Journal Article

Neonatal exposure to the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-<i>b</i>]pyridine via breast milk or directly induces intestinal tumors in multiple intestinal neoplasia mice

Jan Erik Paulsen, Inger-Lise Steffensen, Åshild Andreassen, Rose Vikse and Jan Alexander

in Carcinogenesis

Volume 20, issue 7, pages 1277-1282
Published in print July 1999 | ISSN: 0143-3334
Published online July 1999 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/20.7.1277
Neonatal exposure to the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine via breast milk or directly induces intestinal tumors in multiple intestinal neoplasia mice

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We examined whether the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) could increase intestinal tumorigenesis in neonatal C57BL/6J-Min/+ mice, a murine model for familial adenomatous polyposis. Min/+ mice are heterozygous for a nonsense mutation in the adenomatous polyposis coli gene and spontaneously develop multiple intestinal adenomas, primarily in the small intestine. Neonatal Min/+ mice (3–6 days old) were exposed to PhIP via breast milk from lactating dams given 8 s.c. injections of 50 mg/kg PhIP three times a week or to 8 s.c. injections of 25 or 50 mg/kg PhIP directly, over the same period. At the age of 11 weeks, the number, diameter and location of the intestinal tumors were scored. Remarkably, a 2- to 4-fold increase in the number of small intestinal tumors was seen in Min/+ mice exposed to PhIP via breast milk (P < 0.001). To our knowledge, this is the first time PhIP has been reported to induce tumors following exposure via breast milk from PhIP-exposed dams. Upon direct exposure to 50 mg/kg PhIP, a 6- to 9-fold increase in the number of small intestinal tumors was observed (P < 0.001). The diameter of the PhIP-induced small intestinal tumors was slightly increased (P < 0.001). In the colon, a 3- to 4-fold increase in the number of tumors was seen in Min/+ mice exposed to PhIP via breast milk (P = 0.004). Direct exposure to 50 mg/kg PhIP caused a 2- to 6-fold increase in the number of colonic tumors (P = 0.014). The PhIP-induced colonic tumors were located more distally and displayed a smaller diameter than the tumors from the controls (P < 0.05). In contrast to a previous study, where PhIP showed only a moderate tumorigenic effect in adult Min/+ mice, the present study demonstrates a strong tumorigenic effect of PhIP in neonatally exposed Min/+ mice, even after exposure via breast milk from PhIP-exposed dams.

Keywords: ACF, aberrant crypt foci; APC/Apc, adenomatous polyposis coli gene (human/murine); FAP, familial adenomatous polyposis; Min, multiple intestinal neoplasia; PhIP, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine.

Journal Article.  5236 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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