ic Oxide Inhibits the Proliferation and Invasion of creatic Cancer Cells through Degradation of Insulin

ownload ic oxide (NO), which plays a role in the posttranslational modification of proteins, exhibits tumoricidal y. However, the mechanism remains largely unclear. We investigated whether the regulation of insulin resubstrate (IRS)-1 protein expression and insulin/insulin-like growth factor (IGF) signaling by NO is inin the proliferation and invasion of pancreatic cancer cells. NO donor inhibited insulin/IGF-I–stimulated horylation of insulin receptor/IGF-I receptor, IRS-1, Akt/PKB, and glycogen synthase kinase-3β along with sed expression of IRS-1 protein in MIAPaCa-2 cells, whereas NO donor enhanced the phosphorylation of llular signal-regulated kinase-1/2. In contrast, a selective inducible nitric oxide synthase inhibitor, 1400W, lated the expression of IRS-1 protein and the phosphorylation of IRS-1, Akt/PKB, and glycogen synthase -3β, along with enhanced proliferation and invasion of Panc-1 cells expressing inducible nitric oxide se protein. NO donor induced IRS-1 protein reduction through increased ubiquitination and degradation. e detection of the site responsible for NO-induced ubiquitination, IRS-1 deletion mutant genes were transand overexpressed in MIAPaCa-2 cells. The results indicate that the COOH terminus of the IRS-1 protein ired for NO donor–induced ubiquitination and protein degradation. Cells stably transfected with COOHal deletion mutants of IRS-1 exhibited reduced IGF signaling and cell proliferation compared with vector transfected cells, with no influence of NO on IGF signaling and invasion, although stable transfectants ull-length IRS-1 protein exhibited remarkable NO-induced reduction in IGF signaling, cell proliferation, vasion. These findings indicate that NO inhibits the proliferation and invasion of pancreatic cancer cells, and in at least in part, through upregulation of IRS-1 protein degradation and resultant downregulation of the insulin/ IGF-I-Akt pathway. Mol Cancer Res; 8(8); 1152–63. ©2010 AACR.