Inhibition of laryngeal cancer stem cells by tetrandrine

Cancer stem cells play a fundamental role in the growth, metastasis, recurrence, and chemoresistance of cancers of various origins; therefore, targeting these cells may prospectively help to eradicate cancer cells from patients. In this study, the effect of tetrandrine on the proliferation of CD133-positive (CD133) Hep-2 cells was examined to characterize its potential for targeting cancer stem cells in laryngeal cancer.The stem cell population of Hep-2 cells was isolated by magnetic-activated cell sorting against CD133, treated with different concentrations of tetrandrine, and assessed for cell cycle progression, proliferation, and migration. The mechanism of tetrandrine inhibition was also investigated.Our in vitro assay indicated that 20 μg/ml tetrandrine significantly inhibited the viability of CD133 Hep-2 cells (P < 0.01). Further cell cycle profiling showed a nearly 50% reduction of the S-phase cells after tetrandrine treatment, suggesting that tetrandrine inhibited DNA synthesis as well as cell proliferation. At the molecular level, tetrandrine induced downregulation of Bcl-2 and simultaneous upregulation of Bax and caspase-3 as well as enhanced cell apoptosis.Our results demonstrated that tetrandrine inhibited the cell viability and proliferation of CD133 Hep-2 cells by reducing the number of cells in the S-phase of the cell cycle and enhancing cell apoptosis.