Immunohistochemical detection of 8-hydroxy-2'-deoxyguanosine in gallbladder epithelium of patients with pancreaticobiliary maljunction

Carcinogenic risk in the biliary epithelium of children with congenital biliary dilatation via the DNA damage repair pathway

PURPOSES

Congenital biliary dilatation (CBD) is a high-risk factor for biliary tract cancer (BTC). We previously reported the potential for carcinogenesis in the biliary epithelium of patients with CBD. In this study, we investigated potential carcinogenetic pathways, focusing on the DNA damage repair response, in children with CBD and compared the findings with those in adults.

METHODS

We enrolled 6 children with CBD and 10 adults with CBD without BTC who underwent extrahepatic bile duct resections, plus 4 control patients who underwent pancreaticoduodenectomy for non-biliary cancer. Levels of phosphorylated histone H2AX (γH2AX), MRE11, and Ku-70 in the biliary tract epithelium were evaluated by immunohistochemistry.

RESULTS

The levels of γH2AX, MRE11, and Ku-70 were significantly higher in the gallbladder epithelium and bile duct epithelium of both children and adults than in controls.

CONCLUSIONS

Children and adults with CBD might develop BTC via the DNA damage repair pathway, as evidenced by increased γH2AX, MRE11, and Ku-70 expression.

Gallbladder cancer

Gallbladder cancer (GBC) is the most common cancer of the biliary tract, characterized by a very poor prognosis when diagnosed at advanced stages owing to its aggressive behaviour and limited therapeutic options. Early detection at a curable stage remains challenging because patients rarely exhibit symptoms; indeed, most GBCs are discovered incidentally following cholecystectomy for symptomatic gallbladder stones. Long-standing chronic inflammation is an important driver of GBC, regardless of the lithiasic or non-lithiasic origin. Advances in omics technologies have provided a deeper understanding of GBC pathogenesis, uncovering mechanisms associated with inflammation-driven tumour initiation and progression. Surgical resection is the only treatment with curative intent for GBC but very few cases are suitable for resection and most adjuvant therapy has a very low response rate. Several unmet clinical needs require to be addressed to improve GBC management, including discovery and validation of reliable biomarkers for screening, therapy selection and prognosis. Standardization of preneoplastic and neoplastic lesion nomenclature, as well as surgical specimen processing and sampling, now provides reproducible and comparable research data that provide a basis for identifying and implementing early detection strategies and improving drug discovery. Advances in the understanding of next-generation sequencing, multidisciplinary care for GBC, neoadjuvant and adjuvant strategies, and novel systemic therapies including chemotherapy and immunotherapies are gradually changing the treatment paradigm and prognosis of this recalcitrant cancer.

Impact of DNA double-strand breaks on pancreaticobiliary maljunction carcinogenesis

BACKGROUND

Pancreaticobiliary maljunction (PBM) is a condition characterized by chronic inflammation due to refluxed pancreatic juice into the biliary tract that is associated with an elevated risk of biliary tract cancer. DNA double-strand breaks (DSBs) are considered the most serious form of DNA damage. DSBs are provoked by inflammatory cell damage and are recognized as an important oncogenic event in several cancers. This study used γ-H2AX, an established marker of DSB formation, to evaluate the impact of DNA damage on carcinogenesis in PBM.

METHODS

We investigated γ-H2AX expression immunohistochemically in gallbladder epithelium samples obtained from 71 PBM cases and 19 control cases.

RESULTS

Fourteen PBM cases with gallbladder adenocarcinoma were evaluated at non-neoplastic regions. A wide range of nuclear γ-H2AX staining was detected in all PBM and control specimens. γ-H2AX expression was significantly higher in PBM cases versus controls (median γ-H2AX-positive proportion: 14.4 % vs. 4.4 %, p = 0.001). Among the PBM cases, γ-H2AX expression was significantly higher in patients with carcinoma than in those without (median γ-H2AX-positive proportion: 21.4 % vs. 11.0 %, p = 0.031).

