Breast cancer is the most common cancer in women around the world. Although treatments have improved greatly over the years, some forms of breast cancer remain especially dangerous.
Scientists have long known that women with obesity face a higher risk of developing breast cancer after menopause and often have poorer outcomes. However, exactly why this happens has remained a puzzle.
Now, researchers at Georgetown University believe they have found an important piece of the answer. Their new study points to a little-known hormone called estrone, which may play a major role in making certain breast cancers grow faster and become more aggressive in postmenopausal women with obesity.
The research was published in the journal Nature Reviews Endocrinology.
The scientists focused on estrogen receptor-positive breast cancer, also known as ER-positive breast cancer. This is the most common type of breast cancer diagnosed after menopause. In this disease, cancer cells use estrogen to help them survive and grow. It is also one of the deadliest forms of breast cancer in older women.
According to Dr. Joyce Slingerland of Georgetown University’s Lombardi Comprehensive Cancer Center, postmenopausal women with obesity are not only more likely to develop ER-positive breast cancer, but they are also two to three times more likely to die from it than women who are not obese.
This is especially concerning because obesity rates continue to rise. Researchers estimate that by the end of this decade, nearly half of all women in the United States may be living with obesity.
The hormone at the center of the new findings is estrone. Before menopause, the ovaries mainly produce a different form of estrogen called estradiol. Estradiol has many important jobs in the body and also helps control inflammation.
Menopause changes this balance dramatically. When women stop menstruating, levels of estradiol drop sharply. At the same time, estrone becomes the main type of estrogen in the body. Unlike estradiol, estrone is produced mainly in fat tissue.
Although estrone and estradiol look very similar chemically, they do not behave in the same way.
Dr. Slingerland’s team found that estradiol can reduce inflammation by blocking certain proteins that trigger inflammatory responses. Estrone, however, appears to do the opposite. It works together with inflammatory proteins and switches on genes that create and maintain inflammation.
This finding is important because chronic inflammation is known to help cancer cells grow, spread, and become more aggressive.
Women with obesity often have much higher levels of estrone. The researchers found that estrone levels can be two to four times higher in fat tissue, breast tissue, and other parts of the body in women with obesity. This creates an environment where inflammation becomes stronger and more persistent.
Earlier studies from Dr. Slingerland’s laboratory showed that estrone can activate genes that push normal cells toward cancer. It can also switch on biological processes that help cancer cells spread to other parts of the body.
The team also studied breast tumors in mice. They found that tumors exposed to estrone grew much faster and spread more widely than tumors exposed to estradiol. In addition, there was evidence that estrone may weaken the immune system’s ability to recognize and destroy cancer cells. This gives tumors even more opportunity to grow unchecked.
These findings suggest that estrone is not simply a harmless hormone that appears after menopause. Instead, it may actively fuel inflammation, cancer growth, and cancer spread, particularly in women with obesity.
Because estrone is produced in fat tissue, reducing body fat may help lower estrone levels and decrease the inflammation it causes. This has led researchers to consider whether modern weight-loss medications could become part of future breast cancer treatment.
Drugs known as GLP-1 receptor agonists, including medicines such as Ozempic and Wegovy, have already changed the treatment of obesity by helping many people lose significant amounts of body fat.
Researchers believe these medications may eventually help women with ER-positive breast cancer by lowering estrone levels and reducing the inflammation that promotes tumor growth.
Lifestyle changes such as eating a healthy diet and exercising regularly can also lower body weight and reduce inflammation. However, maintaining these changes over many years can be difficult for many people. GLP-1 drugs may offer another option for achieving long-term reductions in body fat and potentially improving cancer outcomes.
The new findings suggest that treating breast cancer in postmenopausal women with obesity may require a broader approach. Instead of focusing only on the tumor itself, doctors may also need to address the hormonal and inflammatory environment created by excess fat tissue.
Although more studies are needed, including clinical trials that test GLP-1 drugs in breast cancer patients, this research offers new hope. Understanding the role of estrone could eventually lead to better treatments and improved survival for many women facing one of the most common and deadly forms of breast cancer.
If you care about breast cancer, please read studies about a major cause of deadly breast cancer, and this daily vitamin is critical to cancer prevention.
For more information about cancer, please see recent studies that new cancer treatment could reawaken the immune system, and results showing vitamin D can cut cancer death risk.
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