Dysbiosis of Oral Microbiota and Its Effect on Epithelial-Mesenchymal Transition: a Review

Malignancies of the oral cavity are common all over the world as well as in India. It has been estimated that, on an average, 70–80% of oral cancers are caused by excessive chewing of betel nut and areca nut and smoking. The cancers arise from various pre-existing potentially malignant lesions and conditions, which are aggravated by various pathogenic oral microbiome. The existing literature credits microbial dysbiosis as one of the key factors behind a number of oral diseases. Interaction between oral epithelial cells and microbes endows oral cells with the capability of undergoing invasion and metastasis. This microbial interference to the transformed epithelial cells promotes epithelial-mesenchymal transition (EMT). Epithelial-mesenchymal transition is a physiological process which allows polarized epithelial cells to mimic mesenchymal phenotype through various biochemical and molecular changes. Epithelial cell interacts with basal membrane via basal cells. EMT induces the invasiveness of these cells leading to metastasis, resistance to apoptosis, and increased production of extracellular matrix components. They degrade the basement membrane and form mesenchymal-like cells that migrate away from the epithelial layer. Microbial intervention causes downregulation of important epithelial markers like E-cadherin and β-catenin along with upregulation of mesenchymal markers, such as N-cadherin, vimentin, and fibronectin. The current review tries to discuss the role of oral microbiota in hastening the process of EMT and the possible mechanisms involved in it.