Study Suggests How Obesity Affects Breast Cancer Cells
Obesity is linked to a higher risk of breast cancer, but whether excess weight affects any breast cancer that develops is unclear. A study has found that breast cancer cells have more inflammation and different mutations in women with a body mass index (BMI) of 30 or higher than in women with lower BMIs.
The research was published in the July 21, 2023, issue of Nature Communications. Read “Obesity-associated changes in molecular biology of primary breast cancer.”
About BMI
Doctors used BMI as an indicator of total body fat for many years. Still, because it doesn’t account for differences in racial and ethnic groups, genders, sexes, and ages, experts now see it as a flawed way to measure body fat.
But many studies still use BMI to classify people as overweight or obese. According to the U.S. National Institutes of Health, the BMI categories are:
BMI of less than 18.5: underweight
BMI of 18.5 to 24.9: normal weight
BMI of 25 to 29.9: overweight
BMI of 30 or higher: obese
About the study
We know that obesity increases the risk of developing breast cancer and also is linked to worse outcomes in people who are diagnosed. In this study, the researchers wanted to understand how the biology of breast cancer differs between women with higher BMIs and women with lower BMIs.
The researchers analyzed samples of breast cancer tissue from 2,071 women who had not yet received any treatment for the disease. The women were part of five studies that also collected information on BMI. No women were considered underweight according to their BMI.
Among the women in the study:
51% were considered at a healthy weight
33% were considered overweight
16% were considered obese
The researchers noted that overweight and obese women in the study were more likely to be diagnosed with larger tumors and more advanced-stage breast cancer.
Among women diagnosed with estrogen receptor-positive, HER2-negative breast cancer, women with a higher BMI were:
more likely to have CDH1 mutations; the CDH1 gene helps control cell growth, and mutations in the CDH1 gene are linked to diffuse stomach cancer and lobular breast cancer
more likely to have TBX3 mutations; the TBX3 gene also helps control cell growth, and TBX3 mutations are linked to breast, cervical, ovarian, pancreatic, lung, liver, bladder, and head and neck cancer, as well as melanoma
more likely to have PTEN mutations
less likely to have PIK3CA mutations
PTEN mutations are linked to a higher risk of developing breast cancer. PIK3CA mutations are found in about 40% of breast cancers.
Among women diagnosed with estrogen receptor-negative, HER2-negative breast cancer, women with a higher BMI were less likely to have a PTEN or TP53 mutation. Nearly 30% of all breast cancers have a TP53 mutation.
Among women diagnosed with estrogen receptor-positive, HER2-negative invasive lobular carcinoma, women with a higher BMI were:
more likely to have TBX3 mutations
more likely to have ARID1A mutations; the ARID1A gene helps control cell growth
less likely to have TP53 mutations
less likely to have RUNX1 mutations; the RUNX1 gene makes the RUNX1 protein, which is found in several types of cells in healthy breast tissue; when the gene mutates, levels of the protein are very low or zero, which may allow breast cancer to develop
less likely to have PIK3CA mutations
The researchers also looked at inflammation in the breast cancer cells and found that breast cancer cells were more likely to have inflammation in women with a higher BMI than in women at a healthy weight.
What this means for you
This study shows that breast cancer in women with higher BMIs is biologically different from breast cancer in women with lower BMIs.
And although the study doesn’t lead to any direct action steps for women diagnosed with breast cancer, it does add to our understanding of how obesity affects breast cancer once it develops.
In the future, the results of this study may be used to make treatments more personalized. For example, researchers may develop medicines that target the specific genetic mutations in breast cancer in women with higher BMIs.
— Last updated on August 31, 2023 at 9:05 PM