MUC5AC and colorectal carcinoma: In CRC, alterations of mucin O-glycans include reduced expression of core 3 (GlcNAcβ1-3GalNAcα-Ser/Thr) and core 4 [GlcNAcβ1-3(GlcNAcβ1-6)GalNAcα-Ser/Thr] based glycans (15, 16).