ru-58668 and Multiple-Myeloma

Multiple myeloma (MM) is a malignancy characterized by the accumulation of tumoral plasma cells in bone marrow. This disease remains incurable and the development of new therapeutic strategies is urgently required. We have studied the effects of 2 selective estrogen receptor disrupters (SERDs), RU 58668 (RU) and ICI 182,780 (ICI) or pure antiestrogens (AEs) on MM cell lines. Both compounds have antimyeloma activity through either cell cycle arrest or induction of apoptosis. To analyze the molecular mechanisms of SERD action, we choose 2 differently responding cell lines as models. In LP-1 cells, RU blocked cell cycle at the G1 phase. RU treatment induced a rapid decrease of c-Myc, an upregulation of p27(Kip1), and the subsequent decreased activity of cyclin-dependent kinase, CDK6 and associated cyclin D3, impairing the inactivation of the retinoblastoma protein (pRb). In RPMI 8226 cells, RU induced apoptosis by recruiting endoplasmic reticulum- as well as mitochondria-associated caspases. Moreover, RU interfered with the NF-kappaB survival pathway, often deregulated in MM malignancy. Antimyeloma activities were observed in dexamethasone (Dex)- and RU-resistant cells when RU was combined with bortezomib; Dex and bortezomib being frequently used in MM therapy. RU induced the death of CD138+ cells purified from MM patients but not CD19+ normal cells obtained from tonsils. Therefore, RU mediates the inhibition of survival, the activation of apoptosis and finally potentiates anticancer drug. Those combinatory effects provide a basis for the potential use of pure AEs in MM treatment.

Topics: Antineoplastic Agents, Hormonal; Apoptosis; Blotting, Western; Boronic Acids; Bortezomib; Caspases; Cell Proliferation; Colorimetry; Cyclin D3; Cyclin-Dependent Kinase 6; Cyclin-Dependent Kinase Inhibitor p27; Cyclins; Drug Resistance, Neoplasm; Drug Synergism; Endoplasmic Reticulum; Estradiol; Estrogen Receptor Modulators; Flow Cytometry; G1 Phase; Humans; Immunoprecipitation; Mitochondria; Multiple Myeloma; NF-kappa B; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Pyrazines; Selective Estrogen Receptor Modulators; Signal Transduction; Tumor Cells, Cultured

In most of multiple myeloma (MM) cells, the "pure" antiestrogen (AE) RU 58668 (RU) induced either a G1-arrest (LP-1, OPM-2, NCI-H929, U266 cells) or apoptosis (RPMI 8226 cells). In RPMI 8226 cells, RU activates a caspase-dependent cell death pathway leading to the release of cytochrome c, the decrease of the essential MM survival factor Mcl-1, the cleavage of Bid and the activation of caspases-3 and -8. Incorporation of RU in pegylated cholesterol-containing liposomes allowed a controlled RU release, improving its anti-proliferative and apoptotic effects in cells. In RPMI 8226 xenografts, i.v. injected RU-liposomes but not free RU, exhibited antitumor activity. In vivo, RU-liposomes triggered the mitochondrial death pathway, concomitantly with a down-regulation of Mcl-1 and Bid cleavage. The decrease of CD34 immunoreactivity indicated a reduction of angiogenesis. The decrease of VEGF secretion in vitro supported a direct effect of RU on angiogenesis. These pro-apoptotic and antiangiogenic effects were explained by a prolonged exposure to the drug and to the endocytosis capacity of liposomes which might increase RU uptake and bypass a membrane export of free RU. Thus, these combined enhanced activities of RU-liposomes support that such a delivery of an AE may constitute a strategy of benefit for MM treatment.

Topics: Animals; Antineoplastic Agents; Apoptosis; B-Lymphocytes; Cell Line, Tumor; Cell Proliferation; Cells, Cultured; Delayed-Action Preparations; Drug Delivery Systems; Estradiol; Estrogen Antagonists; Estrogen Receptor Modulators; Female; Humans; Immunohistochemistry; Liposomes; Mice; Mice, Nude; Models, Biological; Multiple Myeloma; Palatine Tonsil; Xenograft Model Antitumor Assays