Growth Inhibitory Effect of Palatine Tonsil-derived Mesenchymal Stem Cells on Head and Neck Squamous Cell Carcinoma Cells

OBJECTIVES Mesenchymal stem cells (MSCs) play an important role in the development and growth of tumor cells. However, the effect of human MSCs on the growth of human tumors is not well understood. The purpose of this study is to confirm the growth effect of palatine tonsil-derived MSCs (TD-MSCs) on head and neck squamous cell carcinoma (HNSCC) cell lines and to elucidate the mechanism of their action. METHODS TD-MSCs were isolated from patient with chronic tonsillitis and tonsillar hypertrophy. Two human HNSCC cell lines (PNUH-12 and SNU-899) were studied and cocultured with isolated palatine tonsil-derived MSC. The growth inhibitory effect of MSCs on HNSCC cell lines was tested through methylthiazolyldiphenyl-tetrazolium (MTT) assay. The apoptosis induction effect of MSCs on cell lines was assessed with flow cytometry and reverse transcriptase (RT)-PCR. RESULTS Palatine tonsil-derived MSCs exhibited a growth inhibitory effect on both cell lines. Cell cycle analysis showed an accumulation of tumor cells predominantly in G0/G1 phase with an increase in concentration of TD-MSCs, which was confirmed by increased mRNA expression of cell cycle negative regulator p21. Apoptosis of tumor cells increased significantly as concentration of cocultured TD-MSCs increased. Additionally, mRNA expression of caspase 3 was upregulated with increased concentration of TD-MSCs. CONCLUSION TD-MSCs have a potential growth inhibitory effect on HNSCC cell lines in vitro by inducing apoptotic cell death and G1 phase arrest of cell lines.