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p53-related protein kinase (TP53RK, also known as PRPK) is an upstream kinase that phosphorylates (serine residue Ser15) and mediates p53 activity. Here we show that TP53RK confers poor prognosis in multiple myeloma (MM) patients, and, conversely, that TP53RK knockdown inhibits p53 phosphorylation and triggers MM cell apoptosis, associated with downregulation of c-Myc and E2F-1-mediated upregulation of pro-apoptotic Bim. We further demonstrate that TP53RK downregulation also triggers growth inhibition in p53-deficient and p53-mutant MM cell lines and identify novel downstream targets of TP53RK including ribonucleotide reductase-1, telomerase reverse transcrip-tase, and cyclin-dependent kinase inhibitor 2C. Our previous studies showed that immunomodulatory drugs (IMiDs) downregulate p21 and trigger apoptosis in wild-type-p53 MM. 1S cells, Importantly, we demonstrate by pull-down, nuclear magnetic resonance spectroscopy, differential scanning f luorimetry, and isothermal titration calorimetry that IMiDs bind and inhibit TP53RK, with biologic sequelae similar to TP53RK knockdown. Our studies therefore demonstrate that either genetic or pharmacological inhibition of TP53RK triggers MM cell apoptosis via both p53-Myc axis-dependent and axis-independent pathways, validating TP53RK as a novel therapeutic target in patients with poor-prognosis MM. [ABSTRACT FROM AUTHOR]

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]

Oncogene-induced DNA damage elicits genomic instability in epithelial cancer cells, but apoptosis is blocked through inactivation of the tumor suppressor p53. In hematological cancers, the relevance of ongoing DNA damage and the mechanisms by which apoptosis is suppressed are largely unknown. We found pervasive DNA damage in hematologic malignancies, including multiple myeloma, lymphoma and leukemia, which leads to activation of a p53-independent, proapoptotic network centered on nuclear relocalization of ABL1 kinase. Although nuclear ABL1 triggers cell death through its interaction with the Hippo pathway coactivator YAP1 in normal cells, we show that low YAP1 levels prevent nuclear ABL1-induced apoptosis in these hematologic malignancies. YAP1 is under the control of a serine-threonine kinase, STK4. Notably, genetic inactivation of STK4 restores YAP1 levels, triggering cell death in vitro and in vivo. Our data therefore identify a new synthetic-lethal strategy to selectively target cancer cells presenting with endogenous DNA damage and low YAP1 levels. [ABSTRACT FROM AUTHOR]

Histone deacetylase (HDAC) enzymatic activity has been linked to the transcription of DNA in cancers including multiple myeloma (MM). Therefore, HDAC inhibitors used alone and in combination are being actively studied as novel therapies in MM. In the present study, we investigated the preclinical activity of ACY-1215, an HDAC6-selective inhibitor, alone and in combination with bortezomib in MM. Low doses of ACY-1215 combined with bortezomib triggered synergistic anti-MM activity, resulting in protracted endoplasmic reticulum stress and apoptosis via activation of caspase-3, caspase-8, and caspase-9 and poly (ADP) ribosome polymerase. In vivo, the anti-MM activity of ACY-1215 in combination with bortezomib was confirmed using 2 different xenograft SCID mouse models: human MM injected subcutaneously (the plasmacytoma model) and luciferase-expressing human MM injected intravenously (the disseminated MM model). Tumor growth was significantly delayed and overall survival was significantly prolonged in animals treated with the combination therapy. Pharmacokinetic data showed peak plasma levels of ACY-1215 at 4 hours after treatment coincident with an increase in acetylated a-tubulin, a marker of HDAC6 inhibition, by immunohis-tochemistry and Western blot analysis. These studies provide preclinical rationale for acetylated a-tubulin use as a pharmacodynamic biomarker in future clinical trials. [ABSTRACT FROM AUTHOR]

The interaction between multiple myeloma (MM) cells and the bone marrow (BM) microenvironment induces proliferation and survival of MM cells, as well as osteoclastogenesis. This study investigated the therapeutic potential of novel p38 mitogen-activated protein kinase (p38MAPK) inhibitor LY2228820 (LY) in MM. Although cytotoxicity against MM cell lines was modest, LY significantly enhanced the toxicity of bortezomib by down-regulating bortezomib-induced heat shock protein 27 phosphorylation. LY inhibited interleukin-6 secretion from long term cultured-BM stromal cells and BM mononuclear cells (BMMNCs) derived from MM patients in remission. LY also inhibited macrophage inflammatory protein-1α secretion from patient MM cells and BMMNCs as well as normal CD14 positive osteoclast precursor cells. Moreover, LY significantly inhibited in vitro osteoclastogenesis from CD14 positive cells induced by macrophage-colony stimulating factor and soluble receptor activator of nuclear factor-κB ligand. Finally, LY also inhibited in vivo osteoclatogenesis in a severe combined immunodeficiency mouse model of human MM. These results suggest that LY represents a promising novel targeted approach to improve MM patient outcome both by enhancing the effect of bortezomib and by reducing osteoskeletal events. [ABSTRACT FROM AUTHOR]

This study investigated the biological significance of the inhibition of fatty acid synthase (FAS) in multiple myeloma (MM) using the small molecule inhibitor Cerulenin. Cerulenin triggered growth inhibition in both MM cell lines and MM patient cells, and overcame the survival and growth advantages conferred by interleukin-6, insulin-like growth factor-1, and bone marrow stromal cells. It induced apoptosis in MM cell lines with only modest activation of caspase -8, -9, -3 and PARP; moreover, the pan-caspase inhibitor Z-VAD-FMK did not inhibit Cerulenin-induced apoptosis and cell death. In addition, treatment of MM cells with Cerulenin primarily up-regulated apoptosis-inducing factor/endonuclease G, mediators of caspase-independent apoptosis. Importantly, Cerulenin induced endoplasmic reticulum stress response via up-regulation of the Grp78/IRE1α/JNK pathway. Although the C-Jun-NH2-terminal kinase (JNK) inhibitor SP600215 blocked Cerulenin-induced cytotoxicity, it did not inhibit apoptosis and caspase cleavage. Furthermore, Cerulenin showed synergistic cytotoxic effects with various agents including Bortezomib, Melphalan and Doxorubicin. Our results therefore indicate that inhibition of FAS by Cerulenin primarily triggered caspase-independent apoptosis and JNK-dependent cytotoxicity in MM cells. This report demonstrated that inhibition of FAS has anti-tumour activity against MM cells, suggesting that it represents a novel therapeutic target in MM. [ABSTRACT FROM AUTHOR]

