Aop: 295

Title

Each AOP should be given a descriptive title that takes the form “MIE leading to AO”. For example, “Aromatase inhibition [MIE] leading to reproductive dysfunction [AO]” or “Thyroperoxidase inhibition [MIE] leading to decreased cognitive function [AO]”. In cases where the MIE is unknown or undefined, the earliest known KE in the chain (i.e., furthest upstream) should be used in lieu of the MIE and it should be made clear that the stated event is a KE and not the MIE. More help

Early-life stromal estrogen receptor activation by endocrine disrupting chemicals in the mammary gland leading to enhanced cancer risk

Short name
A short name should also be provided that succinctly summarises the information from the title. This name should not exceed 90 characters. More help
Early-life stromal ER-activation by EDCs leads to mammary cancer risk

Graphical Representation

A graphical summary of the AOP listing all the KEs in sequence, including the MIE (if known) and AO, and the pair-wise relationships (links or KERs) between those KEs should be provided. This is easily achieved using the standard box and arrow AOP diagram (see this page for example). The graphical summary is prepared and uploaded by the user (templates are available) and is often included as part of the proposal when AOP development projects are submitted to the OECD AOP Development Workplan. The graphical representation or AOP diagram provides a useful and concise overview of the KEs that are included in the AOP, and the sequence in which they are linked together. This can aid both the process of development, as well as review and use of the AOP (for more information please see page 19 of the Users' Handbook).If you already have a graphical representation of your AOP in electronic format, simple save it in a standard image format (e.g. jpeg, png) then click ‘Choose File’ under the “Graphical Representation” heading, which is part of the Summary of the AOP section, to select the file that you have just edited. Files must be in jpeg, jpg, gif, png, or bmp format. Click ‘Upload’ to upload the file. You should see the AOP page with the image displayed under the “Graphical Representation” heading. To remove a graphical representation file, click 'Remove' and then click 'OK.'  Your graphic should no longer be displayed on the AOP page. If you do not have a graphical representation of your AOP in electronic format, a template is available to assist you.  Under “Summary of the AOP”, under the “Graphical Representation” heading click on the link “Click to download template for graphical representation.” A Powerpoint template file should download via the default download mechanism for your browser. Click to open this file; it contains a Powerpoint template for an AOP diagram and instructions for editing and saving the diagram. Be sure to save the diagram as jpeg, jpg, gif, png, or bmp format. Once the diagram is edited to its final state, upload the image file as described above. More help

Authors

List the name and affiliation information of the individual(s)/organisation(s) that created/developed the AOP. In the context of the OECD AOP Development Workplan, this would typically be the individuals and organisation that submitted an AOP development proposal to the EAGMST. Significant contributors to the AOP should also be listed. A corresponding author with contact information may be provided here. This author does not need an account on the AOP-KB and can be distinct from the point of contact below. The list of authors will be included in any snapshot made from an AOP. More help

Andrea R. Hindman*+, Alissa P. Link^ and Ruthann A. Rudel*

*Silent Spring Institute, Newton, MA; +Social Science Environmental Health Research Institute, Northeastern University, Boston, MA; ^Research and Instruction, Northeastern University, Boston, MA

Point of Contact

Indicate the point of contact for the AOP-KB entry itself. This person is responsible for managing the AOP entry in the AOP-KB and controls write access to the page by defining the contributors as described below. Clicking on the name will allow any wiki user to correspond with the point of contact via the email address associated with their user profile in the AOP-KB. This person can be the same as the corresponding author listed in the authors section but isn’t required to be. In cases where the individuals are different, the corresponding author would be the appropriate person to contact for scientific issues whereas the point of contact would be the appropriate person to contact about technical issues with the AOP-KB entry itself. Corresponding authors and the point of contact are encouraged to monitor comments on their AOPs and develop or coordinate responses as appropriate.  More help
Andrea Hindman   (email point of contact)

Contributors

List user names of all  authors contributing to or revising pages in the AOP-KB that are linked to the AOP description. This information is mainly used to control write access to the AOP page and is controlled by the Point of Contact.  More help
  • Andrea Hindman

