The Oral Microbiome and Cancer

Abstract

There is mounting evidence that members of the human microbiome are highly associated with a wide variety of cancer types. Among oral cancers, oral squamous cell carcinoma (OSCC) is the most prevalent and most commonly studied, and it is the most common malignancy of the head and neck worldwide. However, there is a void regarding the role that the oral microbiome may play in OSCC. Previous studies have not consistently found a characteristic oral microbiome composition associated with OSCC. Although a direct causality has not been proven, individual members of the oral microbiome are capable of promoting various tumorigenic functions related to cancer development. Two prominent oral pathogens, Porphyromonas gingivalis, and Fusobacterium nucleatum can promote tumor progression in mice. P. gingivalis infection has been associated with oro-digestive cancer, increased oral cancer invasion, and proliferation of oral cancer stem cells. The microbiome can influence the evolution of the disease by directly interacting with the human body and significantly altering the response and toxicity to various forms of cancer therapy. Recent studies have shown an association of certain phylogenetic groups with the immunotherapy treatment outcomes of certain tumors. On the other side of the coin, recently it has been a resurgence in interest on the potential use of bacteria to cure cancer. These kinds of treatments were used in the late nineteenth and early twentieth centuries as the first line of defense against cancer in some hospitals but later displaced by other types of treatments such as radiotherapy. Currently, organisms such as Salmonella typhimurium and Clostridium spp. have been used for targeted strategies as potential vectors to treat cancer. In this review, we briefly summarize our current knowledge of the role of the oral microbiome, focusing on its bacterial fraction, in cancer in general and in OSCC more precisely, and a brief description of the potential use of bacteria to target tumors.

Comprehensive analysis of bacteriocins in Streptococcus mutans

“…Since S. mutans is a key bacterium for the formation of dental plaques, the type of bacteriocin in S. mutans affects the composition of bacterial flora in dental plaques. To date, many investigations regarding the oral bacterial composition in saliva and dental plaque have been performed 24 – 28 . In particular, comparative analyses between healthy subjects and those with oral diseases, such as periodontitis, dental caries and oral cancer, have been demonstrated to identify the key bacteria or bacterial flora specific for the disease or health status.…”

Feasibility of investigating the association between bacterial pathogens and oral leukoplakia in low and middle income countries: A population-based pilot study in India

“…gingivalis , to evade host immune mechanisms enables them to survive in systemic circulation and reach distant organ sites [ 2 ]. Due to these properties, emerging evidence shows positive associations of oral bacterial pathogens not only with oral potentially malignant lesions [ 5 , 8 ] and oral or orodigestive cancers, [ 30 – 33 ] but also with distant cancer sites [ 1 , 34 , 35 ]. Recent meta-analysis on the effect of periodontal bacteria infection on incidence and prognosis of cancer confirmed that P .…”

“…The ability of these pathogens, particularly P. gingivalis, to evade host immune mechanisms enables them to survive in systemic circulation and reach distant organ sites [2]. Due to these properties, emerging evidence shows positive associations of oral bacterial pathogens not only with oral potentially malignant lesions [5,8] and oral or orodigestive cancers, [30][31][32][33] but also with distant cancer sites [1,34,35]. Recent meta-analysis on the effect of periodontal bacteria infection on incidence and prognosis of cancer confirmed that P.gingivalis and P.intermedia infection was associated with high incidence of cancer and P.gingivalis and F. nucleatum infection was associated with poor prognosis [36].…”

The Presence of HPV in Dental Calculus: It’s Role in Pathogenesis of Oral and Cervical Cancer

“…An increased risk of developing oral squamous cell carcinoma (OSCC) associated with periodontitis suggests a possible role of inflammation caused by the microbiome with oral cancer. Periodontitis is a typical example of an infectious disease causing chronic inflammation in the oral cavity [56]. Recent evidence proved the role of microbiomederived signals in the pathogenesis of several chronic inflammatory diseases.…”

“…Chronic infection with P. gingivalis and Fusobacterium nucleatum has been recently demonstrated to promote tongue tumors in a murine model through direct interaction with oral epithelial cells, leading to upregulation of the IL-6-STAT3 pathway in a TLR2-dependent manner [56]. P. gingivalis was also shown to cause gingival epithelial cells (GECs) to migrate in a manner which depends on the overexpression of Zeb1, an activator of the epithelial-mesenchymal transition (EMT).…”