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M S Zhang

Publications and source records attributed to M S Zhang.

26 records · Page 2Linked to original sources
PubMed1986

Relevance of N-nitrosamines to esophageal cancer in China.

Studies on the relevance of the N-nitrosamines to esophageal cancer in China are reviewed. Esophageal cancer is a complex and multifactorial problem. Although a causal association between nitrosamines exposure and esophageal cancer in China has not yet been rigorously established, exposure of Lin-Xian subjects to nitrosamines either directly or as a result of their in vivo formation has been detected in our study. Several N-nitrosamines (NDMA, NDEA, NMBzA, NPyr, NPip, and NSAR) in gastric juice collected from Lin-Xian inhabitants have been detected. A correlation was found between the lesions of esophageal epithelium and the amount of nitrosamines present. In addition, the amounts of N-nitrosamino acids (N-nitrosoproline, N-nitrosothiazolidine 4-carboxylic acid, NSAR, and nitrates) excreted in 24-hr urine of subjects in Lin-Xian were significantly higher than those in Fan-Xian, indicating a higher exposure to N-nitroso compound and their precursors of the inhabitants in the high-risk area. The effect of nitrosamines on human esophagus has been investigated at the cellular levels. The amounts of O6-MedG in DNA of esophageal or stomach mucosa of patients from Lin-Xian were higher than that from Europe (Lyon and Essen). The presence of O6-MedG in the human fetal esophagus cultured with NMBzA was also detected. These findings indicate that the elevated levels of O6-MedG in esophageal DNA could be the result of a recent exposure to N-nitroso compounds or a genetically determined reduced cellular capacity for repair of O6-MedG from DNA. The hyperplasia was induced in the esophagus of human fetus that cultured with NMBzA for 2 weeks to 2 months. The intervention studies of esophageal cancer in Lin-Xian have been pursued. Intake of moderate doses of ascorbic acids by Lin-Xian subjects effectively reduced the urinary levels of N-nitrosamino acids to those found in un-dosed subjects in the low-risk area. If N-nitroso compounds are formed in vivo and are among the causative factors of esophageal cancer in Lin-Xian, ascorbic acid appears to be effective in lowering the body burden of these carcinogenic compounds. Thus, the plan of chemoprevention is carried out in Lin-Xian.

Ascorbic Acid↗
PubMed1986

[O6-methyldeoxyguanosine in DNA of the adjacent epithelium in human esophageal cancer in Linxian County].

Radioimmunoassay of monoclonal antibodies against O6-methyldeoxyguanosine (O6-MedG) was used to detect the presence of these DNA adducts in the human esophageal epithelium. The analysis comprised 48 adjacent epithelial specimens of the esophageal and cardiac cancer resected in Linxian County and 30 specimens of the fetal esophageal epithelium and 4 of the normal esophageal epithelium from autopsy as collected from the hospital in Beijing. The results show that O6-MedG was detected in all the specimens from the esophageal and cardiac cancer patients. In 7 samples in the adjacent epithelium of esophageal cancer, the level of O6-MedG ranged from 0.5 to 1.0 pmol/mgDNA. 19 showed higher levels up to 37.4 pmol/mgDNA with a mean of 4.72 +/- 6.08 pmol/mgDNA. 5 samples of gastric mucosa showed the level of O6-MedG ranging 0.3-1.0 pmol/mgDNA and the remaining 6 showed a higher level of 1.2-13.4 pmol/mgDNA. The mean was 3.31 +/- 3.97. In all the 11 patients, O6-MedG was detected in the para-cancerous gastric mucosa of the cardiac cancer. 4 normal autopsied esophageal epithelial samples were too low for detection. Samples from the fetal esophageal epithelium showed lower level of O6-MedG, the mean was 0.4 +/- 0.57 pmol/mgDNA. The results mentioned above give us the new evidence that the effect of N-nitrosamines is most likely a causative factor in the carcinogenesis of human esophageal cancer.

Cardia↗