Effects of vitamin E and selenium supplementation on esophageal adenocarcinogenesis in a surgical model with rats

Associations of trace element levels in paired serum, whole blood, and tissue: an example of esophageal squamous cell carcinoma

Previous studies have extensively explored impacts of trace elements on human beings and complex relationships with cancers. However, contradictory conclusions may be more challenging to explain due to biological specimen differences. To investigate the distribution of trace elements inside body, we collected serum, whole blood and tissues from 77 patients with esophageal squamous cell carcinoma (ESCC), as well as serum and whole blood from 100 healthy individuals, and determined the concentrations of 13 elements (Al, V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Sr, Cd, and Pb) with inductively coupled plasma-mass spectrometry (ICP-MS). Al, Ni, Cu, Sr, and Cd variations between patients and controls were found to be inconsistent in serum and blood. Concentrations of Cu, As, Se, and Sr in serum were positively correlated with that in whole blood in both case and control group (r_s >0.450, P <0.01). Elements in serum had a higher accuracy (87.0%) than whole blood (74.0%) in classifying ESCC patients and healthy individuals with discriminant analysis. As, Cd, and Pb concentrations in cancerous tissues were positively correlated with those in normal epithelium (r_s =0.397, 0.571, and 0.542, respectively), while Mn, Cu, and Se accumulated in malignant tissues, with V, Cr, Co, Ni, Sr, and Cd partitioning in normal epithelium (all P <0.05). Thus, certain elements in blood, such as Cu, As, Se, and Sr, were useful in assessing element exposure burdens and accumulation tendency of some elements (Mn, Cu and Se, etc.) was uncovered in tumors. Our investigation demonstrated the variations in trace element distribution for frequently used specimens and further evidence of etiological mechanism is necessary.

The Role of Chosen Essential Elements (Zn, Cu, Se, Fe, Mn) in Food for Special Medical Purposes (FSMPs) Dedicated to Oncology Patients-Critical Review: State-of-the-Art

The scoping review aimed to characterise the role of selected essential elements (Zn, Cu, Se, Fe, Mn) in food for special medical purposes (FSMPs) aimed at oncology patients. The scope review was conducted using Scopus, Google Scholar, and Web of Science to find published references on this subject. Data from the reviewed literature were related to the physiological functions of the element in the body, and the effects of deficiencies and excesses, referring to the latest ESPEN and EFSA guidelines, among others. Important dietary indices/parameters based on the literature review are provided for each element. On the basis of the literature, data on the level of elements in patients with cancer were collected. The content of these elements in 100 mL of FSMPs was read from the manufacturers' declarations. The literature has been provided on the importance of each element in cancer. Our findings show that the essential elements (Zn, Cu, Se, Fe, and Mn) of FSMPs for cancer patients are not adequately treated. We suggest solutions to ensure the safe use of FSMPs in oncology patients.

On the Potential Role of the Antioxidant Couple Vitamin E/Selenium Taken by the Oral Route in Skin and Hair Health

The relationship between oxidative stress and skin aging/disorders is well established. Many topical and oral antioxidants (vitamins C and E, carotenoids, polyphenols) have been proposed to protect the skin against the deleterious effect induced by increased reactive oxygen species production, particularly in the context of sun exposure. In this review, we focused on the combination of vitamin E and selenium taken in supplements since both molecules act in synergy either by non-enzymatic and enzymatic pathways to eliminate skin lipids peroxides, which are strongly implicated in skin and hair disorders.

Long-Term Excessive Selenium Supplementation Affects Gene Expression in Esophageal Tissue of Rats

Esophageal cancer is one of the leading causes of cancer death and the seventh most prevalent cancer worldwide. Considering the positive association of high selenium with the prevalence of esophageal cancer, we have investigated the effect of high doses of selenium on gene expression in the normal esophageal tissue of rats. Twenty male rats were randomly divided into four groups: control group, group 2 mg Se/L, 10 mg Se/L, and 20 mg Se/L rats fed with a basal basic diet and 2, 10, and 20 mg Se/L as sodium selenite in drinking water, respectively, for 20 weeks. Serum malondialdehyde and glutathione peroxidase activity were measured. Moreover, the expression and concentration of the cyclin D1, cyclin E, KRAS, p53, NF-kB, TGF-β, and MGMT in the esophageal tissue were analyzed and compared between the four groups. In normal esophageal tissue, selenium supplementations (2, 10, and 20 mg Se/L) increased the mRNA levels of cyclin D1, P53, KRAS, NF-κB p65, and MGMT and decreased the mRNA level of TGFß1. The concentrations of cyclin D1 and MGMT were also significantly increased by selenium supplementations. Selenium supplementations had no significant effect on serum MDA but significantly increased GPX activity. The present study suggests that selenium supplementation (2, 10, and 20 mg Se/L) affects gene expression related to inflammation, Cell proliferation, and apoptosis in the normal esophageal tissue. However, there were no observed abnormalities other than reduced growth with supplementation of 20 mg/L as Na2SeO3 in rats.

Serum Selenium, Vitamin A, and Vitamin E Levels of Healthy Individuals in High- and Low-Risk Areas of Esophageal Cancer

Background: Esophageal cancer is one of the main causes of cancer mortality in the world. Golestan province, in the northern part of Iran, has the highest esophageal cancer rate in the world. The north and south districts of Golestan province can be classified as low and high-risk areas for esophageal cancer. One of the potential risk factors for esophageal cancer in this population is a nutrient-deficient diet. Dietary antioxidant compounds such as selenium, vitamin E, vitamin A, and β-carotene are reactive oxygen species (ROC) scavengers that play a key role in cellular responses to oxidative stress and preventing DNA damage. This study aims to compare the serum levels of selenium, vitamin E, and vitamin A in healthy individuals in high and low-risk areas of esophageal cancer. Methods: This study is a population of 242 healthy individuals. Serum selenium levels were assessed by atomic absorption spectroscopy. Vitamin E and A were assessed by reversed-phase high-performance liquid chromatography. Results: Vitamin E levels of healthy individuals in high-risk areas were significantly lower than in low-risk areas, while there was no significant difference between the selenium and vitamin A levels of healthy individuals in high-risk areas and low-risk areas. Also, there was no significant difference between selenium, vitamin E, and vitamin A levels in urban and rural areas and men and women in Golestan province. Conclusion: High levels of selenium with lower levels of vitamin E, along with other risk factors, may be associated with esophageal squamous cell carcinoma in high-risk areas of Golestan province.

Trace elements under the spotlight: A powerful nutritional tool in cancer

Cancer is the second leading cause of death worldwide. Research on the relationships between trace elements (TE) and the development of cancer or its prevention is a field that is gaining increasing relevance. This review provides an evaluation of the effects of TE (As, Al, B, Cd, Cr, Cu, F, I, Pb, Li, Mn, Hg, Mo, Ni, Se, Si, Sn, V and Zn) intake and supplementation in cancer risk and prevention, as well as their interactions with oncology treatments. Advancements in the knowledge of TE, their dietary interactions and their main food sources can provide patients with choices that will help them to improve their quality of life and therapy outcomes. This approach could open new opportunities for treatments based on the integration of conventional therapies (chemotherapy, radiotherapy, and immunotherapy) and dietary interventions that provide advanced personalized treatments.

Environmental Selenium and Human Health: an Update

PURPOSE OF REVIEW

Selenium, a trace element, is ubiquitous in the environment. The main source of human exposure is diet. Despite its nutritional benefits, it is one of the most toxic naturally occurring elements. Selenium deficiency and overexposure have been associated with adverse health effects. Its level of toxicity may depend on its chemical form, as inorganic and organic species have distinct biological properties.

