Abstract
The human microbiota, the collection of microbes that inhabit the human body, is increasingly being appreciated as playing a role in human health. A seminal example of this relationship is Helicobacter pylori and gastric cancer oncogenesis. The drop in H.pylori infections and non-cardia gastric cancer incidences has coincided with the rise in oesophageal adenocarcinoma (OAC) incidences. We sought to explore the relationship between the upper digestive tract microbiome and OAC oncogenesis.
Methods
Pinch biopsies were taken from individual’s oesophagus and stomach who were along the metaplasia-dysplasia-adenocarcinoma sequence (GERD, Barrett's oesophagus, dysplasia, OAC, metastatic OAC) as well as healthy controls. We carried out 16 s rRNA gene DNA sequencing protocols on these samples. DNA extraction and library preparation was performed with consideration to the low mass nature of oesophageal biopsies. Raw reads were processed and amplicon sequence variants (ASVs) were generated using the DADA2. We dissected ecological differences between sample site and clinical classification using a variety of approaches including examining differentially abundant taxa and inferred metabolic pathways, alpha diversity and beta-diversity.
Results
The upper digestive tract was found to be dominated by the genera Streptococcus, Prevotella, and Haemophilus. There was no statistically significant shift in beta diversity with respect to biopsy location. Alpha diversity was reduced in gastric biopsies compare to oesophageal biopsies. A slight yet significant shift was seen in beta diversity (Bray–Curtis Dissimilarity) with respect to clinical classification in biopsies derived from the gastroesophageal junction (GEJ) and stomach.
Various taxa were found to be differentially abundant between biopsy site and with regard to clinical classification.
Conclusion
OAC primarily occurs at the GEJ. Community structure was shifted in samples derived from the GEJ and the stomach. Fusobacterium nucleatum was overrepresented in oesophageal biopsies from individuals with diseased oesophagus compared to individuals with a histologically normal oesophagus. This bacterium has been implicated in oncogenesis of various cancers most notably colorectal cancer. Serval ASVs assigned to the genus Prevotella were depleted in stomachs of individuals with metastatic OAC compared to all other groups.
Motor Disorders of the Upper Digestive Tract Review. Clinical Classification of Swallowing Disorders and the Resulting Mechanism of Aspiration.
