Cellular transformations that enable breastfeeding can also spur cancerous tumours in older expectant mothers, the new research reveals.
“Our study found something very important,” said senior author Justin Stebbing, Professor of Biomedical Sciences at Anglia Ruskin University.
“Pregnancy can actually change the genetic makeup of breast tissue Just like wrinkles appear on our skin as we get older, changes can also happen in the DNA of breast cells over time… pregnancy adds an extra element to these changes.”
The researchers evaluated first-time mothers in a variety of age groups and discovered that those in the 35 to 55 years range had larger numbers of mutated cells.
Previous research had established that mothers in that age range face a 30 percent increased risk of breast cancer, but until now it was not known why.
Dr Bianca Castrella from Imperial’s Department of Surgery and Cancer, and lead author of the study, said:
“We found that the human breast, like other organs, accumulates mutations with age. “Also that pregnancy has an additional effect meaning, that older first-time mothers might have a higher chance of developing harmful changes in their breast cells compared to other women.”
The research was published this week in the journal Nature Communications. The Imperial College London team revealed that the dataset of mutations they had discovered could now be used as a reference for other breast cancer researchers, spurring hope of a progressive step forward in the disease battle.
“Nobody has looked at the entire genome of the healthy breast before,” Dr Castrella said. It is thought future tests could one day detect the newly-identified mutated cells and help older mothers evaluate their risk of cancer.
The team examined healthy breast cells from women who had given birth at different ages and also women who did not have any children.
None of the donors were carrying inherited mutations in the two genes known to significantly increase the risk of breast and ovarian cancer
The researchers, who sequenced the entire genomes of 29 frozen healthy breast tissues from donors, discovered that breast tissue typically accumulates approximately 15 mutations a year.
Imperial College London said it is the first time such a study has ever been performed.