Oxidative stress and cancer: have we moved forward?

Oxidative stress, DNA methylation and carcinogenesis

Transformation of a normal cell to a malignant one requires phenotypic changes often associated with each of the initiation, promotion and progression phases of the carcinogenic process. Genes in each of these phases acquire alterations in their transcriptional activity that are associated either with hypermethylation-induced transcriptional repression (in the case of tumor suppressor genes) or hypomethylation-induced activation (in the case of oncogenes). Growing evidence supports a role of ROS-induced generation of oxidative stress in these epigenetic processes and as such we can hypothesize of potential mode(s) of action by which oxidative stress modulates epigenetic regulation of gene expression. This is of outmost importance given that various components of the epigenetic pathway and primarily aberrant DNA methylation patterns are used as potential biomarkers for cancer diagnosis and prognosis.

Reactive species: a cell damaging rout assisting to chemical carcinogens

Reactive oxygen and nitrogen species (ROS and RNS) are known to contribute as pathogenic factors to the development of chronic progressive diseases at various stages. The present review discusses the role of oxidative stress in chemically induced cancer development and progression. Reactive species are capable of inducing DNA damage that eventually may contribute to cell transformation and tumor initiation. ROS and RNS are also associated with tumor promotion and progression. Both endogenous processes and redox-cycling of xenobiotic compounds have been shown to result in oxidative DNA damage. In addition, several exocyclic DNA adducts represent secondary DNA damage caused by products of lipid peroxidation in the course of oxidative cellular stress. Due to their intrinsic ability to catalyze redox reactions, transition metals, and quinones from various classes of xenobiotics or endogenous compounds are important mediators of oxidative stress and thus likely of being involved in DNA damage, lipid peroxidation, cell transformation, and tumor development.

A nested case-control study of stomach cancer incidence and serum superoxide dismutase activity in the Japan Collaborative Cohort study in Japan

BACKGROUND

We conducted a nested case-control study to investigate the association between serum levels of superoxide dismutase (SOD) enzyme and the incidence of stomach cancer.

METHODS

A nested case-control study was established within the Japan Collaborative Cohort Study. The follow-up period was from 1988 through 1997. Newly diagnosed cases of stomach cancer were recorded in 804 subjects, of these sera were available for 161 cases. Each of these cases was matched on study area, gender and baseline age with two controls; giving 161 stomach cancer cases and 314 control subjects for analysis. Serum levels of SODs were divided into quartiles, with the first quartile used as the reference. Odds ratios (ORs) and 95% confidence interval (95% CI) for the other serum level quartiles were estimated using the conditional logistic model.

RESULTS

The adjusted ORs and 95% CI for the second, third, and fourth SOD quartiles were 0.71 (95% CI: 0.42-1.19), 0.59 (95% CI: 0.32-1.10), and 0.86 (95% CI: 0.48-1.54), respectively.

CONCLUSION

We found no association between SOD serum level and the risk of stomach cancer. The role of SOD in the development of stomach cancer requires further investigation.

Genetic aspects of inflammation and cancer

Chronic inflammation is involved in the pathogenesis of most common cancers. The aetiology of the inflammation is varied and includes microbial, chemical and physical agents. The chronically inflamed milieu is awash with pro-inflammatory cytokines and is characterized by the activation of signalling pathways that cross-talk between inflammation and carcinogenesis. Many of the factors involved in chronic inflammation play a dual role in the process, promoting neoplastic progression but also facilitating cancer prevention. A comprehensive understanding of the molecular and cellular inflammatory mechanisms involved is vital for developing preventive and therapeutic strategies against cancer. The purpose of the present review is to evaluate the mechanistic pathways that underlie chronic inflammation and cancer with particular emphasis on the role of host genetic factors that increase the risk of carcinogenesis.

