Breast cancer often grows in tissue that is unusually dense. That’s why clinicians flag women with this kind of breast tissue for follow-up after a mammogram.
A UC San Francisco study has uncovered a mechanism that could help explain how this dense environment promotes breast cancer. Dense tissue, which is stiffer than normal tissue, attracts immune cells to the breast and prompts them to release chemicals that mutate DNA. The chemicals penetrate nearby breast cells and damage their DNA, raising the risk of cancer.
“For decades, we’ve used this relationship between breast tissue density and cancer risk to more readily find cancer,” said Valerie M. Weaver, PhD, director of the UCSF Center for Bioengineering and Tissue Regeneration and senior author of the paper, which appeared in Cancer Cell in June. “Our research could enable us to prevent this cancerous domino effect from occurring.”
Dense tissue attracts macrophages
Weaver’s team, led by UCSF postdoctoral scholar Mary Kate Hayward, PhD, began by analyzing publicly available genomic data from breast tumors. They found that the patients with worse outcomes had more breast tissue fibrosis, or scarring, and more of a type of immune cell known as a macrophage, which is often involved in cancer, and more DNA mutations.