epothilone-a and Multiple-Myeloma

In this study, we investigated the in vitro and in vivo efficacy of patupilone (epothilone B, EPO906), a novel nontaxane microtubule stabilizing agent, in treatment of multiple myeloma (MM). Patupilone directly inhibited growth and survival of MM cells, including those resistant to conventional chemotherapies, such as the taxane paclitaxel. Patupilone induced G2M arrest of MM cells, with subsequent apoptosis. Interleukin-6 (IL-6) and insulin-like growth factor-1 (IGF-1), 2 known growth and survival factors for MM, did not protect MM.1S cells against patupilone-induced cell death. Proliferation of MM cells induced by adherence to bone marrow stromal cells (BMSCs) was also inhibited by patupilone and was paralleled by down-regulation of vascular endothelial growth factor (VEGF) secretion. Importantly, stimulation of cells from patients with MM, either with IL-6 or by adherence to BMSCs, enhanced the anti-proliferative and proapoptotic effects of patupilone. Moreover, patupilone was effective against MM cell lines that overexpress the MDR1/P-glycoprotein multidrug efflux pump. In addition, patupilone was effective in slowing tumor growth and prolonging median survival of mice that received orthotopical transplants with MM tumor cells. Taken together, these preclinical findings suggest that patupilone may be a safe and effective drug in the treatment of MM, providing the framework for clinical studies to improve patient outcome in MM.

Topics: Animals; Apoptosis; Bone Marrow Cells; Cell Cycle; Cell Proliferation; Cell Survival; Cells, Cultured; Coculture Techniques; Dexamethasone; Disease Models, Animal; Drug Resistance, Multiple; Epothilones; Humans; Insulin-Like Growth Factor I; Interleukin-6; Leukocytes, Mononuclear; Mice; Multiple Myeloma; Neoplasm Transplantation; Plasmacytoma; Time Factors; Xenograft Model Antitumor Assays

26-Trifluoro-(E)-9,10-dehydro-12,13-desoxyepothilone B [Fludelone (Flu)] has shown broad antitumor activity in solid tumor models. In the present study, we showed, in vitro, that Flu significantly inhibited multiple myeloma (MM) cell proliferation (with 1-15 nM IC50), whereas normal human bone marrow stromal cells (HS-27A and HS-5 lines) were relatively resistant (10- to 15-fold higher IC50). Cell-cycle analysis demonstrated that Flu caused G2/M phase arrest and induced cell apoptosis. After Flu treatment, caspase-3, -8, and -9 were activated, cytochrome c and second mitochondrial-derived activator of caspase were released to the cytosol, and c-Jun N-terminal kinase was activated, indicating that mitochondria were involved in the apoptosis. Flu toxicity to human hematopoietic stem cells was evaluated by CD34+ cell-apoptosis measurements and hematopoietic-progenitor assays. There was no significant toxicity to noncycling human CD34+ cells. We compared the efficacy of Flu with the epothilone analog 12,13-desoxyepothilone B (dEpoB) in xenograft nonobese diabetic/severe combined immunodeficient mouse models with subcutaneous or disseminated MM. Flu caused tumor disappearance in RPMI 8226 subcutaneous xenografts after only five doses of the drug (20 mg/kg of body weight), with no sign of relapse after 100 d of observation. In a disseminated CAG MM model, mice treated with Flu had a significantly decreased tumor burden, as determined by bioluminescence imaging, and prolonged overall survival vs. mice treated with dEpoB or vehicle control, indicating that Flu may be a promising agent for MM therapy.

Topics: Animals; Annexin A5; Apoptosis; Bone Marrow Cells; Caspase 8; Caspase 9; Caspases; Cell Cycle; Cell Line; Cell Proliferation; Dose-Response Relationship, Drug; Epothilones; Immunoblotting; Inhibitory Concentration 50; JNK Mitogen-Activated Protein Kinases; Mice; Multiple Myeloma