Impact of Oral Microbiome on Head and Neck Cancer Development: A Critical Review

A significant contributor to cancer-related morbidity and mortality worldwide is head and neck cancer (HNC). Depending on the affected site, its etiology may include risk factors like geographic differences, genetic predisposition, gender, age, type of diet, smoking and/or alcohol consumption habits, and sexual preferences. Dysbiosis, or disruption of the oral microbiota balance, is another proposed causative factor for HNC. The oral microbiota is home to over 1,000 microbial species, including pathogenic and commensal strains. Disruption of the healthy balance of the oral cavity microbiota triggers the carcinogenic mechanisms by inducing chronic inflammation in the affected site, which acts as a pro-carcinogenic factor by inducing an immune-suppressed microenvironment that induces cell proliferation and inhibits apoptosis. Recent studies have also found that members of the human microbiome are strongly linked to a wide range of cancer types, with well-established associations between the oral microbiota and chronic inflammation and cell proliferation. Aside from chronic inflammation, the bacterial genome, toxins, and metabolites have been proposed as additional factors that induce or facilitate carcinogenesis and its progression in the head and neck region. However, the precise mechanisms remain largely unknown. However, a greater understanding of the underlying mechanisms may lead to the development of novel preventive or customized treatments that can be used in routine clinical practice. The link between oral dysbiosis and the development of HNC is a relatively new and well-received topic in the oncological and dental communities. Therefore, this review intends to provide a comprehensive summary of the currently available information on the potential mechanistic relationships between changes in the oral microbiota and the development of HNC, which is still in the research phase.