Abstract
Accumulating evidence demonstrates that the oral pathobiont Fusobacterium nucleatum is involved in the progression of an increasing number of tumors types. Thus far, the mechanisms underlying tumor exacerbation by F. nucleatum include the enhancement of proliferation, establishment of a tumor‐promoting immune environment, induction of chemoresistance, and the activation of immune checkpoints. This review focuses on the mechanisms that mediate tumor‐specific colonization by fusobacteria. Elucidating the mechanisms mediating fusobacterial tumor tropism and promotion might provide new insights for the development of novel approaches for tumor detection and treatment.
Keywords: Fusobacterium nucleatum, oncobacteria, oncobiont, pathobiont
1. INFECTIVE AGENTS AND CANCER
In 1911, a causal role of microbes in cancer was first revealed by Peyton Rous who demonstrated that sarcoma can be induced in chickens by a virus. 1 The link between a virus and human cancer was demonstrated 53 years later by Epstein, Achong and Barr as evidenced by the presence of Epstein–Barr virus in Burkitt lymphoma cells visualized by electron microscopy. 2 This was followed with the association of hepatitis B and C viruses with liver cancer, papillomavirus with cervical cancer and herpesviruses with Kaposi sarcoma. 3
In contrast to viruses, which play critical roles in cancer, bacteria were first considered as anti‐cancer agents (reviewed in reference 4 ). In 1813, Vautier reported that patients with cancer who developed gas gangrene showed tumor regression. 5 German physicians Busch and Fehleisen independently observed the regression of tumors in patients with cancer suffering from erysipelas infection. In 1868, Busch infected a cancer patient with erysipelas and noted tumor shrinkage. In 1882, Fehleisen repeated this treatment and identified Streptococcus pyogenes as the causative agent of erysipelas. 4 Furthermore, in the United States in the early 1890s, a surgeon named William Coley pioneered the use of bacteria and their extracts (Coley's toxins) to evoke anti‐tumor immunity and successfully treat cancer patients. 6 However, the high‐degree of success of newly developed radiation therapy led to a decline in the application of Coley's toxins as cancer treatment (reviewed in reference 7 ). Bacterial‐based anticancer treatment reemerged in 1990, when the FDA approved the Bacillus Calmette–Guérin (BCG) vaccine, a live attenuated form of Mycobacterium bovis that is used against tuberculosis, for treating noninvasive bladder cancer. 8 , 9 Currently, BCG is the only anti‐cancer bacterial agent approved for routine clinical use. 4 BCG, and fungal‐derived polysaccharide β‐glucan, can promote a sustained enhanced response of myeloid and natural killer (NK) cells to secondary infectious, inflammatory challenges, and tumors. This process of non‐specific memory of innate immune cells, facilitates the heightened response of these cells, as well as that of their progeny, to future challenges, and has been termed ‘‘trained innate immunity’’ or ‘‘innate immune memory’’. 10 , 11 Trained immunity is mediated via transcriptomic, epigenetic, and metabolic reprogramming. 11 NK cells, 12 and the induction trained immunity, 13 are hypothesized to play important roles in BCG immunotherapy for noninvasive bladder cancer. 14
The realization that Helicobacter pylori is a causative agent of gastric cancers in the 1990s indicated that bacteria are involved in tumor promotion. 15 , 16 , 17 , 18 Furthermore, mice that were genetically susceptible to cancer developed significantly fewer tumors under germ‐free conditions than those with conventional microbiota, thus supporting the pro‐tumorigenic roles of bacteria. 19 , 20 Studies employing advanced genomic sequencing and microbiome characterization methods indicate the association of bacterial species with specific cancers. 21 , 22 Multiple features of tumor, including proliferation, survival, progression, immunogenicity, sensitivity, and resistance to therapy, are affected by their interaction with the components of their microbial environment. 22 , 23 Although some bacterial species can promote cancer, those found to have reduced abundance in cancers might have cancer‐inhibitory actions or antagonistic interactions with tumor‐promoting bacteria. 24 , 25
Among the first bacteria suggested as potential cancer drivers are Escherichia coli strains that generate a mutagenic toxin called colibactin, which can induce single‐strand DNA breaks, and fragilysin‐expressing Bacteroides fragilis, which is genotoxic and can cleave the tumor suppressor protein E‐cadherin. 19 Streptococcus gallolyticus (former Streptococcus bovis) bacteremia is an indicator of colorectal cancer since 1951 26 ; however, the specific bacteria–cancer interaction is not understood. Overall, approximately 16% to 20% of cancer incidence can be linked to infectious agents. 27 , 28 , 29 A recent report comprehensively characterized the microbiome of seven solid tumors. 21
Cancer is among the comorbidities affected by periodontal pathobionts. 30 , 31 , 32 Fusobacterium nucleatum the focus of the review, is an oral oncobiont mostly associated with the development of periodontitis. Highly abundant F. nucleatum has been detected in various types of cancer, including colorectal (CRC), 33 , 34 pancreatic, 35 , 36 esophageal, 37 , 38 and breast cancers, 39 , 40 and associated with shorter survival in patients with CRC, pancreatic, and esophageal cancers. 35 , 37 , 38 , 41 , 42 Accumulating evidence indicating that F. nucleatum accelerates tumorigenesis 40 , 43 , 44 , 45 , 46 , 47 , 48 and induces resistance to chemotherapy 49 , 50 , 51 , 52 may provide rational for the association of high amounts of F. nucleatum with poor disease outcome.
The mechanisms by which F. nucleatum accelerates tumor progression and metastasis and induces tumor‐chemoresistance have been thoroughly reviewed previously. 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 This paper focuses on fusobacterial mechanisms that guide tumor‐specific colonization and protect tumors against anti‐tumor immunity.
2. FUSOBACTERIUM NUCLEATUM IN THE ORAL CAVITY
Fusobacterium nucleatum is a gram‐negative, spindle‐shaped, non‐spore forming, oral anaerobe and is one of the most abundant gram‐negative species residing in the human oral cavity. 68 , 69 It is one of the pathobionts that outgrow during dysbiosis that precedes periodontal disease 68 , 69 and assist keystone species such as Porphyromonas gingivalis 70 in disrupting host–microbial homeostasis and inducing periodontitis. 71 , 72 It can be found on the dorsal surface of the tongue 73 , 74 and in multispecies biofilms at the gingival margin of the tooth, where it is hypothesized to play an important role in the development of the subgingival dental plaque. Owing to its abundant adhesion mechanisms, F. nucleatum can bind many oral bacterial species. Attachment between different oral colonizers is termed coaggregation or coadherence. 75 , 76 , 77 By coaggregation with early oral colonizers capable of attaching to oral surfaces, such as Streptococcus species (via the RadD adhesin), 78 and the largely anaerobic secondary colonizers that are associated with periodontal disease, including Porphyromonas gingivalis (via Fap2 as will be discussed below), Treponema denticola, and Aggregatibacter actinomycetemcomitans, and bridging them, F. nucleatum play a scuffle‐like, structurally supportive role in the oral biofilm that can resist washing by the saliva and gingival crevicular fluid. Multispecies bridging also facilitates multi‐species community existence, including communication, cross‐feeding, and metabolic interactions (Figure 1). 55 , 75 , 76 , 79
3. FUSOBACTERIUM NUCLEATUM IS OVERABUNDANT IN COLORECTAL CANCER
CRC is the second most common cause of cancer deaths in the United States 80 and the fourth leading cause of cancer‐related deaths worldwide. 81 The burden of CRC is rapidly increasing in developing countries as they adopt western lifestyles. 81 In 2012, two studies employing applied computational approaches found increased fusobacteria (particularly F. nucleatum) DNA or RNA levels in colorectal cancer tissues compared to adjacent normal tissues. 33 , 34 This discovery was unexpected as fusobacteria are the core resident members of the human oral microbiome and infrequently found in the gut. 82 , 83 Live F. nucleatum directly isolated from biopsy samples 34 , 84 , 85 and patient‐derived xenografts in mice 46 confirmed these metagenomic results. Interestingly, the proportion of F. nucleatum–high colorectal cancers gradually increased from rectal cancers to the cecal cancers. 86 Remarkably, a stronger association between F. nucleatum and CRC patients was found in Asiatic populations than in European and American populations (for a recent systematic review and meta‐analysis, please see references 42 , 87 ). In addition, F. nucleatum in CRC patients was frequently detected with other oral anaerobic species including Peptostreptococcus spp. 46 , 88 Leptotrichia and Campylobacter. 89 Increasing evidence indicates that the presence of F. nucleatum in colon cancer is associated with resistance to chemotherapy, disease recurrence, and poor prognosis, which will be discussed in detail in section 9 below.
4. CRC‐ASSOCIATED F. NUCLEATUM ORIGINATES FROM THE ORAL MICROBIOTA
Although F. nucleatum is a common oral isolate, it is not abundantly found in the gut microbiota. Thus, fusobacteria detected in colon cancer samples are speculated to be of oral origin. To confirm this hypothesis, Komiya et al 90 collected colon cancer specimens and matched saliva samples from 14 CRC patients and isolated F. nucleatum strains (n = 361) from the tumors of eight (57.1%) and the saliva of all 14 patients. Matching patterns of arbitrarily primed PCR products of tumor and oral isolates were found in six of eight (75%) patients thus suggesting that fusobacteria found in colon cancer tumors originated from the oral cavity. To further verify these results, Abed et al 85 isolated the genomic DNA of F. nucleatum obtained from paired oral and adenocarcinoma samples from three patients. Genomic DNA was sequenced and compared with the available fusobacterial genomes deposited in the Sequence Read Archive (SRA) database. The results revealed the extremely close evolutionary relationship between each oral and matching tumor isolate, thereby supporting fusobacteria from the oral cavity may seed and become enriched in colorectal cancers. 85 The frequent co‐occurrence of F. nucleatum in tumors with potential oral coaggregation partners, including Peptostreptococcus spp. 46 , 88 Leptotrichia and Campylobacter spp., 89 also substantiate the oral origin of colorectal cancer‐colonizing fusobacteria.
5. ORAL F. NUCLEATUM CAN TRANSLOCATE TO COLORECTAL TUMORS VIA THE HEMATOGENOUS ROUTE
Considering the oral origin of colon cancer‐associated fusobacteria, the route of their oral to tumor transmission remained to be resolved. Kostic et al 45 demonstrated that oral fusobacteria can reach colon tumors by descending via the digestive tract. 45 However, hematogenous translocation that can occur during frequent gingival bleeding 91 is also possible. Such hematogenous transfer of oral fusobacteria to the placenta was previously observed, thus explaining its high occurrence in preterm births. 92 (Reviewed in this volume by Y. W. Han).
