The causes and prevention of cancer

Identification of clinically relevant protein targets in prostate cancer with 2D-DIGE coupled mass spectrometry and systems biology network platform

Prostate cancer (PCa) is the most common type of cancer found in men and among the leading causes of cancer death in the western world. In the present study, we compared the individual protein expression patterns from histologically characterized PCa and the surrounding benign tissue obtained by manual micro dissection using highly sensitive two-dimensional differential gel electrophoresis (2D-DIGE) coupled with mass spectrometry. Proteomic data revealed 118 protein spots to be differentially expressed in cancer (n = 24) compared to benign (n = 21) prostate tissue. These spots were analysed by MALDI-TOF-MS/MS and 79 different proteins were identified. Using principal component analysis we could clearly separate tumor and normal tissue and two distinct tumor groups based on the protein expression pattern. By using a systems biology approach, we could map many of these proteins both into major pathways involved in PCa progression as well as into a group of potential diagnostic and/or prognostic markers. Due to complexity of the highly interconnected shortest pathway network, the functional sub networks revealed some of the potential candidate biomarker proteins for further validation. By using a systems biology approach, our study revealed novel proteins and molecular networks with altered expression in PCa. Further functional validation of individual proteins is ongoing and might provide new insights in PCa progression potentially leading to the design of novel diagnostic and therapeutic strategies.

Locked nucleic acid hairpin detection of UV-induced DNA damage

The exposure of DNA to radiation and chemical insults leads to damage and disease. Thus, detection and understanding of DNA damage is important for elucidating molecular mechanisms of disease. However, current methods of DNA damage detection are either time-consuming, destroy the sample, or are too specific to be used for generic detection of damage. In this paper, we examine the sensitivity of different locked nucleic acid (LNA) hairpin probes for detecting UV-induced oligonucleotide damage to LNA composition, target concentration, and ionic strength. We also compare the selectivity of the LNA hairpin probe with a DNA molecular beacon (MB) hairpin probe for detecting DNA damage. Our results show that the selectivity of the LNA hairpin probe to UV-induced nucleic acid damage increases with increasing ionic strength of the buffer and decreases with increasing target concentration and with increasing LNA ratio.

Tissue hOGG1 genotype predicts bladder cancer prognosis: a novel approach using a peptide nucleic acid clamping method

BACKGROUND

Tissue genotyping is a more useful approach than using blood genomic DNA, because the tumor tissues can reflect the effects of somatic mutations in cancer. We investigated the value of the human oxoguanine glycosylase (hOGG1) genotype determined in tumor tissues as a prognostic indicator for bladder cancer (BC) using a novel technological approach.

METHODS

A total of 335 DNA samples from patients with primary BC were analyzed by peptide nucleic acid (PNA)-mediated real-time polymerase chain reaction (PCR) clamping to characterize the association between genetic polymorphisms within hOGG1 codon 326 and the clinicopathological characteristics of primary BC patients.

RESULTS

Tumor stage and number were significantly associated with the hOGG1 codon 326 genotype in nonmuscle invasive bladder cancer (NMIBC) patients. Compared with Cys326Ser and Ser326Ser, the Cys326Cys genotype had a greater progression-free survival benefit in patients with muscle invasive bladder cancer (MIBC). Univariate and multivariate Cox regression analyses indicated that the hOGG1 Cys326Cys genotype has a protective effect against progression in MIBC (hazard ratio, 0.360 and 0.314, respectively).

CONCLUSIONS

The hOGG1 tissue genotype is associated with aggressive clinicopathological features in NMIBC and with progression in patients with MIBC. Results suggest that the hOGG1 tissue genotype represents a promising marker for assessing BC prognosis in the clinical setting.

Xanthine oxidase inhibitory activities of extracts and flavonoids of the leaves of Blumea balsamifera

CONTEXT

Blumea balsamifera DC (Compositae) leaves have been recommended for use as a folk medicine in the treatment of various diseases related to urolithiasis in southeast Asia. Phytochemical studies of this plant revealed it contains four classes of flavonoids (e.g., flavonols, flavones, flavanones, and dihydroflavonol derivatives).

OBJECTIVE

In view of the broad pharmacological activity of flavonoids, this study was carried out to determine the xanthine oxidase (XO) inhibitory and enzymatically produced superoxide radical scavenging activity of different organic extracts and that of the isolated flavonoids from B. balsamifera leaves.

MATERIALS AND METHODS

The inhibitory activity of XO was assayed spectrophotometrically at 295 nm. The superoxide radicals scavenging activity was assessed by NBT reduction method, spectrophotometrically at 560 nm. A dose response curve was plotted for determining IC₅₀ values.

RESULTS

The methanol extract (IC₅₀ = 0.111 mg/mL) showed higher XO inhibitory activity than the chloroform (0.138 mg/mL) and pet-ether extracts (0.516 mg/mL). IC₅₀ values of scavenging of superoxide radicals for extracts decreased in the order of: methanol (0.063 mg/mL) > chloroform (0.092 mg/mL) > pet-ether (0.321 mg/mL). The XO inhibitory activity of the isolated flavonoids and reference compounds tested decreased in the order of: allopurinol > luteolin > quercetin > tamarixetin > 5,7,3',5'-tetrahydroxyflavanone > rhamnetin > luteolin-7-methyl ether > blumeatin > dihydroquercetin-4'-methyl ether > dihydroquercetin-7,4'-dimethyl ether > L-ascorbic acid.

DISCUSSION AND CONCLUSION

The results indicated that the flavone derivatives were more active than the flavonol derivatives. The flavanone derivatives were moderately active and the dihydroflavonol derivatives were the least. The higher flavonoid content of extracts contributed to their higher XO inhibitory activity.

Analysis of hOGG1 genotype as a prognostic marker for muscle invasive bladder cancer: a novel approach using peptide nucleic acid-mediated, real-time PCR clamping

OBJECTIVE

DNA damage repair mechanisms are a source of genetic mutation and are believed to play an important role in human cancer. Human 8-oxoguanine DNA glycosylase 1 (hOGG1) is involved in the recognition and repair of DNA damage. The value of the hOGG1 genotype as a prognostic indicator for bladder cancer (BC) was assessed using a novel technological approach.

MATERIALS AND METHODS

The association between genetic polymorphisms of hOGG1 codon 326 and clinicopathologic characteristics of 337 patients with BC was analyzed using peptide nucleic acid (PNA)-mediated real-time PCR clamping.

