Scientists Reveal Why Teen Pregnancy Halves the Risk of Breast Cancer
Scientists have long puzzled over why early pregnancy protects women from breast cancer. Researchers say early pregnancy protects humans and rodents against breast cancer. Previous research found that having a child before the age of 20 decreases a woman's risk of breast cancer by half.
Now a new study using microarray analysis on the breast tissue of mice that have given birth and virgin mice reveals that the decreased Wnt/Notch signaling ratio after pregnancy may be responsible for the reduced breast cancer risk.
Researchers found that genes involved in the immune system and differentiation were up-regulated after pregnancy while the activity of genes coding for growth factors was reduced.
The study also found that the activity of one particular gene Wnt4 was don-regulated after pregnancy. Researchers say the protein from the Wnt4 gene is a feminizing protein, and that the absence of this protein propels a fetus towards developing as a boy.
Researchers explain that Wnt and Notch are opposing components of a system, which controls cellular fate within an organism. After further analysis, researchers found that genes regulated by Notch were up-regulated. In other words, Notch-stimulating proteins were up-regulated and Notch-inhibiting proteins were down-regulated.
Researchers explain that Wnt/Notch signaling ratio was permanently altered in the basal stem/progenitor cells of mammary tissue of mice by pregnancy.
"The down-regulation of Wnt is the opposite of that seen in many cancers, and this tightened control of Wnt/Notch after pregnancy may be preventing the runaway growth present in cancer," lead researcher Mohamed Bentires-Alj from the Friedrich Miescher Institute for Biomedical Research in Basel, Switzerland said in a news release.