Epidemiological evidence of the effects of behaviour and the environment on the risk of human cancer

Oxidative Stress and X-ray Exposure Levels-Dependent Survival and Metabolic Changes in Murine HSPCs

Haematopoietic bone marrow cells are amongst the most sensitive to ionizing radiation (IR), initially resulting in cell death or genotoxicity that may later lead to leukaemia development, most frequently Acute Myeloid Leukaemia (AML). The target cells for radiation-induced Acute Myeloid Leukaemia (rAML) are believed to lie in the haematopoietic stem and progenitor cell (HSPC) compartment. Using the inbred strain CBA/Ca as a murine model of rAML, progress has been made in understanding the underlying mechanisms, characterisation of target cell population and responses to IR. Complex regulatory systems maintain haematopoietic homeostasis which may act to modulate the risk of rAML. However, little is currently known about the role of metabolic factors and diet in these regulatory systems and modification of the risk of AML development. This study characterises cellular proliferative and clonogenic potential as well as metabolic changes within murine HSPCs under oxidative stress and X-ray exposure. Ambient oxygen (normoxia; 20.8% O2) levels were found to increase irradiated HSPC-stress, stimulating proliferative activity compared to low oxygen (3% O2) levels. IR exposure has a negative influence on the proliferative capability of HSPCs in a dose-dependent manner (0-2 Gy) and this is more pronounced under a normoxic state. One Gy x-irradiated HSPCs cultured under normoxic conditions displayed a significant increase in oxygen consumption compared to those cultured under low O2 conditions and to unirradiated HSPCs. Furthermore, mitochondrial analyses revealed a significant increase in mitochondrial DNA (mtDNA) content, mitochondrial mass and membrane potential in a dose-dependent manner under normoxic conditions. Our results demonstrate that both IR and normoxia act as stressors for HSPCs, leading to significant metabolic deregulation and mitochondrial dysfunctionality which may affect long term risks such as leukaemia.

Cancer rates not explained by smoking: a county-level analysis

BACKGROUND

Debates over the importance of "lifestyle" versus "environment" contributions to cancer have been going on for over 40 years. While it is clear that cigarette smoking is the most significant cancer risk factor, the contributions of occupational and environmental carcinogens in air, water and food remain controversial. In practice, most cancer prevention messaging focuses on reducing cigarette smoking and changing other personal behaviors with little mention of environmental chemicals, despite widespread exposure to many known carcinogens. To inform decision-making on cancer prevention priorities, we evaluated the potential impact of smoking cessation on cancer rates.

METHODS

Using cancer incidence data from 612 counties in the SEER database, and county-level smoking prevalences, we investigated the impact of smoking cessation on incidence for 12 smoking-related cancer types, 2006-2016. A multilevel mixed-effects regression model quantified the association between county-level smoking prevalence and cancer incidence, adjusting for age, gender and variability over time and among counties. We simulated complete smoking cessation and estimated the effects on county-level cancer rates.

RESULTS

Regression models showed the expected strong association between smoking prevalence and cancer incidence. Simulating complete smoking cessation, the incidence of the 12 smoking-related cancer types fell by 39.8% (54.9% for airways cancers; 28.9% for non-airways cancers). And, while the actual rates of smoking-related cancers from 2006 to 2016 declined (annual percent change (APC) = - 0.8, 95% CI = - 1.0 to - 0.5%), under the scenario of smoking elimination, the trend in cancer incidence at these sites was not declining (APC = - 0.1, 95% CI = - 0.4 to + 0.1%). Not all counties were predicted to benefit equally from smoking elimination, and cancer rates would fall less than 10% in some counties.

CONCLUSIONS

Smoking prevention has produced dramatic reductions in cancer in the US for 12 major types. However, we estimate that eliminating smoking completely would not affect about 60% of cancer cases of the 12 smoking-related types, leaving no improvement in the incidence trend from 2006 to 2016. We conclude that cancer prevention strategies should focus not only on lifestyle changes but also the likely contributions of the full range of risk factors, including environmental/occupational carcinogens.

Estimates of the incidence of infection-related cancers in Italy and Italian regions in 2018

Introduction

Chronic infections and infestations represent one of the leading causes of cancer. Eleven agents have been categorized by the International Agency for Research on Cancer (IARC) in Group 1, 3 in Group 2A and 4 in Group 2B. We previously estimated that the incidence of cancers associated with infectious agents accounted for the 8.5% of new cancer cases diagnosed in Italy in 2014.

Methods

In the present study we evaluated the incidence of cancer in Italy and in the 20 Italian regions in 2018, based on the data of Cancer Registries, and calculated the fraction attributable to infectious agents.