RESULTS

Tumor grade and size were significantly associated with the hOGG1 codon 326 genotype in non-muscle-invasive bladder cancer (NMIBC). The Cys326Cys polymorphism was significantly associated with progression and cancer specific survival in patients with muscle-invasive bladder cancer (MIBC). Multivariate Cox regression analysis indicated that the hOGG1 Cys326Cys polymorphism is associated with a protective effect on progression and a more dominant survival benefit than the Ser326Ser polymorphism in MIBC (hazard ratio 0.284 and 0.305, respectively).

CONCLUSIONS

Analysis of genotypes and clinical data for 337 BC patients indicates that the hOGG1 genotype may be a useful prognostic genetic marker for MIBC.

Cancer chemopreventive potential of volatile oil from black cumin seeds, Nigella sativa L., in a rat multi-organ carcinogenesis bioassay

Nigella sativa (N. sativa) is a herbal plant of the Ranunculaceae family that has been widely used for various medicinal and nutritional purposes. Volatile oil extracts along with its major constituents, such as thymoquinone, have recently attracted considerable attention for their antioxidant, immunoprotective and antitumor properties. The present study was conducted to assess the chemopreventive potential of crude oils in N. sativa on tumor formation using a well-established rat multi-organ carcinogenesis model featuring initial treatment with five different carcinogens. Post-initiation administration of 1000 or 4000 ppm N. sativa volatile oil in the diet of male Wistar rats for 30 weeks significantly reduced malignant and benign colon tumor sizes, incidences and multiplicities. The treatment also significantly decreased the incidences and multiplicities of tumors in the lungs and in different parts of the alimentary canal, particularly the esophagus and forestomach. Bromodeoxyuridine labeling indices, reflecting cell proliferation were significantly decreased in various organs and lesions after treatment with the two doses of N. sativa. The plasma levels of insulin growth factor, triglycerides and prostaglandin E2 were also altered. The findings show, for the first time, that N. sativa administration exerts potent inhibitory effects on rat tumor development and on cellular proliferation in multiple organ sites. In particular, the ability to significantly inhibit murine colon, lung, esophageal and forestomach tumors was demonstrated in the post-initiation phase, with no evidence of clinical side effects. The mechanisms are likely to be related to suppression of cell proliferation.

Oxidatively Damaged DNA: A Possible Antigenic Stimulus for Cancer Autoantibodies

Reactive oxygen species (ROS) are cytotoxic at higher concentration resulting in cell death, mutations, chromosomal aberrations or carcinogenesis. In this study DNA was modified by singlet oxygen and superoxide anion radicals generated by illumination of riboflavin under 365 nm UV-light. The modified DNA induced high titre antibodies in experimental animals. In enzyme immunoassay, serum antibodies from cancer patients (n = 34) showed a higher recognition of the modified DNA, as compared to the native form. This was further confirmed by the gel-shift assay. Immune IgG were used as a probe to detect oxidative lesions in the DNA of cancer patients. DNA isolated from lymphocytes of cancer patients proved to be an appreciable inhibitor of the experimentally induced antibodies against the ROS-DNA. This indicates the presence of oxidative lesions in the DNA obtained from cancer patients. The results show that ROS induced oxidative damage to DNA in cancer patients generate neo-epitopes that are alien for the immune system, resulting in autoantibody formation.

Metastasis: cancer cell's escape from oxidative stress

According to a "canonical" view, reactive oxygen species (ROS) positively contribute, in different ways, to carcinogenesis and to malignant progression of tumor cells: they drive genomic damage and genetic instability, transduce, as signaling intermediates, mitogenic and survival inputs by growth factor receptors and adhesion molecules, promote cell motility and shape the tumor microenvironment by inducing inflammation/repair and angiogenesis. Chemopreventive and tumor-inhibitory effects of endogenous, diet-derived or supplemented antioxidants largely support this notion. However, emerging lines of evidence indicates that tumor cells also need to defend themselves from oxidative damage in order to survive and successfully spread at distance. This "heresy" has recently received important impulse from studies on the role of antioxidant capacity in cancer stem cells self-renewal and resistance to therapy; additionally, the transforming activity of some oncogenes has been unexpectedly linked to their capacity to maintain elevated intracellular levels of reduced glutathione (GSH), the principal redox buffer. These studies underline the importance of cellular antioxidant capacity in metastasis, as the result of a complex cell program involving enhanced motility and a profound change in energy metabolism. The glycolytic switch (Warburg effect) observed in malignant tissues is triggered by mitochondrial oxidative damage and/or activation of redox-sensitive transcription factors, and results in an increase of cell resistance to oxidants. On the other hand, cytoskeleton rearrangement underlying cell motile and tumor-aggressive behavior use ROS as intermediates and are therefore facilitated by oxidative stress. Along this line of speculation, we suggest that metastasis represents an integrated strategy for cancer cells to avoid oxidative damage and escape excess ROS in the primary tumor site, explaning why redox signaling pathways are often up-regulated in malignancy and metastasis.

Micronucleus frequency in lymphocytes and 8-hydroxydeoxyguanosine level in plasma of women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) has recently been linked with genomic instability and DNA damage. The aim of this study was to test genomic damage in women PCOS, using two different methods for assessing damage in both chromosome and base level. The study was performed on 36 newly diagnosed women with PCOS and 29 healthy women as controls. The micronucleus (MN) analysis used as a biomarker of chromosomal/DNA damage was performed in peripheral lymphocytes by cytokinesis-block method. 8-hydroxydeoxyguanosine (8-OHdG) levels used as a reliable marker of oxidative DNA damage were measured in plasma using an ELISA kit. We found that MN frequencies obtained from lymphocytes of the women with PCOS were significantly higher than those of controls (4.1 +/- 1.0 vs. 2.1 +/- 0.6, P = 0.001), whereas, no differences in 8-OHdG level were found between the patients with PCOS and controls (0.5 +/- 0.3 vs. 0.5 +/- 0.2, P = 0.858). These findings indicate that women with PCOS seem to have increased genomic instability, but do not appear to have oxidative DNA damage despite the increased oxidative stress associated with PCOS.

