Interpreting the molecular biology and clinical behavior of multiple myeloma in the context of global gene expression profiling

Molecular mechanisms, current management and next generation therapy in myeloma bone disease

Multiple myeloma (MM) bone disease is a major cause of morbidity and mortality in MM patients and persists even in patients in remission. This bone disease is caused by an uncoupling of bone remodeling, with increased osteoclast and decreased osteoblast activity and formation, culminating in lytic bone destruction. Bisphosphonates are the current standard of care but new therapies are needed. As the molecular mechanisms controlling MM bone disease are increasingly well understood, new therapeutic targets are extensively explored in the preclinical setting and initial clinical trials with novel compounds now show promising results. In this review, we will provide a comprehensive overview of the biology of MM bone disease, summarize its current clinical management and discuss preclinical and clinical data on next generation therapies.

Suboptimal B-cell antigen receptor signaling activity in vivo elicits germinal center counterselection mechanisms

Syk and Zap-70 constitute a closely related nonreceptor protein tyrosine kinase family, of which both members are functionally indispensable for conferring their respective antigen receptors with enzymatic activity. In this study, we analyze the impact of altering BCR signaling output on B-cell germinal center (GC) fate selection by constitutive, as well as inducible, monoallelic Syk kinase loss in the presence of a Zap-70 knock-in rescue allele. Cre-mediated Syk deletion in Syk(flox/Zap-70) B cells lowers pErk, but not pAkt-mediated signaling. Surprisingly, the use of a B-cell-specific constitutive mb1-cre deleter mouse model showed that a small cohort of peripheral Syk(flox/Zap-70);mb1-cre B cells efficiently circumvents deletion, which ultimately favors these Syk-sufficient cells to contribute to the GC reaction. Using a developmentally unbiased Syk(flox/Zap-70);mb1-creER(T2) approach in combination with an inducible tdRFP allele, we further demonstrate that this monoallelic deletion escape is not fully explained by leakiness of Cre expression, but is possibly the result of differential Syk locus accessibility in maturing B cells. Altogether, this underscores the importance of proper Syk kinase function not only during central and peripheral selection processes, but also during GC formation and maintenance.

Bone marrow mast cell density correlates with serum levels of VEGF and CXC chemokines ENA-78 and GRO-α in multiple myeloma

Angiogenesis is a crucial process in growth and progression of multiple myeloma (MM). Mast cells (MCs) play an important role in MM angiogenesis. Various angiogenic mediators secreted by MCs regulate endothelial cell proliferation and function. Among them, ELR(+) CXC chemokines, such as growth-related oncogen-alpha (GRO-α) and epithelial neutrophil activating protein-78 (ENA-78), have been described as potential mediators in regulation of angiogenesis. The purpose of the study was to quantify MCs in bone marrow (BM) biopsies of MM patients, expressed as MC density (MCD), and correlate it with serum concentrations of vascular endothelial factor (VEGF), GRO-α, ENA-78. Fifty-four newly diagnosed MM patients and 22 healthy controls were studied. Tryptase was used for the immunohistochemical stain of MCs. VEGF, GRO-α, and ENA-78 were measured in sera by ELISA. MCD and serum levels of GRO-α, ENA-78, and VEGF were significantly higher in MM patients compared to controls (p<0.001 in all cases). MCD was significantly increasing with increased stage of the disease (p<0.001). Furthermore, significant correlations were found between MCD with VEGF, GRO-α, and ENA-78. These findings support that MCs participate in the pathophysiology of MM and is implicated in the angiogenic process and disease progression.

Characterization of the molecular mechanism of the bone-anabolic activity of carfilzomib in multiple myeloma

Carfilzomib, the next generation of proteasome inhibitor, may increase osteoblast-related markers in patients with multiple myeloma, but the molecular mechanism of its effect on mesenchymal stem cell differentiation to osteoblasts remains unknown. Herein, we demonstrated that carfilzomib significantly promoted mesenchymal stem cell differentiation into osteoblasts. In osteoprogenitor cells and primary mesenchymal stem cells from patients with myeloma, carfilzomib induced increases in alkaline phosphatase activity, matrix mineralization, and calcium deposition via Wnt-independent activation of β-catenin/TCF signaling. Using affinity pull-down assays with immunoblotting analysis and immunofluorescence, we found that carfilzomib induced stabilization of both free and active forms of β-catenin in a time- and dose-dependent manner that was not associated with β-catenin transcriptional regulation. Nuclear translocation of β-catenin protein was associated with TCF transcriptional activity that was independent of the effects of GSK3β-activation and of signaling induced by 19 Wnt ligands, 10 Frizzled receptors, and LRP5/6 co-receptors. Blocking activation of β-catenin/TCF signaling by dominant negative TCF1 or TCF4 attenuated carfilzomib-induced matrix mineralization. Thus, carfilzomib induced osteoblast differentiation via Wnt-independent activation of the β-catenin/TCF pathway. These results provide a novel molecular mechanism critical to understanding the anabolic role of carfilzomib on myeloma-induced bone disease.