RECENT FINDINGS

Nonexperimental and experimental studies have generated insufficient evidence for a role of selenium deficiency in human disease, with the exception of Keshan disease, a cardiomyopathy. Conversely, recent randomized trials have indicated that selenium overexposure is positively associated with type 2 diabetes and high-grade prostate cancer. In addition, a natural experiment has suggested an association between overexposure to inorganic hexavalent selenium and two neurodegenerative diseases, amyotrophic lateral sclerosis and Parkinson's disease. Risk assessments should be revised to incorporate the results of studies demonstrating toxic effects of selenium. Additional observational studies and secondary analyses of completed randomized trials are needed to address the uncertainties regarding the health risks of selenium exposure.

Differential diagnosis of multielements in cancerous and non-cancerous esophageal tissues

It is known that variations in the concentrations of certain elements in humans may be an indication of cancers. In this work, a method for the quantitative analysis of 22 elements in non-tumor and esophageal squamous cell carcinoma (ESCC) tissues from the same individual is reported. Based on the optimized platform combined with multivariate analysis, diagnostic models of ESCC were established using principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), showing excellent classification of cancerous and non-cancerous group by metallomic profiling. Elemental concentrations of 10 elements (Mn, Se, Cu, Ti, Mg, Fe, Co, Zn, Sr, Ca) showed significant difference (p < 0.001) in tumor and non-tumor tissues, in which Mn, Se, Cu and Ti are the top 4 elements of statistical significance and a shift towards higher concentration levels has also been observed in the tumor samples. These results confirm the considerable potential of elemental studies for biomedical purposes. To our knowledge, previous studies on elemental concentration in esophageal cancer were performed in serum or plasma levels; and this is the first study to evaluate the association of tissue elemental concentrations with ESCC.

Cancer incidence following long-term consumption of drinking water with high inorganic selenium content

Selenium, a trace element to which humans are exposed mainly through diet, has been involved in the etiology of human cancer. We investigated the long-term effects of selenium exposure on cancer incidence using data from a natural experiment in Northern Italy. During the 1970s-1980s, in a part of the Italian municipality of Reggio Emilia, residents were inadvertently exposed to unusually high levels of inorganic hexavalent selenium (selenate) through drinking water. We followed the exposed residents for 28years, generating data on incidence (when available) and mortality rates for selected cancer sites; the remaining municipal residents comprised the unexposed (reference) group. We observed no substantial difference in overall cancer incidence comparing exposed and unexposed cohorts. We detected, however, a higher incidence of cancer at some sites, and for a few of them, namely cancers of the buccal cavity and pharynx, melanoma, urinary tract and lymphoid tissue, the excess incidence was particularly evident in the first period of follow-up but decreased over time. Overall, these results suggest that consumption of water with levels of selenium in its inorganic hexavalent form close to the European standard, 10μg/L, may have unfavourable effects on cancer incidence.

A Case-Control Study of the Risk of Cutaneous Melanoma Associated with Three Selenium Exposure Indicators

Aims and background

A direct association between exposure to the metalloid selenium and risk of cutaneous melanoma has been suggested by some observational and experimental cohort studies, whereas other studies have yielded inconsistent results. Since some of the inconsistencies may be due to exposure misclassification arising from the use of exposure indicators that do not adequately reflect body tissue selenium content or the levels of the biologically relevant species of this metalloid, we examined this issue using multiple indicators of exposure.

Methods

We analyzed the relation of selenium exposure with risk of cutaneous melanoma using two different biomarkers, plasma and toenail selenium concentration, and estimated dietary selenium intake in a population-based case-control series (54 cases, 56 controls) from an Italian community.

Results

In unmatched and matched logistic regression models as well as nonparametric generalized additive models, higher plasma selenium levels were strongly associated with excess disease risk. In contrast, toenail and dietary selenium exhibited little relation with melanoma risk. The pattern of correlation among indicators of exposure differed by disease status, with dietary intake associated with plasma selenium levels in patients but not in controls.

Conclusions

Our data showed that different selenium exposure indicators can yield different inferences about melanoma risk. Although the series was small, our results are consistent with a positive association between circulating levels of selenium and melanoma risk. Further investigation of the exposure classification performance of various selenium biomarkers and of metabolic patterns of the metalloid and of its speciation are needed to help elucidate the relation between selenium exposure and human health.

Selenium for preventing cancer

BACKGROUND

This review is the third update of the Cochrane review "Selenium for preventing cancer". Selenium is a naturally occurring element with both nutritional and toxicological properties. Higher selenium exposure and selenium supplements have been suggested to protect against several types of cancer.

OBJECTIVES

To gather and present evidence needed to address two research questions:1. What is the aetiological relationship between selenium exposure and cancer risk in humans?2. Describe the efficacy of selenium supplementation for cancer prevention in humans.

SEARCH METHODS

We updated electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 2), MEDLINE (Ovid, 2013 to January 2017, week 4), and Embase (2013 to 2017, week 6), as well as searches of clinical trial registries.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and longitudinal observational studies that enrolled adult participants.

DATA COLLECTION AND ANALYSIS

We performed random-effects (RE) meta-analyses when two or more RCTs were available for a specific outcome. We conducted RE meta-analyses when five or more observational studies were available for a specific outcome. We assessed risk of bias in RCTs and in observational studies using Cochrane's risk assessment tool and the Newcastle-Ottawa Scale, respectively. We considered in the primary analysis data pooled from RCTs with low risk of bias. We assessed the certainty of evidence by using the GRADE approach.

