“The major risk factors, tobacco and alcohol use, alone cannot explain the changes in incidence because oral cancer also commonly occurs in patients without a history of tobacco or alcohol exposure,” said Dr. Brian Schmidt, professor of oral and maxillofacial surgery and director of the Bluestone Center for Clinical Research at the NYU College of Dentistry (NYUCD).
Changes in the microbial community are commonly associated with dental diseases, such as periodontal disease, which is most likely a poly-microbial disease characterized by outgrowth of certain pathologic organisms, as well as chronic periodontitis, which has been reported to be a risk factor for oral premalignant lesions and cancers.
“We know that other cancers, including gallbladder, colon, lung, and prostate, have been associated with particular bacterial infections, so we hypothesized that shifts in the composition of the normal oral cavity microbiome could be promoters or causes of oral cancer,” said Dr. Albertson.
Drs. Schmidt and Albertson and their team profiled cancers and anatomically matched contralateral normal tissue from the same patient by sequencing 16S rDNA hypervariable region amplicons. The team’s findings begin to develop a framework for exploiting the oral microbiome for the monitoring of oral cancer development, progression, and recurrence.
[Note: The team's findings, "Changes in abundance of oral microbiota associated with oral cancer," were published in the June 2, 2014 issue of the online journal, PLOS ONE.]
In cancer samples from both a discovery (n=5) and a subsequent confirmation cohort (n=10), abundance of Firmicutes (especially Streptococcus) and Actinobacteria (especially Rothia) were significantly decreased relative to contralateral normal samples from the same patient. Significant decreases in abundance of these phyla were observed for pre-cancers but not when comparing samples from contralateral sites, such as the tongue and the floor of the mouth, from healthy individuals. Using differences in abundance of the genera Actinomyces, Rothia, Streptococcus, and Fusobacterium, the team was able to separate most cancer samples from pre-cancer and normal samples.
“The oral cavity offers a relatively unique opportunity to screen at-risk individuals for [oral] cancer because the lesions can be seen, and as we found, the shift in the microbiome of the cancer and pre‑cancer lesions, compared to anatomically matched clinically normal tissue from the same individual, can be detected in non‑invasively collected swab samples.” said Dr. Schmidt.
Non-invasively sampling the microbiome of oral lesions and corresponding normal tissue opens the possibility not only to detect cancer‑associated changes at one time point, but the relative stability of the adult oral microbiome also offers the opportunity to monitor shifts in bacterial communities over time.
“Here we observed changes in the microbiome, which, in future larger studies, may be confirmed as a potential biomarker of oral cancers or pre‑cancers and may even have utility for discriminating patients with lymph node metastases,” notes Dr. Albertson. “In addition, there are other challenges in clinical management of oral cancers that would benefit from better diagnostic tools.”
Oral cancer patients are also at risk of second primary cancers and recurrences. The microbiome may provide signatures that can be used as biomarkers for monitoring field changes associated with the high rate of second primary oral cancers and recurrences. The team also notes the possibility of medically modulating the oral microbiome for treatment of oral pre-cancers and damaged fields (field cancerization).
About the Bluestone Center for Clinical Research
The Bluestone Center for Clinical Research, in conjunction with the NYU Oral Cancer Center, is an academic research organization located at the NYU College of Dentistry. Bluestone’s mission is to take a creative scientific approach to transform world health. Bluestone is dedicated to conducting research in oral cancer, cancer symptomology, pharmaceuticals, medical devices, emerging biotechnology, periodontics, implants, and oral health products.
About UC San Francisco
UC San Francisco (UCSF), now celebrating the 150th anniversary of its founding, is a leading university dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care. It includes top-ranked graduate schools of dentistry, medicine, nursing, and pharmacy, a graduate division with nationally-renowned programs in basic, biomedical, translational and population sciences, as well as a preeminent biomedical research enterprise and two top-ranked hospitals, UCSF Medical Center and UCSF Benioff Children’s Hospital San Francisco. Please visit ucsf.edu for more information.
About New York University College of Dentistry
New York University College of Dentistry (NYUCD) is the third oldest and the largest dental school in the U.S., educating more than 8 percent of all dentists. NYUCD has a significant global reach and provides a level of national and international diversity among its students that is unmatched by any other dental school. For more information, please visit nyu.edu/dental.