Status

The status section is used to provide AOP-KB users with information concerning how actively the AOP page is being developed, what type of use or input the authors feel comfortable with given the current level of development, and whether it is part of the OECD AOP Development Workplan and has been reviewed and/or endorsed. “Author Status” is an author defined field that is designated by selecting one of several options from a drop-down menu (Table 3). The “Author Status” field should be changed by the point of contact, as appropriate, as AOP development proceeds. See page 22 of the User Handbook for definitions of selection options. More help
Author status OECD status OECD project SAAOP status
Under development: Not open for comment. Do not cite Under Development 1.79 Included in OECD Work Plan
This AOP was last modified on January 09, 2020 08:10
The date the AOP was last modified is automatically tracked by the AOP-KB. The date modified field can be used to evaluate how actively the page is under development and how recently the version within the AOP-Wiki has been updated compared to any snapshots that were generated. More help

Revision dates for related pages

Page Revision Date/Time

Abstract

In the abstract section, authors should provide a concise and informative summation of the AOP under development that can stand-alone from the AOP page. Abstracts should typically be 200-400 words in length (similar to an abstract for a journal article). Suggested content for the abstract includes the following: The background/purpose for initiation of the AOP’s development (if there was a specific intent) A brief description of the MIE, AO, and/or major KEs that define the pathway A short summation of the overall WoE supporting the AOP and identification of major knowledge gaps (if any) If a brief statement about how the AOP may be applied (optional). The aim is to capture the highlights of the AOP and its potential scientific and regulatory relevance More help

This adverse outcome pathway (AOP) links gestational EDC exposure to enhanced breast cancer risk. The molecular initiating event (MIE) is gestational estrogen receptor (ER) activation; particularly, stromal activation at in utero time of exposure. The ER is a master transcriptional regulator, with proliferation as its primary effect, and is the main mediator of breast development [24, 25]. Human-relevant EDC exposure triggers transcriptional activity that promotes altered signaling between the epithelial and stromal tissue compartments leading to disrupted tensional homeostasis [26] and tissue architecture. Inflammation and altered cellular differentiation are major cell- and tissue-level key events (KEs) mediating these disruptions. The pathway converges on the following mammary gland adverse outcomes (AOs) at the tissue- and organ-levels: altered density, structure and hormone sensitivity along with hyperplasia. Epigenetic alterations are a cellular-level AO that propagate gestational EDC exposure to later-life risk through cellular memory that directs ER-mediated gene expression and altered mammary development. Risk of tumorigenesis follows from these AOs.

The industrial estrogen, bisphenol A (BPA) is one of the most data-rich chemicals related to breast cancer and altered mammary gland development [11]. As such, studies in model rodent strains following gestational EDC exposure to bisphenol A (BPA) or DES provide experimental support for this AOP and human-relevance. A thorough search of the literature yielded experimental evidence for this AOP as directed by a mix of natural and MeSH term search logic specifying rodents and non-human primates (population); human-relevant, in utero exposure to BPA or DES (exposure); and mammary gland AOs (outcome) [27-32] (see PECO statement, Table 1 below). Most studies investigating EDC-effects on mammary development heavily describe altered growth and structure, resulting in limited mechanistic understanding. This AOP integrates knowledge and tools from investigations of established breast cancer risk factors such as density and obesity to enhance understanding of the molecular- and cellular-driven etiologies of altered mammary structure and growth. Integrating this knowledge promotes the development of in vitro assays capable of predicting high-risk phenotypes and offers efficient alternatives to in vivo mammary gland evaluation. Ultimately, making these links in the knowledge base will improve screening to identify chemicals that act on gestational development and will more specifically target chemical contributions to later-life breast cancer risk in toxicity testing. Productive intermediate testing endpoints would follow ER-binding, -activation and steroidogenesis (OECD TG-455; EDSP TG-890[33, 34]), precede carcinogenicity (OECD TG-451, and -453) and connect these with EDC-effects on breast cancer due to prenatal exposure (OECD TG-414, -415, -416, -422, -443). This AOP will also describe ‘missed opportunities’ in the existing evidence; not reporting or measuring traditional toxicity testing endpoints, like uterine weight and body weight alongside more sensitive mammary gland growth and structural changes. Failure to do this in parallel within the same study undermines the sensitivity of these endpoints to predict later-life breast cancer risk.

