Effect of combinations of antioxidants on phagocyte-induced sister-chromatid exchanges

The crosstalk between glucose metabolism and telomerase regulation in cancer

Accumulated alterations in metabolic control provide energy and anabolic demands for enhanced cancer cell proliferation. Exemplified by the Warburg effect, changes in glucose metabolism during cancer progression are widely recognized as a characteristic of metabolic disorders. Since telomerases are a vital factor in maintaining DNA integrity and stability, any damage threatening telomerases could have a severe impact on DNA and, subsequently, whole-cell homeostasis. However, it remains unclear whether the regulation of glucose metabolism in cancer is connected to the regulation of telomerase. In this review, we present the latest insights into the crosstalk between telomerase function and glucose metabolism in cancer cells. However, at this moment this subject is not well investigated that the association is mostly indirectly regulations and few explicit regulating pathways were identified between telomerase and glucose metabolism. Therefore, the information presented in this review can provide a scientific basis for further research on the detail mechanism and the clinical application of cancer therapy, which could be valuable in improving the effectiveness of chemotherapy.

Schistosomiasis and cancer in egypt: review

Schistosomiasis is not known to be associated with any malignant disease other than bladder cancer. Bladder cancer is still the most common malignant tumor among males in Egypt and some African and Middle East countries. However, the frequency rate of bladder cancer has declined significantly during the last 25 years. This drop is mainly related to the control of Schistosomiasis. Many studies have elucidated the pathogenic events of Schistosomal-related bladder cancer with a suggested theory of pathogenesis. Furthermore, the disease presents with a distinct clinicopathologic profile that is quite different from bladder cancer elsewhere with younger age at presentation, more male predominance, more invasive stages, and occurrence of squamous cell carcinoma pathologic subtype. However, recent data suggest that this profile has been dramatically changed over the past 25 years leading to minimization of the differences between its features in Egypt and that in Western countries. Management of muscle-invasive localized disease is mainly surgery with 5-year survival rates of 30-50%. Although still a debatable issue, adjuvant and neoadjuvant chemotherapy and radiotherapy have improved treatment outcomes including survival and bladder preservation rates in most studies. This controversy emphasizes the need of individualized treatment options based on a prognostic index or other factors that can define the higher risk groups where more aggressive therapy is needed. The treatment for locally advanced and/or metastatic disease has passed through a series of clinical trials since 1970s. These phase II and III trials have included the use of single agent and combination of chemotherapy and radiotherapy regimens. The current standard of systemic chemotherapy of generally fit patients is now the gemcitabine-cisplatin combination. In conclusion, a changing pattern of bladder cancer in Egypt is clearly observed. This is mainly due to the success in the control of Schistosomiasis. It may also be due to increased exposure to other etiologic factors that include smoking, pesticides, and/or other causative agents. This change will ultimately affect disease management.

Oxidative stress, inflammation, and cancer: how are they linked?

Extensive research during the past 2 decades has revealed the mechanism by which continued oxidative stress can lead to chronic inflammation, which in turn could mediate most chronic diseases including cancer, diabetes, and cardiovascular, neurological, and pulmonary diseases. Oxidative stress can activate a variety of transcription factors including NF-κB, AP-1, p53, HIF-1α, PPAR-γ, β-catenin/Wnt, and Nrf2. Activation of these transcription factors can lead to the expression of over 500 different genes, including those for growth factors, inflammatory cytokines, chemokines, cell cycle regulatory molecules, and anti-inflammatory molecules. How oxidative stress activates inflammatory pathways leading to transformation of a normal cell to tumor cell, tumor cell survival, proliferation, chemoresistance, radioresistance, invasion, angiogenesis, and stem cell survival is the focus of this review. Overall, observations to date suggest that oxidative stress, chronic inflammation, and cancer are closely linked.

Heat-shock proteins in infection-mediated inflammation-induced tumorigenesis

Inflammation is a necessary albeit insufficient component of tumorigenesis in some cancers. Infectious agents directly implicated in tumorigenesis have been shown to induce inflammation. This process involves both the innate and adaptive components of the immune system which contribute to tumor angiogenesis, tumor tolerance and metastatic properties of neoplasms. Recently, heat-shock proteins have been identified as mediators of this inflammatory process and thus may provide a link between infection-mediated inflammation and subsequent cancer development. In this review, the role of heat-shock proteins in infection-induced inflammation and carcinogenesis will be discussed.