Mechanisms of intestinal inflammation and development of associated cancers: lessons learned from mouse models

Chronic inflammation is strongly associated with approximately 1/5th of all human cancers. Arising from combinations of factors such as environmental exposures, diet, inherited gene polymorphisms, infections, or from dysfunctions of the immune response, chronic inflammation begins as an attempt of the body to remove injurious stimuli; however, over time, this results in continuous tissue destruction and promotion and maintenance of carcinogenesis. Here we focus on intestinal inflammation and its associated cancers, a group of diseases on the rise and affecting millions of people worldwide. Intestinal inflammation can be widely grouped into inflammatory bowel diseases (ulcerative colitis and Crohn's disease) and celiac disease. Long-standing intestinal inflammation is associated with colorectal cancer and small-bowel adenocarcinoma, as well as extraintestinal manifestations, including lymphomas and autoimmune diseases. This article highlights potential mechanisms of pathogenesis in inflammatory bowel diseases and celiac disease, as well as those involved in the progression to associated cancers, most of which have been identified from studies utilizing mouse models of intestinal inflammation. Mouse models of intestinal inflammation can be widely grouped into chemically induced models; genetic models, which make up the bulk of the studied models; adoptive transfer models; and spontaneous models. Studies in these models have lead to the understanding that persistent antigen exposure in the intestinal lumen, in combination with loss of epithelial barrier function, and dysfunction and dysregulation of the innate and adaptive immune responses lead to chronic intestinal inflammation. Transcriptional changes in this environment leading to cell survival, hyperplasia, promotion of angiogenesis, persistent DNA damage, or insufficient repair of DNA damage due to an excess of proinflammatory mediators are then thought to lead to sustained malignant transformation. With regards to extraintestinal manifestations such as lymphoma, however, more suitable models are required to further investigate the complex and heterogeneous mechanisms that may be at play.

Expression of p53 in leukoplakia and squamous cell carcinoma of the oral mucosa: correlation with expression of Ki67

Aim-To study p53 expression in relation to proliferative status in normal and nondysplastic, dysplastic and malignant lesions of the oral mucosa.Method-The standard avidin-biotin complex (ABC) immunohistochemical staining method was used to study the expression of p53 and Ki67 on frozen sections of oral leukoplakias and carcinomas.Results-Of the leukoplakia and carcinoma samples, 70% expressed p53 in over 5% of cells. In normal mucosa less than 5% of cells expressed p53. The proliferation index, as assessed by expression of Ki67, was highest in the malignant lesions (43%) and lowest in normal mucosa (11%). Statistical analysis revealed that expression of both p53 and Ki67 was correlated significantly with the histopathological stage of the tumour. However, expression of p53 was not correlated with that of Ki67. In leukoplakia lesions with proliferative features p53 immunostaining was less intense than in non-proliferative lesions; this difference was statistically significant.Conclusions-These results emphasise the potential of Ki67 and p53 as biomarkers of carcinogenesis in oral cancer and may also serve as intermediate points for cancer prevention programmes, such as the oral chemopreventive trials. Factors other than p53 may have a more important role in the deregulation of proliferation in pre-malignant oral lesions.

DNA damage and repair: fruit and vegetable effects in a feeding trial

Epidemiologic studies have examined the association between fruit and vegetable (F&V) consumption and the risk of cancer. Several cancer-preventive mechanisms have been proposed, such as antioxidant properties and modulation of biotransformation enzyme activities; both may be associated with reducing DNA damage and hence the mutation rate. We investigated, in a randomized, controlled, crossover feeding trial, the effect of 10 servings/day of botanically defined F&V for 2 wk on endogenous DNA damage; resistance to gamma -irradiation damage; and DNA repair capacity in lymphocytes, measured by the Comet assay. We also explored the association between the UGT1A1*28 polymorphism and serum bilirubin concentrations and DNA damage and repair measures. Healthy men (n = 11) and women (n = 17), age 20 to 40 yr, provided blood samples at the end of each feeding period. Overall, F&V did not affect DNA damage and repair measures in lymphocytes. The number of UGT1A1*28 alleles was inversely associated with sensitivity to gamma -irradiation exposure and DNA repair capacity, but a biological mechanism to explain this association is unclear. A larger sample size is needed to investigate the association between bilirubin concentrations and endogenous DNA damage. With inconsistent findings in the literature, additional dietary intervention studies on the effect of F&V on DNA damage and repair are needed.

Comparative in vitro antioxidant potential of different parts of Ipomoea asarifolia, Roemer & Schultes, Guiera senegalensis, J. F. Gmel and Anisopus mannii N. E. Brown

In this study, the radical scavenging capacity of Guiera senegalensis, Ipomoea asarifolia and Anisopus mannii were compared. The ascorbic acid equivalent of the stem bark (2.1 mM), leaves (2.05 mM) and root barks (1.89 mM) of Guiera senegalesis are much higher than any part of Ipomoea asarifolia or Anisopus manii. The stem bark, leaves and root bark of Guiera Senegalensis had IC50 of 15.4, 20.0 and 17.0 µL respectively, while corresponding parts of Ipomoea asarifolia showed IC50 of 50, 42 and 65 µL, respectively. These results suggest that Guiera senegalensis and Ipomoea asarifolia possess significant antioxidant capacities to warrant further detailed studies on the role of this property in their therapeutic effects.

Daily intake of antioxidants in relation to survival among adult patients diagnosed with malignant glioma

BACKGROUND

Malignant glioma is a rare cancer with poor survival. The influence of diet and antioxidant intake on glioma survival is not well understood. The current study examines the association between antioxidant intake and survival after glioma diagnosis.

METHODS

Adult patients diagnosed with malignant glioma during 1991-1994 and 1997-2001 were enrolled in a population-based study. Diagnosis was confirmed by review of pathology specimens. A modified food-frequency questionnaire interview was completed by each glioma patient or a designated proxy. Intake of each food item was converted to grams consumed/day. From this nutrient database, 16 antioxidants, calcium, a total antioxidant index and 3 macronutrients were available for survival analysis. Cox regression estimated mortality hazard ratios associated with each nutrient and the antioxidant index adjusting for potential confounders. Nutrient values were categorized into tertiles. Models were stratified by histology (Grades II, III, and IV) and conducted for all (including proxy) subjects and for a subset of self-reported subjects.

RESULTS

Geometric mean values for 11 fat-soluble and 6 water-soluble individual antioxidants, antioxidant index and 3 macronutrients were virtually the same when comparing all cases (n=748) to self-reported cases only (n=450). For patients diagnosed with Grade II and Grade III histology, moderate (915.8-2118.3 mcg) intake of fat-soluble lycopene was associated with poorer survival when compared to low intake (0.0-914.8 mcg), for self-reported cases only. High intake of vitamin E and moderate/high intake of secoisolariciresinol among Grade III patients indicated greater survival for all cases. In Grade IV patients, moderate/high intake of cryptoxanthin and high intake of secoisolariciresinol were associated with poorer survival among all cases. Among Grade II patients, moderate intake of water-soluble folate was associated with greater survival for all cases; high intake of vitamin C and genistein and the highest level of the antioxidant index were associated with poorer survival for all cases.

