SDX-308, a nonsteroidal anti-inflammatory agent, inhibits NF-kappaB activity, resulting in strong inhibition of osteoclast formation/activity and multiple myeloma cell growth

Targeting cancer-related inflammation with non-steroidal anti-inflammatory drugs: Perspectives in pharmacogenomics

Inflammatory processes are essential for innate immunity and contribute to carcinogenesis in various malignancies, such as colorectal cancer, esophageal cancer and lung cancer. Pharmacotherapies targeting inflammation have the potential to reduce the risk of carcinogenesis and improve therapeutic efficacy of existing anti-cancer treatment. Non-steroidal anti-inflammatory drugs (NSAIDs), comprising a variety of structurally different chemicals that can inhibit cyclooxygenase (COX) enzymes and other COX-independent pathways, are originally used to treat inflammatory diseases, but their preventive and therapeutic potential for cancers have also attracted researchers' attention. Pharmacogenomic variability, including distinct genetic characteristics among different patients, can significantly affect pharmacokinetics and effectiveness of NSAIDs, which might determine the preventive or therapeutic success for cancer patients. Hence, a more comprehensive understanding in pharmacogenomic characteristics of NSAIDs and cancer-related inflammation would provide new insights into this appealing strategy. In this review, the up-to-date advances in clinical and experimental researches targeting cancer-related inflammation with NSAIDs are presented, and the potential of pharmacogenomics are discussed as well.

HOTAIRM1 promotes osteogenic differentiation and alleviates osteoclast differentiation by inactivating the NF-κB pathway

Osteoporosis (OP), one of the most prevalent chronic progressive bone diseases, is caused by deficiency in bone formation by osteoblasts or excessive bone resorption by osteoclasts and subsequently increases the risk of bone fractures. Emerging evidence has indicated that long noncoding RNAs (lncRNAs) play key roles in many biological processes and various disorders. However, the role and mechanism of HOX antisense intergenic RNA myeloid 1 (HOTAIRM1), a myeloid-specific lncRNA, in osteoclast differentiation, osteogenic differentiation, and OP remain unclear. In this study, we found that HOTAIRM1 was upregulated during ossification of ligamentum flavum and osteogenic differentiation, while it was downregulated in osteoclast differentiation and in the bone and serum of human and mouse with OP. Further investigation revealed that silencing Hotairm1 decreased the expression of the osteogenic markers and attenuated osteogenesis. Moreover, forced Hotairm1 expression inhibited the expressions of the osteoclastogenesis markers and alleviated receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL)-induced osteoclast differentiation. Mechanically, Hotairm1 repressed the phosphorylation of p65 and inhibitor of κBα (IκBα) and attenuated RANKL-mediated enhancement of phos-p65 and IκBα, suggesting that Hotairm1 inhibits RANKL-induced osteoclastogenesis through the NF-κB pathway. In conclusion, our data identified a crucial role of HOTAIRM1 in OP, providing a proof of this molecule as a potential diagnostic marker and a possible therapeutic target against OP.

Inhibitory-κB Kinase (IKK) α and Nuclear Factor-κB (NFκB)-Inducing Kinase (NIK) as Anti-Cancer Drug Targets

The cellular kinases inhibitory-κB kinase (IKK) α and Nuclear Factor-κB (NF-κB)-inducing kinase (NIK) are well recognised as key central regulators and drivers of the non-canonical NF-κB cascade and as such dictate the initiation and development of defined transcriptional responses associated with the liberation of p52-RelB and p52-p52 NF-κB dimer complexes. Whilst these kinases and downstream NF-κB complexes transduce pro-inflammatory and growth stimulating signals that contribute to major cellular processes, they also play a key role in the pathogenesis of a number of inflammatory-based conditions and diverse cancer types, which for the latter may be a result of background mutational status. IKKα and NIK, therefore, represent attractive targets for pharmacological intervention. Here, specifically in the cancer setting, we reflect on the potential pathophysiological role(s) of each of these kinases, their associated downstream signalling outcomes and the stimulatory and mutational mechanisms leading to their increased activation. We also consider the downstream coordination of transcriptional events and phenotypic outcomes illustrative of key cancer 'Hallmarks' that are now increasingly perceived to be due to the coordinated recruitment of both NF-κB-dependent as well as NF-κB⁻independent signalling. Furthermore, as these kinases regulate the transition from hormone-dependent to hormone-independent growth in defined tumour subsets, potential tumour reactivation and major cytokine and chemokine species that may have significant bearing upon tumour-stromal communication and tumour microenvironment it reiterates their potential to be drug targets. Therefore, with the emergence of small molecule kinase inhibitors targeting each of these kinases, we consider medicinal chemistry efforts to date and those evolving that may contribute to the development of viable pharmacological intervention strategies to target a variety of tumour types.

