The expression of 8-hydroxydeoxyguanosine in oesophageal tissues and tumours

The Oxidative Damage and Inflammation Mechanisms in GERD-Induced Barrett's Esophagus

Barrett's esophagus is a major complication of gastro-esophageal reflux disease and an important precursor lesion for the development of Barrett's metaplasia and esophageal adenocarcinoma. However, the cellular and molecular mechanisms of Barrett's metaplasia remain unclear. Inflammation-associated oxidative DNA damage could contribute to Barrett's esophagus. It has been demonstrated that poly(ADP-ribose) polymerases (PARPs)-associated with ADP-ribosylation plays an important role in DNA damage and inflammatory response. A previous study indicated that there is inflammatory infiltration and oxidative DNA damage in the lower esophagus due to acid/bile reflux, and gastric acid could induce DNA damage in culture esophageal cells. This review will discuss the mechanisms of Barrett's metaplasia and adenocarcinoma underlying oxidative DNA damage in gastro-esophageal reflux disease patients based on recent clinical and basic findings.

The Mechanisms for the Association of Cancer and Esophageal Dysmotility Disorders

BACKGROUND

Achalasia and other esophageal dysmotility disorders mimicking achalasia can be associated with cancer. This study aimed to review the main mechanisms for which cancer may develop in esophageal dysmotility disorder patients.

METHODS

A narrative review was performed.

RESULTS

The mechanism for developing squamous cell carcinoma and adenocarcinoma are discussed. Besides, achalasia-like syndromes related to familial KIT-gene mutation and pseudoachalasia are discussed.

CONCLUSIONS

Knowing the main mechanism for which achalasia can be related to cancer is essential for clinicians to conduct the proper investigation, surveillance, and treatment.

The antioxidant response in Barrett's tumorigenesis: A double-edged sword

Esophageal adenocarcinoma (EAC) is the dominant form of esophageal malignancies in the United States and other industrialized countries. The incidence of EAC has been rising rapidly during the past four decades. Barrett's esophagus (BE) is the main precancerous condition for EAC, where a metaplastic columnar epithelium replaces normal squamous mucosa of the lower esophagus. The primary risk factor for BE and EAC are chronic gastroesophageal reflux disease (GERD), obesity and smoking. During the BE-dysplasia-EAC sequence, esophageal cells are under a tremendous burden of accumulating reactive oxygen species (ROS) and oxidative stress. While normal cells have intact antioxidant machinery to maintain a balanced anti-tumorigenic physiological response, the antioxidant capacity is compromised in neoplastic cells with a pro-tumorigenic development antioxidant response. The accumulation of ROS, during the neoplastic progression of the GERD-BE-EAC sequence, induces DNA damage, lipid peroxidation and protein oxidation. Neoplastic cells adapt to oxidative stress by developing a pro-tumorigenic antioxidant response that keeps oxidative damage below lethal levels while promoting tumorigenesis, progression, and resistance to therapy. In this review, we will summarize the recent findings on oxidative stress in tumorigenesis in the context of the GERD-BE-EAC process. We will discuss how EAC cells adapt to increased ROS. We will review APE1 and NRF2 signaling mechanisms in the context of EAC. Finally, we will discuss the potential clinical significance of applying antioxidants or NRF2 activators as chemoprevention and NRF2 inhibitors in treating EAC patients.

Mutational signature distribution varies with DNA replication timing and strand asymmetry

BACKGROUND

DNA replication plays an important role in mutagenesis, yet little is known about how it interacts with other mutagenic processes. Here, we use somatic mutation signatures-each representing a mutagenic process-derived from 3056 patients spanning 19 cancer types to quantify the strand asymmetry of mutational signatures around replication origins and between early and late replicating regions.

RESULTS

We observe that most of the detected mutational signatures are significantly correlated with the timing or direction of DNA replication. The properties of these associations are distinct for different signatures and shed new light on several mutagenic processes. For example, our results suggest that oxidative damage to the nucleotide pool substantially contributes to the mutational landscape of esophageal adenocarcinoma.

CONCLUSIONS

Together, our results indicate an interaction between DNA replication, the associated damage repair, and most mutagenic processes.

