title: Relevance of drug metabolizing enzyme activity modulation by tea polyphenols in the inhibition of esophageal tumorigenesis.
abstract: Tea is a popular, socially accepted, drink that is enjoyed by millions of people. A growing body of evidence suggests that moderate consumption of tea may protect against several forms of cancer. It is also known that bioactivation of precarcinogens and detoxification of ultimate carcinogens is carried out mainly by drug metabolizing enzymes such as cytochrome P450 (CYP). The present study investigates the effect of tea consumption on modulating CYP and phase II conjugating enzymes, and their association in the chemopreventive effect against esophageal tumorigenesis using both in vitro and in vivo techniques. Female Wistar rats were given aqueous solutions (2% w/v) of six different teas, standard green tea extract (GTE) (0.5% w/v), and dandelion tea (2% w/v) as the sole source of fluid for two weeks prior to and during the entire period of tumour induction (12 weeks). Animals were gavaged with 0.5 mg/kg N-nitrosomethylbenzylamine (NMBA) twice weekly for 12 weeks for esophageal tumor induction and the activities of different CYP isoforms and phase II enzymes were determined in the liver microsomes or cytosols. GTE, green tea and Dandelion tea caused decrease in tumour multiplication, tumour size and tumour volume; however, none of these tea preparations altered tumour incidence. No appreciable changes in drug metabolizing enzyme activity were observed in the treatment groups. Thus, the modulations in the activities of CYP 1A1/ 1A2 and CYP2E enzymes, by pre-treatment with green and dandelion teas, observed in our earlier experiments, seem to be compensated by the tumor inducing agent, NMBA. The balance between phase I carcinogen-activating enzymes and phase II detoxifying enzymes could be important in determining the risk of developing chemically-induced cancer and the present study in conjunction with the previous observations suggest a possible role of drug metabolizing enzymes in the anticancer effect of tea.
authors.affiliation: MD Anderson Cancer Center Orlando, Orlando, FL 32806, USA. pius.maliakal@orlandohealth.com
authors.forename: Pius
authors.initials: P
authors.lastname: Maliakal
authors.forename: Umesh T
authors.initials: UT
authors.lastname: Sankpal
authors.forename: Riyaz
authors.initials: R
authors.lastname: Basha
authors.forename: Cima
authors.initials: C
authors.lastname: Maliakal
authors.forename: Andrea
authors.initials: A
authors.lastname: Ledford
authors.forename: Sompon
authors.initials: S
authors.lastname: Wanwimolruk
mesh_terms: D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004128:Dimethylnitrosamine / Q000031:analogs & derivatives; D004938:Esophageal Neoplasms / Q000139:chemically induced / Q000201:enzymology / Q000517:prevention & control*; D005260:Female; D059808:Polyphenols / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013662:Tea / Q000737:chemistry*
chemical_list: D016588:Anticarcinogenic Agents; D059808:Polyphenols; D013662:Tea; D003577:Cytochrome P-450 Enzyme System; C014707:nitrosobenzylmethylamine; D004128:Dimethylnitrosamine