Abed et al 85 studied the preferred oral tumor route by employing two orthotropic mouse colon cancer models, namely MC38 in C57BL/6 mice and CT26 in BALB/C mice. They compared colon tumor colonization by F. nucleatum that was intravascularly injected via the tail vein or administered via oral gavage. Under the tested conditions, tumor colonization by the intravascularly injected fusobacteria is more efficient than that of the gavage‐inoculated ones in both mouse models. 85 Intravenously injected fusobacteria were detected in mouse CT26 colon tumors at 2 h post‐delivery, and their levels remained stable at 6 h post‐infection. Fusobacterial proliferation in the tumor was observed at 24 h and 72 h post‐infection. 85
The magnitude of bacteremia resulting after a dental procedure and routine daily activities is significantly lower (<104 CFU/ml) 93 than that tested in the experiments described above (1 × 107–1 × 108 F. nucleatum per mouse). However, when fusobacteria were inoculated in physiological doses in the orthotropic MC38 CRC model, tumor‐associated fusobacteria were also detected in mice inoculated with the more physiologic dose range (1 × 104 F. nucleatum 93 ). Increased doses resulted in increased proportion of mice‐bearing tumors with intertumoral fusobacteria. In detail, fusobacteria were detected in the tumors of 45% of mice‐bearing tumors inoculated with 5 × 103 to 1 × 104 F. nucleatum; 60%, 5 × 104 to 1 × 105; and 100%, 5 × 106 to 1 × 107. Thus, lowering the fusobacterial inoculation dose did not suppress colon tumor colonization but rather reduced its efficiency. These results may explain the heterogeneity observed in fusobacterial occurrence in 3% to 56% of human colorectal cancer. 55
The above results do not rule out that oral fusobacteria, which are constantly swallowed, may colonize colon tumors through the digestive tract. However, the hematogenous dissemination of oral fusobacteria to CRC is biologically conceivable as bloodstream travel circumvents the toxicity of low gastric pH and bile acids encountered upon descent to the gastrointestinal tract. Furthermore, bloodstream travel affords fusobacteria an escape from competition with the endogenous colonic microbiota. 85
6. FAP2–GLYCANS INTERACTIONS GUIDE F. NUCLEATUM COLONIZATION IN COLORECTAL CANCER
Whether oral fusobacteria translocate to colon tumors via the blood circulation or descending through the digestive tract, mechanisms that home and localize fusobacteria to colorectal tumors must exist. Tumor‐induced conditions, including increased blood supply, blood vessel leakiness, hypoxia, and immunosuppressive microenvironment, are non‐specific factors that might contribute to a niche that promotes fusobacterial survival. However, these local environmental conditions are apparently not sufficient to enable the localization of other abundant oral anaerobic bacteria, such as Porphyromonas gingivalis, to colon cancers. 94 Therefore, specific factors and mechanisms might be required for CRC colonization by fusobacteria. Current evidence suggests that tumor localization by F. nucleatum is dictated by glycan–lectin interactions.
D‐galactose‐β(1‐3)‐N‐acetyl‐D‐galactosamine (Gal‐GalNAc) or an unknown structural‐related sugar moiety is hypothesized as a tumor ligand for fusobacterial attachment. Gal‐GalNAc was found to be over‐displayed in sections of colorectal adenocarcinoma and has been suggested as a biomarker for colon cancer. 95 GalNAc and Gal‐GalNAc are O‐GalNAc glycans and protein post‐translational modifications. In the biosynthesis of O‐GalNAc glycans, the first step involves the covalent linkage of N‐acetylgalactosamine (GalNAc) to selected Ser/Thr residues of the acceptor protein to yield GalNAcα1‐O‐Ser/Thr (also called the Tn‐antigen). A galactose (Gal) monosaccharide might then be linked to the GalNAcα1‐O‐Ser/Thr, consequently generating Galβ3GalNAcα1‐O‐Ser/Thr (Gal‐GalNAc‐O‐Ser/Thr), which is also called core 1 glycan, T‐antigen, or Thomsen–Friedenreich antigen. 96 In normal cells, N‐acetylneuraminic acid, the predominant sialic acid in human and many mammalian cells, is frequently added to cap and mask the GalNAc and Gal‐GalNAc residues. 96 , 97 However, in many carcinomas (such as CRC), truncated O‐GalNAc glycans are formed, and sialic acid is not added to the exposed GalNAc and Gal‐GalNAc. 97 , 98 As a result, high levels of GalNAc (Tn antigen) and Gal‐GalNAc (T antigen) have been detected in colon cancer and additional human tumors including lung, breast and liver carcinoma. 96 , 99 , 100 Such high levels of unmasked Tn‐ and T‐ antigens are associated with tumor invasion and metastasis. 99
In the dental plaque, the coaggregation of F. nucleatum with many gram‐negative species can be inhibited by galactose and GalNAc indicating that F. nucleatum expresses a lectin (previously termed adhesin) that binds these sugar molecules present on the receptor of these coaggregation‐partner bacteria. 75 , 101 Transposon mutagenesis and mutant screening results identified the outer‐membrane Fap2 protein as the fusobacterial lectin that mediates GalNAc‐inhibited coaggregation. 102 Interestingly, in previous studies, Fap2 was found to enable the ability of F. nucleatum to induce apoptosis in lymphocytes. 103 , 104 Therefore, it is plausible that Fap2 mediates the binding of F. nucleatum to lymphocytes, and enable additional fusobacterial factors to induce this apoptosis‐mediated immune evading mechanism.
As Gal‐GalNAc is over‐displayed by colon tumors, it has potential as an oncotarget for fusobacterial Fap2. In agreement with this, the attachment of F. nucleatum to colon cancer cell lines and colon cancer sections correlated with the amounts of Gal‐GalNAc detected on the target cells. In addition, its attachment was reduced upon O‐glycanase treatment and inhibited by soluble GalNAc in a dose‐dependent manner. 85 , 94 Fap2‐inactivated F. nucleatum mutants and clinical F. nucleatum isolates deficient in Fap2 hemagglutination activity exhibited impaired attachment to colon tumor cell lines and clinical specimens. More importantly, IV inoculated Fap2‐deficient F. nucleatum mutants were impaired in colonizing colon cancer mouse models. 85 , 94
7. GAL‐GALNAC IS OVER‐DISPLAYED IN MANY ADENOCARCINOMAS
Evidence suggests that oral F. nucleatum can hematogenously translocate to and specifically colonize colon cancer tumors 85 via recognition and attachment to Gal‐GalNAc (or related sugars), which is highly displayed in colon cancer. 85 , 94 This indicates that F. nucleatum can reach other Gal‐GalNAc–displaying tumors through the same mechanism.
A screen for tumors that display high Gal‐GalNAc levels and might be targeted by fusobacteria was conducted, and Gal‐GalNAc levels of 20 different types of tumors were determined based on fluorescently labeled peanut agglutinin (PNA), a Gal‐GalNAc‐specific lectin. 105 In agreement with previous reports, 99 high Gal‐GalNAc levels were detected in 10 tumors types of epithelial tissues with glandular origin or/and characteristics (Figure 2A). 105 Of which, nine were adenocarcinomas, namely that of the stomach, prostate, ovary, colon, uterus, pancreas, breast, lung, and esophagus. The remaining one was a squamous cell carcinoma of the cervix. In addition, Gal‐GalNAc levels were significantly higher in seven of these adenocarcinomas than in the matched normal control tissues (Figure 2B), whereas those in the stomach, lung, and cervix of the normal control samples were high and similar to those of their respective adenocarcinomas. 105
Concurring with the speculation that fusobacteria can home‐in and accumulate in cancers that display high Gal‐GalNAc levels, fusobacterial DNA levels were reported to be overabundant in the pancreas, 35 , 36 esophagus, 37 gastric, 106 , 107 cervical, 108 and breast 39 adenocarcinomas. Importantly, similar to its prevalence in colorectal cancer, 41 , 109 fusobacterial occurrence in pancreatic tumors was associated with shorter survival. 35 High levels of F. nucleatum nucleic acids in esophageal cancer was also associated with shorter survival 37 and poor response to neoadjuvant chemotherapy. 38
Interestingly, high levels of Gal‐GalNAc are also found in the placenta, 110 , 111 , 112 another extraoral niche, in which F. nucleatum is associated with pathology (Reviewed in this volume by Y. W. Han). Fap2‐inactivated mutants were deficient in placental colonization, 102 suggesting that, Fap2–Gal‐GalNAc interaction might be involved in placental colonization by F. nucleatum, similar to tumor colonization.
8. BREAST CANCER COLONIZATION BY F. NUCLEATUM
Fusobacterium nucleatum is enriched in the breast cancer microbiome, 21 , 39 , 40 which supports the hypothesis that fusobacteria can reach tumors via the circulatory system. A study focusing on breast cancer 40 revealed that Gal‐GalNAc levels increase along with the progression of human breast cancer, similar to colon cancer ie, transition from adenoma to adenocarcinoma. 94 The most dramatic rise in Gal‐GalNAc levels occurs in the transition from hyperplasia to atypical hyperplasia. 40 Breast cancer, which develops in a sequence of events, begins with non‐neoplastic epithelial cells undergoing hyperplasia, atypical hyperplasia, carcinoma in situ, and eventually invasive adenocarcinoma. The conversion from benign hyperplasia to carcinoma in situ (the stage preceding invasive carcinoma) is speculated to occur at the transition from hyperplasia to atypical ductal hyperplasia. 113 Importantly, the presence of F. nucleatum gDNA in breast cancer samples was correlated with high Gal‐GalNAc levels. 40 In mouse models of breast cancer, when fap2‐expressing F. nucleatum ATCC 23726 was intravascularly inoculated, specific colonization of mammary tumors was observed (Figure 3). In contrast, fap2‐inactivated F. nucleatum mutants showed impaired tumor colonization. 40 The inoculation of F. nucleatum into C57BL/6 mice orthotopically implanted with AT3 breast cancer cells resulted in the impaired accumulation of tumor‐infiltrating CD4+ and CD8+ T cells. Tumors obtained from F. nucleatum‐inoculated mice were significantly larger in volume than those from non‐inoculated ones. The progression of lung metastasis was also significantly enhanced in the F. nucleatum ‐ infected group. Fusobacterial‐induced breast tumor growth and metastatic progression in mice were revealed to be Fap2‐dependent and could be prevented by antibiotic treatment, 40 suggesting that targeting F. nucleatum or Fap2 might be beneficial for the treatment of breast cancer. Although these results indicate the existence of F. nucleatum in human breast cancer, the possible role of fusobacteria in human breast cancer development and treatment outcome has not yet been investigated in the clinical setting.