MAIN RESULTS

We included 83 studies in this updated review: two additional RCTs (10 in total) and a few additional trial reports for previously included studies. RCTs involved 27,232 participants allocated to either selenium supplements or placebo. For analyses of RCTs with low risk of bias, the summary risk ratio (RR) for any cancer incidence was 1.01 (95% confidence interval (CI) 0.93 to 1.10; 3 studies, 19,475 participants; high-certainty evidence). The RR for estimated cancer mortality was 1.02 (95% CI 0.80 to 1.30; 1 study, 17,444 participants). For the most frequently investigated site-specific cancers, investigators provided little evidence of any effect of selenium supplementation. Two RCTs with 19,009 participants indicated that colorectal cancer was unaffected by selenium administration (RR 0.99, 95% CI 0.69 to 1.43), as were non-melanoma skin cancer (RR 1.16, 95% CI 0.30 to 4.42; 2 studies, 2027 participants), lung cancer (RR 1.16, 95% CI 0.89 to 1.50; 2 studies, 19,009 participants), breast cancer (RR 2.04, 95% CI 0.44 to 9.55; 1 study, 802 participants), bladder cancer (RR 1.07, 95% CI 0.76 to 1.52; 2 studies, 19,009 participants), and prostate cancer (RR 1.01, 95% CI 0.90 to 1.14; 4 studies, 18,942 participants). Certainty of the evidence was high for all of these cancer sites, except for breast cancer, which was of moderate certainty owing to imprecision, and non-melanoma skin cancer, which we judged as moderate certainty owing to high heterogeneity. RCTs with low risk of bias suggested increased melanoma risk.Results for most outcomes were similar when we included all RCTs in the meta-analysis, regardless of risk of bias. Selenium supplementation did not reduce overall cancer incidence (RR 0.99, 95% CI 0.86 to 1.14; 5 studies, 21,860 participants) nor mortality (RR 0.81, 95% CI 0.49 to 1.32; 2 studies, 18,698 participants). Summary RRs for site-specific cancers showed limited changes compared with estimates from high-quality studies alone, except for liver cancer, for which results were reversed.In the largest trial, the Selenium and Vitamin E Cancer Trial, selenium supplementation increased risks of alopecia and dermatitis, and for participants with highest background selenium status, supplementation also increased risk of high-grade prostate cancer. RCTs showed a slightly increased risk of type 2 diabetes associated with supplementation. A hypothesis generated by the Nutritional Prevention of Cancer Trial - that individuals with low blood selenium levels could reduce their risk of cancer (particularly prostate cancer) by increasing selenium intake - has not been confirmed. As RCT participants have been overwhelmingly male (88%), we could not assess the potential influence of sex or gender.We included 15 additional observational cohort studies (70 in total; over 2,360,000 participants). We found that lower cancer incidence (summary odds ratio (OR) 0.72, 95% CI 0.55 to 0.93; 7 studies, 76,239 participants) and lower cancer mortality (OR 0.76, 95% CI 0.59 to 0.97; 7 studies, 183,863 participants) were associated with the highest category of selenium exposure compared with the lowest. Cancer incidence was lower in men (OR 0.72, 95% CI 0.46 to 1.14, 4 studies, 29,365 men) than in women (OR 0.90, 95% CI 0.45 to 1.77, 2 studies, 18,244 women). Data show a decrease in risk of site-specific cancers for stomach, colorectal, lung, breast, bladder, and prostate cancers. However, these studies have major weaknesses due to study design, exposure misclassification, and potential unmeasured confounding due to lifestyle or nutritional factors covarying with selenium exposure beyond those taken into account in multi-variable analyses. In addition, no evidence of a dose-response relation between selenium status and cancer risk emerged. Certainty of evidence was very low for each outcome. Some studies suggested that genetic factors might modify the relation between selenium and cancer risk - an issue that merits further investigation.

AUTHORS' CONCLUSIONS

Well-designed and well-conducted RCTs have shown no beneficial effect of selenium supplements in reducing cancer risk (high certainty of evidence). Some RCTs have raised concerns by reporting a higher incidence of high-grade prostate cancer and type 2 diabetes in participants with selenium supplementation. No clear evidence of an influence of baseline participant selenium status on outcomes has emerged in these studies.Observational longitudinal studies have shown an inverse association between selenium exposure and risk of some cancer types, but null and direct relations have also been reported, and no systematic pattern suggesting dose-response relations has emerged. These studies suffer from limitations inherent to the observational design, including exposure misclassification and unmeasured confounding.Overall, there is no evidence to suggest that increasing selenium intake through diet or supplementation prevents cancer in humans. However, more research is needed to assess whether selenium may modify the risk of cancer in individuals with a specific genetic background or nutritional status, and to investigate possible differential effects of various forms of selenium.

Cross sectional study of serum selenium concentration and esophageal squamous dysplasia in western Kenya

Background

Low serum selenium status has been associated with increased risk of esophageal squamous cell carcinoma (ESCC). East Africa is a region of high ESCC incidence and is known to have low soil selenium levels, but this association has not previously been evaluated. In this study we assessed the association of serum selenium concentration and the prevalence of esophageal squamous dysplasia (ESD), the precursor lesion of ESCC, in a cross-sectional study of subjects from Bomet, Kenya.

Methods

294 asymptomatic adult residents of Bomet, Kenya completed questionnaires and underwent endoscopy with Lugol’s iodine staining and biopsy for detection of ESD. Serum selenium concentrations were measured by instrumental neutron activation analysis. Odds ratios (OR) and confidence intervals (95% CI) for associations between serum selenium and ESD were calculated using unconditional logistic regression.

Results

The mean serum selenium concentration was 85.5 (±28.3) μg/L. Forty-two ESD cases were identified (14% of those screened), including 5 (12%) in selenium quartile 1 (Q1), 5 (12%) in Q2, 15 (36%) in Q3, and 17 (40%) in Q4. Higher serum selenium was associated with prevalence of ESD (Q4 vs Q1: OR: 3.03; 95% CI: 1.05–8.74) and this association remained after adjusting for potential confounders (Q4 vs Q1: OR: 3.87; 95% CI: 1.06–14.19).

Conclusion

This is the first study to evaluate the association of serum selenium concentration and esophageal squamous dysplasia in an African population at high risk for ESCC. We found a positive association between higher serum selenium concentration and prevalence of ESD, an association contrary to our original hypothesis. Further work is needed to better understand the role of selenium in the etiology of ESCC in this region, and to develop effective ESCC prevention and control strategies.

The Epidemiology of Selenium and Human Cancer

The relation between selenium and cancer has been one of the most hotly debated topics in human health over the last decades. Early observational studies reported an inverse relation between selenium exposure and cancer risk. Subsequently, randomized controlled trials showed that selenium supplementation does not reduce the risk of cancer and may even increase it for some types, including advanced prostate cancer and skin cancer. An increased risk of diabetes has also been reported. These findings have been consistent in the most methodologically sound trials, suggesting that the early observational studies were misleading. Other studies have investigated selenium compounds as adjuvant therapy for cancer. Though there is currently insufficient evidence regarding the utility and safety of selenium compounds for such treatments, this issue is worthy of further investigation. The study of selenium and cancer is complicated by the existence of a diverse array of organic and inorganic selenium compounds, each with distinct biological properties, and this must be taken into consideration in the interpretation of both observational and experimental human studies.

Antioxidant strategies in respiratory medicine

Pulmonary oxidant stress plays an important pathogenetic role in disease conditions including acute lung injury/adult respiratory distress syndrome (ALI/ARDS), hyperoxia, ischemia-reperfusion, sepsis, radiation injury, lung transplantation, COPD, and inflammation. Reactive oxygen species (ROS), released from activated macrophages and leukocytes or formed in the pulmonary epithelial and endothelial cells, damage the lungs and initiate cascades of pro-inflammatory reactions propagating pulmonary and systemic stress. Diverse molecules including small organic compounds (e.g. gluthatione, tocopherol (vitamin E), flavonoids) serve as natural antioxidants that reduce oxidized cellular components, decompose ROS and detoxify toxic oxidation products. Antioxidant enzymes can either facilitate these antioxidant reactions (e.g. peroxidases using glutathione as a reducing agent) or directly decompose ROS (e.g. superoxide dismutases [SOD] and catalase). Many antioxidant agents are being tested for treatment of pulmonary oxidant stress. The administration of small antioxidants via the oral, intratracheal and vascular routes for the treatment of short- and long-term oxidant stress showed rather modest protective effects in animal and human studies. Intratracheal and intravascular administration of antioxidant enzymes are being currently tested for the treatment of acute oxidant stress. For example, intratracheal administration of recombinant human SOD is protective in premature infants exposed to hyperoxia. However, animal and human studies show that more effective delivery of drugs to cells experiencing oxidant stress is needed to improve protection. Diverse delivery systems for antioxidants including liposomes, chemical modifications (e.g. attachment of masking pegylated [PEG]-groups) and coupling to affinity carriers (e.g. antibodies against cellular adhesion molecules) are being employed and currently tested, mostly in animal and, to a limited extent, in humans, for the treatment of oxidant stress. Further studies are needed, however, in order to develop and establish effective applications of pulmonary antioxidant interventions useful in clinical practice. Although beyond the scope of this review, antioxidant gene therapies may eventually provide a strategy for the management of subacute and chronic pulmonary oxidant stress.