Table 1. PECO statement [27, 28].  A statement of the Population, Exposure, Comparators and Outcomes was prepared to direct objective experimental study collection for this AOP synthesis on breast cancer risk from early-life EDC exposure. The Organization for Economic Co-operation and Development does not cite systematic review methods or objective identification of included evidence in its guidance for AOP development. A narrowed survey of review articles in PubMed, published after 2006 and until November 2018, was performed to assess the state of mechanistic evidence connecting EDC exposure to breast cancer risk and altered mammary gland growth and structure. This step assisted problem formulation by situating human-relevant EDC exposures in the hallmarks of cancer via ‘important reviews.’ There were no systematic reviews. This initial survey of the review literature assisted search logic development and supported an initial sketch of the AOP.

INCLUSION CRITERIA

EXCLUSION CRITERIA

Population (Experimental animal, in vivo studies)

  • Female laboratory rodents
  • Female laboratory non-human primates
  • Human and non-rodent animals and organisms, including wildlife, aquatic species and plants
  • Males

Exposure

  • Human-relevant exposure to BPA, related BPA analogues or DES
  • In utero exposure. In utero exposure is a requirement but studies that extend exposure to the perinatal period are also included
  • Exposure to controlled doses of BPA via an exposure method (e.g. – diet, drinking water, gavage, injection)
  • High-dose or pharmacological-dose exposures to BPA or DES
  • Any other EDC
  • Exposure to chemical mixtures in animals
  • Exposures during other developmental windows of risk

Comparators

  • Vehicle-only, concurrently run treatment controls
  • No controls
  • Historical controls

Outcomes

  • Determination of mammary gland disruption via any methodology intended to address mechanisms mapped in the AOP (see Figure ) including to alterations of tissue density, epigenetics, gland morphology, hormone sensitivity and hyperplasia as precursors to tumorigenesis
  • Assessed in virgin, female laboratory rodents or non-human primates at any stage-of-life (e.g. - postnatal, pubertal or adult development)
  • Uterine weight
  • Body weight
  • Any other organs
  • Any other stage-of-life

Publication parameters

  • Peer-reviewed
  • Original data
  • Studies must be published in English
  • Non-peer reviewed; gray literature (e.g. - conference presentations or other studies published in abstract form only, grant awards/ proposals and theses/ dissertations
  • Retracted articles
  • Review articles (only considered for the initial survey of available mechanistic data)

Background (optional)

This optional subsection should be used to provide background information for AOP reviewers and users that is considered helpful in understanding the biology underlying the AOP and the motivation for its development. The background should NOT provide an overview of the AOP, its KEs or KERs, which are captured in more detail below. Examples of potential uses of the optional background section are listed on pages 24-25 of the User Handbook. More help

Breast cancer risk background: Breast cancer is a significant health concern as the second leading cause of death in women [1]. Only 5-10% of breast cancers are attributable to genetic predisposition and substantial evidence indicates many lifestyle and environmental factors contribute to lifetime risk [2-5]. Early-life developmental disruption by hormone-like, or endocrine disrupting chemicals (EDCs), heightens age-related breast cancer risk. A human model of this disruption emerges from the treatment of pregnant women with synthetic estrogen, diethylstilbestrol (DES), beginning in the 1940’s with the intent to prevent miscarriages. This practice ceased when women exposed in gestation – “DES Daughters” – had a 40x increased incidence of cervical and vaginal cancers [6, 7], highlighting in utero development as a critical window of exposure. The later finding that “DES Daughters” also had a 2-fold increased incidence of breast cancer only detected in women ≥30 years post-exposure, underscores the latency of this disruption in causing disease [7-9]. Studies of the reproductive tract and mammary gland of rodent models have recapitulated these increased risks [10-12]. While synthetic estrogens are no longer prescribed to pregnant women, human biomonitoring data show widespread exposure to EDCs that include weak estrogens [13, 14] and their ability to cross the placental barrier [14-18]. Many EDCs are present at human-relevant exposures in the environment, but these chemicals can act together on the same adverse health outcomes [19], including estrogen action as a relevant target for breast cancer [20-23]. Taken together, this evidence raises concerns that early-life EDC exposure enhances later-life breast cancer risk.

