To provide an update on recent advances in the management of patients with multiple myeloma who are not eligible for autologous stem-cell transplantation.
A comprehensive review of the literature on diagnostic criteria is provided, and treatment options and management of adverse events are summarized.
Patients with symptomatic disease and organ damage (ie, hypercalcemia, renal failure, anemia, or bone lesions) require immediate treatment. The International Staging System and chromosomal abnormalities identify high- and standard-risk patients. Proteasome inhibitors, immunomodulatory drugs, corticosteroids, and alkylating agents are the most active agents. The presence of concomitant diseases, frailty, or disability should be assessed and, if present, treated with reduced-dose approaches. Bone disease, renal damage, hematologic toxicities, infections, thromboembolism, and peripheral neuropathy are the most frequent disabling events requiring prompt and active supportive care.
These recommendations will help clinicians ensure the most appropriate care for patients with myeloma in everyday clinical practice.
Here we report that targeting casein kinase 1 (CSNK1α1) is a potential novel treatment strategy in multiple myeloma (MM) therapy distinct from proteasome inhibition. CSNK1α1 is expressed in all the tested MM cell lines and patient MM cells, and is not altered during bortezomib-triggered cytotoxicity. Inhibition of CSNK1α1 kinase activity in MM cells with targeted therapy D4476 or shRNAs triggers cell G0/G1 phase arrest, prolonged G2/M phase, and apoptosis. D4476 also induced cytotoxicity in bortezomib-resistant MM cells and enhances bortezomib-triggered cytotoxicity. CSNK1α1 signaling pathways include CDKN1B, P53 and FADD; gene signatures involved included interferon alpha (IFNα), tumor necrosis factor alpha (TNFα), and LIN9. Additionally, reduction of Csnk1α1 prevents cMYC/KRAS12V transformation of BaF3 cells independent of IL3. Impartially, reducing Csnk1α1 prevented development of cMYC/KRAS12V-induced plasmacytomas (PCTs) in mice, suggesting that CSNK1α1 may be involved in MM initiation and progression. Our data suggest that targeting CSNK1α1, alone or combined with bortezomib, is a potential novel therapeutic strategy in MM. Moreover, inhibition of CSNK1α1 may prevent the progression of monoclonal gammopathy of undetermined significance (MGUS) to MM.
Multiple Myeloma (MM); CSNK1α1; D4476; Bortezomib; cMYC/KRAS12V; plasmacytomas (PCTs)
Our prior study in multiple myeloma (MM) patients showed increased numbers of plasmacytoid dendritic cells (pDCs) in the bone marrow (BM) which both contribute to immune dysfunction as well as promote tumor cell growth, survival, and drug resistance. Here we show that a novel Toll-Like Receptor (TLR-9) agonist C792 restores the ability of MM patient-pDCs to stimulate T cell proliferation. Co-culture of pDCs with MM cells induces MM cell growth; and importantly, C792 inhibits pDC-induced MM cell growth and triggers apoptosis. In contrast, treatment of either MM cells or pDCs alone with C792 does not affect the viability of either cell type. In agreement with our in vitro data, C792 inhibits pDC-induced MM cell growth in vivo in a murine xenograft model of human MM. Mechanistic studies show that C792 triggers maturation of pDCs, enhances interferon-α and interferon-λ secretion, and activates TLR-9/MyD88 signaling axis. Finally, C792 enhances the anti-MM activity of bortezomib, lenalidomide, pomalidomide, SAHA, or melphalan. Collectively, our preclinical studies provide the basis for clinical trials of C792, either alone or in combination, to both improve immune function and overcome drug resistance in MM.
