Combination chemoprevention by tomato and garlic in the hamster buccal pouch carcinogenesis model

Abstract

Combination chemoprevention by dietary agents is a promising strategy for cancer prevention. We evaluated the combined chemopreventive effect of tomato paste and aqueous garlic extract against 7, 12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Hamsters were divided into eight groups. Animals in group 1 served as control. Groups 2 through 4 were given tomato, garlic and mixture of tomato and garlic respectively. The right buccal pouches of animals in group 5 were painted with 0.5% DMBA three times a week. Animals in groups 6 to 8 painted with DMBA as in group 5, received in addition, intragastric administration of tomato paste, aqueous garlic extract alone and in combination respectively on days alternate to DMBA application. Lipid peroxidation, reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione-S-transferase (GST), glutathione reductase (GR) and γ-glutamyltranspeptidase (GGT) as well as GSH/GSSG ratio were measured in the buccal pouch, liver and erythrocytes at the end of 14 weeks. Diminished lipid peroxidation in the HBP tumours was associated with enhanced levels of GSH and GSH-dependent enzymes. In contrast to the buccal pouch, the liver and erythrocytes of tumour-bearing hamsters exhibited elevated lipid peroxidation accompanied by compromised antioxidant status. Although administration of tomato paste and garlic alone significantly reduced the tumour incidence and tumour burden, combined administration of tomato and garlic was more effective in inhibiting the development of HBP carcinomas as revealed by modulation of the cellular redox status. From these results, we suggest that broader spectrum of chemoprevention with less adverse effects can be attained through effective combination of functional foods.