Sarcosine as a potential prostate cancer biomarker--a review

Prostate cancer (CaP) is the most common type of tumour disease in men. Early diagnosis of cancer of the prostate is very important, because the sooner the cancer is detected, the better it is treated. According to that fact, there is great interest in the finding of new markers including amino acids, proteins or nucleic acids. Prostate specific antigen (PSA) is commonly used and is the most important biomarker of CaP. This marker can only be detected in blood and its sensitivity is approximately 80%. Moreover, early stages cannot be diagnosed using this protein. Currently, there does not exist a test for diagnosis of early stages of prostate cancer. This fact motivates us to find markers sensitive to the early stages of CaP, which are easily detected in body fluids including urine. A potential is therefore attributed to the non-protein amino acid sarcosine, which is generated by glycine-N-methyltransferase in its biochemical cycle. In this review, we summarize analytical methods for quantification of sarcosine as a CaP marker. Moreover, pathways of the connection of synthesis of sarcosine and CaP development are discussed.

Characterization of cyclin E expression in multiple myeloma and its functional role in seliciclib-induced apoptotic cell death

Multiple Myeloma (MM) is a lymphatic neoplasm characterized by clonal proliferation of malignant plasma cell that eventually develops resistance to chemotherapy. Drug resistance, differentiation block and increased survival of the MM tumor cells result from high genomic instability. Chromosomal translocations, the most common genomic alterations in MM, lead to dysregulation of cyclin D, a regulatory protein that governs the activation of key cell cycle regulator – cyclin dependent kinase (CDK). Genomic instability was reported to be affected by over expression of another CDK regulator - cyclin E (CCNE). This occurs early in tumorigenesis in various lymphatic malignancies including CLL, NHL and HL. We therefore sought to investigate the role of cyclin E in MM. CCNE1 expression was found to be heterogeneous in various MM cell lines (hMMCLs). Incubation of hMMCLs with seliciclib, a selective CDK-inhibitor, results in apoptosis which is accompanied by down regulation of MCL1 and p27. Ectopic over expression of CCNE1 resulted in reduced sensitivity of the MM tumor cells in comparison to the paternal cell line, whereas CCNE1 silencing with siRNA increased the cell sensitivity to seliciclib. Adhesion to FN of hMMCLs was prevented by seliciclib, eliminating adhesion–mediated drug resistance of MM cells. Combination of seliciclib with flavopiridol effectively reduced CCNE1 and CCND1 protein levels, increased subG1 apoptotic fraction and promoted MM cell death in BMSCs co-culture conditions, therefore over-coming stroma-mediated protection. We suggest that seliciclib may be considered as essential component of modern anti MM drug combination therapy.

Patterns of expression of CD56 and CD117 on neoplastic plasma cells and association with genetically distinct subtypes of plasma cell myeloma

Plasma cell neoplasms are common hematopoietic malignancies that recently have been shown to be driven by specific genetic events. In the past decade, immunophenotyping by flow cytometry has become an important tool in the characterization of plasma cells. However, the clinical and prognostic significance of antigenic expression remains unclear. We analyzed 102 cases of plasma cell neoplasm by flow cytometric immunophenotyping for expression of CD56 and CD117 and correlated the results with immunohistochemical and cytogenetic findings. Expression of CD56 and CD117 was associated with hyperdiploidy and the absence of CD117 expression was associated with different immunoglobulin heavy chain gene (IGH) translocations. Assessment of CD117 expression on neoplastic plasma cells by flow cytometry is superior to immunohistochemistry. Simultaneous assessment of CD56 and CD117 expression by flow cytometry is a sensitive method for diagnostic evaluation of plasma cell neoplasms, and furthermore may function as a rapid adjunctive test providing independent prognostic information in the absence of cytogenetic data.

Principled sure independence screening for Cox models with ultra-high-dimensional covariates

It is rather challenging for current variable selectors to handle situations where the number of covariates under consideration is ultra-high. Consider a motivating clinical trial of the drug bortezomib for the treatment of multiple myeloma, where overall survival and expression levels of 44760 probesets were measured for each of 80 patients with the goal of identifying genes that predict survival after treatment. This dataset defies analysis even with regularized regression. Some remedies have been proposed for the linear model and for generalized linear models, but there are few solutions in the survival setting and, to our knowledge, no theoretical support. Furthermore, existing strategies often involve tuning parameters that are difficult to interpret. In this paper we propose and theoretically justify a principled method for reducing dimensionality in the analysis of censored data by selecting only the important covariates. Our procedure involves a tuning parameter that has a simple interpretation as the desired false positive rate of this selection. We present simulation results and apply the proposed procedure to analyze the aforementioned myeloma study.

Small compound 6-O-angeloylplenolin induces mitotic arrest and exhibits therapeutic potentials in multiple myeloma

Background

Multiple myeloma (MM) is a disease of cell cycle dysregulation while cell cycle modulation can be a target for MM therapy. In this study we investigated the effects and mechanisms of action of a sesquiterpene lactone 6-O-angeloylplenolin (6-OAP) on MM cells.

