Original Articles
Copyright ©The Author(s) 1999. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Apr 15, 1999; 5(2): 138-142
Published online Apr 15, 1999. doi: 10.3748/wjg.v5.i2.138
Chemoprevention of 2-amino-1-methyl-6-phenyli-midazo [4, 5-b] pyridine-induced carcinogen-DNA adducts by Chinese cabbage in rats
Wen Tan, Dong-Xin Lin, Ying Xiao, Kadlubar Ff, Jun-Shi Chen
Wen Tan, Dong-Xin Lin, Department of Chemical Etiology and Carcinogenesis, Cancer Institute, Chinese Academy of Medical Sciences and Beijing Union Medical College, Beijing 100021, China
Ying Xiao, Department of Nutrition & Food Hygiene, School of Public Health, Beijing Medical University, Beijing 100083, China
Kadlubar Ff, Division of Molecular Epidemiology, National Center for Toxicological Research, Jefferson, AR 72079, United States
Jun-Shi Chen, Institute of Nutrition and Food Hygiene, Chinese Academy of Preventive Medicine, Beijing 100050, China
Author contributions: All authors contributed equally to the work.
Supported by the National Natural Science Foundation of China, No.39570627.
Correspondence to: Dr. Dong-Xin Lin, Department of Chemical Etiology and Carcinogenesis, Cancer Institute, Chinese Academy of Medical Sciences, P.O. Box 2258, Beijing 100021, China. dlin@public.net.cn
Telephone: +86-10-67722460 Fax: +86-10-67713359
Received: December 29, 1998
Revised: January 14, 1999
Accepted: January 26, 1999
Published online: April 15, 1999
Abstract

AIM The food-borne carcinogen 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) induces colon and mammary gland tumors in rats and has been implicated in the etiology of human colorectal cancer. This study was conducted to examine the potentially preventive effect of Chinese cabbage (Brassica chinensis), a brassica vegetable most commonly consumed in China, against this carcinogen induced DNA adduct formation in rats and its possible mechanisms. METHODS Sprague-Dawley rats were maintained for 10 days on basal diet or diet containing 20% (w/w) freeze-dried cabbage powder prior to administration of a single dose of PhIP (10 mg/kg) by oral gavage. Rats were sacrificed at 20 h after PhIP treatment and PhIP-DNA adducts in the colon, heart, lung and liver were analyzed using 32P-postlabeling technique. Levels of hepatic cytochrome P450 (CYP) 1A1 and 1A2, as indicated by 7-ethoxyresorufin O-deethylase and 7-methlxyresorufin O-demethylase activity, and cytosolic glutathione-S-transferases (GSTs) towards 1-chloro-2, 4-dinitrobenzene (CDNB) in the liver, lung and colon were measured.

RESULTS Rats pre-treated with Chinese cabbage and given a single dose of PhIP had reduced levels of PhIP-DNA adducts in the colon, heart, lung and liver, with inhibition rates of 82.3%, 60.6%, 48.4% and 48.9%, res pectively(P < 0.01). The enzyme assays revealed that Chinese cabbage induced both CYP1A1 and 1A2 activity, but the induction was preferential for CYP1A1 over 1A2 (81% vs 51%). GST activity towards CDNB in the liver and lung, but not colon, was also significantly increased by cabbage treatment.

CONCLUSION The results indicate that Chinese cabbage has a preventive effect on PhIP-initiated carcinogenesis in rats and the mechanism is likely to involve the induction of detoxification enzymes.

Keywords: heterocyclic amine; DNA-adduct; Brassica vegetable; colonic neoplasms; cytochrome P450