Development of a rat model by 3,4-benzopyrene intra-pulmonary injection and evaluation of the effect of green tea drinking on p53 and bcl-2 expression in lung carcinoma

Background A convenient animal model of primary lung cancer is compelling for investigation into the disease mechanisms and for development of therapeutic strategies. This study aims to develop a reproducible rat model for lung carcinoma by intra-pulmonary injection of 3,4-benzopyrene, and to evaluate the preventive effect of green tea on the formation of lung carcinoma. Methods Sprague-Dawley rats of the same ages were randomly assigned into three groups treated differently. Rats in group one were given green tea in drinking water (tea concentration: 1.2%; tea polyphenols in the tea solution: 0.3%); rats in the groups two and three were given blank drinking water. Rats in the groups one and two were injected intra-pulmonarily with 3,4-benzopyrene dissolved in corn oil (2 mg/0.2 mL/injection, fortnightly, 4 times in all); rats in the group three were injected with the vehicle corn oil as the control for injection. All the rats were sacrificed one year after the first intra-pulmonary injection. Tumors developed in rats and lung tissues were collected for carcinoma diagnosis and for p53 and bcl-2 expression. Results Intra-pulmonary injection of 3,4-benzopyrene steady induced lung carcinoma at a success rate of 75%. Administration with green tea drinking significantly reduced the incidence of lung carcinoma to 30%. Green tea up-regulated p53 expression in lung carcinoma, but significantly down-regulated bcl-2 expression. Conclusions Intra-pulmonary injection of 3,4-benzopyrene can steady induce lung carcinoma in rats, and green tea has preventive effect against lung cancer possibly by regulating expression of some critical genes such as p53 and bcl-2. (C) 2009 Elsevier Ltd. All rights reserved.