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Multiple myeloma (MM) is a plasma-cell malignancy which remains incurable despite the recent emergence of multiple novel agents. Importantly, recent genetic and molecular analyses have revealed the complexity and heterogeneity of this disease, highlighting the need for therapeutic strategies to eliminate all clones. Moreover, the bone marrow microenvironment, including stromal cells and immune cells, plays a central role in MM pathogenesis, promoting tumor cell growth, survival, and drug resistance. New classes of agents including proteasome inhibitors, immunomodulatory drugs, monoclonal antibodies, and histone deacetylase inhibitors have shown remarkable efficacy; however, novel therapeutic approaches are still urgently needed to further improve patient outcomes. In this review, we discuss the recent advances and future strategies to ultimately develop MM therapies with curative potential. [ABSTRACT FROM AUTHOR]

Objectives: Alkyl-lysophospholipids are a novel class of antitumor agents. Perifosine is a novel alkyl-lysophospholipid that can induce apoptosis in multiple myeloma (MM) tumor cells, both in vitro and in vivo. We investigated the effects of perifosine on the peripheral blood, bone marrow, and spleen of mice inoculated with subcutaneous plasmacytomas. Methods: Immunocompromised mice were inoculated with myeloma cell lines and treated with oral perifosine in either a daily or weekly schedule, or with vehicle only. When plasmacytomas reached 2 cm, mice were sacrificed. Terminal blood was analyzed with a Coulter counter, and counts were confirmed by light microscopy. Marrow and spleen were also analyzed by light microscopy. Results: In control mice, mean hemoglobin was 12 g/dL, white blood cell (WBC) count 7 × 109/L, and mean platelet count was 292 × 109/L. In contrast, the respective values for mice treated with perifosine weekly were 11 g/dL, 9 × 109/L, and 944 × 109/L; and for mice treated with perifosine daily were 10 g/dL, 11 × 109/L, and 752 × 109/L. The increase in WBCs was due, predominantly, to a neutrophilia. Compared to control mice, perifosine treatment induced marrow hypercellularity and splenic white pulp expansion. Conclusions: These findings have clinical relevance because myeloid suppression is a dose-limiting toxicity of many cytotoxic agents, and myeloid hyperplasia is usually only observed in the setting of growth factor stimulation. Coupled with its remarkable in vitro MM cytotoxicity, these results strongly support the use of perifosine in clinical trials for patients with MM. [Copyright &y& Elsevier]

Discusses a study indicating that the induction of apoptosis in multiple myeloma cells is associated with activation of c-Jun NH[sub 2]-terminal kinase (JNK), translocation of JNK from cytosol to mitochondria and release of second mitochondria-derived activator of capcases (Smac) from mitochondria to cytosol. JNK blocking by dominant-negative mutant or cotreatment with specific JNK inhibitors, SP600125.

Carfilzomib, a recently FDA-approved proteasome inhibitor, has remarkable anti-myeloma (MM) activity. However, its effectiveness is limited by associated severe side-effects, short circulation half-life, and limited solubility. Here, we report the engineering of liposomal carfilzomib nanoparticles to overcome these problems and enhance the therapeutic efficacy of carfilzomib by increasing tumoral drug accumulation while decreasing systemic toxicity. In our design, carfilzomib was loaded into the bilayer of liposomes to yield stable and reproducible liposomal nanoparticles. Liposomal carfilzomib nanoparticles were efficiently taken up by MM cells, demonstrated proteasome inhibition, induced apoptosis, and exhibited enhanced cytotoxicity against MM cells. In vivo , liposomal carfilzomib demonstrated significant tumor growth inhibition and dramatically reduced overall systemic toxicity compared to free carfilzomib. Finally, liposomal carfilzomib demonstrated enhanced synergy in combination with doxorubicin. Taken together, this study establishes the successful synthesis of liposomal carfilzomib nanoparticles that demonstrates improved therapeutic index and the potential to improve patient outcome in MM. [ABSTRACT FROM AUTHOR]

