Analysis of Salivary Mycobiome in a Cohort of Oral Squamous Cell Carcinoma Patients From Sudan Identifies Higher Salivary Carriage of Malassezia as an Independent and Favorable Predictor of Overall Survival

Abstract

BackgroundMicrobial dysbiosis and microbiome-induced inflammation have emerged as important factors in oral squamous cell carcinoma (OSCC) tumorigenesis during the last two decades. However, the “rare biosphere” of the oral microbiome, including fungi, has been sparsely investigated. This study aimed to characterize the salivary mycobiome in a prospective Sudanese cohort of OSCC patients and to explore patterns of diversities associated with overall survival (OS).Materials and MethodsUnstimulated saliva samples (n = 72) were collected from patients diagnosed with OSCC (n = 59) and from non-OSCC control volunteers (n = 13). DNA was extracted using a combined enzymatic–mechanical extraction protocol. The salivary mycobiome was assessed using a next-generation sequencing (NGS)-based methodology by amplifying the ITS2 region. The impact of the abundance of different fungal genera on the survival of OSCC patients was analyzed using Kaplan–Meier and Cox regression survival analyses (SPPS).ResultsSixteen genera were identified exclusively in the saliva of OSCC patients. Candida, Malassezia, Saccharomyces, Aspergillus, and Cyberlindnera were the most relatively abundant fungal genera in both groups and showed higher abundance in OSCC patients. Kaplan–Meier survival analysis showed higher salivary carriage of the Candida genus significantly associated with poor OS of OSCC patients (Breslow test: p = 0.043). In contrast, the higher salivary carriage of Malassezia showed a significant association with favorable OS in OSCC patients (Breslow test: p = 0.039). The Cox proportional hazards multiple regression model was applied to adjust the salivary carriage of both Candida and Malassezia according to age (p = 0.029) and identified the genus Malassezia as an independent predictor of OS (hazard ratio = 0.383, 95% CI = 0.16–0.93, p = 0.03).ConclusionThe fungal compositional patterns in saliva from OSCC patients were different from those of individuals without OSCC. The fungal genus Malassezia was identified as a putative prognostic biomarker and therapeutic target for OSCC.

The oral mycobiome: Oral epithelial dysplasia and oral squamous cell carcinoma

“…Finally, findings from a recent mechanistic study in pancreatic cancer showed that mycobiota with predominance of the Malassezia genus displayed tumor‐promoting effects through activation of mannose‐binding lectin which binds to the glycans of the fungal wall with subsequent involvement of adaptive responses (i.e., upregulation of the C3 complement cascade which was proved necessary for tumor development in this model) 40 . Interestingly, upregulation of the same genus in cases of OSCC was shown to correlate with favorable prognosis, highlighting the organ‐specific pathogenicity of mycobiome dysbiosis 41 …”

“…40 Interestingly, upregulation of the same genus in cases of OSCC was shown to correlate with favorable prognosis, highlighting the organ-specific pathogenicity of mycobiome dysbiosis. 41 In this pathogenic model, an environmental factor (Candida) causes well-established hyperplastic changes in the lining epithelium of the oral mucosa termed chronic hyperplastic candidosis (CHC) with the potential of progressing to a premalignant (OED) and malignant (OSCC) sequence through the previously described mechanisms (Figure 1A). It is obvious that intervention with antifungal therapy in the reversible step of CHC may result in regression of the clinically identifiable white plaque and thus preclude the development of cancer, 42 while intervention after the development of OED does not result in regression of the established dysplastic and molecular changes but may eliminate any further tumor-initiating effects of Candida.…”

“…This setting implies that treatment with antifungals cannot resolve the lesion and is not sufficient to treat this multifactorial process, and thus the lesion should be managed as a leukoplakia 2 . The possible tumor‐promoting events of mycobiome dysbiosis in this clinical setting may also be indirectly supported by recent evidence from a descriptive study indicating that OSCC patients with Candida may display a decreased overall survival 41 …”

Malassezia in Inflammatory Bowel Disease: Accomplice of Evoking Tumorigenesis

“…Furthermore, they have demonstrated that repopulation with Malassezia could promote PC through mannose-binding lectin (MBL) signal pathway, thus accordingly its ablation with amphotericin B in murine models was found to slow oncogenic progression (31,105). Malassezia also showed higher relative abundance in patients with oral squamous cell carcinoma (OSCC), compared with control volunteers (106). In addition, Gao and collaborators discovered that although there was no significant difference in stool mycobiota diversity between CRC patients and healthy controls, the fungal subgroup Malassezia genus was more enriched in people with CRC, which was positively correlated with tumor progression (48).…”

Is Candida albicans an opportunistic oncogenic pathogen?

“…Neoplastic processes affecting other organs have been investigated [ 10 ], including pancreatic cancer induced by Malassezia genus [ 11 ]. However, conversely, the same fungus was shown to correlate with favorable prognosis [ 12 ] in oral cancer, highlighting the complex and organ-specific oncogenicity of mycobiome dysbiosis. Within the framework of oral cancer, C .…”