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. This evidence concerns the gene C1GALT1C1 and cancer.