Mesenchymal stem cells in multiple myeloma: a therapeutical tool or target?

Multiple myeloma (MM) is a malignant plasma cell (PC) disorder, characterized by a complex interactive network of tumour cells and the bone marrow (BM) stromal microenvironment, contributing to MM cell survival, proliferation and chemoresistance. Mesenchymal stem cells (MSCs) represent the predominant stem cell population of the bone marrow stroma, capable of differentiating into multiple cell lineages, including fibroblasts, adipocytes, chondrocytes and osteoblasts. MSCs can migrate towards primary tumours and metastatic sites, implying that these cells might modulate tumour growth and metastasis. However, this issue remains controversial and is not well understood. Interestingly, several recent studies have shown functional abnormalities of MM patient-derived MSCs indicating that MSCs are not just by-standers in the BM microenvironment but rather active players in the pathophysiology of this disease. It appears that the complex interaction of MSCs and MM cells is critical for MM development and disease outcome. This review will focus on the current understanding of the biological role of MSCs in MM as well as the potential utility of MSC-based therapies in this malignancy.

Unfractionated Heparin Promotes Osteoclast Formation in Vitro by Inhibiting Osteoprotegerin Activity

Heparin has been proven to enhance bone resorption and induce bone loss. Since osteoclasts play a pivotal role in bone resorption, the effect of heparin on osteoclastogenesis needs to be clarified. Since osteocytes are the key modulator during osteoclastogenesis, we evaluated heparin’s effect on osteoclastogenesis in vitro by co-culturing an osteocyte cell line (MLO-Y4) and pre-osteoclasts (RAW264.7). In this co-culture system, heparin enhanced osteoclastogenesis and osteoclastic bone resorption while having no influence on the production of RANKL (receptor activator of NFκB ligand), M-CSF (macrophage colony-stimulating factor), and OPG (osteoprotegerin), which are three main regulatory factors derived from osteocytes. According to previous studies, heparin could bind specifically to OPG and inhibit its activity, so we hypothesized that this might be a possible mechanism of heparin activity. To test this hypothesis, osteoclastogenesis was induced using recombinant RANKL or MLO-Y4 supernatant. We found that heparin has no effect on RANKL-induced osteoclastogenesis (contains no OPG). However, after incubation with OPG, the capacity of MLO-Y4 supernatant for supporting osteoclast formation was increased. This effect disappeared after OPG was neutralized and reappeared after OPG was replenished. These results strongly suggest that heparin promotes osteocyte-modulated osteoclastogenesis in vitro, at least partially, through inhibiting OPG activity.

Multiple myeloma-derived MMP-13 mediates osteoclast fusogenesis and osteolytic disease

Multiple myeloma (MM) cells secrete osteoclastogenic factors that promote osteolytic lesions; however, the identity of these factors is largely unknown. Here, we performed a screen of human myeloma cells to identify pro-osteoclastogenic agents that could potentially serve as therapeutic targets for ameliorating MM-associated bone disease. We found that myeloma cells express high levels of the matrix metalloproteinase MMP-13 and determined that MMP-13 directly enhances osteoclast multinucleation and bone-resorptive activity by triggering upregulation of the cell fusogen DC-STAMP. Moreover, this effect was independent of the proteolytic activity of the enzyme. Further, in mouse xenograft models, silencing MMP-13 expression in myeloma cells inhibited the development of osteolytic lesions. In patient cohorts, MMP-13 expression was localized to BM-associated myeloma cells, while elevated MMP-13 serum levels were able to correctly predict the presence of active bone disease. Together, these data demonstrate that MMP-13 is critical for the development of osteolytic lesions in MM and that targeting the MMP-13 protein - rather than its catalytic activity - constitutes a potential approach to mitigating bone disease in affected patients.

Targeting truncated RXRα for cancer therapy

Retinoid X receptor-alpha (RXRα), a unique member of the nuclear receptor superfamily, is a well-established drug target, representing one of the most important targets for pharmacologic interventions and therapeutic applications for cancer. However, how RXRα regulates cancer cell growth and how RXRα modulators suppress tumorigenesis are poorly understood. Altered expression and aberrant function of RXRα are implicated in the development of cancer. Previously, several studies had demonstrated the presence of N-terminally truncated RXRα (tRXRα) proteins resulted from limited proteolysis of RXRα in tumor cells. Recently, we discovered that overexpression of tRXRα can promote tumor growth by interacting with tumor necrosis factor-alpha-induced phosphoinositide 3-kinase and NF-κB signal transduction pathways. We also identified nonsteroidal anti-inflammatory drug Sulindac and analogs as effective inhibitors of tRXRα activities via a unique binding mechanism. This review discusses the emerging roles of tRXRα and modulators in the regulation of cancer cell survival and death as well as inflammation and our recent understanding of tRXRα regulation by targeting the alternate binding sites on its surface.

