgG and IgA anti-HSA autoantibodies were 29% and 34%, respectively. The IgG anti-HSA autoantibodies in ABID sera recognized a number of HSA antigen epitopes and therefore a polyclonal antibody against HSA were next employed to study its pathogenesis. In vitro cell and tissue culture models, anti-HSA antibody could influence DNA damage-related signaling proteins, via activation of phospho-p38 signaling pathway. This is the first report that an autoantibody may influence DNA damage-related signaling proteins. Statistical analyses also proved that anti-HSA autoantibodies were positively correlated with various known autoantibodies and clinical features of ABID patients. In summary, IgG and IgA autoantibodies to HSA may have diagnosis values for AIBD. DNA damage-related signaling proteins might be involved in the pathogenic role of anti-HSA autoantibodies in AIBD. Phospho-p38 signaling pathway is a potential target for treatment of AIBD positive for serum anti-HSA autoantibodies.

A Summary of In Vitro and In Vivo Studies Evaluating the Impact of E-Cigarette Exposure on Living Organisms and the Environment

Worldwide use of electronic cigarettes has been rapidly expanding over recent years, but the long-term effect of e-cigarette vapor exposure on human health and environment is not well established; however, its mechanism of action entails the production of reactive oxygen species and trace metals, and the exacerbation of inflammation, which are associated with potential cytotoxicity and genotoxicity. The present study examines the effects of selected liquid chemicals used in e-cigarettes, such as propylene glycol/vegetable glycerin, nicotine and flavorings, on living organisms; the data collected indicates that exposure to e-cigarette liquid has potentially detrimental effects on cells in vitro, and on animals and humans in vivo. While e-liquid exposure can adversely influence the physiology of living organisms, vaping is recommended as an alternative for tobacco smoking. The study also compares the impact of e-cigarette liquid exposure and traditional cigarette smoke on organisms and the environmental impact. The environmental influence of e-cigarette use is closely connected with the emission of airborne particulate matter, suggesting the possibility of passive smoking. The obtained data provides an insight into the impact of nicotine delivery systems on living organisms and the environment.

Construction of a self-directed replication system for label-free and real-time sensing of repair glycosylases with zero background

Genomic DNA damage and repair are involved in multiple fundamental biological processes, including metabolism, disease, and aging. Inspired by the natural repair mechanism in vivo, we demonstrate for the first time the construction of a self-directed replication system for label-free and real-time sensing of repair glycosylases with zero background. The presence of DNA glycosylase can catalyze the excision repair of the damaged base, successively autostarting the self-directed replication through recycling polymerization extension and strand-displacement DNA synthesis for the generation of exponentially amplified dsDNAs. The resultant dsDNA products can be label-free and real-time monitored with SYBR Green I as the fluorescent indicator. Owing to the high efficiency of self-directed exponential replication and the absolute zero background resulting from the efficient inhibition of nonspecific amplification induced by multiple primer-dependent amplification, this strategy exhibits high sensitivity with a detection limit of 1 × 10-8 U μL-1 in vitro and 1 cell in vivo, and it can be further used to screen inhibitors, quantify DNA glycosylase from diverse cancer cells, and even monitor various repair enzymes by simply changing the specific damaged base in the DNA template. Importantly, this assay can be performed in a label-free, real-time and isothermal manner with the involvement of only a single type of polymerase, providing a simple, robust and universal platform for repair enzyme-related biomedical research and clinical therapeutics.

The Diverse Involvement of Cigarette Smoking in Pancreatic Cancer Development and Prognosis

Despite extensive research in the pathogenesis, early detection, and therapeutic approaches of pancreatic ductal adenocarcinoma (PDAC), it remains a devastating and incurable disease. As the global incidence and prevalence of PDAC continue to rise, there is a pressing need to place strong emphasis on its prevention. Although it is widely recognized that cigarette smoking, a potentially modifiable risk factor, has been linked to PDAC development, its contribution to prognosis is still uncertain. Moreover, the mechanistic pathways of PDAC progression secondary to smoking are various and lack a summative narration. Herein, we update and summarize the direct and indirect roles cigarette smoking plays on PDAC development, review literature to conclude the impact cigarette smoking has on prognosis, and postulate a comprehensive mechanism for cigarette smoking-induced PDAC.

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.

Pragmatic and rapid analysis of carbonyl, oxidation and chlorination nucleoside-adducts in murine tissue by UPLC-ESI-MS/MS

Nucleoside-adduct analysis by liquid chromatography mass spectrometry is a powerful tool in genotoxicity studies. Efforts to date have quantified an impressive array of DNA damage products, although methodological diversity suggests quantification is still a challenging task. For example, inadequate co-examination of normal nucleosides, cumbersome sample preparation and large DNA requirements were identified to be recurring issues. A six-minute ultra-performance liquid chromatography method is presented which adequately separates seven candidate nucleoside-adducts from the four unmodified nucleosides. The method was sensitive to 1 adduct per 10⁸ normal bases with 20 µg DNA input for most targets. The method was shown to be accurate (81-119% across quintuplets of six tissue types) and precise (relative standard deviation 4-13%). The fast method time facilitated a second quantitation for normal nucleosides at an appropriate dilution, allowing DNA damage concentrations to be contextualised accurately sample-to-sample. From DNA samples, the analytical processing time was < 8 h, and 96 samples can easily be prepared in a day. The method was used to quantify carbonyl, chloro- and oxo- adducts in murine tissue samples.

Pancreatic Cancer is Associated with Peripheral Leukocyte Oxidative DNA Damage

Background:

DNA damage accumulation has been linked to the cancer phenotype. The purpose of this study was to compare the levels of DNA base 8-hydroxy-2’-deoxyguanosine (8-OHdG) and C-reactive protein (CRP) inflammatory markers in healthy controls and pancreatic cancer patients from a hospital-based case-control study.

Materials and Methods:

Fifty-five pancreatic cancer patients and 55 healthy controls were enrolled from a pool of patients referred to the Endoscopic Ultrasound (EUS) center. Analysis of DNA content of peripheral blood cells was conducted for 8-OHdG with the 32P-postlabelling assay. Serum CRP levels were measured by high-sensitivity assays and demographic data for comparison were collected from individual medical records.

Results:

The group of cases showed significant increased median (IQR) 8-OHdG DNA adducts/106 nucleotides and CRP compared to the controls (208.8 (138.0-340.8) vs 121.8 (57.7-194.8) RAL value; P<0.001) and (3.5 (1.5-8.6) vs 0.5 (0.2-1.5) mg/L P<0.001). A number of conditional regression models confirmed associations of pancreatic cancer with oxidative DNA damage in peripheral leukocytes.

Conclusions:

Our findings suggest the importance of leukocyte 8-OHdG adducts as an indicator for systemic oxidative DNA damage in pancreatic cancer patients. In addition to increase in the CRP inflammatory marker, this supports the impact of inflammation in the occurrence of pancreatic cancer as well as inflammatory responses during cancer development.