Endoplasmic reticulum stress and unfolded protein response in Atm-deficient thymocytes and thymic lymphoma cells are attributable to oxidative stress

Both oxidative stress and endoplasmic reticulum (ER) stress have been implicated in carcinogenesis. It is well documented that cells deficient in the ataxia-telangiectasia mutated (ATM) gene undergo oxidative stress, which is critically involved in thymic lymphomagenesis in Atm-/- mice. Here we demonstrate that undifferentiated Atm-/- thymocytes show signs of ER stress and of the unfolded protein response (UPR). Using two-dimensional (2-D) gel electrophoresis and mass spectrometry (MS) analysis, we identified 22 differentially expressed proteins, including the ER stress marker glucose-regulated protein 78 (GRP78), in Atm-/- thymocytes and in Atm-/- thymic lymphoma cells relative to Atm+/+ thymocytes. The phosphorylated alpha subunit of eukaryotic translation initiation factor 2 (p-eIF2alpha), a UPR marker, was also increased in Atm-/- thymocytes. Cells of the ATL-1 line, which were derived from an Atm-/- mouse thymic lymphoma, were more sensitive to the ER stress inducer tunicamycin than were Atm+/+ thymic leukemia ASL-1 cells. Notably, treatment with hydrogen peroxide duplicated the effects of ATM deficiency in cultured thymocytes, and treatment with the novel cell-permeable thiol antioxidant N-acetylcysteine amide (AD4) reduced elevated p-eIF2alpha levels in thymocytes of Atm-/- mice. Thus, we propose that ER stress and the UPR are secondary to oxidative stress in Atm-/- thymocytes.

PGAM5 tethers a ternary complex containing Keap1 and Nrf2 to mitochondria

Eukaryote cells balance production of reactive oxygen species (ROS) with levels of anti-oxidant enzyme activity to maintain cellular redox homeostasis. Mitochondria are a major source of ROS, while many anti-oxidant genes are regulated by the Nrf2 transcription factor. Keap1, a redox-regulated substrate adaptor for a cullin-based ubiquitin ligase, targets Nrf2 for proteosome-mediated degradation and represses Nrf2-dependent gene expression. We have previously identified a member of the phosphoglycerate mutase family, PGAM5, as a Keap1-binding protein. In this report, we demonstrate that PGAM5 is targeted to the outer membrane of mitochondria by an N-terminal mitochondrial-localization sequence. Furthermore, we provide evidence that PGAM5 forms a ternary complex containing both Keap1 and Nrf2, in which the dimeric Keap1 protein simultaneously binds both PGAM5 and Nrf2 through their conserved E(S/T)GE motifs. Knockdown of either Keap1 or PGAM5 activates Nrf2-dependent gene expression. We suggest that this ternary complex provides a molecular framework for understanding how nuclear anti-oxidant gene expression is regulated in response to changes in mitochondrial function(s).

Leukocyte telomere length predicts cancer risk in Barrett's esophagus

PURPOSE

Leukocyte telomere length has gained attention as a marker of oxidative damage and age-related diseases, including cancer. We hypothesize that leukocyte telomere length might be able to predict future risk of cancer and examined this in a cohort of patients with Barrett's esophagus, who are at increased risk of esophageal adenocarcinoma and thus were enrolled in a long-term cancer surveillance program.

PATIENTS AND METHODS

In this prospective study, telomere length was measured by quantitative PCR in baseline blood samples in a cohort of 300 patients with Barrett's esophagus followed for a mean of 5.8 years. Leukocyte telomere length hazard ratios (HR) for risk of esophageal adenocarcinoma were calculated using multivariate Cox models.

RESULTS

Shorter telomeres were associated with increased esophageal adenocarcinoma risk (age-adjusted HR between top and bottom quartiles of telomere length, 3.45; 95% confidence interval, 1.35-8.78; P = 0.009). This association was still significant when individually or simultaneously adjusted for age, gender, nonsteroidal anti-inflammatory drug (NSAID) use, cigarette smoking, and waist-to-hip ratio (HR, 4.18; 95% confidence interval, 1.60-10.94; P = 0.004). The relationship between telomere length and cancer risk was particularly strong among NSAID nonusers, ever smokers, and patients with low waist-to-hip ratio.

CONCLUSION

Leukocyte telomere length predicts risk of esophageal adenocarcinoma in patients with Barrett's esophagus independently of smoking, obesity, and NSAID use. These results show the ability of leukocyte telomere length to predict the risk of future cancer and suggest that it might also have predictive value in other cancers arising in a setting of chronic inflammation.

Oxidative stress in endometrial hyperplasia

OBJECTIVE

Reactive oxygen species seem to be involved in the onset and promotion of carcinogenesis. In 80% of cases of endometrial adenocarcinoma type I, a clear association exists with endometrial hyperplasia, which is considered a key factor in the endometrial oncological spectrum. The presence or absence of atypical cells determines oncological potential. This study explored the behavior of oxidative stress (catalase and malondialdehyde) in endometrial hyperplasia (with or without atypical cells) by comparing it with the oxidative stress existing in both the proliferative and secretory phases.

