Protein fractions associated with Prevotella intermedia suppress the growth of HSC-3 oral squamous cell carcinoma cells

OBJECTIVES: Oral microbiomes are associated with the progression of oral squamous cell carcinoma (OSCC). Prevotella intermedia is associated with tumor progression; however, the direct effects of P. intermedia on OSCC cells have not been elucidated. In this study, the aim was to elucidate the direct effects of P. intermedia on OSCC cells. METHODS: HSC-2, HSC-3, and SAS cells were treated with P. intermedia OMA14 at multiplicities of infection of 10 and 100, and cell viability was then assessed using a cell-counting kit (CCK)-8 assay. The effects of heat-killed P. intermedia OMA14 and protein fractions prepared from SDS-PAGE-separated membrane strips on HSC-3 cell viability were assessed using the CCK-8 assay. Cell migration, cell cycle, and lactate dehydrogenase (LDH) cytotoxicity assays were performed using HSC-3 cells treated with P. intermedia OMA14. RESULTS: Treatment with P. intermedia OMA14 reduced HSC-3 cell viability, whereas there were no significant changes in SAS or HSC-2 cell viability. Heat-killed P. intermedia did not reduce HSC-3 cell viability. P. intermedia also suppressed HSC-3 cell migration, and it induced G0/G1-phase cell-cycle arrest without increasing LDH release. In addition, among the P. intermedia-derived protein fractions, the fractions corresponding to approximately 75 kDa and 15-20 kDa had the strongest inhibitory effects on HSC-3 cell viability. CONCLUSION: P. intermedia OMA14 reduced HSC-3 cell viability through an anti-proliferative mechanism associated with G0/G1-phase cell-cycle arrest rather than overt cytotoxicity. Protein fractions of approximately 75 kDa and 15-20 kDa showed the strongest inhibitory effects on HSC-3 cell viability.