Social isolation affects breast cancer outcome in mice, say US scientists

In collaboration with the Press Association

US scientists have found that mice who are isolated from their peers appear to be more stressed and have a worse prognosis for breast cancer.

But a spokesman for Cancer Research UK noted that there is no evidence that a similar effect can worsen cancer outcomes in people.

Scientists at the University of Chicago bred mice which were genetically prone to developing breast tumours.

They kept some in isolation as soon as they were taken away from their mothers, while others were moved into housing with other mice.

The researchers found that mice which were stressed because of their social isolation tended to develop much larger breast tumours than those which were housed with others.

In addition, the isolated mice developed stronger stress responses, as measured by their levels of the hormone corticosterone.

Dr Suzanne Conzen, associate professor in the department of medicine and the Ben May department for cancer research at the University of Chicago, commented: "Despite the genetic similarity of the mice assigned to grouped versus isolated housing, living in the stressful environment was associated with greater tumour size."

The scientist said that this suggests social environment may actually "alter the biology of cancer growth", although how this happens is not yet clear.

Analysis revealed that isolated mice showed differences in the expression of certain genes involved in various metabolic pathways that play a role in tumour growth.

But Oliver Childs, Cancer Research UK's senior cancer information officer, cautioned against leaping to conclusions from the results:

"These experiments were carried out in mice, so certainly don't prove that the stress caused by social isolation causes cancer to get worse in humans.

"It is now widely recognised that stress plays a part in illness. But no one really knows how much and there is no good evidence from controlled studies that stress contributes to cancer progression."

References

Williams, J., Pang, D., Delgado, B., Kocherginsky, M., Tretiakova, M., Krausz, T., Pan, D., He, J., McClintock, M., & Conzen, S. (2009). A Model of Gene-Environment Interaction Reveals Altered Mammary Gland Gene Expression and Increased Tumor Growth following Social Isolation Cancer Prevention Research, 2 (10), 850-861 DOI: 10.1158/1940-6207.CAPR-08-0238