Dietary zinc deficiency enhances esophageal cell proliferation and N-nitrosomethylbenzylamine (NMBA)-induced esophageal tumor incidence in C57BL/6 mouse

Zinc deficiency drives ferroptosis resistance by lactate production in esophageal squamous cell carcinoma

Trace metal zinc is involved in key processes of solid tumors by its antioxidant properties, while the role of zinc at the onset of esophageal squamous cell carcinoma (ESCC) remains controversial. This study aimed to determine whether zinc is associated with the ESCC and underlying molecular events involving malignant progression. Based on a case-control study, we found serum and urine zinc were decreased and correlated with ESCC progression. Thus, an in vitro model for zinc deficiency (ZD) was established, and we found that ZD contributed to the proliferation, migration, and invasion of EC109 cells. Untargeted metabolomics identified 59 upregulated metabolites and 6 downregulated metabolites, among which glycolysis and ferroptosis-related oxidation of chain fatty acids might play crucial steps in ZD-treated molecular events. Interestingly, ZD disrupted redox homeostasis and enhanced cytosolic Fe2+ of EC109 cells, while lipid peroxidation, the key marker of ferroptosis occurrence, was decreased after ZD treatment. The mechanism underlying these changes may involve ZD-enhanced ESCC glycolysis and lactate production, which confer ferroptosis resistance by inhibiting of p-AMPK and leading to the upregulation of SREBP1 and SCD1 to enhance the production of anti-ferroptosis monounsaturated fatty acids.

Cellular zinc metabolism and zinc signaling: from biological functions to diseases and therapeutic targets

Zinc metabolism at the cellular level is critical for many biological processes in the body. A key observation is the disruption of cellular homeostasis, often coinciding with disease progression. As an essential factor in maintaining cellular equilibrium, cellular zinc has been increasingly spotlighted in the context of disease development. Extensive research suggests zinc's involvement in promoting malignancy and invasion in cancer cells, despite its low tissue concentration. This has led to a growing body of literature investigating zinc's cellular metabolism, particularly the functions of zinc transporters and storage mechanisms during cancer progression. Zinc transportation is under the control of two major transporter families: SLC30 (ZnT) for the excretion of zinc and SLC39 (ZIP) for the zinc intake. Additionally, the storage of this essential element is predominantly mediated by metallothioneins (MTs). This review consolidates knowledge on the critical functions of cellular zinc signaling and underscores potential molecular pathways linking zinc metabolism to disease progression, with a special focus on cancer. We also compile a summary of clinical trials involving zinc ions. Given the main localization of zinc transporters at the cell membrane, the potential for targeted therapies, including small molecules and monoclonal antibodies, offers promising avenues for future exploration.

Climate Change and the Esophagus: Speculations on Changing Disease Patterns as the World Warms

PURPOSE OF REVIEW

Esophageal disorders, including gastroesophageal reflux disease (GERD), eosinophilic esophagitis (EoE), and esophageal cancer, may be affected by climate change. Our review describes the impact of climate change on risk factors associated with esophageal diseases and speculates how these climate-related factors impacted esophageal disorders and their management.

RECENT FINDINGS

Climate change is responsible for extreme weather conditions (shifts in rainfall, floods, droughts, and forest fires) and global warming. These consequences affect basic human needs of water and food, causing changes in population dynamics and pose significant threats to digestive health, including common esophageal disorders like GERD, EoE, and esophageal cancers. The changing patterns of esophageal diseases with climate change are likely mediated through risk factors, including nutrition, pollutants, microplastics, and the microbiota-gut-brain axis. The healthcare process itself, including GI endoscopy practices commonly employed in diagnosing and therapeutics of esophageal diseases, may, in turn, contribute to climate change through plastic wastage and greenhouse gas emissions, thus creating the climate change lifecycle. Breaking the cycle would involve changes at the individual level, community level, and national policy level. Prevention is key, with individuals identifying and remediating risk factors and reducing carbon footprints. The ABC (Advocacy, Broadcast, and Collaborate) activities would help enhance awareness at the community level. Higher-level programs such as the Bracing Resilience Against Climate Effects (BRACE) would lead to broader and larger-scale adoption of public health adaptation strategies at the national level. The impact of climate change on esophageal disorders is likely real, mediated by several risk factors, and creates a climate change lifecycle that may only break if changes are made at individual, community, and national levels.

Effects of dietary zinc deficiency on esophageal squamous cell proliferation and the mechanisms involved

BACKGROUND

Dietary zinc deficiency has been shown to be associated with the development of esophageal cancer in humans, but the exact mechanism of action is not known

AIM

To observe the effects of dietary zinc deficiency on esophageal squamous cell proliferation.

METHODS

Thirty C57BL/6 mice were randomly divided into three groups: A zinc-sufficient (ZS) group, zinc-deficient (ZD) group, and zinc-replenished (ZR) group. For weeks 1–10, zinc levels in the mice diets were 30.66–30.89 mg/kg in the ZS group and 0.66–0.89 mg/kg in the ZD and ZR groups. During weeks 10–12, the ZR group was switched to the ZS diet; the other two groups had no changes in their diets. Changes in body weight, serum, and esophageal tissue zinc concentrations were assessed as well as differences in the expression of proliferating cell nuclear antigen (PCNA), mitogen-activated protein kinase p38 (p38MAPK), nuclear factor kappa B (NF-κB) p105, NF-κB p65, and cyclooxygenase (COX)-2 proteins in the esophageal mucosa.

RESULTS

The body weight and zinc concentration in the serum and esophageal mucosa were significantly lower in the ZD and ZR groups than in the ZS group (P < 0.05). In ZD mice, there was a marked proliferation of basal cells in the esophageal mucosa, resulting in a disturbance in the arrangement of basal cells in layers 2–4, a thickening of the squamous layer, and a significant increase in the expression of the above-mentioned five proteins involved in proliferation and inflammation in the esophageal mucosa. Two weeks after switching to the ZS diet, the serum zinc concentration in the ZR group increased, and the expression of PCNA, NF-κB p105, and COX-2 decreased, but the concentration of zinc in the esophageal mucosa and the structure of the esophageal mucosa did not display any significant changes

CONCLUSION

The ZD diet decreased the growth rate and promoted the proliferation of esophageal squamous cells in mice. The mechanism of proliferation was related to the induced overexpression of COX-2, P38, PCNA, and NF-κB (p105 and p65), and the ZR diet reduced the expression of PCNA, NF-κB p105, and COX-2, thereby reversing this process.

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Tocopherols inhibit esophageal carcinogenesis through attenuating NF-κB activation and CXCR3-mediated inflammation

Esophageal cancer is one of the common causes of cancer mortality in the world. The predominant histological subtype, esophageal squamous cell carcinoma (ESCC), often results in poor prognosis due to the lack of effective approaches for the early diagnosis and treatment, highlighting the need for preventive intervention against this disease. Here we report that dietary tocopherols significantly prevents esophageal carcinogenesis by inhibiting the activation of NF-κB and the subsequent interaction of chemokine CXCL9/10/11 with their receptor CXCR3 in ESCC induced by N-nitrosomethylbenzylamine (NMBA) in murine models. Dietary supplementation with 0.15% α-tocopherol (α-T), δ-tocopherol (δ-T), or γ-tocopherol rich mixture (γ-TmT) markedly suppressed the production of pro-inflammatory cytokines, as well as the induction of CXCR3+ effector T cells (CD4+ Th1 and CD8+ CTLs) infiltration, especially at the early stage of carcinogenesis. In experiments in vivo and in vitro, these events were tightly correlated with the blockade of NF-κB activation. Our results show that tocopherols decrease carcinogenesis through inhibiting NF-κB and CXCR3 signaling, as well as related inflammation in early premalignant lesions. This pathway may offer a novel target for chemoprevention of esophageal cancer.