9. TUMOR EXACERBATION BY F. NUCLEATUM
To date, F. nucleatum has been reported as overabundant in colon adenocarcinoma, 34 , 45 esophageal cancer, 37 pancreatic cancer, 35 , 36 and breast cancer. 40 Fusobacterial presence has been associated with poor prognosis in colon, rectal, pancreatic, and esophageal cancers 35 , 37 , 41 , 109 , 114 and with treatment failure in colorectal and esophageal cancers. 38 , 49 In an animal model of colon and breast cancer, F. nucleatum accelerated tumor growth and metastatic progression. 40 , 44 , 45 , 46 Tumor acceleration by F. nucleatum involves the promotion of proliferation, 43 , 44 generation of a pro‐tumorigenic immune microenvironment, 45 and the reduction in the number of tumor‐infiltrating lymphocytes (TILs). 40 , 115 F. nucleatum further inhibits the anti‐tumor activity of some TILs and NK cells that reach the tumor site by activating the human TIGIT checkpoint by utilizing a non‐lectin domain of the fusobacterial Fap2 116 and the human CEACAM1 checkpoint via fusobacterial CbpF. 117 , 118 , 119 In this section, we discuss these various mechanisms of tumor exacerbation induced by F. nucleatum.
9.1. Fusobacterium nucleatum enhances the proliferation of tumor cells
The FadA adhesin of F. nucleatum 12230 was shown to stimulate the proliferation of the human colon cancer cell lines HCT116, DLD1, SW480, and HT29 in a time‐dependent manner. 43 , 44 FadA interaction with E‐cadherin facilitated bacterial adhesion and invasion of E‐cadherin‐expressing cells via clathrin‐mediated endocytosis. Short incubation period of FadAc (the FadA active complex) with HCT116 cells impaired the tumor‐suppressing activity of E‐cadherin, resulting in the decreased phosphorylation of β‐catenin and subsequently increasing its stability and translocation into the nucleus. The nuclear translocation of β‐catenin activates the Wnt pathway and enhances the expression of NF‐κB and the oncogenes Myc and Cyclin D1. In agreement with these in vitro results, significant increases in FadA, Wnt7b (a representative Wnt gene), and NFkB2 expression were detected in human cancerous colon tissues compared with normal ones. 44 Annexin A1 was later revealed as a key component by which F. nucleatum exerts its stimulatory effect on cell proliferation. Downregulation of ANXA1 (Annexin A1 gene) by siRNA effectively reduced F. nucleatum binding and invasion in a similar manner to the suppression of CDH1, which encodes E‐cadherin. 43 These findings are supported by an independent study demonstrating that recombinant FadA promotes the proliferation of SW480 colon cancer cells in a dose‐ and time‐dependent manner. 48
Fusobacterium nucleatum can also enhance the proliferation and invasion of colon cancer cells by upregulating microRNA 21 (miR21). 47 A microRNA screening of four human colorectal cancer cell lines, including HCT116, HT29, LoVo, and SW480, revealed that miR21 is the most upregulated miRNA upon incubation with F. nucleatum. F. nucleatum increases the expression of miR21 by activating the MYD88‐dependent Toll‐like receptor 4 signaling pathway, thus upregulating the nuclear factor‐κB (NF‐κB) signaling pathway. MiR21 decreases the levels of RAS GTPase encoded by RASA1, thus activating the RAS‐mitogen‐activated protein kinase (MAPK) cascade. 120 , 121 Consistently, the inhibition of miR21 suppressed cell proliferation and invasion. Analysis of 90 human‐matched CRC and normal tissues revealed that F. nucleatum DNA and miR21 transcripts were more abundant in cancer tissues than the control and that their levels were significantly higher in more advanced tumors. Importantly, high levels of F. nucleatum DNA and miR21 in tumors correlated with shorter survival. 47
9.2. Fusobacterium nucleatum promotes chemoresistance in CRC
Resistance to chemotherapy is a major cause of tumor recurrence and poor prognosis in patients with CRC. As the abundance of F. nucleatum has been reported in the CRC tissues of post‐chemotherapy recurrence patients compared to non‐recurrence patients, studies have explored whether fusobacteria are involved in chemoresistance. 49
Oxaliplatin and 5‐fluorouracil (5‐FU) are widely used for CRC treatment. 5‐FU inhibits the activity of thymidylate synthase during DNA replication, 122 and oxaliplatin covalently binds DNA and forms platinum‐DNA adducts, resulting in cell‐cycle arrest at G2 phase. 123 Infecting HCT116 and HT29 human colon cancer cell lines with F. nucleatum induced the expression of the LC3‐II marker of autophagosomes, 124 suggesting that fusobacteria might induce colorectal cancer chemotherapeutic response. Moreover, the cytotoxicity of oxaliplatin or 5‐FU treatment on F. nucleatum‐infected colon cancer cells was significantly reduced. Meanwhile, the addition of chloroquine (CQ), an autophagy lysosomal inhibitor, restored drug cytotoxicity. Following F. nucleatum exposure, the expression of miR‐18a and miR‐4802 was the most significantly downregulated among miRNAs in the tumor cells, and their levels inversely correlated with those of the autophagy elements ULK1 and ATG7. The F. nucleatum‐induced reduction in miR‐18a and miR‐4802 levels was dependent on the TLR4/MYD88 signaling pathway. The proposed mechanism speculates that exposure of cancer cells to F. nucleatum activates the TLR4 and MYD88 signaling pathways to downregulate the expression of miR‐18a and miR‐4802, thus inducing a switch from apoptosis to autophagy and drug resistance. 49 , 125
Additional mechanisms by which F. nucleatum regulate apoptosis to induce alterations in chemosensitivity to 5‐FU have also been described. For example, F. nucleatum infection has been reported to upregulate BIRC3 via the TLR4/NF‐kB signaling in HCT116 and HT29 cells. BIRC3, a member of the inhibitor of apoptosis protein (IAP) family, can suppress apoptosis by directly inhibiting the caspase cascade. 126 A SMAC mimetic, a small molecule antagonist of BIRC3, gradually diminished chemoresistance induced by F. nucleatum. In human CRC tissues, high levels of F. nucleatum correlated with high levels of BIRC3. Moreover, high levels of F. nucleatum, TLR4, and BIRC3 were more likely to be detected in CRC patients with recurrence than in those without. 50 In another study, the incubation of HCT116 and HT29 cells with F. nucleatum significantly upregulated the expression of anoctamin‐1 (ANO1), which encodes a human chloride channel protein. ANO1 is located on chromosome 11q13, which is frequently amplified in different types of human carcinomas including head and neck squamous cell carcinoma, bladder cancer and breast cancer. 127 , 128 F. nucleatum‐infected cells treated with oxaliplatin or 5‐FU showed significantly lower levels of apoptosis. Silencing ANO1 blocked the protective effect of F. nucleatum and increased apoptosis, whereas its overexpression further increased F. nucleatum‐induced chemoresistance. 51
Fusobacterium nucleatum‐induced autophagy‐mediated chemoresistance has also been described in esophageal squamous cell carcinoma (ESCC). ESCC patients with high levels of F. nucleatum exhibited higher resistance to chemotherapeutic treatment than patients with lower levels of F. nucleatum. LC3, an autophagy marker, was predominantly detected in F. nucleatum‐treated ESCC cells compared to the control. Furthermore, in TE8 and TE10 human ESCC cells the expression of ATG7, an essential factor for the induction of autophagy, was significantly increased after incubation with F. nucleatum. Upon treatment with docetaxel, cisplatin (CDDP), or 5‐FU, which are key chemotherapeutic agents for ESCC, 129 , 130 F. nucleatum‐infected TE8 and TE10 cells showed significantly higher growth rate than the non‐infected control cells. CQ addition to the infected cells decreased cell growth. In agreement with these in vitro results, a positive correlation between F. nucleatum and the levels of the autophagy markers ATG7 and LC3 was observed in human ESCC tissues. 52
9.3. Fusobacterium nucleatum establishes a tumor‐permissive immune microenvironment
Immune cells and their effectors play critical role in tumor control and progression. The ability of F. nucleatum to manipulate the tumor immune microenvironment was first demonstrated in a C57BL/6 ApcMin/+ mouse model of intestinal tumorigenesis. 45 Adenomatous polyposis coli (Apc) is a tumor suppressor gene and C57BL/6 Apc Min/+ mice spontaneously develop intestinal cancers. Repeated oral inoculations with F. nucleatum but not with Streptococcus sanguinis (control), increased tumor multiplicity in these mice. Tumor promotion by fusobacteria involved the selective recruitment of tumor‐infiltrating myeloid cells, which can promote tumor progression. This was concluded due to the elevated number of infiltrating myeloid‐derived cells, which suppress CD4+ T cells, in the fusobacterial‐infected mice. 45 In addition, the expansion of tumor‐associated neutrophils (TANs), which promote tumor progression and angiogenesis and impair antitumor immunity, and tumor‐associated macrophages (TAMs; both TAMs and M2‐like TAMs), which suppress T cell activity, was elevated in F. nucleatum‐infected mice‐bearing tumors compared to the controls. Analysis of the transcriptome sequencing data revealed that tumors from Apc Min/+ mice exposed to F. nucleatum exhibited a proinflammatory expression signature that is shared with human fusobacteria‐positive colorectal carcinomas. Transcriptomic analysis of human colon tumors with high fusobacterial RNA levels revealed the Fusobacterium‐induced genes, PTGS2 (COX‐2), IL1β, IL6, IL8, and TNF (TNF‐α), indicating an NF‐κB‐driven proinflammatory response associated with colorectal carcinogenesis. 45
9.4. Fusobacterium nucleatum inhibits the recruitment of anti‐cancer tumor‐infiltrating T cells
Accumulated evidence indicates that tumor‐colonized F. nucleatum can also interfere with the recruitment of TILs. In colorectal carcinoma tissues, the abundance of F. nucleatum was inversely correlated with T‐cell density. 115 , 131 , 132 In post‐neoadjuvant locally treated advanced rectal cancer, fusobacterial persistence was associated with a lack of CD8+ T cells. 109
In an AT3 orthotropic mouse model of breast cancer, F. nucleatum accelerated cancer progression by inhibiting the recruitment of TILs. C57BL/6 mice implanted with AT3 cells and IV‐inoculated with F. nucleatum showed significantly larger tumors and more lung metastasis than noninfected mice. Metronidazole treatment diminished the pro‐tumorigenic effects of the bacteria. Bacterial‐induced tumor enlargement was attributed to the inhibition of T cell recruitment into the tumor site as evidenced by the fewer number of CD4+ and CD8+ T cells detected in the tumors of F. nucleatum‐infected mice. Similarly, fusobacteria did not induce tumor enlargement when AT3 cells were implanted in SCID beige mice lacking T, B, and NK cells. 40 Thus, these findings indicate that in immunocompetent C57BL/6 mice, the growth of AT3 breast tumor is restricted by NK, B, or T cells. However, in the presence of F. nucleatum, T cell levels were reduced, resulting in increased tumor growth. The reduction in the number of immune cells may involve apoptosis. Apoptosis was induced by F. nucleatum in lymphocytes via Fap2. 103 Importantly, the immunomodulated pro‐tumorigenic effect of F. nucleatum is expected to be more significant in humans because the activity of NK and some T cells in tumors can be further weakened by the inhibitory interactions between Fap2 and TIGIT 116 and between CbpF and CEACAM 117 checkpoints (as discussed below).