Myeloma; Immunotherapy; Dendritic cells; pDC; TLR-9; CpG-ODN-C792; Interferons
The development of bortezomib and IMIDs resulted in a revolution in the treatment of MM. Moreover, second-generation proteasome inhibitors (carfilzomib) and IMIDs (pomalidomide) have recently been approved. Nevertheless, the incurability of this disease requires other drugs with different mechanisms of action to either prolong the survival of patients refractory to current therapies, or achieve cure. Active research has been done exploring the pathogenesis of MM and searching for novel druggable targets. In this regard, some of these novel agents seem promising, such as monoclonal antibodies (anti-CD38 - daratumumab or anti-CS1 - elotuzumab) or the kinesin protein inhibitor Arry-520. Other agents under investigation are kinase inhibitors, signaling pathways inhibitors or deacetylase inhibitors. With so many novel agents under investigation, future therapy in MM will probably involve the combined use of the already approved drugs with some of those newly discovered.
Multiple Myeloma; Proteasome Inhibitors; IMIDs; Targeted Agents; Monoclonal Antibodies; Deacetylase Inhibitors; Targeted drugs
Multiple Myeloma (MM) is a common hematologic malignancy of plasma cells representing an excellent model of epigenomics dysregulation in human disease. Importantly, these findings, in addition to provide a better understanding of the underlying molecular changes leading to this malignance, furnish the basis for an innovative therapeutic approach. Histone deacetylase inhibitors (HDACIs), including Vorinostat and Panobinostat, represent a novel class of drugs targeting enzymes involved in epigenetic regulation of gene expression, which have been evaluated also for the treatment of multiple myeloma. Although the clinical role in this setting is evolving and their precise utility remains to be determined, to date that single-agent anti-MM activity is modest. More importantly, HDACIs appear to be synergistic both in vitro and in vivo when combined with other anti-MM agents, mainly proteasome inhibitors including bortezomib. The molecular basis underlying this synergism seems to be multifactorial and involves interference with protein degradation as well as the interaction of myeloma cells with microenvironment. Here we review molecular events underling antitumor effects of HDACIs and the most recent results of clinical trials in relapsed and refractory MM.
Multiple myeloma; HDACIs; apoptosis; proteasome inhibitor; novel therapy
Histone deacetylases (HDACs) represent novel molecular targets for the treatment of various types of cancers, including multiple myeloma (MM). Many HDAC inhibitors have already shown remarkable anti-tumor activities in the preclinical setting; however, their clinical utility is limited due to unfavorable toxicities associated with their broad range HDAC inhibitory effects. Isoform-selective HDAC inhibition may allow for MM cytotoxicity without attendant side effects. In this study, we demonstrated that HDAC3 knockdown and a small molecule HDAC3 inhibitor BG45 trigger significant MM cell growth inhibition via apoptosis, evidenced by caspase and PARP cleavage. Importantly, HDAC3 inhibition downregulates phosphorylation (tyrosine 705 and serine 727) of STAT3. Neither IL-6 nor bone marrow stromal cells overcome this inhibitory effect of HDAC3 inhibition on p-STAT3 and MM cell growth. Moreover, HDAC3 inhibition also triggers hyperacetylation of STAT3, suggesting crosstalk signaling between phosphorylation and acetylation of STAT3. Importantly, inhibition of HDAC3, but not HDAC1 or HDAC2, significantly enhances bortezomib-induced cytotoxicity. Finally, we confirm that BG45 alone and in combination with bortezomib trigger significant tumor growth inhibition in vivo in a murine xenograft model of human MM. Our results indicate that HDAC3 represents a promising therapeutic target, and validate a prototype novel HDAC3 inhibitor BG45 in MM.
multiple myeloma; histone deacetylase 3; STAT3; bortezomib
Several components of the Wnt signaling cascade have been shown to function either as tumor suppressor proteins or as oncogenes in multiple human cancers, underscoring the relevance of this pathway in oncogenesis and the need for further investigation of Wnt signaling components as potential targets for cancer therapy. Here, using expression profiling analysis as well as in vitro and in vivo functional studies, we show that the Wnt pathway component BCL9 is a novel oncogene that is aberrantly expressed in human multiple myeloma as well as colon carcinoma. We show that BCL9 enhances β-catenin–mediated transcriptional activity regardless of the mutational status of the Wnt signaling components and increases cell proliferation, migration, invasion, and the metastatic potential of tumor cells by promoting loss of epithelial and gain of mesenchymal-like phenotype. Most importantly, BCL9 knockdown significantly increased the survival of xenograft mouse models of cancer by reducing tumor load, metastasis, and host angiogenesis through down-regulation of c-Myc, cyclin D1, CD44, and vascular endothelial growth factor expression by tumor cells. Together, these findings suggest that deregulation of BCL9 is an important contributing factor to tumor progression. The pleiotropic roles of BCL9 reported in this study underscore its value as a drug target for therapeutic intervention in several malignancies associated with aberrant Wnt signaling.
