| Summary: | 博士 === 國立臺灣大學 === 解剖學暨細胞生物學研究所 === 102 === β1,4-N-acetylgalactosaminyltransferase III (B4GALNT3) catalyzes the transfer of GalNAc to any nonreducing terminal GlcNAc-β on N- and O-glycans, resulting in the synthesis of GalNAcβ1-4GlcNAc (LacdiNAc) structure. Although we previously showed that B4GALNT3 overexpression increased colon cancer cell malignant phenotypes in vitro and tumorigenesis in vivo, the underlying mechanism is poorly understood. Immunohistochemistry showed that B4GALNT3 was upregulated in colorectal tumors compared with their surrounding non-tumor colorectal tissues and was associated with poor survival of colorectal cancer patients. B4GALNT3 overexpression enhanced EGF-induced migration and invasion in HCT116 and SW480 cells. Knockdown of B4GALNT3 reduced EGF-induced migration and invasion in HCT115 and HT29 cells. The effects of B4GALNT3 on migration and invasion induced by 10% FBS were blocked with erlotinib, an EGFR inhibitor. Moreover, overexpression of B4GALNT3 increased EGF-induced sphere formation, whereas B4GALNT3 knockdown reduced cell malignant phenotypes. Wisteria floribunda agglutinin (WFA) pull down assays showed that B4GALNT3 primarily decorated the LacdiNAc structure on the N-glycans of EGFR. B4GALNT3 overexpressing cells enhanced EGF-induced phosphorylation of EGFR and its downstream signaling pathway. Overexpression of B4GALNT3 in colon cancer cells altered neither the HGF-induced motility and glycosylation of MET nor the bFGF-induced sphere forming ability. Our results suggest that B4GALNT3 regulates cancer stemness and the invasive properties of colon cancer cells through modifying EGFR glycosylation and signaling. Our findings provide a novel strategy for colorectal cancer therapy by inhibiting B4GALNT3.
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