CONCLUSIONS

DSBs occurred significantly more abundantly in the PBM gallbladder mucosa, especially in the context of cancer, indicating an involvement in PBM-related carcinogenesis.

Oxidative Stress: A New Target for Pancreatic Cancer Prognosis and Treatment

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal types of tumors, and its incidence is rising worldwide. Survival can be improved when tumors are detected at an early stage; however, this cancer is usually asymptomatic, and the disease only becomes apparent after metastasis. Several risk factors are associated to this disease. Chronic pancreatitis, diabetes, and some infectious disease are the most relevant risk factors. Incidence of PDAC has increased in the last decades. It is hypothesized it could be due to other acquired risk habits, like smoking, high alcohol intake, and obesity. Indeed, adipose tissue is a dynamic endocrine organ that secretes different pro-inflammatory cytokines, enzymes, and other factors that activate oxidative stress. Reactive oxygen species caused by oxidative stress, damage DNA, proteins, and lipids, and produce several toxic and high mutagenic metabolites that could modify tumor behavior, turning it into a malignant phenotype. Anti-oxidant compounds, like vitamins, are considered protective factors against cancer. Here, we review the literature on oxidative stress, the molecular pathways that activate or counteract oxidative stress, and potential treatment strategies that target reactive oxygen species suitable for this kind of cancer.

Altered expression levels of occludin, claudin-1 and myosin light chain kinase in the common bile duct of pediatric patients with pancreaticobiliary maljunction

BACKGROUND

In pancreaticobiliary maljunction (PBM), the sphincter of Oddi can not control bile and pancreatic juice flow, which may lead to two-way reflux of bile and pancreatic juice, thus causing chronic inflammation, thickening, fibrosis and metaplasia of the common bile duct wall. These pathophysiological changes have been linked to disruption of the epithelium barrier in the common bile duct. We hypothesized that the expression of tight junction-associated proteins may be dysregulated in the common bile duct in PBM. In the current study, we sought to analyze the expression of tight junction-associated proteins in the common bile duct epithelium of pediatric patients with PBM.

METHODS

Specimens of the common bile duct were collected from 12 pediatric patients with PBM and 10 non-PBM controls. The expression of the tight junction-associated proteins occludin and claudin-1 in the epithelium was examined by immunohistochemistry. The Image-Pro Plus v. 6.0 image analysis software was used to calculate the mean qualifying score (MQS) of imunostained sections of common bile duct epithelium. Total protein extracts of common bile duct were analyzed by Western blotting assays to examine expression of occludin, claudin-1 and myosin light chain kinase (MLCK). Spearman correlation analysis was used to analyze the relation between MLCK and occludin, MLCK and claudin-1.

RESULTS

Immunostained sections of the common bile duct epithelium showed significantly higher MQS in pediatric patients than controls for occludin (44.11 ± 13.82 vs. 11.30 ± 9.58, P = 0.0034) and claudin-1 (63.44 ± 23.59 vs. 46.10 ± 7.84, P = 0.0384). Western blotting also showed significantly higher expression of occludin, claudin-1 and MLCK in the common bile duct of patients than of controls (P = 0.0023, 0.0015, 0.0488). Spearman correlation analysis showed that MLCK expression correlated positively with the expression of occludin (r s = 0.61538, P = 0.0032) and claudin-1 (r s = 0.7972, P = 0.0019).

CONCLUSIONS

Occludin and claudin-1 are up-regulated in the common bile duct epithelium of pediatric PBM patients. MLCK may be involved in the process of up-regulation of the tight junction-associated proteins in PBM.

Immunochemical detection of oxidatively damaged DNA

Oxidatively damaged DNA is implicated in various diseases, including neurodegenerative disorders, cancer, diabetes, cardiovascular and inflammatory diseases as well as aging. Several methods have been developed to detect oxidatively damaged DNA. They include chromatographic techniques, the Comet assay, (32)P-postlabelling and immunochemical methods that use antibodies to detect oxidized lesions. In this review, we discuss the detection of 8-oxo-7,8-dihydro-29-deoxyguanosine (8-oxodG), the most abundant oxidized nucleoside. This lesion is frequently used as a marker of exposure to oxidants, including environmental pollutants, as well as a potential marker of disease progression. We concentrate on studies published between the years 2000 and 2011 that used enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry to detect 8-oxodG in humans, laboratory animals and in cell lines. Oxidative damage observed in these organisms resulted from disease, exposure to environmental pollutants or from in vitro treatment with various chemical and physical factors.