Akt mediates growth and drug resistance in multiple myeloma (MM) cells in the bone marrow (BM) microenvironment. We have shown that a novel Akt inhibitor Perifosine induces significant cytotoxicity in MM cells in the BM milieu. This study further delineated molecular mechanisms whereby Perifosine triggered cytotoxicity in MM cells. Neither the intensity of Jun NH2-terminal kinase phosphorylation nor caspase/poly (ADP-ribose) polymerase cleavage correlated with Perifosine-induced cytotoxicity in MM.1S, INA6, OPM1 and OPM2 MM cells. However, survivin, which regulates caspase-3 activity, was markedly downregulated by Perifosine treatment, without changes in other anti-apoptotic proteins. Downregulation of survivin by siRNA significantly inhibited OPM1 MM cell growth, confirming that survivin mediates MM cell survival. Perifosine significantly downregulated both function and protein expression of β-catenin. Co-culture with BM stromal cells (BMSCs) upregulated both β-catenin and survivin expression in MM cells, which was blocked by Perifosine. Importantly, Perifosine treatment also downregulated survivin expression in human MM cells grown in vivo in a severe combined immunodeficient mouse xenograft model. Finally, Perifosine inhibited bortezomib-induced upregulation of survivin, associated with enhanced cytotoxicity of combined bortezomib and Perifosine treatment. These preclinical studies provide the framework for clinical trials of bortezomib with Perifosine to improve patient outcome in MM. [ABSTRACT FROM AUTHOR]

Multiple myeloma is a plasma cell malignancy characterized by complex heterogeneous cytogenetic abnormalities. The bone marrow microenvironment promotes multiple myeloma cell growth and resistance to conventional therapies. Although multiple myeloma remains incurable, novel targeted agents, used alone or in combination, have shown great promise to overcome conventional drug resistance and improve patient outcome. Recent oncogenomic studies have further advanced our understanding of the molecular pathogenesis of multiple myeloma, providing the framework for new prognostic classification and identifying new therapeutic targets. [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]

We have previously shown that heat shock protein (Hsp) 27 or its upstream activator p38 mitogen-activated protein kinase (MAPK) confers resistance to bortezomib and dexamethasone (Dex) in multiple myeloma (MM) cells. This study examined anti-MM activity of a novel p38 MAPK inhibitor, BIRB 796, alone and in combination with conventional and novel therapeutic agents. BIRB 796 blocked baseline and bortezomib-triggered upregulation of p38 MAPK and Hsp27 phosphorylation, thereby enhancing cytotoxicity and caspase activation. The Hsp90 inhibitor 17-allylamino-17-demethoxy-geldanamycin (17-AAG) upregulated protein expression and phosphorylation of Hsp27; conversely, BIRB 796 inhibited this phosphorylation and enhanced 17-AAG-induced cytotoxicity. Importantly, BIRB 796 inhibited Hsp27 phosphorylation induced by 17-AAG plus bortezomib, thereby enhancing cytotoxicity. In bone marrow stromal cells (BMSC), BIRB 796 inhibited phosphorylation of p38 MAPK and secretion of interleukin-6 (IL-6) and vascular endothelial growth factor triggered by either tumour necrosis factor- α or tumour growth factor- β1. BIRB 796 also inhibited IL-6 secretion induced in BMSCs by adherence to MM cells, thereby inhibiting tumour cell proliferation. These studies therefore suggest that BIRB 796 overcomes drug-resistance in the BM microenvironment, providing the framework for clinical trials of a p38 MAPK inhibitor, alone and in combination with bortezomib, Hsp90 inhibitor, or Dex, to improve patient outcome in MM. [ABSTRACT FROM AUTHOR]

Multiple myeloma (MM) is a malignancy of plasma cells within the bone marrow characterized by bone loss, renal disease, and immunodeficiency. Recent advances in the understanding of MM pathogenesis have improved established conventional cytotoxic therapy as well as transplantation regimens. Despite these advances, median overall survival is only 3–5 years. Therefore new therapies are urgently needed. Besides thalidomide, whose antimyeloma activity has only recently been defined, a plethora of novel agents, including the thalidomide-derived immunomodulatory drugs and bortezomib, have been identified to directly target the tumor cell or its microenvironment, and thereby inhibit MM cell growth and survival, and to overcome drug resistance. After validation of their preclinical anti-MM activity, several clinical trials are now ongoing to test the efficacy of these novel therapeutics, administered alone or in combination with conventional or other novel therapeutics and bone marrow transplantation. This article reviews the development of MM therapy, from its initial description approximately 150 years ago to the novel therapy regimens of recent years, highlighting that MM may soon become a chronic disease. [ABSTRACT FROM AUTHOR]

Multiple myeloma (MM) remains largely incurable despite conventional and high-dose therapies, and novel biologically based treatment approaches are urgently required. Recent studies demonstrate that various growth factors including interleukin (IL)-6, insulin-like growth factor (IGF)-1, vascular endothelial growth factor (VEGF), the tumour necrosis factor (TNF) family proteins, Wnt, and Notch family members play an important role in MM pathogenesis, and mediate tumour cell proliferation, drug resistance and migration in the bone marrow (BM) milieu. Targeting growth factors, therefore, represents a promising therapeutic strategy in MM. Novel agents inhibiting growth factor signalling cascades can target ligands, receptors, and/or downstream signalling cascade proteins in MM cells and the BM microenvironment. Combinations of these novel agents with conventional therapies may not only enhance cytotoxicity, but also avoid drug resistance and thereby improve patient outcome in MM. [ABSTRACT FROM AUTHOR]

