BALTIMORE, June 30 (UPI) -- Differences in the microbiome between cancer patients and healthy people may lead to diagnostic tests for some forms of the disease based on saliva samples, a new study suggests.
Researchers at Johns Hopkins University report they found the bacteria that naturally colonizes the body was different when comparing saliva samples from healthy people and people with head or neck cancer.
Changes to the microbiome have been linked in previous studies to arthritis, multiple sclerosis, irritable bowel syndrome and other forms of cancer, though scientists do not fully understand how the body, treatment and other environmental factors influence bodily bacteria, or vice versa.
The goal of the study was to further research into how the microbiome may influence the immune response to cancer, as well as how the immune response affects the microbiome. Researchers say their study suggests a saliva test could be possible in the future.
"We see some specific bacterial populations that are increased or lost in the presence of cancer when compared to healthy controls," says Guerrero-Preston. This may mean that either the tumor is affecting the environment in the mouth by killing bacteria that would fight cancer or that the patients may be predisposed to cancer because they originally lacked bacteria that prevent tumor development.
For the study, published in the journal Oncotarget, researchers took bacterial DNA samples from the saliva of 42 cancer patients -- 17 with head and neck squamous cell carcinoma, seven who were positive for HPV and 10 without HPV -- comparing them to 25 samples from people without cancer.
For patients with tumors, researchers found increased levels of streptococcus, dialister and veillonella genera and lower levels of neisseria, aggregatibacter, haemophilus and leptotrichia genera when compared to people without cancer. The researchers also linked differences in bacterial DNA between cancer patients who did and did not have HPV.
While the researchers say the study does not show any type of cause-and-effect link, future research needs to look at the detection of bacterial DNA and effects of the actual bacteria, as well as how they affect the oral environment.
"One of the goals of our research is to better understand how the microbiome may influence the immune response to cancer and how the immune response affects the microbiome in turn," Dr. Rafael Guerrero-Preston, an assistant professor of otolaryngology–head and neck surgery at the Johns Hopkins University School of Medicine, said in a press release. "Our findings suggest that we may one day use the composition of the microbiome to test for disease."