The transcription factor Sp1 controls number of cellular processes by regulating the expression of critical cell cycle, differentiation and apoptosis-related genes containing proximal GC/GT-rich promoter elements. We here provide both experimental and clinical evidence that Sp1 plays an important regulatory role in MM cell growth and survival.
We have investigated the functional Sp1 activity in MM cells using a plasmid with renilla luciferase reporter gene driven by Sp1-responsive promoter. We have also used both SiRNA and ShRNA-mediated Sp1 knock-down to investigate the growth and survival effects of Sp1 on MM cells, and further investigated the anti-MM activity of Terameprocol (TMP), a small molecule which specifically competes with Sp1-DNA binding in vitro and in vivo.
We have confirmed high Sp1 activity in MM cells which is further induced by adhesion to bone marrow stromal cells (BMSC). Sp1 knock down decreases MM cell proliferation and induces apoptosis. Sp1-DNA binding inhibition by TMP inhibits MM cell growth both in vitro and in vivo, inducing caspase 9-dependent apoptosis and overcoming the protective effects of BMSCs.
Our results demonstrate Sp1 as an important transcription factor in myeloma that can be therapeutically targeted for clinical application by TMP.
The alkylating agent melphalan prolongs survival in multiple myeloma (MM) patients; however, it is associated with toxicities and development of drug-resistance. Here, we evaluated the efficacy of melphalan-flufenamide (Mel-flufen), a novel dipeptide prodrug of melphalan in MM.
MM cell lines, primary patient cells, and the human MM xenograft animal model were utilized to study the antitumor activity of mel-flufen.
Low doses of mel-flufen triggers a more rapid and higher intracellular concentrations of melphalan in MM cells than is achievable by free melphalan. Cytotoxicity analysis showed significantly lower IC50 of mel-flufen than melphalan in MM cells. Importantly, mel-flufen induces apoptosis even in melphalan-, and bortezomib-resistant MM cells. Mechanistic studies show that siRNA knockdown of aminopeptidase N, a key enzyme mediating intracellular conversion of mel-flufen to melphalan, attenuates anti-MM activity of mel-flufen. Furthermore, mel-flufen-induced apoptosis was associated with: 1) activation of caspases and PARP cleavage; 2) ROS generation; 3) mitochondrial dysfunction and release of cytochrome-c; and 4) induction of DNA damage. Moreover, mel-flufen inhibits MM cell migration and tumor-associated angiogenesis. Human MM xenograft studies showed a more potent inhibition of tumor growth in mice treated with mel-flufen than mice receiving equimolar doses of melphalan. Finally, combining mel-flufen with lenalidomide, bortezomib, or dexamethasone triggers synergistic anti-MM activity.
Our preclinical study supports clinical evaluation of mel-flufen to enhance therapeutic potential of melphalan, overcome drug-resistance, and improve MM patient outcome.
Myeloma; Apoptosis; Novel therapeutics; alkylating agents
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 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, pro-apoptotic network centered on nuclear relocalization of ABL1 kinase. Although nuclear ABL1 triggers cell death through its interaction with the Hippo pathway co–activator 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. Importantly, genetic inactivation of STK4 restores YAP1 levels, triggering cell death in vitro and in vivo. Our data therefore identify a novel synthetic–lethal strategy to selectively target cancer cells presenting with endogenous DNA damage and low YAP1 levels.
