RESUMO
PURPOSE: To compare the chemopreventive efficacy of Polyphenon E (Poly E), (-)-epigallocatechin-3-gallate (EGCG) and Polyphenon E without EGCG (Poly E-EGCG) on the development of benzo(a)pyrene (B(a)P)-induced lung tumors in A/J mice. METHODS: Female A/J mice were given a single intraperitoneal injection of B(a)P (100 mg/kg body weight). One week after B(a)P injection, animals received AIN-76A purified powder diet containing 0.975% (wt/wt) EGCG, 0.525% (wt/wt) Poly E-EGCG or 1.5% (wt/wt) Poly E for 24 weeks or control diet with no additives. RESULTS: Poly E treatment significantly decreased tumor multiplicity by 52% and tumor load by 64%, while EGCG and Poly E-EGCG did not significantly inhibit lung tumor multiplicity. EGCG was more stable in a complex mixture (Poly E) than as a pure compound. CONCLUSION: EGCG was ineffective when administered by diet likely due to its instability. Thus, EGCG's efficacy on mice lung tumorigenesis requires the presence of other tea catechins.
Assuntos
Anticarcinógenos/uso terapêutico , Catequina/análogos & derivados , Neoplasias Pulmonares/prevenção & controle , Pulmão/efeitos dos fármacos , Animais , Catequina/administração & dosagem , Catequina/uso terapêutico , Quimioprevenção , Feminino , Pulmão/patologia , Neoplasias Pulmonares/dietoterapia , Neoplasias Pulmonares/patologia , CamundongosRESUMO
Green tea has been shown to exhibit cancer-preventive activities in preclinical studies. However, (-)-epigallocatechin-3-gallate (EGCG) alone was shown to be ineffective in preventing lung tumorigenesis in mice by aerosol administration. In this study, Polyphenon E and Polyphenon E without EGCG were administered by aerosol delivery to A/J mice 2 weeks after carcinogen treatment and continuing daily throughout the remainder of the study (20 weeks). An improved aerosol delivery system with a custom-built atomizer, an efficient solvent remove system, and a nose-only exposure chamber was used to provide aerosols with stable size distribution. There were no significant differences in the size distributions of Polyphenon E and Polyphenon E without EGCG. With a relatively low dose level (4.19 mg/kg), Polyphenon E decreased tumor multiplicity by 53%, whereas Polyphenon E without EGCG at the same dose failed to inhibit lung carcinogenesis. These results indicate that aerosol administration can be an effective approach in chemoprevention study, and aerosolized Polyphenon E can significantly inhibit pulmonary adenoma formation and growth in A/J mice. Furthermore, in aerosolized form, EGCG, which is thought to be the most active component of Polyphenon E, has to be present with other tea catechins to show chemopreventive activity on lung tumorigenesis.