Bacterial extracellular vesicles from Streptococcus mutans drive OSCC progression through β-catenin signaling.

Oral squamous cell carcinoma (OSCC) is an aggressive malignancy in which microbial dysbiosis is increasingly recognized as a contributing factor, yet the pathogenic potential of bacterial extracellular vesicles (EVs) remains poorly defined. To determine whether Streptococcus mutans-derived EVs (SmEVs) influence OSCC progression, we isolated and characterized SmEVs from ATCC 35,668 and examined their effects in CAL-27 cells and a nude-mouse xenograft model. SmEVs were readily internalized by OSCC cells, enhancing their proliferative, migratory, and invasive capacities in vitro. Transcriptomic analysis revealed that SmEV exposure reshaped the CAL-27 gene expression landscape, prominently enriching the Wnt/β-catenin signaling pathway, accompanied by increased activation of β-catenin, TCF7, and FOSL1/Fra-1 in both cultured cells and xenograft tumors. Functional loss-of-experiments further demonstrated that β-catenin is critically required for these effects, as its silencing abrogated SmEV-induced proliferation, migration, and activation of the TCF7/Fra-1 axis. DIA proteomics identified a broad array of SmEV proteins, and in silico docking highlighted several abundant, cancer-associated candidates with strong predicted interactions with β-catenin. In vivo, co-administration of SmEVs accelerated tumor growth and reinforced activation of the β-catenin axis. Collectively, these findings provide the first evidence that S. mutans-derived EVs promote OSCC progression through β-catenin-driven transcriptional programs and identify specific vesicular proteins as candidate mediators, offering new insights into microbe-derived factors as potential diagnostic or therapeutic targets in OSCC.