Social Isolation Adversely Affects Breast Cancer

Sept. 30 -- TUESDAY, Sept. 29 (HealthDay News) -- A socially isolated, stressful environment can speed up the growth of breast cancer, researchers studying the effects of stress in animal models reported Tuesday.

Social isolation can actually change the expression of genes important in the growth of mammary gland tumors, according to Dr. Suzanne D. Conzen, an associate professor of medicine at the University of Chicago and the study's lead author.

"As far as we know, this is the first assessment of gene expression in mammary glands, looking at the molecular basis for differences in tumor development under the setting of social stress," Conzen said at a news conference Tuesday.

The findings, published in the October issue of Cancer Prevention Research, follow other studies, some in humans, that showed stress can adversely impact cancer. One study, for instance, found that stressful marriages are bad for breast cancer recovery.

Conzen and her colleagues randomly assigned mice that were genetically susceptible to breast cancer to live either in isolation or in group housing.

"We separated the mice at a very young age, just a few days after they had been weaned from their mothers' milk," Conzen said. "Mice are social animals. In the wild, they live in groups of three or four. They have dramatic responses to isolation."

"What we found was the isolated mice developed larger and more breast cancers than the group-housed mice," she added.

Three and a half weeks into the isolation, Conzen's team measured gene expression in the animals' mammary glands, the equivalent of the human breast. "We found very reproducible changes in gene expression [in the isolated mice]. We found genes that were turned on and turned off that had to do with metabolism," she said. These pathways are known to contribute to increased growth of breast cancer, she added.

The isolated mice also had a higher corticosterone stress hormone response than did the group-housed mice.