Selective inhibitory effects of zinc on cell proliferation in esophageal squamous cell carcinoma through Orai1

Zinc, an essential micronutrient, has a cancer preventive role. Zinc deficiency has been shown to contribute to the progression of esophageal cancer. Orai1, a store-operated Ca²⁺ entry (SOCE) channel, was previously reported to be highly expressed in tumor tissues removed from patients with esophageal squamous cell carcinoma (ESCC) with poor prognosis, and elevation of its expression contributes to both hyperactive intracellular Ca²⁺ oscillations and fast cell proliferation in human ESCC cells. However, the molecular basis of cancer preventive functions of zinc and its association with Orai1-mediated cell proliferation remains unknown. The present study shows that zinc supplementation significantly inhibits proliferation of ESCC cell lines and that the effect of zinc is reversible with N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine, a specific Zn²⁺ chelator, whereas nontumorigenic esophageal epithelial cells are significantly less sensitive to zinc treatment. Fluorescence live cell imaging revealed that extracellular Zn²⁺ exerted rapid inhibitory effects on Orai1-mediated SOCE and on intracellular Ca²⁺ oscillations in the ESCC cells. Knockdown of Orai1 or expression of Orai1 mutants with compromised zinc binding significantly diminished sensitivity of the cancer cells to zinc treatment in both SOCE and cell proliferation analyses. These data suggest that zinc may inhibit cell proliferation of esophageal cancer cells through Orai1-mediated intracellular Ca²⁺ oscillations and reveal a possible molecular basis for zinc-induced cancer prevention and Orai1-SOCE signaling pathway in cancer cells.-Choi, S., Cui, C., Luo, Y., Kim, S.-H., Ko, J.-K., Huo, X., Ma, J., Fu, L.-W., Souza, R. F., Korichneva, I., Pan, Z. Selective inhibitory effects of zinc on cell proliferation in esophageal squamous cell carcinoma through Orai1.

Zinc transporters and dysregulated channels in cancers

As a nutritionally essential metal ion, zinc (Zn) not only constitutes a structural element for more than 3000 proteins but also plays important regulatory functions in cellular signal transduction. Zn homeostasis is tightly controlled by regulating the flux of Zn across cell membranes through specific transporters, i.e. ZnT and ZIP family proteins. Zn deficiency and malfunction of Zn transporters have been associated with many chronic diseases including cancer. However, the mechanisms underlying Zn regulatory functions in cellular signaling and their impact on the pathogenesis and progression of cancers remain largely unknown. In addition to these acknowledged multifunctions, Zn modulates a wide range of ion channels that in turn may also play an important role in cancer biology. The goal of this review is to propose how zinc deficiency, through modified Zn homeostasis, transporter activity and the putative regulatory function of Zn can influence ion channel activity, and thereby contribute to carcinogenesis and tumorigenesis. This review intends to stimulate interest in, and support for research into the understanding of Zn-modulated channels in cancers, and to search for novel biomarkers facilitating effective clinical stratification of high risk cancer patients as well as improved prevention and therapy in this emerging field.

Africa's Oesophageal Cancer Corridor: Geographic Variations in Incidence Correlate with Certain Micronutrient Deficiencies

BACKGROUND

The aetiology of Africa's easterly-lying corridor of squamous cell oesophageal cancer is poorly understood. Micronutrient deficiencies have been implicated in this cancer in other areas of the world, but their role in Africa is unclear. Without prospective cohorts, timely insights can instead be gained through ecological studies.

METHODS

Across Africa we assessed associations between a country's oesophageal cancer incidence rate and food balance sheet-derived estimates of mean national dietary supplies of 7 nutrients: calcium (Ca), copper (Cu), iron (Fe), iodine (I), magnesium (Mg), selenium (Se) and zinc (Zn). We included 32 countries which had estimates of dietary nutrient supplies and of better-quality GLOBCAN 2012 cancer incidence rates. Bayesian hierarchical Poisson lognormal models were used to estimate incidence rate ratios for oesophageal cancer associated with each nutrient, adjusted for age, gender, energy intake, phytate, smoking and alcohol consumption, as well as their 95% posterior credible intervals (CI). Adult dietary deficiencies were quantified using an estimated average requirements (EAR) cut-point approach.

RESULTS

Adjusted incidence rate ratios for oesophageal cancer associated with a doubling of mean nutrient supply were: for Fe 0.49 (95% CI: 0.29-0.82); Mg 0.58 (0.31-1.08); Se 0.40 (0.18-0.90); and Zn 0.29 (0.11-0.74). There were no associations with Ca, Cu and I. Mean national nutrient supplies exceeded adult EARs for Mg and Fe in most countries. For Se, mean supplies were less than EARs (both sexes) in 7 of the 10 highest oesophageal cancer ranking countries, compared to 23% of remaining countries. For Zn, mean supplies were less than the male EARs in 8 of these 10 highest ranking countries compared to in 36% of other countries.

CONCLUSIONS

Ecological associations are consistent with the potential role of Se and/or Zn deficiencies in squamous cell oesophageal cancer in Africa. Individual-level analytical studies are needed to elucidate their causal role in this setting.

Knockdown of zinc transporter ZIP5 (SLC39A5) expression significantly inhibits human esophageal cancer progression

ZIP5 is a central player in mammalian zinc metabolism. Studies suggest that ZIP5 is differentially expressed during esophageal tumorigenesis, yet the role of ZIP5 in esophageal cancer cells has not yet been clarified. Immunohistochemistry, western blotting and qRT-PCR techniques were used to detect ZIP5 expression in esophageal squamous cell carcinoma (ESCC) tissues. We established a stable knockdown ZIP5 cell line (KYSE170K) derived from the ESCC cell line KYSE170. We conducted MTT and CCK-8 assays to determine the role of ZIP5 in cell proliferation, Transwell assays to detect migration and invasion, and flow cytometry (FCM) to detect apoptosis and cell cycle percentage using KYSE170K cells. We conducted a gene profiling study to detect the expression of genes related to tumor progression. The results demonstrated that ZIP5 protein and mRNA expression was highest in ESCC, intermediate in para-carcinoma and lowest in normal tissue. ZIP5 knockdown decreased proliferation by 28 and 38%, respectively, according to the MTT and CCK-8 assays. Migration and invasion decreased by 54 and 68%, respectively, according to the Transwell assays. COX2 expression was decreased by 68 and 75% at the mRNA and protein level, respectively, and cyclin D1 mRNA and protein expression was decreased following 62 and 60%, respectively, by knockdown of ZIP5, which upregulated the mRNA and protein expression of E-cadherin by 80 and 60%, respectively. ZIP5 knockdown inhibited the proliferation, migration and invasion of ESCC and suppressed COX2, cyclin D1 and E-cadherin expression, which led to the inhibition of cell progression in ESCC.

Synthesis, structure, photoluminescence and antitumour activity of zinc complex based on 2-(2-(1H-benzo-[d]imidazol-2-yl)benzyl)-1H-benzo-[d]imidazole

A new complex [Zn(bbb)Cl2]·DMF, where bbb is 2-(2-(1H-benzo[d]imidazol-2-yl)benzyl)-1H-benzo[d]imidazole, was synthesized and characterized by element analysis, (1)H NMR and X-ray single crystal structure analyses. For complex: crystal system, triclinic, space group, P-1, a=9.4661(13), b=10.3534(14), c=13.0025(18)Å, α=73.477(2), β=80.743(2), γ=88.658(2)°, V=1205.5(3)Å(3), Z=2. In this complex, the Zn(2+) distorted tetrahedron geometry is coordinated by two nitrogen atoms from 2-(2-(1H-benzo[d]imidazol-2-yl)benzyl)-1H-benzo[d]imidazole and two Cl(-). The complex emits yellow green luminescence with the maximal emission peak at 550 nm in DMF solution. The complex exhibits inhibition on the growth of Eca109 cancer cell with IC50 value of 8.9±1.1 μM, which was lower than that of cisplatin (14.3±1.4 μM). This complex has potential application in treatment of esophageal cancer.

