siRNA directed against TrkA sensitizes human pancreatic cancer cells to apoptosis induced by gemcitabine through an inactivation of PI3K/Akt-dependent pathway

Objective To determine the effect of suppressing TrkA expression on pancreatic cancer chemosensitivity to gemcitabine and further disclose the role of PI3K/Akt signal transduction pathway in pancreatic cancer chemoresistance.Methods Human pancreatic cancer cell lines PANC-1,MIA-PaCa2 and ASPC-1 were studied.The expression and kinase activity of TrkA were determined by Western blot analysis and in vitro kinase assay,respectively.RNA interference was used to suppress TrkA expression.Gemcitabine-induced cytotoxicity was determined by tetrazolium reduction assay and caspase profiling was performed.The effect of TrkA-specific siRNA on PI3K/Akt activity was also quantified.Results TrkA expression and kinase activity in cell lines were directly correlated with gemcitabine chemoresistance.TrkA-specific siRNA suppressed TrkA expression and kinase activity,and furthermore increased gemcitabine-induced,caspase-mediated apoptosis.PI3K/Akt activity was decreased by suppression of TrkA expression.Conclusion TrkA is a determinant of pancreatic adenocarcinoma chemoresistance and PI3K/Akt is a key signaling component by which NGF activation of the TrkA signal transduction pathway protects pancreatic cancer cells from chemotherapy-induced cell death.