Results

Cancers of infectious origin contributed to the overall burden of cancer in Italy with more than 27,000 yearly cases, the 92% of which was attributable to Helicobacter pylori, human papillomaviruses, and hepatitis B and C viruses. With the exception of papillomavirus-related cancers, the incidence of cancers of infectious origin was higher in males (16,000 cases) than in females (11,000 cases). There were regional and geographical variations of cancers depending on the type of cancer and on the gender. Nevertheless, the overall figures were rather similar, the infection-related cancers accounting for the 7.2, 7.6, and 7.1% of all cancers in Northern, Central, and Southern Italy, respectively.

Conclusions

The estimate of the incidence of cancers attributable to infectious agents in Italy in 2018 (7.3% of all cancer cases) is approximately half of the worldwide burden, which has been estimated by IARC to be the 15.4% of all cancer cases in 2012.

Influence of diet and metabolism on hematopoietic stem cells and leukemia development following ionizing radiation exposure

PURPOSE

The review aims to discuss the prominence of dietary and metabolic regulators in maintaining hematopoietic stem cell (HSC) function, long-term self-renewal, and differentiation.

RESULTS

Most adult stem cells are preserved in a quiescent, nonmotile state in vivo which acts as a "protective state" for stem cells to reduce endogenous stress provoked by DNA replication and cellular respiration as well as exogenous environmental stress. The dynamic balance between quiescence, self-renewal and differentiation is critical for supporting a functional blood system throughout life of an organism. Stress-conditions, for example ionizing radiation exposure can trigger the blood forming HSCs to proliferate and migrate through extramedullary tissues to expand the number of HSCs and increase hematopoiesis. In addition, a wealth of investigation validated that deregulation of this balance plays a critical pathogenic role in various different hematopoietic diseases including the leukemia development.

CONCLUSION

The review summarizes the current knowledge on how alterations in dietary and metabolic factors could alter the risk of leukemia development following ionizing radiation exposure by inhibiting or even reversing the leukemic progression. Understanding the influence of diet, metabolism, and epigenetics on radiation-induced leukemogenesis may lead to the development of practical interventions to reduce the risk in exposed populations.

Pyrazine, 2-ethylpyridine, and 3-ethylpyridine are cigarette smoke components that alter the growth of normal and malignant human lung cells, and play a role in multidrug resistance development

Lung cancer is one of the few human diseases for which the primary etiological agent, cigarette smoke (CS), has been described; however, the precise role of individual cigarette smoke toxicant in tumor development and progression remains to be elusive. The purpose of this study was to assess in vitro the effects of previously identified cigarette smoke components, pyrazine, 2-ethylpyridine, and 3-ethylpyridine, on non-tumorigenic (MRC5) and adenocarcinomic (A549) human lung cell lines. Our data showed that the administration of three cigarette smoke components in combination perturbed the proliferation of both normal and adenocarcinomic cells. Study of malignant cells revealed that CS components were cytotoxic at high concentration (10(-6) M) and stimulatory in a dose-dependent manner at lower concentrations (10(-8) M to 10(-10) M). This adverse effect was enhanced when adenocarcinomic cells were maintained in hypoxia resembling intratumoral environment. Furthermore, exposure to pyrazine, 2-ethylpyridine, and 3-ethylpyridine induced oxidative stress in both normal and malignant cells. Finally, assessment of P-gp activity revealed that multidrug resistance was induced in CS component exposed adenocarcinomic lung cells and the induction was augmented in hypoxia. Taken together, pyrazine, 2-ethylpyridine, and 3-ethylpyridine adversely altered both normal and diseased lung cells in vitro and data collected from this study may help lung cancer patients to understand the importance of quitting smoking during lung cancer treatment.

Influence of food condiments on the formation of carcinogenic heterocyclic amines in cooked chicken and determination by LC-MS/MS

Heterocyclic amines (HCAs) are known to be suspected human carcinogens produced by high-temperature cooking of protein-rich foods such as meat and fish. In the present study, the influence of numerous food condiments on the formation of HCAs in cooked chicken was investigated. Chicken samples were subjected to pan-frying under controlled temperature. The levels of HCAs DMIP, MeIQx, 4,8-DiMeIQx, PhIP, harman and norharman were found to be between 0.93 and 27.52 ng g(-1), whereas IQ, MeIQ, AαC, MeAαC, Trp-P-1 and Trp-P-2 were found either below the limit of quantification or not detected in the control sample. Nevertheless, for samples cooked using food condiments, the amounts of HCAs (DMIP, MeIQx, 4,8-DiMeIQx and PhIP) were between 0.14 and 19.57 ng g(-1); harman and norharman were detected at higher concentrations up to 17.77 ng g(-1) while IQ and MeIQ were at levels below the limit of quantification; and AαC, MeAαC, Trp-P-1 and Trp-P-2 were not detected in any of the samples. The outcomes revealed that the formation of HCAs (except harman and norharman) diminished after the addition of food condiments. Edible oil contributed to the highest levels of HCA formation, followed by garlic, paprika, pepper and tomato.

