Antitumor Activity of a Bupleurum chinense-Derived Vesicle-like Particle Preparation in MOC1 Oral Squamous Cell Carcinoma Models

Background/Objectives: This study evaluated the antitumor activity of a Bupleurum chinense-derived extracellular vesicle-like particle (BC-EVLP) preparation in MOC1 oral squamous cell carcinoma (OSCC) models. Methods: Fresh roots were processed by differential centrifugation, filtration, ultracentrifugation, and sucrose density-gradient separation. The preparation was characterized by transmission electron microscopy, nanoparticle tracking analysis, and total protein measurement. Cellular association, viability, ROS-associated fluorescence, mitochondrial membrane potential, and Annexin V-FITC/PI staining were assessed. Cell viability was also compared after exposure to equal added volumes of the preparation or pre-gradient ultracentrifugation supernatant. Female C57BL/6 mice bearing syngeneic MOC1 tumors received peritumoral treatment every 3 days for 14 days, followed by tumor histology. Results: The preparation contained nanoscale vesicle-like structures, with median and mean particle diameters of 162.0 and 191.9 nm. DiI-associated fluorescence was detected in MOC1 cells after 4 h. Treatment reduced cell viability and was associated with increased DCF fluorescence, a lower JC-1 red/green ratio, and increased Annexin V-positive fractions. The BC-EVLP preparation reduced cell viability more than the supernatant at equal added volumes, although the higher-volume supernatant treatment retained partial activity. High-dose treatment attenuated tumor growth in vivo, and representative tumor sections showed less densely cellular areas. Conclusions: The BC-EVLP preparation exhibited antitumor activity in the tested MOC1 models. The active constituents and the relative contributions of vesicular and non-vesicular components remain unresolved.