Deadly breast cancer cells grow faster when surrounded by fatty tissue, and that could have tremendous public health implications as obesity rates increase.
Researchers from the University of North Carolina Lineberger studied an aggressive form of the disease known as triple-negative breast cancer, which affects up to 20 percent of women who develop breast cancer.
In a study that was meant to simulate different environments often faced within the human body, they compared how quickly the cancer cells spread based on the proximity and amount of adipose tissue.
“We’re interested in something called the ‘microenvironment,’ which is basically cells around the tumor and the chemicals those cells produce,” said Dr. Liza Makowski, University of North Carolina Lineberger member and associate professor in the university’s Gillings School of Global Public Health.
“In breast cancer, we know that the cancer is embedded in very fatty tissue, because the breast is made up largely of adipose tissue. As a person becomes obese, that can change the adipose tissue, or change this microenvironment where the cancer can start or progress,” explained Makowski.
Previous research has shown that obesity is directly related to increased cancer risk, including a host of common cancers affecting both men and women, but the new study suggests that cancer essentially thrives in an adipose environment.
The study authors report that “tumors were significantly larger in the obese models than in the lean models,” according to the studies performed on mice. The authors add that mice that had previously been obese saw slower cancer growth, suggesting that “weight loss corrected changes to the microenvironment that were helping drive the cancer.”
Extrapolating the Study to Humans
The researchers assessed gene expressions that were taking place within the tumors and discovered “extremely subtle” changes among the test subjects. However, the changing gene expressions could not alone be responsible for the significant acceleration in tumor growth when obesity was present.
Again the researchers point to the environment surrounding the cancer cells as the likely driver of change. “Where we saw the most changes were in the mammary glands around the tumors,” said author Alyssa J. Cozzo, a graduate student with the University of North Carolina’s Gillings School of Global Public Health.
“This implies that the microenvironment surrounding the tumor can be a driver of tumor growth, even when the tumor cells and the other cells that make up the tumor itself are relatively similar,” added Cozzo.
As the medical community continues to piece together the links between obesity and cancer, the researchers believe that their new analysis sheds important light on the topic.
“Our take-home message for this study was that, indeed, the obese microenvironment (the mammary gland surrounding the tumor) can drive tumor growth even when the tumor cells come from a lean mouse, and, critically, the obese environment can be partially or completely reversed by weight loss,” said Makowski. “It’s as if the cells do not ‘remember’ the obese exposure.”
These findings could lead to health interventions aiming to drive weight loss and other health implications.