According to a meta-analysis published in The Lancet in 2002, the risk of breast cancer would decrease by 7% after each new full-term pregnancyemphasizes the Foundation for Medical Research (source 1).
A recent study conducted on mice by a team of researchers from the Cold Spring Harbor Laboratory (United States) confirms that pregnancy would indeed prevent the formation of cancerous tumours. The results, published in the journal Cell Reports (source 2), establish a link between pregnancy and the immune system in the prevention of breast cancer.
To reach this discovery, they carried out different experiments on female mice that had already given birth and female mice that had never given birth. “We used single-cell RNA sequencing to profile the composition of epithelial and non-epithelial cells in mammary tissue” from rodents, they state in their study.
Certain immune cells prevent tumor formation
Scientists have found that after pregnancy, breast cells call upon specialized immune cellscells“Natural Killer T” (or NKT lymphocytes), to prevent tumor formation. And these specific cells would be observed only in the mammary gland. “We do not see this expansion elsewhere in the body, even if NKT cells are present everywhere else in the body”, specifies researcher Amritha Varshini Hanasoge Somasundara, co-author of the study.
“One of the hypotheses we are currently working on is: the late pregnancies do they lead to the same expansion of the same immune cell subtypes?” she adds.
The next steps are to demonstrate that similar results can be observed in humans and to try to translate these results into means of preventing breast cancer, “particularly by figuring out how to induce an abundance of NKT cells in breast tissue as women age and go through menopause.”