Bhat-Nakshatri P, et al., 2022

Breast cancer doesn’t affect all women in the same way. Women from different backgrounds—including those with African, Indigenous American, or European roots—often experience differences in the age of diagnosis, the type of breast cancer, and how the disease progresses. While factors like access to healthcare are important, scientists are also exploring how biological differences tied to a person’s ancestry might contribute.

Our understanding of healthy breast tissue has grown in recent years, but researchers still don’t fully know how ancestry influences the biology of normal breast cells. This gap in knowledge matters because understanding what’s “normal” in different groups could help explain why breast cancer shows up and behaves differently across populations.

This study used cutting-edge tools to look at healthy breast tissue in women from a wide range of backgrounds. Their goal was to create a detailed map of the healthy breast and uncover how breast tissue might vary depending on a woman’s ancestral background.

Full-Text Journal Article PubMed

What did they study?

Researchers collected breast tissue from 92 healthy women with diverse ancestral backgrounds. The breast tissue in this study came from the Komen Tissue Bank. They used a technique that allowed them to look at individual cells and see which genes were active, as well as how the DNA was packaged—meaning how tightly or loosely it was folded. This packaging affects whether a gene is easy or hard for the cell to read, which helps determine how each cell behaves.

They focused on identifying the types of cells present in the breast and analyzing how gene activity and DNA packaging differed across those types. Special attention was given to epithelial cells, which line the milk ducts and lobules. These are the cells from which most breast cancers develop. The researchers also compared samples from different parts of the breast and looked at how gene activity changed with age or varied across ancestry groups.

What did they find?

1. Distinct Patterns in Breast Cell Types: The researchers found that different types of breast cells—especially the epithelial cells—had their own unique patterns of gene activity and DNA packaging. These differences help determine each cell’s role and behavior in the tissue, and they may also help explain why some cells are more likely than others to develop into cancer.
2. Differences Between Duct and Lobule Cells: Even though the ducts (which carry milk to the nipple) and lobules (which produce milk) are both key parts of the breast, the cells in these areas showed clear differences in gene activity. These differences were consistent across women and could help explain why different breast cancers arise in ducts versus lobules.
3. Changes Over Time: Some genes changed their activity as women aged, especially those involved in how cells produce energy or respond to stress. These shifts may contribute to age-related changes in breast cancer risk.
4. Differences Tied to Ancestry: One group of cells that respond to hormones showed unique activity in women with Indigenous American ancestry. This wasn’t seen in other groups and could point to ancestry-related differences in how breast cells respond to hormones.
5. Differences in Support Cells: Fibroblasts, which are support cells that help structure breast tissue, also showed ancestry-related variation. For example, women of African ancestry had a higher presence of a fibroblast that was linked to the formation of new blood.

Why is this study important?

Understanding these baseline differences in healthy tissue could help scientists develop better, more personalized tools to predict, prevent, and treat breast cancer. It also highlights the importance of including diverse populations in research, so discoveries reflect everyone—not just those who have traditionally been studied. Importantly, the study found ancestry-linked differences in a type of support cell known as a fibroblast. These cells, which help shape the breast tissue environment, showed a unique state in women of African ancestry that may play a role in tissue development or repair. This points to a possible biological contributor to racial disparities in breast cancer outcomes—an area that warrants further research.

Full citation

Bhat-Nakshatri P,Marino N,Gao H,Liu Y,Storniolo AM,Nakshatri H Acquisition, processing, and single-cell analysis of normal human breast tissues from a biobank.. STAR protocols 2022 Mar; 3 (1). PMID:34977686.