Ala499Val (C>T) and Lys939Gln (A>C) polymorphisms of the XPC gene: their correlation with the risk of primary gallbladder adenocarcinoma--a case-control study in China

Genetic variations in the gene XPC may be associated with increased risk for gallbladder cancer (GBC). In this study, we detected two non-synonymous polymorphisms in XPC (Ala499Val and Lys939Gln) in 334 cases of GBC and 329 subjects of hospital-based age- and sex frequency-matched controls in China using a polymerase chain reaction-restriction fragment length polymorphism assay. Allelic association analysis for the two single-nucleotide polymorphisms (SNPs) showed that the risk allele T of Ala499Val was significantly associated with GBC [odds ratio (OR)=1.40, 95% confidence interval (CI): 1.11-1.76, P=0.005), with a population attributive risk of 5.3%. Logistic regression analysis revealed that Ala499Val CT heterozygote (OR=1.56, 95% CI: 1.13-2.14, P=0.002) and TT homozygote (OR=1.93, 95% CI: 1.04-3.55, P=0.048) had a significantly increased risk compared with CC homozygotes. Genetic analysis suggested that either the SNPs directly exert an effect or the linked functional gene impact of the disease trait likely follows an additive or dominant model. Gene interaction analysis demonstrated that the effects of XPC diplotypes (defined as the number of risk genotypes at the two SNP loci) were highly dependent on gallstone. The data from this case-control study indicated that XPC exonic variants contributed to the risk of GBC in this Chinese population.

Pancreaticobiliary maljunction and carcinogenesis to biliary and pancreatic malignancy

BACKGROUND

It is widely accepted that congenital choledochal cyst is associated with pancreaticobiliary maljunction (PBM). But, PBM is an independent disease entity from choledochal cyst. PBM is synonymous with "abnormal junction of the pancreaticobiliary ductal system", "anomalous arrangement of pancreaticobiliary ducts", "anomalous union of bilio-pancreatic ducts", etc. Cases with PBM not associated with biliary duct dilatation are often found, and these cases are frequently complicated gallbladder cancer. The Japanese Study Group of Pancreaticobiliary Maljunction was started in 1983, and defined diagnostic criteria and nationwide registration system of PBM cases was started. PBM is defined as a union of the pancreatic and biliary ducts which is located outside the duodenal wall. Bile and pancreatic juice reflux and regurgitate mutually.

BILIARY CARCINOGENESIS

The most bothersome problem is biliary carcinogenesis. Gallbladder cancers arise in 14.8% and bile duct cancers arise in 4.9%. The incidence of the gallbladder carcinoma of PBM without bile duct dilatation is 36.1%. Many investigators have tried to clarify the carcinogenic process, from various aspects. The biliary epithelia are injured by harmful substances, and in the course of repair, multiple alterations of oncogenes and tumor suppressor genes are followed, and they lead to carcinoma through multistage interaction. In the biliary epithelia of PBM, incidence and degree of hyperplasia are characteristic. K-ras gene mutations are observed in the cancerous as well as noncancerous lesions of biliary tract of PBM patients. Mutations of p53 gene and overexpression of p53 protein are also found in the cancerous and noncancerous lesions. These changes are called "hyperplasia-carcinoma sequence".

