Novel off-target effect of tamoxifen--inhibition of acid ceramidase activity in cancer cells.
Biochim Biophys Acta
; 1831(12): 1657-64, 2013 Dec.
Article
em En
| MEDLINE
| ID: mdl-23939396
ABSTRACT
Acid ceramidase (AC), EC 3.5.1.23, a lysosomal enzyme, catalyzes the hydrolysis of ceramide to constituent sphingoid base, sphingosine, and fatty acid. Because AC regulates the levels of pro-apoptotic ceramide and mitogenic sphingosine-1-phosphate, it is considered an apt target in cancer therapy. The present study reveals, for the first time, that the prominent antiestrogen, tamoxifen, is a pan-effective AC inhibitor in the low, single digit micromolar range, as demonstrated in a wide spectrum of cancer cell types, prostate, pancreatic, colorectal, and breast. Prostate cancer cells were chosen for the detailed investigations. Treatment of intact PC-3 cells with tamoxifen produced time- and dose-dependent inhibition of AC activity. Tamoxifen did not impact cell viability nor did it inhibit AC activity in cell-free assays. In pursuit of mechanism of action, we demonstrate that tamoxifen induced time-, as early as 5min, and dose-dependent, as low as 5µM, increases in lysosomal membrane permeability (LMP), and time- and dose-dependent downregulation of AC protein expression. Assessing various protease inhibitors revealed that a cathepsin B inhibitor blocked tamoxifen-elicited downregulation of AC protein; however, this action failed to restore AC activity unless assayed in a cell-free system at pH4.5. In addition, pretreatment with tamoxifen inhibited PC-3 cell migration. Toremifene, an antiestrogen structurally similar to tamoxifen, was also a potent inhibitor of AC activity. This study reveals a new, off-target action of tamoxifen that may be of benefit to enhance anticancer therapies that either incorporate ceramide or target ceramide metabolism.
Palavras-chave
AC; AO; Acid ceramidase; Antiestrogen; Ceramide; GC; LMP; Lysosomal protease; N-oleoylethanolamine; NOE; PBS; PBST; PMSF; S1-P; SK; Tamoxifen; acid ceramidase; acridine orange; glucosylceramide; lysosomal membrane permeability; phenylmethylsulfonyl fluoride; phosphate-buffered saline; phosphate-buffered saline with Tween-20; sphingosine 1-phosphate; sphingosine kinase
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Tamoxifeno
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Moduladores Seletivos de Receptor Estrogênico
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Inibidores Enzimáticos
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Ceramidase Ácida
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Lisossomos
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Antineoplásicos
Limite:
Female
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Humans
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Male
Idioma:
En
Revista:
Biochim Biophys Acta
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Estados Unidos