CONCLUSIONS

The associations observed in our study suggest that the influence of some antioxidants on survival following a diagnosis of malignant glioma are inconsistent and vary by histology group. Further research in a large sample of glioma patients is needed to confirm/refute our results.

Involvement of oxidatively damaged DNA and repair in cancer development and aging

DNA damage and DNA repair may mediate several cellular processes, like replication and transcription, mutagenesis and apoptosis and thus may be important factors in the development and pathology of an organism, including cancer. DNA is constantly damaged by reactive oxygen species (ROS) and reactive nitrogen species (RNS) directly and also by products of lipid peroxidation (LPO), which form exocyclic adducts to DNA bases. A wide variety of oxidatively-generated DNA lesions are present in living cells. 8-oxoguanine (8-oxoGua) is one of the best known DNA lesions due to its mutagenic properties. Among LPO-derived DNA base modifications the most intensively studied are ethenoadenine and ethenocytosine, highly miscoding DNA lesions considered as markers of oxidative stress and promutagenic DNA damage. Although at present it is impossible to directly answer the question concerning involvement of oxidatively damaged DNA in cancer etiology, it is likely that oxidatively modified DNA bases may serve as a source of mutations that initiate carcinogenesis and are involved in aging (i.e. they may be causal factors responsible for these processes). To counteract the deleterious effect of oxidatively damaged DNA, all organisms have developed several DNA repair mechanisms. The efficiency of oxidatively damaged DNA repair was frequently found to be decreased in cancer patients. The present work reviews the basis for the biological significance of DNA damage, particularly effects of 8-oxoGua and ethenoadduct occurrence in DNA in the aspect of cancer development, drawing attention to the multiplicity of proteins with repair activities.

C-reactive protein as an adverse prognostic marker for men with castration-resistant prostate cancer (CRPC): confirmatory results

We previously reported that higher serum concentrations of C-reactive protein (CRP) are associated with shorter survival in men with castration-resistant prostate cancer (CRPC). To confirm this finding in an independent data set, we used 119 CRPC patients enrolled in 6 phase II clinical trials and examined the relationship of CRP, alkaline phosphatase, hemoglobin, age, ECOG PS, and prostate specific antigen (PSA) with survival. Median follow-up was 19.7 months (0.9-98.5 months), and 89% have died. After analyzing the form of the risk function using the generalized additive model method, univariate and multivariate Cox proportional hazard models were used to assess associations between baseline individual categorical and continuous variables. Quartiles of CRP were: 0-1.0, 1.1-4.9, 5.0-17.0, and 17.1-311 mg/L. In a Cox multivariate model, log(2) (CRP) (HR 1.106, P = 0.013) as well as hemoglobin and alkaline phosphatase were independently associated with survival, confirming that higher CRP is associated with shorter survival in CRPC. Since CRP is a marker of inflammation, this finding suggests that inflammation may play an important role in the natural history of advanced prostate cancer. CRP is a readily measurable biomarker that has the potential to improve prognostic models and should be validated in a prospective clinical trial.

The role of dysregulated glucose metabolism in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the most lethal gynecologic cancer and also one of the most poorly understood. Other health issues that are affecting women with increasing frequency are obesity and diabetes, which are associated with dysglycemia and increased blood glucose. The Warburg Effect describes the ability of fast-growing cancer cells to preferentially metabolize glucose via anaerobic glycolysis rather than oxidative phosphorylation. Recent epidemiological studies have suggested a role for hyperglycemia in the pathogenesis of a number of cancers. If hyperglycemia contributes to tumour growth and progression, then it is intuitive that antihyperglycemic drugs may also have an important antitumour role. Preliminary reports suggest that these drugs not only reduce available plasma glucose, but also have direct effects on cancer cell viability through modification of molecular energy-sensing pathways. This review investigates the effect that hyperglycemia may have on EOC and the potential of antihyperglycemic drugs as therapeutic adjuncts.

Vinclozolin exposure in utero induces postpubertal prostatitis and reduces sperm production via a reversible hormone-regulated mechanism

Vinclozolin is an endocrine-disrupting chemical (EDC) that binds with high affinity to the androgen receptor (AR) and blocks the action of gonadal hormones on male reproductive organs. An alternative mechanism of action of Vinclozolin involves transgenerational effects on the male reproductive tract. We previously reported in utero Vinclozolin exposure-induced prostatitis (prostate inflammation) in postpubertal rats concurrent with down-regulation of AR and increased nuclear factor-kappaB activation. We postulated the male reproductive abnormalities induced by in utero Vinclozolin exposure could be reversed by testosterone supplementation, in contrast to the permanent modifications involving DNA methyltransferases (Dnmts) described by others. To test this hypothesis, we administered high-dose testosterone at puberty to Vinclozolin-treated rats and determined the effect on anogenital distance (AGD); testicular germ cell apoptosis, concentration of elongated spermatids, and the onset of prostatitis. Concurrently we examined Dnmt1, -3A, -3B, and -3L mRNA expression. Consistent with previous reports, in utero exposure to Vinclozolin significantly reduced AGD, increased testicular germ cell apoptosis 3-fold, reduced elongated spermatid number by 40%, and induced postpubertal prostatitis in 100% of exposed males. Administration of high-dose testosterone (25 mg/kg) at puberty normalized AGD, reduced germ cell apoptosis, and restored elongated spermatid number. Testosterone restored AR and nuclear factor-kappaB expression in the prostate and abolished Vinclozolin-induced prostatitis. Altered Dnmt expression was evident with in utero Vinclozolin exposure and was not normalized after testosterone treatment. These data demonstrate in utero Vinclozolin-induced male reproductive tract abnormalities are AR mediated and reversible and involve a mechanism independent of Dnmt expression.