Zinc and gastrointestinal disease

This review is a current summary of the role that both zinc deficiency and zinc supplementation can play in the etiology and therapy of a wide range of gastrointestinal diseases. The recent literature describing zinc action on gastrointestinal epithelial tight junctions and epithelial barrier function is described. Zinc enhancement of gastrointestinal epithelial barrier function may figure prominently in its potential therapeutic action in several gastrointestinal diseases.

Targeted expression of ornithine decarboxylase antizyme prevents upper aerodigestive tract carcinogenesis in p53-deficient mice

Upper aerodigestive tract (UADT) cancers of the oral cavity and esophagus are a significant global health burden, and there is an urgent need to develop relevant animal models to identify chemopreventive and therapeutic strategies to combat these diseases. Antizyme (AZ) is a multifunctional negative regulator of cellular polyamine levels, and here, we evaluate the susceptibility of keratin 5 (K5)-AZ transgenic mice to tumor models that combine chemical carcinogenesis with dietary and genetic risk factors known to influence human susceptibility to UADT cancer and promote UADT carcinogenesis in mice. First, p53(+/-) and K5-AZ/p53(+/-) (AZ/p53(+/-)) mice were placed on a zinc-deficient (ZD) or zinc-sufficient (ZS) diet and chronically exposed to 4-nitroquinoline 1-oxide. Tongue tumor incidence, multiplicity and size were substantially reduced in both ZD and ZS AZ/p53(+/-) mice compared with p53(+/-). AZ expression also reduced progression to carcinoma in situ or invasive carcinoma and decreased expression of the squamous cell carcinoma biomarkers K14, cyclooxygenase-2 and metallothionein. Next, AZ-expressing p53(+/-) and p53 null mice were placed on the ZD diet and treated with a single dose of N-nitrosomethylbenzylamine. Regardless of p53 status, forestomach (FST) tumor incidence, multiplicity and size were greatly reduced with AZ expression, which was also associated with a significant decrease in FST epithelial thickness along with reduced proliferation marker K6 and increased differentiation marker loricrin. These studies demonstrate the powerful tumor suppressive effects of targeted AZ expression in two distinct and unique mouse models and validate the polyamine metabolic pathway as a target for chemoprevention of UADT cancers.

Effects of cigarette smoke and ethanol intake on mouse oesophageal mucosa changes induced by dietary zinc deficiency and deoxycholic acid supplementation

The noxious effects of dietary zinc deficiency (ZD) and deoxycholic bile acid (DCA) supplementation in the oesophagus were investigated. The additional influence of cigarette smoke and ethanol intake on the changes in the oesophageal mucosa induced by dietary ZD plus DCA was also assessed. Male C57BL/6 mice were allocated into four groups: Group 1 was fed control diet and groups 2-4 were fed ZD plus DCA diet. After 5 weeks, groups 3 and 4 were exposed to 10% ethanol intake or cigarette smoke for 15 weeks, respectively. All animals were euthanized at the end of week 20, and the oesophagus, lung, liver and colon were collected and analysed by conventional morphology. Cell proliferation was assessed in the oesophageal mucosa by Ki-67 immunohistochemistry and cyclooxygenase 2 (COX-2) protein by Western blotting. Dietary ZD plus DCA treatment induced mild hyperkeratosis and hyperplasia, increased cell proliferation index and COX-2 protein expression in the oesophagus, and intranuclear inclusion, karyocytomegaly and microvesicular fatty change in the liver. Cigarette smoke increased COX-2 protein expression in oesophageal mucosa and irregular enlargement of alveolus and alveolar ductal air spaces, while ethanol enhanced liver damage induced by ZD plus DCA diet. These findings indicate that dietary ZD plus DCA treatment during 20 weeks induces a pattern of chemical oesophageal injury but not Barrett's-like lesions.

The levels of zinc and molybdenum in hair and food grain in areas of high and low incidence of esophageal cancer: a comparative study

The outcome of different studies on the role of Zn & Mo in esophageal cancer (EC) is conflicting. Here, the levels of those elements in hair as well as food grain of two different ethnic populations across two continents have been studied to explore their role in EC. Two different ethnic populations are taken from (i) Eastern Cape, South Africa (RSA), an area of very high incidence of EC and (ii) West Bengal, India, an area of low incidence of that disease. Each ethnic population is divided into two groups: case and control (n=30 for all groups). Hair samples from all groups and food grains from RSA and India are analyzed for Zn & Mo content. This study shows a strong correlation between reduced levels of those elements in hair and the development of EC in RSA (both Zn & Mo: p<0.0001), though it is only suggestive in Indian context (both Zn & Mo: p≥0.05). Interestingly, control group of RSA shows significantly reduced level of those elements in hair even with respect to Indian case group (Zn: p<0.001 & Mo: p<0.00001). Food grain from RSA has significantly reduced level of those elements with respect to India (both Zn & Mo: p<0.0001). This deficiency of Zn & Mo in food grains can be correlated to the deficiency of those elements in hair of RSA population. The deficiency of Zn & Mo can be correlated to the development of EC.

The immunological contribution of NF-κB within the tumor microenvironment: a potential protective role of zinc as an anti-tumor agent

Over decades, cancer treatment has been mainly focused on targeting cancer cells and not much attention to host tumor microenvironment. Recent advances suggest that the tumor microenvironment requires in-depth investigation for understanding the interactions between tumor cell biology and immunobiology in order to optimize therapeutic approaches. Tumor microenvironment consists of cancer cells and tumor associated reactive fibroblasts, infiltrating non-cancer cells, secreted soluble factors or molecules, and non-cellular support materials. Tumor associated host immune cells such as Th(1), Th(2), Th17, regulatory cells, dendritic cells, macrophages, and myeloid-derived suppressor cells are major components of the tumor microenvironment. Accumulating evidence suggests that these tumor associated immune cells may play important roles in cancer development and progression. However, the exact functions of these cells in the tumor microenvironment are poorly understood. In the tumor microenvironment, NF-κB plays an important role in cancer development and progression because this is a major transcription factor which regulates immune functions within the tumor microenvironment. In this review, we will focus our discussion on the immunological contribution of NF-κB in tumor associated host immune cells within the tumor microenvironment. We will also discuss the potential protective role of zinc, a well-known immune response mediator, in the regulation of these immune cells and cancer cells in the tumor microenvironment especially because zinc could be useful for conditioning the tumor microenvironment toward innovative cancer therapy.

Proton Pump Inhibitors Interfere With Zinc Absorption and Zinc Body Stores

Background

Proton pump inhibitors (PPIs) cause a sharp elevation of gastro-duodenal luminal pH which in turn has resulted in reports of reduced absorption of magnesium and certain other nutrients.

Methods

Gastroesophageal reflux disease (GERD) patients on long-term PPI therapy (> 6 months) or healthy test subjects (not on any acid preventive or neutralizing medication) were administered oral doses of zinc gluconate (26.2 mg zinc, twice daily) for 14 days followed by 5 cc venous blood samples. Plasma was analyzed for total zinc content by atomic absorption spectrophotometry. Baseline plasma and red blood cell zinc levels were also measured in these two groups when not taking any zinc supplementation.

Results

Plasma zinc levels of healthy controls increased by 126% during the period of zinc supplementation compared to only a 37% increase for individuals on long-term PPI therapy. On their normal diet (with no zinc supplementation), PPI-users had a 28% lower plasma zinc level than healthy controls (P < 0.005).

Conclusions

PPI use dramatically reduces supplemental zinc uptake and can result in decreased zinc body stores. Certain individuals on long-term PPI therapy, such as infants being treated for colic, may be at risk for decreased systemic levels of trace metals needed for developmental, regenerative and immunological requirements.