Inosine monophosphate dehydrogenase (IMPDH) is a rate-limiting enzyme required for the de novo synthesis of guanine nucleotides from IMP. VX-944 (Vertex Pharmaceuticals, Cambridge, MA, USA) is a small-molecule, selective, noncompetitive inhibitor directed against human IMPDH. In this report, we show that VX-944 inhibits in vitro growth of human multiple myeloma (MM) cell lines via induction of apoptosis. Interleukin-6, insulin-like growth factor-1, or co-culture with bone marrow stromal cells (BMSCs) do not protect against VX-944-induced MM cell growth inhibition. VX-944 induced apoptosis in MM cell lines with only modest activation of caspases 3, 8, and 9. Furthermore, the pan-caspase inhibitor z-VAD-fmk did not inhibit VX-944-induced apoptosis and cell death. During VX-944-induced apoptosis, expressions of Bax and Bak were enhanced, and both apoptosis-inducing factor (AIF) and endonuclease G (Endo G) were released from the mitochondria to cytosol, suggesting that VX-944 triggers apoptosis in MM cells primarily via a caspase-independent, Bax/AIF/Endo G pathway. Importantly, VX-944 augments the cytotoxicity of doxorubicin and melphalan even in the presence of BMSCs. Taken together, our data demonstrate a primarily non-caspase-dependent apoptotic pathway triggered by VX-944, thereby providing a rationale to enhance MM cell cytotoxicity by combining this agent with conventional agents which trigger caspase activation.Oncogene (2005) 24, 5888–5896. doi:10.1038/sj.onc.1208739; published online 6 June 2005 [ABSTRACT FROM AUTHOR]

We have shown that the proteasome inhibitor bortezomib (formerly known as P5-341) triggers significant antitumor activity in multiple myeloma (MM) in both preclinical models and patients with relapsed refractory disease. Recent studies have shown that unfolded and misfolded ubiquitinated proteins are degraded not only by proteasomes, but also by aggresomes, dependent on histone deacetylase 6 (HDAC6) activity. We therefore hypothesized that inhibition of both mechanisms of protein catabolism could induce accumulation of ubiquitinated proteins followed by significant cell stress and cytotoxicity in MM cells. To prove this hypothesis, we used bortezomib and tubacin to inhibit the proteasome and HDAC6, respectively. Tubacin specifically triggers acetylation of u-tubulin as a result of HDAC6 inhibition in a dose- and time-dependent fashion. It induces cytotoxicity in MM cells at 72 h with an IC50 of 5-20 pM, which is mediated by caspase-dependent apoptosis; no toxicity is observed in normal peripheral blood mononuclear cells. Tubacin inhibits the interaction of HDAC6 with dynein and induces marked accumulation of ubiquitinated proteins. It synergistically augments bortezomib-induced cytotoxicity by c-Jun NH2-terminal kinase/caspase activation. Importantly, this combination also induces significant cytotoxicity in plasma cells isolated from MM patient bone marrow. Finally, adherence of MM cells to bone marrow stromal cells confers growth and resistance to conventional treatments; in contrast, the combination of tubacin and bortezomib triggers toxicity even in adherent MM cells. Our studies therefore demonstrate that tubacin combined with boil-ezomib mediates significant anti-MM activity, providing the frame- work for clinical evaluation of combined therapy to improve patient outcome in MM. [ABSTRACT FROM AUTHOR]

PS-341 (bortezomib, Velcade™) is a promising novel agent for treatment of advanced multiple myeloma (MM); however, 65%of patients with relapsed refractory disease in a phase II study do not respond to PS-341. We have previously shown that lysophosphatidic acid acyltransferase (LPAAT)-ßinhibitor CT-32615 triggers caspase-dependent apoptosis, and can overcome resistance to conventional therapeutics (i.e., dexamethasone, doxorubicin, melphalan) in MM cells. In this study, we therefore determined whether CT-32615 could also overcome resistance to PS-341. We first characterized molecular mechanisms of resistance to PS-341 in DHL-4 cells. DHL-4 cells express low levels of caspase-3 and caspase-8; furthermore, no cleavage in caspase-8, caspase-9, caspase-3, poly ADP-ribose polymerase (PARP), or DNA fragmentation factor 45 was triggered by PS-341 treatment. We have previously shown that PS-341 treatment triggers phosphorylation of c-Jun NH2-terminal kinase (JNK), which subsequently induces caspase-dependent apoptosis; conversely, JNK inhibition blocks PS-341-induced apoptosis. We here show that phosphorylation of SEK-1, JNK, and c-Jun are not induced by PS-341 treatment, suggesting that PS-341 does not trigger a stress response in DHL-4 cells. Importantly, CT-32615 inhibits growth of DHL-4 cells in a time- and dose-dependent fashion: a transient G2/M cell cycle arrest induced by CT-32615 is mediated via downregulation of cdc25c and cdc2. CT-32615 triggered swelling and lysis of DHL-4 cells, without caspase/PARP cleavage or TUNEL-positivity, suggesting a necrotic response. Our studies therefore demonstrate that LPAAT-ßinhibitor CT-32615 triggers necrosis, even in PS-341-resistant DHL-4 cells, providing the framework for its evaluation to overcome clinical PS-341 resistance and improve patient outcome.Oncogene (2005) 24, 3121-3129. doi:10.1038/sj.onc.1208522 Published online 21 February 2005 [ABSTRACT FROM AUTHOR]

Normal cellular functioning requires processing of proteins regulating cell cycle, growth, and apoptosis. The ubiquitin-proteasome pathway (UBP) modulates intracellular protein degradation. Specifically, the 26S proteasome is a multienzyme protease that degrades misfolded or redundant proteins; conversely, blockade of the proteasomal degradation pathways results in accumulation of unwanted proteins and cell death. Because cancer cells are more highly proliferative than normal cells, their rate of protein translation and degradation is also higher. This notion led to the development of proteasome inhibitors as therapeutics in cancer. The FDA recently approved the first proteasome inhibitor bortezomib (Velcade ™ ), formerly known as PS-341, for the treatment of newly diagnosed and relapsed/refractory multiple myeloma (MM). Ongoing studies are examining other novel proteasome inhibitors, in addition to bortezomib, for the treatment of MM and other cancers. [ABSTRACT FROM AUTHOR]

