| Research Abstract |
Reactive oxygen and nitrogen species generated by environmental and dietary factors can cause DNA damage and play important roles in mutagenesis and carcinogenesis. We have investigated sequence specificity of oxidative stress-mediated DNA damage by using 32P-labeled DNA fragments obtained from the human c-Ha-ras-1, p16 and p53 genes. Furthermore, protein expression profile in HL-60 cells treated with an environmental factor was analyzed using two-dimensional gel electrophoresis plus mass spectrometry.
(1) Catechol, a naturally occurring and an important industrial chemical, has been shown to have strong promotion activity and induce glandular stomach tumors to rodent. In addition, catechol is a major metabolite of carcinogenic benzene. Catechol induced oxidative DNA damage in HL-60 cells. Catechol caused damage to 32P-Labeled DNA fragments in the presence of Cu(II). When NADH was added, the DNA damage was markedly enhanced and clearly observed of relatively low concentrations of catech
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ol. Catalase inhibited the DNA damage. Therefore, it is concluded that the oxidative DNA damage by catechol through generation of H2O2 plays an important role in the carcinogenic process of catechol and benzene.
In addition, environmental factors (UVA, benz[a]anthracene, etc), dietary factors (homocysteine, catechins, etc) and medical and pharmaceutical products also induced sequence-specific DNA damage via H2O2 generation.
(2) Bisphenol A (BPA), which has been detected in canned food and human saliva, induced leukemias in rats. A BPA metabolite, 3-hydroxybisphenol A (3-OH-BPA), induced extensive DNA damage in the presence of Cu(II) and NADH. 3-OH-BPA strongly damaged G and C of the ACG sequence complementary to codon 273, a mutational spot of the p53 gene. Furthermore, flow cytometry showed that HL-60 cells treated with BPA underwent apoptotic death. Proteome analysis revealed that four proteins were differentially expressed between control cells and cells treated with BPA. These proteins identified in our proteomic studies may be implicated in carcinogenesis and candidates as tumor biomarkers. Less
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