Oxidative and nitrative DNA damage in animals and patients with inflammatory diseases in relation to inflammation-related carcinogenesis

Resveratrol suppresses oxidative stress and inflammatory response in diethylnitrosamine-initiated rat hepatocarcinogenesis

Hepatocellular carcinoma (HCC), one of the most frequent and deadliest cancers, has been increasing considerably in the United States. In the absence of a proven effective therapy for HCC, novel chemopreventive strategies are urgently needed to lower the current morbidity and mortality of HCC. Recently, we have reported that resveratrol, a compound present in grapes and red wine, significantly prevents diethylnitrosamine (DENA)-induced liver tumorigenesis in rats, although the mechanism of action is not completely understood. In the present study, we have examined the underlying mechanisms of resveratrol chemoprevention of hepatocarcinogenesis by investigating the effects of resveratrol on oxidative damage and inflammatory markers during DENA-initiated rat liver carcinogenesis. There was a significant increase in hepatic lipid peroxidation and protein oxidation in carcinogen control animals compared with their normal counterparts at the end of the study (20 weeks). Elevated expressions of inducible nitric oxide synthase and 3-nitrotyrosine were noticed in the livers of the same animals. Dietary resveratrol (50-300 mg/kg) administered throughout the study reversed all the aforementioned markers in a dose-responsive fashion in rats challenged with DENA. Resveratrol also elevated the protein and mRNA expression of hepatic nuclear factor E2-related factor 2 (Nrf2). Results of the present investigation provide evidence that attenuation of oxidative stress and suppression of inflammatory response mediated by Nrf2 could be implicated, at least in part, in the chemopreventive effects of this dietary agent against chemically induced hepatic tumorigenesis in rats. The outcome of this study may benefit the development of resveratrol in the prevention and intervention of human HCC.

Role of oxidative stress in stem, cancer, and cancer stem cells

The term ‘‘oxidative stress” refers to a cell’s state characterized by excessive production of reactive oxygen species (ROS) and oxidative stress is one of the most important regulatory mechanisms for stem, cancer, and cancer stem cells. The concept of cancer stem cells arose from observations of similarities between the self-renewal mechanism of stem cells and that of cancer stem cells, but compared to normal stem cells, they are believed to have no control over the cell number. ROS have been implicated in diverse processes in various cancers, and generally the increase of ROS in cancer cells is known to play an important role in the initiation and progression of cancer. Additionally, ROS have been considered as the most significant mutagens in stem cells; when elevated, blocking self-renewal and at the same time, serving as a signal stimulating stem cell differentiation. Several signaling pathways enhanced by oxidative stress are suggested to have important roles in tumorigenesis of cancer or cancer stem cells and the self-renewal ability of stem or cancer stem cells. It is now well established that mitochondria play a prominent role in apoptosis and increasing evidence supports that apoptosis and autophagy are physiological phenomena closely linked with oxidative stress. This review elucidates the effect and the mechanism of the oxidative stress on the regulation of stem, cancer, and cancer stem cells and focuses on the cell signaling cascades stimulated by oxidative stress and their mechanism in cancer stem cell formation, as very little is known about the redox status in cancer stem cells. Moreover, we explain the link between ROS and both of apoptosis and autophagy and the impact on cancer development and treatment. Better understanding of this intricate link may shed light on mechanisms that lead to better modes of cancer treatment.

Relationship between chronic trauma of the oral mucosa, oral potentially malignant disorders and oral cancer

BACKGROUND

Oral cancer represents 2%-5% of all cancers, being one of the 10 most frequent ones. Apart from oral cancer risk factors already described in literature, such as tobacco and alcohol consumption, others emerging risk factors have been proposed, such as chronic irritation from dental factors. The aim of this work was to assess the influence of chronic trauma of the oral mucosa (CTOM) in patients with oral potentially malignant disorders (OPMD) and cancer.

METHODS

A retrospective study of 406 patients (both sexes; aged between 18 and 80 years; with OPMD and cancer) who attended the Department of Clinical Stomatology A of the National University of Cordoba was performed by non-probabilistic sampling. The association of variables and outcome variable diagnosis, with levels control, OPMD, oral cancer, was evaluated by multinomial regression model.

RESULTS

Population under study was represented by 72% of control patients, 16% patients with OPMD and 11% of patients with oral cancer. It was observed a significant association between diagnosis and CTOM (P = 0.000), after adjustment of confounding factors (smoking and drinking habits, sex, cancer inheritance and denture use).

CONCLUSIONS

Our results suggest that CTOM is, together with other factors, an important risk factor in patients with oral cancer diagnosis, but not for patients with OPMD.

Reduction of periductal fibrosis in liver fluke-infected hamsters after long-term curcumin treatment

Chronic infection with the liver fluke, Opisthorchis viverrini, induces advanced periductal fibrosis and is a relative risk factor for cholangiocarcinoma in Southeastern Asia. We examined the reducing effect of curcumin on hepatobiliary fibrosis using O. viverrini-infected hamsters supplemented with dietary 1% curcumin (w/w) as an animal model. The expression profile of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs), cytokines, and collagens was assessed in relation to liver fibrosis. Histopathological studies revealed that curcumin had no effect on fibrosis at the short-term infection (21 days and 1 month); however, peribiliary fibrosis was significantly reduced after the long-term curcumin treatment for 3 months, compared to the untreated group. Expression of alpha-smooth muscle actin was associated with the reduction of liver fibrosis. A decrease in hepatic hydroxyproline level and mRNA expression of collagen I and III supported the reduction of fibrosis. The expression of TIMP-1, TIMP-2, and tumor necrosis factor-alpha genes was also decreased after curcumin treatment. In contrast, curcumin increased mRNA expression of MMP-13, MMP-7 (at 6 months), interleukin-1 beta, and transforming growth factor beta, implying that increased MMPs activity contributes to extracellular matrix degradation. These results suggest that curcumin reduces periductal fibrosis after long-term treatment by tissue resorption via inhibition of TIMPs expression and enhancement of MMPs expression mediated by cytokines. In conclusion, curcumin may serve as a promising nutraceutical agent exerting antifibrotic effect in O. viverrini-infected patients and contribute to cholangiocarcinoma prevention.

Oligosaccharides from agar inhibit pro-inflammatory mediator release by inducing heme oxygenase 1

We investigated whether agaro-oligosaccharides have any immunological effects on RAW264.7 mouse macrophages and human monocytes in vitro. We demonstrate that agaro-oligosaccharides suppressed the elevated levels of nitric oxide, prostaglandin E(2), and such pro-inflammatory cytokines as tumor necrosis factor-alpha, interleukin-1beta and interleukin-6 in lipopolysaccharide-stimulated monocytes and macrophages. We also demonstrate that those effects of agaro-oligosaccharides on activated monocytes and macrophages may have been caused by heme oxygenase-1 induction. It is therefore proposed that agaro-oligosaccharides might be a good candidate for a functional food to prevent inflammatory diseases.