Thalidomide and immunomodulatory drugs (IMiDs), which target multiple myeloma (MM) cells and the bone marrow microenvironment, can overcome drug resistance. These agents also have immunomodulatory effects. Specifically, we have reported that thalidomide increased serum interleukin-2 (IL-2) levels and natural killer (NK) cell numbers in the peripheral blood of responding MM patients. In this study, we investigated the mechanisms whereby IMiDs augment NK cell cytotoxicity. NK cytotoxicity and antibody-dependent cell-mediated cytotoxicity (ADCC) of peripheral blood mononuclear cells cultured with IMiDs were examined in the presence or absence of anti-IL-2 antibody, ciclosporin A or depletion of CD56-positive cells. IMiDs-induced signalling pathways, triggering IL-2 transcription in T cells, were also delineated. IMiDs facilitated the nuclear translocation of nuclear factor of activated T cells-2 and activator protein-1 via activation of phosphoinositide-3 kinase signalling, with resultant IL-2 secretion. IMiDs enhanced both NK cell cytotoxicity and ADCC induced by triggering IL-2 production from T cells. These studies defined the mechanisms whereby IMiDs trigger NK cell-mediated tumour-cell lysis, further supporting their therapeutic use in MM. [ABSTRACT FROM AUTHOR]

Although PS-341 (bortezomib) is a promising agent to improve multiple myeloma (MM) patient outcome, 65%of patients with relapsed and refractory disease do not respond. We have previously shown that heat shock protein (Hsp)27 is upregulated after PS-341 treatment, that overexpression of Hsp27 confers PS-341 resistance, and that inhibition of Hsp27 overcomes PS-341 resistance. Since Hsp27 is a downstream target of p38 mitogen-activated protein kinase (MAPK)/MAPK-mitogen-activated protein kinase-2 (MAPKAPK2), we hypothesized that inhibition of p38 MAPK activity could augment PS-341 cytotoxicity by downregulating Hsp27. Although p38 MAPK inhibitor SCIO-469 (Scios Inc, CA, USA) alone did not induce significant growth inhibition, it blocked baseline and PS-341-triggered phosphorylation of p38 MAPK as well as upregulation of Hsp27, associated with enhanced cytotoxicity in MM.1S cells. Importantly, SCIO-469 enhanced phosphorylation of c-Jun NH2-terminal kinase (JNK) and augmented cleavage of caspase-8 and poly(ADP)-ribose polymerase. Moreover, SCIO-469 downregulated PS-341-induced increases in G2/M-phase cells, associated with downregulation of p21Cip1 expression. Importantly, SCIO-469 treatment augmented cytotoxicity of PS-341 even against PS-341-resistant cell lines and patient MM cells. These studies therefore provide the framework for clinical trials of SCIO-469 to enhance sensitivity and overcome resistance to PS-341, thereby improving patient outcome in MM.Oncogene (2004) 23, 8766-8776. doi:10.1038/sj.onc.1208118 Published online 11 October 2004 [ABSTRACT FROM AUTHOR]

Proteasome inhibition is a new approach under investigation for cancer therapy. Protein degradation by the proteasome is a fundamental metabolic process. Inhibition of the proteasome has been shown to result in cell-cycle arrest and programmed cell death. Bortezomib (Velcade®; formerly PS-341, Millennium Pharmaceuticals, Inc, Cambridge, Massachusetts) is the first proteasome inhibitor to enter clinical trials and is approved for the treatment of multiple myeloma in patients who have received at least two prior therapies and progressed on their last therapy. It is also being investigated for the treatment of a range of other cancers, both solid and hematologic. In preclinical studies, bortezomib causes apoptosis in cancer cells and seems to enhance the cytotoxicity of other conventional tumoricidal agents in human tumor cell lines, murine tumor models, and human xenograft models. In addition to targeting cancer cells directly, there is growing evidence that proteasome inhibition interferes with protective interactions between cancer cells and the bone marrow and may also act to prevent tumor-associated angiogenesis. Preliminary data suggest that bortezomib inhibits proteasome activity in a dose-dependent and reversible manner, and has manageable toxicities. A phase II trial in relapsed and refractory multiple myeloma patients indicated that patients experienced substantial anticancer activity when treated with bortezomib monotherapy. [ABSTRACT FROM AUTHOR]

Multiple myeloma (MM) cells express certain tumour-associated antigens (TAAs) that could serve as targets for active-specific immunotherapy. The aim of the present study was to test the MM/dendritic cell (DC) fusion as a vaccination strategy. We fused MM cells with DC to generate fusion cells (FCs) and tested their antigen presenting cell (APC) function in mixed lymphocyte reactions and cytotoxicity assays. First, the HS Sultan and SK0-007 HAT sensitive human MM cell lines and DCs generated from peripheral blood of normal donors were fused in the presence of 50% polyethylene glycol to form FCs. Next, tumour cells freshly isolated from patients were similarly fused with autologous DCs to generate FCs. The FCs demonstrated a biphenotypic profile, confirmed both by flow-cytometry and dual immunofluorescence microscopy. These FCs induced MM-specific cytotoxicity. FCs, but not MM cells or DCs alone, were potent stimulators of autologous patient T cells. More importantly, FC-primed autologous peripheral blood mononuclear cells demonstrated major histocompatibility complex-restricted MM-specific cytolysis. These studies therefore demonstrated that MM/DC FC can trigger an autologous immune response to MM cells and formed the framework for a clinical trial currently underway. [ABSTRACT FROM AUTHOR]

Although c-Jun NH2-terminal kinase (JNK) is activated by treatment with therapeutic agents, the biologic sequelae of inhibiting constitutive activation of JNK has not yet been clarified. In this study, we examine the biologic effect of JNK inhibition in multiple myeloma (MM) cell lines. JNK-specific inhibitor SP600125 induces growth inhibition via induction of G1 or G2/M arrest in U266 and MM.1S multiple myeloma cell lines, respectively. Neither exogenous IL-6 nor insulin-like growth factor-1 (IGF-1) overcome SP600125-induced growth inhibition, and IL-6 enhances SP600125-induced G2/M phase in MM.1S cells. Induction of growth arrest is mediated by upregulation of p27Kip1, without alteration of p53 and JNK protein expression. Importantly, SP600125 inhibits growth of MM cells adherent to bone marrow stromal cells (BMSCs). SP600125 induces NF-?B activation in a dose-dependent fashion, associated with phosphorylation of I?B kinase a (IKKa) and degradation of I?Ba. In contrast, SP600125 does not affect phosphorylation of STAT3, Akt, and/or ERK. IKK-specific inhibitor PS-1145 inhibits SP600125-induced NF-?B activation and blocks the protective effect of SP600125 against apoptosis. Our data therefore demonstrate for the first time that inhibiting JNK activity induces growth arrest and activates NF-?B in MM cells.Oncogene (2003) 22, 8797-8801. doi:10.1038/sj.onc.1206919 [ABSTRACT FROM AUTHOR]

