Gamma-amino Butyric Acid (GABA) Prevents the Induction of Nicotinic Receptor-Regulated Signaling by Chronic Ethanol in Pancreatic Cancer Cells and Normal Duct Epithelia

Pancreatic cancer has a high mortality rate and alcoholism is a risk factor independent of smoking. We have shown that nicotinic acetylcholine receptors (nAChR) regulate pancreatic ductal epithelia and pancreatic ductal adenocarcinoma (PDAC) cells in an autocrine fashion by stimulating their production of the stress neurotransmitters noradrenaline and adrenaline that signal through beta-adrenergic receptors (beta-AR). Our current study has investigated the modulation of this autocrine regulatory loop by chronic ethanol and explored the potential prevention of these effects by g-amino butyric acid (GABA). Using MTT assays, cell migration assays, Western blotting, immunoassays, and gene knockdown of individual nAChRs in two PDAC cell lines and in immortalized human pancreatic duct epithelial cells, our data show that treatment for seven days with ethanol induced the protein expression and sensitivity of nAChRs alpha 3, alpha 5, and alpha 7 resulting in increased production of noradrenaline and adrenaline, which drive proliferation and migration via cyclic AMP (cAMP)-dependent signaling downstream of beta-ARs. Treatment with GABA prevented all of these responses to chronic ethanol, reducing cell proliferation and migration below base levels in untreated cells. Our findings suggest that alcoholism induces multiple cAMP-dependent PDAC stimulating signaling pathways by upregulating the protein expression and sensitivity of nAChRs that regulate stress neurotransmitter production. Moreover, our data identify GABA as a promising agent for the prevention of PDAC in individuals at risk due to chronic alcohol consumption. Cancer Prev Res; 6(2); 139-48. (C)2012 AACR.