Methodology/Principal Findings

MM cells were exposed to 6-OAP and cell cycle distribution were analyzed. The role for cyclin B1 to play in 6-OAP-caused mitotic arrest was tested by specific siRNA analyses in U266 cells. MM.1S cells co-incubated with interleukin-6 (IL-6), insulin-like growth factor-I (IGF-I), or bone marrow stromal cells (BMSCs) were treated with 6-OAP. The effects of 6-OAP plus other drugs on MM.1S cells were evaluated. The in vivo therapeutic efficacy and pharmacokinetic features of 6-OAP were tested in nude mice bearing U266 cells and Sprague-Dawley rats, respectively. We found that 6-OAP suppressed the proliferation of dexamethasone-sensitive and dexamethasone-resistant cell lines and primary CD138+ MM cells. 6-OAP caused mitotic arrest, accompanied by activation of spindle assembly checkpoint and blockage of ubiquitiniation and subsequent proteasomal degradation of cyclin B1. Combined use of 6-OAP and bortezomib induced potentiated cytotoxicity with inactivation of ERK1/2 and activation of JNK1/2 and Casp-8/-3. 6-OAP overcame the protective effects of IL-6 and IGF-I on MM cells through inhibition of Jak2/Stat3 and Akt, respectively. 6-OAP inhibited BMSCs-facilitated MM cell expansion and TNF-α-induced NF-κB signal. Moreover, 6-OAP exhibited potent anti-MM activity in nude mice and favorable pharmacokinetics in rats.

Conclusions/Significance

These results indicate that 6-OAP is a new cell cycle inhibitor which shows therapeutic potentials for MM.

RANKL inhibition: clinical implications for the management of patients with multiple myeloma and solid tumors with bone metastases

BACKGROUND

Receptor activator of NF-kappaB ligand (RANKL) binds to RANK on the surface of osteoclast precursors and enhances their differentiation, survival and fusion, activates mature osteoclasts and inhibits their apoptosis. Osteoprotegerin (OPG) is the decoy receptor of RANKL. Disruption of the RANK/RANKL/OPG axis is implicated in bone metastases.

OBJECTIVE/METHODS

A review of the role of RANKL signaling in bone development and the rationale for targeting RANKL in treatment of bone metastases and myeloma bone disease.

RESULTS/CONCLUSIONS

In preclinical models of solid tumors and myeloma, RANKL inhibition reduced osteoclast numbers and subsequent bone resorption, prevented development of osteolytic lesions and decreased tumor burden. Preliminary clinical studies with denosumab, an anti-RANKL fully human monoclonal antibody, in patients with solid tumors with bone metastases and myeloma showed that targeting RANKL reduces osteoclastogenesis, bone resorption markers and skeletal-related events, supporting further study of this molecule and others with anti-RANKL activity.

An open-label, phase 2 trial of denosumab in the treatment of relapsed or plateau-phase multiple myeloma

RANKL is a key mediator of osteoclast differentiation, activation, and survival. Preclinical data suggest that aberrant production and activation of osteoclasts may influence proliferation of multiple myeloma (MM) cells in the bone marrow. Reports have also shown that inhibiting RANKL may have a direct effect on RANK-expressing myeloma cells and a therapeutic role in treating the disease. In mouse myeloma models, inhibition of RANKL led to reduced serum paraprotein levels and tumor burden. Based on this hypothesis, this proof-of-concept, single-arm study investigated whether RANKL inhibition with denosumab could reduce serum M-protein levels in relapsed or plateau-phase myeloma subjects. All subjects received denosumab monthly, with loading doses on days 8 and 15 of month one, until disease progression or subject discontinuation. Results of this ongoing study demonstrated that no subjects in either cohort met the protocol-defined objective response criteria of complete response (CR) or partial response (PR), but that denosumab effectively inhibited the RANKL pathway regardless of previous exposure to bisphosphonates, as evidenced by suppressed levels of the bone turnover marker, serum C-terminal telopeptide of type 1 collagen (sCTx). Eleven (21%) subjects who relapsed within 3 months before study entry maintained stable disease for up to 16.5 months. Nineteen (46%) subjects with plateau-phase myeloma maintained stable disease for up to 18.3 months. The adverse event (AE) profile for denosumab and its dosing schedule in these populations was consistent with that for advanced cancer patients receiving systemic therapy. Additional controlled clinical studies of denosumab in subjects with both relapsed and plateau-phase MM are warranted.

Anti-DKK1 mAb (BHQ880) as a potential therapeutic agent for multiple myeloma

Decreased activity of osteoblasts (OBs) contributes to osteolytic lesions in multiple myeloma (MM). The production of the soluble Wnt inhibitor Dickkopf-1 (DKK1) by MM cells inhibits OB activity, and its serum level correlates with focal bone lesions in MM. Therefore, we have evaluated bone anabolic effects of a DKK1 neutralizing antibody (BHQ880) in MM. In vitro BHQ880 increased OB differentiation, neutralized the negative effect of MM cells on osteoblastogenesis, and reduced IL-6 secretion. In a severe combined immunodeficiency (SCID)-hu murine model of human MM, BHQ880 treatment led to a significant increase in OB number, serum human osteocalcin level, and trabecular bone. Although BHQ880 had no direct effect on MM cell growth, it significantly inhibited growth of MM cells in the presence of bone marrow stromal cells (BMSCs) in vitro. This effect was associated with inhibition of BMSC/MM cell adhesion and production of IL-6. In addition, BHQ880 up-regulated beta-catenin level while down-regulating nuclear factor-kappaB (NF-kappaB) activity in BMSC. Interestingly, we also observed in vivo inhibition of MM cell growth by BHQ880 treatment in the SCID-hu murine model. These results confirm DKK1 as an important therapeutic target in myeloma and provide the rationale for clinical evaluation of BHQ880 to improve bone disease and to inhibit MM growth.

