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Fedak KM, Bernal A, Capshaw ZA, Gross S. Applying the Bradford Hill criteria in the 21st century: how data integration has changed causal inference in molecular epidemiology. Emerg Themes Epidemiol 2015; 12:14. [PMID: 26425136 PMCID: PMC4589117 DOI: 10.1186/s12982-015-0037-4] [Citation(s) in RCA: 357] [Impact Index Per Article: 39.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 09/23/2015] [Indexed: 01/15/2023] Open
Abstract
In 1965, Sir Austin Bradford Hill published nine “viewpoints” to help determine if observed epidemiologic associations are causal. Since then, the “Bradford Hill Criteria” have become the most frequently cited framework for causal inference in epidemiologic studies. However, when Hill published his causal guidelines—just 12 years after the double-helix model for DNA was first suggested and 25 years before the Human Genome Project began—disease causation was understood on a more elementary level than it is today. Advancements in genetics, molecular biology, toxicology, exposure science, and statistics have increased our analytical capabilities for exploring potential cause-and-effect relationships, and have resulted in a greater understanding of the complexity behind human disease onset and progression. These additional tools for causal inference necessitate a re-evaluation of how each Bradford Hill criterion should be interpreted when considering a variety of data types beyond classic epidemiology studies. Herein, we explore the implications of data integration on the interpretation and application of the criteria. Using examples of recently discovered exposure–response associations in human disease, we discuss novel ways by which researchers can apply and interpret the Bradford Hill criteria when considering data gathered using modern molecular techniques, such as epigenetics, biomarkers, mechanistic toxicology, and genotoxicology.
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Affiliation(s)
- Kristen M Fedak
- Department of Environmental and Radiological Health Sciences, Colorado State University, 350 West Lake Street, Fort Collins, CO 80521 USA ; Cardno ChemRisk, 4840 Pearl East Circle, Suite 300 West, Boulder, CO 80301 USA
| | - Autumn Bernal
- Cardno ChemRisk, 130 Vantis Suite 170, Aliso Viejo, CA 92656 USA
| | - Zachary A Capshaw
- Cardno ChemRisk, 4840 Pearl East Circle, Suite 300 West, Boulder, CO 80301 USA
| | - Sherilyn Gross
- Cardno ChemRisk, 4840 Pearl East Circle, Suite 300 West, Boulder, CO 80301 USA
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Geneletti S, Gallo V, Porta M, Khoury MJ, Vineis P. Assessing causal relationships in genomics: From Bradford-Hill criteria to complex gene-environment interactions and directed acyclic graphs. Emerg Themes Epidemiol 2011; 8:5. [PMID: 21658235 PMCID: PMC3141807 DOI: 10.1186/1742-7622-8-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 06/09/2011] [Indexed: 12/16/2022] Open
Abstract
Observational studies of human health and disease (basic, clinical and epidemiological) are vulnerable to methodological problems -such as selection bias and confounding- that make causal inferences problematic. Gene-disease associations are no exception, as they are commonly investigated using observational designs. A rich body of knowledge exists in medicine and epidemiology on the assessment of causal relationships involving personal and environmental causes of disease; it includes seminal causal criteria developed by Austin Bradford Hill and more recently applied directed acyclic graphs (DAGs). However, such knowledge has seldom been applied to assess causal relationships in clinical genetics and genomics, even in studies aimed at making inferences relevant for human health. Conversely, incorporating genetic causal knowledge into clinical and epidemiological causal reasoning is still a largely unexplored area. As the contribution of genetics to the understanding of disease aetiology becomes more important, causal assessment of genetic and genomic evidence becomes fundamental. The method we develop in this paper provides a simple and rigorous first step towards this goal. The present paper is an example of integrative research, i.e., research that integrates knowledge, data, methods, techniques, and reasoning from multiple disciplines, approaches and levels of analysis to generate knowledge that no discipline alone may achieve.