Cyclooxygenase inhibitory and antioxidant compounds from the fruiting body of an edible mushroom, Agrocybe aegerita

In the search for bioactive natural products from edible mushrooms, we have investigated the fruiting body of Agrocybe aegerita. The methanol extract of this mushroom yielded a fatty acid fraction (FAF), along with palmitic acid (1), ergosterol (2), 5,8-epidioxy-ergosta-6,22-dien-3beta-ol (3), mannitol (4) and trehalose (5). The composition of FAF was confirmed by GC-MS and by comparison to the retention values of authentic samples of palmitic, stearic, oleic and linoleic acids. The structures of 1-5 were established using spectroscopic methods. FAF and compounds 1-3 showed cyclooxygenase (COX) enzyme inhibitory and antioxidant activities. The inhibition values of liposome peroxidation by FAF, compounds 1 and 2 at 100 microg/ml were 75, 45, and 43%, respectively. The inhibition values of COX-I enzyme by FAF and 1-3 at 100 microg/ml were 80, 39, 19, and 57%, respectively. Similarly, COX-II enzyme activity was reduced by FAF and 1-3 at 100 microg/ml with values of 88, 45, 28, and 22%, respectively. Compounds 1, 3 and fatty acids were isolated here for the first time from the fruiting body of A. aegerita.

Antiinflammatory and antioxidant property of saponins of tea [Camellia sinensis (L) O. Kuntze] root extract

Two groups of saponins, TS-1 and TS-2, isolated from tea root extract (TRE) were tested for antiinflammatory and in vitro antioxidant activity. Both TS-1 and TS-2 inhibited carrageenan-induced paw oedema in rats. The antioxidant activity of these compounds was evaluated using the xanthine-xanthine oxidase system. The study indicated that the previously observed antitumour activity of TRE might be mediated through scavenging of free radicals by saponins and their antiinflammatory activity.

Eosinophil peroxidase catalyzes bromination of free nucleosides and double-stranded DNA

Chronic parasitic infections are a major risk factor for cancer development in many underdeveloped countries. Oxidative damage of DNA may provide a mechanism linking these processes. Eosinophil recruitment is a hallmark of parasitic infections and many forms of cancer, and eosinophil peroxidase (EPO), a secreted hemoprotein, plays a central role in oxidant production by these cells. However, mechanisms through which EPO may facilitate DNA oxidation have not been fully characterized. Here, we show that EPO effectively uses plasma levels of bromide as a cosubstrate to brominate bases in nucleotides and double-stranded DNA, forming several stable novel brominated adducts. Products were characterized by HPLC with on-line UV spectroscopy and electrospray ionization tandem mass spectrometry (LC/ESI/MS/MS). Ring assignments for brominated purine bases as their 8-bromo adducts were identified by NMR spectroscopy. Using stable isotope dilution LC/ESI/MS/MS, we show that while guanine is the preferred purine targeted for bromination as a free nucleobase, 8-bromoadenine is the major purine oxidation product generated following exposure of double-stranded DNA to either HOBr or the EPO/H(2)O(2)/Br(-) system. Bromination of nucleobases was inhibited by scavengers of hypohalous acids such as the thioether methionine, but not by a large molar excess of primary amines. Subsequently, N-monobromoamines were demonstrated to be effective brominating agents for both free nucleobases and adenine within intact DNA. A rationale for selective modification of adenine, but not guanine, in double-stranded DNA based upon stereochemical criteria is presented. Collectively, these results suggest that specific brominated DNA bases may serve as novel markers for monitoring oxidative damage of DNA and the nucleotide pool by brominating oxidants.