9.5. Fusobacterium nucleatum activates immune checkpoints
While the presence of F. nucleatum in human colorectal cancer 115 , 131 , 132 and in a mouse model of breast cancer 40 has been associated with decreased number of TILs in the tumor site, the effect of fusobacteria on the recruitment of NK cells to tumors has not yet been reported. Remarkably, the tumor‐killing effect of NK cells on various tumor cell lines was inhibited by the presence of various F. nucleatum strains. 116 To prevent autoimmune reactions and the killing of normal cells, the activity of immune cells can be negatively regulated by a large repertoire of inhibitory receptors, one of which includes TIGIT, an inhibitory receptor expressed by many immune cells, including NK cells. Tumor‐attached F. nucleatum inhibited immune cell activity via the interaction between the fusobacterial Fap2 protein and the human TIGIT inhibitory receptor. 116 More recently, the suppression of immune cell anti‐tumor activity by F. nucleatum through the activation of an additional immune cell suppressing receptor CEAMAM1, was reported. 117 , 119 Thus, in addition to reducing the number of immune cells infiltrating the fusobacterial‐colonized tumor microenvironment, fusobacteria can further protect tumors by activating checkpoints to suppress immune‐cell anti‐tumor activity.
9.6. Fusobacterium nucleatum promotes metastasis
Fusobacterium nucleatum has been detected in CRC metastases to the liver and lymph nodes 33 , 34 , 46 , 94 and is associated with increased number of liver metastases in colorectal cancer. 46 , 133 In a mouse model of breast cancer, F. nucleatum promoted lung metastasis. 40 The presence of F. nucleatum was also shown to promote the successful establishment of CRC patient‐derived xenografts in mice. 46 The proposed mechanism by which F. nucleatum promotes metastasis involves the induction of proinflammatory cytokines that stimulate tumor cell migration and invasion. F. nucleatum‐infected CRC cells secrete cytokines IL‐8 and CXCL1, which promote the invasive motility of infected and non‐infected cells. 134 Upon incubation with F. nucleatum, human and mouse breast cancer cells also induced the overexpression and increased secretion of the matrix metalloproteinase 9 (MMP‐9). 40 Proteases of the MMP family play vital roles in many biological processes that involve matrix remodeling. In particular, MMP‐9 activity has been related to cancer pathology, including invasion, angiogenesis, and metastasis. 135 Therefore, in addition to immune modulation, which is the putative major mechanism of F. nucleatum action in AT3 breast cancer model in C57BL/6 mice, the induction of MMP might be another mechanism by which F. nucleatum accelerates breast tumor progression.
Generally, metastasis is responsible for more than 90% of cancer‐associated mortality and is the main cause of breast cancer‐related deaths. Patients with localized breast cancer have a 5‐year survival rate of 98%, which dramatically decreases to 26% in patients with metastatic breast cancer. 136 More studies are required to completely understand the pro‐metastasis mechanisms of F. nucleatum.
10. FUSOBACTERIUM NUCLEATUM AS A POTENTIAL DIAGNOSTIC BIOMARKER
Microbiome‐based oncology diagnostics are promising novel approaches for tumor detection. A recent report demonstrated the potential of plasma‐derived, cell‐free microbial nucleic acids for tumor screening. Good discrimination was achieved between samples from donors with tumors and those from healthy ones and among 32 different cancer types. 137 Therefore, the overabundance of F. nucleatum in tumors can be utilized as a strategy for tumor detection. Although a number of approaches have been explored, adequate screening capabilities have not yet been achieved.
10.1. Stool screening for CRC detection
The early detection of cancers is important to reduce CRC mortality. 138 Fecal occult blood testing (FOBT) is a common non‐invasive cost‐efficient method to screen for CRC 138 ; However, FOBT has moderate sensitivity. 138 , 139 , 140
Almost a decade ago, F. nucleatum was reported to be enriched in stool samples from colorectal adenoma and carcinoma patients compared to healthy subjects. 45 Many reports have since corroborated this finding, particularly those involving Asian cohorts. 141 A recent review and meta‐analysis demonstrated the potential of a fecal F. nucleatum ‐based test for detecting colorectal cancer; however, additional clinical trials should be performed to verify this. 141
The combination of fecal quantification of F. nucleatum and FOBT was shown to increase the specificity and sensitivity of the latter, 142 , 143 indicating the applicability of this combination method as a large population‐based screening strategy employing large non‐invasive samples for colorectal cancer. To date, the quantification of F. nucleatum has been performed using quantitative PCR. 141 It is expected that future developments of novel antibody‐ or enzymatic‐based assays might enable the combination of FOBT with fecal fusobacterial testing (FFT) in a single test.
10.2. Tumor detection based on antibody responses
Immune assays based on the serum, salivary, or fecal anti‐ F. nucleatum antibodies may also offer new opportunities for CRC screening. Thus far, serum anti‐ F. nucleatum antibodies could not discriminate between CRC patients and the controls with sufficient specificity and sensitivity. 144 , 145 , 146 One study used multiplex serology assay to simultaneously measure antibody responses to 11 F. nucleatum recombinant antigens in prediagnostic serum samples from colorectal cancer patients and matched controls (n = 485 each). However, colorectal cancer risk was not significantly associated with antibody response to each F. nucleatum protein or combined positivity to any of the 11 proteins. 145 In a subsequent study, ELISA‐based testing found that the levels of F. nucleatum IgA and IgG antibodies in the CRC group were higher than those in the healthy controls. However, the discriminative ability of the ELISA test was not adequate for diagnosis. 146 Notably, plasma anti‐ F. nucleatum IgG level and salivary IgA level against F. nucleatum and specifically against Fap2, has been recently reported to be associated with pancreatic malignancy. 147 However, the diagnostic potential of these findings should be confirmed by future studies.
11. ANTI‐TUMOR THERAPEUTIC STRATEGIES EMPLOYING F. NUCLEATUM
11.1. Elimination of tumor‐colonized F. nucleatum
As mentioned above (section 9), high fusobacterium load in tumors has been associated with poor disease outcomes in humans. 35 , 37 , 38 , 41 , 42 , 49 , 51 , 52 In animal models, systemic antibiotic treatment eliminated tumor‐colonized fusobacteria and subsequently suppressed fusobacterial‐induced tumor exacerbation, suggesting the effectivity of antibiotic treatment for cancer patients. 40 , 46 Unfortunately, in some cases, antibiotics might interfere with anti‐tumor treatment. Gut microbiota can influence anti‐tumor chemotherapy, 148 , 149 immunotherapy, 150 , 151 , 152 , 153 , 154 , 155 , 156 radiotherapy, 157 and allogeneic bone marrow transplantation 158 via various proposed mechanisms. 23 Fecal transplantation to restore the gut microbiota following antibiotic treatment might address this issue, especially if in the future, fecal transplant will be considered to aid anti‐cancer (chemotherapeutic, immunotherapeutic) treatments. 25 Bacteriophages are viruses that prey and replicate in bacteria. The use of bacteriophages for targeting specific oncobacteria, including tumor‐colonized F. nucleatum, has been recently suggested. 25 Importantly, a fusobacteria bacteriophage with a potential to eradicate tumor‐colonized F. nucleatum has been recently identified. 159
11.2. Tumor targeting strategies using F. nucleatum and Fap2
Due to their specific homing to glycan‐overdisplaying tumors, F. nucleatum or Fap2 could potentially be used as a platform for targeting tumors and metastases that display high levels of Gal‐GalNAc (or related sugars). Recent advances in the genetic manipulation of F. nucleatum 134 , 160 have facilitated the ability to weaken fusobacterial tumor‐enhancing actions in the future by for example mutating FadA and/or nullifying TIGIT and CEACAM1 activation. Such enfeebled strains can then be engineered to express anti‐cancer payloads. Possible anti‐tumor agents might include antigens that induce trained innate immunity, or antigens that induce innate and adaptive anti‐tumor immune responses, and/or enzymes that locally convert a nontoxic prodrug to a cytolytic drug. Such strategies are currently being tested with several tumor‐colonizing bacteria including Salmonella and Listeria (reviewed in 5 ).
Importantly, live bacteria are currently used for cancer treatment. 161 In case of adverse effects, this treatment can be terminated using antibiotics. For over three decades, the intravesical administration of live bacillus Calmette–Guérin, a vaccine against tuberculosis, has been used to treat bladder cancer. 161 Anecdotally, bladder cancer patients treated with BCG have significantly reduced risk of Alzheimer's disease and Parkinson's disease compared to those not treated with BCG. The beneficial effect of BCG on neurodegenerative diseases has been attributed to the possible activation of long‐term nonspecific immune effects. 162
A more advanced version of this tumor‐targeting approach might be targeting tumor‐colonized fusobacteria with bacteriophages engineered to express anti‐cancer payloads such as described above. A phage‐guided encapsulation of the anti‐tumor drug irinotecan dextran nanoparticles has been recently proposed to promote the growth of tumor‐suppressing Clostridium butyricum. The engineered nanocapsules were covalently bound to a phage that target the tumor‐colonized fusobacteria. The capacity of the phage‐guided nanoparticles to control tumor growth was then demonstrated in two mouse models of colon cancer. 163
Similar to F. nucleatum, Plasmodium falciparum, the causal agent of malaria, is found in both the placenta and tumors. In the analogues of Fap2, VAR2CSA is the malaria protein speculated to be responsible for the accumulation of malaria‐infected erythrocytes to the placenta and tumors. During pregnancy‐associated malaria, malarial parasites express VAR2CSA proteins on the surface of infected erythrocytes. VAR2CSA enables the specific anchoring of the infected erythrocytes to the syncytiotrophoblast in the placenta by binding to chondroitin sulfate. Similar to the Fap2 oncofetal ligand Gal‐GalNAc, chondroitin sulfate is an oncofetal antigen shared between placental trophoblasts and cancer cells. 164 , 165
Recombinant VAR2CSA (rVAR2) coupled to magnetic beads can capture circulating tumor cells in a blood sample, thus serving as a potential tool for novel cancer diagnostics. 166 The conjugation of a toxin to rVAR2 can also direct anti‐tumor therapeutics. 165 , 167 The parallel roles played by VAR2CSA–chondroitin sulfate and Fap2–Gal‐GalNAc interactions are interesting and require further investigation. The complementary utilization of Fap2 for tumor detection and treatment should also be explored.
