Figure 4.

Triptolide synergistically enhances gemcitabine-induced cell cycle arrest and DNA double-strand breaks by suppressing CHK1 expression in pancreatic cancer cells. (A and B) BxPC-3 or PANC-1 cells were treated initally with gemcitabine for 24 h, followed by treatment with triptolide for 48 h without washing off the gemcitabine. Cell cycle distribution was determined by propidium iodide staining and flow cytometric analysis. (C) BxPC-3 or PANC-1 cells were treated initially with gemcitabine for 24 h, followed by treatment with triptolide for 48 h without washing off the gemcitabine. Cells were harvested and whole cell lysates were prepared and subjected to immunoblot analysis of γH2AX, CHK1 and GAPDH. CHK1, checkpoint kinase 1; γH2AX, phospho-H2AX; GAPDH, glyceraldehyde 3-phosphate dehydrogenase. *P<0.05, **P<0.01, combined treatment vs. treatment with gemcitabine and triptolide.