Bortezomib induces osteoblast differentiation via Wnt-independent activation of beta-catenin/TCF signaling

Inhibition of Wnt/beta-catenin/T-cell factor (TCF) signaling induces proliferation of mesenchymal stem cells and/or suppresses their differentiation into osteoblasts (OBs). Osteolysis in multiple myeloma (MM) is related to the suppression of canonical Wnt signaling caused by DKK1, a soluble inhibitor of this pathway secreted by MM cells. Bortezomib (Bzb) can induce OB differentiation in vitro and in vivo and its anti-MM efficacy linked to bone anabolic effects. However, the molecular basis of the action of Bzb on bone is not completely understood. In the present study, we show that Bzb promotes matrix mineralization and calcium deposition by osteoprogenitor cells and primary mesenchymal stem cells via Wnt-independent activation of beta-catenin/TCF signaling. Using affinity pull-down assays with immunoblotting and immunofluorescence, we found that Bzb induced stabilization of beta-catenin. Nuclear translocation of stabilized beta-catenin was associated with beta-catenin/TCF transcriptional activity that was independent of the effects of Wnt ligand-receptor-induced signaling or GSK3beta activation. Blocking the activation of beta-catenin/TCF signaling by dominant negative TCF attenuated Bzb-induced matrix mineralization. These results provide evidence that Bzb induces OB differentiation via Wnt-independent activation of beta-catenin/TCF pathway and suggest that proteasome inhibition therapy in MM may function in part by subverting tumor-induced suppression of canonical Wnt signaling in the bone microenvironment.

The role of Dickkopf-1 in bone development, homeostasis, and disease

Wnt/beta-catenin signaling is central to bone development and homeostasis in adulthood and its deregulation is associated with bone pathologies. Dickkopf-1 (DKK1), a soluble inhibitor of Wnt/beta-catenin signaling required for embryonic head development, regulates Wnt signaling by binding to the Wnt coreceptor lipoprotein-related protein-5 (LRP5)/Arrow. LRP5 mutations causing high bone mass syndromes disrupt DKK1-mediated regulation of LRP5. Forced overexpression of Dkk1 in osteoblasts causes osteopenia, disruption of the hematopoietic stem cell (HSC) niche, and defects in HSC function. Dkk1 also inhibits fracture repair. Studies suggest that DKK1 activation in osteoblasts is the underlying cause of glucocorticoid- and estrogen deficiency-mediated osteoporosis, and at least partially underlies the teratogenic effects of thalidomide on limb development. DKK1 induces proliferation of mesenchymal stem cells (MSC) in vitro and may play a role in the development of high-grade undifferentiated pleomorphic sarcomas derived from MSC and osteosarcomas. DKK1 has been implicated in causing erosive arthritis, the osteolytic phenotypes of multiple myeloma and metastatic breast cancer, and osteoblastic metastases of prostate cancer. Preclinical studies have shown that neutralizing DKK1/Dkk1 and/or enhancing Wnt/beta-catenin signaling may prove effective in treating bone pathologies. Here, we review the rapidly growing body of literature defining a pivotal role for DKK1 in bone health and disease.

Clustering of significant genes in prognostic studies with microarrays: Application to a clinical study for multiple myeloma

When a large number of genes are significant in correlating microarray gene expression data with patient prognosis, clustering of significant genes may be effective not only for further dimension reduction but also for identifying co-regulated genes that belong to the same molecular pathway related to disease biology and aggressiveness. Moreover, a reduced feature, such as the average expression across samples for a cluster of significant genes, can play an important role in reducing variance in prediction analysis. We propose a simple procedure to select gene clusters that have strong marginal association with survival outcome from a large pool of candidate hierarchical clusters of significant genes. Selected gene clusters can have better predictive capability than the other gene clusters and singleton genes. Application of such clustering to the data set from a clinical study for patients with multiple myeloma and associated microarrays is given.

The oxidative stress response regulates DKK1 expression through the JNK signaling cascade in multiple myeloma plasma cells

Multiple myeloma (MM) plasma cells, but not those from healthy donors and patients with monoclonal gammopathy of undetermined significance or other plasma cell dyscrasias involving the bone marrow, express the Wnt-signaling antagonist DKK1. We previously reported that secretion of DKK1 by MM cells likely contributes to osteolytic lesions in this disease by inhibiting Wnt signaling, which is essential for osteoblast differentiation and survival. The mechanisms responsible for activation and regulation of DKK1 expression in MM are not known. Herein, we could trace DKK1 expression changes in MM cells to perturbations in the JNK signaling cascade, which is differentially modulated through oxidative stress and interactions between MM cells with osteoclasts in vitro. Despite its role as a tumor suppressor and mediator of apoptosis in other cell types including osteoblasts, our data suggest that DKK1, a stress-responsive gene in MM, does not mediate apoptotic signaling, is not activated by TP53, and its forced overexpression could not inhibit cell growth or sensitize MM cells to apoptosis following treatment with thalidomide or lenalidomide. We conclude that specific strategies to modulate persistent activation of the JNK pathway may be beneficial in preventing disease progression and treating myeloma-associated bone disease by inhibiting DKK1 expression.