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Affiliation(s)
- Sara Geneletti
- Department of Statistics, London School of Economics, Houghton Street, London, UK.
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Parker LA, Porta M, Lumbreras B, López T, Guarner L, Hernández-Aguado I, Carrato A, Corominas JM, Rifà J, Fernandez E, Alguacil J, Malats N, Real FX. Clinical validity of detecting K-ras mutations for the diagnosis of exocrine pancreatic cancer: a prospective study in a clinically-relevant spectrum of patients. Eur J Epidemiol 2011; 26:229-36. [PMID: 21298467 DOI: 10.1007/s10654-011-9547-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Accepted: 01/20/2011] [Indexed: 12/22/2022]
Abstract
The diagnostic utility of detecting K-ras mutations for the diagnosis of exocrine pancreatic cancer (EPC) has not been properly studied, and few reports have analysed a clinically relevant spectrum of patients. The objective was to evaluate the clinical validity of detecting K-ras mutations in the diagnosis of EPC in a large sample of clinically relevant patients. We prospectively identified 374 patients in whom one of the following diagnoses was suspected at hospital admission: EPC, chronic pancreatitis, pancreatic cysts, and cancer of the extrahepatic biliary system. Mutations in the K-ras oncogene were analysed by PCR and artificial RFLP in 212 patients. The sensitivity and specificity of the K-ras mutational status for the diagnosis of EPC were 77.7% (95% CI: 69.2-84.8) and 78.0% (68.1-86.0), respectively. The diagnostic accuracy was hardly modified by sex and age. In patients with either mutated K-ras or CEA > 5 ng/ml, the sensitivity and specificity were 81.0% (72.9-87.6) and 62.6% (72.9-87.6), respectively. In patients with mutated K-ras and CEA > 5 ng/ml the sensitivity was markedly reduced. In comparisons with a variety of non-EPC patient groups sensitivity and specificity were both always greater than 75%. In this clinically relevant sample of patients the sensitivity and specificity of K-ras mutations were not sufficiently high for independent diagnostic use. However, it seems premature to rule out the utility of K-ras analysis in conjunction with other genetic and 'omics' technologies.
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Affiliation(s)
- Lucy A Parker
- Department of Public Health, Miguel Hernández University, Alicante, Spain
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Gasull M, Porta M, Pumarega J, Vioque J, Bosch de Basea M, Puigdomènech E, Morales E, Grimalt JO, Malats N. The relative influence of diet and serum concentrations of organochlorine compounds on K-ras mutations in exocrine pancreatic cancer. CHEMOSPHERE 2010; 79:686-697. [PMID: 20350743 DOI: 10.1016/j.chemosphere.2010.03.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 02/24/2010] [Accepted: 03/06/2010] [Indexed: 05/29/2023]
Abstract
BACKGROUND In exocrine pancreatic cancer (EPC) mechanistic relationships may exist among some organochlorine compounds (OCs) and mutations in the K-ras oncogene, as well as among the latter and dietary factors. OBJECTIVE To analyze (1) the relationship between food intake and serum concentrations of OCs in EPC patients and (2) the relative influence of food and OCs on the frequency of K-ras mutations in EPC. PATIENTS AND METHODS Incident cases of EPC were prospectively identified, and interviewed face-to-face during hospital admission (N=135 patients with data on OCs and diet, and N=97 with additional information on K-ras status). OCs were measured by high-resolution gas chromatography with electron-capture detection. RESULTS Consumption of milk and other dairy products was positively associated with concentrations of p,p'-DDT, PCB 138 and PCB 153 (log-transformed betas=0.652, 0.588 and 0.317, respectively; all p<0.05). When adjusted by OCs, dairy products were no longer associated with K-ras. By contrast, after adjusting by consumption of dairy products, patients with the highest concentrations of p,p'-DDT and some PCBs remained more likely to have a K-ras-mutated EPC than patients with lower concentrations (OR for upper tertile of PCB 138=5.5, 95% CI: 1.3-23.4). CONCLUSIONS Dairy products were a source of OCs. The association between dairy products and K-ras mutations was not independent of OCs. By contrast, the association between OCs and K-ras was not confounded by dairy products. OCs may be more likely to contribute to the occurrence of K-ras mutations than nutrients contained in dairy products.