Increased Oxidative Stress in the Proximal Stomach of Patients with Barrett's Esophagus and Adenocarcinoma of the Esophagus and Esophagogastric Junction

OBJECTIVES: Oxidative stress (OS) is an essential element in the pathogenesis of Barrett’s esophagus (BE) and its transformation to adenocarcinoma (EAC). The state of OS in the proximal stomach of patients with BE and EAC is unknown. Isoprostanes are a specific marker of OS not previously used to determine OS from BE/EAC tissue samples. PATIENTS AND METHODS: OS was measured in 42 patients with BE (n = 9), EAC (n = 9), or both (n = 24) and 15 control patients. A STAT-8-Isoprostane EIA Kit served to identify 8-Isoprostanes (8-IP), and a Glutathione Assay Kit was used to measure glutathione reduced form (GSH) and glutathione oxidized form. An OxiSelect Oxidative DNA Damage ELISA Kit (8-OHdG) served to measure 8-OH-deoxyguanosine. RESULTS: The 8-IP (P = .039) and 8-OHdG (P = .008) levels were higher, and the GSH level lower (P = .031), in the proximal stomach of the study group than in that of the controls. Helicobacter pylori infection was present in 8% of the study patients. CONCLUSIONS: In the proximal stomach of BE and EAC patients, OS was elevated and antioxidative capacity was reduced. This finding suggests that the gastroesophageal reflux causing BE also induces oxidative stress in the proximal stomach and may contribute to the development of cancer in the proximal stomach and gastric cardia.

Serum calprotectin: a new potential biomarker for thyroid papillary carcinoma

The aim of this study was to evaluate serum calprotectin levels and oxidative stress status in patients with papillary thyroid carcinoma (PTC) and the changes in their levels after total thyroidectomy. The study involved 30 patients with PTC and 30 healthy controls. Blood samples were obtained from the PTC patients before and 1 month after the operation. Preoperative and postoperative serum samples from PTC patients and healthy controls were analysed for calprotectin, total antioxidant status (TAS), total oxidant status (TOS) and lipid hydroperokside (LOOH). The preoperative calprotectin, TOS, OSI and LOOH levels of the patients with PTC were significantly higher compared to those of the control group (p < 0.001, for each). The levels of calprotectin decreased significantly in patients with PTC after the operation (p < 0.001), while TAS, TOS and OSI levels remained unchanged (p = 0.313, p = 0.085 and p = 0.163, respectively). Preoperative serum calprotectin levels were positively correlated with TOS, OSI and LOOH levels and negatively correlated with TAS levels in patients with PTC. In conclusion, serum calprotectin levels is increased in patients with PTC, and calprotectin is positively correlated with TOS and LOOH. Serum calprotectin levels is significantly decreased after total thyroidectomy.

A review of the application of inflammatory biomarkers in epidemiologic cancer research

Inflammation is a facilitating process for multiple cancer types. It is believed to affect cancer development and progression through several etiologic pathways, including increased levels of DNA adduct formation, increased angiogenesis, and altered antiapoptotic signaling. This review highlights the application of inflammatory biomarkers in epidemiologic studies and discusses the various cellular mediators of inflammation characterizing the innate immune system response to infection and chronic insult from environmental factors. Included is a review of six classes of inflammation-related biomarkers: cytokines/chemokines, immune-related effectors, acute-phase proteins, reactive oxygen and nitrogen species, prostaglandins and cyclooxygenase-related factors, and mediators such as transcription factors and growth factors. For each of these biomarkers, we provide a brief overview of the etiologic role in the inflammation response and how they have been related to cancer etiology and progression within the literature. We provide a discussion of the common techniques available for quantification of each marker, including strengths, weaknesses, and potential pitfalls. Subsequently, we highlight a few under-studied measures to characterize the inflammatory response and their potential utility in epidemiologic studies of cancer. Finally, we suggest integrative methods for future studies to apply multifaceted approaches to examine the relationship between inflammatory markers and their roles in cancer development.

