Disialyl-Lewis a (the structure and biosynthesis are shown in Figure 1), originally isolated from a colon cancer metastasis [67], was then found expressed in normal colon mucosa and down-regulated in colon cancer, due to the down-regulation of cognate α2,6sialyltransferase ST6GALNAC6, leading to the conclusion that CA19.9 was specifically expressed in colon cancer due to the lack of the second sialylation step [45]. Here, ST6GALNAC6 is linked to colonic neoplasm.