Hippo pathway; YAP1; leukemia; lymphoma; multiple myeloma; ABL1; STK4; synthetic lethality
Multiple myeloma (MM) is a clonal B-cell malignancy characterized by the proliferation of plasma cells in the bone marrow. Despite recent therapeutic advances, MM remains an incurable disease. Therefore, research has focused on defining new aspects in MM biology that can be therapeutically targeted. Compelling evidence suggests that malignant cells have a higher nicotinamide adenine dinucleotide (NAD+) turnover rate than normal cells, suggesting that this biosynthetic pathway represents an attractive target for cancer treatment. We recently reported that an intracellular NAD+-depleting agent, FK866, exerts its anti-MM effect by triggering autophagic cell death via transcriptional-dependent (transcription factor EB, TFEB) and -independent (PI3K-MTORC1) mechanisms. Our findings link intracellular NAD+ levels to autophagy in MM cells, providing the rationale for novel targeted therapies in MM.
multiple myeloma; nicotinamide phosphoribosyltransferase; PI3K/MTORC1; TFEB; cancer treatment
Despite the recent development of effective therapeutic agents against multiple myeloma (MM), new therapeutic approaches, including immunotherapies, remain to be developed. Here we identified novel human leucocyte antigen (HLA)-A*0201 (HLAA2)-restricted cytotoxic T lymphocyte (CTL) epitopes from a B cell specific molecule HLA-DOβ (DOB) as a potential target for MM. By DNA microarray analysis, the HLADOB expression in MM cells was significantly higher than that in normal plasma cells. Twenty-five peptides were predicted to bind to HLA-A2 from the amino acid sequence of HLA-DOB. When screened for the immunogenicity in HLA-A2-transgenic mice immunized with HLA-DOB cDNA, 4 peptides were substantially immunogenic. By mass spectrometry analysis of peptides eluted from HLA-A2-immunoprecipitates of MM cell lines, only two epitopes, HLA-DOB232-240 (FLLGLIFLL) and HLA-DOB185-193 (VMLEMTPEL), were confirmed for their physical presence on cell surface. When healthy donor blood was repeatedly stimulated in vitro with these two peptides and assessed by antigen-specific γ-interferon secretion, HLA-DOB232-240 was more immunogenic than HLA-DOB185-193. Additionally, the HLA-DOB232-240-specific CTLs, but not the HLA-DOB185-193-specific CTLs, displayed an major histocompatibility complex class I-restricted reactivity against MM cell lines expressing both HLA-A2 and HLA-DOB. Taken together, based on the physical presence on tumour cell surface and high immunogenicity, HLA-DOB232-240 might be useful for developing a novel immunotherapy against MM.
multiple myeloma; HLA-DOβ; cytotoxic T lymphocyte; T cell epitope; DNA microarray
Bone destruction is a feature of multiple myeloma, characterised by osteolytic bone destruction due to increased osteoclast activity and suppressed or absent osteoblast activity. Almost all multiple myeloma patients develop osteolytic bone lesions associated with severe and debilitating bone pain, pathologic fractures, hypercalcemia, and spinal cord compression, as well as increased mortality. Biomarkers of bone remodelling are used to identify disease characteristics that can help select the optimal management of patients. However, more accurate biomarkers are needed to effectively mirror the dynamics of bone disease activity.
A label-free mass spectrometry-based strategy was employed for discovery phase analysis of fractionated patient serum samples associated with no or high bone disease. A number of proteins were identified which were statistically significantly correlated with bone disease, including enzymes, extracellular matrix glycoproteins, and components of the complement system.
Enzyme-linked immunosorbent assay of complement C4 and serum paraoxonase/arylesterase 1 indicated that these proteins were associated with high bone disease in a larger independent cohort of patient samples. These biomolecules may therefore be clinically useful in assessing the extent of bone disease.
Electronic supplementary material
The online version of this article (doi:10.1186/1471-2164-15-904) contains supplementary material, which is available to authorized users.