Proteasome inhibitor PS-341 is one of the most promising novel agents against multiple myeloma (MM). We have previously shown that PS-341 inhibits IL-6 triggered phosphorylation of extracellular signal-regulated kinases (ERK) 1/2 (also known as p42/44 mitogen-activated protein kinases) in MM cells. In this study, we further examined whether clinically achievable concentrations of PS-341 could inhibit IL-6 triggered signaling cascades in MM. We found that PS-341 inhibited not only ERK, but also signal transducers and activators of transcription (STAT) 3 as well as Akt phosphorylation. Since gp130 (CD130) dimerizes and is phosphorylated after IL-6 binding to gp80 (IL-6 receptor), we hypothesized that gp130 could be involved in PS-341-induced blockade of signaling cascades mediating MM cell growth, survival, and drug resistance in the bone marrow (BM) microenvironment. In this study, we first demonstrate that PS-341 induces downregulation of gp130 in a time- and dose-dependent manner in vitro, prior to MM cell death. Conversely, downregulation of gp130 is completely abrogated by the pan-caspase inhibitor Z-VAD-FMK, suggesting that downregulation of gp130 is mediated via caspase activation. Z-VAD-FMK also abrogates the inhibitory effect of PS-341 on IL-6-triggered signaling cascades. Importantly, we demonstrate that phosphorylation of ERK, STAT3, and Akt in MM.1S cells induced by either exogenous IL-6 or by binding of MM cells to BM stromal cells is abrogated by PS-341. These studies, therefore, define another novel mechanism whereby PS-341 can overcome the growth and survival advantage in MM cells conferred by the BM milieu. Importantly, this effect on cytokine-induced gp130 signaling cascades may account, at least in part, for the remarkable preclinical sensitivity and clinical responses achieved in MM with PS-341 treatment.Oncogene (2003) 22, 8386-8393. doi:10.1038/sj.onc.1207170 [ABSTRACT FROM AUTHOR]

Summary: Multiple myeloma (MM) affects 15 000 new patients annually in the US, with 50 000 total patients, and remains incurable. Our preliminary in vitro and animal studies suggest a role for MM–host interactions in regulating MM cell growth, drug resistance, and migration in the bone marrow. Importantly, treatment strategies which target mechanisms whereby MM cells grow and survive in the bone marrow, including thalidomide and its potent immunomodulatory derivatives and proteasome inhibitor PS-341, can overcome classical drug resistance in preclinical and early clinical studies. [ABSTRACT FROM AUTHOR]

Proteasome inhibitors represent potential novel anti-cancer therapy. These agents inhibit the degradation of multi-ubiquitinated target proteins mediating cell cycle progression, apoptosis, NF-κB activation, inflammation, cell cycle regulatory proteins such as cyclins and cyclin dependent kinase inhibitors, as well as immune surveillance; and regulate anti-apoptosis and cell cycle progression. Proteasome inhibitors also directly induce caspase-dependent apoptosis of tumor cells, despite the accumulation of p21 and p27 and irrespective of the p53 wild type or mutant status. Recent studies demonstrate that PS-341, peptide boronate, has remarkable anti-tumor activity in preclinical and clinical studies, not only in multiple myeloma but also in other malignancies. [ABSTRACT FROM AUTHOR]

Investigates novel therapies for multiple myeloma (MM). Role of the bone marrow microenvironment in the pathogenesis of MM; Thalidomide and its immunomodulatory derivatives; Proteasome inhibitors; NF-kappabetta inhibitors; Arsenic trioxide; 2-methyloxyestradiol; PTK787 tyrosine kinase inhibitor.

Multiple myeloma remains largely incurable despite conventional and high-dose therapies, and so novel biologically based treatment approaches are urgently required. Recent studies have characterized the molecular mechanisms by which multiple myeloma cell-host bonemarrow interactions regulate tumour cell growth, survival and migration in the bone-marrow microenvironment. These studies have not only enhanced our understanding of disease pathogenesis, but have also provided the framework for a new treatment model that targets the multiple myeloma cell in its bone-marrow microenvironment to overcome drug resistance and improve patient outcome. [ABSTRACT FROM AUTHOR]

Multiple myeloma remains incurable despite advances in conventional chemotherapy and wider applicability of high dose chemotherapy with single and/or tandem autologous peripheral blood stem cell transplantation. Although a complete remission rate of 41% and an event-free survival of 43 months have been reported after tandem transplantation, it is highly unlikely that further improvements in the outcome of multiple myeloma will be achieved by escalating cytotoxic chemotherapy alone. Novel biologically based therapies are therefore urgently required. Targeted therapeutic approaches based on: identification of genetic abnormalities in malignant plasma cells; interrupting growth of myeloma cells; triggering apoptotic signaling cascades in tumor cells; modulating growth and survival of multiple myeloma cells in the bone marrow microenvironment, i.e. angiogenesis and cytokine networks; enhancing allogeneic and autologous antimyeloma immunity; and characterizing newer myeloma antigens for serotherapy are under development. These therapies offer great promise, used alone/or in combination with conventional treatment approaches, to improve the outcome in this disease in newly diagnosed/refractory or relapsed patients with multiple myeloma. [ABSTRACT FROM AUTHOR]

Offers information on the drug thalidomide. History; Pharmacology; Details on its preclinical and clinical studies for the treatment of cancer.