Aspirin Suppresses the Growth and Metastasis of Osteosarcoma through the NF-κB Pathway

PURPOSE

Aspirin has recently been reported to reduce both the incidence and the risk of metastasis in colon cancer. However, there is no evidence at the cellular levels or in the animal models for such an effect of aspirin on cancer metastasis.

EXPERIMENTAL DESIGN

MTT assay, colony formation assay, and apoptosis assay were employed to analyze the effects of aspirin on the osteosarcoma cell viability in vitro. The NF-κB activity was measured by the NF-κB p65 luciferase reporter. Western blotting was used to analyze the proteins in cells. The migration and invasion abilities of osteosarcoma cells in vitro were measured by the Transwell assay. Xenograft-bearing mice were used to assess the roles of aspirin in both tumor growth and metastasis of osteosarcoma in vivo (n = 5-8 mice/group). An unpaired Student t test or ANOVA with the Bonferroni post hoc test were used for the statistical comparisons.

RESULTS

Aspirin reduced cell viability in a dose- and time-dependent manner in osteosarcoma cell lines, and aspirin synergistically sensitized osteosarcoma cells to cisplatin (DDP) in vitro and in vivo (P < 0.001). Moreover, aspirin markedly repressed the migration and invasion of osteosarcoma cells in vitro (P < 0.001), and dramatically diminished the occurrence of osteosarcoma xenograft metastases to the lungs in vivo (P < 0.001). Mechanistically, aspirin diminishes osteosarcoma migration, invasion, and metastasis through the NF-κB pathway.

CONCLUSIONS

Aspirin suppresses both the growth and metastasis of osteosarcoma through the NF-κB pathway at the cellular level and in the animal models.

Suppression of NF-κB activation by gentian violet promotes osteoblastogenesis and suppresses osteoclastogenesis

Skeletal mass is regulated by the coordinated action of bone forming osteoblasts and bone resorbing osteoclasts. Accelerated rates of bone resorption relative to bone formation lead to net bone loss and the development of osteoporosis, a devastating disease that predisposes the skeleton to fractures. Bone fractures are associated with significant morbidity and in the case of hip fractures, high mortality. Gentian violet (GV), a cationic triphenylmethane dye, has long been used as an antifungal and antibacterial agent and is presently under investigation as a potential chemotherapeutic and antiangiogenic agent. However, effects on bone cells have not been previously reported and the mechanisms of action of GV, are poorly understood. In this study we show that GV suppresses receptor activator of NF-κB ligand (RANKL)-induced differentiation of RAW264.7 osteoclast precursors into mature osteoclasts, but paradoxically stimulates the differentiation of MC3T3 cells into mineralizing osteoblasts. These actions stem from the capacity of GV to suppress activation of the nuclear factor kappa B (NF-κB) signal transduction pathway that is required for osteoclastogenesis, but inhibitory to osteoblast differentiation and activity. Our data reveal that GV is an inhibitor of NF-κB activation and may hold promise for modulation of bone turnover to promote a balance between bone formation and bone resorption, favorable to gain of bone mass.

Targeting cannabinoid receptor-2 pathway by phenylacetylamide suppresses the proliferation of human myeloma cells through mitotic dysregulation and cytoskeleton disruption

Cannabinoid receptor-2 (CB2) is expressed dominantly in the immune system, especially on plasma cells. Cannabinergic ligands with CB2 selectivity emerge as a class of promising agents to treat CB2-expressing malignancies without psychotropic concerns. In this study, we found that CB2 but not CB1 was highly expressed in human multiple myeloma (MM) and primary CD138+ cells. A novel inverse agonist of CB2, phenylacetylamide but not CB1 inverse agonist SR141716, inhibited the proliferation of human MM cells (IC50 : 0.62 ∼ 2.5 μM) mediated by apoptosis induction, but exhibited minor cytotoxic effects on human normal mononuclear cells. CB2 gene silencing or pharmacological antagonism markedly attenuated phenylacetylamide's anti-MM effects. Phenylacetylamide triggered the expression of C/EBP homologous protein at the early treatment stage, followed by death receptor-5 upregulation, caspase activation, and β-actin/tubulin degradation. Cell cycle related protein cdc25C and mitotic regulator Aurora A kinase were inactivated by phenylacetylamide treatment, leading to an increase in the ratio inactive/active cdc2 kinase. As a result, phosphorylation of CDK substrates was decreased, and the MM cell mitotic division was largely blocked by treatment. Importantly, phenylacetylamide could overcome the chemoresistance of MM cells against dexamethasone or melphalan. Thus, targeting CB2 may represent an attractive approach to treat cancers of immune origin.