12. CONCLUDING REMARKS
The terms alpha‐bugs 168 also referred to as bacterial drivers 19 have been proposed to describe certain members of the microbiome that possess direct pro‐oncogenic features or the ability to shift the local bacterial community to one that promotes mucosal immune responses and epithelial cell changes, consequently resulting in the development of colorectal cancer. Alpha‐bugs have been also suggested to enhance carcinogenesis by selectively “crowding out” cancer‐protective microbial species. 168 “Classical” bacterial drivers possess virulence factors that might initiate cancer formation. These factors include the colibactin genotoxin of several E. coli strains that can induce single‐strand DNA breaks 169 and the B. fragilis toxin fragilysin (BFT). BFT, a metalloproteinase, is genotoxic to colonic epithelial cells, upregulates spermine oxidase, a polyamine catabolic enzyme that contributes to increased production of reactive oxygen species and DNA damage. 170 Fragilysin also promotes the proliferation of intestinal epithelial cells in a mechanism involving cleavage of the tumor suppressor protein E‐cadherin. 171 , 172
Currently, H. pylori is the only bacterium that is classified as a direct carcinogen. Epidemiological evidence and experimental data indicate that prevalence of H. pylori is associated with the development of gastric adenocarcinoma and gastric mucosa‐associated lymphoid tissue (MALT) lymphoma. 173 H. pylori in the stomach mucosa is crucial in the chronic inflammatory process, which leads to gastric cancer development. 173 Thus, the cytotoxin‐associated gene A (CagA) protein of H. pylori, which is delivered to gastric epithelial cells via bacterial type IV‐secretion, is an oncoprotein that can induce malignant neoplasms in mammals. 174 , 175
Unlike the cancer drivers mentioned above, based on the current evidence, F. nucleatum is a “passenger” 19 bacteria that colonizes an already formed tumor and accelerates its progression through manipulation of β‐catenin signaling, 43 , 44 host cytokine production (IL‐8 and CXCL1), 134 anti‐tumor immunity, and chemoresistance. These mechanisms are illustrated in Figure 4.
Occurrence of F. nucleatum is found to be associated with poor disease outcome in an increasing number of tumor types suggesting that targeting intratumor fusobacteria will improve prognosis.
High Gal‐GalNAc level is found in all tumor‐types colonized by fusobacteria indicating that it is an oncoantigen that plays a role in the specificity of tumor colonization by fusobacteria by serving as a ligand to Fap2. It is therefore tempting to assume that fusobacterial overabundance will be found in all Gal‐GalNAc overdisplaying tumors. Due to the tumor specificity, fusobacteria and Fap2 hold potential for use for tumor screening and treatment.
The fusobacterial adhesin FadA binds to E‐cadherin and activates the β‐catenin/WNT signaling pathway, thus promoting cell proliferation. 43
The bacterial endotoxin lipopolysaccharide (LPS) activates the Toll‐like receptor 4 (TLR4) to trigger the upregulation of miR21. This decreases the levels of RAS GTPase RASA1 and activates the RAS–mitogen‐activated protein kinase (MAPK) cascade to enhance cell proliferation. 120 , 121
Fusobacterium nucleatum LPS interactions with TLR4 can also upregulate BIRC3, which inhibits apoptosis by directly inhibiting the caspase cascade, thereby increasing cell resistance against cytotoxic drugs. 50 In addition, LPS/TLR4 interactions downregulate the expression of miR18a and miR4802, which is associated with that of autophagy elements ULK1 and ATG7, resulting in increased autophagy and subsequently enhancing cell resistance to therapy. 49 , 125
Lastly, F. nucleatum inhibits apoptosis by upregulating the expression anoctamin‐1 (ANO1) in a TLR4‐dependent manner to contribute to chemoresistance. 51
The non‐lectin domain of Fap2 inhibits the anti‐tumor activity of TILs and NK cells at the tumor site by activating the human TIGIT checkpoint. 116
Fusobacterial CbpF further suppresses the anti‐tumor activity of TILs and NK cells by activating the human CEACAM1 checkpoint. 117 , 118
ACKNOWLEDGEMENTS
This work was supported by the Israel Cancer Research Fund Project grant (GB), the Israel Science Foundation Moked grant and the Israel Ministry of Science and Technology Personalized Medicine grant (GB and OM). TAM is a fellow of the AdR Women Doctoral Program. Figures were created using BioRender.com.
Alon‐Maimon T, Mandelboim O, Bachrach G. Fusobacterium nucleatum and cancer. Periodontol 2000. 2022;98:166–180. doi: 10.1111/prd.12426
Alon‐Maimon, Mandelboim and Bachrach contributed equally to this work.
Contributor Information
Ofer Mandelboim, Email: oferm@ekmd.huji.ac.il.
Gilad Bachrach, Email: giladba@ekmd.huji.ac.il.
REFERENCES
- 1. Rous P. A sarcoma of the fowl transmissible by an agent separable from the tumor cells. J Exp Med. 1911;13:397‐411. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Epstein MA, Achong BG, Barr YM. Virus particles in cultured lymphoblasts from Burkitt's lymphoma. Lancet. 1964;1:702‐703. [DOI] [PubMed] [Google Scholar]
- 3. Zapatka M, Borozan I, Brewer DS, et al. The landscape of viral associations in human cancers. Nat Genet. 2020;52:320‐330. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4. Loughlin KR, William B. Coley: his hypothesis, his toxin, and the birth of immunotherapy. Urol Clin North Am. 2020;47:413‐417. [DOI] [PubMed] [Google Scholar]
- 5. Zhou S, Gravekamp C, Bermudes D, Liu K. Tumour‐targeting bacteria engineered to fight cancer. Nat Rev Cancer. 2018;18:727‐743. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6. Starnes CO. Coley's toxins in perspective. Nature. 1992;357:11‐12. [DOI] [PubMed] [Google Scholar]
- 7. Sepich‐Poore GD, Zitvogel L, Straussman R, Hasty J, Wargo JA, Knight R. The microbiome and human cancer. Science. 2021;371. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8. Lenis AT, Lec PM, Chamie K, Mshs MD. Bladder cancer: a review. JAMA. 2020;324:1980‐1991. [DOI] [PubMed] [Google Scholar]
- 9. Pettenati C, Ingersoll MA. Mechanisms of BCG immunotherapy and its outlook for bladder cancer. Nat Rev Urol. 2018;15:615‐625. [DOI] [PubMed] [Google Scholar]
- 10. Kleinnijenhuis J, Quintin J, Preijers F, et al. BCG‐induced trained immunity in NK cells: role for non‐specific protection to infection. Clin Immunol. 2014;155:213‐219. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11. Chavakis T, Mitroulis I, Hajishengallis G. Hematopoietic progenitor cells as integrative hubs for adaptation to and fine‐tuning of inflammation. Nat Immunol. 2019;20:802‐811. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12. Brandau S, Riemensberger J, Jacobsen M, et al. NK cells are essential for effective BCG immunotherapy. Int J Cancer. 2001;92:697‐702. [DOI] [PubMed] [Google Scholar]
- 13. Kalafati L, Kourtzelis I, Schulte‐Schrepping J, et al. Innate immune training of granulopoiesis promotes anti‐tumor activity. Cell. 2020;183(3):771‐785.e12. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14. van Puffelen JH, Keating ST, Oosterwijk E, et al. Trained immunity as a molecular mechanism for BCG immunotherapy in bladder cancer. Nat Rev Urol. 2020;17:513‐525. [DOI] [PubMed] [Google Scholar]
- 15. Parsonnet J, Friedman GD, Vandersteen DP, et al. Helicobacter pylori infection and the risk of gastric carcinoma. N Engl J Med. 1991;325:1127‐1131. [DOI] [PubMed] [Google Scholar]
- 16. Uemura N, Okamoto S, Yamamoto S, et al. Helicobacter pylori infection and the development of gastric cancer. N Engl J Med. 2001;345:784‐789. [DOI] [PubMed] [Google Scholar]
- 17. Amieva M, Peek RM Jr. Pathobiology of Helicobacter pylori‐induced gastric cancer. Gastroenterology. 2016;150:64‐78. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18. Scott AJ, Alexander JL, Merrifield CA, et al. International Cancer Microbiome Consortium consensus statement on the role of the human microbiome in carcinogenesis. Gut. 2019;68:1624‐1632. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19. Tjalsma H, Boleij A, Marchesi JR, Dutilh BE. A bacterial driver‐passenger model for colorectal cancer: beyond the usual suspects. Nat Rev Microbiol. 2012;10:575‐582. [DOI] [PubMed] [Google Scholar]
- 20. Jin C, Lagoudas GK, Zhao C, et al. Commensal microbiota promote lung cancer development via gammadelta T cells. Cell. 2019;176:998‐1013.e1016. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21. Nejman D, Livyatan I, Fuks G, et al. The human tumor microbiome is composed of tumor type‐specific intracellular bacteria. Science. 2020;368:973‐980. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22. Livyatan I, Nejman D, Shental N, Straussman R. Characterization of the human tumor microbiome reveals tumor‐type specific intra‐cellular bacteria. Oncoimmunology. 2020;9:1800957. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23. Helmink BA, Khan MAW, Hermann A, Gopalakrishnan V, Wargo JA. The microbiome, cancer, and cancer therapy. Nat Med. 2019;25:377‐388. [DOI] [PubMed] [Google Scholar]
- 24. Neville BA, Forster SC, Lawley TD. Commensal Koch's postulates: establishing causation in human microbiota research. Curr Opin Microbiol. 2018;42:47‐52. [DOI] [PubMed] [Google Scholar]
- 25. Kabwe M, Dashper S, Bachrach G, Tucci J. Bacteriophage manipulation of the microbiome associated with tumour microenvironments‐can this improve cancer therapeutic response? FEMS Microbiol Rev. 2021;45(5). doi: 10.1093/femsre/fuab017 [DOI] [PubMed] [Google Scholar]
- 26. Mc CW, Mason JM 3rd. Enterococcal endocarditis associated with carcinoma of the sigmoid; report of a case. J Med Assoc State Ala. 1951;21:162‐166. [PubMed] [Google Scholar]
- 27. zur Hausen H. The search for infectious causes of human cancers: where and why (Nobel lecture). Angew Chem Int Ed Engl. 2009;48:5798‐5808. [DOI] [PubMed] [Google Scholar]
- 28. de Martel C, Ferlay J, Franceschi S, et al. Global burden of cancers attributable to infections in 2008: a review and synthetic analysis. Lancet Oncol. 2012;13:607‐615. [DOI] [PubMed] [Google Scholar]
- 29. Plummer M, de Martel C, Vignat J, Ferlay J, Bray F, Franceschi S. Global burden of cancers attributable to infections in 2012: a synthetic analysis. Lancet Glob Health. 2016;4:e609‐616. [DOI] [PubMed] [Google Scholar]