Biomarkers; Bone disease; C4; Mass spectrometry; PON1; Proteomics
Over-expression of the protein Dickkopf-1 (Dkk1) has been associated with multiple myeloma bone disease. Previous reports with the use of anti-Dkk1 neutralizing Ab directed strategies have demonstrated a pro-anabolic effect with associated anti-myeloma activity in 2 in vivo mouse models. However new insights on the role of the wnt pathway in osteoclasts (OC) are emerging and the potential effect of a neutralizing Ab to Dkk1 in osteoclastogenesis remains to be elucidated. In order to better define the effect of an anti-Dkk1 neutralizing Ab on osteoclastogenesis and myeloma, we studied a novel anti-Dkk1 monoclonal Ab in our preclinical models. In vivo data confirmed the pro-anabolic and anti-MM effect. In vitro data in part confirmed the in vivo observation, suggesting an indirect anti-MM effect secondary to inhibition of osteoclastogenesis and thus the interaction between MM and bone microenvironment. However, when studies on osteoclastogenesis were extended to samples derived from MM patients, we observed a variable response to anti-Dkk1 treatment without correlation to expression of surface receptors for Dkk1 in OCs suggesting potential heterogeneity in efficacy of such a strategy. In conclusion, Dkk1 is a promising target for the treatment of both MM and bone disease, and ongoing clinical studies will help elucidate its efficacy.
Dkk1; wnt; multiple myeloma; osteoclast; osteoblast
Aurora Kinases, whose expression is linked to genetic instability and cellular proliferation, are under investigation as novel therapeutic targets in multiple myeloma (MM). Here, we investigated the preclinical activity of a small molecule–multi-targeted kinase inhibitor, AT9283, with potent activity against Aurora kinase A (AURKA), Aurora kinase B (AURKB) and Janus Kinase 2/3.
We evaluated the in vitro anti myeloma activity of AT9283 alone and in combination with lenalidomide and the in vivo efficacy by using a Xenograft mouse model of human MM.
Our data demonstrated AT9283 induced cell growth inhibition and apoptosis in MM. Studying the apoptosis mechanism of AT9283 in MM, we observed features consistent with both AURKA and AURKB inhibition, e.g increase of cells with polyploid DNA content, decrease in phospho-Histone H3, and decrease of phospho-Aurora A. Importantly, AT9283 also inhibited STAT3 tyrosine phosphorylation in MM cells. Genetic depletion of STAT3, AURKA or AURKB showed growth inhibition of MM cells, suggesting a role of AT9283-induced inhibition of these molecules in the underlying mechanism of MM cell death. In vivo studies demonstrated decreased MM cell growth and prolonged survival in AT9283-treated mice compared to controls. Importantly, combination studies of AT9283 with lenalidomide showed significant synergistic cytotoxicity in MM cells, even in the presence of bone marrow stromal cells (BMSCs). Enhanced cytotoxicity was associated with increased inhibition of pSTAT3 and pERK.
Demonstration of in vitro and in vivo anti-MM activity of AT9283 provides the rationale for the clinical evaluation of AT9283 as monotherapy and in combination in patients with MM.
Aurora Kinases; STAT3; multiple myeloma; lenalidomide
Recent studies have provided direct evidence for genetic variegation in subclones for various cancer types. However little is known about subclonal evolutionary processes according to treatment and subsequent relapse in multiple myeloma (MM). This issue was addressed in a cohort of 24 MM patients treated either with conventional chemotherapy or with the proteasome inhibitor, bortezomib. Because MM is a highly heterogeneous disease associated to a large number of chromosomal abnormalities, a subset of secondary genetic events that seem to reflect progression: 1q21 gain, NF-κB activating mutations, RB1 and TP53 deletions was examined. By using high resolution SNP arrays, subclones were identified with nonlinear complex evolutionary histories. Such reordering of the spectrum of genetic lesions, identified in a third of MM patients during therapy, is likely to reflect the selection of genetically distinct subclones, not initially competitive against the dominant population, but which survived chemotherapy, thrived and acquired new anomalies. In addition, the emergence of minor subclones at relapse appeared to be significantly associated with bortezomib treatment. These data support the idea that new strategies for future clinical trials in MM should combine targeted therapy and subpopulations’ control to eradicate all myeloma subclones in order to obtain long-term remission.
multiple myeloma; genomic analysis; nonlinear evolution
Deregulated expression of microRNAs (miRNAs) plays a role in the pathogenesis and progression of multiple myeloma (MM). Among upregulated miRNAs, miR-21 has oncogenic potential and therefore represents an attractive target for the treatment of MM.
