8-hydroxy-2--deoxyguanosine and Lymphoma

Oxidative stress combined with nullity of xenobiotic metabolizing GSTT1/GSTM1/CYP2E1 genes may increase the susceptibility of agricultural workers to adverse health effects including cancer. The present study was conducted to determine; the prevalence of polymorphisms in GSTM1, GSTT1 and CYP2E1 genes, serum 8-hydroxy-2'-deoxygunosine levels, and the role of these markers in risk of cancer among agricultural workers occupationally exposed to pesticides.. A total of 360 participants, of which 180 belonging to farming group diagnosed with leukemia (n=60), lymphoma (n=60) and breast cancers (n=60), 90 in non-farming group diagnosed with similar cancers and the other 90 as healthy controls with neither history of occupational exposure nor diagnosed with any type of cancers were recruited. Following the questionnaire survey, serum 8-OHdG and genetic polymorphisms in the three genes were determined using ELISA and PCR methods respectively.. The results of the study revealed that farm workers carrying GSTT1 null genotype had increased risk for lymphoma (OR = 5.34; 95% CI = 1.80-15.82) and breast cancer (OR=4.04; 95% CI = 1.24-13.07). For farm workers carrying GSTM1 null genotype, the risk was six-fold for breast cancer (OR = 6.88; 95% CI =1.88-25.99). Further, there found a significant difference between 8-OHdG and nullity of CYP2E1 among the farm workers diagnosed with leukemia.. The findings of the present study suggest that the polymorphisms in detoxifying genes among farm workers occupationally exposed to pesticides and the oxidative stress may likely be responsible for triggering the mechanism of malignancy.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Breast Neoplasms; Cytochrome P-450 CYP2E1; Drug-Related Side Effects and Adverse Reactions; Farmers; Female; Humans; Leukemia; Lymphoma; Pesticides; Polymorphism, Genetic; Xenobiotics

H-ferritin (HF) is a core subunit of the iron storage protein ferritin and is related to the pathogenesis of malignant diseases. HF overexpression is present in human hematologic malignancies, suggesting that HF overexpression may contribute to the development of hematologic cancers. However, in vivo evidence that HF is directly linked to hematologic tumorigenesis has not yet been shown. In this study, we show that transgenic (tg) mice overexpressing the human HF gene (hHF-tg) developed aggressive radiation-induced thymic lymphoma/leukemia (TL) compared with wild-type (WT) mice, providing evidence that HF overexpression promotes leukemia/lymphomagenesis. Fractionated X-irradiation of hHF-tg mice caused a higher incidence and earlier onset of TL compared with WT mice. Immunological and pathological features of TLs were similar in both groups. However, proliferative activity of hHF-tg lymphoma cells was higher than that of WT lymphoma cells, and microarray analyses revealed that some leukemia/lymphoma-related genes were differentially expressed in hHF-tg TLs compared with WT TLs. To investigate whether cell damage induced by irradiation is related to leukemia/lymphomagenesis, we evaluated apoptotic levels in the thymus and bone marrow (BM) of hHF-tg and WT groups after fractionated X-irradiation. Apoptosis was augmented in the hHF-tg BM, but not in the thymus, compared with the WT BM, suggesting a possible linkage between increased BM apoptosis by HF overexpression and accelerated radiation-induced TL development. Our findings indicate that HF overexpression is closely related to the development of leukemia/lymphoma, which could have implications for the prevention of malignant hematologic diseases.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Apoferritins; Apoptosis; Deoxyguanosine; Flow Cytometry; Humans; Leukemia, Radiation-Induced; Lymphoma; Mice; Mice, Inbred C57BL; Mice, Transgenic; Survival Rate; X-Rays

Potassium bromate (KBrO3) is a well-established rodent kidney carcinogen and its oxidising activity is considered to be a significant factor in its mechanism of action. Although it has also been shown to be clearly genotoxic in a range of in vivo and in vitro test systems, surprisingly, it is not readily detected in several cell lines using the standard alkaline Comet assay. However, previous results from this laboratory demonstrated huge increases in tail intensity by modifying the method to include incubation with either human 8-oxodeoxyguanosine DNA glycosylase-1 (hOGG1) or bacterial formamidopyrimidine DNA glycosylase (FPG) indicating that, as expected, significant amounts of 8-oxodeoxyguanosine (8-OHdG) were induced. The purpose of this work, therefore, was to investigate why KBrO3, in contrast to other oxidising agents, gives a relatively poor response in the standard Comet assay. Results confirmed that it is a potent genotoxin in mouse lymphoma L5178Y cells inducing micronuclei and mutation at the tk and hprt loci at relatively non-cytotoxic concentrations. Subsequent time-course studies demonstrated that substantial amounts of 8-OHdG appear to remain in cells 24h after treatment with KBrO3 but result in no increase in frank stand breaks (FSB) even though phosphorylated histone H2AX (gamma-H2AX) antibody labelling confirmed the presence of double-strand breaks. Using bromodeoxyuracil (BrdU) incorporation together with measured increases in cell numbers, L5178Y cells also appeared to go through the cell cycle with unrepaired hOGG1-recognisable damage. Since unrepaired 8-OHdG can give rise to point mutations through G:C-->T:A transversions, it was also surprising that mutation could not be detected at the Na+/K+ATPase locus as determined by ouabain resistance. Some increases in strand breakage could be seen in the Comet assay by increasing the unwinding time, but only at highly toxic concentrations and to a much smaller extent than would be expected from the magnitude of the other genotoxic responses. It was considered unlikely that these anomalous observations were due to the inability of L5178Y cells to recognise 8-OHdG because these cells were shown to express mOGG1 and have functional cleavage activity at the adducted site. It appears that the responses of L5178Y cells to KBrO3 are complex and differ from those induced by other oxidising agents.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Bromates; Cell Line, Tumor; Comet Assay; Deoxyguanosine; Histones; Lymphoma; Mice; Micronucleus Tests; Mutagens; Mutation