Measuring antioxidant capacity using the ORAC and TOSC assays

Recent epidemiological studies have shown that there may be a link between oxidative stress and the development of several types of chronic diseases. Studies have also shown that diets rich in fruits and vegetables may decrease the incidence of cancer and other chronic diseases. The antioxidant activity of the phytochemicals these foods contain may be partially responsible for the decreased incidence of these diseases in people who regularly consume them. While there are several assays currently used to assess the antioxidant activity of phytochemicals and other antioxidant compounds, two are reviewed here in detail. The first is the oxygen radical absorbance capacity (ORAC) assay, which measures the decrease in fluorescence decay caused by antioxidants, and the second is the total oxyradical scavenging capacity (TOSC) assay, which measures the decrease in ethylene gas production caused by the inhibition of the thermal hydrolysis of ABAP (2,2'-Azobis(2-methyl-(propionamidine) dihydrochloride) by KMBA (alpha-keto-gamma-(methylthio)butyric acid sodium salt) in the presence of antioxidant compounds. These two assays are discussed here, with an in depth review of their methodology and correlation.

Prostate calculi in cancer and BPH in a cohort of Korean men: Presence of calculi did not correlate with cancer risk

Prostatic calculi are common and are associated with inflammation of the prostate. Recently, it has been suggested that this inflammation may be associated with prostate carcinogenesis. The aim of this study was to investigate the relationship between prostatic calculi and prostate cancer (PCa) in prostate biopsy specimens. We retrospectively analyzed 417 consecutive patients who underwent transrectal ultrasonography (TRUS) and prostate biopsies between January 2005 and January 2008. Based on the biopsy findings, patients were divided into benign prostatic hyperplasia and PCa groups. TRUS was used to detect prostatic calculi and to measure prostate volume. The correlations between PCa risk and age, serum total PSA levels, prostate volume, and prostatic calculi were analyzed. Patient age and PSA, as well as the frequency of prostatic calculi in the biopsy specimens, differed significantly between both the groups (P < 0.05). In the PCa group, the Gleason scores (GSs) were higher in patients with prostatic calculi than in patients without prostatic calculi (P = 0.023). Using multivariate logistic regression analysis, we found that patient age, serum total PSA and prostate volume were risk factors for PCa (P = 0.001), but that the presence of prostatic calculi was not associated with an increased risk of PCa (P = 0.13). In conclusion, although the presence of prostatic calculi was not shown to be a risk factor for PCa, prostatic calculi were more common in patients with PCa and were associated with a higher GS among these men.

Mastitis and the risk of breast cancer

BACKGROUND

Many cancers arise from sites of infection and inflammation. Results from animal studies indicate that inflammatory cells may facilitate neoplastic processes by orchestrating the tumor microenvironment. Little is known about the role of inflammation in the etiology of breast cancer. The aim of this study was to examine possible associations between a history of mastitis requiring hospitalization and subsequent risk of breast cancer.

METHODS

This cohort study of 2,577,565 women used data from several Swedish population-based registers, including the Inpatient Register and the Cancer Register. The risk of breast cancer was assessed by Poisson regression modeling.

RESULTS

We identified 8411 women in the Inpatient Register with a discharge diagnosis of mastitis. Of these, 106 had a subsequent diagnosis of breast cancer recorded in the Cancer Register. Compared with women who had no recorded mastitis, the incidence rate of breast cancer (regardless of laterality) was higher in women with mastitis, with an incidence rate ratio of 1.23 (95% confidence interval [CI] = 1.02-1.49) following adjustment for age, calendar time, age at first birth and parity. In the group of women among whom information on laterality was available for both the mastitis and the malignancy (n = 87), side of lesions corresponded for 52% (95% CI = 41%-62%), which is what could be expected by chance.

CONCLUSIONS

The overall risk of breast cancer was slightly elevated in women with a history of mastitis recorded in the Inpatient Register. The absence of a correlation between laterality of lesions, however, does not support a causal association between inflammation and the development of breast cancer.

Critical role of endogenous heme oxygenase 1 as a tuner of the invasive potential of prostate cancer cells

Prostate cancer (PCa) is the second leading cause of cancer-associated death in men. Inflammation has been recognized as a risk factor for this disease. Heme oxygenase 1 (HO-1), the inducible isoform of the rate-limiting enzyme in heme degradation, counteracts oxidative and inflammatory damage. Here, we investigated the regulated expression of HO-1 and its functional consequences in PCa. We studied the effect of genetic and pharmacologic disruption of HO-1 in the growth, invasion, and migration in androgen-sensitive (MDA PCa2b and LNCaP) and androgen-insensitive (PC3) PCa cell lines. Our results show that HO-1 levels are markedly decreased in PC3 compared with MDA PCa2b and LNCaP. Hemin treatment increased HO-1 at both protein and mRNA levels in all cell lines and decreased cell proliferation and invasion. Furthermore, overexpression of HO-1 in PC3 resulted in markedly reduced cell proliferation and migration. Accordingly, small interfering RNA-mediated silencing of HO-1 expression in MDA PCa2b cells resulted in increased proliferation and invasion. Using reverse transcription-quantitative PCR-generated gene array, a set of inflammatory and angiogenic genes were upregulated or downregulated in response to HO-1 overexpression identifying matrix metalloprotease 9 (MMP9) as a novel downstream target of HO-1. MMP9 production and activity was downregulated by HO-1 overexpression. Furthermore, PC3 cells stably transfected with HO-1 (PC3HO-1) and controls were injected into nu/nu mice for analysis of in vivo tumor xenograft phenotype. Tumor growth and MMP9 expression was significantly reduced in PC3HO-1 tumors compared with control xenografts. Taken together, these results implicate HO-1 in PCa cell migration and proliferation suggesting its potential role as a therapeutic target in clinical settings.

Chronic bacterial inflammation induces prostatic intraepithelial neoplasia in mouse prostate

Background:

Although the aetiology of prostate cancer remains unknown, we hypothesised that chronic bacterial insult has a major role in prostate carcinogenesis.

Methods:

Male C3H/HeOuJ mice, infected with phosphate-buffered saline or Escherichia coli bacteria, were killed at 5 days, or at 12 or 26 weeks. Harvested prostate tissues were evaluated for inflammatory responses and immunostained for neoplastic transformation markers.

Results:

All infected mice developed bacterial prostatitis. Control mice had no prostate infections or inflammation. Mice infected for 5 days showed foci of acute inflammation with infiltrating neutrophils and epithelial necrotic debris in the prostatic glandular lumen. All mice infected for 12 weeks had evidence of chronic inflammation with dense inflammatory infiltrates in the stroma. The prostatic epithelium showed varying degrees of atypical hyperplasia with increased epithelial cell layers and cytological atypia. At 26 weeks, the dysplastic changes were more pronounced and mimicked a prostatic intraepithelial neoplasia and high-grade dysplasia. Prostatic glands exhibiting reactive dysplasia had a stronger staining for oxidative DNA damage, increased epithelial cell proliferation, and a decrease in androgen receptor, GSTP1, p27^Kip1, and PTEN expression, when compared with control prostate glands.

