Photo/IllutrationA thesis on the correlation between stress and breast cancer was published in Nature Neuroscience on July 8. (Yuri Oiwa)

Feelings of stress, including anxiety, fear and anger, increase the spread of breast cancer and heighten the recurrence rate, a study at the cellular level showed.

The confirmed correlation could lead to the development of cancer treatments using genetic manipulation to halt the activities of sympathetic nerves, which are activated when the patient is under stress, the research team said.

“If patients can control their anxieties, anger and other stresses, they could prevent an over-stimulation of their sympathetic nerves, which could have a positive influence (in curbing the progression of their cancers),” said Atsunori Kamiya, a professor of cell physiology at Okayama University and a member of the research team.

Kamiya and researchers at the National Cancer Center (NCC) announced the results of their study in the online Nature Neuroscience on July 8.

Epidemiological surveys had pointed out a connection between the activities of sympathetic nerves and the progression of cancer. However, details of the correlation had been unclear.

The researchers focused on sympathetic nerves in breast cancer tumors among 29 patients who had undergone surgery at the NCC.

They found that patients with higher densities of sympathetic nerves in the tumors were more likely to suffer a recurrence of cancer.

The team also stimulated sympathetic nerves in human breast cancer tumors that had been transplanted in mice.

After 60 days, the size of tumors nearly doubled compared with those in the mice that did not receive the nerve stimulation.

The number of metastases, or secondary malignant growths, in the stimulated mice was also larger.

When the researchers manipulated the genes in mice to prevent the activation of the sympathetic nerves, the size of the cancer was almost unchanged, even after 60 days. There were also no signs of metastases.

So far, medical treatments for cancer have centered on surgery, drug therapies and radiotherapies.

If genetic manipulation can curb the activities of sympathetic nerves in certain areas of tumors in humans, “a new option called ‘nerve treatment’ may appear for cancer patients,” Kamiya said.

A thesis written by Kamiya’s group can be read at (https://nature.com/articles/s41593-019-0430-3).