Identification & correlation of bacterial diversity in oral cancer and long-term tobacco chewers- A case-control pilot study

Abstract

Introduction. Squamous cell carcinoma is a highly aggressive type of oral cancer (OC). It is the most common cancer among men, and accounts for almost 90 % of all oral cancers in India. Consumption of tobacco is a leading factor contributing to maximum oral cancer incidences as per the WHO. Hypothesis/Gap statement. Researchers reported a direct association of microorganisms with dysbiosis in various oral lesions including oral cancer. However, there is a dearth of information related to compositional changes in the oral microbiome in long-term tobacco chewers and the Indian oral cancer population. Aim. The aim of this study was to identify and correlate the bacterial diversity in the oral cavity of tobacco chewers, patients with oral cancer and healthy subjects in the Indian population. Methods. Oral rinse samples were collected for ten subjects in each group followed by DNA extraction. The variable regions of the bacterial 16S rRNA gene (V6-V8) were amplified, sequenced, processed, and analysed using QIIME2 platform to assess alpha and beta diversity between the study groups. Results. This pilot study showed genus Streptococcus dominated the control group (18.54 %), and the abundance decreased in tobacco and OC group (9.63 and 5.45% respectively); whereas genus Prevotella dominated the tobacco and OC group (21.01 and 26.03% respectively). A shift in abundance of microbiome was observed from control population to oral cancer via the tobacco chewing population. Maximum alpha diversity of oral microbiome was found in Indian tobacco chewers. Beta diversity of tobacco chewers was similar to both the healthy population as well as oral cancer patients suggesting transitioning of the oral microbiome from healthy to oral cancer microbiome via the tobacco chewers microbiome. Conclusion. The data provides evidence of oral bacterial dysbiosis due to tobacco chewing habits that can further lead to progression towards cancer.

Oral Microbial Signatures of Tobacco Chewers and Oral Cancer Patients in India

“…In this study, we have analyzed a larger population group for accurate information regarding the study population compared to an earlier published report [ 13 ]. The present study reveals five phyla and 23 genera contributing to approximately 90% of the total oral microbiome composition.…”

“…Oral rinse samples were collected from study participants as mentioned earlier [ 12 , 13 ]. Briefly, during the sample collection procedure, patients were asked to rinse their mouths for 30 s with sterile normal saline and spit into a sterile tube, of 50 mL.…”

“…DNA extraction, V6–V8 hypervariable region amplification, sequencing, and processing of reads have been carried out as mentioned in our recent publication [ 13 ]. DNA was isolated using the Invitrogen PureLink™ Genomic DNA Kit (Cat no.…”

“…Participants were advised to abstain from eating, drinking, and doing oral hygiene procedures for at least one hour before sample collection. Salivary samples were collected in well-labeled sterile falcon tubes, stored at 4 • C, and processed within 48 h. DNA extraction, V6-V8 hypervariable region amplification, sequencing, and processing of reads have been carried out as mentioned in our recent publication [13]. DNA was isolated using the Invitrogen PureLink™ Genomic DNA Kit (Cat no.…”

Microbial dysbiosis in oral squamous cell carcinoma: A systematic review and meta-analysis

“…To analyse changes in the relative abundance at the genus level, the mean value was extracted directly from nine included literature. In studies in which the mean value was not directly available [ 17 , 22 , 25 , 26 ], it was then extracted from graphs of the original articles as described in a previous study [ 27 ]. To calculate standard deviation (SD), the relative abundance of bacteria genera of each sample and total number of samples were extracted from three studies [ 4 , 28 , 29 ].…”