A new study has suggested that young mice separated from their mums for longer periods are likely to develop mammary tumors twice as fast as mice that experienced short or no maternal separation.
The results of this study, conducted by Leslie Kerr, of the Trent University and colleagues, have added to the increasing amount of research examining the effects of stress and other social experiences on cancer development.
"So far, we have not really understood, or really sifted through and found factors in the environment that cause a predisposition to the development of breast cancer, or any cancers," said Kerr.
Examining environmental effects related to breast cancer development is of increased interest because, like the brain, breast tissue develops postnatally.
This means that changes in developmental environment including changes in hormonal activity may increase an animal's risk for developing breast tumors, said Kerr.
Two other studies published in Cancer Prevention Research within the last year explored whether social isolation- another psychosocial stress-affected breast 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," said Kerr.
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.
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 separation were also more invasive.
In addition, mice exposed to prolonged separation had 200 percent greater expression of estrogen receptor alpha levels compared with mice that had no separation, and 30 percent higher levels than mice exposed to brief separation.
The research was published in Cancer Prevention Research, a journal of the American Association for Cancer Research.