Loss of Nkx3.1 expression in bacterial prostatitis: a potential link between inflammation and neoplasia

NKX3.1 is a homeodomain protein that functions as a dosage sensitive prostate-specific transcription factor. Diminished NKX3.1 expression is associated with prostate epithelial cell proliferation in vitro and with increasing Gleason grade in patient samples. Mouse Nkx3.1 also functions as a negative regulator of prostate cell growth in prostate cancer models. Identifying biological and environmental factors that modulate NKX3.1 accumulation is therefore central to efforts aimed at elucidating prostate growth control mechanisms. To determine the effect of inflammation on Nxk3.1 accumulation, bacterial prostatitis was induced by intraurethral inoculation of a uropathogenic E. coli strain in mice. Nkx3.1 expression was profoundly reduced in infected prostate lobes and correlated with increased expression of a proliferation marker. Androgen receptor levels were also reduced in concert with Nkx3.1, and a marked increase in the basal cell marker p63 was observed. Analyses of the inflammatory infiltrate revealed a classic acute inflammatory response that attained characteristics of a chronic state within fourteen days postinoculation. Comparison of the four prostate lobes revealed clear differences in the extent of inflammation. These data demonstrate that acute inflammation in response to a bacterial agent in the prostate is associated with a significant diminution in the level of a key regulator of prostate cell proliferation. These observations provide a plausible mechanism whereby prostate inflammation may establish a local environment conducive to epithelial cell growth.

Role of oxidatively induced DNA lesions in human pathogenesis

Genome stability is essential for maintaining cellular and organismal homeostasis, but it is subject to many threats. One ubiquitous threat is from a class of compounds known as reactive oxygen species (ROS), which can indiscriminately react with many cellular biomolecules including proteins, lipids, and DNA to produce a variety of oxidative lesions. These DNA oxidation products are a direct risk to genome stability, and of particular importance are oxidative clustered DNA lesions (OCDLs), defined as two or more oxidative lesions present within 10 bp of each other. ROS can be produced by exposure of cells to exogenous environmental agents including ionizing radiation, light, chemicals, and metals. In addition, they are produced by cellular metabolism including mitochondrial ATP generation. However, ROS also serve a variety of critical cellular functions and optimal ROS levels are maintained by multiple cellular antioxidant defenses. Oxidative DNA lesions can be efficiently repaired by base excision repair or nucleotide excision repair. If ROS levels increase beyond the capacity of its antioxidant defenses, the cell's DNA repair capacity can become overwhelmed, leading to the accumulation of oxidative DNA damage products including OCDLs, which are more difficult to repair than individual isolated DNA damage products. Here we focus on the induction and repair of OCDLs and other oxidatively induced DNA lesions. If unrepaired, these lesions can lead to the formation of mutations, DNA DSBs, and chromosome abnormalities. We discuss the roles of these lesions in human pathologies including aging and cancer, and in bystander effects.

A functional polymorphism in the NAD(P)H oxidase subunit CYBA is related to gene expression, enzyme activity, and outcome in non-Hodgkin lymphoma

NAD(P)H oxidase is a major endogenous source of reactive oxygen species (ROS). ROS may not only be involved in carcinogenesis but also in efficacy of chemotherapeutic agents like doxorubicin. By a comprehensive genotyping approach covering 48 genetic polymorphisms (single-nucleotide polymorphisms) in five subunits of phagocytic NAD(P)H oxidase, we asked whether they affect gene expression, enzymatic activity, and outcome of CHO(E)P chemotherapy. A highly consistent effect was observed for the CYBA 640A>G variant. In peripheral blood granulocytes of 125 healthy volunteers, the G allele of 640A>G was associated with lower NAD(P)H oxidase activity (P = 0.006). Moreover, the G allele was associated with lower mRNA and protein expression (both P = 0.02). Of clinical importance, the outcome of patients suffering from non-Hodgkin lymphoma and treated with CHO(E)P regimen was dependent on the CYBA 640A>G polymorphism. In an exploratory study (n = 401), carriers of 640GG had an event-free survival (EFS) risk ratio of 1.95 [95% confidence interval (95% CI), 1.31-2.90; P = 0.001] compared with 640AA. In a confirmatory set (n = 477), the risk ratios were 1.53 (1.04-2.25, P = 0.03). The complete set of 878 patients showed a relative risk of 1.72 (1.30-2.26) and 1.59 (1.14-2.21) for EFS and overall survival, respectively. Further molecular-biological experiments showed lower expression and reduced stability of transcripts with the G allele in lymphoblastoid cell lines. Transfection of allele-specific plasmids into HEK293 cells elicited lower activity for the G allele in a luciferase reporter gene construct. Thus, CYBA 640A>G was shown to be a functional polymorphism with possible consequences for patients receiving CHO(E)P chemotherapy and might have further implications for other ROS-mediated modalities.

Formation of 8-nitroguanine, a nitrative DNA lesion, in inflammation-related carcinogenesis and its significance

Chronic infection and inflammation contribute to a substantial part of environmental carcinogenesis. Recently, it has been estimated that chronic inflammation accounts for approximately 25% of cancer cases. Various infectious diseases and physical, chemical, and immunological factors participate in inflammation-related carcinogenesis. Under inflammatory conditions, reactive oxygen and nitrogen species, which are generated from inflammatory and epithelial cells, may play an important role in carcinogenesis by causing DNA damage. 8-Nitroguanine is a mutagenic DNA lesion formed during chronic inflammation. In an earlier publication, our group reported the results of an immunohistochemical analysis of animals infected with the liver fluke Opisthorchis viverrini and demonstrated for the first time that 8-nitroguanine was formed at the sites of carcinogenesis. This DNA lesion was found to accumulate in the carcinogenic process in clinical specimens of cancer-prone inflammatory diseases caused by various pathogens, including human papillomavirus and Epstein-Barr virus. Moreover, strong 8-nitroguanine formation in tumor tissues was closely associated with a poor prognosis. On the basis of these findings, 8-nitroguanine could be a potential biomarker to evaluate the risk of inflammation-related carcinogenesis and the prognosis of cancer patients. In this review, the significance of 8-nitroguanine formation in inflammation-related carcinogenesis and tumor progression will be discussed.

Formation of 8-nitroguanine, a nitrative DNA lesion, in inflammation-related carcinogenesis and its significance

Chronic infection and inflammation contribute to a substantial part of environmental carcinogenesis. Recently, it has been estimated that chronic inflammation accounts for approximately 25% of cancer cases. Various infectious diseases and physical, chemical, and immunological factors participate in inflammation-related carcinogenesis. Under inflammatory conditions, reactive oxygen and nitrogen species, which are generated from inflammatory and epithelial cells, may play an important role in carcinogenesis by causing DNA damage. 8-Nitroguanine is a mutagenic DNA lesion formed during chronic inflammation. In an earlier publication, our group reported the results of an immunohistochemical analysis of animals infected with the liver fluke Opisthorchis viverrini and demonstrated for the first time that 8-nitroguanine was formed at the sites of carcinogenesis. This DNA lesion was found to accumulate in the carcinogenic process in clinical specimens of cancer-prone inflammatory diseases caused by various pathogens, including human papillomavirus and Epstein-Barr virus. Moreover, strong 8-nitroguanine formation in tumor tissues was closely associated with a poor prognosis. On the basis of these findings, 8-nitroguanine could be a potential biomarker to evaluate the risk of inflammation-related carcinogenesis and the prognosis of cancer patients. In this review, the significance of 8-nitroguanine formation in inflammation-related carcinogenesis and tumor progression will be discussed.