Use of single nucleotide polymorphism-based mapping arrays to detect copy number changes and loss of heterozygosity in multiple myeloma

The genetics of multiple myeloma is a vastly studied field in which techniques such as classical cytogenetics, fluorescence in situ hybridization, and comparative genomic hybridization have been used. More recently, single nucleotide polymorphism (SNP)-based mapping arrays have become available that allow the identification of regions of gain or loss as small as 2.5 kb. In addition to the increased resolution of SNP-based arrays, the detection of loss of heterozygosity is also possible. This allows the identification of loss of heterozygosity regions that arise through monosomy and recombination, resulting in uniparental disomy, which cannot be detected by conventional genetic methods. In this review, we discuss the benefits of SNP-based arrays along with some of the drawbacks and how that data can be used in conjunction with expression data to identify genes with altered expression in regions of interest.

A validated gene expression model of high-risk multiple myeloma is defined by deregulated expression of genes mapping to chromosome 1

To molecularly define high-risk disease, we performed microarray analysis on tumor cells from 532 newly diagnosed patients with multiple myeloma (MM) treated on 2 separate protocols. Using log-rank tests of expression quartiles, 70 genes, 30% mapping to chromosome 1 (P < .001), were linked to early disease-related death. Importantly, most up-regulated genes mapped to chromosome 1q, and down-regulated genes mapped to chromosome 1p. The ratio of mean expression levels of up-regulated to down-regulated genes defined a high-risk score present in 13% of patients with shorter durations of complete remission, event-free survival, and overall survival (training set: hazard ratio [HR], 5.16; P < .001; test cohort: HR, 4.75; P < .001). The high-risk score also was an independent predictor of outcome endpoints in multivariate analysis (P < .001) that included the International Staging System and high-risk translocations. In a comparison of paired baseline and relapse samples, the high-risk score frequency rose to 76% at relapse and predicted short postrelapse survival (P < .05). Multivariate discriminant analysis revealed that a 17-gene subset could predict outcome as well as the 70-gene model. Our data suggest that altered transcriptional regulation of genes mapping to chromosome 1 may contribute to disease progression, and that expression profiling can be used to identify high-risk disease and guide therapeutic interventions.

Biology and treatment of multiple myeloma

Multiple myeloma (MM) is a B cell malignancy that accounts for 10% of all hematologic cancers. In recent years much has been learned regarding the biology of the myeloma clone; specifically on the chromosomal alterations that can be more frequently found and on the involved oncogenes. It has been also demonstrated that, in MM, bone marrow microenvironment, both in its cellular (stromal cells, osteoblasts, osteoclasts, endothelia) and protein (extracellular matrix) components, plays an important role in promoting growth and survival of malignant plasma cells. Much of this knowledge will be translated into a better patients treatment; although high-dose therapy programs can be considered the treatment of choice for patients aged 70 or younger, novel drugs, targeting MM clone in its microenvironment can be incorporated into these therapeutic programs improving response rate and patients survival.

Amplification and overexpression of CKS1B at chromosome band 1q21 is associated with reduced levels of p27Kip1 and an aggressive clinical course in multiple myeloma

The molecular basis for aggressive transformation of multiple myeloma (MM) and other cancers is not completely understood. Global gene expression profiling on highly purified malignant plasma cells from 351 newly diagnosed patients with MM treated with autologous stem cell transplantation revealed a statistically significant over-representation of chromosome 1 genes in a group of 70 genes whose expression was linked to poor outcome. In particular, over-expression of CKS1B, which maps to an amplicon at 1q21 in myeloma and regulates SCF(Skp2)-mediated ubquitination and proteolysis of the cyclin dependent kinase inhibitor p27Kip1 was significantly over-expressed in patients with poor survival. Interphase fluorescence in-situ hybridization revealed that CKS1B expression was strongly correlated with DNA copy number in a subset of 197 cases (P<0.0001) with both measurements. Validated in 224 patients lacking expression analysis, CKS1B gene amplification conferred a poor prognosis (P<0.0001) and was an independent predictor of outcome in multivariate analyses (P=0.002). CKS1B mRNA and protein expression were correlated and both were inversely correlated with p27(Kip1) protein levels. RNA interference of CKS1B messenger RNA in myeloma cell lines led to reduced CKS1B mRNA and protein, an accumulation of p27Kip1, and profound growth inhibition. Based on these data we conclude that over-expression of CKS1B, mainly due to gene amplification, imparts a poor prognosis in MM, possibly as a result of enhanced degradation of p27Kip1.

