Maybe a lot. Exciting new research shows how the microbiome of tiny organisms colonizing your digestive tract can help (or harm) your health in many ways — even in the field of skin cancer.
It may be hard to digest this fact, but there are trillions of teeny, tiny living things, called microbes or microorganisms, that have made your body their home. No need to run to the shower or try a detox cleanse, though. You need these organisms as much as they need you. And yes, there is a connection to your skin health and skin cancer.
Each community of microbes is called a microbiome, and there are microbiomes all around your body: on your skin, in your mouth, in your stomach and in your colon, for example. Bacteria are the majority “landowners” in each microbiome, but there are also viruses, fungi and archaea (an ancient group of single-celled organisms) living side-by-side. These microbes move in as soon as you are born, though their communities evolve and mature over the first few years of your life as different species move in and out. By the time you are about 5 years old, your microbiomes are well-established, relatively stable, fully functioning societies.
For the most part, these communities are made of “good” microbes that remain in a balance known as homeostasis. But if they fall off-balance from, say, an outside infection, smoking or taking an antibiotic medication (which kills off some good bacteria along with the bad), it turns out that their host (that’s you!) does too. In other words, they can have a huge effect on your health.
“The largest concentration of microbes is in your colon, in the lower gut,” says Alena Pribyl, PhD, senior scientist and research officer at Microba, an Australia-based company that is doing groundbreaking research into the microbiome and how it can affect health. Over the past 20 years, an astounding amount of research has linked the gut microbiome to nearly every angle of human health. “It can be described as almost another organ that we’ve recently discovered,” Dr. Pribyl explains. “It influences all of our different bodily systems.”
At first, researchers focused on how the relative abundance of species in the gut microbiomes of people who had a certain disease differed from those who didn’t have the disease. Sometimes, species seemed to be missing, while others were present at much higher levels. Different compositions of species in the gut turned out to be associated with diseases like inflammatory bowel disease (IBD), type 2 diabetes, atopic dermatitis (eczema) and depression.
Then, scientists found a connection between the microbiome and whether someone will respond to certain treatments, including the immunotherapies used to treat melanoma. Since 2015, multiple studies have shown that the gut microbiome of first mice and then human patients who respond to immune checkpoint inhibitors (a type of immunotherapy) differs from the gut microbiome of those who don’t respond.
The Skin Cancer Foundation reported on this in 2019 in The Melanoma Letter, when Jennifer A. Wargo, MD, and colleagues at The University of Texas MD Anderson Cancer Center wrote that the gut microbiome may affect patients’ response to melanoma treatment. [Note that since then, immunotherapies have also been approved to treat some advanced basal cell carcinomas, or BCCs, and squamous cell carcinomas, or SCCs]. “This has important implications,” she stated then, “as numerous factors impact the gut microbiome, and strategies are being developed to modify it for therapeutic purposes.”
One of those impacting factors is the use of antibiotic medication. While antibiotics are useful for treating bacterial infections, they can also wipe out good species of “gut bugs,” as Dr. Pribyl affectionately calls them. “Studies have shown that patients who have been given antibiotics respond more poorly to immune checkpoint inhibitors,” she says. The next step in this research is to work out which gut microorganisms are important for response and how to make certain they are present when a patient starts immunotherapy.