Etiology and Prevention of Esophageal Cancer

BACKGROUND

Esophageal cancer (EC) occurs commonly, especially in Asia, and is the sixth leading cause of cancer deaths worldwide. Recently, great progress has been made in research on the etiology and prevention of EC.

SUMMARY

The major risk factors for esophageal squamous cell carcinoma (ESCC) are tobacco smoking and alcohol drinking, which act synergistically. Dietary parameters, including dietary carcinogens and insufficiency of micronutrients, could also be important risk factors in certain areas. A common etiological factor for both EC and some other cancers are low levels of intake of fruits and vegetables. With improvements in diet and drinking water in developing countries, the incidence of ESCC decreased. However, in economically well-developed countries, the incidence of esophageal adenocarcinoma (EAC) has markedly increased in the past 40 years. The major etiological factor for EAC is gastroesophageal reflux, which is also an etiological factor for gastric cardia adenocarcinoma (GCA). In certain areas of China, the occurrence of GCA is closely related to ESCC. Susceptibility genes for EC are starting to be discovered, and this may help to identify high-risk groups that have more need for preventive measures. Mitigation of the risk factors, early detection and treatment of precancerous lesions are effective approaches for prevention. Smoking cessation, avoidance of excessive alcohol, meat and caloric consumption, increasing physical activity and frequent consumption of vegetables and fruits are prudent lifestyle modifications for the prevention of EC as well as other diseases.

KEY MESSAGE

The etiology of EC includes tobacco smoking, alcohol drinking, low levels of intake of fruits and vegetables as well as gastroesophageal reflux and susceptibility genes.

PRACTICAL IMPLICATIONS

A healthy lifestyle including smoking cessation, increasing physical activity, consumption of vegetables as well as reduction of alcohol intake and caloric consumption are major approaches to the prevention of EC.

Animal Models of Barrett's Esophagus and Esophageal Adenocarcinoma-Past, Present, and Future

Esophageal adenocarcinoma is the fastest rising cancer in the United States. It develops from long-standing gastroesophageal reflux disease which affects >20% of the general population. It carries a very poor prognosis with 5-year survival <20%. The disease is known to sequentially progress from reflux esophagitis to a metaplastic precursor, Barrett's esophagus and then onto dysplasia and esophageal adenocarcinoma. However, only few patients with reflux develop Barrett's esophagus and only a minority of these turn malignant. The reason for this heterogeneity in clinical progression is unknown. To improve patient management, molecular changes which facilitate disease progression must be identified. Animal models can provide a comprehensive functional and anatomic platform for such a study. Rats and mice have been the most widely studied but disease homology with humans has been questioned. No animal model naturally simulates the inflammation to adenocarcinoma progression as in humans, with all models requiring surgical bypass or destruction of existing antireflux mechanisms. Valuable properties of individual models could be utilized to holistically evaluate disease progression. In this review paper, we critically examined the current animal models of Barrett's esophagus, their differences and homologies with human disease and how they have shaped our current understanding of Barrett's carcinogenesis.

From reflux esophagitis to Barrett’s esophagus and esophageal adenocarcinoma

The occurrence of gastroesophageal reflux disease is common in the human population. Almost all cases of esophageal adenocarcinoma are derived from Barrett’s esophagus, which is a complication of esophageal adenocarcinoma precancerous lesions. Chronic exposure of the esophagus to gastroduodenal intestinal fluid is an important determinant factor in the development of Barrett’s esophagus. The replacement of normal squamous epithelium with specific columnar epithelium in the lower esophagus induced by the chronic exposure to gastroduodenal fluid could lead to intestinal metaplasia, which is closely associated with the development of esophageal adenocarcinoma. However, the exact mechanism of injury is not completely understood. Various animal models of the developmental mechanisms of disease, and theoretical and clinical effects of drug treatment have been widely used in research. Recently, animal models employed in studies on gastroesophageal reflux injury have allowed significant progress. The advantage of using animal models lies in the ability to accurately control the experimental conditions for better evaluation of results. In this article, various modeling methods are reviewed, with discussion of the major findings on the developmental mechanism of Barrett’s esophagus, which should help to develop better prevention and treatment strategies for Barrett’s esophagus.

Selenium and Human Health: Witnessing a Copernican Revolution?

In humans, selenium was hypothesized to lower the risk of several chronic diseases, mainly due to the antioxidant activity of selenium-containing proteins. Recent epidemiologic and laboratory studies, however, are changing our perception of the biological effects of this nutritionally essential trace element. We reviewed the most recent epidemiologic and biochemical literature on selenium, synthesizing the findings from these studies into a unifying view. Randomized trials have shown that selenium did not protect against cancer and other chronic diseases, but even increased the risk of specific neoplasms such as advanced prostate cancer and skin cancer, in addition to type 2 diabetes. Biochemical studies indicate that selenium may exert a broad pattern of toxic effects at unexpectedly low concentrations. Furthermore, its upregulation of antioxidant proteins (selenium-dependent and selenium-independent) may be a manifestation of self-induced oxidative stress. In conclusion, toxic effects of selenium species occur at lower concentrations than previously believed. Those effects may include a large range of proteomic changes and adverse health effects in humans. Since the effects of environmental exposure to this element on human health still remain partially unknown, but are potentially serious, the toxicity of selenium exposure should be further investigated and considered as a public health priority.

Oxidative stress: an essential factor in the pathogenesis of gastrointestinal mucosal diseases

Reactive oxygen species (ROS) are generated as by-products of normal cellular metabolic activities. Superoxide dismutase, glutathione peroxidase, and catalase are the enzymes involved in protecting cells from the damaging effects of ROS. ROS are produced in response to ultraviolet radiation, cigarette smoking, alcohol, nonsteroidal anti-inflammatory drugs, ischemia-reperfusion injury, chronic infections, and inflammatory disorders. Disruption of normal cellular homeostasis by redox signaling may result in cardiovascular, neurodegenerative diseases and cancer. ROS are produced within the gastrointestinal (GI) tract, but their roles in pathophysiology and disease pathogenesis have not been well studied. Despite the protective barrier provided by the mucosa, ingested materials and microbial pathogens can induce oxidative injury and GI inflammatory responses involving the epithelium and immune/inflammatory cells. The pathogenesis of various GI diseases including peptic ulcers, gastrointestinal cancers, and inflammatory bowel disease is in part due to oxidative stress. Unraveling the signaling events initiated at the cellular level by oxidative free radicals as well as the physiological responses to such stress is important to better understand disease pathogenesis and to develop new therapies to manage a variety of conditions for which current therapies are not always sufficient.

Selenium for preventing cancer

BACKGROUND

This review is an update of the first Cochrane publication on selenium for preventing cancer (Dennert 2011).Selenium is a metalloid with both nutritional and toxicological properties. Higher selenium exposure and selenium supplements have been suggested to protect against several types of cancers.

OBJECTIVES

Two research questions were addressed in this review: What is the evidence for:1. an aetiological relation between selenium exposure and cancer risk in humans? and2. the efficacy of selenium supplementation for cancer prevention in humans?

SEARCH METHODS

We conducted electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL, 2013, Issue 1), MEDLINE (Ovid, 1966 to February 2013 week 1), EMBASE (1980 to 2013 week 6), CancerLit (February 2004) and CCMed (February 2011). As MEDLINE now includes the journals indexed in CancerLit, no further searches were conducted in this database after 2004.