DESIGN

Endometrial specimens from 55 women were used, 32 of which were histologically diagnosed as physiological (17 proliferative and 15 secretory endometria) and 23 as endometrial hyperplasia (18 nonatypical and 5 atypical endometrial hyperplasia).

RESULTS

Significant differences were found in the malondialdehyde variable between the proliferative endometrium and the endometrium with atypical hyperplasia (P = 0.0208) and between both types of endometrial hyperplasia (P = 0.0441). The other comparisons were not statistically significant. No changes in catalase activity were observed.

CONCLUSION

Our findings seem to suggest that the presence of atypical cells in endometrial hyperplasia induces a reduction in lipid peroxidation, which could permit survival and growth of these cells. This possible decrease in lipid peroxidation does not seem to be mediated by an increase in endometrial catalase activity.

Biochemistry of oxidative stress

The terms 'antioxidant', 'oxidative stress' and 'oxidative damage' are widely used but rarely defined. This brief review attempts to define them and to examine the ways in which oxidative stress and oxidative damage can affect cell behaviour both in vivo and in cell culture, using cancer as an example.

Induction of oxidative stress as a mechanism of action of chemopreventive agents against cancer

Prevention is a promising option for the control of cancer. Cellular redox changes have emerged as a pivotal and proximal event in cancer. In this review, we provide a brief background on redox biochemistry, discuss the important distinction between redox signalling and oxidative stress, and outline the ‘multiple biological personalities’ of reactive oxygen and nitrogen species: at low concentrations they protect the cell; at higher concentrations they can damage many biological molecules, such as DNA, proteins, and lipids; and, as we argue here, they may also prevent cancer by initiating the death of the transformed cell. Nitric oxide-donating aspirin is discussed as an instructive example: it generates a state of oxidative stress through which it affects several redox-sensitive signalling pathways, leading ultimately to the elimination of the neoplastic cell via apoptosis or necrosis. As additional examples, we discuss the chemopreventive n–3 polyunsaturated fatty acids and conventional nonsteroidal anti-inflammatory drugs, which induce cell death through redox changes. We conclude that modulation of redox biochemistry represents a fruitful approach to cancer prevention.

[Oxidative stress and atherosclerosis]

Oxidative stress is a continuous level of oxidative damage in animal cells, which is caused by an overabundance of reactive oxygen species or a decline in antioxidant ability against them. Oxidative stress increases with individual risk factors of atherosclerosis such as obesity, hypertension, hyperlipidemia, diabetes and smoking. Thus, oxidative stress is considered to play a key role in the pathogenesis of atherosclerosis. This review discusses the relationship between oxidative stress and atherosclerosis based on findings from our research group. We have found that atherosclerotic lesions are formed in the aorta of mice fed a high-cholesterol and high-linoleic diet, in parallel with elevated serum lipid peroxide levels. This model is useful for primary screening of antiatherosclerotic agents with antioxidative activity. One notable factor in the development of atherosclerosis is oxidized low-density lipoprotein (OxLDL). In order to examine OxLDL levels in blood, we have developed anion-exchange HPLC methods using stepwise elution. Using these methods, we have found that OxLDL markedly increases in a rat model of metabolic syndrome, in animals exposed to cigarette smoke and in smokers in parallel with other oxidative stress markers. These oxidative stress markers have been attenuated by administration of several antioxidants. In addition, we have found that smoking accelerates atherogenesis in the aorta of apoE-deficient mice and this acceleration can be ameliorated by administration of vitamin E. These observations suggest that antioxidant supplementation may be an effective therapeutic strategy for metabolic syndrome and smoking-induced diseases in which elevated oxidative stress plays a pivotal role.

