br Comparison of relative abundance of genera br Peptostrept
4.2. Comparison of relative abundance of genera
Peptostreptococcus was abundant in OSCC patients. Genus Fusobacterium includes obligate EPZ-6438 bacteria and is consid-ered to be related to apical periodontitis and periodontal disease [25e27]. It has been consistently reported that Peptostreptococcus is markedly increased in OSCC samples [10,11,28]. There was also a report that Peptostreptococcus stomatis is involved in colorectal cancer .
Another report suggested that Fusobacterium is markedly increased in OSCC patients and is also involved in cancer pro-gression . Fusobacterium is known as a key bacterium forming
crosslinked biofilm structures during colony formation and coex-isting with other bacteria. Therefore, it is possible that the action of Fusobacterium may result in increased diversity in OSCC patients.
It has been reported that Veillonella is markedly decreased in samples of patients who have completed cancer treatment . However, in our results there was no difference in the ratio be-tween the two groups.
There was a report that the genus Capnocytophaga was remarkably higher in salivary samples from lung cancer patients than from healthy subjects . Another report also suggested that C. gingivalis may be a biomarker for oral cancer . r> In the comparison of microbiota with the TNM classification, a negative correlation was observed in progression of the T factor indicating tumor size and invasion degree. a-diversity (observed index) decreased with progression of the T factor (Fig. 5A).
Fig. 5. Comparison of microbiota depending on the TNM-stage progression. a-diversity decreased from T2 to T4. b-diversity showed a significant correlation (A). No diversity difference was observed with N factor (B). Relative abundance of genus Rothia was associated with T-stage progression. Rothia revealed a negative correlation which decreases with progression of T factor (C). Each black dot shows the individual OTUs.
However, since a-diversity (observed index) was increased as a whole in the OSCC patients compared to the healthy controls, changes in the oxygen exposure state, the influence of exudates from necrotic tissue, and changes in the immune state can occur as the tumor increases. It is also possible that the microbiota changes.
For the N factor indicating lymph node metastasis, progressing a-diversity (observed index) was not observed (Fig. 5B). Regarding the presence or absence of lymph node metastasis, a relationship with tumor size could not be clarified. The participants of this study showed lymph node metastasis at T4 and also at T1, due to which the relevance could not be confirmed. The nature of the tumor surface tissue influences the changes in microbiota. Thus, if caused by microbiota changes, the result is not contradictory in that, the T factor was involved in the microbiota change, but not the presence or absence of N factor.
In this study, Rothia revealed a negative correlation showing a decrease with the progression of the T factor (Fig. 5C), and from a previous study, we know that it is remarkably low in OSCC patients [9,10,23]. Moreover, although this bacterium is consid-ered to be phylogenetically related to Actinomyces, its pathoge-nicity itself is considered low. Thus, it is possible that Rothia is common among healthy people.
In this study, we examined factors influencing cancer incidence using logistic regression analysis (Table 3). So far, sex, smoking, and drinking habits have been reported as cancer risk factors [3,33,34], but in this study we obtained similar results only with regard to sex. An odds ratio of 10.85 also indicated a high risk.
The genera Rothia, Alloprevotella, Capnocytophaga, Fusobacte-rium, Haemophilus, and family Peptostreptococcus, which showed a significant difference in abundance among OSCC patients compared to the healthy controls, had no influence on cancer incidence, however the Chao 1 index, indicating a-diversity, showed a significant difference regarding cancer incidence. Although the odds ratio was 1.006, it is possible that the diversity index indicates an influencing factor for cancer incidence.
4.3. Relationship between oral microbiota and disease
It is suggested that there is also an age difference in the occur-rence of oral cancer .
Recent studies have reported that gut microbiota and age are related and that the microbiota changes with age [36,37]. In addi-tion, a relationship between intestinal microbiota and the general condition of the immune status has also been reported .
There have been several reports showing differences between the oral microbiota in healthy people and periodontitis patients [39,40]. Changes in the oral microbial flora have also been re-ported using saliva samples for comparison between aged care facility residents and the healthy group among the elderly in Japan. A significant difference was observed in a-diversity be-tween these two groups . From the results obtained in this study, differences in diversity and the existence of specific minor bacterial species might influence the incidence of OSCC and microbiota composition.