Envision zero breast cancer

In this third blog in our series exploring how chemical mixtures relate to breast cancer risk, we explain what DNA methylation is and how it is relevant to a groundbreaking new research study. (Read the first blog explaining the study background and the second blog explaining non-targeted analysis.)

The study is led by Dr. Kimberly Badal from the University of California, San Francisco, with help from Dr. Hannah Lui Park from University of California, Irvine and other researchers. It aims to find out which individual chemicals and chemical mixtures are linked to breast cancer. The study will give insight into how we can reduce exposure to chemicals to lower the risk of getting breast cancer. We interviewed Dr. Park about DNA methylation, the method she brings to the study.

What is DNA Methylation?

DNA is a complex molecule found in the cells of a living organism that contains the genetic instructions needed for that organism to function. A gene is a specific segment of DNA that codes for a particular trait or biological function.

Now imagine your DNA as a library full of books. Each book represents a gene that contains instructions for how your body should work. Think of DNA methylation as putting sticky notes on certain pages of these books. These sticky notes can either hide the instructions on those pages or highlight them.

When a sticky note hides a page, it means that the information on that page can't be read and used by the body. This is like turning off a gene. On the other hand, if the sticky note highlights a page, it makes it easier for the body to read and use the instructions on that page, like turning a gene on or keeping it active.

Humans are born with a set of DNA instructions that cannot be changed. However, the environment and lifestyle can affect which genes are methylated – turned on and off. This makes sure the right instructions are used at the right time to keep the human body working properly.

How does this apply to breast cancer?

Existing breast cancer risk prediction models mainly rely on clinical factors like family history and the number of children a woman has had. Breast cancer risk prediction models developed over the last 20 years weren’t very accurate. Until more recently, they performed only slightly better than a coin toss. These models have improved significantly over time with the use of artificial intelligence, but there is still more room for improvement. Better risk prediction can help guide screening and prevention strategies, like determining who should undergo earlier and more frequent screening.

DNA methylation can help assess the risk of diseases. In cancer cells and precancerous cells, the patterns of DNA methylation (the sticky notes) are different from those of healthy cells. This might help us detect cancer early. The patterns can also reflect human lifestyle factors, such as diet and exercise habits, and environmental factors, such as chemical exposures from air pollution and personal care products.

What is the role of DNA methylation in this research project?

Dr. Park’s role in the study is to identify DNA methylation markers in blood samples that are linked to chemical exposures and lifestyle factors. While this research focuses on breast cancer, Dr. Park is analyzing DNA from white blood cells because it is less invasive to collect than breast tissue and can still provide valuable information about how the body responds to chemical exposures. The study accounts for different cell types, age, race, ethnicity, and other factors to ensure accurate results.

Even if someone has a healthy lifestyle by exercising regularly, eating healthfully, sleeping well, etc., they might still get breast cancer. DNA methylation from chemical mixtures may help explain why. The researchers’ goal is to identify methylation markers for a variety of chemicals to see if there is a connection between these exposures and breast cancer risk. By doing this, the researchers hope to improve the ability to predict which women might develop breast cancer and whether they are at risk of a more aggressive form of the disease.

For example, the methylation markers linked to cigarette smoking are not the same as those linked to obesity. With all the various chemicals we're exposed to, it's likely that different chemicals will be associated with different DNA methylation markers. It's possible that the study may find certain chemicals are linked to certain types of breast cancer.

Future goals

Dr. Park hopes that this research and similar studies will eventually help create a comprehensive and more accurate breast cancer risk assessment tool that combines clinical factors, such as family history, number of children a woman has had, plus genetic risk for the disease, and information about DNA methylation. This improved, more personalized breast cancer risk prediction model would help people know which lifestyle and environmental factors to focus on improving, as well as inform screening protocols so those who have greater risk for the disease have screening earlier and more often.

Zero Breast Cancer (ZBC) at Collaborative for Health & Environment (CHE) offers breast cancer prevention and survivorship health and wellness programs, including a health and wellness coaching program. We also provide resources on breast cancer prevention for audiences of all ages — from five-year-old children through survivors.

For more than 28 years, ZBC has centered community perspectives in our program and resource development. To illustrate how this works, I’m going to explain the development of our bilingual Generations/Generacionesresources about the impact of endocrine disrupting chemicals (EDCs) across generations.

Read the full blog on CHE's blog. 

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