Gemcitabine-induced pancreatic cancer cell death is associated with MST1/Cyclophilin D mitochondrial complexation

• Gemcitabine-resistant pancreatic cancer cells express low level of MST1 and Cyp-D.
• Gemcitabine activates MST1 through ROS production in pancreatic cancer cells.
• MST1 and Cyp-D are important for gemcitabine-induced cell death.
• Gemcitabine induces MST1 mitochondrial translocation and Cyp-D complexation.
• CsA inhibits Gemcitabine-induced MST1-Cyp-D mitochondrial association and cell death.

The pancreatic adenocarcinoma remains the most aggressive human malignancy with an extremely low 5-year overall survival. Postoperative gemcitabine could significantly delay recurrence after complete resection of pancreatic cancer. However, the underlying mechanisms are not fully understood. The chemo-resistance factors against gemcitabine still need further characterizations. Here we studied the mechanism of gemcitabine-induced pancreatic cancer cell death by focusing on mammalian sterile 20-like kinase 1 (MST1) and cyclophilin D (Cyp-D). We found that MST1 and Cyp-D expressions were significantly lower in gemcitabine-resistant pancreatic cancer tissues and cell lines. In vitro, gemcitabine activated MST1 through reactive oxygen species (ROS) production, which was prevented by antioxidant n-acetyl-cysteine (NAC). We found that gemcitabine-activated MST1 translocated to mitochondria and formed a complex with the local protein Cyp-D. Gemcitabine-induced cell death was alleviated by MST1 or Cyp-D shRNA silencing, but was aggravated by MST1 or Cyp-D over-expression. Further, cyclosporin A (CsA), the Cyp-D inhibitor, prevented gemcitabine-induced MST1/Cyp-D mitochondrial complexation and cancer cell death. We suggest that gemcitabine-induced death of pancreatic cancer cells requires MST1/Cyp-D mitochondrial complexation.