Variations of oral microbiota are associated with pancreatic diseases including pancreatic cancer

Abstract

Objective: The associations between oral diseases and increased risk of pancreatic cancer have been reported in several prospective cohort studies. In this study, we measured variations of salivary microbiota and evaluated their potential associations with pancreatic cancer and chronic pancreatitis.

Methods: This study was divided into three phases: (1) microbial profiling using the Human Oral Microbe Identification Microarray to investigate salivary microbiota variation between 10 resectable patients with pancreatic cancer and 10 matched healthy controls, (2) identification and verification of bacterial candidates by real-time quantitative PCR (qPCR) and (3) validation of bacterial candidates by qPCR on an independent cohort of 28 resectable pancreatic cancer, 28 matched healthy control and 27 chronic pancreatitis samples.

Results: Comprehensive comparison of the salivary microbiota between patients with pancreatic cancer and healthy control subjects revealed a significant variation of salivary microflora. Thirty-one bacterial species/clusters were increased in the saliva of patients with pancreatic cancer (n=10) in comparison to those of the healthy controls (n=10), whereas 25 bacterial species/clusters were decreased. Two out of six bacterial candidates (Neisseria elongata and Streptococcus mitis) were validated using the independent samples, showing significant variation (p<0.05, qPCR) between patients with pancreatic cancer and controls (n=56). Additionally, two bacteria (Granulicatella adiacens and S mitis) showed significant variation (p<0.05, qPCR) between chronic pancreatitis samples and controls (n=55). The combination of two bacterial biomarkers (N elongata and S mitis) yielded a receiver operating characteristic plot area under the curve value of 0.90 (95% CI 0.78 to 0.96, p<0.0001) with a 96.4% sensitivity and 82.1% specificity in distinguishing patients with pancreatic cancer from healthy subjects.

Conclusions: The authors observed associations between variations of patients' salivary microbiota with pancreatic cancer and chronic pancreatitis. This report also provides proof of salivary microbiota as an informative source for discovering non-invasive biomarkers of systemic diseases.

Figure 1

chematic of the strategy used for the discovery (including verification) and validation of salivary bacterial biomarkers. PC, pancreatic cancer; HC, healthy control; CP, chronic pancreatitis.

Figure 2

16S rRNA gene-based phylogenetic tree of 56 varied clusters/genera between patients with pancreatic cancer and healthy controls. Thirty-one clusters/species increased in the saliva of pancreatic cancer patients were marked with triangles. The phylogenetic tree was inferred by a minimum evolution analysis of 16S rRNA sequences.

Figure 3

nteractive dot diagram analysis and receiver operating characteristic (ROC) curve analysis for the predictive power of combined salivary bacterial biomarkers. The validated biomarkers were evaluated by logistic regression within three levels of clinical discrimination categories: pancreatic cancer versus healthy control (A), pancreatic cancer versus chronic pancreatitis (B) and pancreatic cancer versus non-cancer (healthy control + chronic pancreatitis) (C). The sensitivity and specificity for each model were obtained by identifying the cut-off point in the predicted probabilities from the logistic regression that maximised the sum of the sensitivity plus specificity. In general, these cut-off points correspond well with the proportion of patients with cancer evaluated in each model.