These observations motivated us to examine the role of M1R (Chrm1) expression in colon neoplasia and to determine whether knocking out both M1R (Chrm1) and M3R (Chrm3) in the same animal (hereafter called dual KO mice) would more effectively attenuate AOM-induced colon neoplasia than M3R (Chrm3) knockout alone. The gene discussed is CHRM3; the disease is infectious otitis media.