TREATMENT

Total excision of the extrahepatic bile duct with gallbladder followed by hepaticojejunostomy, Roux-en-Y, or end-to-side hepaticoduodenostomy are treatment of choice, even for cases with not dilated bile duct, because the incidence of cancer in the nondilated bile duct is not negligible, and genetic changes are seen in a nondilated bile duct.

hOGG1 Ser326Cys polymorphism and susceptibility to gallbladder cancer in a Chinese population

The human oxoguanine glycosylase 1(hOGG1) gene encodes a DNA glycosylase that is involved in excision repair of 8-OH-dG (8-hydroxy-2-deoxyguanine) from oxidatively-damaged DNA. To determine whether hOGG1 plays a role in the risk for adenocarcinoma of the gallbladder, we tested the association of this polymorphism with gallbladder cancer in a Chinese population-based, case control study of 204 cases and 209 controls. The subjects were genotyped with a polymerase chain reaction-restriction fragment length polymorphism (PCR-RELP) assay. The association between the genetic polymorphism of this gene and risk of the cancer was examined by using a multivariate analysis. We found that the distribution of hOGG1 Ser326Cys genotypes among controls (Ser/Ser, 37.3%; Ser/Cys, 53.6% and Cys/Cys, 9.1%) was significantly different from that among gallbladder cancer cases (Ser/Ser, 43.1%; Ser/Cys, 36.3% and Cys/Cys, 20.6%). Significantly increased risk for gallbladder cancer was both the hOGG1 326Ser/Cys (Odds ratio [OR] = 1.9, 95% confidence interval (CI) = 1.0-3.7) and hOGG1 326Cys/Cys genotypes (OR = 4.5, 95% CI = 1.1-22.4). We observed no statistically significant association between hOGG1 genotype and gallbladder cancer association in gallstone absence. In contrast, a near-significant increase in risk for gallbladder cancer was observed for gallstone presence with the hOGG1 326Ser/Cys genotype (OR = 2.2, CI = 1.4-3.5) whereas a significant increase in association for gallbladder cancer was observed for gallstone presence with the 326Cys/Cys genotype (OR = 6.1, CI = 2.1-27.2). These data corresponded with the fact that a significant trend towards increased association for gallbladder cancer was observed with potentially higher-risk hOGG1 genotypes in gallstone presence(p < 0.001, chi(2) trend test)but not in gallstone absence(p = 0.89, chi(2) trend test). A significant increase in risk for gallbladder cancer was observed for larger gallstone (those with stone diameters 2 cm or greater) with the hOGG1 326Ser/Cys(OR = 1.9, 95% CI = 1.1-2.9) and hOGG1 326Cys/Cys genotypes(OR = 5.9, 95% CI = 1.6-18.0). These data are consistent with the observation that a significant trend towards increased risk for gallbladder cancer was observed with potentially higher-risk hOGG1 genotypes in gallbladder cancer patients with larger gallstone (p < 0.001, chi(2) trend test). However, we observed no statistically significant association between hOGG1 genotype and gallbladder cancer risk in gallbladder cancer patients with smaller gallstone (those with stone diameters 2 cm smaller) (hOGG1 326Ser/Cys:OR = 2.2, 95% CI = 0.8-4.0; hOGG1 326Cys/Cys:OR = 2.9, 95% CI = 0.6-29.4; p = 0.06, chi(2) tread test). These results suggest that hOGG1 Ser326Cys polymorphism is associated with gallbladder cancer risk.

Oxidative DNA damage in peripheral leukocytes and its association with expression and polymorphisms of hOGG1: A study of adolescents in a high risk region for hepatocellular carcinoma in China

AIM: To study the oxidative DNA damage to adolescents of hepatocellular carcinoma (HCC) families in Guangxi Zhuang Autonomous Region, China.

METHODS: Peripheral leukocytes’ DNA 7,8-dihydro-8-oxoguanine (8-oxoG) and repair enzyme hOGG₁ were quantified by flow-cytometry. hOGG₁-Cys326Ser single nucleotide polymorphism (SNP) was distinguished by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) assay.

