BACKGROUND: YM155, which inhibits the anti-apoptotic protein survivin, is known to exert anti-tumor effects in various cancers. However, there were few reports describing the inhibitory effect of YM155 on human oral squamous cell carcinoma (OSCC) cells that highly express survivin. In this study, we investigated the anti-tumor effects of YM155 on OSCC cells and then examined its molecular mechanisms.

MATERIAL AND METHODS: SCC9 cells of OSCC were treated with series of concentrations of YM155 (0.01, 0.1, 1, and 10 ng/ml) for 6, 12, and 24 h. The effect of YM155 on survival of SCC9 cells was detected by MTT and colony formation assay. Cell apoptosis was detected by flow cytometric analysis and the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) assays. Western blot was used to detect the protein expression of survivin, p53, and PUMA. Caspase-3 activity was measured by cleavage of the caspase-3 substrate. To test the role of PUMA and caspase-3 on YM155-induced apoptosis and growth inhibition, the SCC9 cells was transfected with PUMA siRNA or caspase-3 siRNA or control siRNA for 16 h before YM155 (1 and 10 ng/ml) treatment for 24 h. In addition, we also investigated the effect of YM155 in an in vivo xenograft model.

RESULTS: Treatment of YM155 efficiently reduced survivin expression and increased PUMA expression and caspase-3 activation in the SCC9 cells. YM155 treatment resulted in 18–86% decrease in cell viability, 10–60% decrease in colony numbers, and 8–40% increase in cell apoptosis (p<0.05 and p<0.01). However, the induction of cell apoptosis growth inhibition was reversed by PUMA siRNA or caspase-3 transfection. In addition, animals treated with YM155 showed more than 60% tumor growth inhibition compared to the controls (p<0.05).

CONCLUSIONS: YM155 is a potent inhibitor of progression of SCC9 cells, which could be due to attenuation of survivin, and activation of the PUMA/caspase-3 cellular signaling processes. This study suggests that YM155 may be a potential molecular target with therapeutic relevance for the treatment of OSCC.

Keywords: Puma