UCLA’s Jonsson Comprehensive Cancer Center found that stress acts as a sort of fertilizer to the growth of breast cancer in mice in that it redirects the immune cells that exist to ward off the disease.
Researchers discovered a 30-fold increase in cancer progression in the bodies of stressed mice when compared to those that were not stressed.
While there has long been evidence to support the theory that stress fuels cancer in humans, this particular study identifies the pathway that changes the makeup of immune cells — causing them to become agents of harm as opposed to agents of healing and protection. By identifying this pathway, researchers hope to gain new insight into the roadmap of how cancer reaches the much harder to treat distant organs of the body.
“What we showed for the first time is that chronic stress causes cancer cells to escape from the primary tumor and colonize distant organs,” said Erica Sloan, a Jonsson Cancer Center scientist, first author of the study and a researcher with the Cousins Center for Psychoneuroimmunology. “We not only showed that this happens, but we showed how stress talks to the tumor and helps it to spread.”
In addition to documenting the effects of stress on cancer metastasis, the researchers were also able to block those effects by treating stressed animals with drugs that block the nervous system’s reprogramming of the metastasis-promoting immune cells, called macrophages.
In this two-week study, mice with breast cancer were divided into two groups—one confined to a small area for short periods of time each day, while the other experienced no confinement.
The mice were genetically engineered to include the luciferase gene, which provides a firefly glow. In turn, they were able to monitor the spread of cancer by tracking the luciferase signal.
Cole noted that the primary tumors remained unaffected by stress but the stressed animals showed significantly more metastases throughout the body.
“This study is not saying that stress causes cancer, but it does show that stress can help support cancer once it has developed,” Cole said. “Stress helps the cancer climb over the fence and get out into the big, wide world of the rest of the body.”
Beta blockers, used in this study to shut down the stress pathways in the mice, are currently being examined in several large breast cancer databases for their role in potential prevention of recurrence and cancer spread, said Dr. Patricia Ganz, director of cancer prevention and control research at UCLA’s Jonsson Comprehensive Cancer Center.
If findings suggest benefit, the next step could lead to early phase clinical at the Jonsson Cancer Center to test beta blockers as a means of preventing breast cancer recurrence. Healthy lifestyle factors to reduce stress may also have influence on these biological pathways, the study suggests.
“We’re going to be focusing on younger women, because they may have a multitude of things weighing on them when they’re diagnosed with breast cancer. Younger women have more significant life demands and typically are under more stress,” Ganz said, adding that “because of this study, we may be able to say to a patient in the future that if you follow this exercise regimen, meditative practice or take this pill every day it will help prevent recurrence of your cancer. We can now test these potential interventions in the animal model and move those that are effective into the clinic.”
The study can be found in the Sept. 15, 2010 issue of the peer-reviewed journal Cancer Research.