Research on Oral Microbiome and Head and Neck Squamous Cell Cancer

Understanding the Human Microbiome

The human body is home to trillions of microbes, including bacteria, fungi, and viruses, which outnumber human cells by approximately ten to one. While these microbes are predominantly located in the gut, especially the large intestine, they also inhabit the mouth. Collectively, the genetic material of these microbes is referred to as the “microbiome,” which varies from person to person. Emerging research indicates that microbiome patterns play a critical role in health, particularly concerning immunity and nutrition. A significant amount of research has focused on the correlation between microbiome patterns and specific cancer risks.

Link Between Oral Microbiome and Head and Neck Squamous Cell Cancer

Each year, over half a million new cases of head and neck cancers, including mouth and throat cancers, are reported globally. Approximately 85% of these cancers are squamous cell cancers, originating from the lining cells of the mouth and throat. Researchers in the United States conducted a comprehensive study to explore the relationship between oral microbiome patterns and the risk of head and neck squamous cell cancer, with their findings recently published in JAMA Oncology.

Study Overview

The study involved 129 cases of head and neck squamous cell cancer identified during two significant cancer screening initiatives: the American Cancer Society Cancer Prevention Study (CPS-II) and the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial (PLCO). Additionally, 254 matched control subjects from these screening studies were included, all of whom were cancer-free at the outset.

The CPS-II study encompassed 184,000 participants aged 50-74, who completed a diet and lifestyle questionnaire in 1992. Follow-up questionnaires were sent every two years to gather updated information and track any new cancer occurrences. Oral wash samples were collected from 70,000 participants in 2001-2002. The PLCO study recruited participants aged 55-74 between 1993 and 2001, focusing on the impact of screening on cancer-related mortality. Participants were randomly assigned to either a screening or control group, with oral wash samples taken from 52,000 individuals in the control group. Annual questionnaires were also utilized to monitor cancer incidence.

Findings from the Oral Microbiome Analysis

The researchers analyzed the stored oral wash samples from the 129 head and neck squamous cell cancer cases and the 254 control subjects to assess their oral microbiome patterns. The study revealed that individuals with head and neck cancer were more likely to be smokers and had higher alcohol consumption compared to the control group. Notably, the overall microbiome pattern did not correlate with the risk of head and neck squamous cell cancer. However, an increased presence of two specific bacteria—Corynebacterium and Kingella—was linked to a reduced risk of developing this type of cancer. This association was particularly significant among individuals with a history of smoking.

Corynebacterium and Kingella are recognized for their ability to break down carcinogens present in cigarette smoke, potentially explaining their protective effects against cancer.

Implications for Oral Health and Cancer Prevention

Maintaining a healthy oral microbiome is essential for overall oral health. The discovery that higher levels of Corynebacterium and Kingella are associated with a decreased risk of head and neck squamous cell cancer may have future implications for prevention strategies, complementing established measures such as quitting smoking and reducing alcohol intake.

Conclusion

Research indicates that understanding the oral microbiome’s role could be pivotal in cancer prevention efforts. Ongoing studies may further elucidate the relationship between specific microbes and cancer risks, ultimately contributing to more effective prevention strategies.

Reference

Hayes R, Ahn J, Fan X, et al. Association of oral microbiome with risk for incident head and neck squamous cell cancer. JAMA Oncology Jan 11, 2018. DOI: 10.1001/jamaoncol.2017.4777.