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Fig. 4 | BMC Microbiology

Fig. 4

From: Oral microbiota and Helicobacter pylori in gastric carcinogenesis: what do we know and where next?

Fig. 4

Oral bacteria produce some substances that play a role in chronic inflammation, genomic instability, tumor angiogenesis, and progression of gastric cancer. Some oral bacteria generate VSCs including CH3SH, H2S, CH3SSCH3, and (CH3)2S that may develop chronic inflammation. Oral bacteria are also involved in the production of ROS, RNS and H2O2, which may be involved in genotoxicity. Some species can generate organic acids (e.g., isobutyric, butyric, isocaproic, and isovaleric acids) that may contribute to cell metastasis. H2S may cause genomic instability, effects on inflammation, apoptosis, and many gastrointestinal processes like cancer. Other oral bacteria generate lactic acid, which is a source of energy for tumor cells and is involved in increasing ATP levels, which may exacerbate inflammation and angiogenesis. Some of them are able to metabolize alcohol to acetaldehyde by ADH enzyme, which is involved in carcinogenesis. VSCs: volatile sulfur compounds, CH3SH: including methyl mercaptan, H2S: hydrogen sulfide, CH3SSCH3: dimethyl disulfide, and (CH3)2S: dimethyl sulfide, ROS: reactive oxygen species, RNS: reactive nitrogen species, H2O2: hydrogen peroxide, ATP: Adenosine triphosphate, ADH: alcohol dehydrogenase

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