Targeting reactive oxygen species in development and progression of pancreatic cancer

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDA) is characterized by expression of oncogenic KRas which drives all aspects of tumorigenesis. Oncogenic KRas induces the formation of reactive oxygen species (ROS) which have been implicated in initiation and progression of PDA. To facilitate tumor promoting levels and to avoid oncogene-induced senescence or cytotoxicity, ROS homeostasis in PDA cells is balanced by additional up-regulation of antioxidant systems. Areas covered: We examine the sources of ROS in PDA, the mechanisms by which ROS homeostasis is maintained, and the biological consequences of ROS in PDA. Additionally, we discuss the potential mechanisms for targeting ROS homoeostasis as a point of therapeutic intervention. An extensive review of the relevant literature as it relates to the topic was conducted using PubMed. Expert commentary: Even though oncogenic mutations in the KRAS gene have been detected in over 95% of human pancreatic adenocarcinoma, targeting its gene product, KRas, has been difficult. The dependency of PDA cells on balancing ROS homeostasis could be an angle for new prevention or treatment strategies. These include use of antioxidants to prevent formation or progression of precancerous lesions, or methods to increase ROS in tumor cells to toxic levels.

Assessment of epidermal growth factor receptor mutation/copy number and K-ras mutation in esophageal cancer

BACKGROUND

The molecular status of epidermal growth factor receptor (EGFR) in esophageal cancer has not been well elucidated. The purpose of the study was to investigate the prevalence of EGFR and K-ras mutation, and EGFR gene copy number status as well as its association with clinicopathologic characteristics, and also to identify the prognostic value of EGFR gene copy number in esophageal cancer.

METHODS

EGFR mutation in exon 19/exon 21 and K-ras mutation in codon 12/codon 13 were detected by real-time PCR method, while EGFR gene copy number status was analyzed by fluorescent in situ hybridization (FISH). EGFR gene amplification and high polysomy were defined as high EGFR gene copy number status (FISH-positive), and all else were defined as low EGFR gene copy number status (FISH-negative). The relationship between EGFR gene copy number status and clinicpathologic characteristics was analyzed. Kaplan-Meier method and Cox proportional hazards regression model were employed to evaluate the effects of EGFR gene copy number status on the patients' survival.

RESULTS

A total of 57 esophageal squamous cell carcinoma (ESCC) patients and 9 esophageal adenocarcinoma (EADC) patients were enrolled in the study. EGFR mutation was identified in one patient who was diagnosed as ESCC with stage IIIC disease. K-ras mutation was identified in one patient who was diagnosed as EADC. In all, 34 of 66 (51.5%) samples were detected as FISH-positive, which includes 30 ESCC and 4 EADC tumor samples. The correlation analysis showed that FISH-positive was significantly associated with the tumor stage (P=0.019) and lymph node metastasis (P=0.005) in esophageal cancer patients, and FISH-positive was also significantly associated with the tumor stage (P=0.007) and lymph node metastasis (P=0.008) in ESCC patients. Cox regression analysis showed that high EGFR gene copy number was not a significant predictor of a poor outcome for esophageal cancer patients (P=0.251) or for ESCC patients (P=0.092), but esophageal cancer patients or ESCC patients with low EGFR gene copy number may have longer survival than those with high EGFR gene copy number according to the survival curve trends.

CONCLUSIONS

The results indicated that EGFR or K-ras mutation was rare in esophageal cancer, but high EGFR gene copy number is frequent, and correlated with advanced pathologic stage and more number of the metastatic regional lymph nodes, especially in ESCC. In addition, high EGFR gene copy number is likely to have a deleterious effect on prognosis of esophageal cancer patients or ESCC patients, although no statistical significance was reached in the study.

Keap1 expression has independent prognostic value in pancreatic adenocarcinomas

BACKGROUND

Oxidative stress and redox-regulating enzymes may potentially accelerate pancreatic carcinogenesis and also affect chemoresistance. Recently major antioxidant response regulator NF-E2-related factor 2 (Nrf2) has been linked to poor prognosis in pancreatic cancer. Nrf2 activity is strictly regulated by oxidative stress sensor Kelch-like ECH-associated protein 1 (Keap1). Oxidative DNA damage can be estimated e.g. by 8-hydroxy-2'-deoxyguanosine (8-OHdG) expression. The aim of this study was to evaluate the expression and possible prognostic role of Keap1 and 8-OHdG in pancreatic cancer.

METHODS

We assessed immunohistochemically the expression of 8-OHdG and Keap1 in precisely characterized material of 69 pancreatic adenocarcinoma patients.

RESULTS

Nuclear 8-OHdG associated with cytoplasmic Keap1 expression (p = 0.031) and was overexpressed in patients with smaller tumors (p = 0.016) and in tumors without lymph node involvement (p = 0.051). Cytoplasmic 8-OHdG expression associated with higher differentiation (p = 0.023). Cytoplasmic Keap1 immunostaining associated with N0-staging (p = 0.0009) and the absence of distant metastases (p = 0.018). Membranous Keap1 associated with longer relapse-free survival (p = 0.041) and pancreatic cancer-specific survival (median survival 14 vs. 32 months; p = 0.029) and was in multivariate analysis an independent prognostic factor of pancreatic cancer-related death (HR 2.66, 95%CI 1.23-5.75).

CONCLUSIONS

Oxidative stress and main redox regulators may participate in pancreatic carcinogenesis and Keap1 appears as a promising prognostic factor in pancreatic cancer. Future studies should also concentrate on potential link between redox regulation and chemoresistance in pancreatic cancer.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/4220521801406476.

Association between alcohol consumption and pancreatic cancer risk: a case-control study

Purpose

Evidence is inconsistent regarding alcohol and pancreatic cancer risk, although heavy drinking may increase risk.

Methods

A population-based case-control study was conducted using 345 pancreas cancer cases diagnosed 2011–2012 and 1,285 frequency-matched controls from Ontario, Canada. Logistic regression was used to evaluate alcohol consumption and pancreatic cancer risk; data was also stratified by sex and smoking status to assess interaction.

Results

Alcohol consumption was not associated with pancreatic cancer risk (age-adjusted odds ratio=0.78, 95% CI: 0.58, 1.05 for 1 - 3 drinks/week; age-adjusted odds ratio=0.86, 95% CI: 0.63, 1.17 for 4 - 20 drinks/week), however there was a non-significant increased risk for heavy drinkers consuming ≥21 drinks/week (age-adjusted odds ratio=1.35, 95% CI: 0.81, 2.27). Cigarette smoking modified the alcohol-cancer relationship; among current smokers, heavy alcohol consumption was associated with a significantly increased pancreatic cancer risk (age-adjusted odds ratio=4.04, 95% CI: 1.58, 10.37), whereas this significant association with heavy drinking was not observed among non-smokers (age-adjusted odds ratio=2.01, 95% CI: 0.50, 8.18). Furthermore, light – moderate alcohol intake was associated with increased pancreas cancer risk among current smokers.

Conclusions

While alcohol was not significantly associated with pancreatic cancer risk, smoking status modified this relationship such that among current smokers, alcohol intake was associated with a greater than two-fold increased risk of pancreatic cancer. The results should be interpreted with caution due to small sample sizes within subgroups and correction for multiple comparisons should be considered. These findings should be replicated in larger studies where more precise estimates of risk can be obtained.

Glutathione S-transferase M1 and glutathione S-transferase T1 genotype in chronic pancreatitis: a meta-analysis

OBJECTIVE

A meta-analysis to determine the association between chronic pancreatitis and glutathione-S transferase (GST) mu 1 (GSTM1) and theta 1 (GSTT1) deletions.

METHODS

Case-control studies concerning the relationship between chronic pancreatitis and GSTM1 or GSTT1 deletions were identified (up to October 2013). Meta-analyses of the association between GSTM1 and GSTT1 genotype and chronic pancreatitis or alcoholic chronic pancreatitis (ACP) were performed.