Oxidative DNA damage in human esophageal cancer: clinicopathological analysis of 8-hydroxydeoxyguanosine and its repair enzyme

Both internal and external oxidative stresses act on DNA and can induce carcinogenesis. 8-hydroxydeoxyguanosine (8-OHdG) is an indicator of oxidative stress and it leads to transversion mutations and carcinogenesis. 8-OHdG is excision-repaired by 8-OHdG DNA glycosylase (OGG1). The purpose of this study is to clarify the effect of oxidative DNA damage and repair enzymes on esophageal carcinogenesis. The levels of 8-OHdG and OGG1 were immunohistochemically evaluated in resected specimens, including squamous cell carcinoma (SCC) in 97 patients with esophageal cancer. Higher levels of 8-OHdG in normal esophageal epithelium were associated with a higher smoking index (P = 0.0464). The 8-OHdG level was higher in cancerous areas than in normal epithelia (P = 0.0061), whereas OGG1 expression was weaker in cancerous areas than in normal epithelia (P < 0.0001). An increase of OGG1 expression in normal epithelium was observed as 8-OHdG levels increased (P = 0.0011). However, this correlation was not observed in cancerous areas. High OGG1 expression in the cytoplasm was related to deeper tumors (P = 0.0023), node metastasis (P = 0.0065) and stage (P = 0.0019). Oxidative DNA damage, which is attributable to smoking as well as disturbances in DNA repair systems, appears to be closely related to esophageal carcinogenesis and its progression.

Oxidized extracellular DNA as a stress signal that may modify response to anticancer therapy

An increase in the levels of oxidation is a universal feature of genomic DNA of irradiated or aged or even malignant cells. In case of apoptotic death of stressed cells, oxidized DNA can be released in circulation (cfDNA). According to the results of the studies performed in vitro by our group and other researchers, the oxidized cfDNA serves as a biomarker for a stress and a stress signal that is transmitted from the "stressed" area i.e. irradiated cells or cells with deficient anti-oxidant defenses to distant (bystander) cells. In recipient cells, oxidized DNA stimulates biosynthesis of ROS that is followed up by an increase in the number of single strand and double strand breaks (SSBs and DSBs), and activation of DNA Damage Response (DDR) pathway. Effects of oxidized DNA are considered similar to that of irradiation. It seems that downstream effects of irradiation, in part, depend on the release of oxidized DNA fragments that mediate the effects in distant cells. The responses of normal and tumor cell to oxidized DNA may differ. It seems that tumor cells are more sensitive to oxidized DNA-dependent DNA damage, while developing pronounced adaptive response. This may suggest that in chemotherapy or irradiation-treated human body, the release of oxidized DNA from dying cancer cells may give a boost to remaining malignant cells by augmenting their survival and stress resistance. Further studies of the effects of oxidized DNA in both in vitro and in vivo systems are warranted.

Oxidative DNA damage in Barrett mucosa: correlation with telomeric dysfunction and p53 mutation

BACKGROUND

Barrett esophagus develops in a scenario of chronic inflammation, linked to free radical formation and oxidative DNA damage. Eight-hydroxydeoxyguanosine, the main oxidative DNA adduct, is partially repaired by a glycosylase (OGG1) whose polymorphism is associated to a reduced repair capacity. Telomeres are particularly prone to oxidative damage, which leads to shortening and cell senescence, while elongation, by telomerase activity, is linked to cell immortalization and cancer. Limited data are available on this point with respect to Barrett esophagus. This study aimed to evaluate the link among 8-hydroxydeoxyguanosine, OGG1 polymorphism, telomerase activity, telomere length, and p53 mutation in Barrett progression.

METHODS

Forty consecutive patients with short- and long-segment Barrett esophagus and 20 controls with gastroesophageal reflux disease without Barrett esophagus were recruited. Analysis of biopsy samples was undertaken to study 8-hydroxydeoxyguanosine levels, OGG1 polymorphism, telomerase activity, and telomere length. Serum samples were obtained for p53 mutation.

RESULTS

Controls had significantly lower levels of 8-hydroxydeoxyguanosine and telomerase activity, with normal telomere length and no p53 mutation. In short-segment Barrett esophagus, 8-hydroxydeoxyguanosine levels were higher and telomeres underwent significant shortening, with stimulation of telomerase activity but no p53 mutations. In long-segment Barrett esophagus, 8-hydroxydeoxyguanosine reached maximal levels, with telomere elongation, and 42 % of the patients showed p53 mutation.

