Getting pregnant at a young age is known to protect a woman against breast cancer, suggests study.
Researchers in BioMed Central found that Wnt/Notch signalling ratio is decreased in the breast tissue of mice which have given birth, compared to virgin mice of the same age.
In humans having a child before the age of 20 decreases risk of breast cancer by half.
The activity of one particular gene Wnt4 was also down-regulated after pregnancy.
The protein from this gene (Wnt4) is a feminising protein - absence of this protein propels a foetus towards developing as a boy.
Wnt and Notch are opposing components of a system which controls cellular fate within an organism and when the team looked at Notch they found that genes regulated by notch were up-regulated, Notch-stimulating proteins up-regulated and Notch-inhibiting proteins down-regulated.
Wnt/Notch signalling ratio was permanently altered in the basal stem/progenitor cells of mammary tissue of mice by pregnancy.
Mohamed Bentires-Alj from the Friedrich Miescher Institute for Biomedical Research, who led this study said, "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."
The research is published in the open access journal Breast Cancer Research.