Epithelial cancers in the post-genomic era: should we reconsider our lifestyle?

The age-related epithelial cancers of the breast, colorectum and prostate are the most prevalent and are increasing in our aging populations. Epithelial cells turnover rapidly and mutations naturally accumulate throughout life. Most epithelial cancers arise from this normal mutation rate. All elderly individuals will harbour many cells with the requisite mutations and most will develop occult neoplastic lesions. Although essential for initiation, these mutations are not sufficient for the progression of cancer to a life-threatening disease. This progression appears to be dependent on context: the tissue ecosystem within individuals and lifestyle exposures across populations of individuals. Together, this implies that the seeds may be plentiful but they only germinate in the right soil. The incidence of these cancers is much lower in Eastern countries but is increasing with Westernisation and increases more acutely in migrants to the West. A Western lifestyle is strongly associated with perturbed metabolism, as evidenced by the epidemics of obesity and diabetes: this may also provide the setting enabling the progression of epithelial cancers. Epidemiology has indicated that metabolic biomarkers are prospectively associated with cancer incidence and prognosis. Furthermore, within cancer research, there has been a rediscovery that a switch in cell metabolism is critical for cancer progression but this is set within the metabolic status of the host. The seed may only germinate if the soil is fertile. This perspective brings together the different avenues of investigation implicating the role that metabolism may play within the context of post-genomic concepts of cancer.

Cancer incidence in Morocco: report from Casablanca registry 2005-2007

INTRODUCTION

Few population-based cancer registries are in place in developing countries. In order to know the burden of cancer in Moroccan population, cancer registry initiative was put in place in the Casablanca district, the biggest city of Morocco.

METHODS

The data collected covers 3.6 millions inhabitant and included Casablanca city and the administrative region.

RESULTS

The data collected in the years 2005-07 show that the top 5 forms of cancers in women were breast (ASR: 36.4 per 100,000), cervical (15.0), thyroid (6.7), colon-rectum (5.8), and ovarian (5.3); the top 5 cancers in men were lung (25.9), prostate (13.5), bladder (8.7), colon-rectum (8.1) and non-Hodgkin lymphoma (7.2). Tumours of haematopoietic and lymphoid tissues represented 11% of all cancers (skin excluded); some presented unusual sex ratios. For breast, cervical, colorectal and thyroid cancer, respectively 57%, 42%, 28% and 60% of the cases were under 50 years of age. This was attributable to particularly low numbers of cases recorded among old people, and the young age of the general population; the observed age-specific incidences under age 50 were not higher than in western countries. Cancers at young ages were particularly common in women: 67% of the cases were under 50. Stage at diagnosis could be obtained for 82% of the breast cancer cases and was as follows: 28% local, 63% regional and 9% distant, in the absence of screening.

CONCLUSION

These first population-based data have provided an invaluable resource for the national cancer control plan of Morocco, and will be useful tool to its future evaluation.

The high harm score of alcohol. Time for drug policy to be revisited?

The aim of this paper is to create awareness of the negative health impact and economic burden and benefits associated to alcohol consumption. Worldwide about two billion people consume alcohol. Low intake of alcohol has a minor protective cardiovascular effect. On the other hand, even moderate alcohol consumption appears to be weakly, but significantly, associated to a limited number of chronic diseases. Alcohol causes a considerable economic burden to society due to the high absolute number of alcohol consumers. As such, alcohol abuse is more harmful for public health and society than illicit drug use. Some 3.7% of alcohol consumers (worldwide 76 million people) have an alcohol use disorder leading to 60-70% of the societal costs related to alcohol. Therefore, policy measures should, in addition to regulatory measures to reduce alcohol use, aim at closing the treatment gap and improving treatment effectiveness of people with an alcohol use disorder. The key message is that policy-makers unjustifiably focus on the harm of illicit drugs, whereas they underestimate the harm of alcohol use. Policy makers should therefore consider alcohol to be at least as harmful as illicit drugs and invest more in prevention and harm reduction strategies for alcohol abuse and dependence.

Occupational and environmental causes of lung cancer

Because tobacco smoking is a potent carcinogen, secondary causes of lung cancer are often diminished in perceived importance. The goal of this review is to describe the occurrence and recent findings of the 27 agents currently listed by the International Agency for Research on Cancer (IARC) as lung carcinogens. The IARC's updated assessments of lung carcinogens provide a long-overdue resource for consensus opinions on the carcinogenic potential of various agents. Supplementary new information, with a focus on analytic epidemiologic studies that has become available since IARC's most recent evaluation, are also discussed.

