Oral microbiome profiles in oral potentially malignant disorders and oral cancer - A diagnostic perspective.

Background: Dysregulation of the oral microbiome has been correlated with many diseases, but oral microbiome in the etiopathogenesis of oral cancer remains a grey area and needs to be explored. It is imperative to understand the oral microbiome profiles so as to know the variations in the composition from normal to pre-cancer to cancer.

Aim: To profile the oral microbiome of normal, oral potentially malignant disorders (leukoplakia - Leu, oral submucous fibrosis - OSMF) and oral squamous cell carcinoma (OSCC) by Next-Generation Sequencing of the 16S ribosomal rRNA gene.

Material and methods: This is an observational cross-sectional study. A total of 50 subjects were selected for this study, which included the the normal, Leukoplakia, OSMF, and OSCC groups. Bacterial genomic DNA was extracted, and 16S rRNA gene sequencing of the V4 region was carried out using the Illumina MiSeq system. Bio-informatics data analysis was carried out using the DADA2 pipeline and phyloseq R package, and the t-test was used for statistical analysis.

Results and conclusion: Variations in the composition of the oral microbiome were identified across all study groups, and significant differences were noted in certain microbial taxa across normal, pre-cancer, and cancer. Certain bacterial taxa were detected only in OSCC. An increase in relative abundance of Gram-negative bacteria as well as an increasing trend in the abundance of periodontal taxa was observed in OSCC. This study generated a baseline data which may provide a guideline for future functional and integrative oral microbiome studies. Variations in oral microbiome composition may be used as biomarkers and provide signatures during the progression from normal to pre-cancer to cancer.