Building on National Initiatives for New Chemicals Screening

Institution: University of California, Berkeley
Investigator(s): Chris  Vulpe , Ph.D. -
Award Cycle: 2011 (Cycle 17) Grant #: 17UB-8708 Award: $1,175,569
Award Type: SRI Request for Proposal (RFP)
Research Priorities
Etiology and Prevention>Etiology: the role of environment and lifestyle



Initial Award Abstract (2011)

Non-technical overview:
Understanding how exposure to chemicals in the environment may raise the risk of breast cancer could offer clues to preventing the disease. Currently, the vast majority of chemicals found in homes, consumer products, and the environment have not been safety-tested. For those chemicals that are tested, most of the methods used are not designed to detect chemical effects specific to breast cancer, and they are typically too slow and expensive to screen the tens of thousands of chemicals on the market. As chemicals in the environment are increasingly suspected to contribute --directly or indirectly-- to breast cancer risk, improving these tests has become a top research priority for many breast cancer organizations. The proposed project addresses these concerns by developing innovative methods to rapidly screen chemicals using methods that are directly relevant to breast cancer. The project also responds to the findings of the CBCRP-funded Breast Cancer and Chemicals Policy project, which recommended development of novel breast cancer-relevant cell-based chemical tests (assays) that can be incorporated into regulatory testing programs and initiatives to design safer chemicals (green chemistry). Finally, it builds on, and will provide information for, major new initiatives at the US Environmental Protection Agency (EPA’s ToxCast program) and the National Toxicology Program (NTP’s Tox21 program) that are developing rapid chemical screening methods to fill current gaps in chemical safety evaluation. Data from the EPA ToxCast and NTP Tox21 screening programs will be used to prioritize chemicals for further evaluation and regulation, so it is important that they use breast-cancer relevant tests.

Research questions:
We anticipate that cell-based (in vitro) chemical tests can be adapted and used to quickly and cost-effectively identify chemicals that may play a role in breast cancer. The EPA ToxCast assays evaluate many different mechanisms of action, or ways that chemicals can affect cells and tissues. However, these tests were not specifically designed to detect mechanisms relevant to breast cancer. We will adapt the cell-based tests used by EPA to make them relevant for breast cancer by transferring the methods into breast cells. We will also develop new tests to fill gaps in current testing methods, for example tests that measure changes in mammary cell specific enzymes involved in estrogen production. By comparing the effects of chemicals that we know cause tumors in animal studies (carcinogens) to those chemicals that do not (non-carcinogens), we will be able to identify a set of tests that can help predict which chemicals might raise the risk of the disease. These chemicals could then be targeted for further testing or for regulation. By identifying the cell changes that occur frequently with exposure to chemicals known to cause breast cancer in laboratory animals, we furthermore expect to be able to create a profile of a possible breast carcinogen.

General methodology:
First we will select from chemical tests already validated by ToxCast, choosing the assays that are most relevant to breast cancer. We will transfer these tests into a variety of breast cell models that range in their complexity. We will also develop two new assays that are not part of the ToxCast program but that represent mechanisms likely to be important in breast cancer. Second, we will run these assays on approximately 60 chemicals and compare the results of assays performed on chemicals not associated with breast cancer to the results of assays performed on known carcinogens. Several of the chemicals we have selected for testing are associated with breast cancer risk in humans, but because there is more data available from laboratory animal studies, our analysis will focus on animal carcinogens. Our goal is to identify the assays that help predict whether a chemical will cause mammary gland tumors in animals, allowing researchers to screen many chemicals and flag the most hazardous ones or others that need further study.

Innovative elements:
ToxCast assays are going to be used to improve chemical testing, so it is important to develop new, breast cancer-relevant assays, as we propose in this project. The new assays will include tests for the kinds of changes in estrogen metabolism that occur in breast tissue, and the particular type DNA-damage specific to breast carcinogens. In addition, we will transfer approximately 100 ToxCast assays into breast cell systems and identify those that produce significantly different results in these sell systems. The project’s focus on rapid cell-based tests extends current innovation in chemical testing and will improve our ability to identify chemicals that might contribute to breast cancer. These assays can also be used to test mixtures, such as consumer products, house dust, drinking water, and even air samples. By testing many chemicals that cause mammary gland tumors in animal studies, we will also identify the specific mechanisms that cause some chemicals to affect breast cancer risk, helping understand how the disease occurs.

Advocacy involvement and relevance to the human issues associated with breast cancer:
The project arises directly from advocates’ concerns that chemical exposures represent a preventable cause of breast cancer, and that improved screening and evaluation of chemicals is a priority. We will work with the advocacy community through our Advisory Council and partnerships with non-profit organizations dedicated to promoting research on breast cancer and the environment. This will enable us to provide advocacy organizations with the information and materials to disseminate these research findings to their constituencies. Silent Spring Institute, a partner in the project, is a research organization founded by activists and experienced in community-based research and proactive dialogue with activists and policy-makers.




