Toxicity Testing a Critical Tool for Breast
Cancer Prevention

The Pathways to Breast Cancer Report, which can be downloaded in full here

Breast cancer affects one out of every eight women in the United States,1 accounting for approximately 40,000 deaths in 2010.2 But with only about 10% of cases thought to be caused by inherited genes,3 scientists are increasingly focused on the role environmental factors play in disease development.

"Breast cancer is a leading cause of death among women in their prime years," reports Sarah Janssen, assistant clinical professor in the UCSF Division of Occupational and Environmental Medicine and senior scientist at the Natural Resources Defense Council (NRDC). "A lot of money and research has been put into better detection and treatment, and as a result, women are living longer with their illness. However, we still don't know what causes breast cancer, and we need more research focused on prevention."

A recent report co-authored by Janssen and Megan Schwarzman, Pathways to Breast Cancer: A Case Study for Innovation in Chemical Safety Evaluation, has provided an important first step to untangling the link between breast cancer and chemical pollutants in the environment. Schwarzman is an associate director of the Berkeley Center for Green Chemistry and research scientist in the School of Public Health.

Though breast cancer is hypothesized to be associated with industrial chemical exposure and the use of consumer products, little is known about the toxicity of tens of thousands of chemicals commonly used in the United States.4 While research is ongoing to address this data gap, Schwarzman points to the need to act in the short-term. "The project asked how to use current test methods and make decisions with what we know now."

For their investigation, Janssen and Schwarzman adopted the disease end-point approach developed by the National Academy of Sciences in their report, Toxicity Testing in 21st Century, which was co-authored by COEH faculty Gina Solomon, senior scientist for the NRDC and co-director of the OEM Residency program at UCSF.

It recommends scientists look upstream for early signs of disease, and where possible, use emerging laboratory tests capable of screening hundreds of chemicals in in vitro  high-throughput assays. "Our project was a way to put some flesh on the bones of that report by focusing on a specific disease like breast cancer," said Janssen.

To conduct the project, Schwarzman and Janssen convened a multidisciplinary expert panel representing the fields of cancer biology, toxicology, medicine, epidemiology, environmental justice, public health and public policy.

The panel first identified what scientists have already demonstrated to be early indicators of breast cancer development. Put simply by Janssen, "Before a tumor grows, what can predict that it will develop?" Examples included cell or tissue changes indicative of altered mammary gland development, and susceptibility factors such as obesity or early puberty.

The panel then developed a testing scheme, called the Hazard Identification Approach, to prioritize chemicals for testing and ultimately single-out chemicals that may raise the risk of breast cancer. They also identified gaps where assays have not yet been developed, and did a scientific review to pilot test the approach.4

"Our goal was to pilot this approach through the lens of breast cancer, rather than developing a boutique toxicity testing scheme unique to a single disease. Ideally, the same approach can be applied to other disease end-points and ultimately combined to form a comprehensive approach to chemical testing," said Schwarzman.

The project aims to dovetail with ongoing efforts to improve chemicals policy, including the regulatory process currently underway within California's Department of Toxic Substances Control as part of the state's Green Chemistry Initiative passed into law in 2008.5

"The pendulum is swinging," says Schwarzman. "A major motivator is the European chemicals regulation, REACH (Registration, Evaluation, Authorization and Restriction of Toxic Chemicals), which demonstrates that comprehensive chemicals policy reform can be done—the ship has sailed." This first-of-its kind regulation, which applies equally to chemical producers in Europe and abroad, requires manufacturers to  generate and disclose chemical information in a central database or face the loss of access to the largest market in the world.6

"Chemical producers must provide information, but what information?" Janssen asks. "Our report was a way to answer that question for a disease that is a major public health issue affecting millions of women. If we did a better job of identifying chemicals upfront that were linked to the disease we could prevent a lot of pain and suffering."

Pathways to Breast Cancer: A Case Study for Innovation in Chemical Safety Evaluation was produced by UC Berkeley and the Natural Resources Defense Council and funded by a special research initiative of the California Breast Cancer Research Program (CBCRP) to investigate the associations between breast cancer and the environment. Following its release, CBCRP issued a Request for Proposal with $5 million in funding for the development of assays identified as gaps in the report.

Download a full copy of the report (pdf)

4 "Pathways to Breast Cancer: A Case Study for Innovation in Chemical Safety Evaluation." A report of the Breast Cancer and Chemicals Policy Project produced by the University of California, Berkeley, and the Natural Resources Defense Council, with funding from the California Breast Cancer Research Program, University of California Office of the President.

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