Conclusion:

These data demonstrate that chronic inflammation induces focal prostatic glandular atypia and suggest a potential linkage between inflammation and prostatic neoplasia.

Increased DNA damage and oxidative stress in chickens with natural Marek's disease

Oxidative stress contributes to the accumulation of genomic abnormalities, prevents cellular apoptosis, and also mediates immunosuppression resulting in tumor formation. Marek's Disease provides excellent opportunities for the study of herpesvirus-induced tumors both in experimental- and natural conditions. The aim of this study was to examine the effects of Marek's Disease (MD) on basal levels of DNA strand breaks and on the oxidative-antioxidative status of chickens with MD. White-Lohmann hens-fifteen infected with Marek's Disease Virus (MDV) and fifteen healthy-of same age and sex were included in this study. MD infection was diagnosed via clinical signs, gross- and micro-pathological findings and also by detection of viral antigens in feather follicle epithelium by the indirect immunoperoxidase method. Compared with healthy controls, DNA damage was greater and levels of malondialdehyde (MDA) and plasma protein carbonyl (PCO), and plasma concentration of nitric oxide metabolites (NOx) higher in the MD group. Furthermore, total antioxidant activities (AOAs) were found lowered and glutathione (GSH) levels reduced in the MD group compared to the control group. Significantly positive correlation was found between DNA damage, MDA, PCO, and NOx in the MD group. DNA strand breaks were found negatively associated with AOA and GSH concentrations in the MD group. Our results demonstrated that oxidative stress markers and DNA damage substantially increased in chickens with MD, which indicated that increased DNA damage levels might be related to the increased oxidative stress and reduced antioxidant activity.

Antioxidant and Radical Scavenging Properties of Malva Sylvestris

Antioxidant capacity of the aqueous extract of Malva sylvestris was measured by its ability to scavenge the DPPH and superoxide anion radicals and to induce the formation of a phosphomolybdenum complex. Analysis of the extract, carried out by different chromatographic techniques, led to the isolation of eleven compounds: 4-hydroxybenzoic acid, 4-methoxybenzoic acid, 4-hydroxy-3-methoxybenzoic acid, 4-hydroxycinnamic acid, ferulic acid, methyl 2-hydroxydihydrocinnamate, scopoletin, N-trans-feruloyl tyramine, a sesquiterpene, (3 R,7 E)-3-hydroxy-5,7-megastigmadien-9-one, and (10 E,15 Z)-9,12,13-trihydroxyoctadeca-10,15-dienoic acid. The antioxidant activities of all these compounds are reported.

Anti-inflammatory drugs, antioxidants, and prostate cancer prevention

Prostate cancer may be the most common preventable cancer among men in the United States (US) and the rest of the developed world. Emerging insights into the molecular pathogenesis of prostate cancer suggest that damage to the prostate epithelium, potentially inflicted by a variety of exposures, triggers procarcinogenic inflammatory processes to promote disease development. In this milieu, the damaged epithelium may generate proliferative inflammatory atrophy (PIA) lesions, which may progress to prostatic intraepithelial neoplasia (PIN) or to prostate cancer. To attenuate prostatic carcinogenesis driven by chronic or recurrent prostate inflammation, rational chemoprevention has thus far featured anti-inflammatory drugs and antioxidants. Results from clinical trials of these approaches have been mixed, emphasizing the need for mechanistic studies of the contribution of inflammation to prostatic carcinogenesis, more extensive analyses of the pharmacology, including distribution of drugs into target tissue, and, rational development of biomarkers to identify patients that are most likely to respond to anti-inflammatory drugs and antioxidants (targeted chemoprevention), alone, or in combination (combination chemoprevention).

Red beet (Beta vulgaris L.) leaf supplementation improves antioxidant status in C57BL/6J mice fed high fat high cholesterol diet

The effect of diet supplemented with red beet (Beta vulgaris L.) leaf on antioxidant status of plasma and tissue was investigated in C57BL/6J mice. The mice were randomly divided into two groups after one-week acclimation, and fed a high fat (20%) and high cholesterol (1%) diet without (control group) or with 8% freeze-dried red beet leaf (RBL group) for 4 weeks. In RBL mice, lipid peroxidation determined as 2-thiobarbituric acid-reactive substances (TBARS value) was significantly reduced in the plasma and selected organs (liver, heart, and kidney). Levels of antioxidants (glutathione and β-carotene) and the activities of antioxidant enzyme (glutathione peroxidase) in plasma and liver were considerably increased, suggesting that antioxidant defenses were improved by RBL diet. Comet parameters such as tail DNA (%), tail extent moment, olive tail moment and tail length were significantly reduced by 25.1%, 49.4%, 35.4%, and 23.7%, respectively, in plasma lymphocyte DNA of RBL mice compared with control mice, and indicated the increased resistance of lymphocyte DNA to oxidative damage. In addition, the RBL diet controlled body weight together with a significant reduction of fat pad (retroperitoneal, epididymal, inguinal fat, and total fat). Therefore, the present study suggested that the supplementation of 8% red beet leaf in high fat high cholesterol diet could prevent lipid peroxidation and improve antioxidant defense system in the plasma and tissue of C57BL/6J mice.

Nrf2 signaling and cell survival

Nrf2:INrf2 acts as a sensor for oxidative/electrophilic stress. INrf2 serves as an adaptor to link Nrf2 to the ubiquitin ligase Cul3-Rbx1 complex that ubiquitinate and degrade Nrf2. Under basal conditions, cytosolic INrf2/Cul3-Rbx1 is constantly degrading Nrf2. When a cell encounters stress Nrf2 dissociates from the INrf2 and translocates into the nucleus. Oxidative/electrophilic stress induced modification of INrf2Cysteine151 and/or protein kinase C (PKC)-mediated phosphorylation of Nrf2Serine40 controls Nrf2 release from INrf2 followed by stabilization and nuclear translocation of Nrf2. Nrf2 binds to the antioxidant response element (ARE) and activates a myriad of genes that protect cells against oxidative/electrophilic stress and neoplasia. A delayed response of oxidative/electrophilic stress activates GSK-3beta that phosphorylates Fyn at unknown threonine residue(s). Phosphorylated Fyn translocates to the nucleus and phosphorylates Nrf2Tyrosine568 that leads to nuclear export and degradation of Nrf2. Prothymosin-alpha mediated nuclear translocation of INrf2 also degrades nuclear Nrf2. The degradation of Nrf2 both in cytosol and nuclear compartments rapidly brings down its levels to normal resulting in suppression of Nrf2 downstream gene expression. An auto-regulatory loop between Nrf2 and INrf2 controls their cellular abundance. Nrf2 regulates INrf2 by controlling its transcription, and INrf2 controls Nrf2 by degrading it. In conclusion, switching on and off of Nrf2 combined with promoting an auto-regulatory loop between them regulates activation/deactivation of defensive genes leading to protection of cells against adverse effects of oxidative and electrophilic stress and promote cell survival.