Inflammatory alterations in excluded colon in rats: a comparison with chemically induced colitis

Diversion colitis occurs commonly in the large bowel remnant after diversion of the fecal stream. Several experimental models of colitis have been described, but none examine the inflammatory alterations that can occur in experimentally defunctioned colons. This characterization could be useful in understanding pathophysiological aspects of diversion colitis, and in developing future therapeutic strategies. Thus, we evaluated the temporal inflammatory alterations in the defunctioned colon of rats by analyzing the histological results, infiltrating neutrophils, pro-inflammatory markers such as cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS), and DNA damage in isolated colonocytes. We compared the obtained data with those from hapten-induced colitis. The experimental diversion of the colon fecal stream induces diversion colitis characterized by an early inflammatory process with increased neutrophil infiltrate, and COX-2 and iNOS expression that resembles, in some aspects, the inflammatory characteristics of chemically induced colitis. After acute inflammation resolution, there was an increase in COX-2 and iNOS expression and the presence of lymphoid follicular hyperplasia and ulcerations, suggesting that diversion colitis can be experimentally established and useful for studying different pathophysiological aspects of this condition.

Macrophage involvement in Epstein-Barr virus-related tumors

Epstein-Barr virus (EBV) is known as a causative agent of Burkitt's lymphoma, nasopharyngeal carcinoma and approximately 10% of stomach carcinoma cases. In other human cancers, EBV gene expression including lytic infection protein detected using in situ hybridization and immunofluorescence staining has been reported. Moreover, the expression and replication of EBV genes in cultured normal macrophages and in histiocytes of Langerhans' cell histiocytosis have been identified. The aim of this study was to examine EBV expression in macrophages in other EBV-associated human tumors. Forty-one cases of EBV-associated tumors, which had been confirmed to express EBV, were examined. Tissue sections after in situ hybridization were double-stained immunohistochemically with the monoclonal anti-CD68 antibody. EBV expression in macrophages in the lesions of nasopharyngeal carcinoma, oral cancer, thyroid carcinoma, renal cell carcinoma, testicular carcinoma, uterine carcinoma, cutaneous T-cell lymphoma and anaplastic large-cell lymphoma was identified, whereas macrophages in normal or non-cancerous lesions showed no EBV expression. Many tumor-associated macrophages in EBV-related tumors carry EBV, which appears to induce the EBV lytic infection of macrophages. Therefore, the possibility that the lytic infection of macrophages by EBV and the resulting inflammation play certain roles in the oncogenesis of EBV-associated human tumors was raised.

Prognostic markers and putative therapeutic targets for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most frequent human cancer and a fatal disease. Therapies with pharmacological agents do not improve the prognosis of patients with unresectable HCC. This emphasizes the need to identify new targets for early diagnosis, chemoprevention, and treatment of the disease. Available evidence indicates that clinical outcome of HCC could reflect the genetic predisposition to cancer development and progression. Numerous loci controlling HCC progression have been identified in rodents. In this review, we describe results of recent studies on effector mechanisms of susceptibility/resistance genes, responsible for HCC progression, aimed at identifying new putative prognostic markers and therapeutic targets of this tumor. Highest c-myc amplification and overexpression, alterations of iNOS crosstalk with IKK/NF-kB and RAS/ERK signaling, ubiquitination of ERK and cell cycle inhibitors, and deregulation of FOXM1 and cell cycle key genes occur in rapidly progressing dysplastic nodules and HCC, induced in genetic susceptible rat strains, compared to the lesions of resistant rats. Notably, alterations of these mechanisms in human HCC subtypes with poorer or better prognosis, are similar to those present in genetically susceptible and resistant rats, respectively, and function as prognostic markers and therapeutic targets. Attempts to cure advanced HCC by molecular therapy directed against specific targets led to modest survival benefit. Thus, efforts are necessary to identify and test, in pre-clinical and clinical studies, new therapeutic targets for combined molecular treatments of HCC. They may take advantage from the comparative analysis of signal transduction in HCCs differently prone to progress, in rats and humans.

A gamma-tocopherol-rich mixture of tocopherols inhibits chemically induced lung tumorigenesis in A/J mice and xenograft tumor growth

The present study investigated the effects of a preparation of a gamma-tocopherol-rich mixture of tocopherols (gamma-TmT) on chemically induced lung tumorigenesis in female A/J mice and the growth of H1299 human lung cancer cell xenograft tumors. In the A/J mouse model, the lung tumors were induced by either 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK; intraperitoneal injections with 100 and 75 mg/kg on Week 1 and 2, respectively) or NNK plus benzo[a]pyrene (B[a]P) (8 weekly gavages of 2 mumole each from Week 1 to 8). The NNK plus B[a]P treatment induced 21 tumors per lung on Week 19; dietary 0.3% gamma-TmT treatment during the entire experimental period significantly lowered tumor multiplicity, tumor volume and tumor burden (by 30, 50 and 55%, respectively; P < 0.05). For three groups of mice treated with NNK alone, the gamma-TmT diet was given during the initiation stage (Week 0 to 3), post-initiation stage (Week 3 to 19) or the entire experimental period, and the tumor multiplicity was reduced by 17.8, 19.7 or 29.3%, respectively (P < 0.05). gamma-TmT treatment during the tumor initiation stage or throughout the entire period of the experiment also significantly reduced tumor burden (by 36 or 43%, respectively). In the xenograft tumor model of human lung cancer H1299 cells in NCr-nu/nu mice, 0.3% dietary gamma-TmT treatment significantly reduced tumor volume and tumor weight by 56 and 47%, respectively (P < 0.05). In both the carcinogenesis and tumor growth models, the inhibitory action of gamma-TmT was associated with enhanced apoptosis and lowered levels of 8-hydroxydeoxyguanine, gamma-H2AX and nitrotyrosine in the tumors of the gamma-TmT-treated mice. In cell culture, the growth of H1299 cells was inhibited by tocopherols with their effectiveness following the order of delta-T > gamma-TmT > gamma-T, whereas alpha-T was not effective. These results demonstrate the inhibitory effect of gamma-TmT against lung tumorigenesis and the growth of xenograft tumors of human lung cancer cells. The inhibitory activity may be due mainly to the actions of delta-T and gamma-T.

Expression of thioredoxin during progression of hamster and human cholangiocarcinoma

Thioredoxin (Trx) is a multifunctional redox protein that has growth-promoting and anti-apoptotic effects on cells and protects cells from endogenous and exogenous free radicals. Recently, altered expression of Trx has been reported in various cancers. In the present study, we investigated altered expression of Trx at the precancerous and carcinogenic phases during cholangiocarcinogenesis in a hamster cholangiocarcinoma (ChC) model, using semiquantitative immunohistochemical and Western blot analyses. Moreover, to determine if the results correlated well with those in human ChCs, we carried out a comparative immunohistochemical study for Trx in tissue-arrayed human ChCs with different grades of tumor cell differentiation. Trx was found highly expressed in the cytoplasm of dysplastic bile ducts with highly abnormal growth patterns and ChCs irrespective of tumor type or tumor cell differentiation. Overexpression of Trx at the precancerous and carcinogenic phases was further supported by significant elevation of Trx protein in Western blotting. The results from the hamster ChCs were in good agreement with those from human ChCs. Our results strongly suggested that the redox regulatory function of Trx plays an important role in bile duct cell transformation and tumor progression during cholangiocarcinogenesis.

