Suppression of beta-catenin mutation by dietary exposure of auraptene, a citrus antioxidant, in N,N-diethylnitrosamine-induced hepatocellular carcinomas in rats.
Alteration of beta-catenin expression in hepatocellular carcinomas (HCCs) may play an important role in tumor progression by stimulating cell proliferation. We have previously reported that auraptene (AUR), an antioxidant agent isolated from citrus fruit, effectively inhibits chemically induced hepatocarcinogenesis in rats. In this study, we investigated the molecular mechanism of the inhibitory effects of dietary supplementation with AUR on N,N-diethylnitrosamine (DEN)-initiated hepatocarcinogenesis. Male F344 rats initiated with DEN were fed the AUR-containing diet during either the initiation stage (initiation feeding for 7 weeks) or post-initiation phase (post-initiation feeding for 25 weeks) of hepatocarcinogenesis. Liver tumors >5 mm in diameter were used for the analysis of beta-catenin gene mutation and beta-catenin protein expression. After PCR amplification of exon 2 of the beta-catenin gene, the products were sequenced directly. Mutations in the beta-catenin gene were detected in 8 of 24 HCCs (33.3%) in the DEN alone group, 7 of 15 HCCs (46.7%) in the DEN + AUR (initiation feeding) group, and 0 of 8 HCCs (0%) in the DENright curved arrow AUR (post-initiation feeding) group. No mutations of beta-catenin gene were detected in liver cell adenomas of any group. These results demonstrate that AUR exposure in post-initiation period suppresses the occurrence of HCCs with beta-catenin mutation, presumably by negative selection for neoplastic cells harboring the mutation.
Hara
Akira
A
Department of Tumor Pathology, Graduate School of Medicine, Gifu University, 1-1 Yanagido, Gifu 501-1194, Japan. ahara@cc.gifu-u.ac.jp
Sakata
Keiko
K
Yamada
Yasuhiro
Y
Kuno
Toshiya
T
Kitaori
Nami
N
Oyama
Takeru
T
Hirose
Yoshinobu
Y
Murakami
Akira
A
Tanaka
Takuji
T
Mori
Hideki
H
D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage; D006528:Carcinoma, Hepatocellular / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism; D002957:Citrus / Q000737:chemistry; D003374:Coumarins / Q000008:administration & dosage*; D003598:Cytoskeletal Proteins / Q000032:analysis / Q000235:genetics*; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004052:Diethylnitrosamine; D007150:Immunohistochemistry; D008113:Liver Neoplasms / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism; D008297:Male; D009154:Mutation / Q000187:drug effects*; D051381:Rats; D011916:Rats, Inbred F344; D015534:Trans-Activators / Q000032:analysis / Q000235:genetics*; D051176:beta Catenin
D000975:Antioxidants; D003374:Coumarins; C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; D004273:DNA, Neoplasm; D015534:Trans-Activators; D051176:beta Catenin; D004052:Diethylnitrosamine; C105832:aurapten