Carcinogenesis of Male Oral Submucous Fibrosis Alters Salivary Microbiomes

Abstract

Most oral squamous cell carcinoma (OSCC) tumors arise from oral premalignant lesions. Oral submucous fibrosis (OSF), usually occurring in male chewers of betel quid, is a premalignant stromal disease characterized by a high malignant transformation rate and high prevalence. Although a relationship between the inhabited microbiome and carcinogenesis has been proposed, no detailed information regarding the oral microbiome of patients with OSF exists; the changes of the salivary microbiome during cancer formation remain unclear. This study compared the salivary microbiomes of male patients with OSCC and a predisposing OSF background (OSCC-OSF group) and those with OSF only (OSF group). The results of high-throughput sequencing of the bacterial 16S rRNA gene indicated that OSF-related carcinogenesis and smoking status significantly contributed to phylogenetic composition variations in the salivary microbiome, leading to considerable reductions in species richness and phylogenetic diversity. The microbiome profile of OSF-related malignancy was associated with increased microbial stochastic fluctuation, which dominated the salivary microbiome assembly and caused species co-occurrence network collapse. Artificial intelligence selection algorithms consistently identified 5 key species in the OSCC-OSF group: Porphyromonas catoniae, Prevotella multisaccharivorax, Prevotella sp. HMT-300, Mitsuokella sp. HMT-131, and Treponema sp. HMT-927. Robust accuracy in predicting oral carcinogenesis was obtained with our exploratory and validation data sets. In functional analysis, the microbiome of the OSCC-OSF group had greater potential for S-adenosyl-l-methionine and norspermidine synthesis but lower potential for l-ornithine and pyrimidine deoxyribonucleotide synthesis and formaldehyde metabolism. These findings indicated that the salivary microbiome plays important roles in modulating microbial metabolites during oral carcinogenesis. In conclusion, our results provided new insights into salivary microbiome alterations during the malignant transformation of OSF.

Taxonomic and Functional Dysregulation in Salivary Microbiomes During Oral Carcinogenesis

“…Although the within-group diversity was not significantly different among cohorts, a decreased trend of core microbiome from healthy or OVH to OSCC was observed when the total diversity of each cohort (gamma diversity) was considered. Consistent with the previous studies that the richness of core species among healthy individuals was 9.6-13.1% ( Takeshita et al., 2016 ; Willis et al., 2018 ) and it decreased to 5.96% in the OSCC patients with oral submucous fibrosis ( Chen et al., 2020 ), our study also showed the decrease of richness from 12.53% in the normal cohort to 6.34% in the OSCC cohort. Together, the gamma diversity as an indication reflecting dysbiosis of the core salivary microbiome is effectually linked to the progression of oral cancer.…”

“…Several amino acid biosynthesis pathways (isoleucine, tryptophan, arginine, ornithine, valine, and methionine) were enriched in the normal group, particularly in Zhao’s and our datasets ( Figure S5 ), suggesting potential up-regulation of those amino acids in the healthy cohort (and correspondingly down-regulation in the OSCC cohort), which is consistent with previous studies ( Yang et al., 2018 ). Several previous studies also suggested the dysregulation of ornithine, arginine, and polyamine synthesis in the salivary microbiome during oral carcinogenesis from the healthy or precancerous stage ( Chen et al., 2020 ; Sharma et al., 2020 ). In addition, Zhao’s and our study showed that the biosynthesis of lipids and fatty acids, especially cis-vaccenate and gondoate are enriched in the OSCC cohort ( Figure 3 ).…”

“…Studies have suggested that the oral microbiome changed during the progression of OSCC ( Zhao et al., 2017 ; Hashimoto et al., 2019 ; Chen et al., 2020 ). These studies mainly focused on two cohorts (healthy control/OSCC or OPMD/OSCC) instead of three (healthy control/OPMD/OSCC) without a follow-up.…”

“…As such, the quantitative determination of the ecological drivers influencing community composition in an ecosystem is important for explicitly elucidating the community dynamics. By quantifying the stochasticity ratio using the pattern-oriented null model ( Ning et al., 2019 ), our previous study showed the dominance of stochastic perturbations in shaping the oral microbiomes of oral submucous fibrosis (one of the OPMDs) and OSCC cohorts ( Chen et al., 2020 ). The influence of stochastic perturbations might also be crucial in the healthy group, given that the oral microbiome was highly personalized and time-varied ( Mukherjee et al., 2018 ).…”

Letter to the Editor: “Carcinogenesis of Male Oral Submucous Fibrosis Alters Salivary Microbiomes”

“…A recently published paper by Chen et al (2021) provided new insights into salivary microbiome and microbial metabolite alterations during the malignant transformation of oral submucous fibrosis (OSF). These findings gave new direction to the understanding of carcinogenesis mechanism of oral squamous cell carcinoma in the background of OSF (OSCC-OSF).…”