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Breast Microbiome Profiles Linked to Higher—or Lower—Chance of Cancer

ByTim De ChantNOVA NextNOVA Next

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Microbiologists have found an intriguing link between the type of bacteria that live inside a woman’s breast and her risk of breast cancer.

The connection is simply correlation at this point—researchers don’t have enough information to know whether the bacteria play a role in causing breast cancer (or not) or if their numbers change in response to the presence (or absence) of cancer. But if the former hypothesis is proven correct, it could offer a potential preventative treatment for women at risk for the disease.

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breast-cancer-mammogram
A mammogram of a breast with a circumscribed mass.

The team, led by Gregor Reid, a professor of microbiology and immunology at Western University in Ontario, Canada, sequenced the DNA samples taken from women both with and without breast cancer. Here’s Knvul Sheikh, reporting for Scientific American:

They analyzed bacterial DNA found in breast tissue samples from 58 women who were undergoing lumpectomies or mastectomies for either benign or cancerous tumors, as well as from 23 healthy women who had undergone breast reductions or enhancements. They found that women with breast cancer had higher levels of some types of bacteria, including Enterobacteriaceae, Staphylococcus and Bacillus. Women without cancer had higher levels of other types, such as Lactococcus and Streptococcus.

Reid and his team also performed preliminary tests to see whether the bacteria types associated with breast cancer might play a role in promoting cancerous qualities in cells. Indeed, bacteria in the Enterobacteriaceae family and Staphylococcus genus damaged DNA in lab tests by breaking both strands, a type of break that is frequently error prone and can lead to cancer. (That test, while suggestive, is preliminary—they’d need to conduct further tests in animal or human models before saying anything with more certainty.)

For women without cancer, the bacteria found in their breasts may be playing a protective role. Those strains are associated with anticancer properties: Other studies have shown that Lactococcus, in particular, can increase the activity of natural killer cells, a type of immune cell that helps control tumor growth, while Streptococcus can have antioxidant properties that could prevent DNA damage.

The paper cites yet another study that suggest probiotics could help coax the immune system into cleaning up potentially cancerous cells, though the effect was only tested in animal models. Still, it tentatively points toward a potential preventative treatment.

Research into the breast microbiome is clearly in its early stages, but these results give scientists some promising leads to follow.