Breast cancer is a major health concern across the world. It is the leading cause of morbidity and mortality among women.
According to the Centers for Disease Prevention and Control (CDC), there are various types of breast cancer, which depends on which cells in the breast turn into cancer and there are many causes that can lead to breast cancer in women.
A new study published in the journal of Cancer Discovery suggests that a microbe found in the colon and commonly associated with the development of colitis and colon cancer may also play a role in the development of some type of breast cancers.
According to the study, breast tissue cells exposed to this toxin retain a long-term memory, increasing the risk for disease. In a series of laboratory experiments, researchers discovered that when enterotoxigenic Bacteroides fragilis (ETBF) was introduced to the guts or breast ducts of mice, it always induced growth and metastatic progression of tumour cells.
Senior author Dipali Sharma, Professor of oncology at Johns Hopkins Medicine in the US said, “While microbes are known to be present in body sites such as the gastrointestinal tract, nasal passages and skin, breast tissue was considered sterile until recently.”
Additional studies are needed to clarify how ETBF moves throughout the body, whether ETBF can be a sole driver to directly trigger the transformation of breast cells in humans, and/or if other microbiota also has cancer-causing activity for breast tissue, according to the team.
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“Despite multiple established risk factors for breast cancer, such as age, genetic changes, radiation therapy and family history, many breast cancers arise in women harbouring none of these, indicating the need to look beyond,” Sharma said.
“Our study suggests another risk factor, which is the microbiome. If your microbiome is perturbed, or if you harbour toxigenic microbes with the oncogenic function that could be considered an additional risk factor for breast cancer,” she added.
Several experiments were performed by the team to study the role of ETBF. Initially, they executed a meta -analysis of clinical data looking at the studies published comparing microbial composition among benign and malignant breast tumours and nipple aspirate fluids of breast cancer survivors and healthy volunteers.
In all breast tissue samples B. fragilis was consistently detected as well as the nipple fluids of cancer survivors.
In the lab, the team gave the ETBF bacteria by mouth to a cluster of mice. First, it occupied the gut and then, in three weeks, the mouse mammary tissue had observable changes usually present in ductal hyperplasia, a precancerous condition.