Abstract
Aberrant expression of O-glycans is a hallmark of epithelial cancers. Mucin type O-glycosylation is initiated by a large family of UDP-GalNAc:polypeptide N-acetyl-galactosaminyltransferases (GalNAc-Ts), that target different proteins and are differentially expressed in cells and organs. Here we investigated the expression patterns of all of the GalNAc-Ts in colon cancer by analysing transcriptomic data. We found that GalNAc-T6 was highly upregulated in colon adenocarcinomas but absent in normal-appearing adjacent colon tissue. The results were verified by immunohistochemistry, suggesting that GalNAc-T6 plays a role in colon carcinogenesis. To investigate the function of GalNAc-T6 in colon cancer, we used precise gene targeting to produce isogenic colon cancer cell lines with a knockout/-rescue system for GalNAc-T6. GalNAc-T6 expression was associated with a cancer-like, dysplastic growth pattern, whereas GalNAc-T6 knockout cells showed a more normal differentiation pattern, reduced proliferation, normalized cell-cell adhesion, and formation of crypts in tissue cultures. O-glycoproteomic analysis of the engineered cell lines identified a small set of GalNAc-T6-specific targets, suggesting that this isoform has unique cellular functions. In support of this notion, the genetically and functionally closely related GalNAc-T3 homologue did not shown compensatory functionality for effects observed for GalNAc-T6. Taken together, these data strongly suggest that aberrant GalNAc-T6 expression and site-specific glycosylation is involved in oncogenic transformation.
Original language | English |
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Journal | The Journal of Biological Chemistry |
Volume | 293 |
Pages (from-to) | 1298-1314 |
ISSN | 0021-9258 |
DOIs | |
Publication status | Published - 2018 |