Summary of the AOP

This section is for information that describes the overall AOP. The information described in section 1 is entered on the upper portion of an AOP page within the AOP-Wiki. This is where some background information may be provided, the structure of the AOP is described, and the KEs and KERs are listed. More help

Events:

Molecular Initiating Events (MIE)
An MIE is a specialised KE that represents the beginning (point of interaction between a stressor and the biological system) of an AOP. More help
Key Events (KE)
This table summarises all of the KEs of the AOP. This table is populated in the AOP-Wiki as KEs are added to the AOP. Each table entry acts as a link to the individual KE description page.  More help
Adverse Outcomes (AO)
An AO is a specialised KE that represents the end (an adverse outcome of regulatory significance) of an AOP.  More help

Relationships Between Two Key Events (Including MIEs and AOs)

This table summarises all of the KERs of the AOP and is populated in the AOP-Wiki as KERs are added to the AOP. Each table entry acts as a link to the individual KER description page.To add a key event relationship click on either Add relationship: events adjacent in sequence or Add relationship: events non-adjacent in sequence.For example, if the intended sequence of KEs for the AOP is [KE1 > KE2 > KE3 > KE4]; relationships between KE1 and KE2; KE2 and KE3; and KE3 and KE4 would be defined using the add relationship: events adjacent in sequence button.  Relationships between KE1 and KE3; KE2 and KE4; or KE1 and KE4, for example, should be created using the add relationship: events non-adjacent button. This helps to both organize the table with regard to which KERs define the main sequence of KEs and those that provide additional supporting evidence and aids computational analysis of AOP networks, where non-adjacent KERs can result in artifacts (see Villeneuve et al. 2018; DOI: 10.1002/etc.4124).After clicking either option, the user will be brought to a new page entitled ‘Add Relationship to AOP.’ To create a new relationship, select an upstream event and a downstream event from the drop down menus. The KER will automatically be designated as either adjacent or non-adjacent depending on the button selected. The fields “Evidence” and “Quantitative understanding” can be selected from the drop-down options at the time of creation of the relationship, or can be added later. See the Users Handbook, page 52 (Assess Evidence Supporting All KERs for guiding questions, etc.).  Click ‘Create [adjacent/non-adjacent] relationship.’  The new relationship should be listed on the AOP page under the heading “Relationships Between Two Key Events (Including MIEs and AOs)”. To edit a key event relationship, click ‘Edit’ next to the name of the relationship you wish to edit. The user will be directed to an Editing Relationship page where they can edit the Evidence, and Quantitative Understanding fields using the drop down menus. Once finished editing, click ‘Update [adjacent/non-adjacent] relationship’ to update these fields and return to the AOP page.To remove a key event relationship to an AOP page, under Summary of the AOP, next to “Relationships Between Two Key Events (Including MIEs and AOs)” click ‘Remove’ The relationship should no longer be listed on the AOP page under the heading “Relationships Between Two Key Events (Including MIEs and AOs)”. More help

Network View

The stressor field is a structured data field that can be used to annotate an AOP with standardised terms identifying stressors known to trigger the MIE/AOP. Most often these are chemical names selected from established chemical ontologies. However, depending on the information available, this could also refer to chemical categories (i.e., groups of chemicals with defined structural features known to trigger the MIE). It can also include non-chemical stressors such as genetic or environmental factors. Although AOPs themselves are not chemical or stressor-specific, linking to stressor terms known to be relevant to different AOPs can aid users in searching for AOPs that may be relevant to a given stressor. More help

Stressors

The stressor field is a structured data field that can be used to annotate an AOP with standardised terms identifying stressors known to trigger the MIE/AOP. Most often these are chemical names selected from established chemical ontologies. However, depending on the information available, this could also refer to chemical categories (i.e., groups of chemicals with defined structural features known to trigger the MIE). It can also include non-chemical stressors such as genetic or environmental factors. Although AOPs themselves are not chemical or stressor-specific, linking to stressor terms known to be relevant to different AOPs can aid users in searching for AOPs that may be relevant to a given stressor. More help

Life Stage Applicability

Identify the life stage for which the KE is known to be applicable. More help

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) can be selected. In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help

Sex Applicability

The authors must select from one of the following: Male, female, mixed, asexual, third gender, hermaphrodite, or unspecific. More help

