Oral microbial community composition is associated with pancreatic cancer: A case-control study in Iran

Objective: Oral microbiota may be related to pancreatic cancer risk because periodontal disease, a condition linked to multiple specific microbes, has been associated with increased risk of pancreatic cancer. We present an evaluation of the association between oral microbiota and pancreatic cancer in Iran.Design: A total of 287 pancreatic adenocarcinoma cases and 300 controls recruited from tertiary hospitals and a specialty clinic in Tehran, Iran provided saliva samples and filled out a questionnaire regarding demographics and lifestyle characteristics. DNA was extracted from saliva and the V4 region of the 16S rRNA gene was PCR amplified and sequenced on the MiSeq. The sequencing data was processed using the DADA2 plugin in QIIME 2 with taxonomic assignment from the Human Oral Microbiome Database. Logistic regression and MiRKAT models were calculated with adjustment for potential confounders.Results: No association was observed for alpha diversity with an average of 91.11 (standard deviation [SD] 2.59) sequence variants for cases and 89.42 (SD 2.58) for controls. However, there was evidence for an association between beta diversity and case status. The association between the Bray-Curtis dissimilarity and pancreatic cancer was particularly strong with a MiRKAT p-value of 0.000142 and specific principal coordinate vectors had strong associations with cancer risk. Several specific taxa were also associated with case status after adjustment for multiple comparisons.Conclusion: The overall microbial community appeared to differ between pancreatic cancer cases and controls. Whether these reflect differences evident before development of pancreatic cancer will need to be evaluated in prospective studies.