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Affiliation(s)
- Magda Gasull
- Institut Municipal d'Investigació Mèdica, Barcelona, Catalonia, Spain
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Porta M, López T, Pumarega J, Jariod M, Crous-Bou M, Marco E, Rifà J, Grimalt JO, Malats N, Real FX. In pancreatic ductal adenocarcinoma blood concentrations of some organochlorine compounds and coffee intake are independently associated with KRAS mutations. Mutagenesis 2009; 24:513-21. [PMID: 19797353 DOI: 10.1093/mutage/gep037] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
While KRAS activation is a fundamental initiating event in the aetiopathogenesis of pancreatic ductal adenocarcinoma (PDA), environmental factors influencing the occurrence and persistence of KRAS mutations remain largely unknown. The objective was to test the hypothesis that in PDA there are aetiopathogenic relationships among concentrations of some organochlorine compounds (OCs) and the mutational status of the KRAS oncogene, as well as among the latter and coffee intake. Incident cases of PDA were interviewed and had blood drawn at hospital admission (N = 103). OCs were measured by high-resolution gas chromatography with electron capture detection. Cases whose tumours harboured a KRAS mutation had higher concentrations of p,p'-dichlorodiphenyltrichloroethane (DDT), p,p'-dichlorodiphenyldichloroethene (DDE) and polychlorinated biphenyls (PCBs) 138, 153 and 180 than cases with wild-type KRAS, but differences were statistically significant only for p,p'-DDT and PCBs 138 and 153. The association between coffee intake and KRAS mutations remained significant (P-trend < 0.015) when most OCs where accounted for. When p,p'-DDT, PCB 153, coffee and alcohol intake were included in the same model, all were associated with KRAS (P = 0.042, 0.007, 0.016 and 0.025, respectively). p,p'-DDT, p,p'-DDE and PCB 138 were significantly associated with the two most prevalent KRAS mutations (Val and Asp). OCs and coffee may have independent roles in the aetiopathogenesis of PDA through modulation of KRAS activation, acquisition or persistence, plausibly through non-genotoxic or epigenetic mechanisms. Given that KRAS mutations are the most frequent abnormality of oncogenes in human cancers, and the lifelong accumulation of OCs in humans, refutation or replication of the findings is required before any implications are assessed.
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Affiliation(s)
- Miquel Porta
- Institut Municipal d'Investigació Mèdica-Hospital del Mar, E-08003 Barcelona, Catalonia, Spain.
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Crous-Bou M, Porta M, López T, Jariod M, Malats N, Morales E, Guarner L, Rifà J, Carrato A, Real FX. Lifetime history of alcohol consumption and K-ras mutations in pancreatic ductal adenocarcinoma. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2009; 50:421-430. [PMID: 19326463 DOI: 10.1002/em.20483] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
BACKGROUND In pancreatic ductal adenocarcinoma (PDA), evidence on the etiopathogenic role of alcohol consumption in the occurrence of K-ras mutations is scant, and the role of alcohol in pancreatic carcinogenesis is not well established. We analyzed the relation between lifetime consumption of alcohol and mutations in codon 12 of the K-ras oncogene in patients with PDA. METHODS Incident cases of PDA were prospectively identified and interviewed face-to-face during hospital admission about lifetime alcohol consumption and other lifestyle factors. Logistic regression was used to compare PDA cases (N = 107) with mutated and wild-type K-ras tumors (case-case study). RESULTS Mutated cases were moderate or heavy drinkers more frequently than wild-type cases: the odds ratio adjusted by age, sex, smoking, and history of pancreatitis (ORa) was 3.18 (95% confidence interval: 1.02-9.93; P = 0.046). Total grams of alcohol and years of consumption were higher in mutated than in wild-type cases: the ORa for lifetime alcohol consumption over 507,499 g was 3.35 (95% CI: 0.81-13.88); and for more than 40 years of alcohol consumption it was 4.47 (95% CI: 1.05-19.02). Age at onset of alcohol consumption and years of abstinence were also associated with the presence of K-ras mutations. There were no significant differences in alcohol dependency. CONCLUSIONS Alcohol consumption is weakly associated with an increased risk of having a K-ras mutated PDA. To confirm or to refute the hypothesis that ethanol, acetaldehyde or other alcohol-related substances might influence the acquisition or persistence of K-ras mutations in the pancreatic epithelium, large and unselected studies are warranted.
