Understanding the Role of Bacteria in Breast Cancer: A Study by Prof Ian Bennett

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Breast cancer is perhaps the most extensively studied human cancer of all. Genome and transcript sequence from several thousand patients are now publically available. Despite the progress made in curing breast cancer, we still do not know what causes it.

Professor Ian Bennett  has been investigating changes in bacterial communities in breast tissue and the development of the changes of these communities in patients with breast cancer. This two-year project has just concluded and is showing promising insight that could lead to the prevention of breast cancer through targeting of healthy bacteria.

Whilst there have been recent reports suggesting that viruses might be implicated in breast cancer development, in an earlier study Professor Bennett’s group demonstrated using genome deep sequencing techniques that viral genomes were not actually incorporated into the tumour genome, thus essentially showing that is was unlikely that viruses were playing a significant role in breast cancer aetiology. This work was published in Scientific Reports. 

More recently, it has emerged that bacteria may be implicated in the causation of human cancers and through a mechanism which involves changing the environment surrounding tissue cells.

Bacterial communities are found in almost all human tissue and are generally considered to be required for good health. However, changes in the composition of bacterial communities are known to cause disease such as inflammatory bowel disease, even diabetes. Whilst Prof.Bennett’s preliminary data indicated that more than 70% of normal breast tissue contained a bacterial community, breast cancer tissue had low levels of bacteria.

Further research using PCR and gene sequencing techniques compared normal breast tissue with cancerous tissue from the same breast of patients.

Using this approach, they consistently found that normal breast tissue had a population of bacteria. However, significantly, it was discovered that the cancer tissue itself had almost undetectable levels of bacteria.

This suggests that the normal healthy breast tissue has a small healthy bacterial community, whereas breast cancer tissue has little if any. It may be that we need bacteria to maintain breast health and that loss of these “healthy” bacteria may contribute to the formation of breast cancer.
“Because our study shows that breast cancer tissue has a greatly reduced bacterial burden, this might suggest that the loss of ‘good bacteria’ may alter the breast tissue biochemical milieu and potentially incite inflammatory changes which predispose to breast cancer development. If we can show that this is the case, then it suggests that tests of bacterial burden may be helpful in diagnosing those at risk of breast cancer. More importantly, it may suggest that treatments or diets that maintain ‘good bacterial’ communities within breast tissue may prevent breast cancer development,” said Professor Ian Bennett.

These findings will be pursued in a future study to understand what preventative mechanisms could be introduced to maintain the healthy bacterial composition of breast parenchyma.

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