Overexpression of human NOX1 complex induces genome instability in mammalian cells

The production of reactive oxygen species (ROS) in mammalian cells is tightly regulated because of their potential to damage macromolecules, including DNA. To investigate possible links between high ROS levels, oxidative DNA damage, and genomic instability in mammalian cells, we established a novel model of chronic oxidative stress by coexpressing the NADPH oxidase human (h) NOX1 gene together with its cofactors NOXO1 and NOXA1. Transfectants of mismatch repair (MMR)-proficient HeLa cells or MMR-defective Msh2(-/-) mouse embryo fibroblasts overexpressing the hNOX1 complex displayed increased intracellular ROS levels. In one HeLa clone in which ROS were particularly elevated, reactive nitrogen species were also increased and nitrated proteins were identified with an anti-3-nitrotyrosine antibody. Overexpression of the hNOX1 complex increased the steady-state levels of DNA 8-oxo-7,8-dihydroguanine and caused a threefold increase in the HPRT mutation rate in HeLa cells. In contrast, additional oxidatively generated damage did not affect the constitutive mutator phenotype of the Msh2(-/-) fibroblasts. Because no significant changes in the expression of several DNA repair enzymes for oxidative DNA damage were identified, we suggest that chronic oxidative stress can saturate the cell's DNA repair capacity and cause significant genomic instability.

A fluorescent probe for the detection of myeloperoxidase activity in atherosclerosis-associated macrophages

The myeloperoxidase (MPO)-derived oxidant hypochlorous acid (HOCl/OCl(-)) is implicated in the pathogenesis of atherosclerosis and other inflammatory states. We have synthesized an imaging probe, sulfonaphthoaminophenyl fluorescein (SNAPF), that selectively reacts with HOCl. SNAPF detects HOCl produced by stimulated MPO-expressing cells cultured from human whole blood, as well as HOCl from bone marrow (BM)-derived macrophages isolated from transgenic mice that express human MPO. Two lines of evidence indicate that SNAPF permits the in vivo imaging of HOCl production. First, we used this approach to demonstrate HOCl production by neutrophils in experimental murine peritonitis. Second, we detected HOCl production by MPO expressing cells in human atherosclerotic arteries. Thus, fluorescence reflectance imaging by SNAPF may provide a valuable noninvasive molecular imaging tool for implicating HOCl and MPO in the damage of inflamed tissues.

Phorbol ester and hydrogen peroxide synergistically induce the interaction of diacylglycerol kinase gamma with the Src homology 2 and C1 domains of beta2-chimaerin

DGKgamma (diacylglycerol kinase gamma) was reported to interact with beta2-chimaerin, a GAP (GTPase-activating protein) for Rac, in response to epidermal growth factor. Here we found that PMA and H2O2 also induced the interaction of DGKgamma with beta2-chimaerin. It is noteworthy that simultaneous addition of PMA and H2O2 synergistically enhanced the interaction. In this case, PMA was replaceable by DAG (diacylglycerol). The beta2-chimaerin translocation from the cytoplasm to the plasma membrane caused by PMA plus H2O2 was further enhanced by the expression of DGKgamma. Moreover, DGKgamma apparently enhanced the beta2-chimaerin GAP activity upon cell stimulation with PMA. PMA was found to be mainly required for a conversion of beta2-chimaerin into an active form. On the other hand, H2O2 was suggested to induce a release of Zn2+ from the C1 domain of beta2-chimaerin. By stepwise deletion analysis, we demonstrated that the SH2 (Src homology 2) and C1 domains of beta2-chimaerin interacted with the N-terminal half of catalytic region of DGKgamma. Unexpectedly, the SH2 domain of beta2-chimaerin contributes to the interaction independently of phosphotyrosine. Taken together, these results suggest that the functional link between DGKgamma and beta2-chimaerin has a broad significance in response to a wide range of cell stimuli. Our work offers a novel mechanism of protein-protein interaction, that is, the phosphotyrosine-independent interaction of the SH2 domain acting in co-operation with the C1 domain.

Mitochondrial DNA damage triggers mitochondrial-superoxide generation and apoptosis

Recently, it has become apparent that mitochondrial DNA (mtDNA) damage can rapidly initiate apoptosis independent of mutations, although the mechanism involved remains unclear. To elucidate this mechanism, angiotensin II-mediated apoptosis was studied in cells that were transduced with a lentiviral vector to overexpress the DNA repair enzyme 8-oxoguanine glycosylase or were treated with inhibitors known to block angiotensin II-induced mtDNA damage. Cells exhibiting angiotensin II-induced mtDNA damage showed two phases of superoxide generation, the first derived from NAD(P)H oxidase and the second of mitochondrial origin, whereas cells prevented from experiencing mtDNA damage importantly exhibited only the first phase. Furthermore, cells with mtDNA damage demonstrated impairments in mitochondrial protein expression, cellular respiration, and complex 1 activity before the onset of the second phase of oxidation. After the second phase, the mitochondrial membrane potential collapsed, cytochrome c was released, and the cells underwent apoptosis, all of which were prevented by disrupting mtDNA damage. Collectively, these data reveal a novel mechanism of apoptosis that is initiated when mtDNA damage triggers mitochondrial superoxide generation and ultimately the activation of the mitochondrial permeability transition. This novel mechanism may play an important pathological role.

