This document discusses potential links between endocrine disrupting chemicals and breast cancer risk. It summarizes studies showing environmental factors play a major role in breast cancer causation. It describes how chemicals like DES, DDT, dieldrin, PCBs, PBDEs may disrupt hormones and increase breast cancer risk and discusses evidence from human and animal studies. The document concludes that while some chemicals show possible links, more research is still needed, especially on exposures during critical windows of development.

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Breast Cancer –
Is there a link to
Endocrine Disrupting Chemicals?
Suzanne M. Snedeker, Ph.D.
Assoc. Director for Translational Research
Cornell University’s
Program on Breast Cancer and
Environmental Risk Factors (BCERF)
sms31@cornell.edu
http://www.cfe.cornell.edu/bcerf/

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Contribution of established factors to
breast cancer risk
 National surveys of US white women
 40-50% of breast cancer risk
 Age first birth / nulliparity
 Family history of breast cancer
 Higher income
Ref: Madigan et al., J Natl Cancer Inst, 87:1681-5, 1987
 North Carolina Breast Cancer Study
 25% of breast cancer risk
 Menarche before 14 yrs
 First birth at or after 20 yrs / nulliparity
 Family history of breast cancer
 History of benign breast disease
Ref: Rockhill et al., Am J Epidemiology, 147:826-33, 1998

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Environmental links to breast cancer
 Scandinavian Twin Study
 27% of risk, Heritable factors
 73% of risk, Environmental factors
 6% of risk, shared environment
 67% of risk, non-shared environment
 Suggests that environmental factors
play a major role in the causation of
breast cancer
Ref: Lichtenstein et al., New England J. of Medicine, 343:78-85, 2000

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Risks Related to Breast Cancer
Advancing
Age
Genetics
Alcohol Hormone
Therapy
Gender
Close
Relative
Benign Breast
Disease
Early
Menarche
Age at
First Birth Passive
Smoke
Education
& Income
Overweight
(post-menopause) Lack of
Exercise
Chemicals
-Work
-Home
-Garden
-Recreation
Late
Menopause Breast
Feeding
???
Diet
Ionizing
Radiation

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Endocrine disrupting chemicals
–Definitions
 Endocrine Disruptor
 Exogenous substance or mixture that alters
the function(s) of the endocrine system and
consequently causes adverse health effects
in an intact organism, or its progeny, or
(sub)populations
 Potential Endocrine Disruptor
 Exogenous substance or mixture that
possess properties that might be expected to
lead to endocrine disruption in an intact
organism, or its progeny, or (sub)populations
Ref: WHO/IPCS, Damstra et al. (eds), Global Assessment of the
State-of-the Science of Endocrine Disruptors, 2002

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Endocrine disrupting chemicals
–Possible modes of action
Affect hormone levels
- Estrogen mimic
(additive / synergistic)
- Alter synthesis or
degradation pathways
 Increase rate of cell
proliferation
 Increase probability of
mutations
 Support the growth of
hormonally responsive
tumors
 Act directly as
carcinogens
Affect the development
of breast tissue
- Hormone receptors
- State of differentiation
 Affect hormonal
responsiveness
 Affect response to
chemical carcinogens
Breast cancer risk

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Endocrine disrupting chemicals
 Pharmaceuticals
 Pesticides
 Industrial Chemicals / Contaminants
 Heavy Metals

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Endocrine disrupting chemicals
–Ovarian hormones
 Estrogen and progesterone have
established roles in:
 Normal mammary gland development in
humans and rodent animal models
 Regulation of breast cell proliferation during
menstrual and estrous cycles
 Humans – breast cell proliferation is the
highest in luteal phase when progesterone
levels highest; progestins do not “oppose”
the action of estrogen in the breast
Ref: Haslam et al., J Mammary Gland Biol Neoplasia, 7:93-105, 2002

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Endocrine disrupting chemicals
–Ovarian hormones
 In utero exposure to estrogen associated
with higher breast cancer risk
 Higher birth weight
Ref: Michels, et al., Lancet, 348:1542-46, 1996
Kaijser et al., Epidemiology, 11:315-9, 2000
 Like-sexed female (dizygotic) twins
Ref: Ekbom et al., J Natl Cancer Inst 88:71-6, 1997
Cerhan et al., J Natl Cancer Inst, 92:262-5, 2000
Hubinette et al., Int J Cancer 91:248-51, 2001
 Preeclampsia (lower estrogen, lower risk)
Ref: Ekbom et al., Lancet, 340:1015-18, 1992
Ekbom et al., J Natl Cancer Inst 88:71-6, 1997