Activated leukocytes oxidatively damage DNA, RNA, and the nucleotide pool through halide-dependent formation of hydroxyl radical

A variety of chronic inflammatory conditions are associated with an increased risk for the development of cancer. Because of the numerous links between DNA oxidative damage and carcinogenesis, a potential role for leukocyte-generated oxidants in these processes has been suggested. In the present study, we demonstrate a novel free transition metal ion-independent mechanism for hydroxyl radical ((*)OH)-mediated damage of cellular DNA, RNA, and cytosolic nucleotides by activated neutrophils and eosinophils. The mechanism involves reaction of peroxidase-generated hypohalous acid (HOCl or HOBr) with intracellular superoxide (O(2)(*)(-)) forming (*)OH, a reactive oxidant species implicated in carcinogenesis. Incubation of DNA with either isolated myeloperoxidase (MPO) or eosinophil peroxidase (EPO), plasma levels of halides (Cl(-) and Br(-)), and a cell-free O(2)(*)(-) -generating system resulted in DNA oxidative damage. Formation of 8-hydroxyguanine (8-OHG), a mutagenic base which is a marker for (*)OH-mediated DNA damage, required peroxidase and halides and occurred in the presence of transition metal chelators (DTPA +/- desferrioxamine), and was inhibited by catalase, superoxide dismutase (SOD), and scavengers of hypohalous acids. Similarly, exposure of DNA to either neutrophils or eosinophils activated in media containing metal ion chelators resulted in 8-OHG formation through a pathway that was blocked by peroxidase inhibitors, hypohalous acid scavengers, and catalytically active (but not heat-inactivated) catalase and SOD. Formation of 8-OHG in target cells (HA1 fibroblasts) occurred in all guanyl nucleotide-containing pools examined following exposure to both a low continuous flux of HOCl (at sublethal doses, as assessed by [(14)C]adenine release and clonogenic survival), and hyperoxia (to enhance intracellular O(2)(*)(-) levels). Mitochondrial DNA, poly A RNA, and the cytosolic nucleotide pool were the primary targets for oxidation. Moreover, modest but statistically significant increases in the 8-OHG content of nuclear DNA were also noted. These results suggest that the peroxidase-H(2)O(2)-halide system of leukocytes is a potential mechanism contributing to the well-established link between chronic inflammation, DNA damage, and cancer development.

Dysplasia and cancer in the dextran sulfate sodium mouse colitis model. Relevance to colitis-associated neoplasia in the human: a study of histopathology, B-catenin and p53 expression and the role of inflammation

Animal models of colitis, which develop dysplasia and cancer similar to human ulcerative colitis are needed to further investigate the dysplasia cancer sequence. This study describes the expression of B-catenin and p53 along with the histopathology and inflammation scores as they relate to dysplasia and cancer in the dextran sulfate sodium (DSS) colitis model. Swiss Webster mice were fed with 5% DSS as follows: group A, four cycles of DSS, 84 days total (1 cycle = 7 days DSS + 14 days H(2)O); group B, four cycles DSS followed by 120 days H(2)O, 204 days total; group C, 7 days DSS followed by 180 days H(2)O, 187 days total; group D, 7 days DSS followed by 90 days H(2)O, 97 days total. The incidences of dysplasia and/or cancer were 15.8, 37.5, 18.1 and 0% in groups A-D, respectively. Dysplasia and/or cancer occurred as flat lesions or as dysplasia-associated lesion or mass (DALM) as observed in the human. Thirty-three percent of cancers had associated dysplasia. Within group A, inflammation scores were significantly higher in animals with dysplasia and/or cancer compared with those without dysplasia and/or cancer (P < 0. 05-P < 0.0001). Inflammation scores were significantly higher in animals with cancers versus those with dysplasia (P < 0.015) and in flat dysplasia and/or cancer versus DALM (P < 0.0042). B-catenin showed translocation from the cell membrane to the cytoplasm and/or nucleus in 100% of DALM and 5.8% of flat dysplasia and/or cancer. A total of 94.2% of flat dysplasia and/or cancer had exclusive cell membrane expression compared with 0% DALM (P < 0.0001). Only 7.4% of dysplasia and/or cancer showed nuclear expression of p53. In colitis-associated dysplasia and/or cancer in the DSS model: (i) histology resembles that in the human; (ii) inflammation plays a significant role in the dysplasia cancer sequence and whether dysplasia and/or cancer grows as a flat lesion or a DALM; (iii) the early molecular pathways are different for flat dysplasia and/or cancer versus DALM, with nuclear/cytoplasmic translocation of B-catenin as an early event in DALM but not flat dysplasia and/or cancer; and (iv) p53 has little or no role in dysplasia and/or cancer. This well characterized model provides an excellent vehicle for studying the roles of inflammation, the molecular events and the role of chemopreventive agents in colitis-associated neoplasia.