Lipid Peroxidation and Antioxidant Status in Stomach Cancer

BACKGROUND

Considerable evidences have linked oxidative damage and cancer. In this article, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx) activities, and malondialdehyde (MDA) and nitric oxide metabolites' levels (NO(x)) were investigated in patients with stomach cancer.

METHODS

All measurments were done by spectrophotometric techniques.

RESULTS

We observed a significant decrease in the activities of SOD and CAT in tumour tissues when compared with control tissues. The different of GSHPx activities and NO metabolite' levels were not statistically significant. MDA levels were significantly increased.

CONCLUSIONS

We conclude that increased MDA levels and decreased antioxidant enzyme activities can be valuable parameters in assessing the possible risk of cancer.

The fallopian tube: primary site of most pelvic high-grade serous carcinomas

Epithelial ovarian cancer is the most common cause of mortality from gynecologic malignancy, and most of epithelial cancers are of serous type. The site of origin of pelvic high-grade serous carcinoma has been the subject of debate for 60 years. This paper reviews the evidence that pelvic serous carcinoma originates from the fallopian tube mucosa and puts forward a theory that inflammation in the tube, caused by menstrual cytokines or infection, is critical to the genesis of these tumors. Other risk factors for pelvic serous carcinoma will be reviewed, including oral contraceptive use, parity, infertility, and tubal ligation.Studies were identified for this review by searching the English language literature in the MEDLINE database between the years 1995 and 2007 using the following keywords: fallopian tube neoplasia, ovarian serous adenocarcinoma, pregnancy, oral contraceptive, infertility, pelvic inflammatory disease, cytokines, menstruation, and tubal ligation, followed by an extensive review of bibliographies from articles found through the search.The clinical implications of this theory are discussed, and a change in surgical practice is recommended, with salpingectomy at the time of simple hysterectomy. This theory also has implications for the development of new methods of screening for pelvic serous carcinomas, as there are no screening methods that are currently available to find this form of cancer in an early stage. Inflammatory markers could be detected in the vagina from the fallopian tube indicating possible chronic inflammation and a risk factor for mutagenesis leading to serous carcinoma.

C-reactive protein haplotype is associated with high PSA as a marker of metastatic prostate cancer but not with overall cancer risk

Growing evidence points to a role for inflammation in prostate carcinogenesis. The significance of C-reactive protein (CRP), an inflammatory and innate immunity molecule, has not been evaluated thoroughly in prostate cancer (PC). In this study of 739 Finnish patients with PC and 760 healthy men, we evaluated the associations of CRP genotypes and haplotypes with total PC risk and PC progression, using prostate-specific antigen (PSA) as a marker of metastatic disease. Although the haplotype frequencies were similar in patients and controls, an association between haplotype ACCCA and patients' PSA levels was found. The carriers more often had a high PSA than non-carriers (P=0.0002) and the SNP rs2794521 A-allele and rs1800947 C-allele carriers had a higher PSA than non-carriers (P=0.009 and P=0.0004, respectively). A trend for a younger age at diagnosis was found among the carriers of ACCCA (P=0.07) and the rs1800947 C-allele (P=0.06), as well as a trend for the latter to have more likely metastases (P=0.06), but not after Bonferroni correction (α=0.00208). This is the first study to suggest association between PSA and CRP variants in PC and, therefore, further studies are warranted. CRP alleles previously found to protect against increased CRP levels are now suggested to be associated with metastatic PC, indicated by elevated PSA.

Polymorphisms in innate immunity genes and lung cancer risk in Xuanwei, China

The high incidence of lung cancer in Xuanwei County, China has been attributed to exposure to indoor smoky coal emissions that contain polycyclic aromatic hydrocarbons (PAHs). The inflammatory response induced by coal smoke components may promote lung tumor development. We studied the association between single nucleotide polymorphisms (SNPs) in genes involved in innate immunity and lung cancer risk in a population-based case-control study (122 cases and 122 controls) in Xuanwei. A total of 1,360 tag SNPs in 149 gene regions were included in the analysis. FCER2 rs7249320 was the most significant SNP (OR: 0.30; 95% CI: 0.16-0.55; P: 0.0001; false discovery rate value, 0.13) for variant carriers. The gene regions ALOX12B/ALOX15B and KLK2 were associated with increased lung cancer risk globally (false discovery rate value <0.15). In addition, there were positive interactions between KLK15 rs3745523 and smoky coal use (OR: 9.40; P-interaction = 0.07) and between FCER2 rs7249320 and KLK2 rs2739476 (OR: 10.77; P-interaction = 0.003). Our results suggest that genetic polymorphisms in innate immunity genes may play a role in the genesis of lung cancer caused by PAH-containing coal smoke. Integrin/receptor and complement pathways as well as IgE regulation are particularly noteworthy.

Identification of oxidative stress-induced tyrosine phosphorylated proteins by immunoprecipitation and mass spectrometry

Oxidative stress is the result of an increased presence of reactive oxygen species (ROS) in cells and is able to promote, among others, protein and lipid oxidation, DNA damage, mutagenesis, oncogenic activation, or inhibition of tumour suppression, resulting in pathological processes such as myocardial dysfunction or carcinogenesis. External treatment of cells with oxidants such as H2O2 or high intracellular levels of ROS has been shown to trigger protein tyrosine phosphorylation. This occurs, at least in part, through the oxidation of reactive cysteine groups in protein tyrosine phosphatases resulting in an inhibition of their activities. Herein, we focus on the characterization of stress-induced protein tyrosine phosphorylation events in a cellular model of human mammary luminal epithelial cells (HB4a cells) stimulated with H2O2, in an attempt to better understand the mechanisms by which oxidative stress could promote such phenomena. Thus, immunoprecipitation with anti-phosphotyrosine antibodies and mass spectrometry have allowed us to identify a number of phosphorylated proteins that respond to oxidative stress and thereby further probe the effects of these changes on cellular function.