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Endocrine disrupting chemicals
–Diethylstibesterol (DES)
 DES–History of use in women
 Pregnant women treated with DES to prevent
miscarriages from 1940s to 1971 in US and 1978 in
Europe; use continued in unindustrialized countries
 Dosage typically 12,000 mg over 4 to 6 months
 DES–History of use in livestock in US
 Use as growth promoter in feed approved in 1954
 Ear implants approved in 1955
 Use in premixes revoked in 1972 because of
detection of residues in edible tissues after slaughter
 Use in livestock revoked by US Food and Drug
Administration in 1978 / 1979
Ref: Calle et al., Am J Epidemiology, 144:645-52, 1996
DHEW, US FDA Judge Davidson brief, 1978
Huckell et al., Lancet, 348:331-1996

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Endocrine disrupting chemicals
–Diethylstilbestrol (DES)
 Human breast cancer risk – DES mothers
First Author Year RR 95% CI Type of study
Greenberg 1984 1.40 1.10-1.90 Incidence
Colton 1993 1.35 1.05-1.74 Incidence
Calle 1996 1.34 1.06-1.69 Mortality
Titus-Ernstroff 2001 1.27 1.07-1.52 Incidence

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Endocrine disrupting chemicals
–Diethylstilbestrol (DES)
 Premenopausal breast cancer risk – DES Daughters
First Author Year RR 95% CI Years Follow-up
Huckell 1996 Reported 2 cases (28, 34 years of age)
Hatch 1998 1.18 0.56 - 2.49 16 years
Palmer 2002 1.4 0.7 - 2.6 19 years
Palmer 2002 2.5 1.0 - 6.3 in women over 40
Palmer 2002 1.9 0.8 - 4.5 in ER positive tumors

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Endocrine disrupting chemicals
–Post-menopausal hormone use
 Effects on breast cancer risk
First Author Year E RR 95% CI E+P RR 95% CI
Stanford 1995 0.4 0.20-1.0
Ross 2000 1.06 0.97-1.15 1.24 1.07-1.45
Schairer 2000 1.20 1.00-1.4 1.40 1.10-1.80
Colditz* 2000 1.23 1.06-1.42 1.67 1.18-2.36
Chen 2002 1.17 0.85-1.60 1.49 1.04-2.12
WHI 2002 1.26 1.00-1.59
Porch 2002 0.96 0.65-1.42 1.37 1.05-1.78
Most studies based on 4-5 years current or recent use
* Colditz-Risk at 70 years of age after 10 years of use from 50-60 yrs of age

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Post-menopausal hormone use
–Breast cancer risk, Nurses Health Study
Ref: Colditz and Rosner, Am. J. Epid., 152:950-964, 2000
HRT, Estrogen + Prog., 10 yrs
ERT, Estrogen unopposed, 10 yrs
ERT, Estrogen unopposed, 5 yrs
Non-users, solid line

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Endocrine disrupting chemicals
–Post-menopausal hormone use
 Nurses Health Study
Ref: Porch et al., Cancer Causes & Control, 13:847-854, 2002
PMH use in 17,835 women aged > 45 years, followed for 5.9 yrs
PMH use E RR 95% CI* E+P RR 95% CI*
0.96 0.65-1.42 1.37 1.05-1.78
< 5 yrs 0.96 0.58-1.58 1.11 0.81-1.52
> 5 yrs 0.99 0.65-1.53 1.76 1.29-2.39
Progestin pattern
<2 wks/month 1.04 0.74 -1.46
Continuous 1.82 1.34 -2.48
 Breast cancer risk increased in women who used:
 Estrogen-progestin PMH therapy for 5 years or more
 Continous rather than cyclic progestin combinations

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Organochlorines and breast cancer risk
–Strength of the evidence
 DDE and DDT
 Early descriptive studies and one case-control study
suggested a positive association between blood /
adipose tissue DDE levels and breast cancer risk
 Majority of recent, well controlled cohort and case-
controlled studies have not demonstrated that
levels of DDE predict breast cancer risk in white,
western, North American or European white women
Ref: Snedeker, Environ. Health Perspec. 109(suppl 1):35-47, 2001
WHO/IPCS, Damstra et. al (ed) Global Assessment EDCs, 2002

