Cancer spreads faster in mice exposed to chronic, continuous stress

lymph

Nanospheres simulating cancer cells flowing through mice lymph vessels.  Under control conditions (top) and under stressful conditions (bottom). Source: bit.ly/1TcaGZG

Cancer spreads through the body by diffusion of cancerous cells from the primary tumor, via the blood vessels and lymphatic system into other parts of the body forming secondary tumors. It is thus of crucial importance to isolate and remove the cancerous cells as fast as possible, while ensuring that their rate of diffusion is reduced during treatment.

Clinical and epidemiological studies over the past 30 years have shown that chronic stress, depression and social isolation are linked to cancer progression. Currently, it has been established that stress hormones increase blood vessel formation, giving more channels of diffusion to cancer cells.

In this study, a group of scientists from Australia, Italy, Switzerland and USA, aimed to study if stress affected the rate of cancer cell diffusion through the lymphatic system as well. The lymphatic system is a network of tissues and organs that transport lymph, a fluid containing white blood cells, to help remove toxins and waste from the body.

They did so by subjecting mice to extreme and continuous stress and found that doing so released the stress hormone, adrenaline, which:

(i) activated the sympathetic nervous system (SNS) to increase the rate of lymph formation
(ii) increased the drainage capacity of lymph vessels connected to tumors.

In effect, allowing cancer cells more and faster avenues to flow out of the tumour and into the other parts of the body.

The researchers were also able to use a beta-blocker, propranolol, to reduce this flow through lymph vessels. The drug is being pilot-tested in a group of women with breast cancer in Melbourne, with hopes of developing a cheap and easy way to reduce the spread of cancer in afflicted patients.

The research paper was published in Nature Communications on 1 Mar 2016.

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