Table 1.
Summary of various experimental studies regarding the presence of oral bacteria in colorectal cancer (CRC).
| Oral Bacteria. | Sampling/Size | Methods | Main Findings | References |
|---|---|---|---|---|
| Fusobacterium, Gemella, Peptostreptococcus and Parvimonas | —Colonic mucosa/ control (n = 61), colonic adenoma-normal adjacent pair (n = 47), tumor tissue-normal adjacent pair (n = 52) | 16S rRNA gene sequencing | —Increased abundance of presented bacteria in CRC —Mucosal microbiota demonstrates distinct changes across stages of CRC tumorigenesis. |
Nakatsu et al. 2015 [80] |
| Actinomyces, Corynebacterium, Haemophilus, Mogibacterium, and Porphyromonas | —Feces/colonic adenoma patients (n = 233), control (n = 547) | 16S rRNA gene sequencing | —Increased abundance of presented bacteria in colonic adenomas | Hale et al. 2017 [81] |
| Fusobacterium, Oscillibacter, Peptostreptococcus, Porphyromonas, Roseburia, and Ruminococcus | —Colonic mucosa/tumor tissue (n = 59), colonic adenoma (n = 21), control (n = 56) | 16S rRNA gene sequencing, real-time qPCR | —Increased abundance of presented bacteria in CRC | Flemer et al. 2017 [45] |
| Fusobacterium nucleatum, Peptostreptococcus stomatitis, and Parvimonas micra | —Oral swabs, feces, colonic mucosa/CRC patients (n = 99), colonic adenoma patients (n = 32), Controls (n = 103) |
16S rRNA gene sequencing | —Increased abundance of presented bacteria in CRC —Oral microbiota is distinctive and predictive in CRC |
Flemer et al. 2018 [83] |
|
Treponema denticola, Bifidobacteriaceae, and Prevotella Carnobacteriaceae, Erysipelotrichaceae, Prevotella melaninogenica, Streptococcus, and Solobacterium |
—Mouth rinse/CRC patients (n = 231), Control (n = 462) | 16S rRNA gene sequencing | —The former group of bacteria was associated with increased risk of CRC —The latter group of bacteria was associated with reduced risk of CRC |
Yang et al. 2018 [86] |
| Fusobacterium spp. (F. nucleatum, F. mortiferum, and F. necrophorum) | —Colonic mucosa/tumor tissue-normal adjacent pair (n = 95) | qPCR, 16S rRNA gene sequencing, FISH | —Bacteria belonging to Fusobacterium were abundant in CRC | Kostic et al. 2012 [87] |
| Fusobacterium (F. nucleatum) | —Colonic mucosa/ tumor tissue-matched normal tissue (n = 99) | qPCR, 16S rRNA gene sequencing | —Increased abundance of Fusobacterium in CRC was positively associated with lymph node metastasis | Castellarin et al. 2012 [49] |
| Fusobacterium spp., Porphyromonas spp. | —Feces/CRC patients (n = 47), control (n = 94) | 16S rRNA gene sequencing | —Increased abundance of presented bacteria in CRC patients —Decreased abundance of Clostridium spp. was simultaneously detected |
Ahn et al. 2013 [90] |
| Fusobacterium nucleatum | —Colonic mucosa/tumor tissue-matched normal tissue (n = 122), colonic adenoma-matched normal tissue (n = 52) —Feces/CRC patients (n = 7), colonic adenoma patients (n = 24), controls (n = 25) |
qPCR | —Patients with high levels of F. nucleatum presented a significantly shorter survival time that patients with low levels of this species | Flanagan et al. 2014 [88] |
| Fusobacterium spp. | Colonic mucosa/tumor tissue (n = 149), normal adjacent tissue (n = 89), control (n = 72) | qPCR | —Fusobacterium enhancement is associated with specific molecular subsets of CRC | Tahara et al. 2014 [93] |
| Fusobacterium spp. and Lactococcus spp. | —Colonic mucosa/ tumor tissue (n = 31), normal adjacent tissue (n = 20) | 16S rRNA gene sequencing | —Increased abundance of presented bacteria in CRC —Pseudomonas and Escherichia-Shigella were decreased |
Gao et al. 2015 [94] |
| Fusobacterium nucleatum | —Colonic mucosa/tumor tissue (n = 1102) | qPCR | —Increased abundance of this species in proximal CRC | Mima et al. 2016 [92] |
| Fusobacterium nucleatum | —Colonic mucosa/tumor tissue (n = 100), normal tissue (n = 72) | Droplet digital PCR | —Overabundance of this species correlated with KRAS mutation, tumor size, and shorter survival time | Yamaoka et al. 2018 [99] |
| Fusobacterium nucleatum | —Colonic mucosa/tumor tissue (n = 296) | HT RNA sequencing, real time qPCR | —Fusobacterium nucleatum promotes chemoresistance through modulation of autophagy in CRC | Yu et al. 2017 [100] |
| Fusobacterium nucleatum | —Colonic mucosa, saliva/CRC patients (n = 14) | AP-PCR, 16S rRNA gene sequencing | —Similar strains of Fusobacterium nucleatum are presented between oral cavity and colon in CRC patients | Komiya et al. 2019 [101] |
AP-PCR: arbitrarily primed polymerase chain reaction, CRC: colorectal cancer, HT: high-throughput, qPCR: quantitative PCR, FISH: fluorescent in situ hybridization.