RESULTS: There was a positive correlation between 8-oxoG and repair enzyme hOGG₁ expression (P < 0.001). HCC children (n = 21) in Fusui county had a higher level of hOGG₁ (P < 0.01) and a lower level of 8-oxoG (P < 0.05) than the controls (n = 63) in Nanning city. Children in Nanning exposed to passive-smoking had a higher hOGG₁ expression (P < 0.05) than the non-exposers. 8-oxoG and hOGG₁ were negatively correlated with body mass index, while hOGG₁ was positively correlated with age. There was a peak of 8-oxoG level nearby the 12 year point. Individuals with the hOGG₁ 326Ser allele had a significantly marginal higher concentration of leukocyte 8-oxoG level than hOGG₁ 326Cys allele.

CONCLUSION: This is the first report using flow-cytometry to simultaneously quantify both the DNA oxidative damage and its repairing enzyme hOGG1. The results provide new insights towards a better understanding of the mechanisms of oxidative stress in a population highly susceptible to hepatocarcinogenesis.

Detection of oxidative DNA damage in oesophageal biopsies of patients with reflux symptoms and normal pH monitoring

BACKGROUND

Gastro-oesophageal reflux has been shown to induce oxidative DNA damage.

AIM

To determine whether oxidative DNA damage, detected in oesophageal biopsies by simple immunohistochemical staining, correlates with gastro-oesophageal reflux disease as determined by pH monitoring.

METHODS

The study included 47 patients with reflux symptoms who had oesophageal biopsy and 24-h pH monitoring studies performed within 3 months of each other with no variation in treatment in the time between the two procedures. Sections of formalin-fixed and paraffin-embedded oesophageal biopsies were stained for 8-hydroxy-2'-deoxyguanosine using the standard immunoperoxidase method. Positive nuclear immunoreactivity was considered to indicate oxidative DNA damage.

RESULTS

Seven (33%) of the 21 cases with normal 24-h pH monitoring results were negative for oxidative DNA damage, compared with only two (8%) of the 26 cases with abnormal 24-h pH results (P=0.058, two-sided Fisher's exact test). Five of the patients with normal 24-h pH results had oesophageal biopsies performed within 24 h of the monitoring procedure and, of these, four (80%) were positive for oxidative DNA damage, including a case in which both biopsy and 24-h pH monitoring were performed on the same day whilst the patient was on proton pump inhibitor therapy. All cases with normal 24-h pH results and positive oxidative DNA damage showed features of reflux on routine morphological evaluation.

CONCLUSIONS

Oxidative DNA damage can occur in the absence of acid reflux and despite adequate antisecretory therapy. This may indicate that other agents, such as bile, can induce oxidative DNA damage in an acid-suppressed environment. The significant discordance between oxidative DNA damage and 24-h pH results makes the determination of oxidative DNA damage a poor surrogate marker for 24-h pH monitoring.

Quantification of DNA adducts in individual cells by immunofluorescence: effects of variation in DNA conformation

Previously reported detection of melphalan-DNA adducts by immunofluorescent staining indicated considerable intercell variation in fluorescence levels. Investigations were undertaken to determine whether this variation reflected actual intercell differences in adduct levels. Melphalan-treated CCRF-CEM leukaemia cells were analysed by the trapped-in-agarose DNA immunostaining (TARDIS) method using fluorescein immunofluorescence and Hoechst dye-DNA fluorescence. Increasing the time of DNA denaturation in alkali affected the staining intensity, in agreement with known adduct properties, but failed to reduce intercell heterogeneity. To test the hypothesis that heterogeneity resulted from variation in levels of DNA strand breaks, drug-treated cells were exposed to ionising radiation. An increase in level and reduction in heterogeneity of immunofluorescence were observed, optimal at 10 Gy. When samples were irradiated after lysis, 1 Gy was optimal. At the optimal doses, irradiation before or after lysis resulted in similar levels of DNA strand breaks. Our conclusions are as follows: (a) There was no major intercell variation in the number of adducts other than from variation in DNA content. (b) Detection of melphalan, and possibly other adducts, by immunofluorescence can be markedly influenced by the level of strand breaks present in the DNA. (c) Samples analysed for melphalan adducts by immunofluorescence should be irradiated to minimise errors due to this factor.