A teen or early pregnancy have been linked to a drop in the risk of breast cancer by 50%, a new study published in BioMed Central’s Breast Cancer Research finds.

Researchers found that the Wnt/Notch signalling ratio was reduced in the breast tissue of mice that gave birth, compared to virgin mice among the same age group. Wnt and Notch are two separate pathways of a system which control cellular fate within an organism.

This suggests that pathways are changed in women 20 years or younger who give birth – resulting in a 50% drop in breast cancer risk.

Lead author Mohamed Bentires-Alj, of the Friedrich Miescher Institute for Biomedical Research, 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.”

It has been known that early pregnancy has a strong protective outcome against breast cancer in humans and rodents, however, exactly why this occurs has been a mystery.

A separate study presented at the AACR (American Association for Cancer Research) 102nd Annual Meeting in 2011 suggested that women who have given birth, especially early on in life, have an overall reduced risk of breast cancer, compared with women who have not.

Researchers from Basel used micoarray analysis and found that genes involved in the immune system and differentiation were up-regulated after pregnancy, while the activity of genes coding for growth factors decreased.

The activity of Wnt4 was down-regulated after pregnancy. The protein from Wnt4 is a feminizing protein, and not having it encourages an embryo to develop as a boy.

When the researchers examined 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 changed in the basal stem/progenitor cells of mammary tissue of mice due to pregnancy.

The study authors believe their research begins to shed light on the long-term results of an early pregnancy. Additionally, it leads the way for future research to examine whether inhibitors of the Wnt pathway could possibly be used to mimic the parity-induced protective outcome against breast cancer.

Written by Kelly Fitzgerald