文摘
Purpose. One of the angiogenic factors secreted from many pancreatic tumors is Interleukin-8 (IL-8). Several signaling pathways have been implicated in IL-8 expression. The purpose of this study was to examine the role of the protein tyrosine kinase, Src, in mediating IL-8 expression in pancreatic tumor cells. Experimental Design. Pancreatic adenocarcinoma cell lines were grown in vitro and maintained in standard culture medium. Stable transfections were achieved with a tetracycline-controlled gene expression system for expression of Src. Transient lipid-mediated DNA-transfection procedures were achieved with an NFκB promoter plasmid driving the expression of luciferase. Selective signal transduction inhibitors, PP2 (for Src Family), LY294002 (for PI3 kinase), PD98059 (for MEK), and SB203580 (for p38 MAPK), were added to cells to examine effects on IL-8 expression. Following incubation in 1 % serum, IL-8 expression in culture medium was determined by ELISA and expression and phosphorylation of specific signal transduction enzymes were determined by immunoblotting. Results. Significant (P < 0.005) dose-dependent decreases were observed in IL-8 expression by inhibiting Src family kinases with PP2. Inhibition of SFK also resulted in decreased phosphorylation of Akt, p38, and Erk1/2. In addition, significant (P < 0.005) dose-dependent decreases were observed in IL-8 expression by inhibiting Src-dependent signaling molecules Erk1/2, and p38, but not Akt phosphorylation. When the expression of Src was induced with doxycycline in the Tet-On system, there was a significant increase in IL-8 protein expression when compared to controls. Inhibition of Src activity did not result in decreases in NFκB transcriptional activity. Conclusions. Src protein tyrosine kinase activity correlates with IL-8 protein expression and regulates critical “downstream” signaling enzymes, p38, and Erk1/2 MAPKs, which contribute to expression of IL-8 in human pancreatic tumor cells. Src activity regulates IL-8 expression in an NFκB-independent manner. Src may be a target for therapeutic intervention of pancreatic adenocarcinoma.
