Stress promotes tumor growth in mice

In a 2006 article in Nature Medicine (Thaker, P. H. et al, Nature Medicine, v 12 no 8 Aug 2006, p 939-44) researchers showed that chronic stress resulted in an increase in the number and size of human tumors (ovarian carcinomas) inoculated into mice. After inoculation, the mice were physically restrained in order to induce stress. Mice don't like to sit still on their own, and apparently they really don't like to be placed in some contraption for a few hours.

After the stress period, the number and size of the tumors was determined in stressed mice. The results showed that stressed mice had 2-3 times more tumors that were 2-3 times larger than mice that were not stressed. Another interesting result was that animals put into social isolation had a similar response to those that were stressed.

The researchers showed that the increase in number and size was directly related to an increase in the number of blood vessels forming in the tumors. Tumors, like all other tissues, rely on a supply of nutrients to grow, and blood serves that purpose. The more blood vessels in a tumor, the more nutrients it receives and thus is able to grow and spread.

What is really exciting about this research is that they were able to show what causes this phenomenon at a biochemical level. When an animal becomes stressed, chemicals called catecholamines are released by the brain into the blood. These chemicals can bind to cells in the body, including tumor cells, to signal stress. However, in some tumor cells, that signal is interpreted as "make more blood vessels". This in turn causes more blood flow to the growing tumor, which then increases the tumor size and its ability to spread to other areas.

So now there is biochemical evidence that stress influences tumor growth. Although this work only describes the stress effect in a particular type of tumor in an animal model, hopefully future work like it will provide more information on this phenomenon. Stress management should become more integrated in the treatment of cancer, and work like this will help to promote that idea. In the interim, if you are battling cancer, do seek out ways to manage your stress. I can't hurt. If you need help, this is a good list from Oklahoma State Univeristy of links to stress management sites:

http://www.pp.okstate.edu/ehs/links/stress.htm