Frequent p53 gene mutations in soft tissue sarcomas arising in burn scar

Squamous cell carcinoma (SCC) is the commonest malignancy that arises in burn scars, which frequently contain p53 mutations. Soft tissue sarcoma (STS) also develops, though less frequently, in burn scars. p53 gene mutations were analyzed in paraffin-embedded specimens from 5 patients with STS (4 males and 1 female) that had arisen in a burn scar, by means of polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) followed by direct sequencing. Age at burn injury ranged from 2 to 10 (median 3) years, and STS developed with a latent period ranging from 29 to 79 (median 60) years. Histologically, all were malignant fibrous histiocytoma. The PCR-SSCP revealed aberrant bands in 4 (80%) of 5 cases. Direct sequencing revealed a total of 11 mutations in these 4 cases: 1 case had a single mutation, 1 had 2 mutations, and 2 had 4 mutations. Every tumor had at least 1 mutation that changed an amino acid, which may have provided the selection pressure for expansion. Thus, there is a high frequency of p53 gene mutations in STS appearing in burn scars. p53 mutations were also frequent in pyothorax-associated lymphoma (PAL), a lymphoma that develops in patients with long-standing pyothorax, so p53 mutations might be frequent in malignancies that develop in chronic inflammatory sites.

Relationship between schistosomiasis and bladder cancer

Carcinoma of the urinary bladder is the most common malignancy in the Middle East and parts of Africa where schistosomiasis is a widespread problem. Much evidence supports the association between schistosomiasis and bladder cancer: this includes the geographical correlation between the two conditions, the distinctive patterns of gender and age at diagnosis, the clinicopathological identity of schistosome-associated bladder cancer, and extensive evidence in experimentally infected animals. Multiple factors have been suggested as causative agents in schistosome-associated bladder carcinogenesis. Of these, N-nitroso compounds appear to be of particular importance since they were found at high levels in the urine of patients with schistosomiasis-associated bladder cancer. Various strains of bacteria that can mediate nitrosation reactions leading to the formation of N-nitrosamines have been identified in the urine of subjects with schistosomiasis at higher intensities of infection than in normal subjects. In experimental schistosomiasis, the activities of carcinogen-metabolizing enzymes are increased soon after infection but are reduced again during the later chronic stages of the disease. Not only could this prolong the period of exposure to activated N-nitrosamines, but also inflammatory cells, stimulated as a result of the infection, may induce the endogenous synthesis of N-nitrosamines as well as generating oxygen radicals. Higher than normal levels of host cell DNA damage are therefore anticipated, and they have indeed been observed in the case of alkylation damage, together with an inefficiency in the capacity of relevant enzymes to repair this damaged DNA. In experimental schistosomiasis, it was also found that endogenous levels of host cell DNA damage were related to the intensity of infection. All of these factors could contribute to an increased risk of bladder cancer in patients with schistosomiasis, and in particular, the gene changes observed may have potential for use as biomarkers in the early detection of bladder cancer that may assist in alleviating the problem.

Multifocal neoplasia involving the colon and appendix in ulcerative colitis: pathological and molecular features

A patient with ulcerative colitis, extensive dysplasia, multifocal colon cancer, and an appendiceal cystadenoma is described. A 48-year-old man with a 26-year history of ulcerative colitis (UC) had extensive dysplasia involving nearly the entire colon and four dysplasia-associated mass lesions (DALMs). Four invasive adenocarcinomas were present. This case is the first documentation of a DALM (mucinous cystadenoma) arising in the appendix in the setting of UC. The genetic alterations present in the various lesions were analyzed. The molecular profiles of the neoplastic lesions differed. Mutations were found in p53 and ras genes, and one site showed microsatellite instability in a single genetic locus. These molecular abnormalities develop before invasive cancer develops, and may undergo clonal expansion to create large mucosal patches containing certain cells with genetic alterations. The diversity of the early changes suggests that the recurrent inflammation characteristic of long-standing UC randomly damages genes known to participate in colon carcinogenesis and that it affects multiple target genes. The findings also support a multiclonal origin of synchronous tumors because the molecular phenotypes of the preinvasive lesions differed at various sites.