The modifying effects of green tea polyphenols on acute colitis and inflammation-associated colon carcinogenesis in male ICR mice

Reactive oxygen species (ROS) have been implicated as mediators of intestinal inflammation and carcinogenesis. Although green tea polyphenols (GTP) have anticancer property as antioxidants they also generate ROS in vitro. In this study, we investigated the modifying effects of GTP on dextran sulfate sodium (DSS)-induced acute colitis and on 1,2-dimethylhydrazine (DMH) and DSS-induced colon carcinogenesis in male ICR mice. At sacrifice after 6 days, the colon shortening induced by 2% DSS was unchanged by 0.1% and 0.25% GTP, but increased by 0.5% and 1% GTP-containing diet. The expression of interleukin-1beta and macrophage-migration inhibitory factor in the DSS + 0.1% GTP group were lower than the DSS alone group, whereas the expression levels were increased in the DSS + 0.5% GTP and DSS + 1% GTP groups when compared with the DSS alone group. In a subsequent experiment to determine the effects of 0.01-1% GTP on inflammation-associated colon carcinogenesis induced by DMH/DSS, 0.5 and 1% doses of GTP failed to prevent the development of multiple colon tumors, rather, they tended to increase it. Our results thus indicate that the modifying effects of GTP on DSS-induced acute colitis and DMH/DSS-induced colon carcinogenesis depends upon its dosage and the expression of proinflammatory cytokines.

Identification of ROS using oxidized DCFDA and flow-cytometry

Cells constantly generate reactive oxygen species (ROS) during aerobic metabolism. The ROS generation plays an important protective and functional role in the immune system. The cell is armed with a powerful antioxidant defense system to combat excessive production of ROS. Oxidative stress occurs in cells when the generation of ROS overwhelms the cells' natural antioxidant defenses. ROS and the oxidative damage are thought to play an important role in many human diseases including cancer, atherosclerosis, other neurodegenerative diseases and diabetes. Thus, establishing their precise role requires the ability to measure ROS accurately and the oxidative damage that they cause. There are many methods for measuring free radical production in cells. The most straightforward techniques use cell permeable fluorescent and chemiluminescent probes. 2'-7'-Dichlorodihydrofluorescein diacetate (DCFH-DA) is one of the most widely used techniques for directly measuring the redox state of a cell. It has several advantages over other techniques developed. It is very easy to use, extremely sensitive to changes in the redox state of a cell, inexpensive and can be used to follow changes in ROS over time.

Somatic mutations of mitochondrial genome in hepatocellular carcinoma

Somatic mutations have been identified in mitochondrial DNA (mtDNA) of various human primary cancers. However, their roles in the pathophysiology of cancers are still unclear. In our previous study, high frequency of somatic mutations was found in the D-loop region of mtDNA of hepatocellular carcinomas (HCCs). In the present study, we examined 44 HCCs and corresponding non-cancerous liver tissues, and identified 13 somatic mutations in the coding region of mtDNAs from 11 HCC samples (11/44, 25%). Among the 13 mtDNA mutations, six mutations (T6787C, G7976A, A9263G, G9267A, A9545G and A11708G) were homoplasmic while seven mutations (956delC, T1659C, G3842A, G5650A, 11032delA, 12418insA and a 66bp deletion) were heteroplasmic. Moreover, the G3842A transition created a premature stop codon and the 66bp deletion could omit 22 amino acid residues in the NADH dehydrogenase (ND) subunit 1 (ND1) gene. The 11032delA and 12418insA could result in frame-shift mutation in the ND4 and ND5 genes, respectively. The T1659C transition in tRNA(Val) gene and G5650A in tRNA(Ala) gene were reported to be clinically associated with some mitochondrial disorders. In addition, the T6787C (cytochrome c oxidase subunit I, COI), G7976A (COII), G9267A (COIII) and A11708G (ND4) mutations could result in amino acid substitutions in the highly conserved regions of the affected mitochondrial genes. These mtDNA mutations (10/13, 76.9%) have the potential to cause mitochondrial dysfunction in HCCs. Taken these results together, we suggest that there may be a higher frequency of mtDNA mutations in HCC than in normal liver tissues from the same individuals.

Reactive nitrogen species mediate DNA damage in Helicobacter pylori-infected gastric mucosa

BACKGROUND

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) can play an important role in cellular injury and carcinogenesis of gastric epithelial cells infected with Helicobacter pylori. 8-OH-deoxy guanosine (8-OHdG) and 8-nitroguanine (8-NG) are markers for ROS- and RNS-mediated DNA oxidation, respectively. In this study, RNS-mediated DNA damage in gastric mucosa was observed directly using a newly developed antibody to 8-NG to clarify how H. pylori infection causes nitrative DNA damage to gastric epithelial cells.

METHODS

Immunohistochemistry with anti-8-OHdG and anti-8-NG antibodies was performed on gastric tissue samples from 45 patients (25 men and 20 women) with H. pylori-positive gastritis and 19 patients (11 men and 8 women) exhibiting successful H. pylori eradication. Histologic factors for gastric mucosal inflammation were graded according to the guidelines of the Updated Sydney system.

RESULTS

In corpus mucosa, 8-OHdG and 8-NG production were significantly associated with the degree of glandular atrophy, infiltration of chronic inflammatory cells and intestinal metaplasia in the glandular epithelial cells. Successful H. pylori eradication resulted in a significant reduction of chronic inflammatory cell infiltration and neutrophilic activity. Mean 8-OHdG production was lower after H. pylori eradication in both corpus and antral mucosa (p = .022 and .049, respectively). However, the reduction in 8-NG exhibited was more pronounced than the reduction of 8-OhdG (p = .004 and .007, respectively).

CONCLUSIONS

Helicobacter pylori infection can induce inflammatory cells infiltration, which evokes DNA damage of gastric epithelial cells through ROS and RNS production. 8-NG might be a more sensitive biomarker than 8-OHdG for H. pylori-induced DNA damage in gastric mucosa.

Resveratrol in the chemoprevention and treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers and lethal diseases in the world. Although the majority of HCC cases occur in developing countries of Asia and Africa, the prevalence of liver cancer has risen considerably in Japan, Western Europe as well as the United States. HCC most commonly develops in patients with chronic liver disease, the etiology of which includes viral hepatitis (B and C), alcohol, obesity, iron overload and dietary carcinogens, including aflatoxins and nitrosamines. The current treatment modalities, including surgical resection and liver transplantation, have been found to be mostly ineffective. Hence, there is an obvious critical need to develop alternative strategies for the chemoprevention and treatment of HCC. Oxidative stress as well as inflammation has been implicated in the development and progression of hepatic neoplasia. Using naturally occurring phytochemicals and dietary compounds endowed with potent antioxidant and antiinflammatory properties is a novel approach to prevent and control HCC. One such compound, resveratrol, present in grapes, berries, peanuts as well as red wine, has emerged as a promising molecule that inhibits carcinogenesis with a pleiotropic mode of action. This review examines the current knowledge on mechanism-based in vitro and in vivo studies on the chemopreventive and chemotherapeutic potential of resveratrol in liver cancer. Pre-clinical and clinical toxicity studies as well as pharmacokinetic data of resveratrol have also been highlighted in this review. Future directions and challenges involved in the use of resveratrol for the prevention and treatment of HCC are also discussed.

The DNA-damage response in human biology and disease

The prime objective for every life form is to deliver its genetic material, intact and unchanged, to the next generation. This must be achieved despite constant assaults by endogenous and environmental agents on the DNA. To counter this threat, life has evolved several systems to detect DNA damage, signal its presence and mediate its repair. Such responses, which have an impact on a wide range of cellular events, are biologically significant because they prevent diverse human diseases. Our improving understanding of DNA-damage responses is providing new avenues for disease management.