RESULTS

Seven studies were included in the meta-analysis (650 patients/1382 controls for GSTM1 and 536 patients/1304 controls for GSTT1). There were no significant relationships between GSTM1/GSTT1 and chronic pancreatitis or GSTT1 and ACP. There was a significant association between GSTM1 null genotype and ACP (odds ratio 1.16, 95% confidence intervals 1.03, 1.30).

CONCLUSION

The GSTM1 null genotype was significantly associated with ACP risk.

Elevated DNA damage response in pancreatic cancer

Pancreatic cancer is one of the most aggressive and intractable human malignant tumors and a leading cause of cancer-related death across the world, with incidence equaling mortality. Because of the extremely high malignance, this disease is usually diagnosed at its advanced stage and recurs even after surgical excision. Pancreatic adenocarcinoma is generally thought to arise from pathological changes of pancreatic duct, and the pancreatic ductal adenocarcinoma accounts for more than 90 % of malignant neoplasms of the pancreas. To date, scientists have revealed several risk factors for pancreatic cancer, including smoking, family history, and aging. However, the underlying molecular mechanism remains unclear. Meanwhile, more mutations of DNA damage response factors have been identified in familial pancreatic cancers, implying a potential link between DNA damage and pancreatic cancer. DNA damage is a recurring phenomenon in our bodies which could be induced by exogenous agents and endogenous metabolism. Accumulated DNA lesions cause genomic instability which eventually results in tumorigenesis. In this study, we showed obvious DNA damages existed in human pancreatic cancer, which activated DNA damage response and the DNA repair pathway including ataxia-telangiectasia mutated, DNA-PK, CHK1, and CHK2. The persistent DNA damage in pancreatic tissue may be the source for its tumorigenesis.

hOGG1 Ser326Cys polymorphism and risk of hepatocellular carcinoma among East Asians: a meta-analysis

Background

The hOGG1 gene encodes a DNA glycosylase enzyme responsible for DNA repair. The Ser326Cys polymorphism in this gene may influence its repair ability and thus plays a role in carcinogenesis. Several case-control studies have been conducted on this polymorphism and its relationship with the risk of hepatocellular carcinoma (HCC) among East Asians. However, their results are inconsistent.

Methods

We performed a meta-analysis of published case-control studies assessing the association of the hOGG1 Ser326Cys polymorphism with HCC risk among East Asians. PubMed, EMBASE, SCI, BIOSIS, CNKI and WanFang databases were searched. A random-effect model was used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs). Analyses were conducted for additive, dominant and recessive genetic models.

Results

Eight studies were identified involving 2369 cases and 2442 controls assessing the association of the hOGG1 Ser326Cys polymorphism with HCC risk among East Asians. Applying a dominant genetic model, only in the Chinese population, the Cys allele was significantly associated with increased risk of HCC (OR 1.56, 95% CI 1.12–2.17). However, two studies influenced this finding according to sensitivity analysis. Furthermore, considerable heterogeneity and bias existed among Chinese studies.

Conclusion

There is limited evidence to support that the hOGG1 Ser326Cys polymorphism is associated with HCC risk among East Asians. Well-designed and large-sized studies are required to determine this relationship.

Active and passive smoking and risk of death from pancreatic cancer: findings from the Japan Collaborative Cohort Study

BACKGROUND

There is uncertainty in the risk of pancreatic cancer with particular aspects of smoking, such as a dose-response relationship and cumulative amount, in Japanese men and women. Very few studies have addressed the role of passive smoking in pancreatic cancer among Japanese women.

METHODS

We examined the association between active or passive smoking and the risk of death from pancreatic cancer using data from the Japan Collaborative Cohort Study. The cohort participants (46,395 men and 64,190 women) were followed-up for mortality from baseline (1988-1990) through December 31, 2009. Cox proportional hazards regression models were used to estimate relative risks (RR) and 95% confidence intervals (CI).

RESULTS

During follow-up, we recorded 611 pancreatic cancer deaths. After adjustment for potential confounding factors, current smokers had a significantly increased risk of death from pancreatic cancer compared with non-smokers, with an RR of 1.70 (95% CI: 1.33-2.19). The risk of death from pancreatic cancer significantly increased with increasing numbers of cigarettes smoked per day. Exposure to environmental tobacco smoke (ETS) in public spaces was not associated with risk of death from pancreatic cancer. The RR for women who reported ETS exposure was 1.20 (95% CI: 0.87-1.67). Women exposed to ETS during childhood or adolescence had 1.21-fold increased risk, but the association was statistically insignificant.

CONCLUSIONS

Cigarette smoking is associated with an approximately 70% increase in the risk of death from pancreatic cancer. Further studies with improved exposure assessment are needed to better quantify the association between passive smoking and pancreatic cancer.

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.

Interplay between smoking-induced genotoxicity and altered signaling in pancreatic carcinogenesis

Despite continuous research efforts directed at early diagnosis and treatment of pancreatic cancer (PC), the status of patients affected by this deadly malignancy remains dismal. Its notoriety with regard to lack of early diagnosis and resistance to the current chemotherapeutics is due to accumulating signaling abnormalities. Hoarding experimental and epidemiological evidences have established a direct correlation between cigarette smoking and PC risk. The cancer initiating/promoting nature of cigarette smoke can be attributed to its various constituents including nicotine, which is the major psychoactive component, and several other toxic constituents, such as nitrosamines, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, and polycyclic aromatic hydrocarbons. These predominant smoke-constituents initiate a series of oncogenic events facilitating epigenetic alterations, self-sufficiency in growth signals, evasion of apoptosis, sustained angiogenesis, and metastasis. A better understanding of the molecular mechanisms underpinning these events is crucial for the prevention and therapeutic intervention against PC. This review presents various interconnected signal transduction cascades, the smoking-mediated genotoxicity, and genetic polymorphisms influencing the susceptibility for smoking-mediated PC development by modulating pivotal biological aspects such as cell defense/tumor suppression, inflammation, DNA repair, as well as tobacco-carcinogen metabolization. Additionally, it provides a large perspective toward tumor biology and the therapeutic approaches against PC by targeting one or several steps of smoking-mediated signaling cascades.

Relationships between single nucleotide polymorphisms of antioxidant enzymes and disease

The presence and progression of numerous diseases have been linked to deficiencies in antioxidant systems. The relationships between single nucleotide polymorphisms (SNPs) arising from specific antioxidant enzymes and diseases associated with elevated oxidative stress have been studied with the rationale that they may be useful in screening for diseases. The purpose of this narrative review is to analyse evidence from these studies. The antioxidant enzyme SNPs selected for analysis are based on those most frequently investigated in relation to diseases in humans: superoxide dismutase (SOD2) Ala16Val (80 studies), glutathione peroxidise (GPx1) Pro197Leu (24 studies) and catalase C-262T (22 studies). Although the majority of evidence supports associations between the SOD2 Ala16Val SNP and diseases such as breast, prostate and lung cancers, diabetes and cardiovascular disease, the presence of the SOD2 Ala16Val SNP confers only a small, clinically insignificant reduction (if any) in the risk of these diseases. Other diseases such as bladder cancer, liver disease, nervous system pathologies and asthma have not been consistently related to this SOD SNP genotype. The GPx1 Pro197Leu and catalase C-262T SNP genotypes have been associated with breast cancer, but only in a small number of studies. Thus, currently available evidence suggests antioxidant enzyme SNP genotypes are not useful for screening for diseases in humans.