Effect of zinc supplementation on N-nitrosomethylbenzylamine-induced forestomach tumor development and progression in tumor suppressor-deficient mouse strains

Zinc deficiency is associated with high incidences of esophageal and other cancers in humans and leads to a highly proliferative hyperplastic condition in the upper gastrointestinal tract in laboratory rodents. Zn replenishment reduces the incidence of lingual, esophageal and forestomach tumors in Zn-deficient rats and mice. While previous animal studies focused on Zn deficiency, we have investigated the effect of Zn supplementation on carcinogenesis in Zn-sufficient mice of wild-type and tumor suppressor-deficient mouse strains. All mice received N-nitrosomethylbenzylamine and half the mice of each strain then received Zn supplementation. At killing, mice without Zn supplementation had developed more tumors than Zn-supplemented mice: wild-type C57BL/6 mice developed an average of 7.0 versus 5.0 tumors for Zn supplemented (P < 0.05); Zn-supplemented Fhit-/- mice averaged 5.7 versus 8.0 for control mice (P < 0.01); Zn-supplemented Fhit-/-Nit1-/- mice averaged 5.4 versus 9.2 for control mice (P < 0.01) and Zn-supplemented Fhit-/-Rassf1a-/- (the murine gene) mice averaged 5.9 versus 9.1 for control mice (P < 0.01). Zn supplementation reduced tumor burdens by 28% (wild-type) to 42% (Fhit-/-Nit1-/-). Histological analysis of forestomach tissues also showed significant decreases in severity of preneoplastic and neoplastic lesions in Zn-supplemented cohorts of each mouse strain. Thus, Zn supplementation significantly reduced tumor burdens in mice with multiple tumor suppressor deficiencies. When Zn supplementation was begun at 7 weeks after the final carcinogen dose, the reduction in tumor burden was the same as observed when supplementation began immediately after carcinogen dosing, suggesting that Zn supplementation may affect tumor progression rather than tumor initiation.

A review of in vitro and in vivo models of oesophageal and gastric cancer

IMPORTANCE OF THE FIELD

Oesophageal and gastric cancers are leading causes of cancer-related mortality. In the era of targeted therapy and individualized treatment strategies, novel treatments for upper-gastrointestinal cancers are only just emerging compared to significant advances in other solid tumour types such as colorectal, breast and lung cancers. Clinical trials are investigating the value of established targeted agents for the treatment of oesophageal and gastric malignancies; however none are used in routine clinical practice.

AREAS COVERED IN THIS REVIEW

In this review we have looked at current in vitro and in vivo models of oesophageal and gastric cancers which may improve our understanding of the biology of these tumours and lead to the development of new preventative, diagnostic and therapeutic approaches.

WHAT THE READER WILL GAIN

We discuss the limitations of our current models and the challenges associated with research into these cancers.

TAKE HOME MESSAGE

The lack of appropriate models for drug development in oesophageal and gastric cancers has hindered the progress of targeted therapy in this field.

Environmental causes of esophageal cancer

This article reviews the environmental risk factors and predisposing conditions for the two main histologic types of esophageal cancer. Tobacco smoking, excessive alcohol consumption, drinking maté, low intake of fresh fruits and vegetables, achalasia, and low socioeconomic status increase the risk of esophageal squamous cell carcinoma. Results of investigations on other potential risk factors, including opium consumption, intake of hot drinks, eating pickled vegetables, poor oral health, and exposure to human papillomavirus, polycyclic aromatic hydrocarbons, N-nitroso compounds, acetaldehyde, and fumonisins are discussed. Gastroesophageal reflux, obesity, tobacco smoking, hiatal hernia, achalasia, and, probably, absence of H pylori in the stomach increase the risk of esophageal adenocarcinoma. Results of studies investigating other factors are also discussed.

Association between copper excess, zinc deficiency, and TP53 mutations in esophageal squamous cell carcinoma from Kashmir Valley, India--a high risk area

Trace element deficiency or excess is implicated in the development or progression in some cancers. Here we report the elevated level of copper and low level of zinc in the plasma of esophageal cancer patients in Kashmir India--a high incidence area. The average level of copper was significantly higher (P < 0.0001) for patients than for controls, with a mean concentration of 169 microg/dl and 149 microg/dl for patients and controls, respectively. The control group consisted of 55 healthy individuals matched for age, sex, and place of residence of the patients. In contrast, the average level of zinc in patients was significantly lower than in controls (P < 0.0001), with a mean concentration of 86.8 microg/dl and 96.1 microg/dl for patients and controls, respectively. The levels of both copper and zinc showed significant differences based on gender and age in patients as compared to controls. Similarly, smokers depicted a significant increase in serum copper (N = 39, P = 0.002) and a decrease in serum zinc approaching level of significance in the patient group as compared to controls. The copper and zinc levels were significantly altered in patients (N = 40) when compared to controls as a function of snuff consumption. The differences in the levels of copper and zinc showed significant association with the consumption of local salted tea up to 1,500 ml per day, but the changes were insignificant beyond that. Patients with poorly differentiated tumors (N = 7) had a higher copper concentration than those with moderately or well-differentiated tumors (P < 0.0001). To validate the general notion that imbalance in copper and zinc levels may lead to higher prevalence of TP53 mutations, we compared the 3 variables, and no association was found between copper concentration and TP53 mutation status; but patients with TP53 mutant tumor had lower zinc levels than those with no mutation. In conclusion, our results point toward a role of the trace element imbalance in the esophageal tumorigenesis in high-risk Kashmiri population exposed to a range of nitroso compounds or their precursors. Further prospective cohort studies are warranted to determine whether change in the plasma zinc and copper homeostasis may represent an independent risk factor for this malignancy as well as a possible target for preventive intervention.

Nutritionally regulated biomarkers for breast cancer

Recent data on the expression and function of the ZIP family of proteins has suggested that these zinc transporters may be useful biomarkers for the diagnosis and prognosis of human breast cancer. This exciting new area of research opens the door for the use of a variety of nutritionally regulated genes and proteins as screening tools not only for breast cancer, but for a variety of other diseases for which early detection is important.

Prevention of upper aerodigestive tract cancer in zinc-deficient rodents: inefficacy of genetic or pharmacological disruption of COX-2

Zinc deficiency in humans is associated with an increased risk of upper aerodigestive tract (UADT) cancer. In rodents, zinc deficiency predisposes to carcinogenesis by causing proliferation and alterations in gene expression. We examined whether in zinc-deficient rodents, targeted disruption of the cyclooxygenase (COX)-2 pathway by the COX-2 selective inhibitor celecoxib or by genetic deletion prevent UADT carcinogenesis. Tongue cancer prevention studies were conducted in zinc-deficient rats previously exposed to a tongue carcinogen by celecoxib treatment with or without zinc replenishment, or by zinc replenishment alone. The ability of genetic COX-2 deletion to protect against chemically-induced forestomach tumorigenesis was examined in mice on zinc-deficient versus zinc-sufficient diet. The expression of 3 predictive biomarkers COX-2, nuclear factor (NF)-kappa B p65 and leukotriene A(4) hydrolase (LTA(4)H) was examined by immunohistochemistry. In zinc-deficient rats, celecoxib without zinc replenishment reduced lingual tumor multiplicity but not progression to malignancy. Celecoxib with zinc replenishment or zinc replenishment alone significantly lowered lingual squamous cell carcinoma incidence, as well as tumor multiplicity. Celecoxib alone reduced overexpression of the 3 biomarkers in tumors slightly, compared with intervention with zinc replenishment. Instead of being protected, zinc-deficient COX-2 null mice developed significantly greater tumor multiplicity and forestomach carcinoma incidence than wild-type controls. Additionally, zinc-deficient COX-2-/- forestomachs displayed strong LTA(4)H immunostaining, indicating activation of an alternative pathway under zinc deficiency when the COX-2 pathway is blocked. Thus, targeting only the COX-2 pathway in zinc-deficient animals did not prevent UADT carcinogenesis. Our data suggest zinc supplementation should be more thoroughly explored in human prevention clinical trials for UADT cancer.

