Probiotics help prevent mammary cancer in mice

Happy Halloween!

Editors note:  We know we wrapped up the breast cancer awareness last week, but then we found this fascinating paper and just had to write about it.  Plus, it is the last day of Breast Cancer Awareness Month, so this post is officially wrapping it up.  And oh yeah, Happy Halloween!  We hope all our trick-or-treating readers receive plenty of fermented foods tonight.

An article published in the International Journal of Cancer explores the effects of probiotic consumption on mice with a predisposition to mammary cancer.  The article also attempts to establish a link between the probiotic and its influence on the immune system.

First, researchers fed mice a high fat diet, similar to a fast food diet.  Compared to controls, these mice had a higher incidence of mammary cancer.  They then repeated these trials but gave some of these fast food mice Lactobacillus reuteri.  Those mice that received the probiotic had a significantly lower rate of mammary cancer symptoms than those that didn’t.  The researchers then conducted a study to see if L. reuteri could help protect from cancer when the factor of obesity was removed.  In this experiment they genetically predisposed some mice to get mammary cancer, and fed these mice the probiotic.  They found that consumption of L. reuteri delayed or completely prevented the development of tumors, when compared to untreated mice.  The researchers go on to suggest that L. reuteri may be increasing the production of a specific type of immune cell, the CD25 T-cell, and this immune cell may be exerting the underlying anticancer effects they are observing.  They tested this hypothesis by transplanting CD25 T-cells into cancerous mice, and blocking CD25 T-cells in mice that were predisposed to cancer, though given the probiotic.  In the mice injected with CD-25 T-cells, their cancer rate decreased.  In the mice where CD25 T-cells were blocked, their cancer rates were the same as mice without the probiotic.

Probiotic bacteria decreased already developed tumors, and, in some cases, prevented tumor growth in animals predisposed to cancer by directly influencing the immune system.  These results reinforce the idea that probiotics are important for a healthy immune system, which is important for overall health.  So keep eating that yogurt, kimchi, and kombucha!

Reflecting on the microbiome during National Breast Cancer Awareness Month

As you watched the future Hall of Fame quarterback Eli Manning over the past two weeks, you probably noticed NFL players wearing pink for National Breast Cancer Awareness Month. Before this month comes to a close we want to bring your attention to one of our previous posts about the microbiome and breast cancer.  The study showed that post-menopausal women who had a more diverse gut microbiome had a lower risk of getting breast cancer. You can read more about it here.  

We also want to take this time to encourage natural breast feeding, whenever possible, for all new mothers.  A new review article published in Nature Pediatric Research describes the importance of breast milk in creating a healthy infant microbiome.  Breast milk is a complex food that contains bacteria and also supports the growth of bacteria.  The review highlights that when compared to formula, breast feeding leads to more infant gut colonization of Bifidobacterium, Lactobacillus, and Clostridia, and these bacterial strains are linked to the development of a healthy gut and a healthy immune system.  In addition, breast milk leads to a lower infant gut pH, compared to formula, and infant gut pH affects further species colonization.  Breast milk has evolved to support both us and our microbiomes, and no simple formula can substitute for the real thing.  

Every week there are new studies connecting the microbiome to public health and disease areas that may not seem as obvious as others. We know that the microbiome influences diseases and conditions like obesity, inflammatory bowel disease (IBD), diabetes, and necrotizing enterocolitis (NEC), but we are now learning that the microbiome is also connected to diseases and conditions like breast cancer, alcoholism, autism, and depression. While it is important to keep our excitement about the microbiome in check, the AMI is building new resources for the microbiome field because we believe our impact can be vast.  Advancing the field of research as a whole can influence the development of new treatments and therapies for a wide range of diseases. 

Microbiome and breast cancer

A recent study out of the University of Maryland suggests that post-menopausal women with a more diverse microbiome have a lower risk of getting breast cancer.  The study investigated the fecal microbiomes of 60 healthy women between the ages of 55 and 69 while also testing the estrogen and estrogen metabolites from their urine.  The results showed a correlation between increased urinary metabolites with increased gut microbiome diversity, independent of other variables.

This is important because estrogen that circulates through the body, that isn't broken down and removed by the body, is correlated with an increased risk for breast cancer.  Therefore, decreasing the amount of circulating estrogen, and increasing the rate at which estrogen is removed from the body may result in a lower risk of breast cancer for post-menopausal women.

It is known that as estrogen and its byproducts are naturally processed, they are circulated in and around the gut, which has led scientists to speculate that the gut microbiome may be important to estrogen cycling and removal in the body.  The authors of this paper help support this hypothesis by showing that microbiome diversity effects estrogen removal.

This paper opens the door to some very interesting questions.  Can microbiome diversity be used as a diagnostic for breast cancer risk?  Can the gut microbiome be adjusted to decrease breast cancer risk?  A nice summary of the findings with quotes from the authors was also published by Science Daily.