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Wendt LR, Osvaldt AB, Bersch VP, Schumacher RDC, Edelweiss MIA, Rohde L. Pancreatic intraepithelial neoplasia and ductal adenocarcinoma induced by DMBA in mice: effects of alcohol and caffeine. Acta Cir Bras 2008; 22:202-9. [PMID: 17546293 DOI: 10.1590/s0102-86502007000300008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2007] [Accepted: 03/20/2007] [Indexed: 12/31/2022] Open
Abstract
PURPOSE To evaluate the effects of alcohol and caffeine in a pancreatic carcinogenesis mouse model induced by 7,12-dimethylbenzantracene (DMBA), according to the PanIN classification system. METHODS 120 male, Mus musculus, CF-1 mice were divided into four groups. Animals received either water or caffeine or alcohol or alcohol + caffeine in their drinking water. In all animals, 1 mg of DMBA was implanted into the head of the pancreas. After 30 days, euthanasia was performed; excised pancreata were then fixed in formalin, stained with hematoxylin-eosin and categorized as follows: normal ducts, reactive hyperplasia, PanIN-1A, PanIN-1B, PanIN-2, PanIN-3 or adenocarcinoma. RESULTS PanIN lesions were verified in all groups. Adenocarcinoma was detected in 15% of animals in the caffeine group, 16.6% in the water group, 23.8% in the alcohol + caffeine group and 52.9% in the alcohol group (P<0.05). CONCLUSIONS The experimental pancreatic carcinogenesis mouse model using DMBA effectively induces PanIN lesions and pancreatic adenocarcinoma. This study verified the association between alcohol use and pancreatic adenocarcinoma; caffeine did not present the same effect.
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Green tea and coffee intake and risk of pancreatic cancer in a large-scale, population-based cohort study in Japan (JPHC study). Eur J Cancer Prev 2007; 16:542-8. [DOI: 10.1097/cej.0b013e32809b4d30] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Porta M, Pumarega J, Ferrer-Armengou O, López T, Alguacil J, Malats N, Fernàndez E. Timing of blood extraction in epidemiologic and proteomic studies: results and proposals from the PANKRAS II Study. Eur J Epidemiol 2007; 22:577-88. [PMID: 17636417 DOI: 10.1007/s10654-007-9149-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2007] [Accepted: 05/29/2007] [Indexed: 12/22/2022]
Abstract
There are no consensus guidelines or standards for epidemiologic and '-omics' studies using blood biomarkers on how to report the timing of extraction of blood samples. However, disease-induced changes in blood concentrations of exogenous and endogenous compounds may bias studies. The aim of the present report is to describe the timing of blood collection with respect to a variety of relevant clinical events in the PANKRAS II Study, and to suggest ways to display graphically the quantitative information. Subjects were 167 incident cases of exocrine pancreatic cancer prospectively recruited in five teaching hospitals in eastern Spain. Over 80% of patients had blood extracted during the first 6 months since onset of cancer symptoms, and 82% within the first month of admission to a study hospital. Over 80% of cases had blood drawn after an ultrasound, a CT scan or an ERCP, 25% after a laparotomy, and 37% after treatment onset. All three intervals from blood extraction to diagnosis, to treatment onset and to interview had a median of 0 days, and 88% of cases had blood drawn within 2 weeks of diagnosis. Over 72% of cases had concentrations of total lipids in the medium, normal range. Results suggest ways to report intervals involving blood biomarkers and may contribute to develop consensus guidelines and standards on the collection of blood samples in epidemiologic and '-omics' research.
