Benzo[a]pyrene and nicotine impair epidermal growth factor mediated cellular functions of buccal mucosa

This study investigated the effect of two major ingredients in cigarette smoke, benzo[a]pyrene (BP) and nicotine, on epidermal growth factor (EGF) receptor binding and EGF-mediated cellular functions in rat buccal mucosa. Rat buccal tissue was incubated in DMEM in the absence (control) and presence of 10 microM BP or nicotine for 2.5 h at 25 degrees C. There were no significant differences in [125I]EGF binding to the buccal mucosal membranes between the control and treatment groups. Protein tyrosine kinase assay showed that EGF stimulated phosphorylation of a 170-kDa protein band in the controls, but not in the BP- and nicotine-treated samples. The basal [3H]thymidine incorporations were not significantly different between the groups. Nevertheless, addition of 5 nM EGF increased [3H]thymidine incorporation by 22% in the control, but not in the BP- or nicotine-treated group. The results demonstrate that BP and nicotine change the buccal mucosal functions associated with alteration of EGF receptor.