Sfanos: Infection may cause chronic inflammation in the prostate, which could lead to cancer.
The urinary tract is not sterile. In fact, it’s full of bacteria, and some of them are linked to the development of chronic inflammation in the prostate.
You’re full of bacteria cells: trillions of them make up your microbiome – distinct ecosystems in and on your body. Some of these bacteria are bad, and cause infections and disease. Other bacteria are good, and help keep us healthy. Until recently, clinicians and scientists believed that one area of the body was bacteria-free: the urinary tract, which they thought was sterile. It turns out, they were wrong. This discovery opens the door to new research into what may cause prostate cancer in some men, and may lead to new ways to prevent it.
Our microbiome changes all the time, depending on such environmental factors as what we eat – for example, the kind of gut bacteria that are supported by a diet of cheeseburgers, chips and sodas are not the same bacteria that thrive when you eat lean meat, fruits and vegetables. Indeed, says Brady scientist Karen Sfanos, Ph.D., “alterations to the heathy microbiome can lead to overgrowth of harmful, pathogenic types of bacteria.” This change is called dysbiosis, and it can lead to the development of chronic inflammation – which, in turn, “is linked to the development of many types of disease, including cancer.”Even prostate cancer? Maybe so. Thanks to more sophisticated testing methods, scientists can see what they couldn’t see before: bacteria in the urine and urinary tract. “We now know,” says Sfanos, “that there’s a urinary microbiome with its own distinct bacteria” – different from, say, the bacteria that live on your skin or in your gut.
Sfanos and other Brady investigators including pathologist Angelo De Marzo, M.D., Ph.D., have been studying the possibility that chronic inflammation in the prostate sets the stage for the development of prostate cancer. What causes the inflammation? Maybe infection. What causes the infection? Bacteria. “The recent discovery of a urinary microbiome, coupled with the fact that the urinary tract runs through the prostate,” which means that bacteria in the urinary tract might find their way into prostate tissue, “led us to hypothesize that prostate infections that may lead to prostate cancer development may be caused by dysbiosis in the normal urinary microbiome.”
To test this idea, Sfanos and her lab have sequenced the genes of bacteria present in urine samples from a large collection developed by Alan Partin, M.D., Ph.D, the Jakurski Family Director of Urology. “We have profiled the bacterial communities in the urinary microbiome from 129 men” with or without prostate cancer. This is uncharted territory, and among their discoveries is that “the urinary microbiome in men is very different from that which has been previously reported in women.” For example, “we found that the urinary microbiome in men is often enriched with a type of bacteria called Actinobacteria. This is of particular interest because certain types of Actinobacteria have been linked to the development of chronic inflammation in the prostate.”
The team also found low levels of certain bacteria known to cause sexually transmitted infections (STIs) in these men. “This was surprising because the men in these studies did not have symptoms of STIs – indicating that men may carry low levels of these organisms in their urinary tract without knowing it,” says Sfanos.
Ultimately, Sfanos and her team hope to figure out which types of bacteria raise a man’s risk of developing prostate cancer. It may be that “men can be tested for this high-risk urinary microbiome, and then could be treated with specific antibiotics as a way of preventing prostate cancer from developing.” This study was recently published in the Journal of Urology. Other Hopkins investigators who contributed to the study include Eva Shrestha, Ibrahim Kulac, Onur Ertunc, Srinivasan Yegnasubramanian, and Leslie Mangold.