Acetylcholine release by human colon cancer cells mediates autocrine stimulation of cell proliferation.
Most colon cancers overexpress M3 muscarinic receptors (M3R), and post-M3R signaling stimulates human colon cancer cell proliferation. Acetylcholine (ACh), a muscarinic receptor ligand traditionally regarded as a neurotransmitter, may be produced by nonneuronal cells. We hypothesized that ACh release by human colon cancer cells results in autocrine stimulation of proliferation. H508 human colon cancer cells, which have robust M3R expression, were used to examine effects of muscarinic receptor antagonists, acetylcholinesterase inhibitors, and choline transport inhibitors on cell proliferation. A nonselective muscarinic receptor antagonist (atropine), a selective M3R antagonist (p-fluorohexahydro-sila-difenidol hydrochloride), and a choline transport inhibitor (hemicholinum-3) all inhibited unstimulated H508 colon cancer cell proliferation by approximately 40% (P<0.005). In contrast, two acetylcholinesterase inhibitors (eserine-hemisulfate and bis-9-amino-1,2,3,4-tetrahydroacridine) increased proliferation by 2.5- and 2-fold, respectively (P<0.005). By using quantitative real-time PCR, expression of choline acetyltransferase (ChAT), a critical enzyme for ACh synthesis, was identified in H508, WiDr, and Caco-2 colon cancer cells. By using high-performance liquid chromatography-electrochemical detection, released ACh was detected in H508 and Caco-2 cell culture media. Immunohistochemistry in surgical specimens revealed weak or no cytoplasmic staining for ChAT in normal colon enterocytes (n=25) whereas half of colon cancer specimens (n=24) exhibited moderate to strong staining (P<0.005). We conclude that ACh is an autocrine growth factor in colon cancer. Mechanisms that regulate colon epithelial cell production and release of ACh warrant further investigation.
Cheng
Kunrong
K
Division of Gastroenterology and Hepatology, Veterans Affairs Maryland Healthcare System, University of Maryland School of Medicine, Department of Pathology, 22 S. Greene St., N3W62, Baltimore, MD 21201, USA.
Samimi
Roxana
R
Xie
Guofeng
G
Shant
Jasleen
J
Drachenberg
Cinthia
C
Wade
Mark
M
Davis
Richard J
RJ
Nomikos
George
G
Raufman
Jean-Pierre
JP
D000109:Acetylcholine / Q000378:metabolism*; D000110:Acetylcholinesterase / Q000378:metabolism; D001285:Atropine / Q000494:pharmacology; D019898:Autocrine Communication / Q000187:drug effects; D018938:Caco-2 Cells; D049109:Cell Proliferation / Q000187:drug effects; D002794:Choline / Q000378:metabolism; D002795:Choline O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D018678:Cholinergic Agents / Q000494:pharmacology; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D003110:Colonic Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D004563:Electrochemistry; D019073:HT29 Cells; D006426:Hemicholinium 3 / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D026901:Membrane Transport Proteins / Q000187:drug effects / Q000378:metabolism; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010830:Physostigmine / Q000031:analogs & derivatives / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D043587:Receptor, Muscarinic M3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013619:Tacrine / Q000494:pharmacology
D018678:Cholinergic Agents; D002800:Cholinesterase Inhibitors; D026901:Membrane Transport Proteins; D018727:Muscarinic Antagonists; D010880:Piperidines; D012333:RNA, Messenger; D043587:Receptor, Muscarinic M3; C065637:choline transporter; C058297:4-fluorohexahydrosiladifenidol; D006426:Hemicholinium 3; D013619:Tacrine; D001285:Atropine; D010830:Physostigmine; D002795:Choline O-Acetyltransferase; D000110:Acetylcholinesterase; D002794:Choline; D000109:Acetylcholine