Women who have children, particularly early in life, have a lower lifetime risk of breast cancer compared with women who do not. Now, Fox Chase Cancer Center researchers have identified a gene expression pattern in breast tissue that differs between post-menopausal women who had children and post-menopausal women who did not. The results will help scientists understand why pregnancy reduces breast cancer risk and may help them develop chemopreventive strategies that can provide similar protection for women who did not have children. Pregnancy triggers differentiation and growth of breast tissue; however breast tissue in post-menopausal women looks similar regardless of childbearing history. That similarity has left researchers wondering why pregnancy is protective throughout a woman's life. This study starts to explain that effect, says Dr. Ricardo López de Cicco, a senior research associate at Fox Chase, who presented the work at the American Association for Cancer Research (AACR) 102nd Annual Meeting 2011 on April 5, 2011. "When a woman has multiple pregnancies beginning at a relatively young age, we see a protective effect against breast cancer," Dr. Lopez says. "In this study, we identified a post-pregnancy genomic signature that can still be seen even after menopause. That is very important because it could begin to help us understand why women who have children early benefit from a reduced risk of breast cancer throughout their lives." By comparing gene expression in breast tissue from 44 post-menopausal women who had children and 21 post-menopausal women who did not, the team identified 208 genes that are differentially expressed. The signature was subsequently validated in an independent cohort of 61 post-menopausal women, 38 who had children and 23 who did not.Login Or Register To Read Full Story