Previous studies demonstrate that interleukin-6 (IL-6) mediates growth and survival in human multiple myeloma (MM) cells via the MEK/MAPK and JAK/STAT signaling pathways, respectively. IL-6 also confers protection against Dexamethasone (Dex)-induced apoptosis via activation of protein tyrosine phosphatase (SHP2). In the current study, we characterized IL-6 triggered phophatidylinositol-3 kinase/Akt kinase (PI3-K/Akt) signaling in MM cells. IL-6 induces Akt/PKB phosphorylation in a time and dose dependent manner in MM.1S MM cells. IL-6 also induced phosphorylation of downstream targets of Akt, including Bad, GSK-3β, and FKHR, confirming Akt activation. Inhibition of Akt activation by the PI3-K inhibitor LY294002 partially blocked IL-6 triggered MEK/MAPK activation and proliferation in MM.1S cells, suggesting cross-talk between PI3-K and MEK signaling. We demonstrate that Dex-induced apoptosis in MM.1S cells is mediated by downstream activation of caspase-9, with resultant caspase-3 cleavage; and conversely, that IL-6 triggers activation of PI3-K and its association with SHP2, inactivates caspase-9, and protects against Dex-induced apoptosis. LY294002 completely abrogates this signaling cascade, further confirming the importance of PI3-K/Akt signaling in conferring the protective effect of IL-6 against Dex-induced apoptosis. Finally, we show that IL-6 triggered PI3-K/Akt signaling in MM.1S cells inactivates forkhead transcriptional factor (FKHR), with related G1/S phase transition, whereas LY294002 blocks this signaling, resulting in upregulation of p27KIP1 and G1 growth arrest. Our data therefore suggest that PI3-K/Akt signaling mediates growth, survival, and cell cycle regulatory effects of IL-6 in MM. Oncogene (2001) 20, 5991–6000. [ABSTRACT FROM AUTHOR]

In this study we demonstrate that tumor necrosis factor α (TNFα) triggers only modest proliferation, as well as p44/p42 mitogen-activated protein kinase (MAPK) and NF-κB activation, in MM.1S multiple myeloma (MM) cells. TNFα also activates NF-κB and markedly upregulates (fivefold) secretion of interleukin-6 (IL-6), a myeloma growth and survival factor, in bone marrow stromal cells (BMSCs). TNFα in both a dose and time dependent fashion induced expression of CD11a (LFA-1), CD54 (intercellular adhesion molecule-1, ICAM-1), CD106 (vascular cell adhesion molecule-1, VCAM-1), CD49d (very late activating antigen-4, VLA-4), and/or MUC-1 on MM cell lines; as well as CD106 (VCAM-1) and CD54 (ICAM-1) expression on BMSCs. This resulted in increased (2–4-fold) per cent specific binding of MM cells to BMSCs, with related IL-6 secretion. Importantly, the proteasome inhibitor PS-341 abrogated TNFα-induced NF-κB activation, induction of ICAM-1 or VCAM-1, and increased adhesion of MM cells to BMSCs. Agents which act to inhibit TNFα may therefore abrogate the paracrine growth and survival advantage conferred by MM cell adhesion in the BM microenvironment. Oncogene (2001) 20, 4519–4527. [ABSTRACT FROM AUTHOR]

Simple Summary: The bone marrow (BM) microenvironment plays a crucial role in pathogenesis of multiple myeloma (MM), and delineation of the intracellular signaling pathways activated in the BM microenvironment in MM cells is essential to develop novel therapeutic strategies to improve patient outcome. The multiple myeloma (MM) bone marrow (BM) microenvironment consists of different types of accessory cells. Both soluble factors (i.e., cytokines) secreted from these cells and adhesion of MM cells to these cells play crucial roles in activation of intracellular signaling pathways mediating MM cell growth, survival, migration, and drug resistance. Importantly, there is crosstalk between the signaling pathways, increasing the complexity of signal transduction networks in MM cells in the BM microenvironment, highlighting the requirement for combination treatment strategies to blocking multiple signaling pathways. [ABSTRACT FROM AUTHOR]

Related Adhesion Focal Tyrosine Kinase (RAFTK; also known as Pyk2), is a member of the Focal Adhesion Kinase (FAK) subfamily and is activated by TNFα, UV light and increases in intracellular calcium levels. However, the function of RAFTK remains largely unknown. Our previous studies demonstrated that treatment with dexamethasone (Dex), ionizing radiation (IR), and anti-Fas mAb induces apoptosis in multiple myeloma (MM) cells. In the present study, we examined the potential role of RAFTK during induction of apoptosis in human MM cells triggered by these three stimuli. Dex-induced apoptosis, in contrast to apoptosis triggered by anti-Fas mAb or IR, is associated with activation of RAFTK. Transient overexpression of RAFTK wild type (RAFTK WT) induces apoptosis, whereas transient overexpression of Kinase inactive RAFTK (RAFTK K-M) blocks Dex-induced apoptosis. In contrast, transient overexpression of RAFTK K-M has no effect on apoptosis triggered by IR or Fas. In Dex-resistant cells, Dex does not trigger either RAFTK activation or apoptosis. Finally, interleukin-6 (IL-6), a known survival factor for MM cells, inhibits both activation of RAFTK and apoptosis of MM.1S cells triggered by Dex. Our studies therefore demonstrate Dex-induced RAFTK-dependent, and IR or Fas induced RAFTK-independent apoptotic signaling cascades in MM cells. [ABSTRACT FROM AUTHOR]

Glucocorticoids have been widely used in the treatment of multiple myeloma (MM) both as single agents and in combination with other drugs. However, primary or acquired glucocorticoid resistance occurs in most cases. It was recently reported that R-etodolac induced in vitro cytotoxicity in MM cell lines and in primary MM cells, as well as synergistically enhanced dexamethasone (Dex)-induced apoptosis in Dex-sensitive MM.1S cells. This study examined the in vitro and in vivo effects of combination treatment with R-etodolac and Dex on Dex-resistant OPM1 cells. Treatment with R-etodolac and Dex was found to enhance cytotoxicity, inhibit nuclear factor κB activity via upregulation of I κB α, as well as enhance Dex-induced caspase activation and poly (ADP)-ribose polymerase cleavage in OPM1 cells. R-etodolac also enhanced Dex cytotoxicity in patient MM cells that were resistant to glucocorticoids. The in vivo anti-tumour effect of this combination on MM cells was evaluated by using severe combined immunodeficient mice engrafted with OPM1. Treatment with R-etodolac or Dex alone did not induce a significant reduction of tumour volume; in contrast, combination treatment with R-etodolac and Dex induced significant synergistic inhibition of tumour growth. These data indicate that R-etodolac overcomes resistance to Dex in glucocorticoid-resistant MM cells, providing the framework for clinical trials of R-etodolac combined with Dex, to improve patient outcome in MM. [ABSTRACT FROM AUTHOR]

