O-GlcNAcylation-inducing treatments inhibit estrogen receptor α expression and confer resistance to 4-OH-tamoxifen in human breast cancer-derived MCF-7 cells.
O-GlcNAcylation (addition of N-acetyl-glucosamine on serine or threonine residues) is a post-translational modification that regulates stability, activity or localization of cytosolic and nuclear proteins. O-linked N-acetylgluocosmaine transferase (OGT) uses UDP-GlcNAc, produced in the hexosamine biosynthetic pathway to O-GlcNacylate proteins. Removal of O-GlcNAc from proteins is catalyzed by the β-N-Acetylglucosaminidase (OGA). Recent evidences suggest that O-GlcNAcylation may affect the growth of cancer cells. However, the consequences of O-GlcNAcylation on anti-cancer therapy have not been evaluated. In this work, we studied the effects of O-GlcNAcylation on tamoxifen-induced cell death in the breast cancer-derived MCF-7 cells. Treatments that increase O-GlcNAcylation (PUGNAc and/or glucosoamine) protected MCF-7 cells from death induced by tamoxifen. In contrast, inhibition of OGT expression by siRNA potentiated the effect of tamoxifen on cell death. Since the PI-3 kinase/Akt pathway is a major regulator of cell survival, we used BRET to evaluate the effect of PUGNAc+glucosamine on PIP3 production. We observed that these treatments stimulated PIP3 production in MCF-7 cells. This effect was associated with an increase in Akt phosphorylation. However, the PI-3 kinase inhibitor LY294002, which abolished the effect of PUGNAc+glucosamine on Akt phosphorylation, did not impair the protective effects of PUGNAc+glucosamine against tamoxifen-induced cell death. These results suggest that the protective effects of O-GlcNAcylation are independent of the PI-3 kinase/Akt pathway. As tamoxifen sensitivity depends on the estrogen receptor (ERα) expression level, we evaluated the effect of PUGNAc+glucosamine on the expression of this receptor. We observed that O-GlcNAcylation-inducing treatment significantly reduced the expression of ERα mRNA and protein, suggesting a potential mechanism for the decreased tamoxifen sensitivity induced by these treatments. Therefore, our results suggest that inhibition of O-GlcNAcylation may constitute an interesting approach to improve the sensitivity of breast cancer to anti-estrogen therapy.
Institut Cochin, Université Paris Descartes, CNRS (UMR8104), Paris, France ; INSERM, U1016, Paris, France.
Shahzina
S
Kanwal
Yann
Y
Fardini
Patrick
P
Pagesy
Thierry
T
N'tumba-Byn
Cécile
C
Pierre-Eugène
Elodie
E
Masson
Cornelia
C
Hampe
Tarik
T
Issad
D000117:Acetylglucosamine / Q000031:analogs & derivatives / Q000494:pharmacology; D018931:Antineoplastic Agents, Hormonal / Q000494:pharmacology; D053898:Biosynthetic Pathways; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D047628:Estrogen Receptor alpha / Q000235:genetics* / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006595:Hexosamines / Q000096:biosynthesis; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D061986:MCF-7 Cells; D010091:Oximes / Q000494:pharmacology; D048448:Phenylcarbamates / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology*
D018931:Antineoplastic Agents, Hormonal; D047628:Estrogen Receptor alpha; D006595:Hexosamines; D010091:Oximes; D048448:Phenylcarbamates; D020845:Selective Estrogen Receptor Modulators; D013629:Tamoxifen; C068836:N-acetylglucosaminono-1,5-lactone O-(phenylcarbamoyl)oxime; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D000117:Acetylglucosamine