The molecular classification of multiple myeloma

To better define the molecular basis of multiple myeloma (MM), we performed unsupervised hierarchic clustering of mRNA expression profiles in CD138-enriched plasma cells from 414 newly diagnosed patients who went on to receive high-dose therapy and tandem stem cell transplants. Seven disease subtypes were validated that were strongly influenced by known genetic lesions, such as c-MAF- and MAFB-, CCND1- and CCND3-, and MMSET-activating translocations and hyperdiploidy. Indicative of the deregulation of common pathways by gene orthologs, common gene signatures were observed in cases with c-MAF and MAFB activation and CCND1 and CCND3 activation, the latter consisting of 2 subgroups, one characterized by expression of the early B-cell markers CD20 and PAX5. A low incidence of focal bone disease distinguished one and increased expression of proliferation-associated genes of another novel subgroup. Comprising varying fractions of each of the other 6 subgroups, the proliferation subgroup dominated at relapse, suggesting that this signature is linked to disease progression. Proliferation and MMSET-spike groups were characterized by significant overexpression of genes mapping to chromosome 1q, and both exhibited a poor prognosis relative to the other groups. A subset of cases with a predominating myeloid gene expression signature, excluded from the profiling analyses, had more favorable baseline characteristics and superior prognosis to those lacking this signature.

High-resolution genomic profiles define distinct clinico-pathogenetic subgroups of multiple myeloma patients

To identify genetic events underlying the genesis and progression of multiple myeloma (MM), we conducted a high-resolution analysis of recurrent copy number alterations (CNAs) and expression profiles in a collection of MM cell lines and outcome-annotated clinical specimens. Attesting to the molecular heterogeneity of MM, unsupervised classification using nonnegative matrix factorization (NMF) designed for array comparative genomic hybridization (aCGH) analysis uncovered distinct genomic subtypes. Additionally, we defined 87 discrete minimal common regions (MCRs) within recurrent and highly focal CNAs. Further integration with expression data generated a refined list of MM gene candidates residing within these MCRs, thereby providing a genomic framework for dissection of disease pathogenesis, improved clinical management, and initiation of targeted drug discovery for specific MM patients.

How Wnt Signaling Affects Bone Repair by Mesenchymal Stem Cells from the Bone Marrow

Human mesenchymal stem cells (hMSCs) from bone marrow are a source of osteoblast progenitors in vivo, and under appropriate conditions they differentiate into osteoblasts ex vivo. The cells provide a convenient cell culture model for the study of osteogenic tissue repair in an experimentally accessible system. Recent advances in the field of skeletal development and osteogenesis have demonstrated that signaling through the canonical wingless (Wnt) pathway is critical for the differentiation of progenitor cell lines into osteoblasts. Inhibition of such signals can predispose hMSCs to cell cycle entry and prevent osteogenesis. Our investigation of the role of Wnt signaling in osteogenesis by hMSCs ex vivo has demonstrated that osteogenesis proceeds in response to bone morphogenic protein 2 stimulation and is sustained by Wnt signaling. In the presence of Dkk-1, an inhibitor of Wnt signaling, the cascade is disrupted, resulting in inhibition of osteogenesis. Peptide mapping studies have provided peptide Dkk-1 agonists and the opportunity for the production of blocking antibodies. Anti-Dkk-1 strategies are clinically relevant since high serum levels of Dkk-1 are thought to contribute to osteolytic lesion formation in multiple myeloma and possibly some forms of osteosarcoma. Specific inhibitors of glycogen synthetase kinase 3beta (GSK3beta), which mimic Wnt signaling, may also have a therapeutic benefit by enhancing in vitro osteogenesis despite the presence of Dkk-1. Antibodies that block Dkk-1 and GSK3beta inhibitors may provide novel opportunities for the enhancement of bone repair in a variety of human diseases such as multiple myeloma and osteosarcoma.

Using Genomics to Identify High-Risk Myeloma after Autologous Stem Cell Transplantation

Multiple myeloma is a malignancy of antibody-secreting plasma cells that expand in the bone marrow. Although high-dose therapy/autologous stem cell transplantation has become the standard of care for patients with multiple myeloma, survival is highly variable and can range from a few years to >10 years after diagnosis. Application of high-throughput genomics on a large uniformly untreated cohort of patients has revealed that activation of 1 of the 3 cyclin D genes is a universal initiating event in this disease and that acquisition of abnormalities of chromosome 1 leads to activation of CKS1B, a regulator of p27Kip1 degradation. Synergy between cyclin D2 and CKS1B, but not cyclin D1 and CKS1B, may lead to early treatment failure.

Gene expression profiling and multiple myeloma

Gene expression profiling is a powerful tool through which the biology of multiple myeloma can be dissected. We will describe in this chapter how early studies using this technology have provided meaningful insights into myeloma biology, have led to the identification of new therapeutic targets, and have identified powerful prognostic and pharmacogenomic markers. Specifically, we will demonstrate that gene expression profiling can be used to segregate myeloma patients into prognostic categories within which known IgH translocation signatures can be readily defined. We also show that expression signatures can identify patients with chromosome 13 deletion. Finally, we demonstrate that global gene expression signatures can be distilled to short lists of three genes or more which together impart clinical outcome information, which is significantly more powerful than any previously defined prognostic tool. Expression profiling has also led to the identification of a number of new therapeutic targets not only in myeloma cell survival but also in the pathogenesis of the osteolysis which is a hallmark of this disease.

