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Schledwitz A, Sundel MH, Alizadeh M, Hu S, Xie G, Raufman JP. Differential Actions of Muscarinic Receptor Subtypes in Gastric, Pancreatic, and Colon Cancer. Int J Mol Sci 2021; 22:ijms222313153. [PMID: 34884958 PMCID: PMC8658119 DOI: 10.3390/ijms222313153] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 12/01/2021] [Accepted: 12/02/2021] [Indexed: 12/17/2022] Open
Abstract
Cancers arising from gastrointestinal epithelial cells are common, aggressive, and difficult to treat. Progress in this area resulted from recognizing that the biological behavior of these cancers is highly dependent on bioactive molecules released by neurocrine, paracrine, and autocrine mechanisms within the tumor microenvironment. For many decades after its discovery as a neurotransmitter, acetylcholine was thought to be synthesized and released uniquely from neurons and considered the sole physiological ligand for muscarinic receptor subtypes, which were believed to have similar or redundant actions. In the intervening years, we learned this former dogma is not tenable. (1) Acetylcholine is not produced and released only by neurons. The cellular machinery required to synthesize and release acetylcholine is present in immune, cancer, and other cells, as well as in lower organisms (e.g., bacteria) that inhabit the gut. (2) Acetylcholine is not the sole physiological activator of muscarinic receptors. For example, selected bile acids can modulate muscarinic receptor function. (3) Muscarinic receptor subtypes anticipated to have overlapping functions based on similar G protein coupling and downstream signaling may have unexpectedly diverse actions. Here, we review the relevant research findings supporting these conclusions and discuss how the complexity of muscarinic receptor biology impacts health and disease, focusing on their role in the initiation and progression of gastric, pancreatic, and colon cancers.
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Affiliation(s)
- Alyssa Schledwitz
- Department of Medicine, Division of Gastroenterology & Hepatology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (A.S.); (M.A.); (S.H.); (G.X.)
| | - Margaret H. Sundel
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA;
| | - Madeline Alizadeh
- Department of Medicine, Division of Gastroenterology & Hepatology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (A.S.); (M.A.); (S.H.); (G.X.)
- The Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Shien Hu
- Department of Medicine, Division of Gastroenterology & Hepatology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (A.S.); (M.A.); (S.H.); (G.X.)
- VA Maryland Healthcare System, Baltimore, MD 21201, USA
| | - Guofeng Xie
- Department of Medicine, Division of Gastroenterology & Hepatology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (A.S.); (M.A.); (S.H.); (G.X.)
- VA Maryland Healthcare System, Baltimore, MD 21201, USA
- Marlene and Stewart Greenebaum Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Jean-Pierre Raufman
- Department of Medicine, Division of Gastroenterology & Hepatology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (A.S.); (M.A.); (S.H.); (G.X.)
- VA Maryland Healthcare System, Baltimore, MD 21201, USA
- Marlene and Stewart Greenebaum Comprehensive Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Correspondence: ; Tel.: +1-410-328-8728
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