An oral bacterium commonly associated with periodontal disease can promote breast cancer initiation, tumor growth and spread by inducing DNA damage and altering cancer cell behavior, according to a study led by researchers at the Johns Hopkins Kimmel Cancer Center and its Bloomberg~Kimmel Institute for Cancer Immunotherapy.

Published in Cell Communication and Signaling, the study shows that Fusobacterium nucleatum, an oral microbe previously linked to colorectal and other cancers, can travel through the bloodstream and colonize in breast tissue, where it causes inflammation and other precancerous changes. The researchers found that the bacterium accelerated tumor growth and increased the spread of cancer cells from the breast to the lung in animal models of human breast cancer.

“The key takeaway is that this oral microbe can reside in breast tissue and that there is a connection between this pathogen and breast cancer,” says study leader Dipali Sharma, professor of oncology, who notes that the team’s study was inspired by many small studies that looked at thousands of patients and connected periodontal disease to breast cancer.

The researchers also found that epithelial cells (the cells that line the breast ducts) and breast cancer cells with BRCA1 mutations were particularly vulnerable.