Regulation of the nongenomic actions of retinoid X receptor-α by targeting the coregulator-binding sites

Retinoid X receptor-α (RXRα), a unique member of the nuclear receptor superfamily, represents an intriguing and unusual target for pharmacologic interventions and therapeutic applications in cancer, metabolic disorders and neurodegenerative diseases. Despite the fact that the RXR-based drug Targretin (bexarotene) is currently used for treating human cutaneous T-cell lymphoma and the fact that RXRα ligands (rexinoids) show beneficial effects in the treatment of cancer and diseases, the therapeutic potential of RXRα remains unexplored. In addition to its conventional transcription regulation activity in the nucleus, RXRα can act in the cytoplasm to modulate important biological processes, such as mitochondria-dependent apoptosis, inflammation, and phosphatidylinositol 3-kinase (PI3K)/AKT-mediated cell survival. Recently, new small-molecule-binding sites on the surface of RXRα have been identified, which mediate the regulation of the nongenomic actions of RXRα by a class of small molecules derived from the nonsteroidal anti-inflammatory drug (NSAID) Sulindac. This review discusses the emerging roles of the nongenomic actions of RXRα in the RXRα signaling network, and their possible implications in cancer, metabolic and neurodegenerative disorders, as well as our current understanding of RXRα regulation by targeting alternate binding sites on its surface.

Antagonism of cannabinoid receptor 2 pathway suppresses IL-6-induced immunoglobulin IgM secretion

Background

Cannabinoid receptor 2 (CB2) is expressed predominantly in the immune system, particularly in plasma cells, raising the possibility that targeting the CB2 pathway could yield an immunomodulatory effect. Although the role of CB2 in mediating immunoglobulin class switching has been reported, the effects of targeting the CB2 pathway on immunoglobulin secretion per se remain unclear.

Methods

Human B cell line SKW 6.4, which is capable of differentiating into IgM-secreting cells once treated with human IL-6, was employed as the cell model. SKW 6.4 cells were incubated for 4 days with CB2 ligands plus IL-6 (100 U/ml). The amount of secreted IgM was determined by an ELISA. Cell proliferation was determined by the ³H-Thymidine incorporation assay. Signal molecules involved in the modulation of IgM secretion were examined by real-time RT-PCR and Western blot analyses or by using their specific inhibitors.

Results

We demonstrated that CB2 inverse agonists SR144528 and AM630, but not CB2 agonist HU308 or CB1 antagonist SR141716, effectively inhibited IL-6-induced secretion of soluble IgM without affecting cell proliferation as measured by thymidine uptake. SR144528 alone had no effects on the basal levels of IgM in the resting cells. These effects were receptor mediated, as pretreatment with CB2 agonist abrogated SR144528-mediated inhibition of IL-6 stimulated IgM secretion. Transcription factors relevant to B cell differentiation, Bcl-6 and PAX5, as well as the protein kinase STAT3 pathway were involved in the inhibition of IL-6-induced IgM by SR144528.

Conclusions

These results uncover a novel function of CB2 antagonists and suggest that CB2 ligands may be potential modulators of immunoglobulin secretion.

Novel triaryl sulfonamide derivatives as selective cannabinoid receptor 2 inverse agonists and osteoclast inhibitors: discovery, optimization, and biological evaluation

Cannabinoid receptors have gained increasing attention as drug targets for developing potential therapeutic ligands. Here, we report the discovery and optimization of triaryl sulfonamides as a novel series possessing significant CB2 receptor affinity and selectivity. Four sets of triaryl ligands were designed and synthesized for further structural modifications and led to the identification of eight compounds as potent and selective CB2 inverse agonists with high binding affinity (CB2K(i) < 10 nM). Especially, compound 57 exhibited the strongest binding affinity on the CB2 receptor (CB2K(i) of 0.5 nM) and the best selectivity over the CB1 receptor (selectivity index of 2594). Importantly, 57 also showed potent inhibitory activity on osteoclast formation, and it was confirmed by a cell viability assay that the inhibition effects were not derived from the cytotoxicity. Finally, 3D QSAR studies confirmed our SAR findings that three bulky groups play an important role for CB2 receptor binding affinity.

