8-hydroxyguanine and Carcinoma--Hepatocellular

Aflatoxin, which leads to formation of carcinogen-DNA adducts as well as oxidized DNA, is a well-known risk factor for development of hepatocellular carcinoma. The aim of the present study was to investigate if the chemopreventive agent oltipraz had an effect on DNA oxidation measured as oxidized guanine derivatives in urine among healthy individuals living in a region of China at high risk of exposure to aflatoxin and development of hepatocellular carcinoma. Two hundred thirty-three healthy residents of Qidong, PRC, were randomized to 8 weeks treatment with placebo, oltipraz 125 mg daily, or oltipraz 500 mg weekly, with a subsequent 8-week follow-up period. Urine samples were collected as overnight voids. Samples collected 4 weeks into the treatment period and 6 weeks into the follow-up period were analyzed for oxidized guanine derivatives with a HPLC-MS/MS method. A repeated-measures analysis of variance showed no significant differences between the randomization groups regarding changes in oxidized guanine derivatives. In the present double-blind, randomized, placebo-controlled trial performed among healthy individuals, oltipraz had no major effect on oxidative DNA damage. Mechanisms other than prevention of oxidative DNA damage may be of higher importance when oltipraz is used as a chemopreventive agent in humans.

Topics: Anticarcinogenic Agents; Biomarkers; Carcinoma, Hepatocellular; China; DNA; Guanine; Humans; Liver Neoplasms; Oxidation-Reduction; Oxidative Stress; Placebos; Pyrazines; Thiones; Thiophenes

Oxidative stress contributes to tumourigenesis by altering gene expression. One accompanying modification, 8-oxoguanine (o

Topics: Animals; Carcinogenesis; Carcinoma, Hepatocellular; Glioma; Guanine; Liver Neoplasms; Mice; MicroRNAs; Oxidation-Reduction

Aflatoxin B1 (AFB1) and microcystin-LR (MC-LR) simultaneously exist in polluted food and water in humid and warm areas, and each has been reported to be genotoxic to liver and associated with hepatocellular carcinoma (HCC). However, the genotoxic effects of the two biotoxins in combination and potential mechanism remain unknown. We treated the human hepatic cell line HL7702 with AFB1 and MC-LR together at different ratios, examined their genotoxic effects using micronuclei and comet assays, and evaluated the possible mechanism by measuring oxidative stress markers and DNA base excision repair (BER) genes. Our data show that co-exposure to AFB1 and MC-LR significantly increased DNA damage compared with AFB1 or MC-LR alone as measured by the levels of both micronuclei and tail DNA. Meanwhile, AFB1 and MC-LR co-exposure showed biphasic effects on ROS production, and a gradual trend towards increased Glutathione (GSH) levels and activity of Catalase (CAT) and Superoxide Dismutase (SOD). Furthermore, MC-LR, with or without AFB1, significantly down-regulated the expression of the base excision repair (BER) genes 8-oxoguanine glycosylase-1 (OGG1) and X-ray repair cross complementing group 1 (XRCC1). AFB1 and MC-LR in combination upregulated the expression of the BER gene apurinic/apyrimidinic endonuclease 1 (APE1), whereas either agent alone had no effect. In conclusion, our studies show that MC-LR exacerbates AFB1-induced genotoxicity and we report for the first time that this occurs through effects on oxidative stress and the deregulation of DNA base excision repair genes.

Topics: Aflatoxin B1; Animals; Carcinoma, Hepatocellular; Catalase; Comet Assay; DNA; DNA Damage; DNA Repair; DNA-(Apurinic or Apyrimidinic Site) Lyase; Glutathione; Guanine; Hepatocytes; Humans; Liver Neoplasms; Marine Toxins; Microcystins; Oxidative Stress; Superoxide Dismutase; Toxicity Tests

HBx is strongly associated with hepatocellular carcinoma development through transcription factor activation and reactive oxygen species (ROSs) production. However, the exact role of HBx during hepatocellular carcinogenesis is not fully understood. Recently, it was reported that C-terminal truncated HBx is associated with tumor metastasis. In the present study, we confirmed that the C-terminal region of HBx is required for ROS production and 8-oxoguanine (8-oxoG) formation, which is considered as a reliable biomarker of oxidative stress. These results suggest ROS production induced by the C-terminal region of HBx leads to mitochondrial DNA damage, which may play a role in HCC development.

Topics: Blotting, Western; Carcinoma, Hepatocellular; Cell Transformation, Neoplastic; DNA Damage; DNA, Mitochondrial; Gene Expression Regulation; Guanine; Humans; Immunoenzyme Techniques; Liver Neoplasms; Mitochondria; Oxidative Stress; Reactive Oxygen Species; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Trans-Activators; Tumor Cells, Cultured; Viral Regulatory and Accessory Proteins

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

Topics: Adolescent; Adult; Age Factors; Biomarkers; Body Mass Index; Carcinoma, Hepatocellular; China; DNA Damage; DNA Glycosylases; Female; Flow Cytometry; Genotype; Guanine; Humans; Leukocytes; Liver Neoplasms; Male; Multivariate Analysis; Oxidative Stress; Polymorphism, Single Nucleotide; Risk Factors