Scientists have shown that stress causes cancers to grow and spread.
A team at Cold Spring Harbor Laboratory in New York discovered that chronic stress leads to the formation of sticky networks of white blood cells called neutrophils, which make it easier for cancer cells to invade tissues.
They conducted their research on laboratory mice that had breast cancer.
When the mice were subjected to stress, the risk of the cancer spreading further increased two to four times.
While the study appears to confirm that stress promotes cancer growth, it does not prove that stress causes tumors in the first place.
Mice exposed to stress (strobe lights, loud music, food deprivation) had larger tumors than the control group not exposed to stressful conditions.
Researchers have found that chronic stress can exacerbate the growth of cancer cells and their metastasis
Stress also affects other parts of the immune system, such as suppressing the actions of crucial immune cells, and making the lungs a more hospitable place for cancer cells to replicate.
Dr. Xue-Yan He, a researcher at Cold Spring Harbor Laboratory, said, “Stress is something we really can’t avoid in cancer patients.
‘You can imagine that if you are diagnosed, you can’t stop thinking about the illness, the insurance or the family. That is why it is very important to understand how stress acts on us.’
The mice had breast tumors and cancer that had spread to the lungs. They were divided into a control group and a group that would be subjected to stressful conditions.
In their study, stressed mice showed greater tumor growth and spread to the lungs than mice that were not under stressful conditions, such as being under constant bright light, sitting in a tilted cage, listening to loud noises, and deprived of food. .
Dr Mikala Egeblad, co-author of the study, said: “[I] I saw this terrifying increase in metastatic lesions in these animals. It was up to a four-fold increase in metastasis.’
Stress also caused a reduction in the number of immune cells, such as T cells and natural killer (NK) cells, while increasing the number of neutrophils traveling from the bloodstream and entering tumors.
Additionally, they discovered that the stress hormone corticosterone promoted the spread of cancer and caused lesions to form in the lungs of the mice.
It also deposited more protein called fibronectin, which promotes tumor cell invasion, and caused a decline in T cells, which normally suppress cancer growth.
Stressed mice had a two- to four-fold increase in lung metastases and lesions. CUMS stands for Chronic Unpredictable Mild Stress
The stressed mice also had more neutrophils circulating in the bloodstream.
Neutrophils release NETs, ​​or web-like networks of DNA and proteins, which normally defend us against invading microorganisms by trapping and killing them.
To confirm that stress triggers NET formation, Dr. He and his fellow researchers performed three tests.
First, the researchers removed neutrophils from the mice using antibodies. The animals were then injected with a drug that disrupts NETs.
Finally, they looked at mice whose neutrophils did not respond to glucocorticoids. Surprisingly, all three tests gave consistent results, according to Dr. He: “The stressed mice no longer developed metastasis,” indicating a crucial role of neutrophils and NET formation in stress-induced cancer metastasis. stress.
The team also found that chronic stress caused NET formation to modify lung tissue even in cancer-free mice.
Dr. Egeblad said, “It’s almost preparing the tissue to get cancer.”
Drugs targeting NET formations would aim to alter the environment surrounding a growing tumor in an effort to slow or stop its growth. Promising drug candidates may decrease inflammation, which would discourage tumor metastasis.
The main takeaway, according to Linda Van Aelst, a professor at Cold Spring Harbor Laboratory, is that “stress reduction should be a component of cancer treatment and prevention.”
Their research was published in the journal. cancer cell.