Effect of triptolide on gemcitabine-mediated apoptosis in pancreatic cancer cell lines.

Abstract

e22043 Background: Pancreatic cancer is notorious for its resistance to anticancer drug. gemcitabine, the most effective anticancer drug currently available for palliative chemotherapy in pancreatic cancer patients, hardly achieves clinically satisfactory response rates. Therefore, it is urgent to develop novel agents that overcome drug resistance of pancreatic cancer. In this study, we demonstrated for the first time that triptolide, a diterpenoid triepoxide purified from the Chinese herb Tripterygium wilfordii Hook F, can enhance gemcitabine-mediated apoptosis in human pancreatic cancer cell lines (AsPC-1 and PANC-1). Methods: Pancreatic cells were treated with gemcitabine or triptolide alone, and combination of them, cell viability was measured by MTT, and apoptotic cells were assessed by flow cytometry for Annexin V/PI staining and western blot for cleaved caspase-3, 8, 9 and PARP. To explore the mechanism of enhancement of triptolide and gemcitabine, proteomic approach was used to screen the related apoptosis factors. Results: Triptolide demonstrated toxicity on pancreatic cancer cell lines with the IC50 of 25-40 nM. The combination of triptolide (IC30 concentration) and gemcitabine enhanced the cytotoxicity significantly compared to gemcitabine alone. Combination index (CI) indicated the effect of triptolide plus gemcitabine was synergistic. Furthermore, pancreatic cancer cells treated with triptolide plus gemcitabine exhibited increased apoptosis, as evidenced by stronger Annexin V/ PI staining, higher levels of pro-apoptotic proteins including cleaved caspases and activated PARP compared to cells treated with gemcitabine alone. In the mechanism study, vimentin, a mesenchymal marker, was screened out to be correlated with enhanced apoptosis induced by triptolide plus gemcitabine. Conclusions: 1) Triptolide has a potent therapeutic effect on pancreatic cancer cell lines; 2) the combination of triptolide with gemcitabine enhances the apoptosis in vitro, low concentration of TPL showed synergistic effect with gemcitabine; 3) The enhanced apoptosis induced by triptolide plus gemcitabine is correlated with vimentin expression inhibited by triptolide.