SELECTION CRITERIA

We included prospective observational studies (cohort studies including sub-cohort controlled studies and nested case-control studies) and randomised controlled trials (RCTs) with healthy adult participants (18 years of age and older).

DATA COLLECTION AND ANALYSIS

For observational studies, we conducted random effects meta-analyses when five or more studies were retrieved for a specific outcome. For RCTs, we performed random effects meta-analyses when two or more studies were available. The risk of bias in observational studies was assessed using forms adapted from the Newcastle-Ottawa Quality Assessment Scale for cohort and case-control studies; the criteria specified in the Cochrane Handbook for Systematic Reviews of Interventions were used to evaluate the risk of bias in RCTs.

MAIN RESULTS

We included 55 prospective observational studies (including more than 1,100,000 participants) and eight RCTs (with a total of 44,743 participants). For the observational studies, we found lower cancer incidence (summary odds ratio (OR) 0.69, 95% confidence interval (CI) 0.53 to 0.91, N = 8) and cancer mortality (OR 0.60, 95% CI 0.39 to 0.93, N = 6) associated with higher selenium exposure. Gender-specific subgroup analysis provided no clear evidence of different effects in men and women (P value 0.47), although cancer incidence was lower in men (OR 0.66, 95% CI 0.42 to 1.05, N = 6) than in women (OR 0.90, 95% CI 0.45 to 1.77, N = 2). The most pronounced decreases in risk of site-specific cancers were seen for stomach, bladder and prostate cancers. However, these findings have limitations due to study design, quality and heterogeneity that complicate interpretation of the summary statistics. Some studies suggested that genetic factors may modify the relation between selenium and cancer risk-a hypothesis that deserves further investigation.In RCTs, we found no clear evidence that selenium supplementation reduced the risk of any cancer (risk ratio (RR) 0.90, 95% CI 0.70 to 1.17, two studies, N = 4765) or cancer-related mortality (RR 0.81, 95% CI 0.49 to 1.32, two studies, N = 18,698), and this finding was confirmed when the analysis was restricted to studies with low risk of bias. The effect on prostate cancer was imprecise (RR 0.90, 95% CI 0.71 to 1.14, four studies, N = 19,110), and when the analysis was limited to trials with low risk of bias, the interventions showed no effect (RR 1.02, 95% CI 0.90 to 1.14, three studies, N = 18,183). The risk of non-melanoma skin cancer was increased (RR 1.44, 95% CI 0.95 to 1.17, three studies, N = 1900). Results of two trials-the Nutritional Prevention of Cancer Trial (NPCT) and the Selenium and Vitamin E Cancer Trial (SELECT)-also raised concerns about possible increased risk of type 2 diabetes, alopecia and dermatitis due to selenium supplements. An early hypothesis generated by NPCT that individuals with the lowest blood selenium levels at baseline could reduce their risk of cancer, particularly of prostate cancer, by increasing selenium intake has not been confirmed by subsequent trials. As the RCT participants were overwhelmingly male (94%), gender differences could not be systematically assessed.

AUTHORS' CONCLUSIONS

Although an inverse association between selenium exposure and the risk of some types of cancer was found in some observational studies, this cannot be taken as evidence of a causal relation, and these results should be interpreted with caution. These studies have many limitations, including issues with assessment of exposure to selenium and to its various chemical forms, heterogeneity, confounding and other biases. Conflicting results including inverse, null and direct associations have been reported for some cancer types.RCTs assessing the effects of selenium supplementation on cancer risk have yielded inconsistent results, although the most recent studies, characterised by a low risk of bias, found no beneficial effect on cancer risk, more specifically on risk of prostate cancer, as well as little evidence of any influence of baseline selenium status. Rather, some trials suggest harmful effects of selenium exposure. To date, no convincing evidence suggests that selenium supplements can prevent cancer in humans.

Prevention of rat breast cancer by genistin and selenium

Breast cancer is the second leading cause of cancer death among women and the third most common cancer. In this study, we investigated the chemoprevention efficacy of each of soy genistin, selenium or a combination of them against breast cancer. Seventy-five female rats were divided into five groups : control group (I); 7,12-dimethylbenz(a)anthracene (DMBA) group (II); DMBA treated with genistin group (III); DMBA treated with selenium group (IV); and DMBA treated with genistin combined with selenium group (V). The treatments were daily administered for 3 months. There were a significant decrease in body weight and serum total antioxidant, while a significant elevation in serum total sialic acid, carcinoembryonic antigen, prolactin, estradiol, nitric oxide, and malondialdhyde of DMBA injected rats compared with control group. Administration of genistin and selenium was associated with decreasing levels of tumorigenicity, endocrine derangement, and oxidative stress. Formation of breast carcinoma in DMBA-induced rats and abnormal changes were ameliorated in the rats treated with genistin/selenium or genistin alone. Supplementation of genistin alone or with selenium provided antioxidant defense with high-potential chemopreventive activity against DMBA-induced mammary tumors more than selenium alone.

Cdx genes, inflammation and the pathogenesis of Barrett's metaplasia

Metaplasia is the conversion of one cell or tissue type to another and can predispose patients to neoplasia. Perhaps one of the best-known examples of metaplasia is Barrett's metaplasia (BM), a pathological condition in which the distal oesophageal epithelium switches from stratified squamous to intestinal-type columnar epithelium. BM predisposes to oesophageal adenocarcinoma and is the consequence of long-term acid bile reflux. The incidence of BM and oesophageal adenocarcinoma has risen dramatically in recent years. A key event in the pathogenesis of BM is the induction of oesophageal CDX2 expression. Importantly, recent data reveal the molecular mechanisms that link inflammation in the development of Barrett's metaplasia, CDX2 and the progression to cancer. This review highlights the relationship between inflammation, metaplasia and carcinogenesis.

Alcohol types and sociodemographic characteristics as risk factors for Barrett's esophagus

BACKGROUND & AIMS

Little is known about the effects of alcohol use and sociodemographics on the risk of Barrett's esophagus, a precursor to esophageal adenocarcinoma. We evaluated the association between alcohol use, alcohol type, sociodemographic profiles, other lifestyle factors, and the risk of Barrett's esophagus.

METHODS

With the use of a case-control study within the Kaiser Permanente Northern California membership, patients with a new diagnosis of Barrett's esophagus (n = 320) diagnosed between 2002 and 2005 were matched to persons with gastroesophageal reflux disease (GERD; n = 316) and to population controls (n = 317). We collected information using validated questionnaires during direct in-person interviews. Analyses used multivariate unconditional logistic regression.

RESULTS

Total alcohol use was not significantly associated with the risk of Barrett's esophagus, although stratification by beverage type showed an inverse association for wine drinkers compared with nondrinkers (>/=7 drinks of wine per week vs none: odds ratio, 0.44; 95% confidence interval, 0.20-0.99; multivariate analysis). Among population controls, those who preferred wine were more likely to have college degrees and regularly take vitamin supplements than those who preferred beer or liquor, although adjustment for these factors or GERD symptoms did not eliminate the inverse association between wine consumption and Barrett's esophagus. Education status was significantly inversely associated with the risk of Barrett's esophagus.

CONCLUSIONS

There are associations between alcohol types, socioeconomic status, and the risk of Barrett's esophagus. Although choice of alcoholic beverages was associated with several factors, multiple adjustments (including for GERD) did not eliminate the association between alcohol and Barrett's esophagus. Further research to evaluate the associations among socioeconomic status, GERD, and Barrett's esophagus is warranted.