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Affiliation(s)
- Miquel Porta
- Clinical & Molecular Epidemiology of Cancer Unit, Institut Municipal d'Investigació Mèdica, Universitat Autònoma de Barcelona, Carrer del Dr. Aiguader 88, 08003 Barcelona, Catalonia, Spain.
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Morales E, Porta M, Vioque J, López T, Mendez MA, Pumarega J, Malats N, Crous-Bou M, Ngo J, Rifà J, Carrato A, Guarner L, Corominas JM, Real FX. Food and nutrient intakes and K-ras mutations in exocrine pancreatic cancer. J Epidemiol Community Health 2007; 61:641-9. [PMID: 17568059 PMCID: PMC2465759 DOI: 10.1136/jech.2007.060632] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/31/2007] [Indexed: 12/30/2022]
Abstract
BACKGROUND No studies have investigated the relation between K-ras mutations and dietary factors in exocrine pancreatic cancer (EPC), and fewer than 10 studies have done so in other neoplasms. PATIENTS AND METHODS Incident cases of EPC were prospectively identified, and interviewed face-to-face during hospital admission. Food and nutrient intakes were measured with a food frequency questionnaire. Logistic regression was used to compare EPC cases (n = 107) with and without K-ras mutations (case-case study). RESULTS K-ras mutations were more common among daily consumers of milk and other dairy products than among non-daily consumers: the odds ratio adjusted by total energy, age, sex, smoking, alcohol and coffee consumption (ORa) was 5.1 (95% CI 1.1 to 24.5, p = 0.040). For all dairy products, including butter, the ORa for the medium and upper tertiles of intake were 5.4 and 11.6, respectively (p for trend = 0.023). The ORa for regular coffee drinkers further adjusted by dairy consumption was 4.7 (95% CI 1.1 to 20.7, p = 0.043). K-ras mutated cases reported a lower intake of vitamin E (ORa = 0.2, p for trend = 0.036), polyunsaturated fats and omega 3 fatty acids (ORa = 0.2; p for trend <0.03). CONCLUSIONS Results support the hypothesis that in EPC exposure to specific dietary components or contaminants may influence the occurrence or persistence of K-ras mutations.
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Affiliation(s)
- Eva Morales
- Clinical & Molecular Epidemiology of Cancer Unit, Institut Municipal d'Investigació Mèdica (IMIM), Universitat Autònoma de Barcelona, Carrer del Dr Aiguader 88, E-08003 Barcelona, Spain
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Wark PA, Van der Kuil W, Ploemacher J, Van Muijen GNP, Mulder CJJ, Weijenberg MP, Kok FJ, Kampman E. Diet, lifestyle and risk of K-ras mutation-positive and -negative colorectal adenomas. Int J Cancer 2006; 119:398-405. [PMID: 16477638 DOI: 10.1002/ijc.21839] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
K-ras mutation-positive (K-ras+) and -negative (K-ras-) colorectal adenomas may differ clinically and pathologically. As environmental compounds may cause mutations in the growth-related K-ras oncogene or affect clonal selection depending on mutational status, we evaluated whether the aetiology of K-ras+ and K-ras- adenomas differs. K-ras mutations in codons 12 and 13 were assessed in colorectal adenoma tissue (K-ras+: n = 81, K-ras-: n = 453). Dietary and lifestyle data were collected through questionnaires that were also administered to 709 polyp-free controls. Multiple logistic regression analyses showed that intake of vitamin B2 and monounsaturated fat were differently associated with risk of K-ras+ and K-ras- adenomas; vitamin B2 was inversely associated with K-ras- (highest vs. lowest