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The incidence of breast cancer is on a rise, and this disease is nothing short of an epidemic for women. Considered one of the most frequently diagnosed and life-threatening cancers, a variety of risk factors can affect your likelihood of getting this disease.
Considering the seriousness of the illness, various studies are being done across the globe to know the risks and preventive measures for breast cancer better. And surprisingly, researchers have found that a microbe found in the colon, which is commonly associated with the development of colitis and colon cancer, can play a role in the development of some breast cancers.
The research, which was led by investigators with the Johns Hopkins Kimmel Cancer Center and its Bloomberg~Kimmel Institute for Cancer Immunotherapy, is published in the journal Cancer Discovery.
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.
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, says senior study author Dipali Sharma, PhD, a professor of oncology at Johns Hopkins Medicine.
“The study is the first step to show the involvement of ETBF in breast cancer development,” Sharma says. However, 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 have cancer-causing activity for breast tissue.
Also, read: Today we’re debunking 8 common myths about breast cancer
The fact that many women are still getting breast cancer without exhibiting any of the known risk factors is a major concern. This study opened another dimension to look into as a probable cause of breast cancer in women.
“Despite multiple established risk factors for breast cancer, such as age, genetic changes, radiation therapy and family history, a large number of breast cancers arise in women harbouring none of these, indicating the need to look beyond,” Sharma says.
“Our study suggests another risk factor, which is the microbiome. If your microbiome is perturbed, or if you harbour toxigenic microbes with oncogenic function, that could be considered an additional risk factor for breast cancer.”
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PERSONALISE NOWThe researchers studied the role of ETBF. First, they performed a meta-analysis of clinical data looking at published studies comparing microbial composition among benign and malignant breast tumours and nipple aspirate fluids of breast cancer survivors and healthy volunteers. B. Fragilis was consistently detected in all breast tissue samples as well as the nipple fluids of cancer survivors.
In the lab, the team gave the ETBF bacteria by mouth to a group of mice. First, it colonized the gut. Then, within three weeks, the mouse mammary tissue had observable changes usually present in ductal hyperplasia, a precancerous condition.
In additional tests, investigators found that hyperplasia-like symptoms also appeared within two to three weeks of injecting ETBF bacteria directly to the teats of mice and that cells exposed to the toxin always exhibited more rapid tumour progression and developed more aggressive tumours than cells not exposed to the toxin.
Breast cells exposed to the toxin for 72 hours retained a memory of the toxin and were able to start cancer development and form metastatic lesions in different mouse models. Investigators also found the Notch1 and beta-catenin cell signalling pathways to be involved in promoting EBFT’s role in breast tissue.
“We definitely should try to maintain a healthy microbiome, including eating a healthy diet and exercising, and maintaining the correct body mass index,” Sharma advices.
Moreover, down the road, screening for microbiome changes could be as simple as stool sample tests, said lead author Sheetal Parida, a postdoctoral fellow at Johns Hopkins Medicine.
“If we find additional bacteria responsible for cancer development, we can easily look at the stool and check for those. Women at high risk of developing breast cancer might have a high population of some of these,” concludes Parida.