The Role of Inflammatory Cytokines, the RANKL/OPG Axis, and the Immunoskeletal Interface in Physiological Bone Turnover and Osteoporosis

Although it has long been recognized that inflammation, a consequence of immune-driven processes, significantly impacts bone turnover, the degree of centralization of skeletal and immune functions has begun to be dissected only recently. It is now recognized that formation of osteoclasts, the bone resorbing cells of the body, is centered on the key osteoclastogenic cytokine, receptor activator of NF- κ B ligand (RANKL). Although numerous inflammatory cytokines are now recognized to promote osteoclast formation and skeletal degradation, with just a few exceptions, RANKL is now considered to be the final downstream effector cytokine that drives osteoclastogenesis and regulates osteoclastic bone resorption. The biological activity of RANKL is moderated by its physiological decoy receptor, osteoprotegerin (OPG). New discoveries concerning the sources and regulation of RANKL and OPG in physiological bone turnover as well as under pathological (osteoporotic) conditions continue to be made, opening a window to the complex regulatory processes that control skeletal integrity and the depth of integration of the skeleton within the immune response. This paper will examine the interconnection between bone turnover and the immune system and the implications thereof for physiological and pathological bone turnover.

Lead discovery, chemistry optimization, and biological evaluation studies of novel biamide derivatives as CB2 receptor inverse agonists and osteoclast inhibitors

N,N'-((4-(Dimethylamino)phenyl)methylene)bis(2-phenylacetamide) was discovered by using 3D pharmacophore database searches and was biologically confirmed as a new class of CB(2) inverse agonists. Subsequently, 52 derivatives were designed and synthesized through lead chemistry optimization by modifying the rings A-C and the core structure in further SAR studies. Five compounds were developed and also confirmed as CB(2) inverse agonists with the highest CB(2) binding affinity (CB(2)K(i) of 22-85 nM, EC(50) of 4-28 nM) and best selectivity (CB(1)/CB(2) of 235- to 909-fold). Furthermore, osteoclastogenesis bioassay indicated that PAM compounds showed great inhibition of osteoclast formation. Especially, compound 26 showed 72% inhibition activity even at the low concentration of 0.1 μM. The cytotoxicity assay suggested that the inhibition of PAM compounds on osteoclastogenesis did not result from its cytotoxicity. Therefore, these PAM derivatives could be used as potential leads for the development of a new type of antiosteoporosis agent.

The bone anabolic carotenoid p-hydroxycinnamic acid promotes osteoblast mineralization and suppresses osteoclast differentiation by antagonizing NF-κB activation

Numerous plant derived nutritional factors including p-hydroxycinnamic acid (HCA), a member of the carotenoid family, have long been held to possess bone protective properties. Studies in animals have provided a mechanistic basis for these observations by demonstrating the capacity of HCA to promote bone formation and suppress bone resorption in vivo. However, the molecular mechanism by which HCA achieves these effects remains unclear. We have demonstrated that a centralized mechanism by which several other nutritional factors achieve similar effects is through modulation of the nuclear factor-κB (NF-κB) signal transduction pathway. NF-κB activation is essential for osteoclast formation and resorption but potently antagonizes osteoblast differentiation and mineralization. In this study we demonstrate that HCA does indeed antagonize the activation of NF-κB by the key osteoclastogenic cytokine receptor activator of NF-κB (RANKL) in RAW264.7 osteoclast precursors, suppressing their differentiation into osteoclasts. Furthermore, HCA augmented the in vitro differentiation of MC3T3 preosteoblastic cells into mineralizing osteoblasts and relieved the inhibitory action of tumor necrosis factor-α (TNF-α)-induced NF-κB signaling on transforming growth factor-β (TGF-β)- or bone morphogenetic protein-2 (BMP-2)-induced Smad activation, an important pathway in osteoblast commitment and differentiation. Our data provide a mechanism to explain the dual pro-anabolic and anti-catabolic activities of HCA.

Targeting the microtubular network as a new antimyeloma strategy

We identified nocodazole as a potent antimyeloma drug from a drug screening library provided by the Multiple Myeloma Research Foundation. Nocodazole is a benzimidazole that was originally categorized as a broad-spectrum anthelmintic drug with antineoplastic properties. We found that nocodazole inhibited growth and induced apoptosis of primary and multiresistant multiple myeloma cells cultured alone and in the presence of bone marrow stromal cells. Nocodazole caused cell-cycle prophase and prometaphase arrest accompanied by microtubular network disarray. Signaling studies indicated that increased expression of Bim protein and reduced X-linked inhibitor of apoptosis protein and Mcl-1(L) levels were involved in nocodazole-induced apoptosis. Further investigation showed Bcl-2 phosphorylation as a critical mediator of cell death, triggered by the activation of c-jun-NH(2) kinase (JNK) instead of p38 kinase or extracellular signal-regulated kinases. Treatment with JNK inhibitor decreased Bcl-2 phosphorylation and subsequently reduced nocodazole-induced cell death. Nocodazole combined with dexamethasone significantly inhibited myeloma tumor growth and prolonged survival in a human xenograft mouse model. Our studies show that nocodazole has potent antimyeloma activity and that targeting the microtubular network might be a promising new treatment approach for multiple myeloma.