Response of fibroblast cultures from ataxia-telangiectasia patients to reactive oxygen species generated during inflammatory reactions

Cells from patients with ataxia-telangiectasia (AT) are more sensitive than cells from normal individuals to a number of compounds which induce DNA damage via oxygen-derived free radical attack. We tested the hypothesis that AT cells would show a sensitivity to reactive oxygen species (ROS) generated by activated inflammatory cells. AT cells were exposed to neutrophils activated with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or to xanthine/xanthine oxidase (X/XO), an enzyme system which generates superoxide and hydrogen peroxide. Induced micronuclei (MN) frequencies (corrected for spontaneous MN frequencies) were significantly higher in AT cell cultures than in cultures from normal individuals (comparison of MN frequencies of AT vs. normal cultures: for treatment with activated neutrophils, P = 0.003; for X/XO, P = 0.05). The comet assay was used to determine whether the elevated chromosomal damage in the treated AT cells was due to a difference in strand breakage or its rejoining. X/XO treatment was used in studies of single-stranded (SS) DNA breakage, and X-ray treatment for double-stranded (DS) DNA damage. AT and normal cells showed no significant differences in the initial levels of SS (P = 0.29) or DS (P = 0.91) DNA damage. Likewise, they exhibited similar rejoining kinetics (rejoining half-time for SS = 10 min, for DS = 30 min). These data support the involvement of the AT loci in determining a cell's ability to deal with oxidative stress, although the mechanism underlying this effect has yet to be resolved. The data also suggest that AT patients are at elevated risk of sustaining DNA damage in tissues undergoing inflammatory reactions.

Peculiarities of the clastogenic properties of chrysotile-asbestos fibers and zeolite particles

It has been established that chrysotile-asbestos fibers and zeolite particles induce chromosome aberrations in human lymphocytes from whole blood cultures, peritoneal fluid cells and bone marrow cells of mice. It is shown that the level of cytogenetic response from the intraperitoneal administration of chrysotile-asbestos fibers and zeolite particles depends on the time of their exposure. Further, it is shown that SOD eliminates the cytogenetic effect of chrysotile-asbestos fibers, while catalase inhibits that of zeolite particles. Recommendations concerning testing for the mutagenic properties of mineral fibers and particles are given, and possible mechanisms of their damaging effects are discussed.

Molecular and biochemical reprogramming of oncogenesis through the activity of prooxidants and antioxidants

The antioxidant alpha-tocopherol and the weaker antioxidant and prooxidant chemopreventative, beta-carotene have been shown to inhibit tumor cell growth in vivo and in vitro. In some epidemiologic studies their serum levels were demonstrated to be inversely related to the incidence of malignant tumor. We hypothesized two basic pathways triggered by antioxidants and prooxidants, which resulted in the control of tumor cell growth. These included changes in phosphorylation and ultimately transcription. Specifically, the prooxidant beta-carotene treatment produced an oxidative stress resulting in the selective induction of heat shock proteins (hsps). These proteins and other proteins that were possibly oxidized were associated with the increased expression of cyclins (A and D) and increased cdc2 kinase expression. An increase in expression of phosphoproteins, such as p53 (tumor suppressor form) was also discerned. The level of expression for the transcription factor c-fos was reduced. Growth factors that contribute to tumor cell growth were also reduced. Increased DNA fragmentation, depression of proliferation and intracellular calcium levels, the accumulation of tumor cells in G0-->G1, and morphologic changes, were consistent with programmed cell death. Antioxidants such as alpha-tocopherol bound to membrane-associated proteins could inhibit the development of peroxidation products (hydroxyl radicals (.OH)), which attack proteins and modify their function and promote their degradation. Some kinases such as, cdc2 may be increased in activity, which would explain the observed increased expression of tumor suppressor p53, the accumulation of the tumor cells in G1 of the cell cycle and the inhibition of tumor cell proliferation. A reduction in oxidant radicals could also reduce transcription factor products, such as c-myb. Indirectly this result may occur through changes in nuclear translocation (signaling) NF-AT or the Rel-related family of transcription factors, including NF-kB (p50 or p65) or inhibition of immunophilin-calmodulin activity. Although the data remains fragmentary there are common points for control for tumor cell growth resulting from the effects of alpha-tocopherol or beta-carotene treatment. These changes involve phosphorylation and protein expression. Ultimately there is a reduction of important transcription factor protein products, a reduction in response to growth factors, and suppression of cell proliferation, resulting in increased control of the cell cycle.

