Frontiers | The Role of The Tumor Microbiome in Tumor Development and Its Treatment

Helicobacter pylori (HP)nHighlight:Microbiota, especially gut microbiota, modulates response to cancer treatment and susceptibility to toxic side effectsnHighlight:The gut microbiota can affect local and distant tumors by influencing the immune environment, inflammation, and metabolic patterns of the tumornHighlight:The presence of bacteria in tumor tissues was identified more than 100 years agonHighlight:microbiota has been found in a variety of cancer tissues, including breast, lung, colorectal, and prostate cancers (PCA)nHighlight:extremely low biomassnHighlight:It has been found that a unique microbiome exists in the placenta and that the placental microbiome profile is most similar to that of the human oral microbiome.nHighlight:periodontal pathogens may colonize the placenta through hematogenous infectionnHighlight:Nejman et al. studied 1526 tumors of seven cancer types and their adjacent normal tissues and found that each tumor type has a unique microbiome composition, with breast cancer (BC) having a particularly rich and diverse microbiomenHighlight:Most of the bacteria within the tumors were intracellular and were present in both cancer cells and immune cellsnHighlight:Mycoplasma is also a member of the TM and also has no cell wall. It has been shown that in hepatocellular carcinoma (HCC), mycoplasma infection promotes tumor progression through the interaction of the mycoplasma protein p37 with epithelial cell adhesion moleculesnHighlight:There are several reasons: 1. Cancer cells evade the recognition of immune cells through various mechanisms, resulting in insufficient strength of immune cells inside the tumor, and the interior of the tumor provides a refuge for microorganisms to avoid immune clearance. 2 The hypoxic nature of the interior of many solid tumors results in a low oxygen content compared to normal tissue, providing an environment for anaerobic bacteria to survive. 3. Highly disorganized neovascularization, slow blood flow, and blood leakage inside the tumor lead to bacteria in the blood circulation entering the tumor tissue. 4. Bacteria enter directly through ducts that are connected to the outside world, for example, bacteria enter the pancreas from the duodenum. 5. The tumor tissue is highly nutritious inside and has some metabolites (such as ribose, aspartic acid, etc.) to attract bacterianSticky notes:Important pointnHighlight:In a study of pancreatic cancer (PC), it was found that the gut microbiota can colonize pancreatic tumors, altering tumor bacterial composition and modulating immune function, ultimately affecting the natural course and survival of PCnHighlight:Microorganisms are involved in tumor formation, and 10 microorganisms were identified by the International Agency for Research on Cancer as carcinogenic to humans in 2012.nSticky notes:Include in postnHighlight:The link between TM and cancer has been demonstrated by four main mechanisms: 1. increased gene mutations directly promoting tumorigenesis, 2. regulation of oncogenes or oncogenic pathways, 3. modulation of the host immune system, and 4. production of small molecules or metabolites that influence cancer development, progression, and response to therapeutic agentsnSticky notes:Include in postnHighlight:BC has a richer and more diverse microbiota than other tumors such as PC and melanoma, with an average of 16.4 bacteria species detected per sample in BC, compared to an average of <9 detected in all other tumor typesnHighlight:significant amount of TM was also found to be present in the BC model in mice, and removal of the TM obviously reduced lung metastasis but did not affect the growth of the primary tumor nHighlight:Intratumoral bacteria (mainly Staphylococcus and Lactobacillus) carried by circulating tumor cells can promote BC cell lung metastasis by reorganizing the actin cytoskeleton to enhance resistance to fluid shear stressnHighlight:Compared to normal controls, tumor tissues were enriched in total T cells, CD8⁺ T cells, natural killer (NK) cells, and neutrophils, but reduced in dendritic cells and macrophagesnHighlight:The use of the intra-TM as a biomarker for assessing prognosis and for the treatment of BC is a future research direction.nHighlight:The intracellular metabolism and anticancer activity of dFdC are affected by TM. In vitro experiments revealed that the efficacy of dFdC was significantly reduced in cultures of tumor cells (including BC, Murine leukemia, etc.) infected with Mycoplasma hyorhinis (M. hyorhinis) due to the rapid catabolism of the drug by cytidine deaminase (CDD) produced by M. hyorhinis nHighlight:In vivo experiments also revealed a significant decrease in the antitumor effect of dFdC observed in BC mice whose tumors carried M. hyorhinis infection compared to uninfected micenHighlight:the antitumor activity of dFdC was reduced in tumors containing bacterianHighlight:F. nucleatum can promote CRC metastasis through multiple pathwaysnHighlight:Some bacteria can accelerate tumor progression and cause resistance to chemotherapeutic drugs. nHighlight:The combination of antibiotics and chemotherapeutic drugs can effectively inhibit bacterial growth in tumors, alleviate bacterial-induced cancer resistance, and suppress tumor growthnHighlight: but also affects the role of the gut microbiota in regulating chemotherapy drugsnHighlight:We already know that the gut microbiota can colonize pancreatic tumors, altering tumor bacterial composition and modulating immune function, ultimately affecting the natural course and survival of PCnHighlight:The gut microbiome can influence the efficacy of a variety of drugs such as Cyclophosphamide, Methotrexate, and PD-1 inhibitorsnHighlight:TM is part of the tumor microenvironment and can influence the biological properties of the tumor through its metabolites, but can also be affected by cancer treatmentnHighlight:bacteraemia of some microorganisms is associated with the development of CRC, and that these bacteria may enter the bloodstream from intestinal flora dysbiosis and barrier dysfunctionnHighlight:increased risk of CRC in patients with the presence of Bacteroides fragilis, Streptococcus gallolyticus, F. nucleatum, and other bacteremia,nHighlight:Studies in PTC have found specific TMs associated with higher mutation expression and methylation of tumor suppressorsnHighlight:In patients with esophageal squamous cell carcinoma (ESCC), TM with high levels of F. nucleatum showed a poorer response to chemotherapy, and a high F. nucleatum burden was associated with poor recurrence-free survival (RFS)nHighlight:F. nucleatum is positively correlated with metastasis in CRC and suggests a poor prognosisnHighlight:F. nucleatum also colonizes BC and accelerates tumor growth and metastatic progressionnHighlight:BCG has become the gold standard for the treatment of non muscle-invasive bladder cancernHighlight:BCG induces a strong innate immune response over several weeks, leading to durable anti-tumor adaptive immunitynHighlight:Lactobacillus lactisnHighlight:immunomodulatory activity and it may have promising therapeutic effects against cancer through activation of immune cells, including CD4 or CD8 T cells and natural killer cells, as well as synergistic effects with oxaliplatin chemotherapy.nHighlight:TM may promote tumor progression and may induce chemotherapy resistance,n]]>