Repair of oxidative DNA damage is delayed in the Ser326Cys polymorphic variant of the base excision repair protein OGG1

Gene-environment interactions influence an individual's risk of disease development. A common human 8-oxoguanine DNA glycosylase 1 (OGG1) variant, Cys326-hOGG1, has been associated with increased cancer risk. Evidence suggests that this is due to reduced repair ability, particularly under oxidising conditions but the underlying mechanism is poorly understood. Oxidising conditions may arise due to internal cellular processes, such as inflammation or external chemical or radiation exposure. To investigate wild-type and variant OGG1 regulation and activity under oxidising conditions, we generated mOgg1 (-/-) null mouse embryonic fibroblasts cells stably expressing Ser326- and Cys326-hOGG1 and measured activity, gene expression, protein expression and localisation following treatment with the glutathione-depleting compound L-buthionine-S-sulfoximine (BSO). Assessment of OGG1 activity using a 7,8-dihydro-8-oxodeoxyguanine (8-oxo dG) containing molecular beacon demonstrated that the activity of both Ser326- and Cys326-hOGG1 was increased following oxidative treatment but with different kinetics. Peak activity of Ser326-hOGG1 occurred 12 h prior to that of Cys326-hOGG1. In both variants, the increased activity was not associated with any gene expression or protein increase or change in protein localisation. These findings suggest that up-regulation of OGG1 activity in response to BSO-induced oxidative stress is via post-transcriptional regulation and provide further evidence for impaired Cys326-hOGG1 repair ability under conditions of oxidative stress. This may have important implications for increased mutation frequency resulting from increased oxidative stress in individuals homozygous for the Cys326 hOGG1 allele.

8-oxo-7,8-dihydro-2'-deoxyguanosine as a biomarker of oxidative damage in oesophageal cancer patients: lack of association with antioxidant vitamins and polymorphism of hOGG1 and GST

Background

The present report was designed to investigate the origins of elevated oxidative stress measured in cancer patients in our previous work related to a case-control study (17 cases, 43 controls) on oesophageal cancers. The aim was to characterize the relationship between the levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), antioxidant vitamins and genetic susceptibility.

Methods

8-oxodG was analysed in peripheral blood mononuclear cells (PBMCs) by High Performance Liquid Chromatography with Electrochemical Detection (HPLC-ED). Analysis of gene polymorphisms in GSTM1 and GSTT1 was performed by multiplex PCR and in GSTP1 and hOGG1 by a PCR-RFLP method. Reversed-phase HPLC with UV detection at 294 nm was used to measure vitamins A and E in serum from the same blood samples.

Results

We observed that in our combined population (cases and control, n = 60), there was no statistically significant correlation between the levels of 8-oxodG and (i) the serum concentration of antioxidant vitamins, vitamin A (P = 0.290) or vitamin E (P = 0.813), or (ii) the incidence of the Ser326Cys polymorphic variant (P = 0.637) of the hOGG1 gene. Also, the levels of 8-oxodG were not significantly associated with polymorphisms in metabolite-detoxifying genes, such as GSTs, except for the positive correlation with Val/Val GST P1 allele (P < 0.0001).

Conclusions

The weakness of our cohort size notwithstanding, vitamins levels in serum and genetic polymorphisms in the hOGG1 or GST genes do not appear to be important modulators of 8-oxodG levels.

Clinical relevance of KRAS in human cancers

The KRAS gene (Ki-ras2 Kirsten rat sarcoma viral oncogene homolog) is an oncogene that encodes a small GTPase transductor protein called KRAS. KRAS is involved in the regulation of cell division as a result of its ability to relay external signals to the cell nucleus. Activating mutations in the KRAS gene impair the ability of the KRAS protein to switch between active and inactive states, leading to cell transformation and increased resistance to chemotherapy and biological therapies targeting epidermal growth factor receptors. This review highlights some of the features of the KRAS gene and the KRAS protein and summarizes current knowledge of the mechanism of KRAS gene regulation. It also underlines the importance of activating mutations in the KRAS gene in relation to carcinogenesis and their importance as diagnostic biomarkers, providing clues regarding human cancer patients' prognosis and indicating potential therapeutic approaches.

Analysis of 7,8-dihydro-8-oxo-2'-deoxyguanosine in cellular DNA during oxidative stress

Analysis of cellular 7,8-dihydro-8-oxo-2′-deoxyguanosine (8-oxo-dGuo) as a biomarker of oxidative DNA damage has been fraught with numerous methodological problems. This is primarily due to artifactual oxidation of dGuo that occurs during DNA isolation and hydrolysis. Therefore, it has become necessary to rely on using the comet assay, which is not necessarily specific for 8-oxo-dGuo. A highly specific and sensitive method based on immunoaffinity purification and stable isotope dilution liquid chromatography (LC)-multiple reaction monitoring (MRM)/mass spectrometry (MS) that avoids artifact formation has now been developed. Cellular DNA was isolated using cold DNAzol (a proprietary product that contains guanidine thiocyanate) instead of chaotropic- or phenol-based methodology. Chelex-treated buffers were used to prevent Fenton chemistry-mediated generation of reactive oxygen species (ROS) and artifactual oxidation of DNA bases. Deferoxamine was also added to all buffers in order to complex any residual transition metal ions remaining after Chelex treatment. The LC-MRM/MS method was used to determine that the basal 8-oxo-dGuo level in DNA from human bronchoalveolar H358 cells was 2.2 ± 0.4 8-oxo-dGuo/10⁷ dGuo (mean ± standard deviation) or 5.5 ± 1.0 8-oxo-dGuo/10⁸ nucleotides. Similar levels were observed in human lung adenocarcinoma A549 cells, mouse hepatoma Hepa-1c1c7 cells, and human HeLa cervical epithelial adenocarcinoma cells. These values are an order of magnitude lower than is typically reported for basal 8-oxo-dGuo levels in DNA as determined by other MS- or chromatography-based assays. H358 cells were treated with increasing concentrations of potassium bromate (KBrO₃) as a positive control or with the methylating agent methyl methanesulfonate (MMS) as a negative control. A linear dose−response for 8-oxo-dGuo formation (r² = 0.962) was obtained with increasing concentrations of KBrO₃ in the range of 0.05 mM to 2.50 mM. In contrast, no 8-oxo-dGuo was observed in H358 cell DNA after treatment with MMS. At low levels of oxidative DNA damage, there was an excellent correlation between a comet assay that measured DNA single strand breaks (SSBs) after treatment with human 8-oxo-guanine glycosylase-1 (hOGG1) when compared with 8-oxo-dGuo in the DNA as measured by the stable isotope dilution LC-MRM/MS method. Availability of the new LC-MRM/MS assay made it possible to show that the benzo[a]pyrene (B[a]P)-derived quinone, B[a]P-7,8-dione, could induce 8-oxo-dGuo formation in H358 cells. This most likely occurred through redox cycling between B[a]P-7,8-dione and B[a]P-7,8-catechol with concomitant generation of DNA damaging ROS. In keeping with this concept, inhibition of catechol-O-methyl transferase (COMT)-mediated detoxification of B[a]P-7,8-catechol with Ro 410961 caused increased 8-oxo-dGuo formation in the H358 cell DNA.