Effect of alpha-tocopherol, N-acetylcysteine and omeprazole on esophageal adenocarcinoma formation in a rat surgical model

We previously demonstrated that oxidative stress subsequent to gastroesophageal reflux is an important driving force of esophageal adenocarcinoma (EAC) formation in the esophagogastroduodenal anastomosis (EGDA) rat model. This study investigated the possible tumor inhibitory effects of 2 antioxidants, alpha-tocopherol (389 and 778 ppm), N-acetylcysteine (NAC, 500 and 1,000 ppm), and their combination (389 and 500 ppm, respectively), as well as an antacid therapeutic agent, omeprazole (1,400 ppm). The rats were fed experimental diets 2 weeks after EGDA. All the animals were sacrificed 40 weeks after EGDA and the esophagi were harvested for histopathological examination. alpha-Tocopherol dose-dependently decreased the incidence of EAC (p = 0.03), with 778 ppm alpha-tocopherol reducing the incidence of EAC to 59% (16/27) in comparison with 84% (26/31) in the control group (p = 0.04). Supplementation of alpha-tocopherol also increased the serum concentration of alpha-tocopherol. NAC at 500 and 1,000 ppm did not significantly decrease EAC incidence; however, the combination of alpha-tocopherol 389 ppm and NAC 500 ppm significantly reduced the incidence of EAC to 55% (15/27) (p = 0.02). alpha-Tocopherol alone or in combination with NAC significantly reduced the number of infiltrating cells positively stained for 4-hydroxynonenal. Omeprazole showed only a slight nonsignificant inhibitory effect at the dose given. Our results suggest that supplementation with alpha-tocopherol inhibits the development of EAC in the rat EGDA model and similar inhibitory effect can be achieved when a lower dose of alpha-tocopherol is used in combination with NAC.

Iron intake and body iron stores as risk factors for Barrett's esophagus: a community-based study

OBJECTIVE

High iron stores are a proposed modifiable risk factor for esophageal adenocarcinoma, but minimal human data exist. We evaluated whether iron intake and iron stores were associated with Barrett's esophagus, a metaplastic change that is a strong risk factor for esophageal adenocarcinoma.

METHODS

We conducted a case-control study within the Kaiser Permanente Northern California population. We identified all persons with a new diagnosis of Barrett's esophagus (cases); they were matched to persons with GERD (without Barrett's esophagus) and to population controls. Subjects completed examinations, dietary questionnaires, and testing for serum iron stores (ferritin and transferrin saturation). Analyses used unconditional logistic regression.

RESULTS

We evaluated 319 cases, 312 GERD patients, and 313 population controls. Compared with population controls, Barrett's esophagus patients had lower dietary iron intakes (4th vs 1st quartiles, odds ratio [OR]= 0.37, 95% confidence interval [CI] 0.17-0.80), similar total iron intakes (including supplement use), and lower iron stores (4th vs 1st quartiles, ferritin OR = 0.24, 95% CI 0.14-0.40;% transferrin saturation OR = 0.66, 95% CI 0.41-1.04; P value trend <0.01 and 0.03, respectively). Similar associations were observed in comparisons with GERD controls and among subjects without clear sources of blood loss on endoscopy.

CONCLUSIONS

Patients with Barrett's esophagus had lower dietary iron intakes and lower serum iron stores than controls in our population. These findings do not provide support for the current hypothesis that high iron stores or a high iron intake are risk factors for Barrett's esophagus, a potential early event in the carcinogenic sequence for esophageal adenocarcinoma.

Dietary antioxidants, fruits, and vegetables and the risk of Barrett's esophagus

OBJECTIVE

The present study evaluated the associations among antioxidants, fruit and vegetable intake, and the risk of Barrett's esophagus (BE), a potential precursor to esophageal adenocarcinoma.

METHODS

We conducted a case-control study within the Kaiser Permanente Northern California population. Incident BE cases (N = 296) were matched to persons with gastroesophageal reflux disease (GERD) (GERD controls N = 308) and to population controls (N = 309). Nutrient intake was measured using a validated 110-item food frequency questionnaire. The antioxidant results were stratified by dietary versus total intake of antioxidants.

RESULTS

Comparing cases to population controls, dietary intake of vitamin C and beta-carotene were inversely associated with the risk of BE (4th vs 1st quartile, adjusted odds ratio [OR] 0.48, 95% confidence interval [CI] 0.26-0.90; OR 0.56, 95% CI 0.32-0.99, respectively), and the inverse association was strongest for vitamin E (OR 0.25, 95% CI 0.11-0.59). The inverse trends for antioxidant index (total and dietary) and fruit and vegetable intake were statistically significant, while most total intakes were not associated with reduced risk. The use of antioxidant supplements did not influence the risk of BE, and antioxidants and fruits and vegetables were inversely associated with a GERD diagnosis.

CONCLUSION

Dietary antioxidants, fruits, and vegetables are inversely associated with the risk of BE, while no association was observed for supplement intake. Our results suggest that fruits and vegetables themselves or associated undetected confounders may influence early events in the carcinogenesis of esophageal adenocarcinoma.

Neither Antioxidants nor COX-2 Inhibition Protect Against Esophageal Inflammation in an Experimental Model of Severe Reflux

BACKGROUND

Reflux-induced injury and oxidative stress result in esophageal inflammation and the potential for progression to intestinal metaplasia and adenocarcinoma. Proton-pump inhibitors represent the standard medical approach, but anti-inflammatories and antioxidants offer novel therapeutic possibilities.

MATERIALS AND METHODS

Six weeks after an esophagojejunostomy reflux procedure, female Wistar rats (n = 100) were randomized to receive either an antioxidant (vitamin C, 8 mg or 28 mg/day), a cyclooxygenase-2 (COX-2) inhibitor (rofecoxib, 1 mg/day), or no therapy. After sacrifice 16 weeks later, esophageal injury was scored using pathologic and image analysis scoring.

RESULTS

Esophagitis was present in all 63 animals completing the study and was severe in 27 (43%). No animal developed metaplasia or tumor. The extent of inflammation and esophageal ulceration were not significantly different between experimental groups.

CONCLUSIONS

In this model of reflux injury, antioxidants and COX-2 inhibitors failed to ameliorate the severe inflammation induced. Further experimental designs should evaluate these novel approaches in less severe experimental models.

Neither Antioxidants nor COX-2 Inhibition Protect Against Esophageal Inflammation in an Experimental Model of Severe Reflux

BACKGROUND

Reflux-induced injury and oxidative stress result in esophageal inflammation and the potential for progression to intestinal metaplasia and adenocarcinoma. Proton-pump inhibitors represent the standard medical approach, but anti-inflammatories and antioxidants offer novel therapeutic possibilities.

MATERIALS AND METHODS

Six weeks after an esophagojejunostomy reflux procedure, female Wistar rats (n = 100) were randomized to receive either an antioxidant (vitamin C, 8 mg or 28 mg/day), a cyclooxygenase-2 (COX-2) inhibitor (rofecoxib, 1 mg/day), or no therapy. After sacrifice 16 weeks later, esophageal injury was scored using pathologic and image analysis scoring.

RESULTS

Esophagitis was present in all 63 animals completing the study and severe in 27 (43%). No animal developed metaplasia or tumor. The extent of inflammation and esophageal ulceration were not significantly different between experimental groups.

CONCLUSIONS

In this model of reflux injury, antioxidants and COX-2 inhibitors failed to ameliorate the severe inflammation induced. Further experimental designs should evaluate these novel approaches in less severe experimental models.