Inhibitory effects of aminoguanidine on thyroid follicular carcinoma development in inflamed capsular regions of rats treated with sulfadimethoxine after N-bis(2-hydroxypropyl)nitrosamine-initiation

We have reported that thyroid capsular thickening with inflammation induced by an antithyroidal agent, sulfadimethoxine (SDM), might play a role in the development of invasive follicular carcinomas in rats initiated with N-bis(2-hydroxypropyl)nitrosamine (DHPN). Inducible nitric oxide synthase (iNOS) expressed in the inflamed capsular regions further appeared to be implicated in the tumor progression. In the present study, the effects of an iNOS inhibitor, aminoguanidine (AG), on thyroid carcinogenesis were examined. F344 male rats were treated with SDM in drinking water (0.1%) with or without concomitant dietary administration of AG (0.2%) for 4 and 10 weeks after subcutaneous injection of DHPN at 2800 mg/kg bodyweight. At week 4, thyroid capsular thickening with inflammation was observed and iNOS-positive foci were found in the inflamed regions. In addition, single-strand DNA-positive inflammatory cells were scattered among neighboring follicular cells, indicating some cellular damage, at least partly in association with iNOS induction. Concurrent dietary administration of AG with SDM treatment slightly decreased the number of single-strand DNA-positive cells but did not alter the incidence and multiplicity of iNOS-positive foci in the inflamed capsular regions at week 4. At week 10, however, invasive follicular carcinomas predominantly arose in the thickened capsule in the DHPN-SDM-treated rats, and AG administration decreased (P < 0.05) their multiplicity. The carcinoma cells were partly positive for iNOS. These results thus suggested that iNOS induction in both inflammatory and tumor cells might play pivotal roles in tumor progression in this DHPN-SDM rat model.

Oxidative stress in depressive patients with gastric adenocarcinoma

Recent data from several studies suggest that oxidative stress is involved in the biochemical mechanisms that underlie neuropsychiatric disorders. The present study was designed to investigate oxidative stress status in depressive patients with gastric adenocarcinoma (GA) at TNM stage III. Oxidative stress, depression and expression of specific genes were monitored during a pretreatment period. Serum total antioxidant capacity, catalase, superoxide dismutase concentrations, and antisuperoxide anion capacity (A-ASC) were significantly decreased in depressive patients compared to control subjects, whereas serum malondialdehyde (MDA) levels were significantly increased. Importantly, the formation of 8-hydroxy-deoxyguanosine (8-OHdG) accumulated. Furthermore, SYBR Green real-time PCR revealed that the expression levels of human oxoguanine glycosylase 1 and APEX nuclease 1 (APEX1) were increased in depressive patients. Pearson correlation analysis revealed that depression was positively correlated with SAS, SCL-90, MDA, 8-OHdG and APEX1, but negatively correlated with A-ASC. Thus, this study confirms oxidative imbalance in depressive patients with GA, and oxidative stress may play a role in the onset and exacerbation of depression.

Steatocholecystitis and fatty gallbladder disease

Obesity has become an epidemic worldwide. It is accompanied by a multitude of medical complications including metabolic syndrome. Obesity may lead to fatty infiltration of multiple internal organs including liver, heart, kidney, and pancreas, causing organ dysfunctions. Fatty infiltration leads to chronic inflammation and tissue damage. Fatty infiltration in the liver results in nonalcoholic fatty liver disease, which is increasingly common nowadays. Recent studies in animals and humans indicate that obesity also is associated with fatty infiltration of gallbladder, resulting in cholecystosteatosis. The increased gallbladder lipids include free fatty acids, phospholipids, and triglycerides. Enhanced inflammation with an increased amount of fat in the gallbladder results in an abnormal wall structure and decreased contractility. In support of this notion, a recent experiment on the effect of Ezetimibe, which is a novel drug that inhibits intestinal fat absorption, on fatty gallbladder disease reveals that Ezetimibe can ameliorate cholecystosteatosis and restore in vivo gallbladder contractility. The proportion of cholecystectomies performed for chronic acalculous cholecystitis has increased significantly over the past two decades. An increase in gallbladder fat, which leads to poor gallbladder emptying and biliary symptoms, may partly explain this phenomenon. Although dietary carbohydrates have been demonstrated to be associated with fatty gallbladder disease, other potential modifiable environmental factors are not clear. The pathogenesis and prognosis of fatty gallbladder disease, including steatocholecystitis, and the relations of fatty gallbladder disease to nonalcoholic fatty liver disease, including steatohepatitis, and other components of metabolic syndrome are largely unknown. More research is needed to answer these questions.

Avaliação da expressão tecidual do gene de reparo MLH1 e dos níveis de dano oxidativo ao DNA em doentes com câncer colorretal

O dano oxidativo ao DNA provocado por radicais livres de oxigênio representa um dos principais mecanismos responsáveis pelas etapas iniciais da carcinogênese colorretal. O estresse oxidativo ocasiona erros de pareamento de bases possibilitando o aparecimento de mutações em genes controladores do ciclo celular. As células possuem um sistema de defesa representado pelos genes de reparo do DNA que corrigindo os erros de pareamento impedem o desenvolvimento de mutações. Poucos estudos avaliaram a relação entre dano oxidativo ao DNA e a expressão tecidual do gene de reparo MLH1. OBJETIVO: O objetivo do presente estudo foi avaliar os níveis de estresse oxidativo ao DNA e a expressão tecidual do gene de reparo MLH1 nas células da mucosa cólica normal e neoplásica de doentes com câncer colorretal. MATERIAL E MÉTODO: Foram estudados 44 doentes com diagnóstico de adenocarcinoma colorretal. Foram excluídos os doentes com câncer colorretal hereditário, portadores de câncer relacionado às doenças inflamatórias intestinais e os submetidos à radioquimioterapia neoadjuvante. Para a avaliação dos níveis de dano oxidativo ao DNA utilizou-se a técnica da eletroforese alcalina em gel de célula isolada (ensaio do cometa) avaliando 100 células obtidas dos tecidos normal e neoplásico. Para a avaliação da expressão do gene MLH1 utilizou-se a técnica de reação de polimerase em cadeia em tempo real (RT-PCR) com primer especificamente desenhados para amplificação do gene. A comparação dos resultados encontrados para os níveis de estresse oxidativo ao DNA, e expressão do gene MLH1 nos tecidos normais e neoplásicos foi feito pelo teste t de Student, adotando-se nível de significância de 5% (p<0,05). RESULTADOS: Os níveis de dano oxidativo ao DNA no tecido neoplásico foram significativamente mais elevados quando comparados ao tecido normal (p=0,0001). A expressão tecidual do gene MLH1 no tecido neoplásico foi significativamente menor quando comparado ao tecido normal (p=0,02). CONCLUSÃO: O gene de reparo MLH1 encontra-se menos expresso no tecido neoplásico e inversamente relacionado aos níveis de dano oxidativo ao DNA.

Nitric oxide induces early viral transcription coincident with increased DNA damage and mutation rates in human papillomavirus-infected cells

High-risk human papillomavirus (HPV) infections are necessary but insufficient causes of cervical cancers. Other risk factors for cervical cancer (e.g., pregnancy, smoking, infections causing inflammation) can lead to high and sustained nitric oxide (NO) concentrations in the cervix, and high NO levels are related to carcinogenesis through DNA damage and mutation. However, the effects of NO exposure in HPV-infected cells have not been investigated. In this study, we used the NO donor DETA-NO to model NO exposure to cervical epithelium. In cell culture media, 24-hour exposure to 0.25 to 0.5 mmol/L DETA-NO yielded a pathologically relevant NO concentration. Exposure of cells maintaining episomal high-risk HPV genomes to NO increased HPV early transcript levels 2- to 4-fold but did not increase viral DNA replication. Accompanying increased E6 and E7 mRNA levels were significant decreases in p53 and pRb protein levels, lower apoptotic indices, increased DNA double-strand breaks, and higher mutation frequencies when compared with HPV-negative cells. We propose that NO is a molecular cofactor with HPV infection in cervical carcinogenesis, and that modifying local NO cervical concentrations may constitute a strategy whereby HPV-related cancer can be reduced.

