The human body contains billions of microorganisms, and microbial cells found in the human gut are estimated to outnumber human cells by ten-to-one in healthy adults. However, little is known about the ways in which these minute life forms influence health and disease.
That is why gastroenterologists at Rush University Medical Center are working on a new research study funded by the U.S. Department of Defense to chart the presence of microorganisms found within the gut and to explore how microbial imbalances may impact diseases like breast cancer.
"Similar to what has been done with human DNA, we want to map out the composition of these microorganisms from their DNA and analyze how they correlate to diseases and changes within the immune system," said Dr. Ece Mutlu, gastroenterologist at Rush and principal investigator of the study. "If we are able to find the microbes responsible for particular diseases, it may increase the likelihood of developing new diagnostic tests and treatments for diseases like breast cancer."
Unlike the over 20,000 genes found in the human genome, the bacterial genomes, known as the microbiome, can rapidly evolve under the pressure of changing environmental factors. Therefore, changes in the gastrointestinal microbiota have the potential to explain rises in breast cancer incidence, which are difficult to attribute to alterations in the human genome alone.
About 20 to 25 percent of the risk of developing breast cancer is related to family history. Unfortunately, the known breast cancer susceptibility genes such as BRCA2 and BRCA 2 explain less than 5-10 percent of the total breast cancer cases attributable to familial factors.
Researchers are exploring the possibility that the gut microbiome passed on from mother to child may be another familial factor previously never accounted for in the genetic risk models.
"The currently recognized environmental risk factors are estimated to account for only 40 percent of the variance in breast cancer incidence, "said Mutlu. "There is a large body of evidence implicating that dietary factors such as alcohol, high fat foods are also possible breast cancer risk enhancers, and fruits and vegetables are protective."
Therefore, the gastrointestinal microbiota also has been an overlooked as a potential, major risk factor for breast cancer compared to better known genetic and environmental risk factors.