Multiple myeloma (MM) is a plasma cell malignancy that claims thousands of lives each year and has considerable morbidity. The disease remains incurable despite recent advances in the understanding of the disease biology and the introduction of more effective drugs is needed. This study evaluated the anti-MM activity of 3-(7-fluoro-4H-quinazolin-3-yl)-piperidine-2,6-dione, hydrochloride (FQPD), a novel immunomodulatory drug. FQPD inhibited the proliferation of multiple MM cell lines, including those resistant to conventional treatments, such as dexamethasone. It induced apoptosis in MM cell lines, as well as freshly isolated patient MM cells, without cytotoxicity on normal human lymphocytes. Moreover, it induced apoptosis in MM cells adherent to bone marrow (BM) stromal cells or in the presence of cytokines, such as interleukin-6 and vascular endothelial growth factor, confirming its ability to overcome the protective effects of the BM milieu. Apoptosis in the MM cells was mediated via poly-ADP ribose polymerase cleavage as well as cleavage of caspase 8 and caspase 9. Our studies therefore demonstrated in vitro anti-MM activity of FQPD and provide the rationale for its in vivo evaluation in animal models and derived clinical trials. [ABSTRACT FROM AUTHOR]

VELCADE® (bortezomib, Millennium Pharmaceuticals, Inc., Cambridge, MA, and Johnson&Johnson Pharmaceutical Research&Development, L.L.C., Raritan, NJ) is a first-in-class proteasome inhibitor developed specifically for use as an antineoplastic agent. Inhibition of the proteasome results in disruption of homeostatic mechanisms within the cell that can lead to cell death. Bortezomib's first indication, for the treatment of relapsed myeloma in patients who have received at least two prior treatments and progressed on their previous treatment, was based in part on the magnitude of activity demonstrated in phase II trials. Bortezomib is currently indicated for patients who have received at least one prior therapy in the United States and European Union, although patients in the European Union must have already undergone bone marrow transplantation or be unsuitable for the procedure. A phase III trial demonstrated the superiority of bortezomib over high-dose dexamethasone in response rate, time to progression, and survival in patients with myeloma who had relapsed after 1–3 prior therapies. Clinical development is ongoing to investigate its activity as monotherapy and in combination regimens for the treatment of non-Hodgkin's lymphoma, solid tumors, and earlier presentations of myeloma. [ABSTRACT FROM AUTHOR]

The ubiquitin-conjugating enzyme CDC34 (UBC3) is linked to cell cycle progression in diverse cell types; however, its role in multiple myeloma (MM) pathogenesis is unclear. Here, we show that CDC34 is highly expressed in patient MM cells and MM cell lines versus normal cells. Blocking CDC34 using a dominant-negative strategy enhances the anti-MM activity of Bortezomib/ Proteasome inhibitor PS-341, dexamethasone (Dex) and 2-Methoxyestradiol (2ME2). The expression of wild-type CDC34 reduces Dex-induced cytotoxicity in MM cells. Moreover, inhibition of CDC34 enzymatic activity abrogates interleukin-6-induced protection against Dex- induced apoptosis. Together, these findings provide evidence that (1) CDC34 expression is associated with growth and survival of MM cells and (2) blocking CDC34 activity not only enhances anti-MM activity of Bortezomib and 2ME2 but also overcomes IL-6-triggered Dex- resistance. [ABSTRACT FROM AUTHOR]

Maintenance of telomeres regulates chromosomal stability and cellular mitosis through a checkpoint mechanism. Continuous cell proliferation requires telomerase to maintain chromosomal stability and to counteract the cellular mitotic clock. Importantly, nuclear expression of telomerase activity is required for elongation of telomere sequences. In this study, we show that tumor necrosis factor α (TNFα) induces telomerase activity in the cytoplasm of peripheral blood lymphocytes (PBL) at 60 min, followed by translocation of activated telomerase to the nucleus at 120 min. Conversely, the phosphoinositol 3-kinase (PI3K) inhibitor wortmannin blocks TNFα-induced activation of telomerase, whereas the specific NF-κB translocation inhibitor SN-50 blocks TNFα-induced nuclear translocation of activated telomerase. These studies suggest that activation and nuclear translocation of telomerase are regulated by PI3K/Akt/NF-κB signaling pathways in PBL. [Copyright &y& Elsevier]

Summary. Multiple myeloma (MM) is currently incurable, and novel therapies are needed. In this study, we examined a novel recombinant humanized monoclonal antibody against CD40 (rhuCD40 mAb) and demonstrate for the first time that rhuCD40 mAb induces antibody-dependent cell-mediated cytotoxicity (ADCC) against CD40-positive MM cells. Importantly, we show that rhuCD40 mAb induces autologous ADCC against primary patient MM cells, without triggering ADCC against normal B cells. This study, therefore, both demonstrates that rhuCD40 mAb triggers autologous ADCC against patient MM cells and provides the framework for the clinical evaluation of rhuCD40 mAb immunotherapy to improve patient outcome in MM. [ABSTRACT FROM AUTHOR]

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.

Condensation of Igs has been observed in pharmaceutical formulations and in vivo in cases of cryoglobulinemia. We report a study of monoclonal IgG cryoglobulins overexpressed by two patients with multiple myeloma. These cryoglobulins form crystals, and we measured their solubility lines. Depending on the supersaturation, we observed a variety of condensate morphologies consistent with those reported in clinical investigations. Remarkably, the crystallization can occur at quite low concentrations. This suggests that, even within the regular immune response to infections, cryoprecipitation of Ig can be possible. [ABSTRACT FROM AUTHOR]