Two novel aspirin analogues show selective cytotoxicity in primary chronic lymphocytic leukaemia cells that is associated with dual inhibition of Rel A and COX-2

OBJECTIVES

Non-steroidal anti-inflammatory drugs have been shown to induce apoptosis in primary B-cell chronic lymphocytic leukaemia (CLL) cells, but the molecular mechanisms that underpin this observation have not been fully elucidated. Here, we have analysed the effect two novel aspirin analogues, 2-hydroxy benzoate zinc (2HBZ) and 4-hydroxy benzoate zinc (4HBZ), on primary CLL samples.

MATERIALS AND METHODS

Cytotoxic effects of 2HBZ and 4HBZ were analysed in primary CLL cells derived from 52 patients, and normal B- and T-lymphocytes. Mechanisms of action of these agents were also elucidated.

RESULTS

Both analogues induced apoptosis in a dose-dependent and time-dependent manner. Apoptosis was associated with activation of caspase-3 that could be partially abrogated by the caspase-9 inhibitor (Z-LEHD.fmk). Importantly, both agents demonstrated preferential cytotoxicity in CLL cells when compared to normal B- and T-lymphocytes. In terms of their molecular mechanisms of action, 4HBZ and 2HBZ inhibited COX-2 transcription and protein expression and this was associated with upstream inhibition of transcription factor Rel A. Co-culture of CLL cells with CD40 ligand-expressing mouse fibroblasts significantly increased COX-2 expression and inhibited spontaneous apoptosis. Importantly, the most potent analogue, 4HBZ, overcame pro-survival effects of the co-culture system and significantly repressed COX-2. Finally, elevated COX-2 expression was associated with poor prognostic subsets and increased sensitivity to 4HBZ.

CONCLUSIONS

Our results demonstrate therapeutic potential of 4HBZ and are consistent with a mechanism involving suppression of Rel A nuclear translocation and inhibition of COX-2 transcription.

IMiD immunomodulatory compounds block C/EBP{beta} translation through eIF4E down-regulation resulting in inhibition of MM

Immunomodulatory derivatives of thalidomide (IMiD compounds), such as pomalidomide and lenalidomide, are highly active in multiple myeloma (MM) treatment. However, the precise mechanisms of action and resistance in MM are unresolved. Here we show that IMiD compounds down-regulate CCAAT/enhancer-binding protein-β (C/EBPβ) resulting in abrogation of cell proliferation. Overexpression of C/EBPβ rescued MM cells from IMiD-induced inhibition of proliferation, indicating that C/EBPβ is critical in mediating antiproliferative effects. IMiD-induced decrease of C/EBPβ protein led to impaired transcription of interferon regulatory factor 4 (IRF4). Down-regulation of IRF4 by lenalidomide was confirmed by longitudinal studies of bone marrow samples from 23 patients obtained before and during lenalidomide treatment using CD138⁺/IRF4⁺ double labeling. In contrast to down-regulation of C/EBPβ protein, IMiD compounds did not alter C/EBPβ mRNA levels or protein stability, suggesting translational regulation of C/EBPβ. We could demonstrate that C/EBPβ protein expression is under eIF4E-translational control in MM. Furthermore, inhibition of the eIF4E-C/EBPβ axis by IMiD compounds was not observed in IMiD-resistant MM cells. However, targeting translation at a different level by inhibiting eukaryotic translation initiation factor 4E-binding protein 1 phosphorylation overcame resistance, suggesting that this pathway is critical and might be a target to overcome drug resistance.

NFkappaB: a promising target for natural products in cancer chemoprevention

The transcription factor nuclear factor kappa B (NFkappaB) is found in nearly all animal cell types. It is involved in cellular responses to stimuli such as stress, cytokines, free radicals, ultraviolet irradiation, oxidized LDL and microbial antigens, and has been shown to regulate the expression of a number of genes including bcl-2, bcl-xl, cIAP, suvivin, TRAF, COX-2, MMP-9, iNOS and cell cycle-regulatory components. Many carcinogens, inflammatory agents and tumor promoters have been shown to activate NFkappaB, and resulting tumors demonstrate misregulated NFkappaB. Incorrect regulation of NFkappaB has been linked to inflammatory and autoimmune diseases, septic shock, viral infection and improper immune development. Aberrant regulation of NFkappaB is involved in cancer development and progression as well as in drug resistance. Inhibitors of NFkappaB mediate effects potentially leading to antitumor responses or greater sensitivity to the action of antitumor agents. Tools have been developed for the rapid assessment of NFkappaB activity, so in concert with a better understanding of NFkappaB activation mechanisms, many agents capable of suppressing NFkappaB activation have been identified. The present article focuses on the functions of NFkappaB, its role in human cancer and the therapeutic potential and benefit of targeting NFkappaB by natural products in cancer chemoprevention.

