Last year the news was all abuzz with new evidence that was uncovered by amateur investigators looking into the most infamous hijacker in aviation history, a man known only as DB Cooper. The investigators found traces of material on his tie that was connected to Boeing’s SST development. But the story leaves more unanswered questions than explanations. What parts of the SST did the flecks come from? Engine, fuselage, avionics? Did the flecks come from parts that were manufactured by Boeing or by one of its subcontractors on the project? Did they look at the employee records of Boeing during that time period to see if anyone matching DB Cooper’s description worked for Boeing?
It started me thinking about a number of the stories in cancer research that were equally frustrating, in that the authors failed to tell, what radio personality Paul Harvey liked to refer to as, “The Rest of the Story”.
The story that came readily to mind was a series of articles which identified several species of bacteria which were over-represented in the oral microbiomes of pancreatic cancer patients[1-7] and another study looked at the gut microbiomes of pancreatic cancer patients[5].
Two different sets of studies were performed by different organisations to identify species of oral microbes associated with pancreatic cancer. In one study, the authors found that 2 species of bacteria (Neisseria elongata and Streptococcus mitis) were over-represented in the oral microbiome of pancreatic cancer patients. And the author speculated that the bacteria likely did not play a causative role in the etiology of the disease.
Two studies with different conclusions, and different bacterial species. Which opens the door for a third, as yet unwritten study, to analyze both results and either confirm or fail to confirm one of the previous studies.
The unanswered questions in these studies are:
- How does pancreatic subtyping affect the results seen in these studies? Could both studies be right, and one set of bacteria is more prevalent in one subtype of pancreatic cancer? Is there a link between the immunogenic subtype of pancreatic cancer and the presence of these species?
- Do these populations change throughout the progression of the disease? Do we see a gradual increase in the population as the disease progresses? How does treatment affect the bacterial populations? Are there certain treatments that cause different species to predominate?
- And perhaps the biggest unanswered question is why is this happening? What role do these bacterial species play with regard to pancreatic cancer?
One tantalising idea that arose from this research is that one day your dentist’s oral cancer screening could include a simple test to detect pancreatic cancer at an early stage.
References
- Fan X, Alekseyenko AV, Wu J, Peters BA, Jacobs EJ, Gapstur SM, et al. Human oral microbiome and prospective risk for pancreatic cancer: a population-based nested case-control study. Gut. 2018;67: 120–127.
- Michaud DS, Izard J. Microbiota, oral microbiome, and pancreatic cancer. Cancer J. 2014;20: 203–206.
- Bracci PM. Oral Health and the Oral Microbiome in Pancreatic Cancer. Cancer J Sci Am. 2017;23: 310–314.
- Ertz-Archambault N, Keim P, Von Hoff D. Microbiome and pancreatic cancer: A comprehensive topic review of literature. World J Gastroenterol. 2017;23: 1899–1908.
- Wang C, Li J. Pathogenic Microorganisms and Pancreatic Cancer. Gastrointest Tumors. 2015;2: 41–47.
- Meurman JH. Oral microbiota and cancer. J Oral Microbiol. 2010;2. doi:10.3402/jom.v2i0.5195
- Olsen I. Oral microbial dysbiosis precedes development of pancreatic cancer. J Oral Microbiol. 2017;9: 1374148.