In order to elucidate the involvement of metallothionein (MT) in radiation carcinogenesis, we examined the susceptibility of MT-I/II null mice to carcinogenesis and oxidative DNA damage resulting from X-irradiation. Eight-week-old female MT-I/II null mice and wild-type mice were exposed to whole-body X-irradiation at doses of 1.0, 1.5 or 2.0 Gy once a week for 6 weeks. Incidence of thymic lymphoma was determined at 24 weeks after the first exposure to X-irradiation. The frequency of thymic lymphomas induced by X-irradiation (at 1.5 and 2.0 Gy) was significantly higher in MT-I/II null mice than in wild-type mice. In addition, although the levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) were increased in the serum and urine of both strains of mice 24 hr after exposure to a single bout of whole body X-irradiation, these increases were significantly greater in the MT-I/II null mice than in the wild-type mice. Thus, the present results suggest that MT plays a protective role against carcinogenesis and oxidative DNA damage caused by X-irradiation.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Deoxyguanosine; DNA Damage; Female; Lymphoma; Metallothionein; Mice; Mice, Knockout; Neoplasms, Radiation-Induced; Thymus Neoplasms; X-Rays

The evolution of mitochondrial oxidative phosphorylation was studied during cancer induction in a model of thymic radiolymphomagenesis in C57BL/Ka mice. During the preneoplastic period, thymuses displayed an increase of the cytochrome c oxidase activity and oxygen consumption together with oxidative DNA damage assessed by the presence of the 8-hydroxydeoxyguanine DNA base modification. These transient changes in mitochondrial functional activity were not observed in thymuses of mice rescued from lymphoma development by a bone marrow graft, suggesting an important role of mitochondria for neoplastic transformation in this model, which might therefore be of interest to test the utilization of antioxidants for the prevention of radiation-induced malignancies.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Bone Marrow Transplantation; Cell Respiration; Cell Transformation, Neoplastic; Deoxyguanosine; Electron Transport Complex IV; Female; Flow Cytometry; In Situ Hybridization; Leukemia, Radiation-Induced; Lymphoma; Male; Mice; Mice, Inbred C57BL; Microscopy, Fluorescence; Oxidative Stress; Oxygen Consumption; Preleukemia; Thymus Gland; Thymus Neoplasms; Up-Regulation; Whole-Body Irradiation

In order to clarify the involvement of oxygen radicals in lung carcinogenesis induced by diesel exhaust particles (DEP), the relationship between lung tumour response and formation of 8-hydroxydeoxyguanosine (8-OHdG) in lung DNA was examined. The role of high dietary fat and beta-carotene on these responses was also studied. Mice were intratracheally injected with 0.05, 0.1 and 0.2 mg of DEP per animal once weekly for 10 weeks. After 12 months, the lung tumour incidence in mice treated with 0.05 mg and 0.1 mg showed similar increases (30% and 31%), but was decreased to 24% at 0.2 mg. High dietary fat enhanced the incidence of both benign and malignant tumours. beta-carotene partially prevented the tumour development. After the 10 weekly treatments of DEP, inflammatory reaction was observed in the respiratory tract and alveoli. The formation of 8-OHdG in lung DNA from mice treated with DEP showed a dose dependent increase. 8-OHdG formation was enhanced by high dietary fat and partially reduced by beta-carotene. Formation of 8-OHdG was significantly correlated with the lung tumour incidence except at 0.2 mg. These results suggest that the induction of oxidative DNA damage may be an important factor in the initiation of DEP-induced lung carcinogenesis, and that beta-carotene and high dietary fat may play a role in the regulation of tumour development via modulation of the formation of 8-OHdG.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Body Weight; Carcinogenicity Tests; Deoxyguanosine; Dietary Fats; DNA; DNA Damage; Incidence; Lung; Lung Neoplasms; Lymphoma; Male; Mice; Mice, Inbred ICR; Neoplasms, Experimental; Vehicle Emissions

Photosensitized formation of 8-hydroxydeoxyguanosine (oh8dG) in DNA by riboflavin has recently been shown in vitro. The present study describes the formation of oh8dG in cellular DNA by photo-irradiation of cultured mammalian cells in the presence of riboflavin. Formation of oh8dG was dependent on the concentration of riboflavin as well as the duration of photoirradiation. These results suggest that photosensitized formation of oh8dG in DNA by riboflavin may be involved in photocarcinogenesis.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Cell Line; Deoxyguanosine; DNA; DNA Damage; Fibroblasts; Humans; Light; Lymphoma; Mice; Riboflavin; Tumor Cells, Cultured