Effects of NSAIDs on Differentiation and Function of Human and Murine Osteoclasts - Crucial 'Human Osteoclastology'

Osteoclasts play a critical role in both normal bone metabolism and bone resorption in the joints of patients with rheumatoid arthritis. It has been reported that non-steroidal anti-inflammatory drugs (NSAIDs) inhibit murine osteoclastogenesis in vitro and murine arthritis models in vivo, but not the destruction of joints of patients with rheumatoid arthritis. In the current review article, we review the recent findings in the effect of NSAIDs on the formation and function of human and murine osteoclasts both in vitro and in vivo, underlining the importance of studies using human osteoclasts. Since 2009, we have suggested a novel term ‘human osteoclastology’.

Immunomodulatory derivatives induce PU.1 down-regulation, myeloid maturation arrest, and neutropenia

The immunomodulatory drugs (IMiDs) lenalidomide and pomalidomide yield high response rates in patients with multiple myeloma, but the use of IMiDs in multiple myeloma is associated with neutropenia and increased risk for venous thromboembolism (VTE) by mechanisms that are unknown. We show that IMiDs down-regulate PU.1, a key transcription factor involved in granulocyte differentiation in vitro and in patients treated with lenalidomide. Loss of PU.1 results in transient maturation arrest with medullary accumulation of immature myeloid precursors and subsequent neutropenia. Accumulation of promyelocytes leads to high levels of the platelet aggregation agonist, cathepsin G stored in the azurophilic granules of promyelocytes. High levels of cathepsin G subsequently may increase the risk of VTE. To our knowledge, this is the first report investigating the underlying mechanism of IMiD-induced neutropenia and increased risk of VTE in multiple myeloma.

Is NF-kappaB a good target for cancer therapy? Hopes and pitfalls

Nuclear factor kappaB (NF-kappaB) transcription factors have a key role in many physiological processes such as innate and adaptive immune responses, cell proliferation, cell death, and inflammation. It has become clear that aberrant regulation of NF-kappaB and the signalling pathways that control its activity are involved in cancer development and progression, as well as in resistance to chemotherapy and radiotherapy. This article discusses recent evidence from cancer genetics and cancer genome studies that support the involvement of NF-kappaB in human cancer, particularly in multiple myeloma. The therapeutic potential and benefit of targeting NF-kappaB in cancer, and the possible complications and pitfalls of such an approach, are explored.

Bone marrow microenvironment and the identification of new targets for myeloma therapy

The development of multiple myeloma (MM) is a complex multi-step process involving both early and late genetic changes in the tumor cell as well as selective supportive conditions by the bone marrow (BM) microenvironment. Indeed, it is now well established that MM cell-induced disruption of the BM homeostasis between the highly organized cellular and extracellular compartments supports MM cell proliferation, survival, migration and drug resistance through activation of various signaling (for example, PI3K/Akt, JAK/Stat-, Raf/MEK/MAPK-, NFkappaB- and Wnt-) pathways. Based on our enhanced understanding of the functional importance of the MM BM microenvironment and its inter-relation with the MM cell resulting in homing, seeding, proliferation and survival, new molecular targets have been identified and derived treatment regimens in MM have already changed fundamentally during recent years. These agents include thalidomide, its immunomodulatory derivative lenalidomide and the proteasome inhibitor bortezomib, which mediate tumor cytotoxicity in the BM milieu. Ongoing studies are further delineating MM pathogenesis in the BM to enhance cytotoxicity, avoid drug resistance and improve patient outcome.

The role of non-steroidal anti-inflammatory drugs in the risk of development and treatment of hematologic malignancies

