Mutation Research 551 (2004) 223–231
Effect of dietary supplementation on the frequency of
spontaneous lacZ mutations in the developing colon
G.A. Trentin
a
, J. Moody
a
, N. Shima
a
, L.U. Thompson
b
, J.A. Heddle
a,∗
a
Department of Biology, York University, 4700 Keele Street, Toronto, Ont., Canada M3J 1P3
b
Department of Nutritional Sciences, University of Toronto, Toronto, Ont., Canada M5S 3E2
Received 14 January 2004; received in revised form 6 April 2004; accepted 7 April 2004
Abstract
Epidemiological studies have demonstrated that dietary modifications can reduce the incidence of cancer. Specifically, diets
high in vegetables and fruits are associated with lower rates of cancer at many sites. Somatic mutations have a critical role in
carcinogenesis suggesting the use of in vivo mutation assays as an alternative approach to studying the relationship between
diet and cancer. Since the rate of accumulation of spontaneous mutations is highest during growth and development early
in life, we tested whether certain foods as dietary supplements could reduce the rate of mutation during this period using
lacZ transgenic mice. Pregnant female mice were placed on a control diet or a diet supplemented to 20% final dry weight
with broccoli, cabbage, carrots, flaxseed, green peas, green peppers, oranges or strawberries for the entire duration of their
pregnancy and lactation. Mutation frequencies were subsequently measured at the lacZ transgene in colonic epithelial cells
of the offspring at 3 weeks of age. A small number of measurements were also made on siblings at 8 weeks of age. While the
control AIN-96G diet on its own resulted in lower mutant frequencies than had been observed in earlier experiments with lab
chow, no significant reduction in mutant frequencies was detected for any of the foods tested as compared to the AIN-93G diet
alone. Significantly more mutations were found at 3 weeks of age in mice fed diets supplemented with broccoli or oranges,
but the result with oranges may be the result of jackpot mutations.
© 2004 Published by Elsevier B.V.
Keywords: Dietary supplementation; lacZ; Colon
1. Introduction
DNA mutations have a central role in carcinogene-
sis. Cancer arises from not one but several mutations
and, in general, those that occur during an individual’s
lifetime rather than those that are inherited are respon-
sible [1,2]. The sources of these somatic mutations are
∗
Corresponding author. Tel.: +1 416 736 2100x33053;
fax: +1 416 736 5698.
E-mail address: jheddle@yorku.ca (J.A. Heddle).
replication errors and DNA lesions generated by ex-
ogenous and/or endogenous genotoxic agents. Spon-
taneous damage produced by endogenous factors such
as oxygen radicals may be particularly important, as
they are thought to be major contributors of mutations
involved in spontaneous carcinogenesis [3]. Although
cancers are more common at older ages, most sponta-
neous mutations arise before adulthood. Two-thirds of
the total mutant accumulation at the hprt gene in hu-
mans occurred by 20 years of age [4,5]. Further sup-
port has come from two transgenic mouse systems.
0027-5107/$ – see front matter © 2004 Published by Elsevier B.V.
doi:10.1016/j.mrfmmm.2004.04.006