title: Extracellular calcium-sensing receptor/PTH knockout mice colons have increased Wnt/β-catenin signaling, reduced non-canonical Wnt signaling, and increased susceptibility to azoxymethane-induced aberrant crypt foci.
abstract: Epidemiological evidence suggests increased dietary calcium and dairy products reduce the onset of colon cancer. To understand a role of the colonic extracellular calcium-sensing receptor (CaSR) in calcium-mediated chemoprevention of colon cancer, we induced formation of aberrant crypt foci (ACF) caused by azoxymethane (AOM) injection in 'rescued' CaSR-/PTH- (C-/P-) double knockout colons compared with colons from control CaSR+/PTH+ (C+/P+) mice. C-/P- colonic epithelia had increased Wnt/β-catenin signaling as evidenced by 3-8-fold increases in Wnt3a, CyclinD1, and MMP-7 proteins compared with C+/P+ colonic epithelia. The C-/P- colonic epithelia had reduced Wnt5a and Ror2, and a three-fold increase in TNFR1 compared with C+/P+ epithelia. The C-/P- colons and small intestine had extensive neutrophil infiltration with myeloperoxidase (MPO) levels 18-fold higher then C+/P+ small intestine and colon. Saline-injected C-/P- colons had the same number of ACF/cm(2) as C+/P+ colons, which were injected with AOM. However, there were eight times more ACF/cm(2) in the C-/P- injected with AOM compared with C+/P+ colons, which received AOM. Together our results suggest both inflammation and Wnt/β-catenin signaling are increased in the epithelia of 'rescued' CaSR/PTH double knockout colons, and the capacity for non-canonical Wnt signaling through Wnt5a/Ror2 engagement is reduced. The loss of the colonic CaSR increased the number of ACF/cm(2) in response to AOM injection, suggesting colonic CaSR may mediate the chemoprotective effect of increased dietary calcium against colorectal cancer observed in humans.
authors.affiliation: Department of Biomedical and Molecular Sciences, GIDRU, Queen's University, Kingston, Ontario, Canada K7L 3N6. rjm5@queensu.ca
authors.forename: R John
authors.initials: RJ
authors.lastname: MacLeod
mesh_terms: D058739:Aberrant Crypt Foci / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001397:Azoxymethane; D015153:Blotting, Western; D003106:Colon / Q000737:chemistry / Q000378:metabolism / Q000473:pathology; D019938:Cyclin D1 / Q000378:metabolism; D020022:Genetic Predisposition to Disease; D007421:Intestine, Small / Q000737:chemistry / Q000378:metabolism / Q000473:pathology; D020783:Matrix Metalloproteinase 7 / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D010281:Parathyroid Hormone / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D057050:Receptor Tyrosine Kinase-like Orphan Receptors / Q000378:metabolism; D044169:Receptors, Calcium-Sensing / Q000235:genetics* / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism; D015398:Signal Transduction; D051153:Wnt Proteins / Q000378:metabolism; D000071818:Wnt-5a Protein; D060509:Wnt3A Protein / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
chemical_list: C495267:CTNNB1 protein, mouse; C530105:Ccnd1 protein, mouse; D010281:Parathyroid Hormone; D044169:Receptors, Calcium-Sensing; D047888:Receptors, Tumor Necrosis Factor, Type I; C506236:Tnfrsf1a protein, mouse; D051153:Wnt Proteins; D000071818:Wnt-5a Protein; D060509:Wnt3A Protein; C555511:Wnt3a protein, mouse; C438615:Wnt5a protein, mouse; D051176:beta Catenin; D019938:Cyclin D1; D009195:Peroxidase; D057050:Receptor Tyrosine Kinase-like Orphan Receptors; C477010:Ror2 protein, mouse; D020783:Matrix Metalloproteinase 7; D001397:Azoxymethane