Activation and Role of MAP Kinases in 15d-PGJ₂-Induced Apoptosis in the Human Pancreatic Cancer Cell Line MIA PaCa-2

Aim: We have previously reported that 15-deoxy-Δ ^12,14-prostaglandin J₂ (15d-PGJ₂), a potent ligand for peroxisome proliferator-activated receptor γ (PPARγ), induces caspase-mediated apoptosis in human pancreatic cancer cell lines. Mitogen-activated protein kinases (MAPKs) are known to regulate apoptosis in various cancers. The purpose of this study was to investigate the role of MAPKs (ERK, JNK, and p38) in 15d-PGJ₂-induced pancreatic cancer cell apoptosis. Methodology: The effect of 15d-PGJ₂ on MAPK activity was investigated by kinase assays using the human pancreatic cancer cell line MIA PaCa-2. Western blot analysis was performed to analyze phosphorylation of MAPKs, activation of caspases and poly ADP-ribose polymerase (PARP) cleavage. Apoptosis was evaluated by caspase-3 enzymatic activity and DNA fragmentation assay. Results: 15d-PGJ₂ activated all 3 MAPKs in a dose- and time-dependent fashion. SB202190, an inhibitor of p38, prevented 15d-PGJ ₂-induced activation of caspase-8, -9, and -3 and significantly decreased apoptosis. This effect was potentiated by SP600125, an inhibitor of JNK, although SP600125 alone had no significant effect on 15d-PGJ ₂-induced apoptosis. In contrast, PD98059, an inhibitor of MEK, significantly increased sensitivity to 15d-PGJ₂-induced apoptosis. Conclusions: 15d-PGJ₂ stimulates proapoptotic and antiapoptotic MAPK pathways. Sensitivity to 15d-PGJ₂-induced apoptosis is increased by ERK inhibition but decreased by inhibition of p38.