Influence of a nonfragile FHIT transgene on murine tumor susceptibility

FHIT, at a constitutively active chromosome fragile site, is often a target of chromosomal aberrations and deletion in a large fraction of human tumors. Inactivation of murine Fhit allelessignificantly increases susceptibility of mice to spontaneous and carcinogen-induced tumorigenesis. In this study, transgenic mice, carrying a human FHIT cDNA under control of the endogenous promoter, were produced to determine the effect of Fhit expression, from a nonfragile cDNA transgene outside the fragile region, on carcinogen-induced tumor susceptibility of wildtype and Fhit heterozygous mice. Mice received sufficient oral doses of N-nitrosomethybenzylamine (NMBA) to cause forestomach tumors in >80% of nontransgenic control mice. Although the level of expression of the FHIT transgene in the recombinant mouse strains was much lower than the level of endogenous Fhit expression, the tumor burden in NMBA-treated male transgenic mice was significantly reduced, while female transgenic mice were not protected. To determine if the difference in protection could be due to differences in epigenetic changes at the transgene loci in male versus female mice, we examined expression, hypermethylation and induced re-expression of FHIT transgenes in male and female mice or cells derived from them. The transgene was methylated in male and female mice and in cell lines established from male and female transgenic kidneys, the FHIT locus was both hypermethylated and deacetylated. It is likely that the FHIT transgene is more tightly silenced in female transgenic mice, leading to a lack of protection from tumor induction.

Inactivation of the Wwox gene accelerates forestomach tumor progression in vivo

The WWOX gene encodes a tumor suppressor spanning the second most common human fragile site, FRA16D. Targeted deletion of the Wwox gene in mice led to an increased incidence of spontaneous and ethyl nitrosourea-induced tumors. In humans, loss of heterozygosity and reduced or loss of WWOX expression has been reported in esophageal squamous cell cancers (SCC). In the present study, we examined whether inactivation of the Wwox gene might lead to enhanced esophageal/forestomach tumorigenesis induced by N-nitrosomethylbenzylamine. Wwox+/- and Wwox+/+ mice were treated with six intragastric doses of N-nitrosomethylbenzylamine and observed for 15 subsequent weeks. Ninety-six percent (25 of 26) of Wwox+/- mice versus 29% (10 of 34) of Wwox+/+ mice developed forestomach tumors (P = 1.3 x 10(-7)). The number of tumors per forestomach was significantly greater in Wwox+/- than in Wwox+/+ mice (3.2 +/- 0.34 versus 0.47 +/- 0.17; P < 0.0001). In addition, 27% of Wwox+/- mice had invasive SCC in the forestomach, as compared with 0% of wild-type controls (P = 0.002). Intriguingly, forestomachs from Wwox+/- mice displayed moderately strong Wwox protein staining in the near-normal epithelium, but weak and diffuse staining in SCC in the same tissue section, a result suggesting that Wwox was haploinsufficient for the initiation of tumor development. Our findings provide the first in vivo evidence of the tumor suppressor function of WWOX in forestomach/esophageal carcinogenesis and suggest that inactivation of one allele of WWOX accelerates the predisposition of normal cells to malignant transformation.

Zinc deficiency potentiates induction and progression of lingual and esophageal tumors in p53-deficient mice

Upper aerodigestive tract (UADT) cancer, including oral and esophageal cancer, is an important cause of cancer deaths worldwide. Patients with UADT cancer are frequently zinc deficient (ZD) and show a loss of function of the pivotal tumor suppressor gene p53. The present study examined whether zinc deficiency in collaboration with p53 insufficiency (p53+/-) promotes lingual and esophageal tumorigenesis in mice exposed to low doses of the carcinogen 4-nitroquinoline 1-oxide. In wild-type mice, ZD significantly increased the incidence of lingual and esophageal tumors from 0% in zinc sufficient (ZS) ZS:p53+/+ mice to approximately 40%. On the p53+/- background, ZD:p53+/- mice had significantly greater tumor incidence and multiplicity than ZS:p53+/- and ZD:p53+/+ mice, with a high frequency of progression to malignancy. Sixty-nine and 31% of ZD:p53+/- lingual and esophageal tumors, respectively, were squamous cell carcinoma versus 19 and 0% of ZS:p53+/- tumors (tongue, P = 0.003; esophagus, P = 0.005). Immunohistochemical analysis revealed that the increased cellular proliferation observed in preneoplastic lingual and esophageal lesions, as well as invasive carcinomas, was accompanied by overexpression of cytokeratin 14, cyclooxygenase-2 and metallothionein. In summary, a new UADT cancer model is developed in ZD:p53+/- mouse that recapitulates aspects of the human cancer and provides opportunities to probe the genetic changes intrinsic to UADT carcinogenesis and to test strategies for prevention and reversal of this deadly cancer.

Zinc requirements and the risks and benefits of zinc supplementation

The adult human contains 2-3g of zinc, about 0.1% of which are replenished daily. On this basis and based on estimates of bioavailability of zinc, dietary recommendations are made for apparently healthy individuals. Absent chemical, functional, and/or physical signs of zinc deficiency are assumed indicative of adequacy. More specific data are seldom available. Changing food preferences and availability, and new food preparation, preservation, and processing technologies may require re-evaluation of past data. Conservative estimates suggest that 25% of the world's population is at risk of zinc deficiency. Most of the affected are poor, and rarely consume foods rich in highly bioavailable zinc, while subsisting on foods that are rich in inhibitors of zinc absorption and/or contain relatively small amounts of bioavailable zinc. In contrast, among the relatively affluent, food choice is a major factor affecting risk of zinc deficiency. An additional problem, especially among the relatively affluent, is risk of chronic zinc toxicity caused by excessive consumption of zinc supplements. High intakes of zinc relative to copper can cause copper deficiency. A major challenge that has not been resolved for maximum health benefit is the proximity of the recommended dietary allowance (RDA) and the reference dose (RfD) for safe intake of zinc. Present recommendations do not consider the numerous dietary factors that influence the bioavailability of zinc and copper, and the likelihood of toxicity from zinc supplements. Thus the current assumed range between safe and unsafe intakes of zinc is relatively narrow. At present, assessment of zinc nutriture is complex, involving a number of chemical and functional measurements that have limitations in sensitivity and specificity. This approach needs to be enhanced so that zinc deficiency or excess can be detected early. An increasing number of associations between diseases and zinc status and apparently normal states of health, where additional zinc might be efficacious to prevent certain conditions, point at the pharmacology of zinc compounds as a promising area. For example, relationships between zinc and diabetes mellitus are an area where research might prove fruitful. In our opinion, a multidisciplinary approach will most likely result in success in this fertile area for translational research.

Zinc deficiency, DNA damage and cancer risk

A large body of evidence suggests that a significant percentage of deaths resulting from cancer in the United States could be avoided through greater attention to proper and adequate nutrition. Although many dietary compounds have been suggested to contribute to the prevention of cancer, there is strong evidence to support the fact that zinc, a key constituent or cofactor of over 300 mammalian proteins, may be of particular importance in host defense against the initiation and progression of cancer. Remarkably, 10% of the U.S. population consumes less than half the recommended dietary allowance for zinc and are at increased risk for zinc deficiency. Zinc is known to be an essential component of DNA-binding proteins with zinc fingers, as well as copper/zinc superoxide dismutase and several proteins involved in DNA repair. Thus, zinc plays an important role in transcription factor function, antioxidant defense and DNA repair. Dietary deficiencies in zinc can contribute to single- and double-strand DNA breaks and oxidative modifications to DNA that increase risk for cancer development. This review will focus on potential mechanisms by which zinc deficiency impairs host protective mechanisms designed to protect against DNA damage, enhances susceptibility to DNA-damaging agents and ultimately increases risk for cancer.

