Chemoprevention of lung carcinogenesis by cacao liquor proanthocyanidins in a male rat multi-organ carcinogenesis model Megumi Yamagishi a , Midori Natsume b , Naomi Osakabe b , Kazushi Okazaki a , Fumio Furukawa a , Takayoshi Imazawa a , Akiyoshi Nishikawa a , Masao Hirose a, * a Division of Pathology, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan b Health and Bioscience Laboratories, Meiji Seika Kaisha, Ltd., 5-3-1, Chiyoda, Sakado-shi, Saitama 350-0289, Japan Received 21 August 2002; received in revised form 7 October 2002; accepted 28 October 2002 Abstract The effects of cacao liquor proanthocyanidins (CLPr) on tumorigenesis were investigated using a multi-organ carcinogenesis model in male F344 rats receiving combined treatment with a single i.p. injection of diethylnitrosamine (100 mg/kg body wt), four i.p. injections of N-methylnitrosourea (20 mg/kg body wt), four s.c. injections of dimethylhydrazine (40 mg/kg body wt), along with 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine and then 0.1% 2,2 0 -dihydroxy-di-n-propylnitrosamine, both in the drinking water, for 2 weeks each, during the initial 4-week period (DMBDD treatment). Starting 1 week thereafter, rats were administered CLPr at a dose of 0.025% or 0.25% and the experiment was terminated at week 36. The final survival rate for the DMBDD þ 0.25% CLPr group was significantly greater than for the DMBDD alone group. In the lung, significant reduction in the incidence and multiplicity of carcinomas was also observed, and in the thyroid, quantitative values for adenomas also tended to decrease in a CLPr dose-dependent manner. No significant modification in the small intestine, colon or kidney was evident. These results indicate that CLPr exerts chemopreventive effects in the lung without any promoting influence in other major organs. q 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Chemoprevention; Cacao liquor; Proanthocyanidin; Multi-organ carcinogenesis model 1. Introduction Flavonoids are natural polyphenolic antioxidants present in a wide range of plant foods. Several epidemiological studies have shown that their intake is associated with a decreased risk of cancer incidence [1–4]. In one longitudinal epidemiological study in Finland, flavonoid intake showed an inverse associ- ation with lung cancer incidence [3]. And, in one case- control study in Japan, high consumption of green tea was associated with a reduced risk of gastric cancer [4]. In the Western diet, cacao products are known to be a major source of compounds of the flavonoid family, such as catechins [5–7]. We have isolated a number of polyphenolic substances such as catechin, epicatechin, clovamide, quercetin, and their glucosides from cacao liquor, a major ingredient in chocolate and cocoa [8,9]. 0304-3835/02/$ - see front matter q 2002 Elsevier Science Ireland Ltd. All rights reserved. doi:10.1016/S0304-3835(02)00629-8 Cancer Letters 191 (2003) 49–57 www.elsevier.com/locate/canlet * Corresponding author. Tel.: þ81-3-3700-9818; fax: þ 81-3- 3700-1425. E-mail address: m-horose@nihs.go.jp (M. Hirose).