tertile: odds ratio (OR) = 0.70, 95% confidence interval (CI) = 0.50-0.97, p trend = 0.020), but not with K-ras+ adenomas, and a positive association with monounsaturated fat was confined to K-ras- adenomas (OR = 1.57, 95% CI = 1.06-2.34, p trend = 0.029). Besides, potential, not statistically significant, differences in risk arose because red meat was distinctly positively associated with K-ras+ adenomas (OR = 1.70, 95% CI = 0.94-3.09, p trend = 0.061); total dietary and polyunsaturated fat tended to be inversely associated with risk of K-ras+ but not of K-ras- adenomas; inverse associations with dairy products, calcium, protein and tea were confined to K-ras- adenomas, and smoking was more markedly positively associated with K-ras- adenomas. No differences in risk of K-ras+ and K-ras- adenomas could be detected for other factors. In conclusion, dietary and lifestyle factors may influence risk of K-ras+ and K-ras- adenomas differently. However, epidemiological literature on diet, lifestyle and colorectal K-ras mutations is inconsistent.
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Affiliation(s)
- Petra A Wark
- Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands
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Huber WW, Parzefall W. Modification of N‐Acetyltransferases and Glutathione S‐Transferases by Coffee Components: Possible Relevance for Cancer Risk. Methods Enzymol 2005; 401:307-41. [PMID: 16399395 DOI: 10.1016/s0076-6879(05)01020-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Enzymes of xenobiotic metabolism are involved in the activation and detoxification of carcinogens and can play a pivotal role in the susceptibility of individuals toward chemically induced cancer. Differences in such susceptibility are often related to genetically predetermined enzyme polymorphisms but may also be caused by enzyme induction or inhibition through environmental factors or in the frame of chemopreventive intervention. In this context, coffee consumption, as an important lifestyle factor, has been under thorough investigation. Whereas the data on a potential procarcinogenic effect in some organs remained inconclusive, epidemiology has clearly revealed coffee drinkers to be at a lower risk of developing cancers of the colon and the liver and possibly of several other organs. The underlying mechanisms of such chemoprotection, modifications of xenobiotic metabolism in particular, were further investigated in rodent and in vitro models, as a result of which several individual chemoprotectants out of the >1000 constituents of coffee were identified as well as some strongly metabolized individual carcinogens against which they specifically protected. This chapter discusses the chemoprotective effects of several coffee components and whole coffee in association with modifications of the usually protective glutathione-S-transferase (GST) and the more ambivalent N-acetyltransferase (NAT). A key role is played by kahweol and cafestol (K/C), two diterpenic constituents of the unfiltered beverage that were found to reduce mutagenesis/tumorigenesis by strongly metabolized compounds, such as 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine, 7,12-dimethylbenz[a]anthracene, and aflatoxin B(1), and to cause various modifications of xenobiotic metabolism that were overwhelmingly beneficial, including induction of GST and inhibition of NAT. Other coffee components such as polyphenols and K/C-free coffee are also capable of increasing GST and partially of inhibiting NAT, although to a somewhat lesser extent.