Targeting cancer cells by ROS-mediated mechanisms: a radical therapeutic approach?

Increased generation of reactive oxygen species (ROS) and an altered redox status have long been observed in cancer cells, and recent studies suggest that this biochemical property of cancer cells can be exploited for therapeutic benefits. Cancer cells in advanced stage tumours frequently exhibit multiple genetic alterations and high oxidative stress, suggesting that it might be possible to preferentially eliminate these cells by pharmacological ROS insults. However, the upregulation of antioxidant capacity in adaptation to intrinsic oxidative stress in cancer cells can confer drug resistance. Abrogation of such drug-resistant mechanisms by redox modulation could have significant therapeutic implications. We argue that modulating the unique redox regulatory mechanisms of cancer cells might be an effective strategy to eliminate these cells.

Genetic and epigenetic control of molecular alterations in hepatocellular carcinoma

Comparative analysis of hepatocellular carcinoma (HCC) in rat strains that are either susceptible or resistant to the induction of HCC has allowed the mapping of genes responsible for inherited predisposition to HCC. These studies show that the activity of several low penetrance genes and a predominant susceptibility gene regulate the development of hepatocarcinogenesis in rodents. These studies shed light on the epidemiology of human HCC. The identified genes regulate resistance to hepatocarcinogenesis by affecting the capacity of the initiated cells to grow autonomously and to progress to HCC. Analysis of the molecular alterations showed highest iNos cross-talk with IKK/NF-kB and RAS/ERK pathways in most aggressive liver lesions represented by HCC in the susceptible F344 rats. Unrestrained extracellular signal-regulated kinase (Erk) activity linked to proteasomal degradation of dual-specificity phosphatase 1 (Dusp1), a specific ERK inhibitor, by the CKS1-SKP2 ubiquitin ligase complex was highest in more aggressive HCC of genetically susceptible rats. Furthermore, deregulation of G1 and S phases of the cell cycle occurs in HCC of susceptible F344 rats, leading to pRb hyperphosphorylation and elevated DNA synthesis, whereas a block to G1-S transition is present in the HCC of resistant BN rats. Importantly, similar alterations in the signaling pathways that regulate cell cycle progression were found in human HCC with poorer prognosis (as defend by patients' survival length), whereas human HCC with better prognosis had molecular characteristics similar to the lesions in the HCC of resistant rat strains. This review discusses the role of molecular alterations involved in the acquisition of resistance or susceptibility to HCC and the importance of genetically susceptible and resistant rat models for the identification of prognostic markers, and chemopreventive or therapeutic targets for the biological network therapy of human disease.

Carcinogenesis in IBD: potential targets for the prevention of colorectal cancer

In patients with IBD, chronic colonic inflammation increases the risk of colorectal cancer, perhaps because inflammation predisposes these tissues to genomic instability. Carcinogenesis in the inflamed colon seems to follow a different sequence of genetic alterations than that observed in sporadic cancers in the uninflamed colon. In this Review, we focus on the genetic alterations in colitis-associated colorectal cancer that contribute to the acquisition of the essential hallmarks of cancer, and on how those alterations differ from sporadic colorectal cancers. Our intent is to provide a conceptual basis for categorizing carcinogenetic molecular abnormalities in IBD, and for understanding how cancer-preventive therapies might target reversal of acquired abnormalities in specific biochemical pathways.

Two cases of bovine sarcoma in clinically long-standing lesions

Histopathological examination of clinically long-standing lesions with durations of one year or more in the extremities of two cattle revealed the presence of sarcomas with distant metastases. In case 1, neoplastic cells were fusiform to pleomorphic, stained for no specific differentiation markers, and diagnosed as undifferentiated sarcoma. Neoplastic growth in case 2 was composed of spindle to histiocytoid cells and a significant number of multinucleated giant cells, both of which were immunoreactive to histiocyte markers, and diagnosed as giant cell malignant fibrous histiocytoma. Neoplastic cells of both cases were immunohistochemically positive for nitric oxide-related antigens, which were recognized as markers of inflammation-induced carcinogenesis in human and laboratory animals.

Immunohistochemical analysis of 8-nitroguanine, a nitrative DNA lesion, in relation to inflammation-associated carcinogenesis

Chronic inflammation is induced by various infectious/infected agents and by many physical, chemical and immunological factors. Many malignancies arise from areas of infection and inflammation. Reactive oxygen species and reactive nitrogen species are considered to play the key role in inflammation-associated carcinogenesis by causing oxidative and nitrative DNA damage. 8-Nitroguanine is a mutagenic nitrative DNA lesion formed during inflammation. Development of a detection method for 8-nitroguanine would provide an insight into the mechanism of inflammation-associated carcinogenesis and the assessment of carcinogenic risk in patients with inflammatory diseases. We established the method to produce highly sensitive and specific anti-8-nitroguanine rabbit polyclonal antibody, and detect 8-nitroguanine formation in biopsy specimens and animal tissues by immunohistochemistry. We have found that 8-nitroguanine is formed at the sites of carcinogenesis regardless of etiology, and proposed the possibility that 8-nitroguanine is a potential biomarker to evaluate the risk of inflammation-associated carcinogenesis. In this paper, we describe the procedures of these experiments and the application to clinical specimens and animal tissues.

Quercetin may suppress rat aberrant crypt foci formation by suppressing inflammatory mediators that influence proliferation and apoptosis

The flavonoid quercetin suppresses cell proliferation and enhances apoptosis in vitro. In this study, we determined whether quercetin protects against colon cancer by regulating the protein level of phosphatidylinositol 3-kinase (PI 3-kinase) and Akt or by suppressing the expression of proinflammatory mediators [cyclooxygenase (COX)-1, COX-2, inducible nitric oxide synthase (iNOS)] during the aberrant crypt (AC) stage. Forty male rats were randomly assigned to receive diets containing quercetin (0 or 4.5 g/kg) and injected subcutaneously with saline or azoxymethane (AOM; 2 times during wk 3 and 4). The colon was resected 4 wk after the last AOM injection and samples were used to determine high multiplicity AC foci (HMACF; foci with >4 AC) number, colonocyte proliferation and apoptosis by immunohistochemistry, expression of PI 3-kinase (p85 and p85alpha subunits) and Akt by immunoblotting, and COX-1, COX-2, and iNOS expression by real time RT-PCR. Quercetin-fed rats had fewer (P = 0.033) HMACF. Relative to the control diet, quercetin lowered the proliferative index (P = 0.035) regardless of treatment and diminished the AOM-induced elevation in crypt column cell number (P = 0.044) and expansion of the proliferative zone (P = 0.021). The proportion of apoptotic colonocytes in AOM-injected rats increased with quercetin treatment (P = 0.014). Levels of p85 and p85alpha subunits of PI 3-kinase and total Akt were unaffected by dietary quercetin. However, quercetin tended to suppress (P < 0.06) the expression of COX-1 and COX-2. Expression of iNOS was elevated by AOM injection (P = 0.0001). In conclusion, quercetin suppresses the formation of early preneoplastic lesions in colon carcinogenesis, which occurred in concert with reductions in proliferation and increases in apoptosis. It is possible the effects on proliferation and apoptosis resulted from the tendency for quercetin to suppress the expression of proinflammatory mediators.

