Researchers in this study wanted to understand why early full-term pregnancy lowers a woman’s risk of breast cancer, especially for the most common type of the disease. Although this protective effect has been observed for decades, the biological mechanisms behind it were not fully clear.
To investigate this, scientists analyzed normal breast tissue from women who had given birth (parous), those who had not (nulliparous), and women with BRCA1 or BRCA2 mutations, which increase breast cancer risk. They examined gene expression and molecular signaling across different types of breast cells to identify key differences.
The researchers found that pregnancy significantly affects a specific group of cells called CD44+ progenitor cells, which have stem-like properties and are thought to be potential starting points for cancer. In women who had given birth, these cells showed reduced activity in genes related to cell growth and stem cell function, including important signaling pathways. They also observed fewer cells expressing p27, a protein that regulates the cell cycle.
These findings suggest that pregnancy leads to long-lasting changes in breast tissue, reducing the number or activity of cells that are more likely to become cancerous.