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Affiliation(s)
- Wolfgang W Huber
- Institut für Krebsforchung, Department of Toxicology, Medical University of Vienna, Austria
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Porta M, Ayude D, Alguacil J, Jariod M. Exploring environmental causes of altered ras effects: fragmentation plus integration? Mol Carcinog 2003; 36:45-52. [PMID: 12557259 DOI: 10.1002/mc.10093] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Mutations in ras genes are the most common abnormality of oncogenes in human cancer and a major example of activation by point mutation. Experimental and epidemiological studies support the notion that Ki-ras activation and expression may be chemically related. We discuss the potential role of several environmental compounds in the induction or promotion of ras mutations in humans, with a focus on exocrine pancreatic cancer, the human tumor with the highest prevalence at diagnosis of Ki-ras mutations. Organochlorine compounds, organic solvents, and coffee compounds may play an indirect role in causing Ki-ras mutations, rather than as direct inducers of the mutations. Although for some organochlorine compounds the induction of point mutations in ras oncogenes cannot be excluded, it seems more likely that the effects of these compounds are mediated through nongenomic or indirectly genotoxic mechanisms of action. Organic solvents also may act via enzymatic induction of ras mutagens or by providing a proliferation advantage to ras-mutated cell clones. In exocrine pancreatic cancer, caffeine, other coffee compounds, or other factors with which coffee drinking is associated could modulate Ki-ras activation by interfering with DNA repair, cell-cycle checkpoints, and apoptosis. Asbestos, cigarette smoking, and some dietary factors also may be involved in the initiation or the promotion of Ki-ras mutations in lung and colon cancers. Further development of the mechanistic scenarios proposed here could contribute to a meaningful integration of biological, clinical, and environmental knowledge on the causes of altered ras effects.
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Affiliation(s)
- Miquel Porta
- Institut Municipal d'Investigació Médica, Barcelona, Spain
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14
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Abstract
Mutations seem to be only one of the mechanisms involved in carcinogenesis; selection of mutated clones is a second crucial mechanism. An evolutionary (darwinian) theory of carcinogenesis can be useful to explain some contradictory observations of epidemiology, and to provide a common theoretical framework for carcinogenesis. In both the selection of species and in carcinogenesis (selection of mutated cells), mutation and selection can be interpreted as necessary and insufficient causes. Selection presupposes competition among clones-that is, survival advantage of the mutated species; without selective forces a mutation is mute, while the lack of mutations makes selective advantage impossible. The identification of carcinogen related fingerprints is ambiguous: it can suggest both a genuine mutational hotspot left by the carcinogenic stimulus (like in tobacco related p53 mutations), and selective advantage of clones whose mutations seem to be not exposure specific (like in the case of aflatoxin). We present several examples of exposures that can increase the risk of cancer in humans not via mutations but through a putative mechanism of clone selection.
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Affiliation(s)
- P Vineis
- CPO-Piemonte and Università di Torino, Italy.
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Costentin L, Pagès P, Bouisson M, Berthelémy P, Buscail L, Escourrou J, Pradayrol L, Vaysse N. Frequent deletions of tumor suppressor genes in pure pancreatic juice from patients with tumoral or nontumoral pancreatic diseases. Pancreatology 2002; 2:17-25. [PMID: 12120000 DOI: 10.1159/000049443] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND/AIMS K-ras codon 12 mutation is the most frequent genetic alteration in pancreatic cancer. Sensitivity and specificity of K-ras are not high enough to detect all pancreatic cancers, especially at early stage. This study investigated whether detection of p16 and/or DPC4 deletions along with K-ras mutation in DNA samples could improve the definition of patients at risk of pancreatic cancer. METHODS K-ras mutations were investigated by sequencing. p16 and DPC4 homozygous deletions were studied using comparative multiplex polymerase chain reaction of DNA in pancreatic juice sampled during endoscopic retrograde pancreatography in 57 patients with either pancreatic cancer (group I, 18 patients), chronic pancreatitis (group II, 20 patients), or nontumoral pancreatobiliary disease (group III, 19 patients). RESULTS The frequencies of Ki-ras mutations were 61% in group I, 10% in group II, and 10.5% in group III. The frequencies of p16 exon 2 and DPC4 deletions were, respectively, 28 and 36% in group I, 50 and 58% in group II, and 24 and 36% in group III. CONCLUSIONS The combination of p16 and DPC4 deletions with K-ras mutation does not improve the diagnosis of pancreatic cancer based on K-ras mutation alone. These data suggest that tumor suppressor gene inactivation can occur with a high frequency during nonmalignant pancreatic diseases.