Cancer risk and the complexity of the interactions between environmental and host factors: HENVINET interactive diagrams as simple tools for exploring and understanding the scientific evidence

BACKGROUND

Development of graphical/visual presentations of cancer etiology caused by environmental stressors is a process that requires combining the complex biological interactions between xenobiotics in living and occupational environment with genes (gene-environment interaction) and genomic and non-genomic based disease specific mechanisms in living organisms. Traditionally, presentation of causal relationships includes the statistical association between exposure to one xenobiotic and the disease corrected for the effect of potential confounders.

METHODS

Within the FP6 project HENVINET, we aimed at considering together all known agents and mechanisms involved in development of selected cancer types. Selection of cancer types for causal diagrams was based on the corpus of available data and reported relative risk (RR). In constructing causal diagrams the complexity of the interactions between xenobiotics was considered a priority in the interpretation of cancer risk. Additionally, gene-environment interactions were incorporated such as polymorphisms in genes for repair and for phase I and II enzymes involved in metabolism of xenobiotics and their elimination. Information on possible age or gender susceptibility is also included. Diagrams are user friendly thanks to multistep access to information packages and the possibility of referring to related literature and a glossary of terms. Diagrams cover both chemical and physical agents (ionizing and non-ionizing radiation) and provide basic information on the strength of the association between type of exposure and cancer risk reported by human studies and supported by mechanistic studies. Causal diagrams developed within HENVINET project represent a valuable source of information for professionals working in the field of environmental health and epidemiology, and as educational material for students.

INTRODUCTION

Cancer risk results from a complex interaction of environmental exposures with inherited gene polymorphisms, genetic burden collected during development and non genomic capacity of response to environmental insults. In order to adopt effective preventive measures and the associated regulatory actions, a comprehensive investigation of cancer etiology is crucial. Variations and fluctuations of cancer incidence in human populations do not necessarily reflect environmental pollution policies or population distribution of polymorphisms of genes known to be associated with increased cancer risk. Tools which may be used in such a comprehensive research, including molecular biology applied to field studies, require a methodological shift from the reductionism that has been used until recently as a basic axiom in interpretation of data. The complexity of the interactions between cells, genes and the environment, i.e. the resonance of the living matter with the environment, can be synthesized by systems biology. Within the HENVINET project such philosophy was followed in order to develop interactive causal diagrams for the investigation of cancers with possible etiology in environmental exposure.

RESULTS

Causal diagrams represent integrated knowledge and seed tool for their future development and development of similar diagrams for other environmentally related diseases such as asthma or sterility. In this paper development and application of causal diagrams for cancer are presented and discussed.

Cancer and environment: definitions and misconceptions

BACKGROUND

Scientific evidence supports an association between environmental exposures and cancer. However, a reliable estimate for the proportion of cancers attributable to environmental factors is currently unavailable. This may be related to the varying definitions of the term "environment." The current review aims to determine how the reporting of the definition of the environment and of the estimates of environmentally attributable risks have changed over the past 50 years.

METHODS

A systematic literature search was performed to retrieve all relevant publications relating to the environment and cancer from January 1960 to December 2010 using PubMed, EMBASE, Scopus, and Web of Science. Definitions of the environment and environmentally attributable risks for cancer were extracted from each relevant publication.

RESULTS

The search resulted in 261 relevant publications. We found vast discrepancies in the definition of the environment, ranging from broad (including lifestyle factors, occupational exposures, pollutants, and other non-genetic factors) to narrow (including air, water, and soil pollutants). Reported environmentally attributable risk estimates ranged from 1% to 100%.

CONCLUSIONS

Our findings emphasize the discrepancies in reporting environmental causation of cancer and the limits of inference in interpreting environmentally attributable risk estimates. Rather than achieving consensus on a single definition for the environment, we suggest the focus be on achieving transparency for any environmentally attributable risks.