Systematic review: the application of molecular pathogenesis to prevention and treatment of oesophageal adenocarcinoma

BACKGROUND

Oesophageal adenocarcinoma is an increasingly common cancer with a poor prognosis. It develops in a stepwise progression from Barrett's metaplasia to dysplasia, and then adenocarcinoma followed by metastasis.

AIM

To outline the key molecular changes in oesophageal adenocarcinoma and to summarize the chemopreventative and therapeutic strategies proposed.

METHODS

A literature search was performed to identify appropriate research papers in the field. Search terms included: Barrett's (o)esophagus, intestinal metaplasia, (o)esophageal adenocarcinoma, molecular changes, genetic changes, pathogenesis, chemoprevention, therapeutic strategies and treatment. The search was restricted to English language articles.

RESULTS

A large number of molecular changes have been identified in the progression from Barrett's oesophagus to oesophageal adenocarcinoma although there does not appear to be an obligate order of events. Potential chemoprevention strategies include acid suppression, anti-inflammatory agents and antioxidants. In established adenocarcinoma, targeted treatments under evaluation include receptor tyrosine kinase inhibitors of EGFR and cyclin-dependent kinase inhibitors, which may benefit a subgroup of patients.

CONCLUSIONS

Advances in molecular methodology have led to a greater understanding of the oesophageal adenocarcinoma pathways, which provides opportunities for chemoprevention and therapeutic strategies with a mechanistic basis. More work is required to assess both the safety and efficacy of these new treatments.

Alterations in manganese superoxide dismutase expression in the progression from reflux esophagitis to esophageal adenocarcinoma

BACKGROUND

Comprehensive understanding of the basic mechanisms in the progression of esophagitis, Barrett esophagus (BE), and esophageal adenocarcinoma (EAC) is urgently needed to develop a management strategy for an effective screening of BE and management of EAC. The aim of this study is to provide a detailed insight of the histology and the cellular and molecular events associated with the genesis of BE and EAC under the esophagoduodenal reflux conditions.

METHODS

Esophagoduodenal anastomosis (EDA) was performed on rats. Animals were weighed weekly and killed after 1, 2, 3, 4, 5, and 6 months. The entire esophagi were examined for macroscopic and microscopic changes and for manganese superoxide dismutase (MnSOD) expression, and TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) assay was performed.

RESULTS

Morphological transformation from esophagitis (100% of animals) to BE (66% of animals) to EAC was observed after 3 months. There was marked loss of MnSOD expression in animals with esophagitis and BE at 1 and 2 months, with an increase in expression during the transformation to dysplasia and EAC. Increased proliferation and apoptosis was observed and reached a peak at months 1 and 2. Greatly increased levels of 8-hydroxy-deoxyguanosine was found during the progression to EAC.

CONCLUSIONS

The morphological transformation of the esophageal mucosa is an adaptive process, and it is an important foundation for the transdifferentiation of BE and cancer. The significant loss of MnSOD expression to achieve BE and then the adaptive increase in expression to achieve dysplasia and EAC during this transformation may represent a predictive marker in identifying patients who will progress from BE to EAC.

Traditional home-brewed beer consumption and iron status in patients with esophageal cancer and healthy control subjects from Transkei, South Africa

Consumption of home-brewed beer is associated with dietary iron excess and a high incidence of esophageal cancer in Transkei, South Africa. We examined the relationship between home-brewed beer consumption and body iron status in 234 patients with esophageal squamous cell carcinoma and 595 control subjects residing in Transkei. Subjects were screened for iron overload using transferrin saturation >45%, and/or serum ferritin >200 microg/l for women and >300 microg/l for men. A questionnaire was administered to all subjects, and iron content of randomly selected home-brewed beer samples was determined. The iron content of home-brewed beer was 258-fold higher than the commercial Castle Lager beer produced by South African Breweries. The prevalence of home-brewed beer consumption was 30.1% in esophageal cancer patients and 15.5% in control subjects and was found not to be a risk factor for esophageal cancer after adjustment for age, sex, and tobacco consumption (male subjects, odds ratio= 1.6 (95% confidence interval [CI]: 0.7-4.5); female subjects, odds ratio=1.7 (95% CI: 0.7-4.5). Iron overload as determined by transferrin saturation and elevated serum ferritin was observed in 4.3% of patients with esophageal cancer and 0.7% of control subjects and was not associated with the consumption of home-brewed beer. Consumption of home-brewed beer is not a risk factor for esophageal cancer and is not linked with iron overload in either cancer patients or control subjects; however, iron overload is likely to result from a combination of dietary intake and a genetic component.

Dietary mineral and trace element intake and squamous cell carcinoma of the esophagus in a Chinese population

Few studies have been conducted in low-selenium areas of China to assess the relationships between dietary intake of selenium and zinc and the risk of squamous cell carcinoma of the esophagus (SCCE). We studied dietary mineral and trace element intake and risk of SCCE in a population- based, case-control study in Taixing, China, in 2000. A total of 218 SCCE patients and 415 population healthy controls were interviewed using a standard dietary and health questionnaire. The median and quartiles were calculated to represent the average level and distribution of selected dietary minerals and trace elements estimated by the Chinese Standard Tables of Food Composition. The adjusted odds ratios (ORs) comparing the highest with the lowest quartiles were 0.30 (95% confidence intervals, CIs = 0.13-0.67) for selenium intake and 0.28 (95% CI = 0.11-0.70) for zinc intake with obvious dose-dependent patterns (P values for trend = 0.01). The adjusted OR for the combined effect of selenium and zinc intake was 0.53 (95% CI = 0.29-0.96) after controlling for potential confounding factors, including age, gender, educational level, body mass index, and total energy intake. Our results suggested that the potential joint effect of zinc and selenium might contribute to SCCE risk. Increased dietary intake of selenium and zinc may decrease the risk of SCCE in a low-selenium area of China.

Selenium regulates cyclooxygenase-2 and extracellular signal-regulated kinase signaling pathways by activating AMP-activated protein kinase in colon cancer cells

Epidemiologic and experimental evidences indicate that selenium, an essential trace element, can reduce the risk of a variety of cancers. Protection against certain types of cancers, particularly colorectal cancers, is closely associated with pathways involving cyclooxygenase-2 (COX-2). We found that AMP-activated protein kinase (AMPK), which functions as a cellular energy sensor, mediates critical anticancer effects of selenium via a COX-2/prostaglandin E(2) signaling pathway. Selenium activated AMPK in tumor xenografts as well as in colon cancer cell lines, and this activation seemed to be essential to the decrease in COX-2 expressions. Transduction with dominant-negative AMPK into colon cancer cells or application of cox-2(-/-)-negative cells supported the evidence that AMPK is an upstream signal of COX-2 and inhibits cell proliferation. In HT-29 colon cancer cells, carcinogenic agent 12-O-tetradecanoylphorbol-13-acetate (TPA) activated extracellular signal-regulated kinase (ERK) that led to COX-2 expression and selenium blocked the TPA-induced ERK and COX-2 activation via AMPK. We also showed the role of a reactive oxygen species as an AMPK activation signal in selenium-treated cells. We propose that AMPK is a novel and critical regulatory component in selenium-induced cancer cell death, further implying AMPK as a prime target of tumorigenesis.