Anti-NF-kappaB and anti-inflammatory activities of synthetic isothiocyanates: effect of chemical structures and cellular signaling

Many cancer chemopreventive agents have been associated with lower cancer risk by suppressing nuclear factor-kappaB (NF-kappaB) signaling pathways, which subsequently leads to attenuated pro-inflammatory mediators and activities. Of the natural compounds, the isothiocyanates (ITCs) found in cruciferous vegetables have received particular attention because of their potential anti-cancer effects. However, limited studies regarding the influence of ITCs structure on NF-kappaB transactivation and anti-inflammatory action are reported. In the present study, the anti-inflammatory potential of ten structurally divergent synthetic ITCs were evaluated in HT-29-N9 human colon cancer cells and RAW 264.7 murine macrophages. The effect of ITCs on the basal transcriptional activation of NF-kappaB and the inflammatory response to bacterial lipopolysaccharide (LPS) were assessed. The synthetic ITC analogs suppressed NF-kappaB-mediated pro-inflammatory gene transcription. Among the ITC analogs, tetrahydrofurfuryl isothiocyanate, methyl-3-isothiocyanatopropionate, 3-morpholinopropyl isothiocyanate and 3,4-methyelendioxybenzyl isothiocyanate showed stronger NF-kappaB inhibition as compared to the parent compound, phenylethyl isothiocyanate (PEITC). Molecular analysis revealed that several of the pro-inflammatory mediators and cytokines (iNOS, COX-2, IL-1beta, IL-6 and TNF-alpha) were reduced by ITCs, and correlated with the downregulation of NF-kappaB signaling pathways. Immunoblotting showed that ITCs suppressed LPS-induced phosphorylation and degradation of IkappaB alpha and decreased nuclear translocation of p65. In parallel, ITCs suppressed the phosphorylation of IkappaB kinase alpha/beta (IKKalpha/beta). Taken together, our findings provide the possibility that synthetic ITC analogs might have promising cancer chemopreventive potential, based on their stronger anti-NF-kappaB and anti-inflammatory activities, than the natural ITCs.

Damage to cellular and isolated DNA induced by a metabolite of aspirin

Aspirin has been proposed as a possible chemopreventive agent. On the other hand, a recent cohort study showed that aspirin may increase the risk for pancreatic cancer. To clarify whether aspirin is potentially carcinogenic, we investigated the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), which is correlated with the incidence of cancer, in cultured cells treated with 2,3-dihydroxybenzoic acid (2,3-DHBA), a metabolite of aspirin. 2,3-DHBA induced 8-oxodG formation in the PANC-1 human pancreatic cancer cell line. 2,3-DHBA-induced DNA single-strand breaks were also revealed by comet assay using PANC-1 cells. Flow cytometric analyses showed that 2,3-DHBA increased the levels of intracellular reactive oxygen species (ROS) in PANC-1 cells. The 8-oxodG formation and ROS generation were also observed in the HL-60 leukemia cell line, but not in the hydrogen peroxide (H(2)O(2))-resistant clone HP100 cells, suggesting the involvement of H(2)O(2). In addition, an hprt mutation assay supported the mutagenicity of 2,3-DHBA. We investigated the mechanism underlying the 2,3-DHBA-induced DNA damage using (32)P-labeled DNA fragments of human tumor suppressor genes. 2,3-DHBA induced DNA damage in the presence of Cu(II) and NADH. DNA damage induced by 2,3-DHBA was enhanced by the addition of histone peptide-6 [AKRHRK]. Interestingly, 2,3-DHBA and histone peptide-6 caused base damage in the 5'-ACG-3' and 5'-CCG-3' sequences, hotspots of the p53 gene. Bathocuproine, a Cu(I) chelator, and catalase inhibited the DNA damage. Typical hydroxyl radical scavengers did not inhibit the DNA damage. These results suggest that ROS derived from the reaction of H(2)O(2) with Cu(I) participate in the DNA damage. In conclusion, 2,3-DHBA induces oxidative DNA damage and mutations, which may result in carcinogenesis.

Aldose reductase deficiency in mice prevents azoxymethane-induced colonic preneoplastic aberrant crypt foci formation

Aldose reductase (AR; EC 1.1.1.21), an nicotinamide adenine dinucleotide phosphate-dependent aldo-keto reductase, has been shown to be involved in oxidative stress signaling initiated by inflammatory cytokines, chemokines and growth factors. Recently, we have shown that inhibition of this enzyme prevents the growth of colon cancer cells in vitro as well as in nude mice xenografts. Herein, we investigated the mediation of AR in the formation of colonic preneoplastic aberrant crypt foci (ACF) using azoxymethane (AOM)-induced colon cancer mice model. Male BALB/c mice were administrated with AOM without or with AR inhibitor, sorbinil and at the end of the protocol, all the mice were euthanized and colons were evaluated for ACF formation. Administration of sorbinil significantly lowered the number of AOM-induced ACF. Similarly, AR-null mice administered with AOM demonstrated significant resistance to ACF formation. Furthermore, inhibition of AR or knockout of AR gene in the mice significantly prevented AOM-induced expression of inducible nitric oxide synthase and cyclooxygenase-2 proteins as well as their messenger RNA. AR inhibition or knockdown also significantly decreased the phosphorylation of protein kinase C (PKC) beta2 and nuclear factor kappa binding protein as well as expression of preneoplastic marker proteins such as cyclin D1 and beta-catenin in mice colons. Our results suggest that AR mediates the formation of ACF in AOM-treated mice and thereby inhibition of AR could provide an effective chemopreventive approach for the treatment of colon cancer.

Zyflamend reduces LTB4 formation and prevents oral carcinogenesis in a 7,12-dimethylbenz[alpha]anthracene (DMBA)-induced hamster cheek pouch model

Aberrant arachidonic acid metabolism, especially altered cyclooxygenase and 5-lipoxygenase (LOX) activities, has been associated with chronic inflammation as well as carcinogenesis in human oral cavity tissues. Here, we examined the effect of Zyflamend, a product containing 10 concentrated herbal extracts, on development of 7,12-dimethylbenz[alpha]anthracene (DMBA)-induced inflammation and oral squamous cell carcinoma (SCC). A hamster cheek pouch model was used in which 0.5% DMBA was applied topically onto the left cheek pouch of male Syrian golden hamsters either three times per week for 3 weeks (short term) or 6 weeks (long term). Zyflamend was then applied topically at one of three different doses (25, 50 and 100 microl) onto the left cheek pouch three times for 1 week (short-term study) or chronically for 18 weeks. Zyflamend significantly reduced infiltration of inflammatory cells, incidence of hyperplasia and dysplastic lesions, bromodeoxyuridine-labeling index as well as number of SCC in a concentration-dependent manner. Application of Zyflamend (100 microl) reduced formation of leukotriene B(4) (LTB(4)) by 50% compared with DMBA-treated tissues. The reduction of LTB(4) was concentration dependent. The effect of Zyflamend on inhibition of LTB(4) formation was further confirmed with in vitro cell-based assay. Adding LTB(4) to RBL-1 cells, a rat leukemia cell line expressing high levels of 5-LOX and LTA(4) hydrolase, partially blocked antiproliferative effect of Zyflamend. This study demonstrates that Zyflamend inhibited LTB(4) formation and modulated adverse histopathological changes in the DMBA-induced hamster cheek pouch model. The study suggests that Zyflamend might prevent oral carcinogenesis at the post-initiation stage.