Progress Report 1 (2012)

Understanding how exposure to chemicals in the environment may raise the risk of breast cancer could offer clues to preventing the disease. Currently, the vast majority of chemicals found in homes, consumer products, and the environment have not been safety-tested. For those chemicals that are tested, most of the methods used are not designed to detect chemical effects specific to breast cancer, and they are typically take too long and cost too much to screen the tens of thousands of chemicals already on the market. Improving chemical testing methods was a primary research recommendation in several recent governmental reports, including one from the Institute of Medicine entitled “Breast Cancer and the Environment: A Life Course Approach,” the President’s Cancer Panel 2010 report, and also the recent Interagency Breast Cancer and Environment Research Coordinating Committee report on breast cancer and the environment. To increase the relevance of chemical testing to breast cancer, this project is developing new screening methods, adapting cell-based (in vitro) chemical tests for use in breast cells, and developing new tests, such as those for the mammary-cell specific enzymes involved in estrogen production. By conducting the new tests using animal mammary carcinogens, as well as chemicals that do not cause cancer in animal models, we aim to identify the tests that best predict which chemicals might contribute to the disease. These tests can be used to screen and prioritize the many chemicals that have not been safety-tested.

In the first year of the project, we made substantial progress on Aim 1, which is to test mammary carcinogens and noncarcinogens in a variety of in vitro tests using two different mammary cell models (MCF-7 and MCF10A). We finalized a list of 143 chemicals that we will test, categorizing them as mammary gland carcinogens, mammary gland development disruptors, and chemicals that were not carcinogenic in long term tests at the National Toxicology Program. Mammary gland carcinogens were further divided into more- and less-genotoxic. We made arrangements to obtain many of these chemicals from federal agencies currently involved in the Tox21 initiative to modernize chemicals testing. We updated our list of over 100 assays we plan to use to test the chemicals to reflect the rapid technological advances occurring in the field and to maximize comparability with Tox21 test programs. We finalized testing protocols and conducted initial experiments with 9 chemicals in 11 assays at 13 dose levels. In parallel with these efforts, the Yaswen laboratory continued its work to develop human mammary tissue models that better reflect tissue complexity. For example they began developing 3-dimensional tissue models that will include mammary epithelial and stromal cells. These more complex models may be used for assays in later stages of this project. The Leitman laboratory conducted initial work in a human BT474 breast cancer line that expresses both ER alpha and HER2 pathways and we are evaluating use of these models in order to identify chemicals activating these pathways. A project community advisory committee including representatives from women’s health and breast cancer organizations as well as state and federal regulatory agencies and NIH, was formed and met in a kickoff meeting in September 2012. The project was presented to the US Environmental Protection Agency National Center for Computational Toxicology as part of our efforts to ensure comparability of methods between our projects. In the coming year we plan to test over 100 chemicals in about that many assays and begin statistical analysis to identify tests that discriminate between carcinogens and non-carcinogens. Results will improve the ability to screen large numbers of chemicals as well as chemical mixtures, such as those in consumer products, house dust, drinking water, and air. The new screening tools could inform the design of safer chemicals (green chemistry), enable manufacturers to select better materials, help regulatory agencies identify chemicals of concern, and contribute to the understanding of environmental factors that contribute to breast cancer risk.




Progress Report 2 (2013)

In the second year of the project, we began compiling existing data and generating new cell screening data on our core set of 112 chemicals, comprising mammary gland carcinogens, mammary gland development disruptors, and chemicals that were not carcinogenic in long-term tests at the National Toxicology Program. We analyzed existing data on the genotoxic (DNA damaging) and hormonal activity of these chemicals, and showed that the mammary gland carcinogens are mostly genotoxic, while the non-carcinogens show much less genotoxicity. Mammary gland carcinogens and development disruptors are more likely to show hormonal activity than the non-carcinogens. We presented this analysis at the Society of Toxicology Annual Meeting and the California Breast Cancer Research Symposium. We tested all the chemicals using mammary cell cultures to see how chemicals affects key cell processes such as membrane permeability or mitochondrial function. In addition, we tested all the chemicals for estrogen receptor alpha and beta activity and androgen activity, and we tested a subset of chemicals to see how exposure affects gene expression for 260 genes of interest for breast cancer. We are doing these tests in mammary cell lines made from cancer tissue, and we are also developing ways to test normal breast tissue in these kinds of tests. We are also beginning to run the toxicity tests in co-cultures of mammary epithelial cells, the type that typically are represented in breast tumors, and neighboring cells called fibroblasts. These co-culture models may more accurately reflect normal tissue, which is made up of multiple cell types. Another key discovery is that in a cell culture model that contains both HER2 and estrogen receptors, as normal mammary epithelial cells do, chemicals that normally are weakly estrogenic become more potent when the HER2 receptor is activated. This is an important discovery because it means having a realistic cell culture system for the testing is important for generating accurate information about doses at which chemicals are active. We are in the process of analyzing the data from all these assays. In the coming year, we will continue testing our set of chemicals in different types of toxicity and gene expression tests and continue statistical analysis to identify tests that discriminate between carcinogens and non-carcinogens. We will also continue our work developing cell culture systems that reflect normal mammary tissue. This project will improve the ability to screen large numbers of chemicals as well as chemical mixtures, such as those in consumer products, house dust, drinking water, and air. We will continue working closely with scientists at the US Environmental Protection Agency to coordinate our findings with their programs for testing chemicals. The new screening tools could inform the design of safer chemicals (green chemistry), enable manufacturers to select better materials, help regulatory agencies identify chemicals of concern, and contribute to the understanding of environmental factors that contribute to breast cancer risk.

Publications:
Designing a broad-spectrum integrative approach for cancer prevention and treatment
Lower doses of common product ingredient might increase breast cancer risk
Parabens and Human Epidermal Growth Factor Receptor Ligands Cross-Talk in Breast Cancer Cells
Lotion ingredient paraben may be more potent carcinogen than thought
Parabens and Human Epidermal Growth Factor Receptor Ligands Cross-Talk in Breast Cancer Cells
Breast cancer risk increases with ingredient in shampoos, sunscreens