BDNF and lung cancer: Since the objective of this work was to examine regulation of cisplatin resistance in lung cancer cells by nicotine, BDNF, and a β-adrenergic receptor blocker, and since no effects were found upon incubation of the non-cancerous cell line, BEAS-2B, with either nicotine, BDNF, or propranolol under our experimental conditions, A549 and H1299 cells were used for the following experiments in this study.