Here, we investigated the in vitro and in vivo anti-MM activity of miR-21 inhibitors.
Either transient enforced expression or lentivirus-based constitutive expression of miR-21 inhibitors triggered significant growth inhibition of primary patient MM cells or IL-6-dependent/independent MM cell lines and overcame the protective activity of human bone marrow stromal cells. Conversely, transfection of miR-21 mimics significantly increased proliferation of MM cells, demonstrating its tumor promoting potential in MM. Importantly, upregulation of miR-21 canonical validated targets (PTEN, Rho-B and BTG2), together with functional impairment of both AKT and ERK signaling, were achieved by transfection of miR-21 inhibitors into MM cells. In vivo delivery of miR-21 inhibitors in SCID mice bearing human MM xenografts expressing miR-21 induced significant anti-tumor activity. Upregulation of PTEN and downregulation of p-AKT were observed in retrieved xenografts following treatment with miR-21 inhibitors.
Our findings show the first evidence that in vivo antagonism of miR-21 exerts anti-MM activity, providing the rationale for clinical development of miR-21 inhibitors in this still incurable disease.
multiple myeloma; plasma cell leukemia; miR-21; miR-21 inhibitor; microRNA
Upregulation of cytokines and chemokines is a frequent finding in multiple myeloma (MM). CCL3 (also known as MIP-1α) is a pro-inflammatory chemokine whose levels in the MM microenvironment correlate with osteolytic lesions and tumor burden. CCL3 and its receptors, CCR1 and CCR5, contribute to the development of bone disease in MM by supporting tumor growth and regulating osteoclast (OC) differentiation. Here, we identify inhibition of osteoblast (OB) function as an additional pathogenic mechanism in CCL3-induced bone disease. MM-derived and exogenous CCL3 represses mineralization and osteocalcin production by primary human bone marrow stromal cells and HS27A cells. Our results suggest that CCL3 effects on OBs are mediated by ERK activation and subsequent downregulation of the osteogenic transcription factor osterix. CCR1 inhibition reduced ERK phosphorylation and restored both osterix and osteocalcin expression in the presence of CCL3. Finally, treating SCID-hu mice with a small molecule CCR1 inhibitor suggests an upregulation of osteocalcin expression along with OC downregulation. Our results show that CCL3, in addition to its known catabolic activity, reduces bone formation by inhibiting OB function and therefore contributes to OB/OC uncoupling in MM.
Myeloma; CCL3; Osteoblast; Osteocalcin; ERK; Osterix
In this prospective study of patients with relapsed and/or refractory multiple myeloma (MM) treated with lenalidomide and dexamethasone, relationships between markers of endothelial stress and drug administration and incidence of venous thromboembolism (VTE) were assessed. Of 33 enrolled patients, laboratory and treatment data were available for 32 patients. Of these, 23 received pulsed dexamethasone (40 mg/day on days 1–4, 9–12, and 17–21 of each 28-day cycle) and 9 received weekly dexamethasone (40 mg/day on days 1, 8, 15, and 21 of each cycle). The overall incidence of VTE was 9%. A decreasing trend in markers values was observed with intercellular adhesion molecule (P = 0·05), fibrinogen (P = 0·008), plasminogen activator inhibitor-1 (P < 0·001), homocysteine (P = 0·002), and P-selectin (P < 0·001) during therapy. Compared with weekly dexamethasone, pulsed dexamethasone was associated with significantly greater variation in mean adjusted relative values of fibrinogen, P-selectin, and vascular endothelial growth factor (P < 0·001 for all comparisons), although there was no apparent association with VTE incidence. Lenalidomide plus dexamethasone affects endothelial stress marker levels in patients with advanced MM. The higher variation seen with pulsed dexamethasone suggests greater endothelial stress with this approach.
