First Ever Characterization of the Breast Cancer Microbiome

Cleveland Clinic researchers discovered for the first time that healthy breast tissue contains more of the bacterial species Methylobacterium than the tissues of women with breast cancer.

Researchers have long suspected that a breast cancer "microbiome" exists, but it has not yet been characterized. This research team, which is made up of both basic researchers and physicians, has taken the first step toward understanding the composition of the bacterial community in breast cancer.

Published in Oncotarget, the study examined the tissues of 78 patients who underwent mastectomy for invasive carcinoma or elective cosmetic breast surgery. In addition, they examined oral wash and urine to determine the bacterial composition of these distant sites. This is the first study to investigate both breast tissue and distant sites for bacterial dysbiosis in breast cancer.

While additional studies are needed, these findings are a good first step towards one day identifying a biomarker that can help physicians quickly and easily diagnose breast cancer. Harnessing the power of microbiomics before breast cancer forms may allow physicians the chance to prevent the disease—which will affect 1 in 8 U.S. women in their lifetime—with prescription of probiotics or antibiotics.

In addition to the Methylobacterium finding, the team discovered that cancer patients' urine samples had increased levels of gram-positive bacteria, including Staphylococcus and Actinomyces. Identifying and targeting specific pro-cancer bacteria may help make the environment less hospitable to cancer, which could have positive implications for both treatment and prevention. Further studies are needed, however, to better understand the role these organisms play in breast cancer.

Charis Eng, MD, PhD, founding chair of the Genomic Medicine Institute and director of the Center for Personalized Genetic Healthcare, and Stephen Grobymer, MD, section head of Surgical Oncology, Director of Breast Services, are co-senior authors of the study.

This work provides proof-of-principle evidence to study creation and utilization of loaded nanoparticles targeting these pro-cancer bacteria. Funded by a grant from the Center of Transformational Medicine, Drs. Eng and Grobymer are collaborating with investigators at Hebrew University to do just that.

Dr. Eng holds the Sondra J. and Stephen R. Hardis Endowed Chair of Cancer Genomic Medicine at Cleveland Clinic.