Madalina Mocanu, Victor Vlad Costan, Mihai Liviu Ciofu, Mihaela Paula Toader, Cristina Popa, Ana Maria Sciuca, Stefan Toader, Mihaela Pertea
Squamous cell carcinoma is the most common epithelial neoplasm of the head and neck, and it is estimated to represent over 90% of oral neoplasms. Despite therapeutic advances, morbidity and mortality from oral squamous cell carcinoma have not improved significantly in the last 30 years, mainly due to the detection of cases in advanced stages. While tobacco and alcohol use are major risk factors for oral cancer, other known causes are: genetic mutations, dietary deficiencies, prolonged exposure to UV radiation, immunosuppressive conditions, oral or systemic infections. Poor oral hygiene, gingival or periodontal chronic inflammatory conditions, as well as chronic oral erosive lesions favor the appearance of oral infections. Bacterial colonization and adjacent pro-inflammatory status induce the initiation and progression of oncogenic processes by stimulating cell proliferation, angiogenesis, and mutagenic processes. Studies investigating the salivary microbiome, performed on people with precancerous or neoplastic lesions, have shown a decrease in microbial diversity and abundance, especially of the species Firmicutes and Actinobacteria together with the increase in the representation of Lactobacillus. Two theories are formulated to clarify the relationship between the salivary microbiome and oral squamous cell carcinoma. The first discusses bacterial colonization as a direct pathogenic cause of carcinoma, the second describes microbiome abnormalities after tumor onset. In both concepts, metagenomic and transcriptomic changes occur in the salivary microbiome and influence oral cellularity and the immune response. In addition, a combination of both theories is very likely to occur during the progression of oral carcinoma. The analysis of the salivary microbiome as a biomarker for the detection of potentially malignant oral lesions and early oral carcinoma is an innovative and non-invasive method that offers promising prospects. To standardize it, there are numerous molecular and genomic biology studies in progress, extensive studies, including new therapeutic approaches to oral carcinoma by correcting salivary microbiome dysfunctions.