A current global view of environmental and occupational cancers

This review is focused on current information of avoidable environmental pollution and occupational exposure as causes of cancer. Approximately 2% to 8% of all cancers are thought to be due to occupation. In addition, occupational and environmental cancers have their own characteristics, e.g., specific chemicals and cancers, multiple factors, multiple causation and interaction, or latency period. Concerning carcinogens, asbestos/silica/wood dust, soot/polycyclic aromatic hydrocarbons [benzo(a) pyrene], heavy metals (arsenic, chromium, nickel), aromatic amines (4-aminobiphenyl, benzidine), organic solvents (benzene or vinyl chloride), radiation/radon, or indoor pollutants (formaldehyde, tobacco smoking) are mentioned with their specific cancers, e.g., lung, skin, and bladder cancers, mesothelioma or leukemia, and exposure routes, rubber or pigment manufacturing, textile, painting, insulation, mining, and so on. In addition, nanoparticles, electromagnetic waves, and climate changes are suspected as future carcinogenic sources. Moreover, the aspects of environmental and occupational cancers are quite different between developing and developed countries. The recent follow-up of occupational cancers in Nordic countries shows a good example for developed countries. On the other hand, newly industrializing countries face an increased burden of occupational and environmental cancers. Developing countries are particularly suffering from preventable cancers in mining, agriculture, or industries without proper implication of safety regulations. Therefore, industrialized countries are expected to educate and provide support for developing countries. In addition, citizens can encounter new environmental and occupational carcinogen nominators such as nanomaterials, electromagnetic wave, and climate exchanges. As their carcinogenicity or involvement in carcinogenesis is not clearly unknown, proper consideration for them should be taken into account. For these purposes, new technologies with a balance of environment and gene are required. Currently, various approaches with advanced technologies--genomics, exposomics, etc.--have accelerated development of new biomarkers for biological monitoring of occupational and environmental carcinogens. These advanced approaches are promising to improve quality of life and to prevent occupational and environmental cancers.

The prevention of infection-associated cancers

Collectively, chronic viral and bacterial infections and trematode infestations have been estimated to be associated with approximately one of five human cancers worldwide. The fraction attributable to each one of the chronic infections caused by hepatitis B and C viruses (HBV and HCV), human papillomaviruses (HPV) and Helicobacter pylori, is ∼5%. These infections are the most important causes of major types of cancer, including hepatocellular carcinoma, cervical cancer and stomach cancer, respectively. Taking into account the mechanisms of infection-related carcinogenesis, integrated approaches are addressed to the control of the associated infection as well as to avoidance of cancer occurrence and progression. Large-scale interventions have been implemented, such as the anti-HBV and anti-HPV routine vaccination programs. The latter has been designed with the specific goal of preventing HPV-associated cancers, which is an outstanding breakthrough in cancer prevention. Intriguingly, not only prevention but even therapy of an infectious disease and eradication of a pathogen become a crucial tool for the primary prevention of these cancers. An important role is also played by secondary prevention (e.g. Pap test and DNA testing for HPV-associated cervical cancers) and by tertiary prevention (e.g. antiangiogenesis in Kaposi's sarcoma). The present article reviews the microbial and parasitic diseases that have been associated so far with human cancers, draws an overview of their burden in cancer epidemiology, deals with applicable prevention strategies and provides examples of co-ordinated approaches to the control of cancers associated with HBV, HCV, HPV, human immunodeficiency virus and H.pylori infections.

Cancer-related disparities and opportunities for intervention in Northern Plains American Indian communities

OBJECTIVES

We examined behavioral trends associated with cancer risk and cancer screening use from 1997 through 2006 among American Indians/Alaska Natives (AI/ANs) in the Northern Plains region (North Dakota, South Dakota, Nebraska, and Iowa) of the United States. We also examined disparities between that population and non-Hispanic white (NHW) people in the Northern Plains and AI/ANs in other regions.

METHODS

We analyzed Behavioral Risk Factor Surveillance System data from the Centers for Disease Control and Prevention for 1997-2000 and 2003-2006. We used age-adjusted Wald Chi-square tests to test the difference between these two periods for AI/ANs and the difference between AI/ANs and NHW people during 2003-2006.

RESULTS

There was no statistically significant improvement among AI/ANs in the Northern Plains region for behaviors associated with cancer risk or cancer screening use, and there was a significant increase in the obesity rate. The prevalence of binge drinking, obesity, and smoking among AI/ANs in the Northern Plains was significantly higher than among NHW people in the same region and among AI/AN populations in other regions. Although the percentage of cancer screening use was similar for all three groups, the use of sigmoidoscopy/colonoscopy was significantly lower among the Northern Plains AI/ANs than among NHW people.

CONCLUSION

These results indicate a need for increased efforts to close the gaps in cancer health disparities between AI/ANs and the general population. Future efforts should focus not only on individual-level changes, but also on system-level changes to build infrastructure to promote healthy living and to increase access to cancer screening.

Intracellular heavy metal nanoparticle storage: progressive accumulation within lymph nodes with transformation from chronic inflammation to malignancy

A 25-year-old man had complained of sudden fever spikes for two years and his blood tests were within the normal range. In 1993, a surgical biopsy of swollen left inguinal lymph nodes was negative for malignancy, but showed reactive lymphadenitis and widespread sinus histiocytosis. A concomitant needle biopsy of the periaortic lymph nodes and a bone marrow aspirate were also negative. In 1994, after an emergency hospital admission because of a sport-related thoracic trauma, a right inguinal lymph node biopsy demonstrated Hodgkin’s lymphoma Stage IVB (scleronodular mixed cell subtype). Although it was improved by chemotherapy, the disease suddenly relapsed, and a further lymph node biopsy was performed in 1998 confirming the same diagnosis. Despite further treatment, the patient died of septic shock in 2004, at the age of 38 years. Retrospective analysis of the various specimens showed intracellular heavy metal nanoparticles within lymph node, bone marrow, and liver samples by field emission gun environmental scanning electron microscopy and energy dispersive spectroscopy. Heavy metals from environmental pollution may accumulate in sites far from the entry route and, in genetically conditioned individuals with tissue specificity, may act as cofactors for chronic inflammation or even malignant transformation. The present anecdotal report highlights the need for further pathologic ultrastructural investigations using serial samples and the possible role of intracellular nanoparticles in human disease.