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DDT and DDE commentary
–Possible explanations for lack of an association
 Chemical formulation
 In white western women, predominate exposure may not
be to estrogenic o,p’-DDT found in the insecticide, but to
the very weakly estrogenic, anti-androgenic breakdown
product, p,p’-DDE found as residues in food
 Heavily exposed populations not well studied
 Predominate use of DDT in the US was on cotton in the
south-eastern. One study of African Americans women from
North Carolina suggests positive association of DDE and
breast cancer risk
 Few studies of breast cancer risk in countries that currently
use DDT for malaria control
 Critical windows of exposure need evaluation
 Little information on whether exposure to DDT during early
breast development affects breast cancer risk

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Organochlorines and breast cancer risk
–Dieldrin
 Breast cancer risk, equivocal evidence
 Danish studies, Copenhagen City Heart Study
 1) Serum dieldrin associated with breast cancer risk
OR 2.05, 95%CI 1.17-3.57
Ref: Høyer et al., Lancet, 352, 1816-20,1998
 2) Serum dieldrin, p53 mutation status & breast cancer risk
OR 3.53, 05% CI 0.70-15.79
Ref: Høyer et al., Breast Cancer Res Treat, 71:59-65, 2002
 American studies, no significant association
OR 0.6, 95% CI 0.3-1.3, Cohort of Missouri women
Ref: Dorgan et al., Cancer Causes & Control 10:1-11, 1999
OR 1.37, 95% CI 0.60-2.72, Long Island Breast Cancer Study
Ref: Gammon et al., Cancer Epidem Biomarkers Prevention 11:686-697, 2002

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Organochlorines and breast cancer risk
–Dieldrin
 Breast cancer survival rates and dieldrin levels
 Danish studies, Copenhagen City Heart Study
 1) Breast cancer survival and serum dieldrin
RR 2.78, 95% CI 1.38-5.59
Higher rate of death associated with highest blood
dieldrin levels
Ref: Høyer et al., J Clin Epidemiology, 53:323-330, 2000
 2) Investigated influence of Estrogen Receptor (ER)
status and serum dieldrin on breast cancer survival
ER+ RR 2.2, 95% CI 0.9-5.4
ER- RR 1.8, 95% CI 0.3-5.5
Risk of dying not significantly elevated in those with
higher serum dieldrin levels, regardless of ER status
Ref: Høyer et al., BMC Cancer 1:8, 2001
http://www.biomedcentral.com/1471-2407/1/8

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Organochlorines and breast cancer risk
–Industrial chemicals
 Total polychlorinated biphenyls (PCBs)
 Little evidence of increased breast cancer risk
 Polymorphisms, Gene-environment interaction
 Higher BC risk in sub-group of white American women with
elevated PCB levels AND variant in CYP1A1
Ref: Moysich et al., Cancer Ep. Biomarkers Prev. 8:414-4, 1999
 Individual PCB congeners
 Difficult to evaluate; estrogenic congeners don’t predominate
 Some evidence of increased BC risk with congeners that
bind to Ah receptor (mono-ortho-substituted)
Ref: Demers et al., Am J. Epidemiology, 155:629-35, 2002
 Possible association with poorer prognosis
 Association with larger, poorer grade breast tumors
Ref: Woolcott, et al., Cancer Causes Control,12:395-404, 2001

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Endocrine disrupting chemicals
–Industrial chemicals
 Polybrominated diphenyl ethers (PBDP)
 Uses - Flame retardant in plastics, textiles, carpets
and furniture foam
 Production - 40,000 tons / yr globally (1990)
 Dietary intake - Nordic areas, 0.2-0.7 micrograms/day
 Ecology
 Detected in marine life globally
 Evidence of human breast milk contamination
 Detected in air, drinking water, as food residues
Refs: Darnerund et al, Environ Health Perspect 109(suppl 1):49-68, 2001
Christensen and Platz, J Environ Monit 3:543-7, 2001
She et al., Chemosphere 46:697-707, 2002
McDonald, Chemosphere 46:745-55, 2002
Wenning, Chemosphere 46:779-96, 2002

