Background: Plumbagin, a quinonoid constituent isolated from the root of Plumbago zeylanica L., has been proven to possess anti-tumor activity both in vitro and in vivo. However, its anti-tumor properties for human tongue carcinoma have not been reported. This study aimed to investigate the inhibitory effect and the underlying mechanism of plumbagin on the growth of human tongue carcinoma cells.
Material and Methods: Cell proliferation ability was detected by EdU incorporation assay and colony formation assay. Cell-cycle distribution was determined by flow cytometric analysis using propidium iodide (PI) staining. Cellular apoptosis was then evaluated by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Western blotting was applied to assay the expression of Bax and Bcl-2.
Results: Plumbagin inhibited the growth and proliferation of Tca8113 cells in vitro in a concentration- and time-dependent manner. The cell cycles of plumbagin-treated Tca8113 cells were arrested at the G2/M phase. Cells treated with plumbagin presented the characteristic morphological changes of apoptosis. The ratio of Bax/Bcl-2 was raised by plumbagin in a concentration-dependent manner.
Conclusions: These results indicate that plumbagin induces the apoptosis of Tca8113 cells through mitochondria-mediated pathway.

Keywords: Signal Transduction - drug effects, Time Factors, Naphthoquinones - pharmacology, Mitosis - drug effects, Mitochondria - metabolism, G2 Phase Cell Cycle Checkpoints - drug effects, Drug Screening Assays, Antitumor, Dose-Response Relationship, Drug, Deoxyuridine - metabolism, Cell Survival - drug effects, Cell Shape - drug effects, Cell Proliferation - drug effects, Cell Line, Tumor, Apoptosis - drug effects, Tongue Neoplasms - pathology, Tumor Stem Cell Assay, bcl-2-Associated X Protein - metabolism