Biomarkers of induced active and passive smoking damage

In addition to the well-known link between smoking and lung cancer, large epidemiological studies have shown a relationship between smoking and cancers of the nose, oral cavity, oropharynx, larynx, esophagus, pancreas, bladder, kidney, stomach, liver, colon and cervix, as well as myeloid leukemia. Epidemiological evidence has reported a direct link between exposure of non-smokers to environmental tobacco smoke and disease, most notably, lung cancer. Much evidence demonstrates that carcinogenic-DNA adducts are useful markers of tobacco smoke exposure, providing an integrated measurement of carcinogen intake, metabolic activation, and delivery to the DNA in target tissues. Monitoring accessible surrogate tissues, such as white blood cells or bronchoalveolar lavage (BAL) cells, also provides a means of investigating passive and active tobacco exposure in healthy individuals and cancer patients. Levels of DNA adducts measured in many tissues of smokers are significantly higher than in non-smokers. While some studies have demonstrated an association between carcinogenic DNA adducts and cancer in current smokers, no association has been observed in ex or never smokers. The role of genetic susceptibility in the development of smoking related-cancer is essential. In order to establish whether smoking-related DNA adducts are biomarkers of tobacco smoke exposure and/or its carcinogenic activity we summarized all data that associated tobacco smoke exposure and smoking-related DNA adducts both in controls and/or in cancer cases and studies where the effect of genetic polymorphisms involved in the activation and deactivation of carcinogens were also evaluated. In the future we hope we will be able to screen for lung cancer susceptibility by using specific biomarkers and that subjects of compared groups can be stratified for multiple potential modulators of biomarkers, taking into account various confounding factors.

Deficient repair of 8-hydroxyguanine in the BxPC-3 pancreatic cancer cell line

Elevated levels of oxidatively induced DNA lesions have been reported in malignant pancreatic tissues relative to normal pancreatic tissues. However, the ability of the pancreatic cancer cells to remove these lesions has not previously been addressed. This study analyzed the effectiveness of the pancreatic cancer cell line, BxPC-3 to repair 8-hydroxyguanine (8-OH-Gua) relative to a nonmalignant cell line. We show that BxPC-3 cells repair 8-OH-Gua less effectively than the nonmalignant cells. This repair deficiency correlated with significant downregulation of the hOGG1 protein and the corresponding mRNA (30-fold lower than GAPDH) in BxPC-3 cell line. The repair defect was complemented in vivo by transient transfection of the hOGG1 gene and in vivo by recombinant hOGG1. These results are the first to show a deficiency of 8-OH-Gua repair in BxPC-3 cells, implicating this defect in the risk factor of pancreatic cancer.

Gene-environment interaction in tobacco-related cancers

This review summarizes the carcinogenic effects of tobacco smoke and the basis for interaction between tobacco smoke and genetic factors. Examples of published papers on gene-tobacco interaction and cancer risk are presented. The assessment of gene-environment interaction in tobacco-related cancers has been more complex than originally expected for several reasons, including the multiplicity of genes involved in tobacco metabolism, the numerous substrates metabolized by the relevant genes and the interaction of smoking with other metabolic pathways. Future studies on gene-environment interaction and cancer risk should include biomarkers of smoking dose, along with markers of quantitative historical exposure to tobacco. Epigenetic studies should be added to classic genetic analyses, in order to better understand gene-environmental interaction and individual susceptibility. Other metabolic pathways in competition with tobacco genetic metabolism/repair should be incorporated in epidemiological studies to generate a more complete picture of individual cancer risk associated with environmental exposure to carcinogens.

Ionic strength and magnesium affect the specificity of Escherichia coli and human 8-oxoguanine-DNA glycosylases

An abundant oxidative lesion, 8-oxo-7,8-dihydroguanine (8-oxoG), often directs the misincorporation of dAMP during replication. To prevent mutations, cells possess an enzymatic system for the removal of 8-oxoG. A key element of this system is 8-oxoguanine-DNA glycosylase (Fpg in bacteria, OGG1 in eukaryotes), which must excise 8-oxoG from 8-oxoG:C pairs but not from 8-oxoG:A. We investigated the influence of various factors, including ionic strength, the presence of Mg(2+) and organic anions, polyamides, crowding agents and two small heterocyclic compounds (biotin and caffeine) on the activity and opposite-base specificity of Escherichia coli Fpg and human OGG1. The activity of both enzymes towards 8-oxoG:A decreased sharply with increasing salt and Mg(2+) concentration, whereas the activity on 8-oxoG:C was much more stable, resulting in higher opposite-base specificity when salt and Mg(2+) were at near-physiological concentrations. This tendency was observed with both Cl(-) and glutamate as the major anions in the reaction mixture. Kinetic and binding parameters for the processing of 8-oxoG:C and 8-oxoG:A by Fpg and OGG1 were determined under several different conditions. Polyamines, crowding agents, biotin and caffeine affected the activity and specificity of Fpg or OGG1 only marginally. We conclude that, in the intracellular environment, the specificity of Fpg and OGG1 for 8-oxoG:C versus 8-oxoG:A is mostly due to high ionic strength and Mg(2+).

Polycyclic aromatic hydrocarbon--DNA adducts in prostate and biochemical recurrence after prostatectomy

PURPOSE

DNA adduct levels may be influenced by metabolic activity, DNA repair capabilities, and genomic integrity, all of which play a role in cancer progression.

EXPERIMENTAL DESIGN

To determine if elevated DNA adducts are a marker for prostate cancer progression, we measured polycyclic aromatic hydrocarbon-DNA adducts by immunohistochemistry in prostate cells of 368 surgical prostate cancer patients treated at the Henry Ford Hospital in Detroit, Michigan, between September 1999 and July 2004. Patients were followed up to 5 years after surgery with relative risk for biochemical recurrence (BCR) estimated with a Cox proportional hazards model that adjusted for standard clinical risk factors.

RESULTS

At 1 year of follow-up, patients with adduct levels above the median in tumor cells [hazard ratio (HR), 2.40; 95% confidence interval (95% CI), 1.10-5.27] and nontumor cells (HR, 3.22; 95% CI, 1.40-7.39) had significant increased risk of BCR, but these HRs decreased to 1.12 (95% CI, 0.68-1.83) and 1.46 (95% CI, 0.89-2.41) in tumor and nontumor cells at 5 years postsurgery. When we restricted our analysis to patients with advanced-stage (III+) disease, those with high adduct levels in either tumor (53.5% versus 30.2%; P = 0.07) or nontumor (55.2% versus 28.6%; P = 0.02) cells had BCR rates almost 2-fold higher. In race-stratified analyses, the greatest risk of BCR associated with high adduct levels (in nontumor cells) was for African American patients younger than 60 years old (HR, 3.79; 95% CI, 1.01-14.30).

CONCLUSIONS

High polycyclic aromatic hydrocarbon-DNA adduct levels in nontumor prostate cells are most strongly associated with BCR between 1 and 2 years after surgery and in patient subsets defined by younger age, advanced tumor stage, and African American race.