Zinc concentration in esophageal biopsy specimens measured by x-ray fluorescence and esophageal cancer risk

BACKGROUND

In rodents, zinc deficiency potentiates the effects of certain nitrosamines that act as esophageal carcinogens. Studies of the association between zinc and esophageal squamous cell carcinoma in humans have been hampered by plasma zinc homeostasis, which obscures individual differences in total zinc stores, and by the uncertainty regarding zinc bioavailability when estimating dietary zinc intake because phytate from whole grains effectively prohibits zinc absorption. By using baseline tissue biopsy specimens collected in a prospective observational study, we determined the association between incident esophageal squamous cell carcinoma and baseline element concentrations in tissue sections from residents of Linzhou, China, participating in a nutrition intervention trial.

METHODS

We used x-ray fluorescence spectroscopy to measure zinc, copper, iron, nickel, and sulfur concentrations in single 5-microm-thick sections from formalin-fixed, paraffin-embedded esophageal biopsy specimens collected in 1985 from 60 eventual case and 72 control subjects. Subjects were matched on baseline histology and followed for 16 years. We used Cox proportional hazards models to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between each element and risk of incident esophageal cancer. All statistical tests were two-sided.

RESULTS

The risk of developing esophageal cancer was much lower for subjects in the highest quartile of esophageal tissue zinc concentration compared with those in the lowest quartile (HR = 0.21, 95% CI = 0.065 to 0.68). The association was statistically significant across quartiles (P(trend) = .015). Individuals in the highest quartile of sulfur concentration had a lower risk of esophageal cancer than individuals in the lowest quartile (HR = 0.29, 95% CI = 0.095 to 0.85), but the association across quartiles was not statistically significant (P(trend) = .081). There was no association between copper, iron, or nickel concentrations and risk of esophageal cancer.

CONCLUSION

High tissue zinc concentration was strongly associated with a reduced risk of developing esophageal squamous cell carcinoma. X-ray fluorescence spectroscopy can be used to assess relationships among concentrations of both nutritional and toxic elements and disease risk in banked tissue specimens.

Zinc stabilizes adenomatous polyposis coli (APC) protein levels and induces cell cycle arrest in colon cancer cells

In the present study, we investigated the mechanisms by which zinc causes growth arrest in colon cancer cells. The results suggest that zinc treatment stabilizes the levels of the wild-type adenomatous polyposis coli (APC) protein at the post-translational level since the APC mRNA levels and the promoter activity of the APC gene were decreased in HCT-116 cells (which express the wild-type APC gene) after treatment with ZnCl2. Increased levels of wild-type but not truncated APC proteins were required for the ZnCl2-mediated G2/M phase arrest in different colon cancer cell lines. We further tested whether serum-stimulation, which induces cell cycle arrest in the S phase, can relieve ZnCl2-induced G2/M phase arrest of HCT-116 cells. Results showed that in the HCT-116 cells pretreated with ZnCl2, the serum-stimulation neither changed the distribution of G2/M phase arrested cells nor the increased levels of APC protein. The G2/M phase arrest correlated with retarded growth of HCT-116 cells. To further establish that wild-type APC protein plays a role in ZnCl2-induced G2/M arrest, we treated SW480 colon cancer cells that express truncated APC protein. We found that ZnCl2 treatment did not induce G2/M phase arrest in SW480 cells; however, the cell growth was retarded due to the loss of E-cadherin and alpha-tubulin levels. These results suggest that ZnCl2 inhibits the proliferation of colon cancer cells (which carry the wild-type APC gene) through stabilization of the APC protein and cell cycle arrest in the G2/M phase. On the other hand, ZnCl2 inhibits the proliferation of colon cancer cells (which carry the mutant APC gene) by disrupting cellular attachment and microtubule stability.

Heme iron, zinc and upper digestive tract cancer: The Iowa Women's Health Study

We examined associations among dietary heme iron as a possible pro-oxidant, dietary zinc as a possible antioxidant, and the incidence of upper digestive tract cancer; 34,708 postmenopausal women, aged 55-69 years at baseline who completed a food frequency questionnaire, were followed 16 years. There were 75 upper digestive tract cancer cases (52 gastric cancer and 23 esophageal cancer). When heme iron and zinc were mutually adjusted, in dose-response manners, heme iron intake was positively associated with the risk of upper digestive tract cancer, while zinc intake was inversely associated with risk. After adjusting for age, total energy intake, cigarette smoking and alcohol consumption, relative risks for quintiles of heme iron intake were 1.0, 1.53, 2.15, 3.05 and 2.83 (p for trend = 0.06) and corresponding relative risks for zinc intake were 1.0, 0.86, 0.42, 0.37 and 0.13 (p for trend < 0.01). Additional adjustment for body mass index, physical activity, hormone replacement therapy, multivitamin intake and intake of saturated fat, vitamin C, vitamin E and folate did not change the results. Higher intake of heme iron is associated with higher risk, while higher intake of zinc is associated with lower, risk of upper digestive tract cancer.

Differentially expressed genes execute zinc-induced apoptosis in precancerous esophageal epithelium of zinc-deficient rats

Zinc deficiency (ZD) in rats increases esophageal cell proliferation and the incidence of N-nitrosomethylbenzylamine-induced esophageal tumors. Conversely, zinc replenishment (ZR) rapidly induces apoptosis in esophageal epithelia and reverses cancer development. We investigated gene expression changes in ZR versus ZD esophageal epithelia to identify differentially expressed genes associated with the antitumor effect of ZR. Weanling rats were fed a ZD diet for 6 weeks to establish esophageal cell proliferation or a zinc-sufficient (ZS) diet. Then, 10 ZD rats were treated with zinc gluconate intragastrically and switched to ZS diet; the remaining 10 ZD and ZS animals were treated with saline. All animals were killed 26-28 h later. Using cDNA microarrays, real-time polymerase chain reaction amplification and RNA hybridization techniques, we identified novel differentially expressed genes, including a RNA-binding protein with two RNA recognition motifs and a zinc knuckle (ZD7), and a DNA/RNA helicase with a DEAD box (ZD10) with two splice variants, ZD10a and ZD10b. In situ hybridization detected increased mRNA expression of ZD7, ZD10a and ZD10b in ZR esophageal epithelia, which displayed markedly increased occurrence of apoptotic cells, relative to ZD epithelia. Overexpression of ZD7 in human esophageal cancer cells resulted in induction of apoptosis and activation of caspase-3 and -7, activities that were inhibited by caspase-specific inhibitors. In addition, ZD7 mRNA levels and zinc-induced apoptosis in rat squamous carcinoma cells were reduced by specific small interfering ribonucleic acids. Thus, ZR rapidly induces ZD7 and ZD10 expression, which in turn stimulates apoptosis. These results provide the beginnings of a molecular pathway for zinc-induced apoptosis under conditions that reverse esophageal tumor initiation.

