Silencing of O-GlcNAc transferase attenuated O-GlcNAcylation and metastatic potentials of melanoma cells through suppression of Akt-NFkB signaling pathway.

Abstract

O-GlcNAcylation is an important biological process in regulating the function of many nucleocytoplasmic proteins in cells.  Enhancement of O-GlcNAcylation was associated with cancer development and progression.  Here, we demonstrated the involvement of O-GlcNAcylation in melanoma metastasis.  Using the data from GEO database, we found that O-GlcNAcylation and its related enzymes, including glutamine fructose-6-phosphate amidotransferase (GFAT), O-GlcNAc transferase (OGT), and O-GlcNAcase (OGA); were elevated in metastatic melanoma compared with primary tumors and normal tissues.  Functional analyses in melanoma cell lines--MNT-1, SK-MEL-28, and A-375 showed that suppression of O-GlcNAcylation by siRNA against OGT significantly reduces the migration and invasion abilities of the cells.  Phosphorylation of Akt and NFkB was drastically suppressed after knockdown of OGT, suggesting the role of O-GlcNAcylation in regulating the Akt-NFkB signaling pathway.  In addition, we found that the NFkB target genes, such as ZEB-2 and MCT-1, were significantly upregulated in metastatic tumors compared with primary tumors.  MCT-1 expression in melanoma tissues was also correlated with O-GlcNAcylation level.  Taken together, we have demonstrated in this study the possible role of O-GlcNAcylation in controlling melanoma metastasis via upregulating MCT-1 expression through activation of Akt-NFkB signaling pathway.