Systematic review on oral microbial dysbiosis and its clinical associations with head and neck squamous cell carcinoma.

ABSTRACT

OBJECTIVES: The relationship between head and neck squamous cell carcinoma (HNSCC) and the oral microbiome has been drawn in various studies. Microbial diversities, microbiome profiles, metagenomic analysis, and host-pathogen interactions were collected from these studies to highlight similarities and account for inconsistencies. We also evaluate the possible clinical applications of the microbiome regarding screening and diagnosis of HNSCC. METHODS: Systematic analysis of studies regarding HNSCC and the microbiome was done according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines. Articles were retrieved from four databases (PubMed, ScienceDirect, CUHK Full-Text Journals, and Cochrane database) and were screened using predefined criteria. RESULTS: Twenty studies were chosen after screening for full-text review. α-diversity comparison was inconsistent whereas ß-diversity between HNSCC and normal samples showed distinct clustering. Microbial dysbiosis characterized by change in the relative abundances of several bacterial species were also seen in HNSCC patients. At a phylum level, inconsistencies were seen between studies using HNSCC tumor tissue samples and saliva samples. At a genus level, Fusobacterium, Peptostreptococcus, Alloprevotella, Capnocytophaga, Catonella, and Prevotella were differentially enriched in HNSCC while Streptococcus, Actinomyces Veillonella, and Rothia were differentially depleted. Co-occurrence network analysis revealed a positive correlation of HNSCC with periodontal pathogens and a negative correlation with commensal bacteria. Metagenomic analysis of microbiota revealed a differential enrichment of pro-inflammatory genomic pathways which was consistent across various studies. Microbial dysbiosis was applied in clinical use as a tool for HNSCC screening. Random-forest analysis was adopted to differentiate between tumor and normal tissue, at 95.7% and 70.0% accuracies respectively in two studies. Microbial dysbiosis index was also used to predict prognosis. CONCLUSIONS: Oral microbial dysbiosis could be a promising tool for HNSCC screening and diagnosis. However, more research should be conducted pertaining to clinical applications to improve diagnostic accuracy and explore other clinical uses.