Targeting receptor kinases by a novel indolinone derivative in multiple myeloma: abrogation of stroma-derived interleukin-6 secretion and induction of apoptosis in cytogenetically defined subgroups

In multiple myeloma (MM), both vascular endothelial (VEGF) and basic fibroblast growth factor (bFGF) promote tumor growth and survival. We have used the novel indolinone BIBF 1000 to study effects of simultaneous inhibition of VEGF, FGF and transforming growth factor-beta on MM cells and their interactions with bone marrow stroma cells (BMSCs). Both, in the absence and presence of myeloma-stroma cell contacts, BIBF 1000 abrogated BMSC-derived secretion of interleukin-6 (IL-6). In addition, BIBF 1000 directly induced apoptosis in t(4;14)-positive cell lines as well as in CD138+ marrow cells from patients with t(4;14) myeloma. To a similar extent, BIBF 1000 induced apoptosis in MM.1S and MM.1R cells carrying the translocation t(14;16). In case of MM.1S and other dexamethasone-sensitive t(14;16) cell lines, BIBF 1000 and dexamethasone had additive proapoptotic effects. Induction of apoptosis by BIBF 1000 was associated with inhibition of the mitogen-activated protein kinases (MAPK) pathway in t(4;14) and inhibition of the phosphatidyl-inositol-3 kinase/AKT pathway in t(14;16) cells. Apoptotic effects did not occur in t(4;14)-or t(14;16)-positive MM cells carrying n- or k-Ras mutations. The data provide the rationale for clinical evaluation of this class of targeted kinase inhibitors in MM with focus on defined cytogenetic subgroups.

Myeloma bone disease: pathophysiology and management

Bone disease is a major feature of multiple myeloma. Myeloma-induced bone destruction is the result of an increased activity of osteoclasts, which is not accompanied by a comparable increase of osteoblast function. Recent studies have revealed that new molecules such as the receptor activator of nuclear factor-kappa B (RANK), its ligand (RANKL), osteoprotegerin (OPG), and macrophage inflammatory protein-1alpha are implicated in osteoclast activation and differentiation, while proteins such as dickkopf-1 inhibit osteoblastic bone formation. These new molecules seem to interfere not only with the biology of myeloma bone destruction but also with tumour growth and survival, creating novel targets for the development of new antimyeloma treatment. Currently, bisphosphonates play a major role in the management of myeloma bone disease. Clodronate, pamidronate and zoledronic acid are the most effective bisphosphonates in symptomatic myeloma patients. Biochemical markers of bone remodeling have been used in an attempt to identify patients more likely to benefit from early treatment with bisphosphonates. Furthermore, using microarray techniques, myeloma patients may be subdivided into molecular subgroups with certain clinical characteristics, such as propensity for lytic lesions that may need early prophylactic treatment. Recent phase I studies with recombinant OPG and monoclonal antibodies to RANKL appear promising.

Cytogenetic manifestations of multiple myeloma heterogeneity

To investigate the genetic basis of the great heterogeneity observed in the clinical behavior of multiple myeloma (MM), a combined approach of G-banding, interphase fluorescence in situ hybridization (FISH), and multicolor FISH (M-FISH) was employed to analyze 70 samples from 53 patients with MM. G-banding revealed abnormal karyotypes in 77% of the cases. The origin of 31 chromosome markers was identified or revised by M-FISH. Combined metaphase karyotypic data and interphase FISH findings, using the immunoglobulin heavy-chain (IGH), IGH/cyclin D1 gene (CCND1), and D13S319 probes, revealed chromosome abnormalities in all evaluated patients and marked inter- and intratumor cytogenetic heterogeneity in the investigated MM samples. Cytogenetically unrelated clones were detected in 26% of the cases, mostly MM evaluated at diagnosis, whereas cytogenetic clonal evolution, manifested as related clones in 20% of the cases, was associated with disease progression. Among the 14q32 rearrangements, present in 66% of the cases, at least three cytogenetic subsets could be identified: one with t(11;14), usually without 13q14 deletion; another with other IGH changes, often 13q14 deletion, and hypodiploid modal chromosome number; and a third without changes in 14q32 but with abnormalities of chromosome 17. The correlation found between cytogenetic and clinicopathologic characteristics provided support for the concept that general genomic features in conjunction with specific chromosome rearrangements define the malignant phenotype in the various subsets of MM.

Advances in myeloma genetics and prospects for pharmacogenomic testing in multiple myeloma

Pharmacogenomic studies in multiple myeloma, a neoplasia of clonally expanded malignant bone marrow plasma cells, are helping to set the stage for individualized therapy. Although relatively few in numbers, these studies are already providing new therapeutic targets and avenues for drug discoveries as well as contributing to novel prognostic markers in multiple myeloma. High-throughput mutation screening of the kinome promises to identify further novel targets for therapy. Genetics and gene expression profiling technology have improved molecular-based patient stratification and prognostic staging, expanded knowledge of the molecular mechanism of chemotherapeutic agents, and provided a better understanding of myeloma bone disease. The use of pharmacogenomic strategies in myeloma is thus already changing medical practice.

A global expression-based analysis of the consequences of the t(4;14) translocation in myeloma

PURPOSE

Our purpose in this report was to define genes and pathways dysregulated as a consequence of the t(4;14) in myeloma, and to gain insight into the downstream functional effects that may explain the different prognosis of this subgroup.

