Analysis of the protumoral mechanisms of F.nucleatum on growth, epithelial-mesenchymal transition and the expression of immunosuppressive markers in cell line of OSCC

Abstract Background: Oral squamous cell carcinoma (OSCC) is the most common manifestation of oral cancer. It has been proposed that periodontal pathogens contribute to OSCC progression, and preliminary data from our laboratory has identified Fusobacterium nucleatum (F.n) and Epithelial Mesenchymal Transition (EMT) markers in the secretome of biopsies from patients with OSCC in comparison with healthy biopsies from the oral cavity. However, the mechanisms modulated by the tumoral bacteriome in OSCC remains not fully understood. Methods: Oral cancer cells (HSC3) were infected with F.n using a MOI of 100 to evaluate the effect of the bacteria on tumor growth, expression of EMT markers and immunomodulatory properties. Results: After infection, we confirmed the presence of bacteria inside and surrounding the cancer cells by confocal microscopy. Then, a significant increment in the size of F.n-infected tumor spheroids was found at 3-, 6- and 10-days post-infection. Related to EMT markers, MMP-9 transcripts were significantly elevated in infected cells, whereas E-cadherin transcripts were significantly downregulated post infection. In addition, the Human XL Oncology array kit revealed that several cancer proteins such as MMP-3, GM-CSF, FOXO1/FKHR, Cathepsina D-S, Amphiregulin, SerpinB5/Maspin and EGFR were upregulated and others like ICAM-1, DLL-1 and ERB2 were downregulated after F.n-infection. Finally, the expression of Galectin-9 measured by flow cytometry was significantly increased in infected cells than control cancer cells. Conclusions: The periodontal bacterium F.n promotes tumor progression of OSCC through increased tumor growth, acquisition of ETM-associated markers and Galectin-9 upregulation. Fondecyt Regular Project 1211480