- 30. Whitmore SE, Lamont RJ. Oral bacteria and cancer. PLoS Pathog. 2014;10:e1003933. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 31. Fitzsimonds ZR, Rodriguez‐Hernandez CJ, Bagaitkar J, Lamont RJ. From beyond the pale to the pale riders: the emerging association of bacteria with oral cancer. J Dent Res. 2020;99:604‐612. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 32. Hajishengallis G, Chavakis T. Local and systemic mechanisms linking periodontal disease and inflammatory comorbidities. Nat Rev Immunol. 2021;21(7):426‐440. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33. Kostic AD, Gevers D, Pedamallu CS, et al. Genomic analysis identifies association of Fusobacterium with colorectal carcinoma. Genome Res. 2012;22:292‐298. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 34. Castellarin M, Warren RL, Freeman JD, et al. Fusobacterium nucleatum infection is prevalent in human colorectal carcinoma. Genome Res. 2012;22:299‐306. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 35. Mitsuhashi K, Nosho K, Sukawa Y, et al. Association of Fusobacterium species in pancreatic cancer tissues with molecular features and prognosis. Oncotarget. 2015;6:7209‐7220. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 36. Gaiser RA, Halimi A, Alkharaan H, et al. Enrichment of oral microbiota in early cystic precursors to invasive pancreatic cancer. Gut. 2019;68:2186‐2194. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 37. Yamamura K, Baba Y, Nakagawa S, et al. Human microbiome Fusobacterium nucleatum in esophageal cancer tissue is associated with prognosis. Clin Cancer Res. 2016;22:5574‐5581. [DOI] [PubMed] [Google Scholar]
- 38. Yamamura K, Izumi D, Kandimalla R, et al. Intratumoral Fusobacterium nucleatum levels predict therapeutic response to neoadjuvant chemotherapy in esophageal squamous cell carcinoma. Clin Cancer Res. 2019;25:6170‐6179. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 39. Hieken TJ, Chen J, Hoskin TL, et al. The microbiome of aseptically collected human breast tissue in benign and malignant disease. Sci Rep. 2016;6:30751. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 40. Parhi L, Alon‐Maimon T, Sol A, et al. Breast cancer colonization by Fusobacterium nucleatum accelerates tumor growth and metastatic progression. Nat Commun. 2020;11:3259. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 41. Mima K, Nishihara R, Qian ZR, et al. Fusobacterium nucleatum in colorectal carcinoma tissue and patient prognosis. Gut. 2016;65:1973‐1980. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 42. Gethings‐Behncke C, Coleman HG, Jordao HWT, et al. Fusobacterium nucleatum in the colorectum and its association with cancer risk and survival: a systematic review and meta‐analysis. Cancer Epidemiol Biomarkers Prev. 2020;29:539‐548. [DOI] [PubMed] [Google Scholar]
- 43. Rubinstein MR, Baik JE, Lagana SM, et al. Fusobacterium nucleatum promotes colorectal cancer by inducing Wnt/beta‐catenin modulator Annexin A1. EMBO Rep. 2019;20. doi: 10.15252/embr.201847638 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 44. Rubinstein MR, Wang X, Liu W, Hao Y, Cai G, Han YW Fusobacterium nucleatum promotes colorectal carcinogenesis by modulating E‐Cadherin/β‐Catenin signaling via its FadA adhesin. Cell Host Microbe. 2013;14:195‐206. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 45. Kostic AD, Chun E, Robertson L, et al. Fusobacterium nucleatum potentiates intestinal tumorigenesis and modulates the tumor‐immune microenvironment. Cell Host Microbe. 2013;14:207‐215. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 46. Bullman S, Pedamallu CS, Sicinska E, et al. Analysis of Fusobacterium persistence and antibiotic response in colorectal cancer. Science. 2017;358:1443‐1448. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 47. Yang Y, Weng W, Peng J, et al. Fusobacterium nucleatum increases proliferation of colorectal cancer cells and tumor development in mice by activating toll‐like receptor 4 signaling to nuclear factor‐kappaB, and up‐regulating expression of MicroRNA‐21. Gastroenterology. 2017;152:851‐866. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 48. Dadashi M, Hajikhani B, Faghihloo E, et al. Proliferative effect of FadA recombinant protein from Fusobacterium nucleatum on SW480 colorectal cancer cell line. Infect Disord Drug Targets. 2021;21(4):623‐628. [DOI] [PubMed] [Google Scholar]
- 49. Yu T, Guo F, Yu Y, et al. Fusobacterium nucleatum promotes chemoresistance to colorectal cancer by modulating autophagy. Cell. 2017;170(3):548‐563.e16. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 50. Zhang S, Yang Y, Weng W, et al. Fusobacterium nucleatum promotes chemoresistance to 5‐fluorouracil by upregulation of BIRC3 expression in colorectal cancer. J Exp Clin Cancer Res. 2019;38:14. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 51. Lu P, Xu M, Xiong Z, Zhou F, Wang L Fusobacterium nucleatum prevents apoptosis in colorectal cancer cells via the ANO1 pathway. Cancer Manag Res. 2019;11:9057‐9066. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 52. Liu Y, Baba Y, Ishimoto T, et al. Fusobacterium nucleatum confers chemoresistance by modulating autophagy in oesophageal squamous cell carcinoma. Br J Cancer. 2021;124(5):963‐974. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 53. Han YW Fusobacterium nucleatum: a commensal‐turned pathogen. Curr Opin Microbiol. 2015;23:141‐147. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 54. Brennan CA, Garrett WS. Gut microbiota, inflammation, and colorectal cancer. Annu Rev Microbiol. 2016;70:395‐411. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 55. Brennan CA, Garrett WS Fusobacterium nucleatum ‐ symbiont, opportunist and oncobacterium. Nat Rev Microbiol. 2019;17(3):156‐166. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 56. Fujiwara N, Kitamura N, Yoshida K, Yamamoto T, Ozaki K, Kudo Y. Involvement of Fusobacterium species in oral cancer progression: a literature review including other types of cancer. Int J Mol Sci. 2020;21(17):6207. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 57. Hashemi Goradel N, Heidarzadeh S, Jahangiri S, et al. Fusobacterium nucleatum and colorectal cancer: a mechanistic overview. J Cell Physiol. 2019;234:2337‐2344. [DOI] [PubMed] [Google Scholar]
- 58. Lee SA, Liu F, Riordan SM, Lee CS, Zhang L. Global investigations of Fusobacterium nucleatum in human colorectal cancer. Front Oncol. 2019;9:566. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 59. Liu Y, Baba Y, Ishimoto T, et al. Progress in characterizing the linkage between Fusobacterium nucleatum and gastrointestinal cancer. J Gastroenterol. 2019;54:33‐41. [DOI] [PubMed] [Google Scholar]
- 60. Luo K, Zhang Y, Xv C, et al. Fusobacterium nucleatum, the communication with colorectal cancer. Biomed Pharmacother. 2019;116:108988. [DOI] [PubMed] [Google Scholar]
- 61. Nosho K, Sukawa Y, Adachi Y, et al. Association of Fusobacterium nucleatum with immunity and molecular alterations in colorectal cancer. World J Gastroenterol. 2016;22:557‐566. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 62. Shang FM, Liu HL Fusobacterium nucleatum and colorectal cancer: a review. World J Gastrointest Oncol. 2018;10:71‐81. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 63. Surlin P, Nicolae FM, Surlin VM, et al. Could periodontal disease through periopathogen Fusobacterium nucleatum be an aggravating factor for gastric cancer? J Clin Med. 2020;9(12):3885. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 64. Wu J, Li Q, Fu X Fusobacterium nucleatum contributes to the carcinogenesis of colorectal cancer by inducing inflammation and suppressing host immunity. Transl Oncol. 2019;12:846‐851. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 65. Yang Z, Ji G Fusobacterium nucleatum‐positive colorectal cancer. Oncol Lett. 2019;18:975‐982. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 66. Zhang S, Cai S, Ma Y. Association between Fusobacterium nucleatum and colorectal cancer: progress and future directions. J Cancer. 2018;9:1652‐1659. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 67. van der Merwe M, Van Niekerk G, Botha A, Engelbrecht AM. The onco‐immunological implications of F nucleatum in breast cancer. Immunol Lett. 2021;232:60‐66. [DOI] [PubMed] [Google Scholar]
- 68. Socransky SS, Haffajee AD, Cugini MA, Smith C, Kent RL Jr. Microbial complexes in subgingival plaque. J Clin Periodontol. 1998;25:134‐144. [DOI] [PubMed] [Google Scholar]
- 69. Nozawa A, Oshima H, Togawa N, Nozaki T, Murakami S. Development of Oral Care Chip, a novel device for quantitative detection of the oral microbiota associated with periodontal disease. PLoS One. 2020;15:e0229485. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 70. Hajishengallis G, Liang S, Payne MA, et al. Low‐abundance biofilm species orchestrates inflammatory periodontal disease through the commensal microbiota and complement. Cell Host Microbe. 2011;10:497‐506. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 71. Hajishengallis G, Lamont RJ. Dancing with the stars: how choreographed bacterial interactions dictate nososymbiocity and give rise to keystone pathogens, accessory pathogens, and pathobionts. Trends Microbiol. 2016;24:477‐489. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 72. Lamont RJ, Koo H, Hajishengallis G. The oral microbiota: dynamic communities and host interactions. Nat Rev Microbiol. 2018;16:745‐759. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 73. Tanner AC, Paster BJ, Lu SC, et al. Subgingival and tongue microbiota during early periodontitis. J Dent Res. 2006;85:318‐323. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 74. Matsui M, Chosa N, Shimoyama Y, Minami K, Kimura S, Kishi M. Effects of tongue cleaning on bacterial flora in tongue coating and dental plaque: a crossover study. BMC Oral Health. 2014;14:4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 75. Kolenbrander PE, London J. Adhere today, here tomorrow: oral bacterial adherence. J Bacteriol. 1993;175:3247‐3252. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 76. Kolenbrander PE, Palmer RJ Jr, Periasamy S, Jakubovics NS. Oral multispecies biofilm development and the key role of cell‐cell distance. Nat Rev Microbiol. 2010;8:471‐480. [DOI] [PubMed] [Google Scholar]
- 77. Kolenbrander PE, Palmer RJ Jr, Rickard AH, Jakubovics NS, Chalmers NI, Diaz PI. Bacterial interactions and successions during plaque development. Periodontol. 2000;2006(42):47‐79. [DOI] [PubMed] [Google Scholar]
- 78. Kaplan CW, Lux R, Haake SK, Shi W. The Fusobacterium nucleatum outer membrane protein RadD is an arginine‐inhibitable adhesin required for inter‐species adherence and the structured architecture of multispecies biofilm. Mol Microbiol. 2009;71:35‐47. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 79. Mark Welch JL, Rossetti BJ, Rieken CW, Dewhirst FE, Borisy GG. Biogeography of a human oral microbiome at the micron scale. Proc Natl Acad Sci USA. 2016;113:E791‐800. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 80. Siegel RL, Miller KD, Goding Sauer A, et al. Colorectal cancer statistics, 2020. CA Cancer J Clin. 2020;70:145‐164. [DOI] [PubMed] [Google Scholar]
