Emerging role of bacteria in oral carcinogenesis: a review with special reference to perio-pathogenic bacteria

Abstract

Oral cancer, primarily oral squamous cell carcinoma (OSCC), continues to be a major global health problem with high incidence and low survival rates. While the major risk factors for this malignancy, mostly lifestyle related, have been identified, around 15% of oral cancer cases remain unexplained. In light of evidence implicating bacteria in the aetiology of some cancer types, several epidemiological studies have been conducted in the last decade, employing methodologies ranging from traditional culture techniques to 16S rRNA metagenomics, to assess the possible role of bacteria in OSCC. While these studies have demonstrated differences in microbial composition between cancerous and healthy tissues, they have failed to agree on specific bacteria or patterns of oral microbial dysbiosis to implicate in OSCC. On the contrary, some oral taxa, particularly Porphyromonas gingivalis and Fusobacterium nucleatum, show strong oral carcinogenic potential in vitro and in animal studies. Bacteria are thought to contribute to oral carcinogenesis via inhibition of apoptosis, activation of cell proliferation, promotion of cellular invasion, induction of chronic inflammation, and production of carcinogens. This narrative review provides a critical analysis of and an update on the association between bacteria and oral carcinogenesis and the possible mechanisms underlying it.

Strategies for Increasing Pancreatic Tumor Immunogenicity

“…Alternatively, it is biologically plausible that certain microbes may directly facilitate PDAC carcinogenesis. Consistent with this notion, the colonic bacterium Enterotoxigenic Bacteroides fragilis has been implicated in causing colon cancer via IL-17 production (94), and Porphyromonas has been implicated in carcinogenesis of oral squamous cell carcinoma in preclinical models (95). Although IL-17 has been implicated in facilitating PDAC and may emerge as a potential therapeutic target (80,81), further studies are needed to determine whether alterations in the oral microbiome play a role in the development of PDAC, which immune signals are involved,or if these findings are simply correlative.…”

Poor oral health affects survival in head and neck cancer

“…19,36–38 Likewise, oral bacterial dysbiosis, particularly involving Porphyromonas gingivalis and F. nucleatum, have been implicated in the development of oral cancer in human and animal studies. 39–41 Possible mechanisms include the induction of chronic inflammation, 40,42,43 promotion of cellular invasion, 40 and direct production of carcinogens. 40,44,45 These local mechanisms that promote bacterial carcinogenesis could also affect tumor behavior and influence patient survival.…”

Inflammatory bacteriome featuring Fusobacterium nucleatum and Pseudomonas aeruginosa identified in association with oral squamous cell carcinoma

“…pylori in gastric cancer 7 . A number of studies have been carried out to this effect using various methods ranging from cultivation to 16S rRNA gene sequencing 8–20 .…”