Evaluation of cell proliferation in rat tissues with BrdU, PCNA, Ki-67(MIB-5) immunohistochemistry and in situ hybridization for histone mRNA

The standard method for assessment of cell proliferation in paraffin-embedded tissue sections is 5-bromodeoxyuridine (BrdU) immunohistochemistry (IHC). BrdU can be administered to laboratory animals via IP injections, is readily incorporated into nuclei during the DNA synthetic phase of the cell cycle, and is detected with an anti-BrdU antibody. This method has several disadvantages, and an accurate method for evaluation of proliferative activity that can substitute for BrdU IHC, when necessary, is of great interest to investigators. Alternative methods for detection of proliferating cells in tissue sections are proliferating cell nuclear antigen (PCNA) IHC, Ki-67 IHC, and in situ hybridization (ISH) for histone mRNA. To determine the optimal choice, we analyzed the correlation of anti-PCNA, anti-Ki-67(MIB-5), and histone mRNA labeling indices (LIs) with anti-BrdU LI in rat highly replicative (renewing) tissues. The correlation between anti-BrdU and histone mRNA LIs, as well as the correlation between anti-BrdU and anti-Ki-67 LIs, was statistically significant. There was no significant correlation between anti-BrdU and anti-PCNA LIs. These results suggest that both ISH for histone mRNA and IHC with MIB-5 are preferable techniques for assessment of cell proliferation in rat paraffin-embedded renewing tissues compared to PCNA IHC. They can substitute for BrdU IHC when necessary.

Deletion of histidine triad nucleotide-binding protein 1/PKC-interacting protein in mice enhances cell growth and carcinogenesis

PKC-interacting protein (PKCI), also designated histidine triad nucleotide-binding protein 1, belongs to the histidine triad (HIT) family of proteins. Its structure is highly conserved from bacteria to humans and shares homology with the tumor-suppressor gene fragile histidine triad (FHIT). Although it was originally thought to inhibit PKC, its actual physiologic function is not known. Therefore, we used the technique of homologous recombination to generate homozygous deleted PKCI-/- mice. These mice display normal fetal and adult development. However, when mouse embryo fibroblasts were established from 13.5-day embryos and serially passaged the PKCI-/- cells displayed an increase in growth rate and underwent spontaneous immortalization, whereas the PKCI+/+ cells senesced and ceased growing. Furthermore, the PKCI-/- mouse embryo fibroblasts displayed increased resistance to cytotoxicity by ionizing radiation. In view of these findings we examined possible effects of PKCI on susceptibility to carcinogenicity. Both PKCI+/+ and PKCI-/- mice were treated with the chemical carcinogen N-nitrosomethylbenzylamine (NMBA) by intragastric administration and killed 12 weeks later. As expected with this protocol, NMBA induced squamous tumors (both papillomas and carcinomas) of the forestomach. The incidence, multiplicity per mouse, volume, and degree of malignancy of these tumors were significantly greater in the PKCI-/- than in the PKCI+/+ mice. Furthermore, four adenomas and one adenocarcinoma of the glandular stomach were found in the NMBA-treated PKCI-/- mice but no tumors of the glandular stomach were found in the NMBA-treated PKCI+/+ mice or in any of the untreated mice. Taken together, these findings suggest that, like FHIT, PKCI may normally play a tumor-suppressor role. The possible role of PKCI as a tumor suppressor in humans remains to be determined.

Nutrition and diet in the development of gastrointestinal cancer

Diet plays a role in the prevention and development of gastrointestinal cancers. The majority of available research consists of case-control studies, but the number of clinical trials is growing. The dietary recommendations to reduce gastrointestinal cancer risk include lowering total energy, fat, and saturated fat intake; avoidance of grilled and smoked foods; avoidance of alcohol; and increasing intake of fruits, vegetables, and fiber. Studies of esophageal cancer support these dietary approaches, with the exception of dietary fat reduction and increased green tea intake. For gastric cancer, consuming additional fruits and vegetables, including those high in ascorbic acid, may reduce risk, and the capacity for diet to alter Helicobacter pylori infection should be explored. Recent interventional trials do not support a role for high-fiber or low-fat diets in reducing development of colon adenomas, although the evidence does not rule out efficacy at earlier stages of disease. Finally, the evidence for a relationship between pancreatic cancer and diet remains sparse and warrants additional investigation.

Changing role of in vivo models in columnar-lined lower esophagus

Columnar-lined lower esophagus (CLE) or Barrett's esophagus (BE) is caused by chronic reflux of the gastrointestinal tract and can progress to invasive adenocarcinoma. However, the pathophysiology, cell of origin, and management of this condition is incompletely understood. This review evaluates the role of in vivo models in resolving these debates. A search was performed on the Ovid and Pub Medline for 1964-2001 and Cochrane Collaboration. The keywords used were adenocarcinoma, animal model, Barrett's esophagus, columnar-lined esophagus, esophageal neoplasms, and esophageal carcinogenesis. All relevant papers were scrutinized and an attempt at tabulation was made. In vivo models have been used at several stages of debate on the pathophysiology of BE. They provide conclusive evidence for its acquired nature secondary to duodenogastroesophageal reflux. The cell of origin of experimental BE may arise from adjacent columnar epithelium, basal layer multipotent cells, or esophageal glands. Experimental work on BE is lacking in assessing therapeutic modalities.

Pancreatic metallothionein-I may play a role in zinc homeostasis during maternal dietary zinc deficiency in mice

Herein, the function of pancreatic metallothionein (MT)-I during zinc deficiency in pregnancy was examined using transgenic mice, which constitutively express the mouse MT-I gene driven by the rat elastase I promoter. Pancreatic MT protein levels and zinc levels were elevated significantly in the transgenic mice compared with those in control mice. Pregnant transgenic and control mice were fed zinc-deficient (1 micro g/g beginning at d 8) or zinc-adequate (50 micro g/g) diets during pregnancy, and the effects on the morphology of embryos were determined at d 14 of pregnancy (d 1 = vaginal plug). As other indicators of zinc deficiency, maternal pancreatic MT levels, as well as the expression of zinc-regulated genes in the embryonic visceral yolk sac were examined. Under these experimental conditions of moderate dietary zinc deficiency, 21.3% of the embryos in control mice exhibited morphological defects, whereas only 5.8% of the embryos in the elastase-MT-I transgenic females had developed abnormally by d 14. Surprisingly, dietary zinc deficiency caused a >95% decrease in pancreatic MT protein concentration in these transgenic mice. This suggests the post-transcriptional control of MT protein levels during zinc deficiency because the rat elastase I promoter is not metal-regulated. The decrease in pancreatic MT protein levels was paralleled by a dramatic decrease in the relative abundance of MT-I mRNA and a dramatic increase in the relative abundance of the zinc/iron regulated transporter-related zinc transporter-4 (ZIP4) mRNA in the embryonic visceral yolk sac. Thus, the constitutive overexpression of pancreatic MT-I in these mice attenuated, but did not prevent the effects of maternal or embryonic zinc deficiency under these conditions. Overall, these findings are consistent with the hypothesis that mouse pancreatic MT-I may participate in providing a labile pool of maternal zinc for the developing embryo during periods of zinc deficiency.

Low intracellular zinc induces oxidative DNA damage, disrupts p53, NFkappa B, and AP1 DNA binding, and affects DNA repair in a rat glioma cell line

Approximately 10% of the U.S. population ingests <50% of the current recommended daily allowance for zinc. We investigate the effect of zinc deficiency on DNA damage, expression of DNA-repair enzymes, and downstream signaling events in a cell-culture model. Low zinc inhibited cell growth of rat glioma C6 cells and increased oxidative stress. Low intracellular zinc increased DNA single-strand breaks (comet assay). Zinc-deficient C6 cells also exhibited an increase in the expression of the zinc-containing DNA-repair proteins p53 and apurinic endonuclease (APE). Repletion with zinc restored cell growth and reversed DNA damage. APE is a multifunctional protein that not only repairs DNA but also controls DNA-binding activity of many transcription factors that may be involved in cancer progression. The ability of the transcription factors p53, nuclear factor kappaB, and activator protein 1 (AP1) to bind to consensus DNA sequences was decreased markedly with zinc deficiency, as assayed by electrophoretic mobility-shift assays. Thus, low intracellular zinc status causes oxidative DNA damage and induces DNA-repair protein expression, but binding of p53 and important downstream signals leading to proper DNA repair are lost without zinc.