Abstract: Over-expression of the protein Dickkopf-1 (Dkk1) has been associated with multiple myeloma bone disease. Previous reports with the use of anti-Dkk1 neutralizing Ab directed strategies have demonstrated a pro-anabolic effect with associated anti-myeloma activity in 2 in vivo mouse models. However new insights on the role of the wnt pathway in osteoclasts (OC) are emerging and the potential effect of a neutralizing Ab to Dkk1 in osteoclastogenesis remains to be elucidated. In order to better define the effect of an anti-Dkk1 neutralizing Ab on osteoclastogenesis and myeloma, we studied a novel anti-Dkk1 monoclonal Ab in our preclinical models. In vivo data confirmed the pro-anabolic and anti-MM effect. In vitro data in part confirmed the in vivo observation, suggesting an indirect anti-MM effect secondary to inhibition of osteoclastogenesis and thus the interaction between MM and bone microenvironment. However, when studies on osteoclastogenesis were extended to samples derived from MM patients, we observed a variable response to anti-Dkk1 treatment without correlation to expression of surface receptors for Dkk1 in OCs suggesting potential heterogeneity in the efficacy of such a strategy. In conclusion, Dkk1 is a promising target for the treatment of both MM and bone disease, and ongoing clinical studies will help elucidate its efficacy. [Copyright &y& Elsevier]

Summary: Bortezomib therapy has proven successful for the treatment of relapsed/refractory, relapsed, and newly diagnosed multiple myeloma (MM); however, dose-limiting toxicities and the development of resistance limit its long-term utility. Here, we show that P5091 is an inhibitor of deubiquitylating enzyme USP7, which induces apoptosis in MM cells resistant to conventional and bortezomib therapies. Biochemical and genetic studies show that blockade of HDM2 and p21 abrogates P5091-induced cytotoxicity. In animal tumor model studies, P5091 is well tolerated, inhibits tumor growth, and prolongs survival. Combining P5091 with lenalidomide, HDAC inhibitor SAHA, or dexamethasone triggers synergistic anti-MM activity. Our preclinical study therefore supports clinical evaluation of USP7 inhibitor, alone or in combination, as a potential MM therapy. [Copyright &y& Elsevier]

Summary: Multiple myeloma (MM) remains incurable despite novel therapies, suggesting the need for further identification of factors mediating tumorigenesis and drug resistance. Using both in vitro and in vivo MM xenograft models, we show that plasmacytoid dendritic cells (pDCs) in the bone marrow (BM) microenvironment both mediate immune deficiency characteristic of MM and promote MM cell growth, survival, and drug resistance. Microarray, cell signaling, cytokine profile, and immunohistochemical analysis delineate the mechanisms mediating these sequelae. Although pDCs are resistant to novel therapies, targeting Toll-like receptors with CpG oligodeoxynucleotides both restores pDC immune function and abrogates pDC-induced MM cell growth. Our study therefore validates targeting pDC-MM interactions as a therapeutic strategy to overcome drug resistance in MM. [Copyright &y& Elsevier]

Summary: Bortezomib therapy has proven successful for the treatment of relapsed and/or refractory multiple myeloma (MM); however, prolonged treatment is associated with toxicity and development of drug resistance. Here, we show that the novel proteasome inhibitor NPI-0052 induces apoptosis in MM cells resistant to conventional and Bortezomib therapies. NPI-0052 is distinct from Bortezomib in its chemical structure, effects on proteasome activities, mechanisms of action, and toxicity profile against normal cells. Moreover, NPI-0052 is orally bioactive. In animal tumor model studies, NPI-0052 is well tolerated and prolongs survival, with significantly reduced tumor recurrence. Combining NPI-0052 and Bortezomib induces synergistic anti-MM activity. Our study therefore provides the rationale for clinical protocols evaluating NPI-0052, alone and together with Bortezomib, to improve patient outcome in MM. [Copyright &y& Elsevier]