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Endocrine disrupting chemicals
–Industrial chemicals
 Polybrominated diphenyl ethers (PBDP)
 Evidence of estrogenicity
 Stimulates ER-dependent gene expression in
human T47D breast cancer cells
 Induces cell proliferation in estrogen-
dependent MCF-7 breast tumor cell line
 Estrogenicity pf PBDEs decreased as
bromination increased
 PBDPs agonists for both ER-a and ER-b
Refs: Samuelsen et al., Cell Biol Toxicol 17:139-51, 2001
Meerts et al., Environ Health Perspect 109:399-407, 2001

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Endocrine disrupting chemicals
–Occupational exposures
ED Chemical Probable exposure
% BC Cases % Controls
Nonylphenol 21.5 21.4
Butylbenzylphthalate (BBP) 10.0 13.2
BHA 7.3 9.6
Bisphenol A 9.6 11.6
No significant increases in breast cancer risk
 PCBs, OR = 3.2, 95% CI 0.8-12.2
 4-octylphenol, OR = 2.9, 95% CI 0.8-10.8
Ref: Aschengrau et al., Am. J. Ind. Med., 34:6-14, 1998

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Endocrine disrupting chemicals
–Household levels, Cape Cod study
Silent Spring Institute
Developed methodology to assess levels of pesticides,bisphenol A,
alkylphenols, PAHs, and PCBs in air and dust of residences
(microgram/g dust)
Chemical No Detect/No Anal Range Mean
DEHP 6/6 69.4-524.0 315.0
BBP 6/6 12.1-524 184.0
Carbaryl 2/6 27.2-140 83.6
Chlorpyrifos 3/6 1.26-89.5 30.7
Bisphenol A 3/6 0.25-0.48 0.4
4-Nonylphenol 4/6 2.3-7.82 4.3
Benzo(a)pryrene 5/6 0.45-10.6 2.9
Ref: Rudel et. al., J. Air & Waste Mang. Assoc., 51: 499-513, 2001

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Endocrine disrupting chemicals
–Effects on early breast development
 Premature Thelarche in Puerto Rico (PR)
 Over 5,000 cases of premature thelarche in the last
30 years (breast development < 8 yrs of age)
 Suspect list:
 Waste stream from OCA factories
 Hormones residues in food
 Ovarian cysts
 Use of soy formula
 DEHP (phthalate)
Ref: Freni-Titulear et al., Am. J. Dis. Children, 140:1263-67, 1986;
Colon et al., Environmental Health Perspectives, 108:895-900, 2000

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Endocrine disrupting chemicals
–Phthalates and Premature Thelarche in Puerto Rican Girls
0
100
200
300
400
500
600
DBP DEP BBP DOP DEHP MEHP Total
Controls
PT Cases
Phthalate esters
Ref: Colon et al., Environ Health Perspect, 108:895-900, 2000

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Endocrine disrupting chemicals
–Premature thelarche and breast cancer risk
 More questions than answers
 Does occurrence of premature thelarche in girls
affect the window of susceptibility of the
developing breast to chemical carcinogens?
 Do endocrine disrupting chemicals have a role in
influencing early breast development?
 Research needs
 Linkage studies needed between girls with
premature thelarche and incidence of breast
cancer
 Studies needed to assess whether endocrine
disrupting chemicals can influence the onset of
breast development

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Endocrine disrupting chemicals
–Industrial contaminants
 Dioxins
 Seveso Italy, 1976 industrial accident
 Breast cancer mortality females,1976-86
RR 0.64, 95%CI 0.4 - 0.9 (less than expected)
Ref: Bertazzi et al., Am J Epidemiology, 129:1187-1200, 1989
 Seveso Women’s Health Study
-Cohort of 981 women, infants to 40 yrs of age in
1976, resided in area of highest TCDD exposure
-Preliminary data; those with highest exposures
had higher breast cancer risk (15 cases)
Ref: Warner et al., Environ Health Perspect 110:625-628, 2002

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Endocrine disrupting chemicals
-Cellular targets for carcinogens
 Terminal End Bud
(TEB)
 Alveolar Buds
Mammary gland structures in the 35-day old CD-1 female mouse
Photo: Snedeker and
DiAugustine, 1988

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Endocrine disrupting chemicals
-Understanding susceptibility
Ref: Russo and Russo, Oncology Research, 11:169-178, 1999
E2
Growth Hormone
IGF
Human breast development

