Download 60 - Fox Chase Cancer Center

Proc Amer Assoc Cancer Res 2005; 46:492 [Abstract #2100]
Influence of Prepubertal Exposure to Benzyl Butyl Phthalate (BBP) on the Genomic
Signature of the Rat Mammary Gland.
Raquel Moral1, Gabriela A. Balogh1, Daniel Mailo1, Irma H. Russo1, Coral Lamartiniere2,
and Jose Russo1.
1
Breast Cancer Research Laboratory, Fox Chase Cancer Center, Philadelphia, PA
Department of Pharmacology and Toxicology, University of Alabama at Birmingham,
Birmingham, AL
2
Environmental estrogens, such as n-butyl benzyl phthalate (BBP), are compounds that act
as xenoestrogens, mimicking the effects of endogenous hormones and that have been
reported to alter tumorigenesis in several experimental animals. BBP is a phthalic ester
that is widely used as a plasticizer, in food wraps, and in cosmetic formulations. To better
understand the possible effect of this xenoestrogen on mammary gland biology and its
influence on cancer susceptibility, we analyzed the effect of prepubertal exposure to BBP
on the genomic signature of the rat mammary gland at different ages. Female rats were
exposed to BBP through the mother’s milk from birth to 21 days of age. Lactating
mothers were gavaged daily with either 500 mg BBP/kg body weight (BBP) or with the
same volume of sesame oil (Control). Ten litters per group were euthanized when they
reached the ages of 21, 35, 50 or 100 days. Abdominal mammary glands were excised for
RNA extraction, quality verification and pooling for reducing it to three replicas per
group. RNAs were fluorescently labeled for hybridization to Agilent 60-mer oligo
microarrays containing 22,000 features. Image analysis was performed with Feature
Extraction and ImaGene softwares. Data were analyzed with GeneSight software using
Lowess normalization. Only genes with 1.4-fold differences at p<0.05 confidence
analysis were considered. In 21 day-old rats BBP exposure resulted in the upregulation of
515 genes, 133 of which were known and included hormone related proteins
(hydroxysteroid dehydrogenase, lutropin, parathyroid-like peptide, GHRH); adhesion
molecules (rCdh8, tenascin), and many regulating cell proliferation and differentiation
genes, such as FABP3, growth factors (EGF, Insl6, PDGF), tumor suppressors (Wt1,
pRb) or other transcription factors (HNF-3, FDHR, TCF2). Among the upregulated genes
382 were unknown. There was only one downregulated gene, GAD1. At 35 days of age
the number of upregulated genes decreased significantly to 4 unknowns; 2 genes were
down regulated. By 50 days of age 25 genes were upregulated, 9 known and 16 unknown,
and 14 genes were downregulated, 8 known and 6 unknown. In the 100 day-old group,
only 3 genes were up modulated. There were significant differences in gene expression
among different ages, except by 2 genes: one of unknown sequence that was up
modulated at 21 and 35 days, and GAD1, which was downregulated at 21, 35 and 50
days. GAD1, FABP3 and Wt1 were chosen to validate results by concordance with
quantitative real-time reverse transcription PCR. Our findings indicated that exposure to
BBP during the lactational period modifies the genomic signature of the mammary gland,
mainly at 21 days of age, becoming less prominent thereafter. The influence of these
early changes on the future development and susceptibility of the mammary gland to
carcinogenesis remains to be elucidated. (This work was supported by NIEHS Grant U01
ES012771)