It is possible that differential localization of MRs within cells comprising the tumor microenvironment also plays a role in discrepant effects; M3R is more consistently expressed throughout multiple tissue layers, including circular and longitudinal muscle, myenteric nerve cell bodies, and mucosal epithelial tissue, while M1R expression is largely restricted to myenteric and submucosal nerve cells and epithelial cells (Harrington et al., 2010). Here, CHRM1 is linked to neoplasm.