Superoxide dismutase enhanced the formation of hydroxyl radicals in a reaction mixture containing xanthone under UVA irradiation

To clarify the effect of superoxide dismutase (SOD) on the formation of hydroxyl radical in a standard reaction mixture containing 15 microM of xanthone, 0.1 M of 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and 45 mM of phosphate buffer (pH 7.4) under UVA irradiation, electron paramagnetic resonance (EPR) measurements were performed. SOD enhanced the formation of hydroxyl radicals. The formation of hydroxyl radicals was inhibited on the addition of catalase. The rate of hydroxyl radical formation also slowed down under a reduced oxygen concentration, whereas it was stimulated by disodium ethylenediaminetetraacetate (EDTA) and diethyleneaminepentaacetic acid (DETAPAC). Above findings suggest that O(2), H(2)O(2), and iron ions participate in the reaction. SOD possibly enhances the formation of the hydroxyl radical in reaction mixtures of photosensitizers that can produce O(2)(-.).

Design and synthesis of manganese porphyrins with tailored lipophilicity: investigation of redox properties and superoxide dismutase activity

Thirteen new manganese porphyrins and two porphodimethenes bearing one to three different substituents at the meso positions in a variety of architectures have been synthesized. The substituents employed generally are (i) electron-withdrawing to tune the reduction potential to the desirable range (near +0.3V vs NHE), and/or (ii) lipophilic to target the interior of lipid bilayer membranes and/or the blood-brain barrier. The influence of the substituents on the Mn(III)/Mn(II) reduction potentials has been characterized, and the superoxide dismutase activity of the compounds has been examined.

Markers of oxidative stress in ICU clinical settings: present and future

PURPOSE OF REVIEW

Oxidative stress is associated with most conditions requiring intensive care: it contributes to clinical complications, organ failure and mortality. Interestingly, no unique definition exists of oxidative stress, of how it contributes to the clinical worsening and most importantly, no common strategy exists about its measurement. Despite these metrology problems, limiting the intensity of oxidative stress has become a popular therapeutic target. The paper reviews methods used to determine oxidative stress in clinical situations using routine validated methods or those used by research laboratories.

RECENT FINDINGS

Many methods of measuring oxidative stress have proven unreliable and no single method exists enabling objective determination and characterization of oxidative stress in clinical settings whether in critical illness or in chronic disease. Some methods, like determination of malondialdehyde, F2-isoprostanes, or 8-hydroxydesoxyguanosine, are widely used to determine oxidative stress. Other methods - such as the determination of vitamins or micronutrients - are able to determine components of the antioxidant defense. No single method, however, is yet alone able to characterize oxidative stress under clinical conditions.

SUMMARY

Today, strategies to measure oxidative stress are limited in clinical settings. The most reliable available marker remains malondialdehyde or F2-isoprostanes, in combination with circulating levels of micronutrients.

Carotenóides: uma possível proteção contra o desenvolvimento de câncer

Este artigo discute as possibilidades de proteção contra o desenvolvimento do câncer, proporcionadas por carotenóides provenientes da alimentação, com base em uma revisão da literatura. Os carotenóides têm demonstrado uma ação protetora contra a carcinogênese, tanto em estudos in vitro como in vivo, com animais e humanos. Entre eles, a beta-criptoxantina, a fucoxantina, a astaxantina, a capsantina, a crocetina e o fitoeno, têm sido pouco explorados, e a literatura ainda se mostra extremamente limitada e pouco conclusiva. Estudos experimentais com humanos demonstraram não haver efeito, ou efeito reverso, do beta-caroteno, no entanto, não incluíram anteriormente variáveis intervenientes e interativas que deveriam ter sido controladas. A partir da evidência científica, baseada em estudos epidemiológicos e ensaios experimentais recentes, e da elucidação dos mecanismos de atuação de fitoquímicos relacionados à maior proteção contra o câncer, conclui-se que a alimentação rica em carotenóides provenientes das frutas, legumes e verduras, representa um possível fator de proteção contra o desenvolvimento do câncer.

