Tyrosine nitration of c-SRC tyrosine kinase in human pancreatic ductal adenocarcinoma

During pancreatic tumorigenesis, the equilibrium between cell survival and cell death is altered, allowing aggressive neoplasia and resistance to radi ation and chemotherapy. Local oxidative stress is one mechanism regulating programmed cell death and growth and may contribute to both tumor progressi on and suppression. Our recent in situ immunohistochemical studies demonstr ated that levels of total nitrotyrosine, a footprint of the reactive nitrog en species peroxynitrite, are elevated in human pancreatic ductal adenocarc inomas. In this study, quantitative HPEC-EC techniques demonstrated a 21- t o 97-fold increase in the overall levels of nitrotyrosine of human pancreat ic tumor extracts compared to normal pancreatic extracts. Western blot anal ysis of human pancreatic tumor extracts showed that tyrosine nitration was restricted to a few specific proteins. Immunoprecipitation coupled with Wes tern analysis identified c-Src tyrosine kinase as a target of both tyrosine nitration and tyrosine phosphorylation. Peroxynitrite treatment of human p ancreatic carcinoma cells in vitro resulted in increased tyrosine nitration and tyrosine phosphorylation of c-Src kinase, increased (>2-fold) c-Src ki nase activity, and increased association be tween c-Src kinase and its down stream substrate cortactin. Collectively, these observations suggest that p eroxynitrite-mediated tyrosine nitration and tyrosine phosphorylation of c- Src kinase may lead to enhanced tyrosine kinase signaling observed during p ancreatic ductal adenocarcinoma growth and metastasis. (C) 2000 Academic Pr ess.