Dysbiosis in the oral environment may play a role in the etiopathogenesis of oral squamous cell carcinoma (OSCC). This review aims to summarize the current knowledge about the association of oral microbiota with OSCC and to describe possible etiopathogenetic mechanisms involved in processes of OSCC development and progression. Association studies included in this review were designed as case–control/case studies, analyzing the bacteriome, mycobiome, and virome from saliva, oral rinses, oral mucosal swabs, or oral mucosal tissue samples (deep and superficial) and comparing the results in healthy individuals to those with OSCC and/or with premalignant lesions. Changes in relative abundances of specific bacteria (e.g., Porphyromonas gingivalis, Fusobacterium nucleatum, Streptococcus sp.) and fungi (especially Candida sp.) were associated with OSCC. Viruses can also play a role; while the results of studies investigating the role of human papillomavirus in OSCC development are controversial, Epstein–Barr virus was positively correlated with OSCC. The oral microbiota has been linked to tumorigenesis through a variety of mechanisms, including the stimulation of cell proliferation, tumor invasiveness, angiogenesis, inhibition of cell apoptosis, induction of chronic inflammation, or production of oncometabolites. We also advocate for the necessity of performing a complex analysis of the microbiome in further studies and of standardizing the sampling procedures by establishing guidelines to support future meta-analyses.

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Background. Squamous cell carcinoma of the oral cavity is generally caused by the long-term impact of known risk factors, e.g. tobacco and alcohol, along with chronic traumatisation. A number of studies now implicate HPV infection in head and neck tumour carcinogenesis but the exact role of HPV infection in the oral cavity remains unclear. Methods. In this study, we evaluated 78 patients with oral squamous cell carcinoma (OSCC) for the expression of protein p16 in the context of HPV positivity and its influence on the overall survival rate, disease location, staging and grading. Results. Regarding the tumour location, no significant difference was found between HPV-positive and HPV-negative patients, nor between p16-positive and p16-negative patients. There was also no trend in terms of HPV status and stage, and differentiation of carcinoma. There was no effect on HPV-positive patients relative to the time to progression (P=0.84) and overall survival rate (P=0.78). P16 positivity was not found to have an effect on the overall survival rate of patients (P=0.41) and there was no correlation between p16 positivity relative to the time to progression (P=0.66). Conclusions. In summary, the data suggest that there is no effect of HPV status on the prognosis of OSCC patients compared to other HNSCC locations.

Host genetic predispositions to dysregulated immune response can influence the development of the aggressive form of periodontitis (AgP) through susceptibility to oral dysbiosis and subsequent host-microbe interaction. This case-control study aimed to perform a multilocus analysis of functional variants in selected interleukin (IL) genes in patients with the generalized form of AgP in a homogenous population. Twelve polymorphisms in IL-1 gene cluster, IL-6 and its receptor, IL-10, IL-17A, and IL-18 were determined in 91 AgP patients and 210 controls. Analysis of seven selected periodontal bacteria in subgingival sulci/pockets was performed with a commercial DNA-microarray kit in a subgroup of 76 individuals. The pilot in vitro study included stimulation of peripheral blood monocytes (PBMC) from 20 individuals with periodontal bacteria and measurement of IL-10 levels using the Luminex method. Only the unctional polymorphism IL-10 −1087 A/G (rs1800896) and specific IL-10 haplotypes were associated with the development of the disease (p < 0.05, Pcorr > 0.05). Four bacterial species occurred more frequently in AgP than in controls (p < 0.01, Pcorr < 0.05). Elevated IL-10 levels were found in AgP patients, carriers of IL-10 −1087GG genotype, and PBMCs stimulated by periodontal bacteria (p < 0.05, Pcorr > 0.05). We therefore conclude that a combination of genetic predisposition to the altered expression of IL-10 and the presence of specific periodontal bacteria may contribute to Th1/Th2 balance disruption and AgP development.