Overall Assessment of the AOP

This section addresses the relevant biological domain of applicability (i.e., in terms of taxa, sex, life stage, etc.) and WoE for the overall AOP as a basis to consider appropriate regulatory application (e.g., priority setting, testing strategies or risk assessment). The goal of the overall assessment is to provide a high level synthesis and overview of the relative confidence in the AOP and where the significant gaps or weaknesses are (if they exist). Users or readers can drill down into the finer details captured in the KE and KER descriptions, and/or associated summary tables, as appropriate to their needs.Assessment of the AOP is organised into a number of steps. Guidance on pages 59-62 of the User Handbook is available to facilitate assignment of categories of high, moderate, or low confidence for each consideration. While it is not necessary to repeat lengthy text that appears elsewhere in the AOP description (or related KE and KER descriptions), a brief explanation or rationale for the selection of high, moderate, or low confidence should be made. More help

Domain of Applicability

The relevant biological domain(s) of applicability in terms of sex, life-stage, taxa, and other aspects of biological context are defined in this section. Biological domain of applicability is informed by the “Description” and “Biological Domain of Applicability” sections of each KE and KER description (see sections 2G and 3E for details). In essence the taxa/life-stage/sex applicability is defined based on the groups of organisms for which the measurements represented by the KEs can feasibly be measured and the functional and regulatory relationships represented by the KERs are operative.The relevant biological domain of applicability of the AOP as a whole will nearly always be defined based on the most narrowly restricted of its KEs and KERs. For example, if most of the KEs apply to either sex, but one is relevant to females only, the biological domain of applicability of the AOP as a whole would be limited to females. While much of the detail defining the domain of applicability may be found in the individual KE and KER descriptions, the rationale for defining the relevant biological domain of applicability of the overall AOP should be briefly summarised on the AOP page. More help

Essentiality of the Key Events

An important aspect of assessing an AOP is evaluating the essentiality of its KEs. The essentiality of KEs can only be assessed relative to the impact of manipulation of a given KE (e.g., experimentally blocking or exacerbating the event) on the downstream sequence of KEs defined for the AOP. Consequently evidence supporting essentiality is assembled on the AOP page, rather than on the independent KE pages that are meant to stand-alone as modular units without reference to other KEs in the sequence.The nature of experimental evidence that is relevant to assessing essentiality relates to the impact on downstream KEs and the AO if upstream KEs are prevented or modified. This includes: Direct evidence: directly measured experimental support that blocking or preventing a KE prevents or impacts downstream KEs in the pathway in the expected fashion. Indirect evidence: evidence that modulation or attenuation in the magnitude of impact on a specific KE (increased effect or decreased effect) is associated with corresponding changes (increases or decreases) in the magnitude or frequency of one or more downstream KEs.When assembling the support for essentiality of the KEs, authors should organise relevant data in a tabular format. The objective is to summarise briefly the nature and numbers of investigations in which the essentiality of KEs has been experimentally explored either directly or indirectly. See pages 50-51 in the User Handbook for further definitions and clarifications.  More help

Evidence Assessment

The biological plausibility, empirical support, and quantitative understanding from each KER in an AOP are assessed together.  Biological plausibility of each of the KERs in the AOP is the most influential consideration in assessing WoE or degree of confidence in an overall hypothesised AOP for potential regulatory application (Meek et al., 2014; 2014a). Empirical support entails consideration of experimental data in terms of the associations between KEs – namely dose-response concordance and temporal relationships between and across multiple KEs. It is examined most often in studies of dose-response/incidence and temporal relationships for stressors that impact the pathway. While less influential than biological plausibility of the KERs and essentiality of the KEs, empirical support can increase confidence in the relationships included in an AOP. For clarification on how to rate the given empirical support for a KER, as well as examples, see pages 53- 55 of the User Handbook.  More help

Quantitative Understanding

Some proof of concept examples to address the WoE considerations for AOPs quantitatively have recently been developed, based on the rank ordering of the relevant Bradford Hill considerations (i.e., biological plausibility, essentiality and empirical support) (Becker et al., 2017; Becker et al, 2015; Collier et al., 2016). Suggested quantitation of the various elements is expert derived, without collective consideration currently of appropriate reporting templates or formal expert engagement. Though not essential, developers may wish to assign comparative quantitative values to the extent of the supporting data based on the three critical Bradford Hill considerations for AOPs, as a basis to contribute to collective experience.Specific attention is also given to how precisely and accurately one can potentially predict an impact on KEdownstream based on some measurement of KEupstream. This is captured in the form of quantitative understanding calls for each KER. See pages 55-56 of the User Handbook for a review of quantitative understanding for KER's. More help

Considerations for Potential Applications of the AOP (optional)