Increased renal vascular resistance in zinc-deficient rats: role of nitric oxide and superoxide

1. Zinc deficiency (ZD) induces many kinds of pathological states. However, the effects of ZD on haemodynamics remain unclear. In the present study, we measured mean blood pressure (BP) and renal blood flow (RBF) under anaesthesia and calculated renal vascular resistance (RVR) from these parameters in rats maintained on a ZD diet (0.5 p.p.m. zinc) for 4 weeks. 2. Zinc deficiency did not change mean BP, but significantly reduced RBF and increased RVR (each P < 0.01). In addition, these effects of ZD were reversible. 3. Because Cu/Zn superoxide dismutase (SOD) is a zinc-containing enzyme and superoxide is a potent scavenger of nitric oxide (NO), a vasodilator, we hypothesized that one of the mechanisms by which ZD increases RVR is by decreasing NO bioavailability by the enhanced formation of superoxide due to low Cu/Zn SOD activity. To test this hypothesis, we observed the roles of NO and superoxide in the mechanism, after having confirmed the low activity of Cu/Zn SOD in the kidneys of ZD rats. 4. Administration of the SOD mimetic tempol (5 mg/kg per min) decreased RVR to a significantly greater extent in ZD rats compared with control, suggesting that superoxide was responsible for the mechanism. Low doses of the NO donor sodium nitroprusside (SNP; 2.0 micro g/kg per min, continuous) decreased RVR to a significantly smaller extent in ZD rats compared with control, whereas a high dose of SNP (0.75 mg/kg, bolus) decreased RVR to a significantly greater extent in ZD rats compared with control, suggesting that the mechanism includes an inhibition of NO activity in ZD, which is most likely to be a scavenging of NO by the activated superoxide. 5. In summary, ZD may increase RVR. The mechanism probably includes changes in NO and superoxide activities.

Extracellular zinc stimulates ERK-dependent activation of p21(Cip/WAF1) and inhibits proliferation of colorectal cancer cells

Zinc is an important trace element in the body and is involved in both the proliferation and growth arrest of many kinds of cells including colorectal epithelial cells. The aim of this study was to identify the molecular mechanism of the growth regulation of colorectal cancer cells by extracellular zinc. Zinc-stimulated activation of the mitogen-activated protein kinase (MAPK) cascade was measured by immunoblotting and Elk-1 dependent trans-reporter gene expression, and zinc-stimulated p21(Cip/WAF1) activation by immunoblotting, Northern blot analysis and immunochemistry. Cell proliferation was measured by thymidine and bromodeoxyuridine (BrdU) incorporation. By treating colorectal cancer cells with 100 microM ZnCl2, MAPKs were activated in two different phases, the initial weak activation occurred within 5 min and this was followed by a stronger and more prolonged activation. Zinc concomitantly activated Raf-1-MEK-MAPK kinases, and induced Elk-1 dependent trans-reporter gene expression. Prolonged activation of MAPKs by 100 microM of ZnCl2 resulted in the induction and nuclear localization of p21(Cip/WAF1) and was related to the inhibition of both thymidine and BrdU incorporations. These results not only suggest the presence of a mechanism for p21(Cip/WAF1) dependent negative regulation of colorectal cancer cell growth by zinc but also suggest potential usage of zinc to control the growth of colorectal cancer cells.

FHIT gene therapy prevents tumor development in Fhit-deficient mice

The tumor suppressor gene FHIT spans a common fragile site and is highly susceptible to environmental carcinogens. FHIT inactivation and loss of expression is found in a large fraction of premaligant and malignant lesions. In this study, we were able to inhibit tumor development by oral gene transfer, using adenoviral or adenoassociated viral vectors expressing the human FHIT gene, in heterozygous Fhit(+/-) knockout mice, that are prone to tumor development after carcinogen exposure. We therefore suggest that FHIT gene therapy could be a novel clinical approach not only in treatment of early stages of cancer, but also in prevention of human cancer.

Retinol binding protein expression is induced in HepG2 cells by zinc deficiency

Zinc (Zn) deficiency is often associated with low plasma vitamin A (retinol) concentrations. It has been suggested that the reduction in plasma retinol is secondary to reduced liver retinol binding protein (RBP) synthesis. In the present study, RBP expression was determined in HepG2 cells cultured in either Zn adequate media or chelated media containing varying concentrations of Zn. Levels of RBP mRNA increased in a time- and Zn concentration-dependent manner such that 0.5 microM Zn-treated cells exhibited a >7.5-fold increase while cells treated with 15 microM Zn were increased 2.9-fold at 72 h compared to controls. RBP protein also progressively increased by 72 h to levels >8-fold and 3-fold higher than controls, in 0.5 microM and 15 microM Zn-treated cells, respectively. The increase in RBP occurred without any change in DNA concentration between groups through 72 h. The Zn deficiency-induced elevations in RBP transcript levels could be reversed within 24-48 h of repletion in Zn adequate media. Thus, the reductions in plasma retinol observed in Zn deficiency are in part a direct consequence of the deficiency.

Chemopreventive effect of curcumin on N-nitrosomethylbenzylamine-induced esophageal carcinogenesis in rats

Modifying effects of curcumin (derived from the rhizome of Curcuma longa L.) during the initiation or post-initiation phase of N-nitrosomethylbenzylamine (NMBA)-induced esophageal carcinogenesis were investigated in male F344 rats. Five-week-old rats were divided into 5 groups, and groups 1, 2 and 3 were given intraperitoneal injections of NMBA (0.5 mg / kg body weight / injection 15 times) for 5 weeks from 7 weeks old to induce esophageal neoplasms. Groups 2 and 3 were fed the diet containing 500 ppm curcumin during the initiation and post-initiation phases, respectively. Group 4 was given the diet containing curcumin throughout the experiment, and group 5 was kept on the basal diet alone and served as an untreated control. Incidence and multiplicity of esophageal neoplasms of group 1 (NMBA alone) were 66.7% and 0.83 +/- 0.70, respectively. Those of groups 2 and 3 were significantly less than those of group 1 (39.3%, 0.46 +/- 0.64, P < 0.05; 33.3%, 0.36 +/- 0.56, P < 0.05, respectively). Furthermore, the incidence and multiplicity of esophageal preneoplastic lesions (moderate or severe epithelial dysplasia) of group 2 (57.1%, 0.61 +/- 0.57; 40%, 0.29 +/- 0.46) or 3 (56.7%, 0.67 +/- 0.66; 23.3%, 0.23 +/- 0.43) were less than those of group 1 (100%, 1.67 +/- 0.70; 70.8%, 0.92 +/- 0.72) (P < 0.05). In this experiment, feeding of curcumin significantly decreased the expression of cell proliferation biomarkers (5-bromo-2'-deoxyuridine labeling index) in the non-lesional esophageal epithelium (P < 0.01). These findings indicate that curcumin inhibits NMBA-induced esophageal carcinogenesis when given during the post initiation as well as initiation phase. This inhibition may be related to suppression of the increased cell proliferation induced by NMBA in the esophageal epithelium.

Muir-Torre-like syndrome in Fhit-deficient mice

To investigate the role of the Fhit gene in carcinogen induction of neoplasia, we have inactivated one Fhit allele in mouse embryonic stem cells and produced (129/SvJ x C57BL/6J) F(1) mice with a Fhit allele inactivated (+/-). Fhit +/+ and +/- mice were treated intragastrically with nitrosomethylbenzylamine and observed for 10 wk posttreatment. A total of 25% of the +/+ mice developed adenoma or papilloma of the forestomach, whereas 100% of the +/- mice developed multiple tumors that were a mixture of adenomas, squamous papillomas, invasive carcinomas of the forestomach, as well as tumors of sebaceous glands. The visceral and sebaceous tumors, which lacked Fhit protein, were similar to those characteristic of Muir-Torre familial cancer syndrome.