Affiliations: The First Department of Pathology, Kanazawa Medical
University, Ishikawa 920-0293, Japan | Research Fellow of the Japan Society for the Promotion
of Science, Tokyo 102-8471, Japan | Division of Applied Life Science, Graduate School of
Agriculture, Kyoto University, Kyoto 606-0085, Japan | National Institute of Fruit Tree Science, Shizuoka
424-0292, Japan | Department of Biochemistry, Kyoto Prefecture
University of Medicine, Kyoto 602-0841, Japan
Note: [] Address for correspondence: Dr. Rikako Suzuki, The First
Department of Pathology, Kanazawa Medical University, 1-1 Daigaku, Uchinada,
Ishikawa, 920-0293, Japan. Tel.: +81 76 286 2211; Fax: +81 76 286 6926; E-mail:
rikako@kanazawa-med.ac.jp
Abstract: The inhibitory effects of dietary feeding of citrus nobiletin on
azoxymethane (AOM)-induced rat colon carcinogenesis using a long-term bioassay
were investigated. Five-week old male F344 rats were initiated with two weekly
subcutaneous injections of AOM (20 mg/kg bw) to induce colonic tumors. They
were also given the diets containing 0.01% or 0.05% nobiletin for 34 weeks,
starting one week after the last dosing of AOM. At the end of the study, the
incidence of colonic adenocarcinoma were 67% in the AOM alone group, 55% in the
AOM→0.01% nobiletin group, 35% (p < 0.05) in the AOM→0.05%
nobiletin group. Also, nobiletin feeding reduced the cell-proliferation
activity, increased the apoptotic index, and decreased the prostaglandin
E_{2} content in colonic adenocarcinoma and/or colonic
mucosa. These findings might suggest that citrus nobiletin has chemopreventive
ability against AOM-induced rat colon carcinogenesis.