multiple myeloma; venous thromboembolism; dexamethasone; lenalidomide; endothelial markers
Plasma cell leukemia (PCL) is a rare and aggressive variant of myeloma characterized by the presence of circulating plasma cells. It is classified as either primary PCL occurring at diagnosis or as secondary PCL in patients with relapsed/refractory myeloma. Primary PCL is a distinct clinic-pathologic entity with different cytogenetic and molecular findings. The clinical course is aggressive with short remissions and survival duration. The diagnosis is based upon the percentage (≥ 20%) and absolute number (≥ 2 × 10 9/L) of plasma cells in the peripheral blood. It is proposed that the thresholds for diagnosis be reexamined and consensus recommendations are made for diagnosis, as well as, response and progression criteria. Induction therapy needs to begin promptly and have high clinical activity leading to rapid disease control in an effort to minimize the risk of early death. Intensive chemotherapy regimens and bortezomib-based regimens are recommended followed by high-dose therapy with autologous stem-cell transplantation (HDT/ASCT) if feasible. Allogeneic transplantation can be considered in younger patients. Prospective multicenter studies are required to provide revised definitions and better understanding of the pathogenesis of PCL.
plasma cell leukemia; cytogenetics; bortezomib; transplantation; myeloma; prognosis
Multiple myeloma (MM) is the second most common hematologic malignancy affecting terminally differentiated plasma cells. Although high-dose chemotherapy and autologous stem cell transplantation improved survival in younger patients, the natural history of MM has been changed with the availability of five new agents approved in last 10 years (thalidomide, bortezomib, lenalidomide, liposomal doxorubicin and carfilzomib). Despite this significant improvement in overall outcome, MM remains incurable in majority of patients prompting continued search for additional therapeutic options. Extensive molecular and genomic characterization of MM cells in its bone marrow milieu, which affects myeloma cell growth and survival, has provided number of novel drugable targets and pathways. Perturbation of protein catabolism at multiple levels has become an important target in MM. Similarly with improvements in monoclonal antibody generation and vaccine development along with identification of number of cell surface and cellular targets have led to development of various strategies including antibodies and antibody-drug conjugates which are under investigation both preclinically as well as in early clinical studies. We propose that eventually, molecularly-informed multi-agent combination therapies will be required to eliminate the MM cell clone for a long-term disease control.
Lenalidomide is an effective therapeutic agent for multiple myeloma that exhibits immunomodulatory properties including the activation of T and NK cells. The use of lenalidomide to reverse tumor-mediated immune suppression and amplify myeloma-specific immunity is currently being explored. In the present study, we examined the effect of lenalidomide on T-cell activation and its ability to amplify responses to a dendritic cell-based myeloma vaccine. We demonstrate that exposure to lenalidomide in the context of T-cell expansion with direct ligation of CD3/ CD28 complex results in polarization toward a Th1 phenotype characterized by increased IFN-γ, but not IL-10 expression. In vitro exposure to lenalidomide resulted in decreased levels of regulatory T cells and a decrease in T-cell expression of the inhibitory marker, PD-1. Lenalidomide also enhanced T-cell proliferative responses to allogeneic DCs. Most significantly, lenalidomide treatment potentiated responses to the dendritic cell/myeloma fusion vaccine, which were characterized by increased production of inflammatory cytokines and increased cytotoxic lymphocyte-mediated lysis of autologous myeloma targets. These findings indicate that lenalidomide enhances the immunologic milieu in patients with myeloma by promoting T-cell proliferation and suppressing inhibitory factors, and thereby augmenting responses to a myeloma-specific tumor vaccine.