Exploratory analysis of potential risk factors of a rare disease: spatial distribution of adrenocortical carcinoma in Israel as a case study

The underlying assumption of the proposed exploratory approach is that, if the geographic patterns of different diseases are compared, the cases of a 'subject' disease should occur closer to cases of a disease with similar environmental risk factors (etiology) and farther away from cases of a disease with different etiology. In the present study, the performance of proposed approach is investigated by cross-examination of the spatial patterns of three widespread cancers--lung, larynx and colorectal (CRC)--with that of a rare malignant disease--Adrenocortical Carcinoma (ACC). As the analysis indicates, the spatial distribution of ACC is more likely to be related to hereditary factors than to environmental causes, in accordance with current knowledge about this rare disease.

Cancer occurrence

In this chapter, we describe the variability of cancer occurrence by using measures of incidence, mortality, prevalence, and survival, according to demographic characteristics such as age, sex, socioeconomic status, and race/ethnicity, as well as geographic location and time period. We also discuss the variability of cancer occurrence in relation to changes in risk factors, screening rates, and improved treatments. The variation according to risk factors provides strong evidence that much of cancer is caused by environmental factors and is potentially avoidable.

Cancer as an endocrine problem

Many of the most common cancers that blight our societies are very rare in other large populations in the world; studies of migrants exclude a simple genetic explanation for these wide geographical variations and imply that environmental exposures are key determinants of the development of these cancers. The most heavily implicated factor is nutrition. There are many other clinical indicators that nutrition, energy balance and metabolic status are perturbed in large numbers of individuals in 'Westernized' societies. Many of the tissue morbidities associated with metabolic disturbance are mediated by the consequent hormonal perturbations, and it is likely that these endocrine controls also mediate the effects of nutrition and metabolic status on the development of many clinical cancers. The recent characterization of the genomic landscape of breast and colorectal cancers have established that a few cell signalling pathways are critical for the clinical course of these cancers, in particular cell signalling pathways that are also central to the regulation of cell metabolism. These signalling pathways are normally under hormonal control, and again this evidence suggests that these hormonal controls may determine the context that is permissive for the progression of clinical cancers. This new understanding indicates that many cancers are potentially preventable, and that nutrition, metabolic and endocrine interventions are the most promising strategies for disease prevention.

An optimised data analysis for the Balb/c 3T3 cell transformation assay and its application to metal compounds

The Balb/c3T3 cell transformation assay (CTA) is an available in vitro system to detect the carcinogenic potential of chemicals. Currently, the European Centre for the Validation of Alternative Methods (ECVAM) is validating this test, assessing its reliability and relevance. Its endpoint is the formation of type III foci, which is, when using clone A31-1-1, a very rare event that usually does not occur at all for negative controls. The carcinogenic potential of a compound tested is assessed by comparing the number of foci in treated and untreated cells. The objective of the present work is to optimise the data analysis for this endpoint by applying the most commonly used approach by a t-test and the Fisher's exact test as an alternative approach. For this purpose selected metal compounds classified as carcinogenic (NaAsO2, CdCl2, cisPt), as suspected carcinogenic (C6H5)4AsCl, CH3HgCl), or as compounds without evidence of carcinogenic properties in humans ((NH4)2PtCl6, NaVO3) as well as a non-carcinogenic (AgNO3) were analysed. Our evaluation revealed that the t-test approach, which assumes normality of data, is not appropriate. The results demonstrated that the statistical analysis by Fisher's exact test, better reflecting the data properties, greatly facilitates the interpretation of Balb/c3T3 CTA data regarding carcinogenic potential.

Environmental and occupational causes of cancer: A call to act on what we know

The discussion of the scientific evidence linking cancer to environmental and occupational exposures has been an area of contention for atleast the past three decades, since the assertion in 1977 by Higginson and Muir that 80% of all cancers were due to environmental exposures. Over the past three decades, there have been additional efforts to estimate the proportion of cancer due to these involuntary exposures, including the 1981 monograph by Doll and Peto and the more recent reports by the Harvard Center for Cancer Prevention. In this paper, we review the evidence that Doll and Peto and other authors have summarized, provide an alternative interpretation of the evidence, and caution against the very idea of attributing specific fractions or proportions of cancer to particular factors. We also review the scientific evidence, particularly epidemiologic evidence, regarding the contribution of environmental and occupational exposures to the overall cancer burden in the US. We conclude with a call for action to prevent exposures to environmental and occupational carcinogens.