Objective: To determine the progression-free survival at 12 weeks, to evaluate the toxic effects, and to analyze the biological activity of thalidomide in patients with relapsed multiple myeloma (MM) after high-dose chemotherapy and stem cell transplantation. Patients and Methods: From 1999 to 2001, we performed a multicenter prospective phase 2 study in patients with MM that relapsed after high-dose chemotherapy and stem cell transplantation to evaluate the efficacy of oral thalidomide, with dose escalation from 200 to 600 mg/d over 12 weeks and a subsequent maintenance phase of 200 mg/d for up to 1 year. Outcome was correlated with serum and plasma levels of vascular endothelial growth factor and serum levels of tumor necrosis factor α, soluble intercellular adhesion molecule 1, interferon γ, interleukin (IL) 2, and IL-6 during treatment. Results: Thirty patients were treated (19 men and 11 women; median age, 58 years). The median number of prior therapies was 5, and the median duration from diagnosis of MM to study enrollment was 4.3 years. The 12-week progression-free survival rate was 67% (94% confidence interval [CI], 48%-86%). The observed response rate (partial response plus minor response) was 43% (95% CI, 28%-60%) with a median duration of 6 months. Attributable toxicities included constipation, fatigue, rash, and neuropathy, which was dose limiting in 8 patients (27%). Dose escalation from 200 to 600 mg/d was achieved in 50% of patients. Although responses were observed with lower doses, possibly eliminating the need to escalate the dose escalation. Some patients had disease progression while receiving the maintenance dose of 200 mg/d. Analysis of biomarker assays did not identify any biomarker associated with greater response, but a significant increase in levels of soluble intercellular adhesion molecule 1, IL-2, and interferon γ was seen with thalidomide therapy. Concusion: The optimal thalidomide dose varies, and adverse effects can be dose limiting. The dose of thalidomide therapy should be based on the individual patient to ensure that it is well tolerated and that a response is achieved. [ABSTRACT FROM AUTHOR]

Interleukin-6 (LI-6) is a known growth and survival factor in multiple myeloma via activation of extracellular signal-regulated kinase and phosphatidylinositol 3-kinase signaling cascade. In this report we show that Grb2-associated binder (Gab) family adapter proteins Gab1 and Gab2 are expressed by multiple myeloma cells; and that interleukin-6 induces their tyrosine phosphorylation and association with downstream signaling molecules. We further demonstrate that these events are Src family tyrosine kinase-dependent and specifically identify the role of hematopoietic cell kinase (Hck) as a new Gab family adapter protein kinase. Conversely, inhibition of Src family tyrosine kinases by the pyrazolopyrimidine PP2, as in kinase-inactive Hck mutants, significantly reduces IL-6-triggered activation of extracellular signal-regulated kinase and AKT-1, leading to significant reduction of multiple myeloma cell proliferation and survival. Taken together, these results delineate a key role for Hck-mediated phosphorylation of Gab1 and Gab2 docking proteins in IL-6-induced proliferation and survival of multiple myeloma cells and identify tyrosine kinases and downstream adapter proteins as potential new therapeutic targets in multiple myeloma. [ABSTRACT FROM AUTHOR]

Insulin-like growth factors and their receptor (IGF-1R) have been implicated in cancer pathophysiology. We demonstrate that IGF-1R is universally expressed in various hematologic (multiple myeloma, lymphoma, leukemia) and solid tumor (breast, prostate, lung, colon, thyroid, renal, adrenal cancer, retinoblastoma, and sarcoma) cells. Specific IGF-1R inhibition with neutralizing antibody, antagonistic peptide, or the selective kinase inhibitor NVP-ADW742 has in vitro activity against diverse tumor cell types (particularly multiple myeloma), even those resistant to conventional therapies, and triggers pleiotropic antiproliferative/proapoptotic molecular sequelae, delineated by global transcriptional and proteomic profiling. NVP-ADW742 monotherapy or its combination with cytotoxic chemotherapy had significant antitumor activity in an orthotopic xenograft MM model, providing in vivo proof of principle for therapeutic use of selective IGF-1R inhibitors in cancer. [Copyright &y& Elsevier]

