title: Glucagon-like peptide-1 receptor activation inhibits growth and augments apoptosis in murine CT26 colon cancer cells.
abstract: Obesity, accompanying or independent of type 2 diabetes mellitus (T2DM), is associated with higher rates of malignancy. Hence, there is considerable interest in understanding whether therapies used to treat obese patients with T2DM impact cancer cell growth. Glucagon-like peptide-1 (GLP-1) is produced in enteroendocrine cells and secreted after meal ingestion. GLP-1 regulates blood glucose through multiple mechanisms, principally inhibition of glucagon and stimulation of insulin secretion. GLP-1 also exerts independent effects promoting cell growth and survival, and sustained activation of GLP-1 receptor (GLP-1R) signaling in rodent thyroid glands leads to C-cell hyperplasia and medullary thyroid cancer. Hence, whether therapies based on GLP-1R activation modify growth or survival of cancer cells is of ongoing interest. We studied the biological actions of GLP-1 in mouse CT26 colon cancer cells that express a functional GLP-1R. The GLP-1R agonist exendin (Ex)-4 (exenatide) increased intracellular cAMP levels and inhibited the activity of signaling kinases glycogen synthase kinase 3 and ERK1/2 in CT26 cells. The Ex-4-induced inactivation of glycogen synthase kinase 3, but not ERK1/2, was dependent on protein kinase A and blocked by the GLP-1R antagonist Ex(9-39). Furthermore, Ex-4 altered cell morphology, induced apoptosis, and inhibited proliferation of CT26 cells in vitro. Moreover Ex-4 decreased CT26 colony formation in soft agar and augmented apoptosis induced by irinotecan. Twice-daily treatment of CT26 tumor-bearing BALB/c mice with Ex-4 for 2 wk increased tumor apoptosis. Hence, GLP-1R activation reduces growth and survival in CT26 colon cancer cells that express the endogenous classical GLP-1R.
authors.affiliation: Department of Medicine, Samuel Lunenfeld Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada M5G 1X5.
authors.forename: Jacqueline A
authors.initials: JA
authors.lastname: Koehler
authors.forename: Taylor
authors.initials: T
authors.lastname: Kain
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Drucker
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D003106:Colon / Q000187:drug effects / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D000077270:Exenatide; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D052216:Glucagon-Like Peptide 1; D000067757:Glucagon-Like Peptide-1 Receptor; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D006801:Humans; D051379:Mice; D010455:Peptides / Q000494:pharmacology; D018027:Receptors, Glucagon / Q000819:agonists / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D014688:Venoms / Q000494:pharmacology
chemical_list: C000593833:GLP1R protein, human; C000593834:Glp1r protein, mouse; D000067757:Glucagon-Like Peptide-1 Receptor; D010455:Peptides; D018027:Receptors, Glucagon; D014688:Venoms; D052216:Glucagon-Like Peptide 1; D000077270:Exenatide; D000242:Cyclic AMP; D048049:Extracellular Signal-Regulated MAP Kinases; D038362:Glycogen Synthase Kinase 3