What was interesting, Cole said, was that the primary tumors did not seem to be affected by stress and grew similarly in both groups of mice. However, the stressed animals showed significantly more metastases throughout the body than did the control group. The cancer, in effect, acted differently in the stressed mice.
"This study is not saying that stress causes cancer, but it does show that stress can help support cancer once it has developed," Cole said. "Stress helps the cancer climb over the fence and get out into the big, wide world of the rest of the body."
Cole said Sloan detailed the biology of the stress-induced changes in the cancer cells along every step of the pathway, providing a road map by which stress promotes cancer metastasis. Additionally, she proved that using beta blockers in stressed mice prevented the same cancer progression seen in the stressed mice that did not receive medication.
When cancer occurs, the immune system sends out macrophages to try to repair the tissue damage caused by uncontrolled growth of cancer cells. The macrophages, in an attempt to help, turn on inflammation genes that are part of the normal immune response to injury. However, the cancer cells feed on the growth factors involved in a normal immune response. Blood vessels that are grown to aid healing instead feed the cancer the oxygen and nutrients it needs to grow and spread, and the extra cellular matrix, which provides structural support for normal cells, is attacked during the immune response, In Sloan's study, mice with breast cancer were divided into two groups. One group of mice was confined in a small area for a short period of time every day for two weeks, while the other group was not. helping the cancer cells escape from the primary tumor and spread to distan
|Contact: Kim Irwin|
University of California - Los Angeles