Multiple myeloma (MM) is a clonal B-lymphocyte malignancy, which is characterized by the accumulation of terminally differentiated antibody-producing cells in the bone marrow. Because current treatments offer only a median survival of 3 years, investigators continue to search for novel therapeutic strategies to combat the disease. Rational drug design is enhanced by understanding MM cell proliferation and key signaling pathways employed. In addition, a model system for preclinical evaluation of novel therapeutics is critical. Our laboratory has developed MM cell lines to study drug action and resistance, cell proliferation, and apoptosis. These cell lines are widely used in MM research. From a single MM patient, three separate cell lines were established that parallel the progression of the disease. These three cell lines, designated MM1.S, MM1.RE, and MM1.RL, can be distinguished on the basis of their sensitivity to steroid hormones such as glucocorticoids (GCs). Utilization of these cell lines to study the etiology of MM, effects of chemotherapeutic agents, and development of clinical resistance, will provide us with vital information for the evolution of new and more efficacious therapeutics. The aim of this review is to summarize the morphological, biochemical, and growth characteristics of these cells, and to review the results from investigations of the MM.1 signaling pathways. This information will enhance the study, treatment, and eventual eradication of MM. [Copyright &y& Elsevier]

Examines the role of caveolin-1 in multiple myeloma cells. Demonstration that the caveolin-1 is expressed in multiple myeloma cells; Effect of cholesterol depletion of by beta-cyclodextrin; Finding that cholesterol depletion by beta-cyclodextrin abrogates both interleukin-6- and insulin-like growth factor-I-triggered multiple myeloma cell survival via negative regulation of caveolin-1.

: ObjectiveTo evaluate the anti-tumor potential of β-lapachone in multiple myeloma (MM) cell lines (U266, RPMI8226, and MM.1S); MM cell lines resistant to dexamethasone (MM.1R), melphalan (RPMI8226/LR5), doxorubicin (RPMI8226/DOX40), and mitoxantrone (RPMI8226/ MR20); and MM cells from patients (MM1-MM4).: Materials and MethodsCytotoxicity of β-lapachone was assessed by MTT and [3H]-thymidine uptake assays. Apoptosis was analyzed using propidium iodide staining, DNA fragmentation, TUNEL assay, caspase-9 colorimetric assay, and immunoblotting for caspase-3, poly (ADP-ribose) polymerase (PARP), and caspase-8 cleavage products. Paracrine growth of MM cells was assessed by [3H]-thymidine uptake in cultures of bone marrow stromal cells (BMSCs) and MM cells. Interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) secretion in the culture supernatants was measured by specific enzyme-linked immunosorbent assays (ELISAs).: Resultsβ-lapachone showed significant cytotoxicity in MM cells (IC50: 4–8 μM). In contrast, normal peripheral blood mononuclear cells (PBMCs) and BMSCs from MM patients were relatively resistant (IC50: 8–16 μM). IL-6 did not protect against β-lapachone–induced apoptosis in MM.1S cells, and dexamethasone showed additive cytotoxicity. β-lapachone also decreased binding of MM.1S cells to BMSCs; abrogated IL-6 and VEGF secretion triggered by adhesion of BMSCs to MM.1S cells; reduced proliferation of MM.1S cells adherent to BMSCs; and decreased intracellular adhesion molecule-1 (ICAM-1) expression on MM.1S cells. Furthermore, β-lapachone induced typical PARP cleavage, increased caspase-9 proteolytic activity, and activation of caspase-3, without activation of caspase-8 in U266 cells.: ConclusionThese studies provide a framework for clinical evaluation of β-lapachone to improve the outcome for patients with MM. [Copyright &y& Elsevier]