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Affiliation(s)
- Lydie Costentin
- INSERM, U531 Biologie, Pathologie Digestive et Département de Gastroentérologie, CHU Rangueil, 1, avenue J.-Poulhès F-31403 Toulouse, France
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Porta M. Role of organochlorine compounds in the etiology of pancreatic cancer: a proposal to develop methodological standards. Epidemiology 2001; 12:272-6. [PMID: 11246593 DOI: 10.1097/00001648-200103000-00024] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Studies on the possible role of organochlorine compounds in the etiology of pancreatic and other cancers face a set of methodologic and logistic issues that stem from the lipophilic nature of most organochlorines, and from the fact that tumor-induced lipid mobilization, weight loss, and metabolic changes can be profound before diagnosis. The question thus arises: do the xenobiotic concentrations in blood and adipose tissue result, in part, from such pathophysiologic changes? To assess and control potential selection and information biases, a flexible framework is warranted. It could be based on indicators such as time elapsed between the first symptom of cancer and blood or fat sample extraction; signs, symptoms and clinical status at the time of extraction; cholesterol and triglycerides levels; other laboratory findings; tumor stage at diagnosis; diagnostic procedures; treatment type and timing; clinical complications; and survival. Before adopting qualitative criteria and quantitative standards, their impact upon causal estimators should be assessed empirically.
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Affiliation(s)
- M Porta
- Grup de Recerca en Epidemiologia Clínica i Molecular del Càncer, Institut Municipal d'Investigació Mèdica, Universitat Autònoma de Barcelona, Spain
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Porta M, Costafreda S, Malats N, Guarner L, Soler M, Gubern JM, García-Olivares E, Andreu M, Salas A, Corominas JM, Alguacil J, Carrato A, Rifà J, Real FX. Validity of the hospital discharge diagnosis in epidemiologic studies of biliopancreatic pathology. PANKRAS II Study Group. Eur J Epidemiol 2000; 16:533-41. [PMID: 11049097 DOI: 10.1023/a:1007692408457] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND The aim was to analyse the magnitude, direction and predictors of change in the main hospital discharge diagnosis (HDD) after a clinical expert review, among patients included in a multicentre molecular epidemiologic study of biliopancreatic diseases. METHODS A total of 602 patients with a suspicion diagnosis of pancreas cancer (PC), cancer of the extrahepatic biliary system (CEBS) or benign biliopancreatic pathologies (BPP) were prospectively recruited at five general hospitals. A structured form was used to collect information from medical records. A panel of experts revised all diagnostic information and established the main clinicopathological diagnosis (CPD) by consensus. RESULTS Of the 204 cases with a HDD of PC, 176 (86%) were deemed to have a CPD of PC, eight of CEBS, twelve a neoplasm of different origin, four BPP and four syndromic diagnoses. Thus, 28 cases (14%) were false positives. Of the 129 patients with a HDD of CEBS, 15 (12%) were false positives. Nine of the 396 cases with a HDD of non-PC (2%) had a CPD of PC (false negatives), whilst 14 of 471 patients with a HDD of non-CEBS (3%) were deemed to have CEBS. Overall, sensitivity and specificity of HDD for PC were, respectively, 95 and 93%, and for CEBS, 89 and 97%. Cytohistological confirmation and laparotomy were independent predictors of diagnostic change. CONCLUSIONS Validity of the HDD was high, but its association with some clinical variables suggests that sole reliance on HDD can significantly bias results, and highlights the need to review all HDDs. Alternatively, only patients at high risk of misdiagnosis could be reviewed: primarily, those lacking a cytohistological diagnosis or a laparotomy. No exclusions appear warranted solely on the basis of age, gender or tumour spread.
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Affiliation(s)
- M Porta
- Institut Municipal d'Investigació Mèdica, Universitat Autònoma de Barcelona, Spain.
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