16S rRNA based metagenomic analysis unveils unique oral microbial signatures in oral squamous cell carcinoma cases from Coastal Karnataka, India.

Oral Squamous cell carcinoma (OSCC) is the 14th most frequent cancer with 300,000 new cases and 100,000 deaths reported annually. Even with advanced therapy, the treatment outcomes are poor at advanced stages of the disease. The diagnosis of early OSCC is of paramount clinical value given the high mortality rate associated with the late stages of the disease. Recently, the role of microbiome in the disease manifestation, including oral cancer, has garnered considerable attention. But, to establish the role of bacteria in oral cancer, it is important to determine the differences in the colonization pattern in non-tumour and tumour tissues. In this study, 16S rRNA based metagenomic analyses of 13 tumorous and contralateral anatomically matched normal tissue biopsies, obtained from patients with advanced stage of OSCC were evaluated to understand the correlation between OSCC and oral microbiome. In this study we identified Fusobacterium, Prevotella, Capnocytophaga, Leptotrichia, Peptostreptococcus, Parvimonas and Bacteroidetes as the most significantly enriched taxa in OSCC lesions compared to the non-cancerous tissues. Further, PICRUSt2 analysis unveiled enhanced expression of metabolic pathways associated with L-lysine fermentation, pyruvate fermentation, and isoleucine biosynthesis in those microbes associated with OSCC tissues. These findings provide valuable insights into the distinctive microbial signatures associated with OSCC, offering potential biomarkers and metabolic pathways underlying OSCC pathogenesis. While our focus has primarily centred on microbial signatures, it is essential to recognize the pivotal role of host factors such as immune responses, genetic predisposition, and the oral microenvironment in shaping OSCC development and microbiome composition.