Genetic ablation of M3 muscarinic receptors attenuates murine colon epithelial cell proliferation and neoplasia.
Colon epithelial cells express and most colon cancers overexpress M(3) muscarinic receptors (M(3)R). In human colon cancer cells, post-M(3)R signaling stimulates proliferation. To explore the importance of M(3)R expression in vivo, we used the azoxymethane-induced colon neoplasia model. Mice treated with weekly i.p. injection of saline [10 wild-type (WT) mice] or azoxymethane (22 WT and 16 M(3)R(-/-) mice) for 6 weeks were euthanized at 20 weeks. At week 20, azoxymethane-treated WT mice weighed approximately 16% more than M(3)R(-/-) mice (33.4 grams +/- 1.0 grams versus 27.9 grams +/- 0.5 grams; mean +/- SE, P < 0.001). In azoxymethane-treated M(3)R(-/-) mice, cell proliferation (BrdUrd staining) was reduced 43% compared with azoxymethane-treated WT mice (P < 0.05). Whereas control mice (both WT and M(3)R(-/-)) had no colon tumors, azoxymethane-treated WT mice had 5.3 +/- 0.5 tumors per animal. Strikingly, azoxymethane-treated M(3)R(-/-) mice had only 3.2 +/- 0.3 tumors per mouse (P < 0.05), a 40% reduction. Tumor volume in azoxymethane-treated M(3)R(-/-) mice was reduced 60% compared with azoxymethane-treated WT mice (8.1 mm(3) +/- 1.5 mm(3) versus 20.3 mm(3) +/- 4.1 mm(3); P < 0.05). Compared with WT, fewer M(3)R(-/-) mice had adenomas (6% versus 36%; P = 0.05), and M(3)R(-/-) mice had fewer adenocarcinomas per mouse (0.6 +/- 0.1 versus 1.7 +/- 0.4; P < 0.05). Eleven of 22 WT but no M(3)R(-/-) mice had multiple adenocarcinomas (P < 0.001). Compared with WT, azoxymethane-treated M(3)R-deficient mice have attenuated epithelial cell proliferation, tumor number, and size. M(3)R and post-M(3)R signaling are novel therapeutic targets for colon cancer.
Raufman
Jean-Pierre
JP
Division of Gastroenterology and Hepatology, VA Maryland Health Care System and Program in Oncology, Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, USA. jraufman@medicine.umaryland.edu
Samimi
Roxana
R
Shah
Nirish
N
Khurana
Sandeep
S
Shant
Jasleen
J
Drachenberg
Cinthia
C
Xie
Guofeng
G
Wess
Jürgen
J
Cheng
Kunrong
K
D000818:Animals; D001397:Azoxymethane / Q000494:pharmacology; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D003110:Colonic Neoplasms / Q000235:genetics*; D004847:Epithelial Cells / Q000166:cytology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D017403:In Situ Hybridization; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D008957:Models, Genetic; D043587:Receptor, Muscarinic M3 / Q000235:genetics*; D015398:Signal Transduction
D043587:Receptor, Muscarinic M3; D001397:Azoxymethane