Researchers from BC Cancer and the University of British Columbia (UBC) have discovered that certain bacteria found in breast tumours could be linked to metastasis, or the spread of cancer to other parts of the body. The findings, published in mBio, a journal of the American Society of Microbiology, suggest that Bacillus bacteria in the tumour micro-environment can play an active role in metastasis.
“The role of bacteria in cancer is something that is undergoing a rapid increase as a field of study,” says Dr. Zachary Gerbec, the study’s first author and former co-post-doctoral fellow in the laboratories of Dr. Shoukat Dedhar, distinguished scientist at BC Cancer, and Dr. Brett Finlay, professor at Michael Smith Laboratories, UBC. “We wanted to explore this further by examining specific bacteria from breast tumours to understand how bacteria and tumours interact.”
The study emphasizes the role of the tumour microbiome in cancer progression, which includes the bacteria, fungi and viruses that live in and around the tumour. While researchers have previously found bacteria to influence cancer growth, it is not well understood how bacteria within the tumour microenvironment impact metastasis, which is a major cause of cancer-related deaths.
The Dedhar and Finlay research teams discovered that a type of bacteria called Bacillus thermoamylovorans, found only in metastatic tumours, made tumour cells spread more aggressively and altered their metabolism.
“We were able to work with Dr. Finlay’s lab to isolate differential bacteria from metastatic and non-metastatic breast tumours – a difficult task,” recalls Dr. Dedhar. “Through this method, we found that this bacteria exists outside of the tumour cell, and can alter the metabolism of tumour cells to promote their survival.”
Interestingly, further genetic analysis showed that the bacteria from metastatic tumours carried specific genes linked to the spread of cancer. These findings were confirmed by testing patient tumour samples, in collaboration with Dr. Samuel Aparicio’s laboratory at BC Cancer, for the presence of similar bacterial genes, which were found to be more common in breast tumours of patients with higher mortality.
The study highlights the importance of further research to understand how certain bacteria may increase cancer's ability to spread and could lead to new ways to slow, or stop, metastatic cancer.
“A lot of what we did was exploratory, and we’re hoping that our study can serve as a jumping off point for future research,” adds Dr. Gerbec, noting that this work has the potential to open other avenues for exploration.
Dr. Dedhar concludes that the next step in this research is to identify the specific mechanism that allows this bacteria to promote metastasis.