phosphorus-radioisotopes and 7-methyl-2-deoxyguanosine

7-Methyldeoxyguanosine (7-medG) may be a useful marker of human exposure to methylating agents at the individual level. Methods of detection, including 32P-postlabeling, HPLC with electrochemical or fluorescence detection, and immunoassays, are critically summarized. These methods have been applied to the analysis of 7-medG in human samples, resulting from environmental exposure or endogenous processes. Detectable levels of adduct have been demonstrated in several tissues (liver, lung, bronchial, pancreas) and peripheral white blood cells. Studies are in progress to verify the possible use of white blood cells as a surrogate for internal organs.

Topics: Alkylating Agents; Biomarkers; Chromatography, High Pressure Liquid; Deoxyguanosine; DNA; DNA Damage; Electrochemistry; Environmental Exposure; Environmental Pollutants; Fluorescence; Humans; Immunoassay; Leukocytes; Methylation; Phosphorus Radioisotopes

Gastric cancer is the most common cancer in Korea. The causes are still unknown but it has been speculated that gastric cancer is associated with consumption of foods rich in nitrates/nitrites or a high dietary intake of salt or pickled food. In the present study, we studied the level of alkylated DNA adducts formed in gastric cancer tissues in comparison with that in normal gastric mucosa. DNA was extracted from surgically removed gastric cancer tissues and patient-matched normal gastric mucosa. The level of N7-methyldeoxyguanosine was measured by 32P-postlabelling assay after high performance liquid chromatography (HPLC) enrichment. We found that the level of N7-methyldeoxyguanosine of gastric cancerous tissues was significantly higher than that of normal gastric mucosa (P=0.01685).

Topics: Adenocarcinoma; Chromatography, High Pressure Liquid; Deoxyguanosine; DNA Adducts; DNA Damage; DNA Methylation; DNA, Neoplasm; Humans; Phosphorus Radioisotopes; Radioisotope Dilution Technique; Stomach Neoplasms

A highly sensitive and specific assay for the detection of N7-methyl-2'-deoxyguanosine (N7methyldG) has been developed by combining high-performance liquid chromatography, 32P-postlabeling, and nucleotide chromatography. Separation of normal nucleotides and adducts by high-performance liquid chromatography and then combining a portion of 2'-deoxyguanosine to the N7methyldG allows for quantitation using an internal standard. The directly determined molar ratio is not subject to errors in digestion, variable ATP-specific activity, or assumptions in relative adduct-labeling efficiency. The detection limit was one N7methyldG adduct in 10(7) unmodified 2'-deoxyguanosine bases. N7methyldG adducts have been detected in 5 human lung samples in which O6-methyl-2'-deoxyguanosine adducts had been previously determined. The mean ratio of N7methyldG to O6-methyl-2'-deoxyguanosine was determined to be approximately 10. The current assay complements the high-performance liquid chromatography/32P-postlabeling assay for O6-methyl-2'-deoxyguanosine and increases the detection sensitivity of DNA methylated by exogenous alkylating agents.

Topics: Adult; Aged; Chromatography, High Pressure Liquid; Deoxyguanosine; DNA; Female; Humans; Lung; Male; Middle Aged; Phosphorus Radioisotopes