Cell‐Free Supernatant of Porphyromonas gingivalis Promotes the Malignancy of Oral Squamous Cell Carcinoma by Suppressing Ferroptosis

BACKGROUND: Oral squamous cell carcinoma (OSCC) is a series global health concern. Porphyromonas gingivalis (P.g), a major pathogenic bacterium, promotes tumorigenesis and progression. Ferroptosis is also closely related to the progression of tumors. Therefore, this study aimed to investigate whether P.g cell-free supernatant (Pg-SN) alters ferroptosis and malignant phenotypes in OSCC cells. METHODS: CCK-8 assays were used to compare the effects of cell-free Pg-SN and Streptococcus salivarius cell-free supernatant (Ss-SN) on OSCC cell viability. Wound healing and Transwell invasion assays were then performed to assess Pg-SN-induced changes in the migratory and invasive abilities. Flow cytometry and fluorescence microscopy were employed to examine ferroptosis biomarkers. Transmission electron microscopy was utilized to observe mitochondrial morphology, while western blot and immunofluorescence analyses were performed to assess ferroptosis-related proteins. RESULTS: Pg-SN enhanced the proliferation, migration, and invasion of OSCC cells. In addition, Pg-SN suppressed ferroptosis in OSCC cells. In comparison, Ss-SN had no significant effect on RSL-3 induced ferroptosis and OSCC cell viability. Furthermore, mechanistic studies demonstrated that Pg-SN modulated the Nrf2/SLC7A11/GPX4 signaling pathway and reduced reactive oxygen species (ROS) and lipid peroxidation (LPO) levels. Pg-SN did not significantly alter TfR1 or ACSL4 expression, suggesting that the suppressive effect on ferroptosis may be independent of iron uptake and ACSL4-dependent lipid remodeling. CONCLUSION: This study demonstrates that Pg-SN modulates the Nrf2/SLC7A11/GPX4 signaling pathway to suppress ferroptosis and promote the progression of OSCC cells. Targeting P.g associated ferroptosis resistance may represent a potential therapeutic strategy for OSCC.