CONCLUSIONS

In Barrett patients, with disease progression, oxidative DNA damage accumulates, causing telomere instability, telomerase activation, and, in a late phase, mutations in the p53 gene, thus abrogating its activity as the checkpoint of proliferation and apoptosis, and facilitating progression to cancer.

Determination of low urinary 8-hydroxy-2`-deoxyguanosine excretion with capillary electrophoresis and molecularly imprinted monolith solid phase microextraction

As a sensitive biomarker, the level of 8-hydroxy-2`-deoxyguanosine (8-OHdG) indicates the extent of DNA oxidative damage of subject. However its determination in human urine is confounded by trace content and a complex matrix. In this study, a new approach of solid phase microextraction (SPME) coupled to capillary electrophoresis and electrochemical detection was developed with molecularly imprinted monolithic column as extraction sorbent. The tailor made monolith exhibited high extraction efficiency with the enrichment factor 73 for 8-OHdG owing to its special porous structure and inherent selectivity. Under optimal conditions, appreciable sensitivity had been achieved with a limit of detection of 2.61 nmol/L (signal/noise=3) and a limit of quantification of 8.63 nmol/L (signal/noise=10), respectively. As an alternative of precise 8-OHdG determination, wide range linearity had been achieved with 0.01-1.50 μmol/L and RSDs with 3.70% for migration time and 4.80% for peak current (10-1000 nmol/L). 106 samples with relative low extents of DNA oxidative damage were collected and analyzed which including coke plant workers, traffic policemen, taxi drivers and healthy students. Elevated urinary 8-OHdG excretions of subjects may correlate to working condition, occupational exposure, or lifestyle.

Oxidative Stress and DNA Damage in Human Gastric Carcinoma: 8-Oxo-7'8-dihydro-2'-deoxyguanosine (8-oxo-dG) as a Possible Tumor Marker

We characterized the oxidative stress (OS) status by the levels of reduced/oxidized glutathione (GSH/GSSG), malondialdehyde (MDA) and the mutagenic base 8-oxo-7′8-dihydro-2′-deoxyguanosine (8-oxo-dG) in human gastric carcinoma (HGC) samples and compared the results with normal tissue from the same patients. We also analyzed 8-oxo-dG in peripheral mononuclear cells (PMNC) and urine from healthy control subjects and in affected patients in the basal state and one, three, six, nine and twelve months after tumor resection. The levels of DNA repair enzyme mRNA expression (hOGG1, RAD51, MUYTH and MTH1) were determined in tumor specimens and compared with normal mucosa. Tumor specimens exhibited increased levels of MDA and 8-oxo-dG compared with normal gastric tissue. GSH levels were also increased, while GSSG levels remained stable. DNA repair enzyme mRNA expression was induced in the tumor tissues. Levels of 8-oxo-dG were significantly elevated in both urine and PMNC of gastric cancer patients compared with healthy controls. After gastrectomy, the levels of the damaged base in urine and PMNC decreased progressively to values close to those found in the healthy population. The high levels of 8-oxo-dG in urine may be related to the increased induction of DNA repair activity in tumor tissue, and the changes observed after tumor resection support its potential use as a tumor marker.

8-hydroxy-2' -deoxyguanosine (8-OHdG): A critical biomarker of oxidative stress and carcinogenesis

There is extensive experimental evidence that oxidative damage permanently occurs to lipids of cellular membranes, proteins, and DNA. In nuclear and mitochondrial DNA, 8-hydroxy-2' -deoxyguanosine (8-OHdG) or 8-oxo-7,8-dihydro-2' -deoxyguanosine (8-oxodG) is one of the predominant forms of free radical-induced oxidative lesions, and has therefore been widely used as a biomarker for oxidative stress and carcinogenesis. Studies showed that urinary 8-OHdG is a good biomarker for risk assessment of various cancers and degenerative diseases. The most widely used method of quantitative analysis is high-performance liquid chromatography (HPLC) with electrochemical detection (EC), gas chromatography-mass spectrometry (GC-MS), and HPLC tandem mass spectrometry. In order to resolve the methodological problems encountered in measuring quantitatively 8-OHdG, the European Standards Committee for Oxidative DNA Damage was set up in 1997 to resolve the artifactual oxidation problems during the procedures of isolation and purification of oxidative DNA products. The biomarker 8-OHdG or 8-oxodG has been a pivotal marker for measuring the effect of endogenous oxidative damage to DNA and as a factor of initiation and promotion of carcinogenesis. The biomarker has been used to estimate the DNA damage in humans after exposure to cancer-causing agents, such as tobacco smoke, asbestos fibers, heavy metals, and polycyclic aromatic hydrocarbons. In recent years, 8-OHdG has been used widely in many studies not only as a biomarker for the measurement of endogenous oxidative DNA damage but also as a risk factor for many diseases including cancer.