EXPERIMENTAL DESIGN

Fibroblast growth factor receptor 3 (FGFR3) overexpression, the presence of immunoglobulin heavy chain-multiple myeloma SET domain (IgH-MMSET) fusion products and the identification of t(4;14) breakpoints were determined in a series of myeloma cases. Differentially expressed genes were identified between cases with (n = 5) and without (n = 24) a t(4;14) by using global gene expression analysis.

RESULTS

Cases with a t(4;14) have a distinct expression pattern compared with other cases of myeloma. A total of 127 genes were identified as being differentially expressed including MMSET and cyclin D2, which have been previously reported as being associated with this translocation. Other important functional classes of genes include cell signaling, apoptosis and related genes, oncogenes, chromatin structure, and DNA repair genes. Interestingly, 25% of myeloma cases lacking evidence of this translocation had up-regulation of the MMSET transcript to the same level as cases with a translocation.

CONCLUSIONS

t(4;14) cases form a distinct subgroup of myeloma cases with a unique gene signature that may account for their poor prognosis. A number of non-t(4;14) cases also express MMSET consistent with this gene playing a role in myeloma pathogenesis.

Mast cell-derived angiopoietin-1 plays a critical role in the growth of plasma cell tumors

Multiple myeloma in humans is frequently associated with mast cell infiltration and neovascularization, which correlate directly with disease severity, but the mechanisms underlying this relationship remain unclear. Here, we report that primary murine mast cells express angiopoietin-1 (Ang-1) and low levels of VEGF-A but not Ang-2 and that 2 established murine plasmacytoma cell lines express high levels of VEGF-A but little or no Ang-1 or Ang-2. An in vivo angiogenesis assay using extracellular matrix components shows that mast cells and plasmacytoma cells, together, promote marked neovascularization composed of dilated vessels, which is prevented by neutralization of VEGF-A and Ang-1 but is only partially reduced by neutralization of either VEGF-A or Ang-1. Mast cells within extracellular matrix components express Ang-1, and recombinant Ang-1 together with plasmacytoma cells promotes extracellular matrix neovascularization similar to that induced by mast cells. A transplantation assay shows that primary mast cells accelerate tumor growth by established plasmacytoma cell lines and that neutralization of Ang-1 alone or with VEGF-A reduces significantly the growth of plasmacytomas containing mast cells. These results demonstrate that mast cell-derived Ang-1 promotes the growth of plasmacytomas by stimulating neovascularization and provide further evidence supporting a causal relationship between inflammation and tumor growth.

New insight in the mechanism of osteoclast activation and formation in multiple myeloma: focus on the receptor activator of NF-kappaB ligand (RANKL)

The increase of osteoclast activation and formation is mainly involved in the development of the osteolytic bone lesions that characterize multiple myeloma (MM) patients. The mechanisms by which myeloma cells induce bone resorption have not been clear for many years. Recently, new evidence has elucidated which factors are critically involved in the activation of osteoclastic cells in MM. The potential role of the critical osteoclastogenic factor, the receptor activator of NF-kappaB ligand (RANKL), and its soluble antagonist osteoprotegerin (OPG) in the activation of bone resorption in MM is summarized in this review. It has been demonstrated that human MM cells induce an imbalance in the bone marrow environment of the RANKL/OPG ratio in favor of RANKL that triggers the osteoclast formation and activation leading to bone destruction. The direct production of the chemokine macrophage inflammatory protein-1 alpha (MIP-1alpha) by myeloma cells, in combination with the RANKL induction in BM stromal cells in response to myeloma cells, are critical in osteoclast activation and osteoclastogenesis.

Selenium Deficiency Abrogates Inflammation-Dependent Plasma Cell Tumors in Mice

The role of the micronutrient, selenium, in human cancers associated with chronic inflammations and persistent infections is poorly understood. Peritoneal plasmacytomas (PCTs) in strain BALB/c (C), the premier experimental model of inflammation-dependent plasma cell transformation in mice, may afford an opportunity to gain additional insights into the significance of selenium in neoplastic development. Here, we report that selenium-depleted C mice (n = 32) maintained on a torula-based low-selenium diet (5-8 micro g of selenium/kg) were totally refractory to pristane induction of PCT. In contrast, 11 of 26 (42.3%) control mice maintained on a selenium adequate torula diet (300 micro g of selenium/kg) and 15 of 40 (37.5%) control mice fed standard Purina chow (440 micro g of selenium/kg) developed PCT by 275 days postpristane. Abrogation of PCT was caused in part by the striking inhibition of the formation of the inflammatory tissue in which PCT develop (pristane granuloma). This was associated with the reduced responsiveness of selenium-deficient inflammatory cells (monocytes and neutrophils) to chemoattractants, such as thioredoxin and chemokines. Selenium-deficient C mice exhibited little evidence of disturbed redox homeostasis and increased mutant frequency of a transgenic lacZ reporter gene in vivo. These findings implicate selenium, via the selenoproteins, in the promotion of inflammation-induced PCT and suggest that small drug inhibitors of selenoproteins might be useful for preventing human cancers linked with chronic inflammations and persistent infections.