The role of Fusobacterium nucleatum and Candida albicans interkingdom interactions in promoting OSCC

PROJECT SUMMARY Oral squamous cell carcinoma (OSCC) exerts a significant clinical and financial burden worldwide. Recently, there has been increasing interest in the role of the microbiome in OSCC. Among microbial species that have frequently been identified in association with OSCC and demonstrated to promote oral carcinogenesis, both in vitro and in animal models, include the bacterium Fusobacterium nucleatum and the fungus Candida albicans. The two species have been demonstrated to interact via co-aggregation; however, whether such interkingdom interaction can promote oral carcinogenesis has never been explored The current proposal builds on our previous studies investigating the microbiome associated with OSCC and oral leukoplakia in clinical samples, and assessing the effects of oral bacteria against oral epithelial cell lines in vitro. The proposed studies will investigate for the first time the potentially synergistic interaction between C. albicans and F. nucleatum in malignant progression, which we hypothesize is facilitated by their coaggregation. Based on our preliminary data, we also hypothesize that the two species mediate part of their oncogenic properties through upregulation of INHBA, a proposed oncogene acting through the TGF-β pathway. To address these hypotheses, we propose to assess synergistic effects of C. albicans and F. nucleatum on normal, dysplastic, and neoplastic oral epithelium in vitro (Aim 1), and to study the carcinogenicity of C. albicans and F. nucleatum co-carriage in 4- nitroquinoline-1-oxide-induced OSCC mouse model (Aim 2). Combinations of wild-type, aggregation +ve strains and mutant, aggregation-deficient strains of the two species will be used in the two aims to assess the role of co-aggregation in promoting synergistic carcinogenicity. The involvement of INHBA upregulation in this synergy will be investigated by mechanistic gene knockdown experiments. The project will employ a range of technologies including cellular and biochemical assays, metatranscriptomics, histopathology, immunohistochemistry, flow cytometry, q-PCR, fluorescent in-situ hybridization and 16S sequencing to investigate the effect of treating the cell lines and mice with the test species. This innovative, exploratory study leverages the complementary expertise of the research team to provide a first insight into the potential role of interkingdom microbial interactions in OSCC and shed light on novel mechanisms by which C. albicans and F. nucleatum may contribute to oral carcinogenesis