C1GALT1C1 and colorectal carcinoma: Most studies have confirmed that aberrant O‐glycosylation mediated by the loss of functional Cosmc contributes to tumour progression and metastasis in a broad range of human cancers including CRC.4, 9, 18 Here we questioned whether the tumour‐promoting effects of Cosmc overexpression were also due to aberrant O‐glycosylation.