Effects of caffeic acid phenethyl ester on the histopathological changes in the lungs of cigarette smoke-exposed rabbits

We aimed at evaluating the effects of caffeic acid phenethyl ester (CAPE) on the histopathological changes in the lungs of rabbits exposed to cigarette smoke exposure. Four groups with six rabbits each were as follows: cigarette smoke group, CAPE group, cigarette smoke + CAPE group and control group. The cigarette smoke group was exposed to cigarette smoke 1 hr daily for 1 month. The CAPE group was administered intraperitoneal CAPE. The CAPE + cigarette smoke group was both exposed to cigarette smoke and was administered intraperitoneal CAPE. The control group was exposed to clean air. After 1 month, the rabbits were killed and the lung tissues were examined histopathologically. Peribronchial and intraparenchymal inflammation, intraparenchymal vascular congestion and thrombosis, intraparenchymal haemorrhage, respiratory epithelial proliferation, number of macrophages in the bronchiolar and alveolar lumen, alveolar destruction, emphysematous changes and bronchoalveolar haemorrhage scores were significantly higher in the cigarette smoke group than in the control group. Administration of CAPE to cigarette smoke-exposed rabbits significantly prevented all these changes. CAPE seems to have significant preventive effects on the severe histopathological changes in the lungs associated with cigarette smoke exposure. However, in some instances, it may not alter the progression to fibrosis.

What does the public know about preventing cancer? Results from the Health Information National Trends Survey (HINTS)

This study provides information about the public's familiarity with cancer prevention strategies and examines the association between this familiarity and actual prevention behavior. Data from interviews with 5,589 adults included in the 2003 Health Information National Trends Survey (HINTS) were analyzed. Most respondents were able to cite one or two strategies for reducing the chances of cancer. On average, the fewest number of strategies were cited by Hispanics, respondents aged 65 years or older, and those with the lowest levels of education and income. Avoiding tobacco and eating a healthy diet were most commonly cited. People who cited the following strategies for preventing cancer were more likely to practice them: eating plenty of fruits and vegetables, exercising regularly, not smoking, and participating in cancer screening. Results indicate that efforts are needed to increase public familiarity with recommended strategies, especially among groups that are least familiar with recommendations for cancer prevention.

Gene-environment studies: any advantage over environmental studies?

Gene-environment studies have been motivated by the likely existence of prevalent low-risk genes that interact with common environmental exposures. The present study assessed the statistical advantage of the simultaneous consideration of genes and environment to investigate the effect of environmental risk factors on disease. In particular, we contemplated the possibility that several genes modulate the environmental effect. Environmental exposures, genotypes and phenotypes were simulated according to a wide range of parameter settings. Different models of gene-gene-environment interaction were considered. For each parameter combination, we estimated the probability of detecting the main environmental effect, the power to identify the gene-environment interaction and the frequency of environmentally affected individuals at which environmental and gene-environment studies show the same statistical power. The proportion of cases in the population attributable to the modeled risk factors was also calculated. Our data indicate that environmental exposures with weak effects may account for a significant proportion of the population prevalence of the disease. A general result was that, if the environmental effect was restricted to rare genotypes, the power to detect the gene-environment interaction was higher than the power to identify the main environmental effect. In other words, when few individuals contribute to the overall environmental effect, individual contributions are large and result in easily identifiable gene-environment interactions. Moreover, when multiple genes interacted with the environment, the statistical benefit of gene-environment studies was limited to those studies that included major contributors to the gene-environment interaction. The advantage of gene-environment over plain environmental studies also depends on the inheritance mode of the involved genes, on the study design and, to some extend, on the disease prevalence.

Environmental and Occupational Causes of Cancer Re-visited

We recently completed a review of scientific evidence, particularly epidemiologic evidence, regarding the contribution of environmental and occupational exposures to the overall cancer burden in the US. We evaluated the efforts to estimate the proportion of cancer due to these involuntary exposures, including the ambitious effort by Doll and Peto and an update by a group of authors at the Harvard Center for Cancer Prevention. In this paper, we critique these efforts, and their resulting estimates of the proportion of cancer due to various factors. We also provide an alternative interpretation of the evidence and a caution against the very idea of attributing specific fractions or proportions of cancer to particular factors. We conclude by recommending that environmental and occupational links to cancer be given serious consideration by individuals and institutions concerned with cancer prevention, particularly those involved in research and public education. We support the new initiative in the European Union to evaluate chemicals more fully before they reach the market.

