Figure 1.

Triptolide treatment results in growth arrest, and synergistically enhances the cytotoxicity of gemcitabine in pancreatic cancer cells. (A and B) BxPC-3 or PANC-1 cells were treated with vehicle control or triptolide at the indicated doses for up to 96 h. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The data are presented as the mean inhibition rate ± standard error from at least three independent experiments. (C and D) Gemcitabine IC₅₀ of BxPC-3 or PANC-1 cells was determined in the absence or presence of sequential triptolide treatment (gemcitabine followed by triptolide) (presented as the mean ± standard error). (E and F) BxPC-3 or PANC-1 cells were treated with gemcitabine (4 varying concentrations: 5, 10, 20 and 40 nM) or triptolide (3 varying concentrations: 6.25, 12.5 and 25 nM) alone or combined sequentially (12 combined groups). CI values were calculated with CalcuSyn software (Biosoft, Cambridge, UK). *P<0.05, **P<0.01 and ***P<0.001 vs. vehicle control. IC₅₀, half maximal inhibitory concentration; CI, combination index.