Both studies looked at mice at puberty that were housed individually compared with mice housed in groups. Conzen and colleagues found that social isolation altered the expression of certain genes, increasing tumor growth. Schuler and colleagues found that social isolation affected breast cancer development, but that the connection between environmental stressors and cancer may not be as clear as initially hypothesized.
Although the results of the two studies differed slightly, Kerr said that important result is that the environment, specifically the psychosocial environment, likely affects cancer risk.
"In contrast to these studies, ours was designed to show whether neonatal experiences, including either mild or moderate stress because of maternal separation experiences, affect normal breast development or predisposed the animal to carcinogen-induced breast cancer," Kerr said.
Kerr and colleagues examined how either brief maternal separation for 15 minutes daily or prolonged separation for four hours daily during the first three weeks of life influenced the development of normal and cancerous mammary gland development in female mice. These mice were compared with mice that did not experience any maternal separation.
When the mice reached puberty and young adulthood, the researchers measured the levels of estrogen receptor alpha and p53, the levels of which have been linked to breast cancer development in prior research. All the mice were then exposed to a known carcinogen in order to assess breast tumor incidence and invasiveness.
The researchers found that 300 days after exposure to the carcinogen 53 percent of the mice exposed to prolonged separation had developed palpable breast lesions compared with 20 percent of mice exposed to brief or no maternal separation. The cancers in mice with prolonged sepa
|Contact: Jeremy Moore|
American Association for Cancer Research