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Endocrine Disrupting Chemicals
-Influencing the window of susceptibility
 Possible ways in utero or pubertal
exposures to EDCs may affect breast
cancer risk:
 Affecting the expression of hormone or growth
factor receptors, and hormone responsiveness of
the mammary gland
 Lengthening the window of susceptibility by
affecting mammary gland development
 Persistence of terminal end buds
 Influencing differentiation

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Endocrine Disrupting Chemicals
-Influencing the window of susceptibility
 Dioxin - TCDD; effects on mammary gland
 TCDD affects ER- a expression
 Gestational-lactation exposure to TCDD in rats causes an
increase in ER-a expression levels and impaired differentiation
in mammary glands of female pups
Ref: Lewis et al., Toxicological Sciences 62:46-53, 2001
 TCDD affects cancer susceptibility
 Gestational exposure to TCDD causes persistency of TEB
structures in female pups, delayed vaginal opening, and an
increase in chemically induced (DMBA) mammary
adenocarcinomas
Ref: Brown et al., Carcinogenesis, 19:1623-1629, 1998
 TCDD permanently affects mammary gland development
 Normal mammary gland transplanted into fat pads of TCDD
treated female rats grows at a slower rate and appeared
underdeveloped; TCDD may affect development of stroma
Ref: Fenton et al., Toxicological Sciences, 67:63-74, 2002

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Endocrine disrupting chemicals
–Heavy metals
 Cadmium (Cd), possible estrogenic effects
 Interacts with estrogen receptor-alpha (ER-a) MCF-7 cells
 Cd binds to ER-a, and blocks binding of estradiol to ER-a
 Interacts with hormone binding domain of ER-a
 COS-1 cells cotransfected with GAL-ER and GAL4 reporter gene
 Treatment with either Cd or estradiol increased reporter gene
activity four-fold
 ER-a mutants used to identify interaction sites of Cd with ER-a
hormone binding domain
 In vivo effect on rodent mammary gland
 Promotes growth, differentiation and side branching of MG in
ovariectomized animal
 In utero exposure; earlier onset of puberty; altered MG
development
Ref: Garcia-Morales et al., J Biol Chem 269:16896-901, 1994
Stocia et al., Molecular Endocrinology, 14:545-553, 2000
Maritin, MB, abstract, e_hormone 2001, Tulane University

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Endocrine disrupting chemicals
–Heavy metals
 Arsenite, possible estrogenic effects
 Interacts with estrogen receptor-alpha (ER-a)
MCF-7 breast cancer cells treated with arsenite
 Decreased level of ER-a and ER-a mRNA
 Increased concentration of progesterone receptor (PR)
 Arsenite-induced increase in PR blocked by antiestrogens
 Arsenite blocked binding of estradiol to ER-a
 Stimulates proliferation in MCF-7 cells
 Arsenite stimulated proliferation of MCF-7 cells in estrogen
depleted medium; effect blocked by antiestrogens
 Interacts with hormone binding domain of ER-a
 COS-1 cells transfected with GAL-ER and CAT reporter
 Arsenite or estradiol treatment induced CAT activity
 ER-a mutants used to identify interaction sites of arsenite with
ER-a hormone binding domain
Ref: Stocia et al., Endocrinology, 141:3595-3602, 2000

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Endocrine disrupting chemicals
–Current challenges
 Complexity of breast cancer
 Long latency
 Many established risk factors
 Risk influenced by interaction of genetic
alterations, susceptibility and proliferative
state

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Endocrine disrupting chemicals
–Current challenges
 Exposure issues
 Difficult to characterize and measure low-level
exposures to multiple chemicals from the distant
past
 Few chemicals have validated biomarkers
 Levels of exposure to EDCs at critical periods of
breast development (in utero through puberty) is
lacking
 Exposures to EDCs in the home environment not
well characterized

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Endocrine disrupting chemicals
–Current challenges
 Modeling issues
 May be difficult to evaluate effects of low-level
exposures to multiple chemicals using epidemiology
 Animal modeling should include promotional models
to assess effects of EDCs that may influence growth
of established hormone-dependent tumors
 Estrogenicity should not be the sole endpoint for
EDC breast cancer risk evaluation; other hormones,
growth factor agonists, and chemicals that affect
mammary gland development should be evaluated