Haplotype of N-acetyltransferase 1 and 2 and risk of pancreatic cancer

We examined the association between N-acetyltransferase 1 and 2 (NAT1 and NAT2) haplotype and risk of pancreatic cancer by genotyping eight NAT1 and seven NAT2 single nucleotide polymorphisms in 532 patients and in 581 healthy controls (all non-Hispanic white) who were recruited at M. D. Anderson Cancer Center from January 2000 to December 2006. Haplotypes were reconstructed by using an expectation-maximization algorithm. Odds ratios and 95% confidence intervals were estimated by using unconditional logistic regression models. Covariates included age (continuous variable), sex, pack-year of smoking (categorical), and history of diabetes when appropriate. NAT1 and NAT2 genotype was mutually adjusted. The prevalence of haplotype NAT1*10-NAT2*6A was 4.3% versus 2.7% (P=0.06) and NAT1*11-NAT2*6A was 1.2% versus 0.4% (P=0.05) in patients and controls, respectively. The diplotype NAT1*10/*10 or NAT1*10/*11 and NAT2*6A/any slow allele was associated with a higher risk of pancreatic cancer compared with other diplotypes (multivariate odds ratio, 4.15; 95% confidence interval, 1.15-15.00; P=0.03). NAT2 slow genotype were associated with increased risk of pancreatic cancer among heavy smokers and among individuals with a history of diabetes. We for the first time found that rare NAT1*10 or NAT1*11-NAT2*6A diplotype may be an "at-risk" genetic variant for pancreatic cancer. The NAT2*6A/any slow acetylation genotype may be a predisposing factor for pancreatic cancer among diabetics with smoking exposure. Our observations must be confirmed in larger independent studies.

The association between N-acetyltransferase 2 gene polymorphisms and pancreatic cancer

Pancreatic cancer has been linked with exposure to environmental chemicals, which generally require metabolic activation to highly reactive toxic or carcinogenic intermediates. N-acetyltransferase 1 (NAT1) and N-acetyltransferase 2 (NAT2) are expressed primarily in extrahepatic and hepatic tissues, respectively. Both enzymes catalyze N- and O-acetylation of aromatic and heterocyclic amines. It is believed that these compounds are activated via O-acetylation and detoxified by N-acetylation. Several polymorphisms of these two genes have been associated with an increased risk of cancer. Twenty-seven cases of pancreatic cancer and 104 controls were included in this study. Blood was collected in EDTA-containing tubes, and genomic DNA was extracted from the white blood cells by using a high pure PCR template preparation kit. Genotyping of NAT2 polymorphisms was detected by a real time PCR instrument. There was a significant difference in the distribution of the NAT2*6A acetylators phenotype between cases and the controls. The odds ratio of pancreatic cancer for the NAT2*6A slow phenotype was 5.7 (95% CI = 1.27-25.55; p = 0.023) compared with the fast type. Our results suggest that slow acetylators have higher risk of developing pancreatic cancer than fast acetylators. NAT2 gene polymorphisms may be associated with genetic susceptibility to pancreatic cancer.

CYP1B1 polymorphisms and k-ras mutations in patients with pancreatic ductal adenocarcinoma

The frequency of CYP1B1 polymorphisms in pancreatic cancer has never been reported. There is also no evidence on the relationship between CYP1B1 variants and mutations in ras genes (K-, H- or N-ras) in any human neoplasm. We analyzed the following CYP1B1 polymorphisms in 129 incident cases of pancreatic ductal adenocarcinoma (PDA): the m1 allele (Val to Leu at codon 432) and the m2 allele (Asn to Ser at codon 453). The calculated frequencies for the m1 Val and m2 Asn alleles were 0.45 and 0.68, respectively. CYP1B1 genotypes were out of Hardy-Weinberg equilibrium; this was largely due to K-ras mutated PDA cases. The Val/Val genotype was over five times more frequent in PDA cases with a K-ras mutation than in wild-type cases (OR = 5.25; P = 0.121). In PDA, polymorphisms in CYP1B1 might be related with K-ras activation pathways.

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.

The role of polycyclic aromatic hydrocarbon-DNA adducts in inducing mutations in mouse skin

Polycyclic aromatic hydrocarbons (PAH) form stable and depurinating DNA adducts in mouse skin to induce preneoplastic mutations. Some mutations transform cells, which then clonally expand to establish tumors. Strong clues about the mutagenic mechanism can be obtained if the PAH-DNA adducts can be correlated with both preneoplastic and tumor mutations. To this end, we studied mutagenesis in PAH-treated early preneoplastic skin (1 day after exposure) and in the induced papillomas in SENCAR mice. Papillomas were studied by PCR amplification of the H-ras gene and sequencing. For benzo[a]pyrene (BP), BP-7,8-dihydrodiol (BPDHD), 7,12-dimethylbenz[a]anthracene (DMBA) and dibenzo[a,l]pyrene (DB[a,l]P), the codon 13 (GGC to GTC) and codon 61 (CAA to CTA) mutations in papillomas corresponded to the relative levels of Gua and Ade-depurinating adducts, despite BP and BPDHD forming significant amounts of stable DNA adducts. Such a relationship was expected for DMBA and DB[a,l]P, as they formed primarily depurinating adducts. These results suggest that depurinating adducts play a major role in forming the tumorigenic mutations. To validate this correlation, preneoplastic skin mutations were studied by cloning H-ras PCR products and sequencing individual clones. DMBA- and DB[a,l]P-treated skin showed primarily A.T to G.C mutations, which correlated with the high ratio of the Ade/Gua-depurinating adducts. Incubation of skin DNA with T.G-DNA glycosylase eliminated most of these A.T to G.C mutations, indicating that they existed as G.T heteroduplexes, as would be expected if they were formed by errors in the repair of abasic sites generated by the depurinating adducts. BP and its metabolites induced mainly G.C to T.A mutations in preneoplastic skin. However, PCR over unrepaired anti-BPDE-N(2)dG adducts can generate similar mutations as artifacts of the study protocol, making it difficult to establish an adduct-mutation correlation for determining which BP-DNA adducts induce the early preneoplastic mutations. In conclusion, this study suggests that depurinating adducts play a major role in PAH mutagenesis.

Catechol-estrogen modified DNA: a better antigen for cancer autoantibody

Estrogens are known mutagenic and carcinogenic risk factors. Non-enzymatic oxidation of catechol-estrogens in the presence of copper is reported to generate reactive oxygen species (ROS) that can cause DNA damage. We show that DNA modification in the presence of 4-hydroxyestradiol (4-OHE(2)) and copper (Cu-II) results in single and double strand breaks, base modification, hyperchromicity and change in ellipticity. Modified DNA (4-OHE(2)-Cu(II)-DNA) was highly immunogenic in experimental animals. Induced anti-4-OHE(2)-Cu(II)-DNA antibodies were effectively used as a probe for detecting oxidative lesions in human genomic DNA and for the estimation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels in the urine of cancer patients. Circulating antibodies from cancer patients showed high binding to 4-OHE(2)-Cu(II)-DNA as compared to native DNA. Our results imply that interaction of catechol-estrogen and copper leads to the production of potent ROS, capable of causing DNA damage, thus playing an important role in carcinogenesis. The modified DNA presents unique epitopes which may be one of the factors for autoantibody induction in cancer.

The genetics of nicotine dependence: Relationship to pancreatic cancer

Smoking of tobacco products continues to be a major cause of worldwide health problems. Epidemiological studies have shown that tobacco smoking is the greatest risk factor for the development of pancreatic cancer. Smokers who are able to quit smoking can reduce their risk of pancreatic cancer by nearly 50% within two years, however, their risk of developing pancreatic cancer remains higher than that of non-smokers for 10 years. Nicotine is the major psychoactive substance in tobacco, and is responsible for tobacco dependence and addiction. Recent evidence suggests that individuals have genetically based differences in their ability to metabolize nicotine, as well as genetic differences in the psychological reward pathways that may influence individual response to smoking initiation, dependence, addiction and cessation. Numerous associations have been reported between smoking behavior and genetic polymorphisms in genes that are responsible for nicotine metabolism. In addition, polymorphisms in genes that encode neurotransmitters and transporters that function in psychological reward pathways have been implicated in differences in smoking behavior. However, there is a large degree of between-study variability that demonstrates the need for larger, well-controlled case-control studies to identify target genes and deduce mechanisms that account for the genetic basis of inter-individual differences in smoking behavior. Understanding the genetic factors that increase susceptibility to tobacco addiction may result in more effective tobacco cessation programs which will, in turn, reduce the incidence of tobacco related disease, including pancreatic cancer.

