Chronic nicotine inhibits the therapeutic effects of gemcitabine on pancreatic cancer in vitro and in mouse xenografts

Aim of study: Smoking is an established risk factor for pancreatic cancer and nicotine replacement therapy (NRT) often accompanies chemotherapy. The current study has tested the hypothesis that chronic exposure to low dose nicotine reduces the responsiveness of pancreatic cancer to the leading therapeutic for this cancer, gemcitabine. Methods: The effects of chronic nicotine (1 mu m/L) on two pancreatic cancer cell lines in vitro and in a xenograft model were assessed by immunoassays, Western blots and cell proliferation assays. Results: Exposure in vitro to nicotine for 7 days inhibited the gemcitabine-induced reduction in viable cells, gemcitabine-induced apoptosis as indicated by reduced expression of cleaved caspase-3 while inducing the phosphorylation of signalling proteins extracellular signal-regulated kinase (ERK), v-akt thymoma viral oncogene homolog (protein kinase B, AKT) and Src. Nicotine (1 mu m/L) in the drinking water for 4 weeks significantly reduced the therapeutic response of mouse xenografts to gemcitabine while reducing the induction of cleaved caspase-3 and the inhibition of phosphorylated forms of multiple signalling proteins by gemcitabine in xenograft tissues. Conclusions: Our experimental data suggest that continued moderate smoking and NRT may negatively impact therapeutic outcomes of gemcitabine on pancreatic cancer and that clinical studies in cancer patients are now warranted. (C) 2012 Elsevier Ltd. All rights reserved.