Taiwan Green Propolis Nanoparticles Induce Antiproliferation and Apoptosis in Oral Cancer Cells

Introduction: Taiwan green propolis (TGP) is rich in prenylflavonoids and exhibits antioxidant, antibacterial, antiviral, and antitumour properties. It induces apoptosis in various cancer cells, making it a highly promising natural medicine. Although the health benefits and food applications of TGP are widely recognised, no study has explored its effects on Taiwan oral cancer cells (OECM1). This study investigated whether TGP induces apoptosis in OECM1 cells. Methods: High-performance liquid chromatography (HPLC), thin-layer chromatography, and liquid chromatography/mass spectrometry were used to identify the components in TGP and the fruit peel of Macaranga tanarius. The inhibitory activities of TGP dissolved in DMSO (TGP_DMSO) and encapsulated in food-grade zein nanoparticles (TGP_NP) against OECM1 cells were compared using MTT assays. The morphological changes, cell cycle analysis, and protein expression profiles of OECM1 cells after the TGP treatments were performed using microscopy, flow cytometry, and Western blot, respectively. Results: An MTT assay of TGP_DMSO-treated OECM1 cells suggested an IC₅₀ of 12.6 µg/mL, demonstrating that TGP_DMSO exhibits significant cytotoxicity. Subsequent MTT assays revealed TGP_NP's cytotoxicity against OECM1 with an IC₅₀ of 11.6 µg/mL. Flow cytometry revealed that TGP_NP induced a cell arrest in S phase and DNA fragmentation. Western blotting analyses manifested an increase in Bax and cl-Casp9 and a decrease in Bcl2 and PARP. Conclusion: This study demonstrated that both TGP_DMSO and TGP_NP treatments induced apoptosis in OECM1 cells with a comparable IC₅₀. Notably, utilising edible zein as a nanoparticle carrier for TGP mitigates the cytotoxicity risk associated with DMSO, providing a novel and safe approach for cancer treatment.