Survival regulation in pancreatic cancer cells by c-Jun

Over 90% of human pancreatic cancers harbor an activating point mutation in the K-ras gene at codon 12. However, it is not clear whether all downstream K-ras are activated and which downstream contributes to the cell survival and proliferation of pancreatic cancer cells. MEK kinase I (MEKK1)-c-Jun N-terminal kinase (JNK)-c-Jun pathway has an important role in cell proliferation, survival and apoptosis in various cells. We previously demonstrated that the dominant negative form of MEKKI (DN-MEKK) inhibits the survival of human pancreatic cancer cell lines. In this study we investigated whether JNK-c-Jun, the downstream pathway of DN-MEKK, affects the survival of human pancreatic cancer cell lines. Colony formation assays indicated that c-Jun failed to inhibit the survival of pancreatic cancer cells, whereas c-Jun remarkably inhibited the cell survival of non-pancreatic cancer cells. Reporter gene assays using Gal4-c-Jun and gel retardation assays indicated that c-Jun functions were activated in growing pancreatic cancer cells. These results revealed that c-Jun activation does not prevent the cell survival of pancreatic cancer cells in contrast to non-pancreatic cancer cells. It appears that MEKKI-JNK-c-Jun pathway fails to act as a negative regulator for the cell survival of pancreatic cancer cells. Greater understanding of these mechanisms may be helpful in the treatment of pancreatic cancer.