Effect of alpha-tocopherol, N-acetylcysteine and omeprazole on esophageal adenocarcinoma formation in a rat surgical model

We previously demonstrated that oxidative stress subsequent to gastroesophageal reflux is an important driving force of esophageal adenocarcinoma (EAC) formation in the esophagogastroduodenal anastomosis (EGDA) rat model. This study investigated the possible tumor inhibitory effects of 2 antioxidants, alpha-tocopherol (389 and 778 ppm), N-acetylcysteine (NAC, 500 and 1,000 ppm), and their combination (389 and 500 ppm, respectively), as well as an antacid therapeutic agent, omeprazole (1,400 ppm). The rats were fed experimental diets 2 weeks after EGDA. All the animals were sacrificed 40 weeks after EGDA and the esophagi were harvested for histopathological examination. alpha-Tocopherol dose-dependently decreased the incidence of EAC (p = 0.03), with 778 ppm alpha-tocopherol reducing the incidence of EAC to 59% (16/27) in comparison with 84% (26/31) in the control group (p = 0.04). Supplementation of alpha-tocopherol also increased the serum concentration of alpha-tocopherol. NAC at 500 and 1,000 ppm did not significantly decrease EAC incidence; however, the combination of alpha-tocopherol 389 ppm and NAC 500 ppm significantly reduced the incidence of EAC to 55% (15/27) (p = 0.02). alpha-Tocopherol alone or in combination with NAC significantly reduced the number of infiltrating cells positively stained for 4-hydroxynonenal. Omeprazole showed only a slight nonsignificant inhibitory effect at the dose given. Our results suggest that supplementation with alpha-tocopherol inhibits the development of EAC in the rat EGDA model and similar inhibitory effect can be achieved when a lower dose of alpha-tocopherol is used in combination with NAC.

Proton pump inhibitor therapy in gastro-oesophageal reflux disease decreases the oesophageal immune response but does not reduce the formation of DNA adducts

BACKGROUND

Chronic oesophageal inflammation and related oxidative stress are important in the pathogenesis of erosive oesophagitis (EO) and its malignant progression.

AIM

To study the effect of proton pump inhibitors (PPIs) on oesophageal cellular immune response and oxidative damage in EO patients.

METHODS

Forty gastro-oesophageal reflux disease (GERD) patients [non-erosive reflux disease (NERD): 15, EO: 25] were included, after 7 days off antisuppressive drugs. EO patients were randomized to 20-mg rabeprazole once daily for either 4 or 8 weeks with baseline and follow-up endoscopy with distal oesophageal biopsies. T lymphocytes, macrophages and mast cells were quantified by immunohistochemistry. DNA adducts were measured by analysis of 8-oxo-deoxyguanosine levels.

RESULTS

Erosive oesophagitis patients had more T lymphocytes and CD8(+) T lymphocytes in squamous epithelium than NERD patients (P = 0.001, P = 0.002, respectively). Levels of DNA adducts between both groups were, however, not different (P = 0.99). Four- and eight-week rabeprazole treatment in EO patients resulted in a significant decrease in number of T lymphocytes and CD8(+) T lymphocytes (all P < 0.05). PPIs did not, however, affect levels of DNA adducts.

CONCLUSIONS

Short-term PPI therapy in EO patients reduces the oesophageal cellular immune response, but does not change oxidative damage. PPI therapy may therefore not be effective in reducing the risk of oesophageal cancer in GERD patients.