Rodent of the Week: Mice reveal how stress fuels the spread of breast cancer

Stress is bad. Breast cancer is bad. Put them together and things get even worse.

That’s what UCLA researchers discovered as they watched breast cancer tumors spread through the bodies of mice. Those tumors spread faster inside the mice that were stressed -- because they had to spend part of each day confined to a small space -- than in the mice that were not.

Stress did not appear to affect the original cancer. But once a malignancy was established, stress helped it to metastasize.

Here’s what was going on inside the mice:

The cancer prompted the immune system to dispatch white blood cells called macrophages to the site of the tumor. Macrophages try to help repair damaged tissues by initiating an inflammatory response, which is how the body normally tries to heal itself. But in the case of cancer, it can backfire -- some of the compounds produced as part of the inflammatory response wind up helping the tumor cells cheat death and proliferate.

The problem with stress is that it causes the body to send more macrophages to the tumor site.

“Stress helps the cancer climb over the fence and get out into the big, wide world of the rest of the body,” UCLA researcher Steven Cole, the study’s lead author, said in a statement.

The good news is that researchers figured out a way to counteract this. By giving the stressed-out mice beta blockers, the macrophages became oblivious to the fact that more of them were being summoned in response to stress.

Researchers at the UCLA’s Jonsson Cancer Center are looking for epidemiological evidence that beta blockers suppress the spread of breast cancer in people. If they can find it, they would like to launch a clinical trial testing beta blockers in breast cancer patients.

The findings were published Sept. 15 in the journal Cancer Research.

-- Karen Kaplan/Los Angeles Times