Omega-3 fatty acids for the treatment of cancer cachexia: issues in designing clinical trials of dietary supplements

Complementary and alternative medicine (CAM) is increasingly popular, despite the limited evidence of the efficacy and safety of some forms of CAM. Cancer patients often turn to CAM therapies for the relief of treatment- induced side-effects and comorbidities. Cancer-associated weight loss commonly results in decreased functional status, life expectancy, and quality of life. Despite the high morbidity and mortality associated with cancer cachexia, mainstream treatments do not sustain weight. Although nutritional supplements are commonly used, many of these have not been tested in clinical trials. The issues faced in dietary supplement research differ from those in pharmaceutical drug trials. These include problems with standardization, contamination, and compliance documentation. A double-blind, randomized, placebo-controlled trial is proposed to evaluate the efficacy and safety of fish oil supplementation for the treatment of cachexia in pancreatic cancer patients. The primary outcome measure will be lean body mass; secondary outcomes include functional status and quality of life. The methodology of the clinical trial is reviewed here and the unique problems faced by investigators in designing studies of dietary supplements are discussed.

Increased etheno-DNA adducts in affected tissues of patients suffering from Crohn's disease, ulcerative colitis, and chronic pancreatitis

Chronic inflammatory processes induce oxidative stress and lipid peroxidation (LPO), hereby generating DNA-reactive aldehydes such as trans-4-hydroxy-2-nonenal (HNE). Etheno-modified DNA bases are inter alia generated by reaction of DNA with HNE. Using an immunoaffinity-(32)P-postlabeling method, the authors have investigated etheno-DNA adduct levels 1,N (6)-ethenodeoxyadenosine (epsilondA) and of 3,N (4)-ethenodeoxycytidine (epsilondC) in the pancreas of chronic pancreatitis patients and in the colon of patients with inflammatory bowel disease. Both epsilondA and epsilondC levels were found to be significantly, 3 and 28 times, respectively, elevated in the inflamed pancreatic tissue. In contrast, only epsilondC was found to be increased in affected colonic mucosa of Crohn's disease (19 times) and of ulcerative colitis patients (4 times) when compared to asymptomatic tissues. In all three cancer-prone diseases, the mean epsilondC-levels in tissues were five- to ninefold higher than those of epsilondA. Differential or impaired DNA repair pathways of these adducts, known to occur by two different glycosylases are implicated. K-ras in pancreatic tumors and K-ras and p53 in colon mucosa in long-standing inflammatory bowel disease are known to be highly mutated. The conclusion is that promutagenic etheno-DNA adducts are generated as a consequence of chronic inflammation, acting as a driving force to malignancy in cancer-prone inflammatory diseases.

Improved measurement of dibenzo[a,l]pyrene-induced abasic sites by the aldehyde-reactive probe assay

Dibenzo[a,l]pyrene (DB[a,l]P) induces abundant amounts of depurinating adducts that spontaneously dissociate to form abasic sites in DNA. However, several previous studies that used the aldehyde-reactive probe (ARP) assay, could not verify abasic site formation by DB[a,l]P. Therefore, we examined whether a modification of the ARP assay would allow greater quantification of abasic sites. A previous study indicated that the abasic site quantification is improved by letting ARP trap the nascent abasic sites in cells, before extracting DNA for the assay. To test whether the addition of ARP to the DB[a,l]P-DNA adduct-forming reaction would improve abasic site quantification, we treated calf thymus DNA (0.625 mg/mL) with DB[a,l]P (80 microM) and 3-methylcholanthrene-treated rat liver microsomes with or without ARP (3 mM). The inclusion of ARP in the adduct-forming reaction resulted in significantly greater detection of abasic sites (62 lesions/10(6) bp versus 3.7 lesions/10(6) bp). DB[a,l]P also induces DNA strand breaks. The strand breaks may occur at abasic sites and by other mechanisms, such as oxidative damage. ARP/O-methoxyamine-abasic site conjugates are refractory to strand breakage, however, ARP or O-methoxyamine (3-10 mM) could only partially protect DB[a,l]P-induced DNA degradation, presumably by protecting the abasic sites, but not the other strand breaks. These results suggest that if DNA strand breakages occur at the abasic sites or at bases flanking them, and the fragments are lost during DNA extraction, abasic site estimation could be compromised. To obtain an independent line of evidence for abasic site formation in DB[a,l]P-treated cells, mouse Mbeta16 fibroblasts were treated with DB[a,l]P and O-methoxyamine. O-Methoxyamine is known to potentiate cytotoxicity of abasic site-inducing chemicals by forming abasic site conjugates, which partially inhibits their repair. O-Methoxyamine was found to increase DB[a,l]P cytotoxicity in these cells, supporting the idea that DB[a,l]P formed abasic sites. In summary, the inclusion of ARP in the DB[a,l]P-DNA adduct-forming reaction traps and protects the nascent abasic sites, allowing an improved quantification of abasic sites.

Expression of human 8-oxoguanine DNA glycosylase (hOGG1) in follicular lymphoma

The human homologue of the yeast DNA repair enzyme 8-oxoguanine DNA glycosylase (hOGG1) repairs oxidatively damaged guanosine nucleotides in DNA. This enzyme is highly expressed in reactive germinal centers, where lymphoid cells are under oxidative stress, and has been thought to protect lymphocytes from mutation. As a first step to investigate the role of hOGG1 in lymphomagenesis, we evaluated hOGG1 expression in follicular lymphoma. Immunohistochemistry was performed on formalin-fixed paraffin-embedded tissue of 28 follicular lymphoma cases (16 grade 1, seven grade 2, and five grade 3) to evaluate the expression of hOGG1 in neoplastic follicles. Reactive germinal centers of non-neoplastic tonsil and lymph node tissue were also examined. Fluorescent-in-situ hybridization (FISH) was performed using a DNA probe from BAC clone RP11-266J6 corresponding to 3p25, where the hOGG1 gene resides, to evaluate for the presence or absence of a deletion. In reactive germinal centers, the majority of centroblasts and centrocytes were positive for hOGG1. In contrast, the majority (21 of 28 or 75%) of follicular lymphoma cases showed absent/minimal expression of hOGG1. Only four of 28 (14%) follicular lymphoma cases revealed the same levels of hOGG1 expression as reactive germinal centers. There was no correlation between hOGG1 expression and histologic grade. None of the 16 cases evaluated by FISH showed a deletion of hOGG1. Furthermore, absent/minimal hOGG1 expression was observed in four of six Bcl-2-negative follicular lymphoma cases. Our findings suggest that absent/minimal hOGG1 expression occurs in the majority of follicular lymphomas. The downregulation of hOGG1 does not appear to be due to a deletion of the hOGG1 locus. Additionally, finding absent/minimal hOGG1 expression in a subset of Bcl-2-negative follicular lymphomas suggests that hOGG1 may have utility in diagnosing Bcl-2-negative follicular lymphomas.