Effects of dietary supplementation with red-pigmented leafy lettuce (Lactuca sativa) on lipid profiles and antioxidant status in C57BL/6J mice fed a high-fat high-cholesterol diet

The present study was undertaken to assess the beneficial effects of a daily consumption of 8 % freeze-dried red-pigmented leafy lettuce (Lactuca sativa) on CVD. C57BL/6J mice were fed a high-fat high-cholesterol diet supplemented with or without red-pigmented leafy lettuce for 4 weeks. The present results showed that the red-pigmented leafy lettuce-supplemented diet significantly decreased the level of total and LDL-cholesterol and TAG in the plasma of the mice. The atherosclerotic index was calculated to be 46 % lower in the mice fed with the lettuce diet compared with the control diet. Lipid peroxidation measured by 2-thiobarbituric acid-reactive substances was markedly reduced in the plasma, liver, heart and kidney of the mice fed the lettuce diet. The content of antioxidants (total glutathione and beta-carotene) was significantly increased by lettuce supplementation. The antioxidant defence system by antioxidant enzymes including glutathione S-transferase, glutathione peroxidase, glutathione reductase, superoxide dismutase and paraoxanase in blood or liver tissues was also increased, and showed the improved oxidative stress in the mice fed the lettuce diet. The measurement of tail DNA (%), tail extent moment and olive tail moment indicated that the lettuce diet increased the resistance of hepatocyte and lymphocyte DNA to oxidative damage. The present study showed that the supplementation of a high-cholesterol high-fat diet with 8 % red-pigmented leafy lettuce resulted in an improvement of plasma cholesterol and lipid levels, prevention of lipid peroxidation and an increase of the antioxidant defence system and, therefore, could contribute to reduce the risk factors of CVD.

A systemic review of the roles of n-3 fatty acids in health and disease

Attention to the role of n-3 long-chain fatty acids in human health and disease has been continuously increased during recent decades. Many clinical and epidemiologic studies have shown positive roles for n-3 fatty acids in infant development; cancer; cardiovascular diseases; and more recently, in various mental illnesses, including depression, attention-deficit hyperactivity disorder, and dementia. These fatty acids are known to have pleiotropic effects, including effects against inflammation, platelet aggregation, hypertension, and hyperlipidemia. These beneficial effects may be mediated through several distinct mechanisms, including alterations in cell membrane composition and function, gene expression, or eicosanoid production. A number of authorities have recently recommended increases in intakes of n-3 fatty acids by the general population. To comply with this recommendation a variety of food products, most notably eggs, yogurt, milk, and spreads have been enriched with these fatty acids. Ongoing research will further determine the tissue distribution, biological effects, cost-effectiveness, and consumer acceptability of such enriched products. Furthermore, additional controlled clinical trials are needed to document whether long-term consumption or supplementation with eicosapentaenoic acid/docosahexaenoic acid or the plant-derived counterpart (alpha-linolenic acid) results in better quality of life.

Glutathione peroxidases in different stages of carcinogenesis

Cancer cells produce high amounts of reactive oxygen species (ROS) and evade apoptosis. Hydroperoxides support proliferation, invasion, migration and angiogenesis, but at higher levels induce apoptosis, thus being pro- and anti-carcinogenic. Accordingly, glutathione peroxidases (GPxs) regulating hydroperoxide levels might have dual roles too. GPx1, clearly an antioxidant enzyme, is down-regulated in many cancer cells. Its main role would be prevention of cancer initiation by ROS-mediated DNA damage. GPx2 is up-regulated in cancer cells. GPx1/GPx2 double knockout mice develop colitis and intestinal cancer. However, GPx2 knockdown cancer cells grow better in vitro and in vivo probably reflecting the physiological role of GPx2 in intestinal mucosa homeostasis. GPx2 counteracts COX-2 expression and PGE(2) production, which explains its potential to inhibit migration and invasion of cultured cancer cells. Overexpression of GPx3 inhibits tumor growth and metastasis. GPx4 is decreased in cancer tissues. GPx4-overexpressing cancer cells have low COX-2 activity and tumors derived therefrom are smaller than from control cells and do not metastasize. Collectively, GPxs prevent cancer initiation by removing hydroperoxides. GPx4 inhibits but GPx2 supports growth of established tumors. Metastasis, but also apoptosis, is inhibited by all GPxs. GPx-mediated regulation of COX/LOX activities may be relevant to early stages of inflammation-mediated carcinogenesis.

Incorporation of 5-chlorocytosine into mammalian DNA results in heritable gene silencing and altered cytosine methylation patterns

Cytosine methylation patterns are essential for the proper control of gene expression in higher vertebrates. Although alterations in methylation patterns are frequently observed in human tumors, neither the mechanisms for establishing methylation patterns during normal development nor the mechanisms leading to pathological alterations of methylation patterns are currently known. While epidemiological studies have implicated inflammation in cancer etiology, a mechanistic link has yet to be established. Investigations of inflammation-mediated DNA damage may have provided important new insights. Our in vitro studies revealed that the inflammation-mediated DNA damage product, 5-chlorocytosine, could direct fraudulent methylation of previously unmethylated CpG sites. The purpose of this study was to recapitulate our in vitro findings by introducing 5-chlorocytosine residues into the DNA of replicating mammalian cells and to examine its impact on gene expression and cytosine methylation patterns. CHO-K1 cells hemizygous for the hprt gene were electroporated with the triphosphates of cytosine [2'-deoxycytidine-5'-triphosphate (dCTP)], 5-methylcytosine [5-methyl-2'-deoxycytidine-5'-triphosphate (MedCTP)] and 5'-chloro-2'-deoxycytidine-5'-triphosphate (CldCTP), and then selected with 6-thioguanine for silencing the hprt gene. Both modified nucleotides, MedCTP and CldCTP, but not unmodified dCTP, silenced hprt gene expression. Subsequent bisulfite pyrosequencing of CpG sites within the hprt promoter region of the selected cells confirmed hypermethylation, although global methylation levels as measured by gas chromatography-mass spectrometry did not change. Modified nucleotide-induced gene silencing could be reversed with 5-aza-2'-deoxycytidine indicating an epigenetic rather than mutagenic alteration. These results provide further evidence that the inflammation damage product 5-chlorocytosine could be a link between inflammation and cancer development.