Oral squamous cell cancer (OSCC) is a deadly disease that starts in the cells lining the mouth. It is often diagnosed late, making it hard to treat. Each year, around 450,000 people die from OSCC, according to the International Agency for Research on Cancer.
Scientists have long suspected that changes in bacteria in the mouth (the oral microbiome) might play a role in the disease, but different studies have reported conflicting results.
A new study, published in mSystems, helps to clear up this confusion. Researchers combined data from 11 earlier studies to identify consistent patterns in the bacteria found in saliva from people with OSCC.
This large-scale analysis confirmed that certain bacteria are more common in people with the disease. It also showed that OSCC disrupts normal bacterial patterns linked to age and gender.
Dr. Zhenjiang Zech Xu, a microbiologist at Southern Medical University in Shenzhen, China, led the study. His team focuses on how bacteria interact with the human body.
Xu was interested in studying oral cancer because it is a serious disease with poor survival rates. He also saw potential in using saliva to detect the disease early since collecting saliva samples is easy and painless.
For years, scientists have studied how bacteria in the mouth might be linked to OSCC. Many studies have compared saliva from healthy people to saliva from people with oral cancer. Some researchers found that people with OSCC had more types of bacteria in their mouths (higher microbial diversity), while others found the opposite.
Some studies reported higher amounts of certain bacteria, while others found lower amounts of the same bacteria. These mixed results made it difficult to draw clear conclusions.
Xu’s team solved this problem by combining data from multiple studies. They found several bacteria that consistently appeared in higher numbers in people with OSCC. These included Streptococcus, Lactobacillus, and Prevotella. This suggests that changes in these bacteria could be linked to the disease.
More importantly, the study found that OSCC does more than just change the levels of certain bacteria—it also disrupts normal bacterial patterns linked to age and gender. In healthy people, the microbiome naturally shifts with age and differs between men and women.
However, in people with OSCC, these patterns were no longer predictable. According to Xu, this finding suggests that the disease affects not only individual bacteria but also the way bacteria and the body interact.
After identifying these bacterial changes, the researchers trained a machine learning model to recognize the microbial patterns linked to OSCC. When tested, the model was able to accurately predict whether a person had the disease.
Its accuracy improved when more data was used, suggesting that a saliva-based screening test for OSCC could be developed in the future.
However, Xu warns that the science is not quite ready for clinical use. Researchers still need to confirm these findings in larger studies and establish the best ways to collect and analyze saliva samples.
His team plans to continue studying differences in bacterial patterns across different populations to understand why some people are more at risk than others.
They are also planning a large-scale study that will track high-risk individuals over time. By studying how their oral bacteria change, researchers hope to learn more about the early warning signs of OSCC.
Xu believes that a better understanding of how bacteria in the mouth contribute to cancer could lead to improved diagnostic tools and treatments.
This study is an important step toward using the oral microbiome as a tool for detecting and understanding oral cancer. If researchers can confirm these findings, a simple saliva test could one day help doctors catch the disease earlier, improving the chances of successful treatment.
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The research findings can be found in mSystems.
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