- 81. Arnold M, Sierra MS, Laversanne M, Soerjomataram I, Jemal A, Bray F. Global patterns and trends in colorectal cancer incidence and mortality. Gut. 2017;66:683‐691. [DOI] [PubMed] [Google Scholar]
- 82. Strauss J, Kaplan GG, Beck PL, et al. Invasive potential of gut mucosa‐derived fusobacterium nucleatum positively correlates with IBD status of the host. Inflamm Bowel Dis. 2011;17:1971‐1978. [DOI] [PubMed] [Google Scholar]
- 83. Consortium, T.H.M.P. Structure, function and diversity of the healthy human microbiome. Nature. 2012;486:207‐214. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 84. Komiya Y, Shimomura Y, Higurashi T, et al. Patients with colorectal cancer have identical strains of Fusobacterium nucleatum in their colorectal cancer and oral cavity. Gut. 2019;68:1335‐1337. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 85. Abed J, Maalouf N, Manson AL, et al. Colon cancer‐associated Fusobacterium nucleatum may originate from the oral cavity and reach colon tumors via the circulatory system. Front Cell Infect Microbiol. 2020;10:400. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 86. Mima K, Cao Y, Chan AT, et al. Fusobacterium nucleatum in colorectal carcinoma tissue according to tumor location. Clin Transl Gastroenterol. 2016;7:e200. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 87. Janati AI, Karp I, Laprise C, Sabri H, Emami E. Detection of Fusobaterium nucleatum in feces and colorectal mucosa as a risk factor for colorectal cancer: a systematic review and meta‐analysis. Syst Rev. 2020;9:276. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 88. Kremer BH, van Steenbergen TJ Peptostreptococcus micros coaggregates with Fusobacterium nucleatum and non‐encapsulated Porphyromonas gingivalis . FEMS Microbiol Lett. 2000;182:57‐62. [DOI] [PubMed] [Google Scholar]
- 89. Warren RL, Freeman DJ, Pleasance S, et al. Co‐occurrence of anaerobic bacteria in colorectal carcinomas. Microbiome. 2013;1:16. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 90. Komiya Y, Shimomura Y, Higurashi T, et al. Patients with colorectal cancer have identical strains of Fusobacterium nucleatum in their colorectal cancer and oral cavity. Gut. 2018;68:1335‐1337. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 91. Ashare A, Stanford C, Hancock P, et al. Chronic liver disease impairs bacterial clearance in a human model of induced bacteremia. Clin Transl Sci. 2009;2:199‐205. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 92. Han YW, Redline RW, Li M, Yin L, Hill GB, McCormick TS Fusobacterium nucleatum induces premature and term stillbirths in pregnant mice: implication of oral bacteria in preterm birth. Infect Immun. 2004;72:2272‐2279. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 93. Wilson W, Taubert KA, Gewitz M, et al. Prevention of infective endocarditis: guidelines from the American Heart Association: a guideline from the American Heart Association Rheumatic Fever, Endocarditis and Kawasaki Disease Committee, Council on Cardiovascular Disease in the Young, and the Council on Clinical Cardiology, Council on Cardiovascular Surgery and Anesthesia, and the Quality of Care and Outcomes Research Interdisciplinary Working Group. J Am Dent Assoc. 2008;139(Suppl):3S‐24S. [DOI] [PubMed] [Google Scholar]
- 94. Abed J, Emgard JE, Zamir G, et al. Fap2 mediates Fusobacterium nucleatum colorectal adenocarcinoma enrichment by binding to tumor‐expressed Gal‐GalNAc. Cell Host Microbe. 2016;20:215‐225. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 95. Yang GY, Shamsuddin AM. Gal‐GalNAc: a biomarker of colon carcinogenesis. Histol Histopathol. 1996;11:801‐806. [PubMed] [Google Scholar]
- 96. Springer GF. T and Tn, general carcinoma autoantigens. Science. 1984;224:1198‐1206. [DOI] [PubMed] [Google Scholar]
- 97. Zlocowski N, Grupe V, Garay YC, Nores GA, Lardone RD, Irazoqui FJ. Purified human anti‐Tn and anti‐T antibodies specifically recognize carcinoma tissues. Sci Rep. 2019;9:8097. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 98. Springer GF. Immunoreactive T and Tn epitopes in cancer diagnosis, prognosis, and immunotherapy. J Mol Med. 1997;75:594‐602. [DOI] [PubMed] [Google Scholar]
- 99. Yu LG. The oncofetal Thomsen‐Friedenreich carbohydrate antigen in cancer progression. Glycoconj J. 2007;24:411‐420. [DOI] [PubMed] [Google Scholar]
- 100. Lin WM, Karsten U, Goletz S, Cheng RC, Cao Y. Expression of CD176 (Thomsen‐Friedenreich antigen) on lung, breast and liver cancer‐initiating cells. Int J Exp Pathol. 2011;92:97‐105. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 101. Kolenbrander PE, Andersen RN. Inhibition of coaggregation between Fusobacterium nucleatum and Porphyromonas (Bacteroides) gingivalis by lactose and related sugars. Infect Immun. 1989;57:3204‐3209. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 102. Coppenhagen‐Glazer S, Sol A, Abed J, et al. Fap2 of Fusobacterium nucleatum is a galactose‐inhibitable adhesin involved in coaggregation, cell adhesion, and preterm birth. Infect Immun. 2015;83:1104‐1113. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 103. Kaplan CW, Lux R, Huynh T, Jewett A, Shi W, Haake SK Fusobacterium nucleatum apoptosis‐inducing outer membrane protein. J Dent Res. 2005;84:700‐704. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 104. Kaplan CW, Ma X, Paranjpe A, et al. Fusobacterium nucleatum outer membrane proteins Fap2 and RadD induce cell death in human lymphocytes. Infect Immun. 2010;78:4773‐4778. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 105. Abed J, Maalouf N, Parhi L, Chaushu S, Mandelboim O, Bachrach G. Tumor targeting by Fusobacterium nucleatum: A pilot study and future perspectives. Front Cell Infect Microbiol. 2017;7:295. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 106. Yamamura K, Baba Y, Miyake K, et al. Fusobacterium nucleatum in gastroenterological cancer: evaluation of measurement methods using quantitative polymerase chain reaction and a literature review. Oncol Lett. 2017;14:6373‐6378. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 107. Hsieh YY, Tung SY, Pan HY, et al. Increased abundance of clostridium and fusobacterium in gastric microbiota of patients with gastric cancer in Taiwan. Sci Rep. 2018;8:158. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 108. Audirac‐Chalifour A, Torres‐Poveda K, Bahena‐Roman M, et al. Cervical microbiome and cytokine profile at various stages of cervical cancer: a pilot study. PLoS One. 2016;11:e0153274. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 109. Serna G, Ruiz‐Pace F, Hernando J, et al. Fusobacterium nucleatum persistence and risk of recurrence after preoperative treatment in locally advanced rectal cancer. Ann Oncol. 2020;31:1366‐1375. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 110. Barr N, Taylor CR, Young T, Springer GF. Are pancarcinoma T and Tn differentiation antigens? Cancer. 1989;64:834‐841. [DOI] [PubMed] [Google Scholar]
- 111. Jeschke U, Mayr D, Schiessl B, et al. Expression of galectin‐1, ‐3 (gal‐1, gal‐3) and the Thomsen‐Friedenreich (TF) antigen in normal, IUGR, preeclamptic and HELLP placentas. Placenta. 2007;28:1165‐1173. [DOI] [PubMed] [Google Scholar]
- 112. Richter DU, Jeschke U, Makovitzky J, et al. Expression of the Thomsen‐Friedenreich (TF) antigen in the human placenta. Anticancer Res. 2000;20:5129‐5133. [PubMed] [Google Scholar]
- 113. Pinder SE, Ellis IO. The diagnosis and management of pre‐invasive breast disease: ductal carcinoma in situ (DCIS) and atypical ductal hyperplasia (ADH)–current definitions and classification. Breast Cancer Res. 2003;5:254‐257. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 114. Yamaoka Y, Suehiro Y, Hashimoto S, et al. Fusobacterium nucleatum as a prognostic marker of colorectal cancer in a Japanese population. J Gastroenterol. 2018;53:517‐524. [DOI] [PubMed] [Google Scholar]
- 115. Mima K, Sukawa Y, Nishihara R, et al. Fusobacterium nucleatum and T cells in colorectal carcinoma. JAMA Oncol. 2015;1:653‐661. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 116. Gur C, Ibrahim Y, Isaacson B, et al. Binding of the Fap2 protein of Fusobacterium nucleatum to human inhibitory receptor TIGIT protects tumors from immune cell attack. Immunity. 2015;42:344‐355. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 117. Gur C, Maalouf N, Shhadeh A, et al. Fusobacterium nucleatum supresses anti‐tumor immunity by activating CEACAM1. Oncoimmunology. 2019;8:e1581531. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 118. Brewer ML, Dymock D, Brady RL, Singer BB, Virji M, Hill DJ Fusobacterium spp. target human CEACAM1 via the trimeric autotransporter adhesin CbpF. J Oral Microbiol. 2019;11:1565043. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 119. Galaski A, Shhadeh A, Ariana U, et al. Fusobacterium nucleatum CbpF mediates inhibition of T cell function through CEACAM1 activation. Front Cell Infect Microbiol. 2021;11:692544. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 120. Sun D, Yu F, Ma Y, et al. MicroRNA‐31 activates the RAS pathway and functions as an oncogenic MicroRNA in human colorectal cancer by repressing RAS p21 GTPase activating protein 1 (RASA1). J Biol Chem. 2013;288:9508‐9518. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 121. Sun D, Wang C, Long S, et al. C/EBP‐beta‐activated microRNA‐223 promotes tumour growth through targeting RASA1 in human colorectal cancer. Br J Cancer. 2015;112:1491‐1500. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 122. Walko CM, Lindley C. Capecitabine: a review. Clin Ther. 2005;27:23‐44. [DOI] [PubMed] [Google Scholar]
- 123. Kelland L. The resurgence of platinum‐based cancer chemotherapy. Nat Rev Cancer. 2007;7:573‐584. [DOI] [PubMed] [Google Scholar]
- 124. Tanida I, Minematsu‐Ikeguchi N, Ueno T, Kominami E. Lysosomal turnover, but not a cellular level, of endogenous LC3 is a marker for autophagy. Autophagy. 2005;1:84‐91. [DOI] [PubMed] [Google Scholar]
- 125. Ramos A, Hemann MT. Drugs, bugs, and cancer: Fusobacterium nucleatum promotes chemoresistance in colorectal cancer. Cell. 2017;170:411‐413. [DOI] [PubMed] [Google Scholar]
- 126. Park SM, Yoon JB, Lee TH. Receptor interacting protein is ubiquitinated by cellular inhibitor of apoptosis proteins (c‐IAP1 and c‐IAP2) in vitro. FEBS Lett. 2004;566:151‐156. [DOI] [PubMed] [Google Scholar]
- 127. Perez‐Ordonez B, Beauchemin M, Jordan RC. Molecular biology of squamous cell carcinoma of the head and neck. J Clin Pathol. 2006;59:445‐453. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 128. Espinosa I, Lee CH, Kim MK, et al. A novel monoclonal antibody against DOG1 is a sensitive and specific marker for gastrointestinal stromal tumors. Am J Surg Pathol. 2008;32:210‐218. [DOI] [PubMed] [Google Scholar]
