Dec. 2 (UPI) -- Stress hormones and immune cells called neutrophils may awaken dormant cancer cells and cause tumors to regrow -- even after treatment -- according to a study published Wednesday by Science Translational Medicine.
The findings may explain why cancers can return long after seemingly being cured with chemotherapy or surgery, the researchers said.
In addition, targeting stress hormones with U.S. Food and Drug Administration-approved beta-blockers, typically used to treat irregular heartbeats, potentially could help prevent tumors from returning, they said.
"Tumor recurrence may be facilitated by common stress," study co-author Dr. Dmitry Gabrilovich told UPI.
Given that "cancer associated anxiety -- fear of death, issues with finances, families, etc. -- is extremely common, the most effective steps people can do [to reduce risk for recurrence] is manage their stress," said Gabrilovich, a chief scientist with drugmaker AstraZeneca.
Stress hormones such as cortisol, which are released into the bloodstream when the human body perceives stress, have been linked with an increased risk for a number of health problems, according to the Mayo Clinic.
As elevated levels of these hormones can increase a person's heart rate and lead to rises in blood pressure, they may lead to heart disease and sleep problems, as well as mental health disorders such as anxiety and depression, the Mayo Clinic says.
However, their exact role in cancer remains unknown, Gabrilovich and his colleagues said.
Tumor recurrence is a major cause of death in cancer patients, but it's also unclear exactly what biological mechanisms prompt cancer cells to accumulate, they said.
For their study, the researchers performed experiments in mice and 80 human patients with lung cancer.
After exposing the mice to stressful situations, the animals' levels of stress hormones rose, causing neutrophils -- cells produced by the immune system -- to release proteins and fatty molecules that in turn prompted tumor cells to reawaken, they found.
However, tumor cells remained dormant in stressed-out mice that received an experimental beta-blocker, the researchers said.
In addition, in blood samples from 80 patients who had their lung cancers surgically removed, those with higher concentrations of the proteins were more likely to have experienced tumor recurrence 33 months after surgery, according to the researchers.
Beta-blockers, including metoprolol and propranolol, or other prescription medications that target these proteins, should be evaluated as potential therapies to prevent tumor recurrence, they said.
"Since stress is unavoidable, we and others will try to find ways to target [with prescription drugs] those mechanisms that are responsible for tumor recurrence," Gabrilovich said.