A new study has identified more than a dozen bacterial species in the mouth that are linked to a 50% increased risk of developing head and neck squamous cell carcinoma (HNSCC). Some of these bacteria were already known to contribute to periodontal disease, a severe gum infection that can lead to jawbone damage and tissue loss.
While experts have long noted that individuals with poor oral health are at higher risk of developing HNSCC, which includes common cancers of the mouth and throat, the exact bacteria responsible had remained unclear. Earlier research had connected certain oral bacteria to these cancers, but definitive links to specific bacterial types were not established until now.
The research, led by scientists from NYU Langone Health and the Perlmutter Cancer Center, analyzed the genetic makeup of oral bacteria from healthy men and women. Of the hundreds of bacterial species typically found in the mouth, 13 were identified as either increasing or decreasing the risk of HNSCC, contributing to an overall 30% greater likelihood of developing the disease. When combined with five species commonly associated with gum disease, the risk rose to 50%.
“Our findings provide new insight into the connection between the oral microbiome and head and neck cancers,” said Soyoung Kwak, PhD, the study’s lead author and a postdoctoral fellow at NYU Grossman School of Medicine. Kwak noted that these bacteria could be used as biomarkers to help identify individuals at higher risk.
Published in JAMA Oncology on September 26, this study is the largest and most detailed analysis of its kind. It is also one of the first to investigate the potential role of fungi in the development of HNSCC, although the research found no significant involvement of fungal organisms.
The researchers drew data from three extensive studies that tracked 159,840 Americans: the American Cancer Society Cancer Prevention Study II, the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, and the Southern Community Cohort Study. Participants provided saliva samples shortly after enrollment, which were used to analyze their oral microbiomes. The study followed participants for 10 to 15 years, recording any development of tumors.
DNA from the saliva of 236 participants who developed HNSCC was compared to that of 458 individuals who remained cancer-free. The researchers adjusted their analysis for factors such as age, race, smoking, and alcohol consumption.
Dr. Richard Hayes, DDS, MPH, PhD, co-senior author of the study, emphasized the importance of maintaining good oral hygiene. “Brushing your teeth and flossing may not only help prevent periodontal disease, but also protect against head and neck cancer,” said Hayes, a professor at NYU Grossman School of Medicine and a member of the Perlmutter Cancer Center.
The study’s findings establish a correlation between oral bacteria and cancer risk, but further research is needed to determine a direct cause-and-effect relationship. “Our next steps will be to explore the mechanisms behind how these bacteria contribute to cancer and how we can intervene,” said Dr. Jiyoung Ahn, co-senior author and associate director for population research at the Perlmutter Cancer Center.
Despite the increased risks, Ahn noted that head and neck cancers remain relatively rare overall.
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