4-Hydroxytamoxifen inhibits proliferation of multiple myeloma cells in vitro through down-regulation of c-Myc, up-regulation of p27Kip1, and modulation of Bcl-2 family members.
OBJECTIVE
Multiple myeloma is an incurable B-cell malignancy requiring new therapeutic strategies. Our approach was to analyze the in vitro effects of a selective estrogen receptor modulator, 4-hydroxytamoxifen (4-OHT), on six multiple myeloma cell lines.


METHODS
Cultured multiple myeloma cells were treated with various 4-OHT concentrations and the cellular response was studied: cell proliferation, cell viability, induction of apoptosis, caspase activities, and expression of signaling proteins.


RESULTS
We found that pharmacologic concentrations of 4-OHT inhibit cell proliferation (4 of 6 cell lines). This inhibition is achieved by two independent events: a block at the G(1) phase of the cell cycle and the induction of apoptotic death. The cellular response to 4-OHT depends on the presence of functional estrogen receptors. 4-OHT treatment activates an intrinsic mitochondrial caspase-9-dependent pathway but not the Fas/FasL death pathway. Signaling pathways known to be involved in the survival and/or proliferation of multiple myeloma cells are not affected by 4-OHT treatment. 4-OHT-induced G(1) arrest is accompanied by the up-regulation of the cell cycle inhibitor p27(Kip1) and the down-regulation of c-Myc. Among the Bcl-2 family members tested, the proapoptotic BimS protein is induced whereas the antiapoptotic protein Mcl-1 is decreased.


CONCLUSIONS
Although the effects of 4-OHT are observed at micromolar concentrations, cellular mechanisms responsible for G(1) arrest, as well as apoptosis induction, are similar to those observed in breast cancer cells. Our data support the concept that 4-OHT may represent an alternative approach to inhibit proliferation and induce apoptosis of multiple myeloma cells.
Gauduchon
Juliette
J
UFR de Médecine, Université de Caen-Basse Normandie, CHU Côte de Nacre, 14032 Caen Cedex, France.
Gouilleux
Fabrice
F
Maillard
Sébastien
S
Marsaud
Véronique
V
Renoir
Jack-Michel
JM
Sola
Brigitte
B
D017209:Apoptosis / Q000187:drug effects; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects*; D050760:Cyclin-Dependent Kinase Inhibitor p27; D015536:Down-Regulation; D004965:Estrogen Antagonists / Q000494:pharmacology*; D016193:G1 Phase / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects; D009101:Multiple Myeloma / Q000378:metabolism* / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000819:agonists / Q000378:metabolism; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D018797:Cell Cycle Proteins; D004965:Estrogen Antagonists; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D011960:Receptors, Estrogen; D025521:Tumor Suppressor Proteins; D013629:Tamoxifen; D050760:Cyclin-Dependent Kinase Inhibitor p27; C016601:afimoxifene; C506433:CASP9 protein, human; D053453:Caspase 9; D020169:Caspases