Oral microbiota are among the most diverse in the human body. More than 700 species have been identified in the mouth, and new sequencing methods are allowing us to discover even more species. The anatomy of the oral cavity is different from that of other body sites. The oral cavity has mucosal surfaces (the tongue, the buccal mucosa, the gingiva, and the palate), hard tissues (the teeth), and exocrine gland tissue (major and minor salivary glands), all of which present unique features for microbiota composition. The connection between oral microbiota and diseases of the human body has been under intensive research in the past years. Furthermore, oral microbiota have been associated with cancer development. Patients suffering from periodontitis, a common advanced gingival disease caused by bacterial dysbiosis, have a 2-5 times higher risk of acquiring any cancer compared to healthy individuals. Some oral taxa, especially Porphyromonas gingivalis and Fusobacterium nucleatum, have been shown to have carcinogenic potential by several different mechanisms. They can inhibit apoptosis, activate cell proliferation, promote cellular invasion, induce chronic inflammation, and directly produce carcinogens. These microbiota changes can already be seen with potentially malignant lesions of the oral cavity. The causal relationship between microbiota and cancer is complex. It is difficult to accurately study the impact of specific bacteria on carcinoma development in humans. This review focuses on the elucidating the interactions between oral cavity bacterial microbiota and cancer. We gather literature on the current knowledge of the bacterial contribution to cancer development and the mechanisms behind it.

中文翻译：

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口腔微生物群与癌症发展

口腔微生物群是人体中最多样化的。口腔中已鉴定出 700 多种物种，新的测序方法使我们能够发现更多物种。口腔的解剖结构不同于身体其他部位的解剖结构。口腔具有粘膜表面（舌头、颊粘膜、牙龈和上颚）、硬组织（牙齿）和外分泌腺组织（大唾液腺和小唾液腺），所有这些都呈现出微生物群组成的独特特征. 口腔微生物群与人体疾病之间的联系在过去几年中一直处于深入研究之中。此外，口腔微生物群与癌症的发展有关。患有牙周炎的患者，这是一种由细菌失调引起的常见晚期牙龈疾病，与健康人相比，患任何癌症的风险要高 2-5 倍。一些口腔分类群，尤其是牙龈卟啉单胞菌和具核梭杆菌，已通过几种不同的机制显示出具有致癌潜力。它们可以抑制细胞凋亡，激活细胞增殖，促进细胞侵袭，诱发慢性炎症，并直接产生致癌物质。这些微生物群的变化已经可以在口腔潜在的恶性病变中看到。微生物群与癌症之间的因果关系是复杂的。很难准确研究特定细菌对人类癌症发展的影响。本综述重点阐明口腔细菌微生物群与癌症之间的相互作用。