Sulforaphane suppressed LPS-induced inflammation in mouse peritoneal macrophages through Nrf2 dependent pathway

Sulforaphane (SFN) is a natural isothiocyanate that is present in cruciferous vegetables such as broccoli and cabbage. Previous studies have shown that SFN is effective in preventing carcinogenesis induced by carcinogens in rodents, which is related in part to its potent anti-inflammation properties. In the present study, we compared the anti-inflammatory effect of SFN on LPS-stimulated inflammation in primary peritoneal macrophages derived from Nrf2 (+/+) and Nrf2 (-/-) mice. Pretreatment of SFN in Nrf2 (+/+) primary peritoneal macrophages potently inhibited LPS-stimulated mRNA expression, protein expression and production of TNF-alpha, IL-1beta, COX-2 and iNOS. HO-1 expression was significantly augmented in LPS-stimulated Nrf2 (+/+) primary peritoneal macrophages by SFN. Interestingly, the anti-inflammatory effect was attenuated in Nrf2 (-/-) primary peritoneal macrophages. We concluded that SFN exerts its anti-inflammatory activity mainly via activation of Nrf2 in mouse peritoneal macrophages.

Genetic and epigenetic changes associated with cholangiocarcinoma: from DNA methylation to microRNAs

Cholangiocarcinomas are malignant epithelial liver tumors arising from the intra- and extra-hepatic bile ducts. Little is known about the molecular development of this disease, and very few effective treatment options are available. Thus, prognosis is poor. Genetic and epigenetic changes play an integral role in the neoplastic transformation of human cells to their malignant counterparts. This review summarizes some of the more prevalent genetic alterations (by microRNA expression) and epigenetic changes (hypermethylation of specific gene promoters) that are thought to contribute to the carcinogenic process in cholangiocarcinoma.

Carcinogenesis induced by foreign bodies

This review deals with the contemporary investigations of carcinogenesis induced by foreign bodies. The main attention is given to the interactions of macrophages with an implanted foreign body and their possible role in tumorigenesis.

Inducible nitric oxide synthase mediates retinal DNA damage in Goto-Kakizaki rat retina

PURPOSE

To examine the nitrosative and oxidative DNA damage induced by 8-nitroguanine and 8-hydroxy-2-deoxy guanosine (8-OHdG), and to determine the role played by inducible nitric oxide synthase (iNOS) in damage to DNA in the retina of the Goto-Kakizaki (GK) rat.

METHODS

Experiments were performed on GK rats, an animal model of spontaneous type 2 diabetes without obesity or visible diabetic vascular lesions. Immunohistochemistry was used to determine the retinal distribution of 8-nitroguanine, 8-OHdG, and iNOS in GK rats and control rats. The change in the expression of 8-nitroguanine and 8-OHdG in GK rats was also determined following an intravitreal injection of 1400W, an inhibitor of iNOS activity.

RESULTS

Immunohistochemical analysis showed that 8-nitroguanine and 8-OHdG were expressed strongly in the inner nuclear layer of GK retinas but only weakly in control retinas. This expression was correlated with an increase in the expression of iNOS in GK retinas, which was confirmed by the inhibition of iNOS activity by 1400W.

CONCLUSION

These findings demonstrate that iNOS plays a crucial role in nitrosative and oxidative DNA damage in GK rats, suggesting a retinal neurotoxic role of nitric oxide and superoxide in diabetic retinas.

Topical application of a bioadhesive black raspberry gel modulates gene expression and reduces cyclooxygenase 2 protein in human premalignant oral lesions

Reduced expression of proapoptotic and terminal differentiation genes in conjunction with increased levels of the proinflammatory and angiogenesis-inducing enzymes, cyclooxygenase 2 (COX-2) and inducible nitric oxide synthase (iNOS), correlate with malignant transformation of oral intraepithelial neoplasia (IEN). Accordingly, this study investigated the effects of a 10% (w/w) freeze-dried black raspberry gel on oral IEN histopathology, gene expression profiles, intraepithelial COX-2 and iNOS proteins, and microvascular densities. Our laboratories have shown that freeze-dried black raspberries possess antioxidant properties and also induce keratinocyte apoptosis and terminal differentiation. Oral IEN tissues were hemisected to provide samples for pretreatment diagnoses and establish baseline biochemical and molecular variables. Treatment of the remaining lesional tissue (0.5 g gel applied four times daily for 6 weeks) began 1 week after the initial biopsy. RNA was isolated from snap-frozen IEN lesions for microarray analyses, followed by quantitative reverse transcription-PCR validation. Additional epithelial gene-specific quantitative reverse transcription-PCR analyses facilitated the assessment of target tissue treatment effects. Surface epithelial COX-2 and iNOS protein levels and microvascular densities were determined by image analysis quantified immunohistochemistry. Topical berry gel application uniformly suppressed genes associated with RNA processing, growth factor recycling, and inhibition of apoptosis. Although the majority of participants showed posttreatment decreases in epithelial iNOS and COX-2 proteins, only COX-2 reductions were statistically significant. These data show that berry gel application modulated oral IEN gene expression profiles, ultimately reducing epithelial COX-2 protein. In a patient subset, berry gel application also reduced vascular densities in the superficial connective tissues and induced genes associated with keratinocyte terminal differentiation.

Reactive nitrogen species-dependent DNA damage in EBV-associated nasopharyngeal carcinoma: the relation to STAT3 activation and EGFR expression

Nasopharyngeal carcinoma (NPC) is strongly associated with Epstein-Barr virus (EBV) infection. Recently, reactive nitrogen and oxygen species are considered to participate in inflammation-related carcinogenesis through DNA damage. In our study, we obtained biopsy and surgical specimens of nasopharyngeal tissues from NPC patients in southern China, and performed double immunofluorescent staining to examine the formation of 8-nitroguanine, a nitrative DNA lesion and 8-oxo-7,8-dihydro-2'-deoxyguanosine, an oxidative DNA lesion, in these specimens. Strong DNA lesions were observed in cancer cells and inflammatory cells in stroma of NPC patients. Intensive immunoreactivity of iNOS was detected in the cytoplasm of 8-nitroguanine-positive cancer cells. DNA lesions and iNOS expression were also observed in epithelial cells of EBV-positive patients with chronic nasopharyngitis, although their intensities were significantly weaker than those in NPC patients. In EBV-negative subjects, no or little DNA lesions and iNOS expression were observed. EGFR and phosphorylated STAT3 were strongly expressed in cancer cells of NPC patients, but NF-kappaB was not expressed, suggesting that STAT3-dependent mechanism is important for NPC carcinogenesis. IL-6 was expressed mainly in inflammatory cells of nasopharyngeal tissues of EBV-infected patients. EBV-encoded RNAs (EBERs) and latent membrane protein 1 (LMP1) were detected in cancer cells from all EBV-infected patients. In vitro cell system, nuclear accumulation of EGFR was observed in LMP1-expressing cells, and IL-6 induced phosphorylated STAT3 and iNOS. These data suggest that nuclear accumulation of EGFR and STAT3 activation by IL-6 play the key role in iNOS expression and resultant DNA damage, leading to EBV-mediated NPC.