Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8301956 | Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids | 2015 | 10 Pages |
Abstract
The triphenylethylene antiestrogen, tamoxifen, can be an effective inhibitor of sphingolipid metabolism. This off-target activity makes tamoxifen an interesting ancillary for boosting the apoptosis-inducing properties of ceramide, a sphingolipid with valuable tumor censoring activity. Here we show for the first time that tamoxifen and metabolite, N-desmethyltamoxifen (DMT), block ceramide glycosylation and inhibit ceramide hydrolysis (by acid ceramidase, AC) in human acute myelogenous leukemia (AML) cell lines and in AML cells derived from patients. Tamoxifen (1-10 μM) inhibition of AC in AML cells was accompanied by decreases in AC protein expression. Tamoxifen also depressed expression and activity of sphingosine kinase 1 (SphK1), the enzyme-catalyzing production of mitogenic sphingosine 1-phosphate (S1-P). Results from mass spectroscopy showed that tamoxifen and DMT (i) increased the levels of endogenous C16:0 and C24:1 ceramide molecular species, (ii) nearly totally halted production of respective glucosylceramide (GC) molecular species, (iii) drastically reduced levels of sphingosine (to 9% of control), and (iv) reduced levels of S1-P by 85%, in vincristine-resistant HL-60/VCR cells. The co-administration of tamoxifen with either N-(4-hydroxyphenyl)retinamide (4-HPR), a ceramide-generating retinoid, or a cell-deliverable form of ceramide, C6-ceramide, resulted in marked decreases in HL-60/VCR cell viability that far exceeded single agent potency. Combination treatments resulted in synergistic apoptotic cell death as gauged by increased Annexin V binding and DNA fragmentation and activation of caspase-3. These results show the versatility of adjuvant triphenylethylene with ceramide-centric therapies for magnifying therapeutic potential in AML. Such drug regimens could serve as effective strategies, even in the multidrug-resistant setting.
Keywords
C6-ceramideP-gpGCsGADPHPDMPATCCSphK1DMTPPMPTLCN-DesmethyltamoxifenTriphenylethylenesPBSAMLFBSPVDF4-HPRDMSOESI-MS/MSP-glycoproteinSDS–PAGEsphingomyelinSphingosine kinase 1sphingosine 1-phosphateacid ceramidasesodium dodecyl sulfate–polyacrylamide gel electrophoresistamoxifenanalysis of varianceANOVApolyvinyl difluorideDimethyl sulfoxideceramidefetal bovine serumcombination indexFenretinideleukemiaAcute myelogenous leukemiaSphingolipid metabolismAmerican Type Culture CollectionPhosphate-buffered salinePropidium iodidehigh-performance liquid chromatographyHPLCthin-layer chromatographyglucosylceramideglucosylceramide synthaseglyceraldehyde 3-phosphate dehydrogenase
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Authors
Samy A.F. Morad, Su-Fern Tan, David J. Feith, Mark Kester, David F. Claxton, Thomas P. Jr., Brian M. Barth, Todd E. Fox, Myles C. Cabot,