Pyruvate reduces DNA damage during hypoxia and after reoxygenation in hepatocellular carcinoma cells

Pyruvate is located at a crucial crossroad of cellular metabolism between the aerobic and anaerobic pathways. Modulation of the fate of pyruvate, in one direction or another, can be important for adaptative response to hypoxia followed by reoxygenation. This could alter functioning of the antioxidant system and have protective effects against DNA damage induced by such stress. Transient hypoxia and alterations of pyruvate metabolism are observed in tumors. This could be advantageous for cancer cells in such stressful conditions. However, the effect of pyruvate in tumor cells is poorly documented during hypoxia/reoxygenation. In this study, we showed that cells had a greater need for pyruvate during hypoxia. Pyruvate decreased the number of DNA breaks, and might favor DNA repair. We demonstrated that pyruvate was a precursor for the biosynthesis of glutathione through oxidative metabolism in HepG2 cells. Therefore, glutathione decreased during hypoxia, but was restored after reoxygenation. Pyruvate had beneficial effects on glutathione depletion and DNA breaks induced after reoxygenation. Our results provide more evidence that the alpha-keto acid promotes the adaptive response to hypoxia followed by reoxygenation. Pyruvate might thus help to protect cancer cells under such stressful conditions, which might be harmful for patients with tumors.

Targeting mitochondria in the treatment of human cancer: a coordinated attack against cancer cell energy metabolism and signalling

Mitochondria have major roles in bioenergetics and vital signalling of the mammalian cell. Consequently, these organelles have been implicated in the process of carcinogenesis, which includes alterations of cellular metabolism and cell death pathways. Multiple molecular routes of malignant transformation appear to result in the common ability of many tumours to take up large amounts of glucose. This metabolic twist has been explained by phenomena such as aerobic glycolysis and impaired mitochondrial function, and is linked to tumour growth potential via major cellular signalling pathways. This paper reviews the literature on central mechanisms through which energy metabolism merges with growth, proliferation and death signalling, which tend to include mitochondria at some level. These processes can potentially be targeted by pharmacological agents for therapeutic and chemosensitising purposes.

Repetitive tissue pO2 measurements by electron paramagnetic resonance oximetry: current status and future potential for experimental and clinical studies

Tissue oxygen plays a crucial role in maintaining tissue viability and in various diseases, including responses to therapy. Useful knowledge has been gained by methods that can give limited snapshots of tissue oxygen (e.g., oxygen electrodes) or evidence of a history of tissue hypoxia (e.g., EF5) or even indirect evidence by monitoring oxygen availability in the circulatory system (e.g., NMR methods). Each of these methods has advantages and significant limitations. EPR oximetry is a technique for direct measurement of tissue pO2, which has several advantages over the other existing methods for applications in which the parameter of interest is the pO2 of tissues, and information is needed over a time course of minutes to hours, and/or for repetitive measurements over days or weeks or years. The aim of this article is to provide an overview of EPR oximetry using particulates to readers who are not familiar with this technique and its potential in vivo and clinical applications. The data presented here are from the experiments currently being carried out in our laboratory. We are confident that in vivo EPR oximetry will play a crucial role in the understanding and clinical management of various pathologies in the years to come.

MAPK activation by radio waves

In this issue of the Biochemical Journal, Freidman et al. report the findings of a study to look at the potential of mobile phones to activate intracellular signalling cascades. They found that radio waves corresponding to the frequency commonly used by mobile phones are able to activate ERK1/2 (extracellular-signal-regulated kinases 1 and 2). This effect was observed even at intensities lower than those emitted by mobile phones that are unable to cause any measurable heating effects. This study provides evidence that radio waves induce ERK1/2 activation downstream of the EGF (epidermal growth factor) receptor, which is in turn activated by the release of reactive oxygen species.

