CHRM1 and malignant colon neoplasm: First, we tested the effects of McN-A-343, a M1R selective agonist developed over 60 years ago [26], on well-characterized H508 human colon cancer cells that express M3R at relatively higher levels than M1R (M1Rlow; Figure 2A) and whose rates of proliferation respond robustly to treatment with non-subtype-selective muscarinic agonists like acetylcholine and carbamylcholine (carbachol) [23].