MUC5AC and cancer: MUC5AC is also expressed at low levels in the gastrointestinal tract and, surprisingly, expressed de novo, and upregulated in colonic mucus from cancer and ulcerative colitis patients (Bartman et al., 1999; Kocer et al., 2002; Byrd and Bresalier, 2004; Forgue-Lafitte et al., 2007; Bu et al., 2010).