Oral cancer inhibition by micronutrients. The experimental basis for clinical trials

Extensive research has been carried out in experimental animals to demonstrate the anticancer activity of retinoids, carotenoids and tocopherol on oral cancer and oral precancerous leukoplakia. The anticancer properties of these micronutrients have been studied in experiments dealing with inhibition of carcinogenesis, prevention of oral cancer development and regression of established oral carcinoma. Synergism has been demonstrated in the anticancer activity of beta carotene and alpha tocopherol. Synergism has also been demonstrated between beta carotene and anticancer alkylating agents such as melphalan and cyclophosphamide. Micronutrients such as beta carotene have been found to inhibit both major phases of carcinogenesis--initiation and promotion. Animal studies of oral cancer inhibition, prevention and regression have been substantiated by tissue culture studies, using animal and human derived oral cancer cell lines and normal epithelial cells. Mechanisms of the anticancer activity of the micronutrients on experimental oral cancer have been explored. They include stimulation of elements of the immune system to kill cancer cells, and enhanced expression of heat-shock proteins and repressor genes such as P 53.

The effectiveness of a mixture of beta-carotene, alpha-tocopherol, glutathione, and ascorbic acid for cancer prevention

Previous studies have shown that beta-carotene and alpha-tocopherol can act synergistically to inhibit the growth of experimentally induced oral cancer. The initial studies on the synergistic anticancer activity of antioxidants have been extended to include reduced glutathione and ascorbic acid. Sixty male hamsters (4-5 wks old) were divided into six equal groups. Groups 1-6 were treated with 7,12-dimethylbenz[a]anthracene (DMBA) (0.5% solution). Group 2 received a mixture containing equal amounts of beta-carotene, dl-alpha-tocopherol (vitamin E), glutathione, and l-ascorbic acid (vitamin C) (12.5 micrograms) delivered orally by pipette. Groups 3-6 were treated with beta-carotene alone (50 micrograms), vitamin E alone (50 micrograms), glutathione (50 micrograms) alone, and vitamin C alone (50 micrograms). Animals were euthanized at 12 and 14 weeks. Tumors were counted and measured, and tumor burden was calculated for each experimental group. The mixture of antioxidants significantly reduced tumor burden, whereas the beta-carotene, vitamin E, and reduced glutathione treatments also reduced tumor burden. beta-Carotene and glutathione provided greater levels of chemoprevention than vitamin E as single agents. In contrast, vitamin C treatment produced no antitumor effect but increased tumor burden by Week 14. This mixture of antioxidants produced a significant synergistic chemoprevention of oral cancer.

Rapid and sensitive detection of hydroxyl radicals formed by activated neutrophils in the presence of chelated iron: hydroxylation of deoxyguanosine to 8-hydroxydeoxyguanosine

Hydroxyl radicals (OH) can react with deoxyguanosine (dG) leading to the formation of 8-hydroxydeoxyguanosine (8OHdG). In this study, this has been used to detect the hydroxyl radicals formed when human polymorphonuclear leukocytes (PMNL) are stimulated with phorbol myristate acetate (PMA) in the presence of chelated iron. Reaction mixtures containing PMNL, PMA, dG and Fe-EDTA were incubated at 37 degrees C, and the formation of 8OHdG was analysed with high-performance liquid chromatography and electrochemical detection. 8OHdG formation was detected at PMA concentrations of 2 nM or higher, and half-maximal 8OHdG formation was found at around 6 nM PMA. Stimulation of 500,000 cells with 10 nM PMA for 20 min resulted in a 500 to 1000-fold increase in 8OHdG formation as compared to unstimulated cells. The 8OHdG formation decreased after addition of hydroxyl radical scavengers (sodium benzoate, dimethylsulfoxide, and mannitol) and increased after addition of platelet-activating factor (PAF), an agent known to stimulate the generation of reactive oxygen metabolites in neutrophils. These results demonstrate that hydroxylation of dG to 8OHdG can be used to determine neutrophil-generated hydroxyl radicals in different experimental systems. Since the analysis of 8OHdG is rapid, sensitive and easy, this may have wide applications in inflammation and cancer research.