A novel external esophageal perfusion model for reflux esophageal injury

The current animal models of esophagitis and Barrett's esophagus consist of surgeries that divert the gastroduodenal contents to the esophagus. The limitations of these models are the inability to control the amount and concentration of the refluxate and the causing of significant postoperative stress and morbidity. Eighteen adult rats were cannulated at the upper esophagus and connected to a subcutaneous osmotic micropump to perfuse the esophageal lumen with bile and acid. Animals were sacrificed after 7 days of perfusion. Histological changes were determined. Cell proliferation, apoptosis, lipid peroxidation, and glutathione were measured. Histopathological changes in the bile- or acid-perfused esophagus were consistent with the findings associated with reflux esophagitis. Enhanced proliferation and apoptosis were seen, along with increased oxidative stress. The external esophageal perfusion model enabled precise control of the injurious agent. It induced the histologic and cellular injury of reflux esophagitis after 7 days.

Dietary Selenium Intake and Genetic Polymorphisms of the GSTP1 and p53 Genes on the Risk of Esophageal Squamous Cell Carcinoma

Few studies have assessed potential effect modifications by polymorphisms of susceptibility genes on the association between selenium intake and esophageal squamous cell carcinoma (ESCC). We studied the joint effects of dietary selenium and the GSTP1 and p53 polymorphisms on ESCC risk in a population-based case-control study with 218 ESCC cases and 415 controls in Taixing City, China. Dietary selenium intake was estimated from a food frequency questionnaire with 97 food items. GSTP1 and p53 polymorphisms were detected by RFLP-PCR assays. Logistic regression analyses were done to estimate odds ratios (OR) and 95% confidence intervals (95% CI). Reduced ESCC risk was observed among individuals in the highest quartile of dietary selenium intake (adjusted OR, 0.31; 95% CI, 0.13-0.70) with a dose-dependent gradient (P(trend) = 0.01). The p53 Pro/Pro genotype was associated with increased risk of ESCC compared with the Arg/Arg genotype (adjusted OR, 2.02; 95% CI, 1.19-3.42). When combined with selenium consumption, an obvious increased risk was observed among individuals with the p53 Pro/Pro or GSTP1 Ile/Ile genotype with adjusted ORs of 3.19 (95% CI, 1.74-5.84) and 1.90 (95% CI, 1.03-3.51), respectively. Among smokers and alcohol drinkers, elevation of ESCC risk was more prominent among p53 Pro/Pro individuals who consumed a low level of dietary selenium (adjusted OR, 3.59; 95% CI, 1.49-8.66 for smokers and 6.19; 95% CI, 1.83-20.9 for drinkers). Our study suggests that the effect of dietary selenium on the risk of ESCC may be modulated by tobacco smoking, alcohol drinking, and p53 Pro/Pro and GSTP1 Ile/Ile genotypes.

Systematic review: the chemoprevention of oesophageal adenocarcinoma

The incidence of oesophageal adenocarcinoma is increasing in the UK faster than any other malignancy. Despite its relatively poor prognosis and the limited success of existing treatments, there is enthusiasm that chemopreventive agents might be able to stem the transition from normal squamous epithelium to adenocarcinoma. We discuss gastro-oesophageal reflux as the main risk factor for the development of Barrett's metaplasia, the only known precursor of oesophageal adenocarcinoma. Treatment options for reflux disease are considered with regard to their effects on cancer risk. Recent advances in the molecular and cell biology of Barrett's are outlined, and potential targets for chemoprevention examined. Available treatments for reflux disease have not convincingly altered the likelihood of cancer development. Epidemiological and animal studies support the use of non-steroidal anti-inflammatory drugs as potential chemopreventive agents. Dietary agents, however, have a more favourable side-effect profile and may prove to be an attractive alternative, although more work is needed to fully explore this prospect.

Effect of dietary selenite on N-nitrosodiethylamine-induced and phenobarbital promoted multistage hepatocarcinogenesis in rat: reflection in some minerals

Selenium (Se), a dietary micronutrient, plays a vital role in cancer chemotherapy in many organs including the liver. We have studied the relationship between some minerals, which are essential in normal functioning of cells and anticancer effect of Se in N-nitrosodiethylamine (DEN) induced and phenobarbital (PB) promoted multistage hepatocarcinogenesis. Se (4 ppm through drinking water; as sodium selenite) was given to animals throughout the study, before initiation and during promotion phase of hepatocarcinogenesis, in a defined experimental protocol. Se, sodium, potassium, calcium and iron were measured either in hepatoma, or surrounding liver tissue or whole liver tissue and serum of experimental animals. DEN and PB treatment significantly (P < 0.001) increased potassium, calcium and iron levels in serum, while it decreased (P < 0.001) the Se and sodium levels when compared with control rats. We have also observed significantly increased (P < 0.001) sodium, calcium and iron levels in hepatoma and surrounding liver tissue, whereas, Se, and potassium level was found to be decreased (P < 0.001) when compared with control rats. Supplementation of selenite throughout the study, before initiation and during promotion stage significantly alters the above mineral content. Results showed that the most significant beneficial effect of selenium during hepatocarcinogenesis was exerted potentially in long-term continuous and/or before the initiation phase of carcinogenicity, rather than in the promotion phase. The present and previous results from our laboratory suggest that sub-optimal intake of a single trace mineral can have broad effects on chemotherapy, providing a framework for understanding the multiple beneficial effects of selenium in cancer chemoprevention.

Effects of 1,4-phenylenebis(methylene)selenocyanate (p-XSC) and vitamin E on 4-nitroquinoline-N-oxide (4-NQO)-induced mutagenesis in lacZ mouse upper aerodigestive tissue

The effects of dietary administration of 1,4-phenylenebis(methylene)selenocyanate (p-XSC) and Vitamin E on 4-nitroquinoline-N-oxide (4-NQO)-induced mutagenesis in lacZ mouse upper aerodigestive tissues were investigated. 4-NQO was a potent mutagen in tongue, other pooled oral tissues and esophagus when given in drinking water for 4 weeks at a concentration of 20 microg/ml [corrected]. The mutant fractions (MFs) in these tissues were: 144+/-73, 130+/-52 and 61+/-24 mutants/10(5), respectively. Background levels were 3.7+/-1.9 in tongue, 2.9+/-1.2 in esophagus and 2.4+/-1.0 in pooled oral tissue. Vitamin E at levels of 200 and 400 IU/kg diet led to no significant effects on mutagenesis although a small decrease in the MF was observed in all tissues at the higher dose. Dietary p-XSC at levels of 2.5 and 10 ppm selenium also resulted in no statistically significant effects on mutagenesis, but mutagenesis was somewhat reduced in esophagus and pooled oral tissue at the higher dose. However, the combination of the low doses of p-XSC and Vitamin E resulted in nearly a 40% decrease in mutagenesis in tongue and esophagus, and this decrease was statistically significant (P=0.008 and 0.023, respectively. No inhibition was observed using a combination of the higher doses of p-XSC and Vitamin E. These results lend support to the use of low doses of inhibitors of mutagenesis in combinations. The application of in vivo mutagenesis assays to the screening of chemopreventive agents enables investigators to evaluate potential inhibitors when given individually and in combinations on the initiation stage of carcinogenesis in a short-term in vivo bioassay.

Perinatal selenium exposure decreases spontaneous liver tumorogenesis in CBA mice

This study was designed to investigate the influence of neonatal selenium (an anticarcinogenic agent) exposure on spontaneous liver tumor formation in adult mice. Pregnant CBA mice were administered selenium during the last week of pregnancy and for ten days following parturition. Selenium significantly reduced the incidence of spontaneous hepatomas in adult male progeny, while having no effect on the lower hepatoma incidence in adult females. The data indicate that neonatal selenium alters hepatoma incidence in a sex-dependent manner. This study represents the model of neonatal cancer prevention.