The tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone stimulates proliferation of immortalized human pancreatic duct epithelia through beta-adrenergic transactivation of EGF receptors.
OBJECTIVE
Pancreatic ductal adenocarcinoma is an aggressive smoking-associated human cancer in both men and women. The nicotine-derived 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is thought to contribute to the development of these neoplasms in smokers through genotoxic effects. However, NNK has been recently identified as an agonist for both beta(1)- and beta(2)-adrenergic receptors. Binding of NNK to these receptors stimulates proliferation of pulmonary and pancreatic adenocarcinomas cells in vitro and in hamster models. The goal of this study was to elucidate the NNK effects on the signal transduction pathways downstream of both beta(1)- and beta(2)-adrenergic receptors in immortalized human pancreatic HPDE6-c7 cells.


METHODS
The HPDE6-c7 cells are developed from normal pancreatic duct epithelial cells which are the putative cells of origin of pancreatic ductal adenocarcinoma. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) cell proliferation assays, Western blot and cyclic AMP assays were employed to demonstrate the effects of NNK and other beta(1)- and beta(2)-adrenergic agonists and antagonist treatments on these cells.


RESULTS
MTT cell proliferation assays demonstrated that NNK and the classic beta-adrenergic agonist, isoproterenol, increased cell proliferation in HPDE6-c7 cells. Western blot and cyclic AMP assays demonstrated that NNK treatments also resulted in: (1) transactivation of the epidermal growth factor receptor, EGFR, (2) an increase in intracellular cyclic AMP accumulation, and (3) phosphorylation of mitogen-activated protein kinase, Erk1/2. The proliferative response to NNK and isoproterenol were inhibited by the use of beta-blockers (propranolol), and the inhibitors of adenylyl cyclase (SQ 22536), EGFR-specific tyrosine kinase (AG 1478) and Erk (PD 98059).


CONCLUSIONS
These findings suggest that the NNK -mediated beta-adrenergic receptor transactivation of the EGFR and phosphorylation of Erk1/2 in immortalized human pancreatic duct epithelial cells as a novel mechanism might contribute to the development of tobacco-associated pancreatic carcinogenesis.
Askari
Minoo D F
MD
Experimental Oncology Laboratory, Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, Knoxville, 37996, USA.
Tsao
Ming-Sound
MS
Schuller
Hildegard M
HM
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D015153:Blotting, Western; D002273:Carcinogens / Q000378:metabolism / Q000494:pharmacology*; D021441:Carcinoma, Pancreatic Ductal / Q000209:etiology; D002461:Cell Line, Transformed; D049109:Cell Proliferation / Q000187:drug effects*; D000242:Cyclic AMP / Q000378:metabolism; D004848:Epithelium / Q000187:drug effects* / Q000378:metabolism; D066246:ErbB Receptors / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000187:drug effects / Q000378:metabolism; D009602:Nitrosamines / Q000009:adverse effects / Q000378:metabolism / Q000494:pharmacology*; D010183:Pancreatic Ducts / Q000187:drug effects; D010190:Pancreatic Neoplasms / Q000209:etiology; D010766:Phosphorylation; D018343:Receptors, Adrenergic, beta-2 / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D015533:Transcriptional Activation / Q000187:drug effects; D014026:Nicotiana
D000318:Adrenergic beta-Agonists; D002273:Carcinogens; D009602:Nitrosamines; D018343:Receptors, Adrenergic, beta-2; C016583:4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone; D000242:Cyclic AMP; D066246:ErbB Receptors; D020929:Mitogen-Activated Protein Kinase Kinases; D007545:Isoproterenol