Lenalidomide; Multiple myeloma; Dendritic cell vaccine; PD-1
Multiple myeloma (MM) is an incurable neoplasm caused by proliferation of malignant plasma cells in the bone marrow (BM). MM is characterized frequently by a complete or partial deletion of chromosome 13q14, seen in more than 50% of patients at diagnosis. Within this deleted region the tripartite motif containing 13 (TRIM13, also termed RFP2) gene product has been proposed to be a tumour suppressor gene (TSG). Here, we show that low expression levels of TRIM13 in MM are associated with chromosome 13q deletion and poor clinical outcome. We present a functional analysis of TRIM13 using a loss-of-function approach, and demonstrate that TRIM13 downregulation decreases tumour cell survival as well as cell cycle progression and proliferation of MM cells. In addition, we provide evidence for the involvement of TRIM13 downregulation in inhibiting the NF kappa B pathway and the activity of the 20S proteasome. Although this data does not support a role of TRIM13 as a TSG, it substantiates important roles of TRIM13 in MM tumour survival and proliferation, underscoring its potential role as a novel target for therapeutic intervention.
TRIM13 (RFP2); 13q; Myeloma; Proliferation; Proteasome
Cell cycle regulators, such as cyclin-dependent kinases (CDKs), are appealing targets for multiple myeloma (MM) therapy given the increased proliferative rates of tumor cells in advanced vs. early stages of MM. We hypothesized that a multi-targeted CDK inhibitor with a different spectrum of activity compared to existing CDK inhibitors could trigger distinct molecular sequelae with therapeutic implications for MM. We therefore studied the small molecule heterocyclic compound NVP-LCQ195/AT9311 (LCQ195), which inhibits CDK1, CDK2 and CDK5, as well as CDK3 and CDK9. LCQ195 induced cell cycle arrest and eventual apoptotic cell death of MM cells, even at sub-μM concentrations; spared non-malignant cells; and overcome the protection conferred to MM cells by stroma or cytokines of the bone marrow milieu. In MM cells, LCQ195 triggered decreased amplitude of transcriptional signatures associated with oncogenesis, drug resistance, and stem cell renewal, including signatures of activation of key transcription factors for MM cells e.g. myc, HIF-1α, IRF4. Bortezomib-treated MM patients whose tumors had high baseline expression of genes suppressed by LCQ195 had significantly shorter progression-free and overall survival than those with low levels of these transcripts in their MM cells. These observations provide insight into the biological relevance of multi-targeted CDK inhibition in MM.
myeloma; cancer; CDK; microenvironment; kinase inhibitor; cyclins
Small molecule multi-targeted CDK inhibitors (CDKIs) are of particular interest due to their potent antitumor activity independent of p53 gene alterations. P53 deletion is associated with a very poor prognosis in multiple myeloma (MM). In this regard, we tested the anti-MM activity of RGB-286638, an indenopyrazole-derived CDKI with Ki-nanomolar activity against transcriptional CDKs. We examined RGB-286638’s mode-of-action in MM cell lines with wild type (wt)-p53 and those expressing mutant p53. RGB-286638 treatment resulted in MM cytotoxicity in vitro associated with inhibition of MM tumor growth and prolonged survival in vivo. RGB-286638 displayed caspase-dependent apoptosis in both wt-p53 and mutant-p53 cells that was closely associated with the downregulation of RNA polymerase II phosphorylation and inhibition of transcription. RGB-286638-triggered p53 accumulation via nucleolar stress and loss of Mdm2, accompanied by induction of p53 DNA binding activity. Additionally, RGB-286638 mediated p53-independent activity, which was confirmed by cytotoxicity in p53-knockdown and p53-mutant cells. We also demonstrated downregulation of oncogenic miR-19, miR-92a-1, and miR-21. Our data provide the rationale for the development of transcriptional CDK inhibitors as therapeutic agents, which activate p53 in competent cells, while circumventing p53 deficiency through alternative p53-independent cell death mechanisms in p53-mutant/deleted cells.
myeloma; p53; transcription; CDKs; apoptosis