Early modulatory effects of Porphyromonas gingivalis and Lactobacillus salivarius on oncogenic processes in dysplastic oral keratinocytes

Background: Disruption of oral homeostasis can contribute to diseases such as oral cancer. This study investigates the early modulatory effects of the probiotic Lactobacillus salivarius and the pathogen Porphyromonas gingivalis on dysplastic oral keratinocytes (DOK). Methods and results: DOK cells were co-cultured with each bacterium at a multiplicity of infection (MOI) of 10 for 2 and 6 h. Following co-culture, RNA was extracted to assess the relative expression of key carcinogenesis-related genes (DUSP16, PIK3CA, AKT, mTOR, ALOX5, VEGF, COX2, HEY1, JAGGED1) via qPCR. Complementary assays included Annexin V, scratch-wound healing, and Raman micro-spectroscopy to evaluate bacterial influence on DOK cell behavior and metabolism. Results showed significant downregulation of only two markers, mTOR and COX2, in the presence of L. salivarius, suggesting a mild antitumorigenic effect. Conversely, P. gingivalis induced marked upregulation of PIK3CA, AKT, ALOX5, and VEGF, consistent with pro-oncogenic activity. Functionally, P. gingivalis enhanced DOK cell migration at 6 h, while L. salivarius did not affect it. Additionally, L. salivarius-treated cells exhibited reduced reactive oxygen species (ROS) production compared to those exposed to P. gingivalis. Raman micro-spectroscopy further revealed distinct metabolic alterations between the two co-cultures. Conclusions: Together, these findings indicate that L. salivarius may exert mild protective, anti-oncogenic effects on dysplastic oral keratinocytes, whereas P. gingivalis promotes oncogenic changes.