Pancreatic cancer is highly resistant to current chemotherapy agents. We therefore examined the effects of triptolide (a diterpenoid triepoxide) on pancreatic cancer growth and local-regional tumor spread using an orthotopic model of pancreatic cancer. We have recently shown that an increased level of HSP70 in pancreatic cancer cells confers resistance to apoptosis and that inhibiting HSP70 induces apoptosis in these cells. In addition, triptolide was recently identified as part of a small molecule screen, as a regulator of the human heat shock response. Therefore, our aims were to examine the effects of triptolide on (a) pancreatic cancer cells by assessing viability and apoptosis, (b) pancreatic cancer growth and local invasion in vivo, and (c) HSP70 levels in pancreatic cancer cells. Incubation of PANC-1 and MiaPaCa-2 cells with triptolide (50-200 nmol/L) significantly reduced cell viability, but had no effect on the viability of normal pancreatic ductal cells. Triptolide induced apoptosis (assessed by Annexin V, caspase-3, and terminal nucleotidyl transferase-mediated nick end labeling) and decreased HSP70 mRNA and protein levels in both cell lines. Triptolide (0.2 mg/kg/d for 60 days) administered in vivo decreased pancreatic cancer growth and significantly decreased local-regional tumor spread. The control group of mice had extensive local invasion into adjacent organs, including the spleen, liver, kidney, and small intestine. Triptolide causes pancreatic cancer cell death in vitro and in vivo by induction of apoptosis and its mechanism of action is mediated via the inhibition of HSP70. Triptolide is a potential therapeutic agent that can be used to prevent the progression and metastases of pancreatic cancer.

Background & Aims Pancreatic adenocarcinoma, among the most lethal human malignancies, is resistant to current chemotherapies. We have previously shown that triptolide inhibits the growth of pancreatic cancer cells in vitro and prevents tumor growth in vivo. This study investigates the mechanism by which triptolide kills pancreatic cancer cells, which has not been previously studied. Methods Cells were treated with triptolide and viability and caspase-3 activity were measured using colorimetric assays. Annexin V, propidium iodide and acridine orange staining were measured by flow cytometry. Immunofluorescence was used to monitor the localization of cytochrome c and LC3 proteins. Caspase-3, Atg5 and Beclin1 levels were downregulated by exposing cells to their respective siRNA. Results We show that triptolide induces apoptosis in MiaPaCa-2, Capan-1 and BxPC-3 cells and autophagy in S2-013, S2-VP10 and Hs766T cells. Triptolide-induced autophagy has a pro-death effect, requires autophagy-specific genes, atg5 or beclin1, and is associated with the inactivation of the Akt/mTOR/p70S6K pathway and the upregulation of the ERK1/2 pathway. Inhibition of autophagy in S2-013 and S2-VP10 cells results in cell death via the apoptotic pathway whereas inhibition of both autophagy and apoptosis rescues cell death. Conclusions This study shows, for the first time, that triptolide kills pancreatic cancer cells by two different pathways. It induces caspase-dependent apoptotic death in MiaPaCa-2, Capan-1 and BxPC-3 and caspase-independent autophagic death in metastatic cell lines, S2-013, S2-VP10 and Hs766T, thereby making it an attractive chemotherapeutic agent against a broad spectrum of pancreatic cancers.

Background & Aims-Heat shock proteins (HSPs) are highly conserved and serve a multitude of functions that mediate cell survival. HSP70, the only inducible form of the 70-kilodalton subfamily of HSPs, is overexpressed in pancreatic cancer cells and has been shown to inhibit caspase-dependent apoptosis. We aimed to elucidate the mechanism by which HSP70 inhibits apoptosis in cancer cells.

Pancreatic cancer is a the four leading cause of cancer related deaths and is adisease with poor prognosis. It is refractory to standard chemotherapeutic drugs or to novel treatment modalities, making it imperative to find new treatments. In this study, using both primary and metastatic pancreatic cancer cell lines, we have demonstrated that the flavonoid myricetin induced pancreatic cancer cell death in vitro via apoptosis, and caused a decrease in PI3 kinase activity. In vivo, treatment of orthotopic pancreatic tumors with myricetin resulted in tumor regression and decreased metastatic spread. Importantly, myricetin was non-toxic, both in vitro and in vivo, underscoring its use as a therapeutic agent against pancreatic cancer.