Harvey-ras gene expression and epidermal cell proliferation in dibenzo[a,l]pyrene-treated early preneoplastic SENCAR mouse skin

Topical application of dibenzo[a,l]pyrene (DB[a,l]P) to the dorsal skin of SENCAR mice induces codon 61 (CAA Gln to CTA Leu) mutations in the Harvey (H)-ras gene within 12 h after treatment. Between days 1 and 3, the frequency of these mutations increases rapidly, suggesting that skin cells carrying the codon 61 mutations proliferate in this period. We have investigated DB[a,l]P-treated mouse skin (12 h-7 d) for further evidence of H-ras expression and epidermal cell proliferation. Two waves of cell proliferation were observed: the first wave (1-2 d) correlated with the clonal proliferation of codon 61-mutated cells, and the second wave (3-7 d) correlated with DB[a,l]P-induced hyperplasia. DB[a,l]P-induced early preneoplastic cell proliferation correlated with H-ras and specific G1 cyclin expression. Total H-ras protein and cyclin D1 were found to increase during DB[a,l]P-induced hyperplasia, but the levels of guanosine triphosphate-bound (active) H-ras protein and cyclin E were increased during the putative clonal proliferation of codon 61-mutated cells. These results suggest that DB[a,l]P-induced oncogenically mutated cells proliferate in early preneoplastic skin. As this proliferation occurs in the absence of any promoting treatment, we propose that this phenomenon is a tumor initiation event.

Role of inflammation in pancreatic carcinogenesis and the implications for future therapy

BACKGROUND

The link between inflammation and pancreatic cancer has been observed for a number of gastrointestinal neoplasms. This review examines the role of inflammation in pancreatic carcinogenesis and how it can be utilised to develop new therapies against pancreatic cancer.

METHODS

A literature review of Pubmed, Medline and Web of Science databases was undertaken using the key words, pancreatic cancer, inflammation, inducible nitric oxide, interleukins, pro-inflammatory cytokines, cyclooxygenase-2, NF-kappa B, reactive oxygen species, DNA adducts, lipoxygenases, chemoprevention.

RESULTS

Epidemiological evidence and molecular studies both in vitro and in vivo all support the hypothesis that inflammation plays an important in the initiation and progression of pancreatic tumours.

CONCLUSION

Sustained damage caused by chronic inflammation may precede the onset of frank malignancy by a significant interval. As such, suppression of inflammatory changes and oxidative damage, may help delay or even prevent the inception of pancreatic neoplasia.

Genetic polymorphisms of GSTT1, GSTM1, GSTP1, MnSOD, and catalase in nonhereditary chronic pancreatitis: evidence of xenobiotic stress and impaired antioxidant capacity

Epidemiological studies have demonstrated a variety of potential environmental factors that may alter susceptibility to chronic pancreatitis (CP) through oxidative/xenobiotic stress; however, a direct causal and mechanistic role has not been established. We aimed (1) to determine the prevalence of functional genetic polymorphisms in the antioxidant enzymes, glutathione S-transferase GSTM-1, GSTP-1, and GSTT-1, manganese superoxide dismutase, and catalase in CP and (2) to reveal evidence of oxidative stress in patients with CP by measuring whole-blood glutathione redox status. In total, 122 patients with CP (75 alcohol-induced [A1CP], 33 idiopathic [ICP], and 13 hereditary) and 245 age- and sex-matched controls were recruited. The prevalence of the functional GSTT-1 genotype (GSTT-1*A) was significantly higher in CP (88.5%) compared to healthy controls (76%; chi2 = 7.26, P = 0.007). Stratification to disease etiology demonstrated that the GSTT-1*A genotype was also significantly more prevalent among patients with ICP (94%; P = 0.02; 95% CI, 0.04-9.16) but not in those with A1CP. In 22 patients with stable CP, the whole-blood glutathione concentration (median [IQR]: 72 micromol/L [21-181 micromol/L]) and the glutathione redox ratio (GSH/GSSG) (median [IQR]: 9 (3-77]) were significantly reduced compared to those in 20 healthy volunteers (median [IQR]: 815 micromol/L [679-1148 micromol/L], P < 0.001, and 96 [52-347], P = 0.005, respectively). We conclude that the GSTT-1 functional genotype is associated with ICP. Evidence of altered glutathione redox status suggests that this disease modification may be a consequence of oxidative stress or the bioactivation of xenobiotics.

Smoking-gene interaction and disease development: relevance to pancreatic cancer and atherosclerosis

There is little doubt that cigarette smoking remains a major environmental health risk that humans are facing in the twenty-first century. Cigarette smokers are more likely to develop many forms of diseases than nonsmokers, including cancers and vascular diseases. With the availability of the human genome sequence, we become more aware of the genetic contributions to these common diseases, especially the interactive relations between environmental factors (e.g., smoking) and genes on disease susceptibility, development, and prognosis. Although smoking is responsible for up to 30% of pancreatic cancers and about 10% of cases are ascribed to genetic reasons, some genetic variants do not predispose carriers to disease development unless they are exposed to a specific adverse environment such as smoking. This smoke-gene interaction could potentially be responsible for most of the cases. Certain polymorphisms in genes such as CYP1A1 have been shown particularly sensitive to smoking-induced pathogenesis, including pancreatic cancer and atherosclerosis. We found that individuals with CYP1A1 CC genotype had a more than three fold increase in risk for severe coronary atherosclerosis when they smoked. Patients with endothelial nitric oxide synthase (eNOS) intron 4 27 repeat homozygotes were more likely to develop severe coronary stenosis when they smoked. On the other hand, DNA variants at the eNOS gene also dictate how smoking affects the expression of eNOS. We showed that GSTM1 deficiency was not involved in smoking-induced vascular diseases, but p53 polymorphisms tended to modify the disease severity in smokers. We are still at an early stage of defining the pairs and mechanisms of smoke-gene interaction, and this etiologic mechanism may hold great potential for risk assessment, treatment strategy, and prognostic predictions.

Cytochrome P-450 1A1 gene polymorphisms and risk of breast cancer: a HuGE review

Cytochrome P-450 (CYP) 1A1 plays a key role in phase I metabolism of polycyclic aromatic hydrocarbons and in estrogen metabolism. It is expressed predominantly in extrahepatic tissues, including the breast. Four CYP1A1 gene polymorphisms (3801T --> C, Ile462Val, 3205T --> C, and Thr461Asp) have been studied in relation to breast cancer. The 3801C variant is more common than the Val variant. Both variants occur more frequently in Asians than in White populations. The 3205T --> C polymorphism has been observed in African Americans only. Little data are available on the geographic/ethnic distribution of the Thr461Asp polymorphism. The functional significance of the polymorphisms is unclear. In 17 studies, no consistent association between breast cancer and CYP1A1 genotype was found. Meta-analysis found no significant risk for the genotypes 1) 3801C/C (relative risk (RR) = 0.97, 95% confidence interval (CI): 0.52, 1.80) or 3801T/C (RR = 0.91, 95% CI: 0.70, 1.19) versus 3801T/T, 2) Val/Val (RR = 1.04, 95% CI: 0.63, 1.74) or Ile/Val (RR = 0.92, 95% CI: 0.76, 1.10) versus Ile/Ile, or 3) Asp/Asp (RR = 0.95, 95% CI: 0.20, 4.49) or Thr/Asp (RR = 1.12, 95% CI: 0.87, 1.43) versus Thr/Thr. Future studies should explore possible interactions between CYP1A1 and sources of polycyclic aromatic hydrocarbons, markers of estrogen exposure, other lifestyle factors influencing hormonal levels, and other genes involved in polycyclic aromatic hydrocarbon metabolism or hormonal biosynthesis.