At their discretion, the developer may include in this section discussion of the potential applications of an AOP to support regulatory decision-making. This may include, for example, possible utility for test guideline development or refinement, development of integrated testing and assessment approaches, development of (Q)SARs / or chemical profilers to facilitate the grouping of chemicals for subsequent read-across, screening level hazard assessments or even risk assessment. While it is challenging to foresee all potential regulatory application of AOPs and any application will ultimately lie within the purview of regulatory agencies, potential applications may be apparent as the AOP is being developed, particularly if it was initiated with a particular application in mind. This optional section is intended to provide the developer with an opportunity to suggest potential regulatory applications and describe his or her rationale.To edit the “Considerations for Potential Applications of the AOP” section, on an AOP page, in the upper right hand menu, click ‘Edit.’ This brings you to a page entitled, “Editing AOP.” Scroll down to the “Considerations for Potential Applications of the AOP” section, where a text entry box allows you to submit text. In the upper right hand menu, click ‘Update AOP’ to save your changes and return to the AOP page or 'Update and continue' to continue editing AOP text sections.  The new text should appear under the “Considerations for Potential Applications of the AOP” section on the AOP page. More help

References

List the bibliographic references to original papers, books or other documents used to support the AOP. More help

1.            Siegel, R.L., K.D. Miller, and A. Jemal, Cancer Statistics, 2017. CA Cancer J Clin, 2017. 67(1): p. 7-30.

2.            Kim, B.J. and S.H. Kim, Prediction of inherited genomic susceptibility to 20 common cancer types by a supervised machine-learning method. Proc Natl Acad Sci U S A, 2018. 115(6): p. 1322-1327.

3.            Lichtenstein, P., et al., Environmental and heritable factors in the causation of cancer--analyses of cohorts of twins from Sweden, Denmark, and Finland. N Engl J Med, 2000. 343(2): p. 78-85.

4.            Foulkes, W.D., Inherited susceptibility to common cancers. N Engl J Med, 2008. 359(20): p. 2143-53.

5.            Peto, J., et al., Prevalence of BRCA1 and BRCA2 gene mutations in patients with early-onset breast cancer. J Natl Cancer Inst, 1999. 91(11): p. 943-9.

6.            Herbst, A.L. and R.E. Scully, Adenocarcinoma of the vagina in adolescence. A report of 7 cases including 6 clear-cell carcinomas (so-called mesonephromas). Cancer, 1970. 25(4): p. 745-57.

7.            Hatch, E.E., et al., Cancer risk in women exposed to diethylstilbestrol in utero. Jama, 1998. 280(7): p. 630-4.

8.            Hoover, R.N., et al., Adverse health outcomes in women exposed in utero to diethylstilbestrol. N Engl J Med, 2011. 365(14): p. 1304-14.

9.            Palmer, J.R., et al., Prenatal diethylstilbestrol exposure and risk of breast cancer. Cancer Epidemiol Biomarkers Prev, 2006. 15(8): p. 1509-14.

10.          Newbold, R.R., W.N. Jefferson, and E. Padilla-Banks, Long-term adverse effects of neonatal exposure to bisphenol A on the murine female reproductive tract. Reprod Toxicol, 2007. 24(2): p. 253-8.

11.          Soto, A.M., et al., Does cancer start in the womb? altered mammary gland development and predisposition to breast cancer due to in utero exposure to endocrine disruptors. J Mammary Gland Biol Neoplasia, 2013. 18(2): p. 199-208.

12.          Boylan, E.S. and R.E. Calhoon, Transplacental action of diethylstilbestrol on mammary carcinogenesis in female rats given one or two doses of 7,12-dimethylbenz(a)anthracene. Cancer Res, 1983. 43(10): p. 4879-84.

13.          Calafat, A.M., et al., Exposure of the U.S. population to bisphenol A and 4-tertiary-octylphenol: 2003-2004. Environ Health Perspect, 2008. 116(1): p. 39-44.

14.          Woodruff, T.J., A.R. Zota, and J.M. Schwartz, Environmental chemicals in pregnant women in the United States: NHANES 2003-2004. Environ Health Perspect, 2011. 119(6): p. 878-85.

15.          Gerona, R.R., et al., Bisphenol-A (BPA), BPA glucuronide, and BPA sulfate in midgestation umbilical cord serum in a northern and central California population. Environ Sci Technol, 2013. 47(21): p. 12477-85.