Non-steroidal anti-inflammatory drugs (NSAIDs) comprise the group of structurally diverse but similarly acting compounds that are used for relieving signs and symptoms of inflammation, especially in treatment of rheumatic diseases. Recent reports suggested potential association between regular use of NSAIDs and the risk of development of hematological malignancies. However, the data distinctly differ depending on type of NSAID used, period of its administration and type of malignancy. Regular use of aspirin and other NSAIDs was shown to correlate with reduced risk of lymphoid malignancies. Frequent use of aspirin was found to be associated with decreased risk of acute leukemia (AL) development. In contrast, correlation between long-term acetaminophen usage and increased incidence of AL and multiple myeloma (MM) was indicated. On the other hand, NSAIDs were found to exert anti-cancer effects, inhibiting proliferation and invasive growth or inducing cell apoptosis in several tumors, including hematologic malignancies. One of those agents, non-cyclooxygenase 2-inhibiting R-enantiomer of etodolac (SDX-101), exerts cytotoxic effects against chronic lymphocytic leukemia (CLL) and MM cells, and is currently investigated in phase II clinical trial in CLL. The indole-pyran analogue of SDX-101, SDX-308 (CEP-18082), showed more potent cytotoxicity than SDX-101 against MM cells and inhibited osteoclast formation and activity of mature osteoclasts. Thus, SDX-308 may be an ideal agent for bone disease in MM and related diseases. Another analogue of SDX-101, SDX-309, showed also significant anti-tumor activity in first preclinical studies. The potential role of NSAIDs in prevention and treatment of hematologic malignancies is the subject of this review.

The histone deacetylase inhibitor, PXD101, potentiates bortezomib-induced anti-multiple myeloma effect by induction of oxidative stress and DNA damage

Clinical trials have shown the high anti-myeloma activity of the proteasome inhibitor bortezomib. The present study examined the activity of bortezomib combined with PXD101, a histone deacetylase inhibitor, against multiple myeloma (MM) and osteoclastogenesis. Treatment of myeloma cell lines with combinations of bortezomib and PXD101 led to synergistic inhibition of proliferation and induction of cell death. The combination significantly decreased the viability of primary human CD138(+) myeloma cells but not of bone marrow mononuclear cells. Further studies showed a dose-dependent activation of caspases-3, -8 and -9 and nuclear fragmentation in myeloma cells. Bortezomib/PXD101 treatment markedly triggered reactive oxygen species (ROS) generation that was accompanied by p53, H2A.X and p38-mitogen-activated protein kinase phosphorylation. ROS generation could be blocked by the free radical scavenger N-acetyl-L-cysteine. The combination of bortezomib and PXD101 also resulted in synergistic inhibition of osteoclast formation. In conclusion, bortezomib and PXD101 have different molecular targets. The combination induces cell death in myeloma cells via ROS-mediated DNA damage and also inhibits osteoclastogenesis. Therefore, this study provides the rationale for the clinical evaluation of bortezomib combined with PXD101 in patients with MM.

SDX-308 and SDX-101, Non-Steroidal Anti-Inflammatory Drugs, as Therapeutic Candidates for Treating Hematologic Malignancies Including Myeloma

Non-steroidal anti-inflammatory drugs have been shown to inhibit carcinogenesis in colon cancer, and to induce apoptosis in a variety of tumor cell lines. Some anti-tumor effects are thought to be related to their cyclooxygenase-2-inhibitory activity, but recent studies have shown that non-steroidal anti-inflammatory drugs exert their anti-tumor effect via cyclooxygenase-2-independent mechanism. SDX-308 (CEP-18082) is a non-cyclooxygenase-2-inhibiting indole-pyran analog and is structurally related to SDX-101, an R-enantiomer of etodolac. SDX-308 has a potent anti-myeloma effect and shows synergism in combination with other drugs for the treatment of chronic lymphocytic leukemia. In addition SDX-308 inhibits osteoclast formation and activity and thereby might be an attractive drug for the treatment of diseases with increased osteoclast activity such as osteolytic lesions in multiple myeloma and metastatic carcinomas, as well as osteoporosis. This review covers future application of SDX-308 as an anti-myeloma drug regulating increased osteoclast activity.

Treatment strategies for bone disease

Multiple myeloma is characterized by extensive bone destruction with little or no new bone formation. A multiplicity of factors including receptor activator NF-kappaB (RANKL), macrophage inflammatory protein-1alpha, interleukin-3 and interleukin-6 can induce osteoclast formation in myeloma and drive the bone destructive process. Furthermore, factors are also produced either in the microenvironment or by myeloma cells themselves, which inhibit osteoblast differentiation and new bone formation. The combination of increased osteoclast formation with little or no bone repair in response to the previous bone destruction explains the severity of the bone disease in myeloma. Studies of the pathophysiology of myeloma bone disease have identified several novel therapeutic targets. These include antibodies to RANKL, chemokine receptor antagonists, which block the effects of chemokines on osteoclast differentiation and proteasome antagonists, which can affect both RANKL production and osteoprotegerin levels as well as inhibit osteoclast and enhance osteoblast differentiation. In addition, many of the new biologic agents being used for the treatment of patients with myeloma also further inhibit the bone destructive process. New therapies that can target both the tumor as well as the severe bone disease should be on the horizon to treat this devastating complication of myeloma.