Neighborhood composition and incidence of cancer among Hispanics in the United States

BACKGROUND

Hispanics in the United States have a 33% lower age-adjusted incidence of cancer and a 38% lower cancer mortality rate compared with non-Hispanic whites. This may be secondary to health behaviors that vary with residential and economic assimilation. The authors investigated whether cancer incidence among Hispanics increased with residential and economic assimilation into mainstream culture.

METHODS

Data from the Surveillance, Epidemiology, and End Results program (SEER) and the U.S. Census Bureau were used to compare cancer incidence rates and rate ratios as a function of percentage of Hispanics and income of Hispanics in a census tract. Type of cancer was identified with a site recode variable in the SEER data set. Cases with in situ prostate and cervical carcinoma were excluded. Hispanic ethnicity in SEER was identified by medical record review and Hispanic surname lists. The study also used income of Hispanics living in the census tract, age at diagnosis, and stratification by gender.

RESULTS

The incidence of breast, colorectal, and lung carcinoma among Hispanics increased as the percentage of Hispanics in the census tract decreased and as tract Hispanic income increased. For example, there was a 39% reduction in breast carcinoma and a 38% reduction in male colorectal carcinoma when the Hispanic population in high-density Hispanic neighborhoods in the lowest income quartile was contrasted to Hispanics living in tracts with the lowest total percentage of Hispanics in the highest income quartile.

CONCLUSIONS

The lower cancer rates among Hispanics relative to non-Hispanic whites in the United States may dissipate as Hispanics become more assimilated into the mainstream society.

Genotoxicity of tobacco smoke and tobacco smoke condensate: a review

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

Tobacco-smoke exposure indicators and urinary mutagenicity

In this study, the correlation of indicators of external (i.e. mean daily intake of condensate, nicotine, tobacco and tobacco proteins, and daily number of cigarettes smoked) and of internal tobacco-smoke exposure (i.e. urinary 1-pyrenol, nicotine and its metabolites and trans,trans-muconic acid) with urinary mutagenicity, detected on YG1024 Salmonella typhimurium strain with S9, were examined in 118 smokers. An increase in urinary mutagenicity was clearly significantly correlated with each external and internal indicators of exposure to tobacco smoke (correlation coefficient (r) ranging between 0.22 and 0.54, P<0.01), with a greater extent in the case of indicators of internal dose. In multiple regression analysis, among the indicators of external exposure, daily tobacco intake was the only variable significantly associated with urinary mutagenicity (t=2.47, P=0.015, with partial contribution to r(2)=5.15%). Instead, when all indicators of exposure (external and internal) were considered in the analysis, the influence of urinary 1-pyrenol on urinary mutagenicity was predominant, followed by those of urinary trans,trans-muconic acid and nicotine plus metabolites (t=4.63, 2.73 and 2.08, P<0.001, P=0.002 and 0.04, with partial contribution to r(2)=17.0, 6.66 and 3.96%, respectively), with no influence at all of external tobacco-smoke exposure indicators. In conclusion, our results show that indicators of internal dose are better correlated with formation of mutagens in urine of smokers. Among these, the best indicator was urinary 1-pyrenol and this result designates the combustion processes of tobacco as the determining step for the formation of urinary mutagens. However, as these biomarkers cannot be analysed the amount of daily tobacco intake represent the best valuable index of external (presumptive) exposure to tobacco-smoke genotoxins.

Environmental and heritable causes of cancer among 9.6 million individuals in the Swedish Family-Cancer Database

The genetic and environmental components in 15 common cancers were estimated using the nationwide Swedish Family-Cancer Database. Tetrachoric correlations were used to describe similarity in cancer liability among family members. Structural equation modeling was used to derive estimates of the importance of genetic and environmental effects. Statistically significant estimates of proportion of cancer susceptibility, accounted for by genetic effects, were obtained for all studied cancers except for leukemia. The estimate was highest in thyroid cancer (53%), followed by tumors at endocrine glands (28%), testis (25%), breast (25%), cervix (22%), melanoma (21%), colon (13%), nervous system (12%), rectum (12%), non-Hodgkin lymphoma (10%), lung (8%), kidney (8%), urinary bladder (7%), stomach (1%) and leukemia (1%). The estimates of shared environmental effects ranged from 0% (cervix) to 15% (stomach). The childhood shared environmental effects were most important in testicular cancer (17%), stomach cancer (13%) and cervix in situ (13%). Our results indicate that environment has a principal causative role in cancer at all studied sites except for thyroid. The relatively large effect of heritability in cancer at some sites, on the other hand, indicates that even though susceptibility genes have been described at many cancer sites, they are likely to explain only part of the genetic effects.