16.          Chen, M., et al., Determination of bisphenol-A levels in human amniotic fluid samples by liquid chromatography coupled with mass spectrometry. J Sep Sci, 2011. 34(14): p. 1648-55.

17.          Balakrishnan, B., et al., Transfer of bisphenol A across the human placenta. Am J Obstet Gynecol, 2010. 202(4): p. 025.

18.          Nishikawa, M., et al., Placental transfer of conjugated bisphenol A and subsequent reactivation in the rat fetus. Environ Health Perspect, 2010. 118(9): p. 1196-203.

19.          Goodson, W.H., 3rd, et al., Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead. Carcinogenesis, 2015. 36(1).

20.          Dairkee, S.H., et al., A Ternary Mixture of Common Chemicals Perturbs Benign Human Breast Epithelial Cells More Than the Same Chemicals Do Individually. Toxicol Sci, 2018. 165(1): p. 131-144.

21.          Goodson, W.H., 3rd, et al., Activation of the mTOR pathway by low levels of xenoestrogens in breast epithelial cells from high-risk women. Carcinogenesis, 2011. 32(11): p. 1724-33.

22.          Silva, E., N. Rajapakse, and A. Kortenkamp, Something from "nothing"--eight weak estrogenic chemicals combined at concentrations below NOECs produce significant mixture effects. Environ Sci Technol, 2002. 36(8): p. 1751-6.

23.          Charles, G.D., et al., Analysis of the interaction of phytoestrogens and synthetic chemicals: an in vitro/in vivo comparison. Toxicol Appl Pharmacol, 2007. 218(3): p. 280-8.

24.          Couse, J.F., et al., Tissue distribution and quantitative analysis of estrogen receptor-alpha (ERalpha) and estrogen receptor-beta (ERbeta) messenger ribonucleic acid in the wild-type and ERalpha-knockout mouse. Endocrinology, 1997. 138(11): p. 4613-21.

25.          Feng, Y., et al., Estrogen receptor-alpha expression in the mammary epithelium is required for ductal and alveolar morphogenesis in mice. Proc Natl Acad Sci U S A, 2007. 104(37): p. 14718-23.

26.          Northey, J.J., L. Przybyla, and V.M. Weaver, Tissue Force Programs Cell Fate and Tumor Aggression. Cancer Discov, 2017. 7(11): p. 1224-1237.

27.          Vandenberg, L.N., et al., A proposed framework for the systematic review and integrated assessment (SYRINA) of endocrine disrupting chemicals. Environ Health, 2016. 15(1): p. 016-0156.

28.          Rochester, J.R., A.L. Bolden, and C.F. Kwiatkowski, Prenatal exposure to bisphenol A and hyperactivity in children: a systematic review and meta-analysis. Environ Int, 2018. 114: p. 343-356.

29.          Lewis, S.J., et al., Developing the WCRF International/University of Bristol Methodology for Identifying and Carrying Out Systematic Reviews of Mechanisms of Exposure-Cancer Associations. Cancer Epidemiol Biomarkers Prev, 2017. 26(11): p. 1667-1675.

30.          Ertaylan, G., et al., A Comparative Study on the WCRF International/University of Bristol Methodology for Systematic Reviews of Mechanisms Underpinning Exposure-Cancer Associations. Cancer Epidemiol Biomarkers Prev, 2017. 26(11): p. 1583-1594.

31.          Kushman, M.E., et al., A systematic approach for identifying and presenting mechanistic evidence in human health assessments. Regul Toxicol Pharmacol, 2013. 67(2): p. 266-77.

32.          Higgins, J.P.T.a.G.S., Cochrane Handbook for Systematic Reviews of Interventions. Vol. Version 5.1.0 [updated March 2011]. 2011: The Cochrane Collaboration, 2011.

33.          OECD, Test No. 455: Performance-Based Test Guideline for Stably Transfected Transactivation In Vitro Assays to Detect Estrogen Receptor Agonists and Antagonists. 2016.

34.          EPA, Endocrine Disruptor Screening Program Tier 1 Assays: Considerations for Use in Human Health and Ecological Risk Assessments, O.o.C.S.a.P.a.P.O.a.O.o.P.P. (OPP), Editor. 2013, Environmental Protection Agency: Washington, DC 20460.