1. Mammary Gland Assessment in Guideline Toxicology Studies for Environmental Chemicals
Susan Makris
U.S. EPA, Office of Research and Development
National Center for Environmental Assessment
July 21, 2011
This presentation does not necessarily represent the policy or opinions of the U.S. EPA.

2. Background
Evaluation of structural and/or functional integrity of the mammary gland across life stages is integral to assessment of developmental, reproductive, and carcinogenic risk for environmental chemicals
Question: how well do standard toxicology guideline protocols assess mammary gland development, adult function, or pathology (including cancer)?
Makris, S.L. (2011) Current assessment of the effects of environmental chemicals on the mammary gland in guideline EPA, OECD, and NTP rodent studies. Environmental Health Perspectives (published on-line: doi: /ehp ).

3. Toxicology Guidelines
Standard testing protocol (study design); a tool that facilitates standardized data collection
Includes recommendations for:
Study methods
Endpoints to assess
Data analysis
Guidelines do not address when to conduct the study, or what substances to test
Each guideline focuses on specific exposures, endpoints, life stages, test species, etc.
Similar guidelines exist for various regulatory agencies

4. Analysis Prenatal Developmental Toxicity
Screening Developmental/Reproduction
2-Generation Reproduction
Reproductive Assessment by Continuous Breeding (RACB)
1-Generation Reproduction
Extended 1-Generation Reproduction
Developmental Neurotoxicity
Uterotrophic Assay
Hershberger Assay
Juvenile/Pubertal Male or Female Assay
Subacute or Subchronic
Chronic or Carcinogenicity
EPA, OECD, and NTP toxicology guidelines with:
Reproduction phase(s)
Development
Lactation
Endocrine assays
Postmortem evaluation
Organ weights
Necropsy observations
Histopathology
Evaluation of study designs for MG-specific recommendations
Note: study designs are described in the manuscript, and study diagrams are provided in supplemental materials on EHP website.
EPA = Environmental Protection Agency
OECD = Organisation for Economic Co-operation and Development
NTP = National Toxicology Program

5. Findings
In reproduction and endocrine studies, the guidelines do not clearly indicate the need to focus on evaluation of endpoints that are specific to MG development, health, or function
Developmental and functional assessments are indirect or non-specific (e.g., surrogate measures of offspring growth and survival)
Endpoints that can be useful in assessing MG toxicity:
Some protocols include endocrine-mediated biomarkers (e.g., timing of puberty) that could be informative about MG development and function
Clinical observations and postmortem examination may identify effects
In subchronic and chronic studies, MG pathology (when required) is generally:
Conducted on adult animals (not during development)
Female-centric (males are often not evaluated)
Not linked to developmental exposures (exception: NTP)

6. Recommendations
Guidelines should be written/revised to specifically address evaluation of MG endpoints
In studies that include peripubertal offspring that were treated in utero and/or postnatally, MG tissue should be evaluated using sensitive methods (e.g., whole mount technique)
In subchronic and chronic rodent studies, exposure should be initiated in utero
The evaluation of male MG tissue should be routinely required