- 129. Ojima T, Nakamori M, Nakamura M, et al. Neoadjuvant chemotherapy with divided‐dose docetaxel, cisplatin and fluorouracil for patients with squamous cell carcinoma of the esophagus. Anticancer Res. 2016;36:829‐834. [PubMed] [Google Scholar]
- 130. Hara H, Tahara M, Daiko H, et al. Phase II feasibility study of preoperative chemotherapy with docetaxel, cisplatin, and fluorouracil for esophageal squamous cell carcinoma. Cancer Sci. 2013;104:1455‐1460. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 131. Hamada T, Zhang X, Mima K, et al. Fusobacterium nucleatum in colorectal cancer relates to immune response differentially by tumor microsatellite instability status. Cancer Immunol Res. 2018;6:1327‐1336. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 132. Chen T, Li Q, Zhang X, et al. TOX expression decreases with progression of colorectal cancers and is associated with CD4 T‐cell density and Fusobacterium nucleatum infection. Hum Pathol. 2018;79:93‐101. [DOI] [PubMed] [Google Scholar]
- 133. Chen S, Su T, Zhang Y, et al. Fusobacterium nucleatum promotes colorectal cancer metastasis by modulating KRT7‐AS/KRT7. Gut Microbes. 2020;11:511‐525. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 134. Casasanta MA, Yoo CC, Udayasuryan B, et al. Fusobacterium nucleatum host‐cell binding and invasion induces IL‐8 and CXCL1 secretion that drives colorectal cancer cell migration. Sci Signal. 2020;13:eaba9157. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 135. Mehner C, Hockla A, Miller E, Ran S, Radisky DC, Radisky ES. Tumor cell‐produced matrix metalloproteinase 9 (MMP‐9) drives malignant progression and metastasis of basal‐like triple negative breast cancer. Oncotarget. 2014;5:2736‐2749. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 136. Siegel RL, Miller KD, Jemal A. Cancer statistics, 2016. CA Cancer J Clin. 2016;66:7‐30. [DOI] [PubMed] [Google Scholar]
- 137. Poore GD, Kopylova E, Zhu Q, et al. Microbiome analyses of blood and tissues suggest cancer diagnostic approach. Nature. 2020;579:567‐574. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 138. Schreuders EH, Ruco A, Rabeneck L, et al. Colorectal cancer screening: a global overview of existing programmes. Gut. 2015;64:1637‐1649. [DOI] [PubMed] [Google Scholar]
- 139. Brenner H, Hoffmeister M, Birkner B, Stock C. Diagnostic performance of guaiac‐based fecal occult blood test in routine screening: state‐wide analysis from Bavaria, Germany. Am J Gastroenterol. 2014;109:427‐435. [DOI] [PubMed] [Google Scholar]
- 140. Gies A, Niedermaier T, Gruner LF, Heisser T, Schrotz‐King P, Brenner H. Fecal immunochemical tests detect screening participants with multiple advanced adenomas better than T1 Colorectal Cancers. Cancers. 2021;13(4):644. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 141. Huang Q, Peng Y, Xie F. Fecal Fusobacterium nucleatum for detecting colorectal cancer: a systematic review and meta‐analysis. Int J Biol Markers. 2018;33(4):345‐352. [DOI] [PubMed] [Google Scholar]
- 142. Wong SH, Kwong TNY, Chow TC, et al. Quantitation of faecal Fusobacterium improves faecal immunochemical test in detecting advanced colorectal neoplasia. Gut. 2017;66:1441‐1448. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 143. Liang Q, Chiu J, Chen Y, et al. Fecal bacteria act as novel biomarkers for noninvasive diagnosis of colorectal cancer. Clin Cancer Res. 2017;23:2061‐2070. [DOI] [PubMed] [Google Scholar]
- 144. Wang HF, Li LF, Guo SH, et al. Evaluation of antibody level against Fusobacterium nucleatum in the serological diagnosis of colorectal cancer. Sci Rep. 2016;6:33440. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 145. Butt J, Jenab M, Pawlita M, et al. Antibody responses to Fusobacterium nucleatum proteins in prediagnostic blood samples are not associated with risk of developing colorectal cancer. Cancer Epidemiol Biomarkers Prev. 2019;28:1552‐1555. [DOI] [PubMed] [Google Scholar]
- 146. Kurt M, Yumuk Z. Diagnostic accuracy of Fusobacterium nucleatum IgA and IgG ELISA test in colorectal cancer. Sci Rep. 2021;11:1608. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 147. Alkharaan H, Lu L, Gabarrini G, et al. Circulating and salivary antibodies to Fusobacterium nucleatum are associated with cystic pancreatic neoplasm malignancy. Front Immunol. 2003;2020:11. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 148. Viaud S, Saccheri F, Mignot G, et al. The intestinal microbiota modulates the anticancer immune effects of cyclophosphamide. Science. 2013;342:971‐976. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 149. Iida N, Dzutsev A, Stewart CA, et al. Commensal bacteria control cancer response to therapy by modulating the tumor microenvironment. Science. 2013;342:967‐970. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 150. Vetizou M, Pitt JM, Daillere R, et al. Anticancer immunotherapy by CTLA‐4 blockade relies on the gut microbiota. Science. 2015;350:1079‐1084. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 151. Sivan A, Corrales L, Hubert N, et al. Commensal Bifidobacterium promotes antitumor immunity and facilitates anti‐PD‐L1 efficacy. Science. 2015;350:1084‐1089. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 152. Gopalakrishnan V, Spencer CN, Nezi L, et al. Gut microbiome modulates response to anti‐PD‐1 immunotherapy in melanoma patients. Science. 2018;359:97‐103. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 153. Routy B, Le Chatelier E, Derosa L, et al. Gut microbiome influences efficacy of PD‐1‐based immunotherapy against epithelial tumors. Science. 2018;359:91‐97. [DOI] [PubMed] [Google Scholar]
- 154. Matson V, Chervin CS, Gajewski TF. Cancer and the microbiome‐influence of the commensal microbiota on cancer, immune responses, and immunotherapy. Gastroenterology. 2021;160:600‐613. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 155. Matson V, Fessler J, Bao R, et al. The commensal microbiome is associated with anti‐PD‐1 efficacy in metastatic melanoma patients. Science. 2018;359:104‐108. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 156. Elkrief A, Derosa L, Kroemer G, Zitvogel L, Routy B. The negative impact of antibiotics on outcomes in cancer patients treated with immunotherapy: a new independent prognostic factor? Ann Oncol. 2019;30:1572‐1579. [DOI] [PubMed] [Google Scholar]
- 157. Tonneau M, Elkrief A, Pasquier D, et al. The role of the gut microbiome on radiation therapy efficacy and gastrointestinal complications: a systematic review. Radiother Oncol. 2020;156:1‐9. [DOI] [PubMed] [Google Scholar]
- 158. Jenq RR, Ubeda C, Taur Y, et al. Regulation of intestinal inflammation by microbiota following allogeneic bone marrow transplantation. J Exp Med. 2012;209:903‐911. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 159. Kabwe M, Brown TL, Dashper S, et al. Genomic, morphological and functional characterisation of novel bacteriophage FNU1 capable of disrupting Fusobacterium nucleatum biofilms. Sci Rep. 2019;9:9107. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 160. Wu C, Al Mamun AAM, Luong TT, et al. Forward genetic dissection of biofilm development by Fusobacterium nucleatum: novel functions of cell division proteins FtsX and EnvC. MBio. 2018;9:e00360. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 161. Lee S, Lim B, You D, et al. Association of Bacillus Calmette‐Guerin shortages with bladder cancer recurrence: a single‐center retrospective study. Urol Oncol. 2020;38(11):851.e11‐851.e17. [DOI] [PubMed] [Google Scholar]
- 162. Klinger D, Hill BL, Barda N, et al. Bladder cancer immunotherapy by BCG is associated with a significantly reduced risk of Alzheimer’s disease and Parkinson’s disease. Vaccines. 2021;9:491. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 163. Zheng DW, Dong X, Pan P, et al. Phage‐guided modulation of the gut microbiota of mouse models of colorectal cancer augments their responses to chemotherapy. Nat Biomed Eng. 2019;3:717‐728. [DOI] [PubMed] [Google Scholar]
- 164. Ayres Pereira M, Mandel Clausen T, Pehrson C, et al. Placental sequestration of Plasmodium falciparum malaria parasites is mediated by the interaction between VAR2CSA and chondroitin sulfate A on syndecan‐1. PLoS Pathog. 2016;12(8):e1005831. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 165. Agerbaek MO, Bang‐Christensen S, Salanti A. Fighting cancer using an oncofetal glycosaminoglycan‐binding protein from malaria parasites. Trends Parasitol. 2019;35:178‐181. [DOI] [PubMed] [Google Scholar]
- 166. Agerbaek MO, Bang‐Christensen SR, Yang MH, et al. The VAR2CSA malaria protein efficiently retrieves circulating tumor cells in an EpCAM‐independent manner. Nat Commun. 2018;9:3279. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 167. Salanti A, Clausen TM, Agerbaek MO, et al. Targeting human cancer by a glycosaminoglycan binding malaria protein. Cancer Cell. 2015;28:500‐514. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 168. Sears CL, Pardoll DM. Perspective: alpha‐bugs, their microbial partners, and the link to colon cancer. J Infect Dis. 2011;203:306‐311. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 169. Nougayrede JP, Homburg S, Taieb F, et al. Escherichia coli induces DNA double‐strand breaks in eukaryotic cells. Science. 2006;313:848‐851. [DOI] [PubMed] [Google Scholar]
- 170. Goodwin AC, Destefano Shields CE, Wu S, et al. Polyamine catabolism contributes to enterotoxigenic Bacteroides fragilis‐induced colon tumorigenesis. Proc Natl Acad Sci USA. 2011;108:15354‐15359. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 171. Wu S, Lim KC, Huang J, Saidi RF, Sears CL Bacteroides fragilis enterotoxin cleaves the zonula adherens protein, E‐cadherin. Proc Natl Acad Sci USA. 1998;95:14979‐14984. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 172. Wu S, Rhee KJ, Zhang M, Franco A, Sears CL Bacteroides fragilis toxin stimulates intestinal epithelial cell shedding and gamma‐secretase‐dependent E‐cadherin cleavage. J Cell Sci. 2007;120:1944‐1952. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 173. Suerbaum S, Michetti P Helicobacter pylori infection. N Engl J Med. 2002;347:1175‐1186. [DOI] [PubMed] [Google Scholar]
- 174. Hatakeyama M Helicobacter pylori CagA and gastric cancer: a paradigm for hit‐and‐run carcinogenesis. Cell Host Microbe. 2014;15:306‐316. [DOI] [PubMed] [Google Scholar]
- 175. Gur C, Maalouf N, Gerhard M, et al. The Helicobacter pylori HopQ outermembrane protein inhibits immune cell activities. Oncoimmunology. 2019;8:e1553487. [DOI] [PMC free article] [PubMed] [Google Scholar]