Multiple myeloma (MM), a B cell malignancy characterized by clonal proliferation of plasma cells in the bone marrow, remains incurable despite the use of novel and conventional therapies. In this study, we demonstrated MM cell cytotoxicity triggered by realgar (REA; As4S4) nanoparticles (NREA) versus Arsenic trioxide (ATO) against MM cell lines and patient cells. Both NREA and ATO showed in vivo anti-MM activity, resulting in significantly decreased tumour burden. The anti-MM activity of NREA and ATO is associated with apoptosis, evidenced by DNA fragmentation, depletion of mitochondrial membrane potential, cleavage of caspases and antiapoptotic proteins. NREA induced 2G/M cell cycle arrest and modulation of cyclin B1, p53 (TP53), p21 (CDKN1A), Puma (BBC3) and Wee-1 (WEE1). Moreover, NREA induced modulation of key regulatory molecules in MM pathogenesis including JNK activation, c-Myc (MYC), BRD4, and histones. Importantly, NREA, but not ATO, significantly depleted the proportion and clonogenicity of the MM stem-like side population, even in the context of the bone marrow stromal cells. Finally, our study showed that both NREA and ATO triggered synergistic anti-MM activity when combined with lenalidomide or melphalan. Taken together, the anti-MM activity of NREA was more potent compared to ATO, providing the preclinical framework for clinical trials to improve patient outcome in MM. [ABSTRACT FROM AUTHOR]

Lenalidomide ( LEN) acts directly on multiple myeloma ( MM) cells by inducing cereblon-mediated degradation of interferon regulatory factor 4, Ikaros ( IKZF)1 and IKZF3, transcription factors that are essential for MM cell survival. The mucin 1 ( MUC1) C-terminal transmembrane subunit ( MUC1-C) oncoprotein is aberrantly expressed by MM cells and protects against reactive oxygen species ( ROS)-mediated MM cell death. The present studies demonstrate that targeting MUC1-C with GO-203, a cell-penetrating peptide inhibitor of MUC1-C homodimerization, is more than additive with LEN in downregulating the WNT/β-catenin pathway, suppressing MYC, and inducing late apoptosis/necrosis. We show that the GO-203/ LEN combination acts by synergistically increasing ROS and, in turn, suppressing β-catenin. LEN resistance has been linked to activation of the WNT/β-catenin→ CD44 pathway. In this regard, our results further demonstrate that targeting MUC1-C is effective against LEN-resistant MM cells. Moreover, GO-203 resensitized LEN-resistant MM cells to LEN treatment in association with suppression of β-catenin and CD44. Targeting MUC1-C also resulted in downregulation of CD44 on the surface of primary MM cells. These findings, and the demonstration that expression of MUC1 and CD44 significantly correlate in microarrays from primary MM cells, provide support for combining GO-203 with LEN in the treatment of MM and in LEN-resistance. [ABSTRACT FROM AUTHOR]

Multiple myeloma (MM) is characterized by a highly unstable genome, with aneuploidy observed in nearly all patients. The mechanism causing this karyotypic instability is largely unknown, but recent observations have correlated these abnormalities with dysfunctional DNA damage response. Here, we show that the NAD+-dependent deacetylase SIRT6 is highly expressed in MM cells, as an adaptive response to genomic stability, and that high SIRT6 levels are associated with adverse prognosis. Mechanistically, SIRT6 interacts with the transcription factor ELK1 and with the ERK signaling-related gene. By binding to their promoters and deacetylating H3K9 at these sites, SIRT6 downregulates the expression of mitogen-activated protein kinase (MAPK) pathway genes, MAPK signaling, and proliferation. In addition, inactivation of ERK2/p90RSK signaling triggered by high SIRT6 levels increases DNA repair via Chk1 and confers resistance to DNA damage. Using genetic and biochemical studies in vitro and in human MM xenograft models, we show that SIRT6 depletion both enhances proliferation and confers sensitization to DNA-damaging agents. Our findings therefore provide insights into the functional interplay between SIRT6 and DNA repair mechanisms, with implications for both tumorigenesis and the treatment of MM. [ABSTRACT FROM AUTHOR]

Heat shock protein (HSP)90 inhibitors have shown significant anti-tumor activities in preclinical settings in both solid and hematological tumors. We previously reported that the novel, orally available HSP90α/β inhibitor TAS-116 shows significant anti-MM activities. In this study, we further examined the combination effect of TAS-116 with a RAS-RAF-MEK-ERK signaling pathway inhibitor in RAS- or BRAF-mutated MM cell lines. TAS-116 monotherapy significantly inhibited growth of RAS-mutated MM cell lines and was associated with decreased expression of downstream target proteins of the RAS-RAF-MEK-ERK signaling pathway. Moreover, TAS-116 showed synergistic growth inhibitory effects with the farnesyltransferase inhibitor tipifarnib, the BRAF inhibitor dabrafenib, and the MEK inhibitor selumetinib. Importantly, treatment with these inhibitors paradoxically enhanced p-C-Raf, p-MEK, and p-ERK activity, which was abrogated by TAS-116. TAS-116 also enhanced dabrafenib-induced MM cytotoxicity associated with mitochondrial damage-induced apoptosis, even in the BRAF-mutated U266 MM cell line. This enhanced apoptosis in RAS-mutated MM triggered by combination treatment was observed even in the presence of bone marrow stromal cells. Taken together, our results provide the rationale for novel combination treatment with HSP90α/β inhibitor and RAS-RAF-MEK-ERK signaling pathway inhibitors to improve outcomes in patients with in RAS- or BRAF-mutated MM. [ABSTRACT FROM AUTHOR]

B cell malignancies frequently colonize the bone marrow. The mechanisms responsible for this preferential homing are incompletely understood. Here we studied multiple myeloma (MM) as a model of a terminally differentiated B cell malignancy that selectively colonizes the bone marrow. We found that extracellular CyPA (eCyPA), secreted by bone marrow endothelial cells (BMECs), promoted the colonization and proliferation of MM cells in an in vivo scaffold system via binding to its receptor, CD147, on MM cells. The expression and secretion of eCyPA by BMECs was enhanced by BCL9, a Wnt-β-catenin transcriptional coactivator that is selectively expressed by these cells. eCyPA levels were higher in bone marrow serum than in peripheral blood in individuals with MM, and eCyPA-CD147 blockade suppressed MM colonization and tumor growth in the in vivo scaffold system. eCyPA also promoted the migration of chronic lymphocytic leukemia and lymphoplasmacytic lymphoma cells, two other B cell malignancies that colonize the bone marrow and express CD147. These findings suggest that eCyPA-CD147 signaling promotes the bone marrow homing of B cell malignancies and offer a compelling rationale for exploring this axis as a therapeutic target for these malignancies. [ABSTRACT FROM AUTHOR]

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]