How Aging Shapes Breast Cancer—and Why It Matters

In a new study to be published in Proceedings of the National Academy of Sciences (PNAS), investigators Drs. Kornelia Polyak and Sandra McAllister reveal how aging changes the way breast cancer develops and evades the immune system. Using an advanced animal model that closely mirrors human disease, the team found that tumors arising in older individuals originate from a distinct population of normal mammary epithelial cells and carry more DNA damage. These age-related tumors were also far less visible to the immune system helping explain why breast cancers in older patients are often more aggressive and harder to treat.Importantly, the researchers discovered that this immune “blind spot” is driven in part by the loss of key genes involved in antigen presentation—the molecular signals that alert the immune system to danger. Analyses of human breast cancer data showed that the same genetic losses are linked to weaker immune responses and worse patient outcomes. These findings highlight why a patient's age should be a key consideration in designing cancer therapies, especially immunotherapies. This work advances more personalized, age-aware approaches to cancer treatment—ensuring scientific progress benefits patients across the lifespan.