Activator Protein-1 Has an Essential Role in Pancreatic Cancer Cells and Is Regulated by a Novel Akt-Mediated Mechanism
Activator protein-1 (AP-1) regulates the expression of several genes involved in human tumorigenesis. However, there is little known about this transcription factor in pancreatic ductal adenocarcinoma. We recently found high levels of AP-1-binding activities and multiple AP-1/DNA complexes containing c-Jun,JunD,Fra1,and Fra2 in pancreatic cancer cells. Transient transfection assays indicated that AP-1 was functional and capable of transactivating its gene targets. Furthermore,a c-Jun transactivation mutant inhibited anchorage-dependent and anchorage-independent proliferation,suggesting that AP-1 had an essential role in pancreatic cancer cells. Our study also uncovered a novel mechanism by which protein kinase Akt controls c-Jun activity in pancreatic cancer cells. Indeed, distinct from its known ability to induce c-fos and fra1 and to stabilize c-Jun,Akt appeared to directly regulate the transcriptional activity of c-Jun independently of the phosphorylation sites targeted by c-Jun NH2-terminal kinase (Ser63/Ser 73) and glycogen synthase kinase-3 (Thr239). Our data also suggest that growth factors might use this Akt-regulated mechanism to potently induce c-Jun targets such as cyclin D1. Collectively,our findings indicate that AP-1 has an important function in pancreatic cancer cells and provide evidence for a previously unknown Akt-mediated mechanism of c-Jun activation.
Shin, Sonyo; Asano, Takayuki; Yao, Yixin; Zhang, Ronghua; Claret, Francois Xavier; Korc, Murray; Sabapathy, Kanaga; Menter, David G.; Abbruzzese, James L.; and Reddy, Shrikanth A.G.. 2009. Activator Protein-1 Has an Essential Role in Pancreatic Cancer Cells and Is Regulated by a Novel Akt-Mediated Mechanism. Molecular Cancer Research. Vol.7(5). 745-754. https://doi.org/10.1158/1541-7786.MCR-08-0462 PMID: 19435822 ISSN: 1541-7786