Carcinogenesis of Helicobacter pylori

Helicobacter infection is the leading cause of gastric cancer worldwide. Infection with this ubiquitous bacterium incites a chronic active immune response that persists for the life of the host, in the absence of antibiotic-induced eradication. It is the combination of bacterial factors, environmental insults, and the host immune response that drives the initiation and progression of mucosal atrophy, metaplasia, and dysplasia toward gastric cancer. Although it may seem intuitively obvious that removing the offending organism would negate the cancer risk, this approach is neither feasible (half of the world harbors this infection) nor is it straightforward. Most patients are infected in childhood, and present with various degrees of mucosal damage before any therapy. This review outlines the histologic progression of human Helicobacter infection from the early stages of inflammation through the development of metaplasia, dysplasia, and, finally, cancer. The effects of dietary and bacterial eradication therapy on disease progression and lesion reversibility are reviewed within the context of population studies and compared between study designs and populations tested. Eradication studies in the mouse model of infection prevents the formation of gastric cancer, and allows regression of established lesions, providing a useful model to study interaction between bacterium, environment, and host, without the difficulties inherent in human population studies. Recent advances in identifying the bone marrow-derived stem cell as the cell of origin of Helicobacter-induced gastric cancer in the murine model are discussed and interpreted in the context of human disease, and implications for future treatment are discussed.

Characterization of redox state of two human prostate carcinoma cell lines with different degrees of aggressiveness

We characterized the redox profiles in two different human prostate carcinoma cell lines (LNCaP vs PC3) that are known to exhibit varying degrees of invasiveness/metastatic ability. We confirmed that PC3 cells were more invasive than LNCaP cells through an in vitro analysis. The present study documented higher 8-hydroxy-2'-deoxyguanosine levels in PC3 cells than in LNCaP cells. The levels of lipid peroxidation were higher in LNCaP cells than in PC3 cells. The reduced glutathione (GSH)/glutathione disulfide (GSSG) ratio increased to a greater extent during cell growth in PC3 cells than in LNCaP cells, whereas both reduced GSH and GSSG levels were higher in the medium of PC3 cells than in that of LNCaP cells. The levels of reactive oxygen (ROS) and reactive nitrogen species (RNS), both intracellularly and in the medium, were higher for LNCaP cells than for PC3 cells during cell growth. In addition, our results demonstrated higher ROS/RNS levels in LNCaP cells than in PC3 cells in S and G(2)/M phases of the cell cycle during logarithmic growth. Each cell type showed distinct cytotoxic responses to low-molecular-weight redox-modulating compounds. Our results document that human prostate cancer cell lines of varying degrees of aggressive behavior have distinct redox properties, findings that could lead to novel therapeutic interventions.

p53: new roles in metabolism

Virtually all cancers show metabolic changes that result in upregulation of glycolysis and glucose consumption. Although discovered in the 1920s, how this glycolytic switch happens, and whether it is a cause or a consequence of the malignant process, has remained a matter of debate. The p53 tumor suppressor gene, discovered some 30 years ago, has a key role in preventing cancer development. Recent discoveries revealing new functions for p53 in the regulation of glucose metabolism and oxidative stress have brought together these two venerable fields of cancer biology. These activities of p53 appear to be key in tumor suppression, and shed some light on the pathways that underlie the metabolic changes in cancer cells.

Molecular mechanisms of euplotin C-induced apoptosis: involvement of mitochondrial dysfunction, oxidative stress and proteases

The metabolite euplotin C (EC), isolated from the marine ciliate Euplotes crassus, is a powerful cytotoxic and pro-apoptotic agent in tumour cell lines. For instance, EC induces the rapid depletion of ryanodine Ca(2+) stores, the release of cytochrome c from the mitochondria, and the activation of caspase-3, leading to apoptosis. The purpose of this study was to gain further insight into the mechanisms of EC-induced apoptosis in rat pheochromocytoma PC12 cells. We found that EC increases Bax/Bcl-2 ratio and that Bax is responsible of the EC-induced dissipation of the mitochondrial membrane potential (Deltapsi(m)). In addition, EC induces the generation of reactive oxygene species (ROS) without involvement of p53. The inhibition of ROS generation prevents, at least in part, the pro-apoptotic effects of EC as well as the effects of EC on Bax, Deltapsi(m) and intracellular free Ca(2+), indicating a cross-talk between different pathways. However, definition of the effector cascade turns out to be more complex than expected and caspase-independent mechanisms, acting in parallel with caspases, should also be considered. Among them, EC increases the expression/activity of calpains downstream of ROS generation, although calpains seem to exert protective effects.