GlcNAcylation, a dynamic posttranslational modification, is involved in a wide range of biological processes and some human diseases. Although there is emerging evidence that some tumor-associated proteins are modified by GlcNAcylation, the role of GlcNAcylation in tumor progression remains unclear. Here, we show that GlcNAcylation enhances the migration/invasion of breast cancer cells in vitro and lung metastasis in vivo. The decrease of cell surface E-cadherin is the molecular mechanism underlying GlcNAcylation-induced breast cancer metastasis. p120 and β-catenin, but not E-cadherin, are GlcNAcylated; the GlcNAcylation of p120 and β-catenin might play roles in the decrease of cell surface E-cadherin. Moreover, immunohistochemistry analysis indicated that the global GlcNAcylation level in breast tumor tissues is elevated significantly as compared with that in the corresponding adjacent tissues; further, GlcNAcylation was significantly enhanced in metastatic lymph nodes compared with their corresponding primary tumor tissues. This is the first report to clearly elucidate the roles and mechanisms whereby GlcNAcylation influences the malignant properties of breast cancer cells. These results also suggest that GlcNAcylation might be a potential target for the diagnosis and therapy of breast cancer. Cancer Res; 70(15);
O-GlcNAc is a monosaccharide attached to serine or threonine hydroxyl moieties on numerous nuclear and cytoplasmic proteins; O-GlcNAcylation is dynamically regulated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Although recent studies have shown that O-GlcNAcylation plays essential roles in breast cancer progression, it is also necessary to know whether O-GlcNAcylation is involved in other types of human cancer. In this study, O-GlcNAcylation levels and the expressions of OGT and OGA in human lung and colon cancer tissues were examined by immunohistochemistry analysis. We found that O-GlcNAcylation as well as OGT expression was significantly elevated in the cancer tissues compared with that in the corresponding adjacent tissues. Additionally, the roles of O-GlcNAcylation in the malignancy of lung and colon cancer were investigated in vitro. The results showed that O-GlcNAcylation markedly enhanced the anchorage-independent growth of lung and colon cancer cells; O-GlcNAcylation could also enhance lung and colon cancer invasion in a context-dependent manner. All together, this study suggests that O-GlcNAcylation might play important roles in lung and colon cancer formation and progression, and may be a valuable target for diagnosis and therapy of cancer.
SIRT1 is the most evolutionarily conserved mammalian sirtuin, and it plays a vital role in the regulation of metabolism, stress responses, genome stability, and ageing. As a stress sensor, SIRT1 deacetylase activity is significantly increased during stresses, but the molecular mechanisms are not yet fully clear. Here, we show that SIRT1 is dynamically modified with O-GlcNAc at Ser 549 in its carboxy-terminal region, which directly increases its deacetylase activity both in vitro and in vivo. The O-GlcNAcylation of SIRT1 is elevated during genotoxic, oxidative, and metabolic stress stimuli in cellular and mouse models, thereby increasing SIRT1 deacetylase activity and protecting cells from stress-induced apoptosis. Our findings demonstrate a new mechanism for the activation of SIRT1 under stress conditions and suggest a novel potential therapeutic target for preventing age-related diseases and extending healthspan.
Abstract. O-GlcNAc is an O-linked β-N-acetylglucosamine moiety attached to the side-chain hydroxyl of a serine or threonine residue in numerous cytoplasmic and nuclear proteins. In this study, we detected the level of O-GlcNAc in prostate, liver and pancreatic cancer tissues, and found that the global O-GlcNAc modification also known as O-GlcNAcylation, is specifically increased in prostate cancer tissues compared to corresponding adjacent tissues. In addition, we found that global O-GlcNAcylation is increased in prostate cancer cells and not in benign prostatic hyperplasia (BPH) epithelial cells. O-GlcNAc enhanced the anchorage-independent growth and the migratory/invasive ability of prostate cancer cells. More importantly, we provide here, for the first time to the best of our knowledge, direct evidence that increased O-GlcNAcylation induces malignant transformation of nontumorigenic (BPH) cells. Furthermore, our study suggested that inhibiting the formation of the E-cadherin/catenin/cytoskeleton complex may underly the O-GlcNAc-induced prostate cancer progression. Overall, these findings indicated that O-GlcNAcylation is increased in prostate, but not in liver and pancreatic cancer tissues, and that O-GlcNAc can enhance the malignancy of prostate cancer cells. IntroductionNumerous nuclear and cytoplasmic proteins have been found modified with O-β-N-acetylglucosamine (O-GlcNAc) at the hydroxyl moiety of serine or threonine residues. This moiety is dynamically added and removed by the O-GlcNAc transferase (OGT) and the O-GlcNAcase (OGA) enzymes, respectively (1). UDP-GlcNAc is the donor substrate of OGT, and is biosynthesized through the hexosamine pathway (HBP). The HBP flux is highly dependent on glucose and glutamine, with ~3-5% of total glucose entering this pathway (2). O-GlcNAc is a sensor of intracellular glucose metabolism, since the intracellular level of UDP-GlcNAc is the main regulatory factor for the activity of OGT (3). O-GlcNAcylation is altered in metabolism-associated diseases, such as type II diabetes (4-6), Alzheimer's disease (7) and cancer (8). Therefore, abnormal O-GlcNAcylation may play critical roles in these pathological processes.Aberrant metabolism is a hallmark of cancer. Most cancer cells show increased rates of glucose and glutamine utilization, up to 200-fold higher than those observed in the healthy cells they originate from, and predominantly produce energy through glycolysis followed by lactic acid fermentation (9,10). As a glycolytic pathway, HBP can enhance the level of UDP-GlcNAc, and thus, the activity of OGT, which may lead to an increase in the global O-GlcNAc level (summed over all proteins) in cancer cells. We have previously demonstrated that the global O-GlcNAc level is increased in breast, lung and colon cancer tissues as compared to respective adjacent tissues (11,12). In addition, other research groups have shown that O-GlcNAcylation is increased in breast, prostate and pancreatic cancer cell lines (13-15). However, whether increased O-GlcNAcylation is universal in ...
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