The t(4;14) translocation in multiple myeloma (MM) simultaneously dysregulates two apparent oncogenes: fibroblast growth factor receptor 3 (FGFR3) controlled by the 3′ immunoglobulin heavy chain enhancer on der(14) and MMSET controlled by the intronic Eμ enhancer on der(4). Although all MM tumors and cell lines with a t(4;14) translocation have dysregulated MMSET, about 25% do not express FGFR3. Therefore, the function of dysregulated wild-type (WT) FGFR3 in the pathogenesis of MM remains unclear. We developed a murine transgenic (TG) model in which WT FGFR3 is over-expressed in B lymphoid cells. Although high levels of FGFR3 resulted in lymphoid hyperplasia in about one-third of older mice, no increase in tumorigenesis was observed. However, double TG FGFR3/Myc mice develop mature B lymphoma tumors that occur with a higher penetrance and shorter latency than in single TG Myc mice (P = 0.006). We conclude that expression of high levels of WT FGFR3 can be oncogenic and cooperate with MYC to generate B lymphoid tumors. This suggests that dysregulated FGFR3 expression is likely to be essential at least for the early stages of pathogenesis of MM tumors that have a t(4;14) translocation.
FGFR3; Myc; lymphoma; multiple myeloma; oncogene
Multiple myeloma (MM) is malignancy of isotype-switched, BM-localized plasma cells that frequently results in bone destruction, BM failure, and death. Important molecular subgroups are identified by three classes of recurrent immunoglobulin gene translocations and hyperdiploidy, both of which affect disease course. From a clinical standpoint, it is critical to identify MM patients carrying the t(4;14) translocation, which is present in 15% of myelomas and is associated with dysregulation of WHSC1/MMSET and often FGFR3. These patients should all receive bortezomib as part of their initial induction treatment because this has been shown to significantly prolong survival. In contrast, patients with translocations affecting the MAF family of transcription factors, del17p, or gene-expression profiling (GEP)–defined high-risk disease appear to have a worse prognosis that is not dramatically improved by any intervention. These patients should be enrolled in innovative clinical trials. The remaining patients with cyclin D translocations or hyperdiploidy do well with most therapies, and the goal should be to control disease while minimizing toxicity.
Multiple myeloma is divided into two distinct genetic subtypes based on chromosome content. Hyperdiploid myeloma is characterized by multiple trisomies of chromosomes 3, 5, 7, 9 11, 15, 19 and 21, and lacks recurrent immunoglobulin gene translocations. Non-hyperdiploid myeloma in contrast is characterized by chromosome translocations t(4;14), t(14;16), t(14;20), t(6;14) and t(11;14). A unifying event in the pathogenesis of multiple myeloma is the dysregulated expression of a cyclin D gene, either directly by juxtaposition to an immunoglobulin enhancer, as a result of ectopic expression of a MAF family transcription factor, or indirectly by as yet unidentified mechanisms. Secondary genetic events include rearrangements of MYC, activating mutations of NRAS, KRAS or BRAF, a promiscuous array of mutations that activate NFkB and deletions of 17p. Among the poor-risk genetic features are t(4;14), t(14;16), t(14;20), del 17p and gains of 1q. Available evidence supports the use of a risk-stratified approach to the treatment of patients with multiple myeloma, with the early and prolonged use of bortezomib particularly in patients with t(4;14) and del 17p.
Pathogenesis; Multiple myeloma; Genetics; Prognosis; Treatment
FGFR3 is implicated in several human diseases. Following activation and endocytosis, FGFR3 undergoes sequential ectodomain and intramembrane cleavages to generate a soluble cytoplasmic fragment that can translocate to the nucleus.
Fibroblast growth factor receptor 3 (FGFR3) is a major negative regulator of bone growth that inhibits the proliferation and differentiation of growth plate chondrocytes. Activating mutations of its c isoform cause dwarfism in humans; somatic mutations can drive oncogenic transformation in multiple myeloma and bladder cancer. How these distinct activities arise is not clear. FGFR3 was previously shown to undergo proteolytic cleavage in the bovine rib growth plate, but this was not explored further. Here, we show that FGF1 induces regulated intramembrane proteolysis (RIP) of FGFR3. The ectodomain is proteolytically cleaved (S1) in response to ligand-induced receptor activation, but unlike most RIP target proteins, it requires endocytosis and does not involve a metalloproteinase. S1 cleavage generates a C-terminal domain fragment that initially remains anchored in the membrane, is phosphorylated, and is spatially distinct from the intact receptor. Ectodomain cleavage is followed by intramembrane cleavage (S2) to generate a soluble intracellular domain that is released into the cytosol and can translocate to the nucleus. We identify the S1 cleavage site and show that γ-secretase mediates the S2 cleavage event. In this way we demonstrate a mechanism for the nuclear localization of FGFR3 in response to ligand activation, which may occur in both development and disease.
We studied 351 patients with smoldering multiple myeloma (SMM) in whom the underlying primary molecular cytogenetic subtype could be determined based on cytoplasmic immunoglobulin fluorescent in situ hybridization studies. Hundred and fifty-four patients (43.9%) had trisomies, 127 (36.2%) had immunoglobulin heavy chain (IgH) translocations, 14 (4%) both trisomies and IgH translocations, 53 (15.1%) no abnormalities detected and 3 (0.9%) had monosomy13/del(13q) in the absence of any other abnormality. Among 127 patients with IgH translocations, 57 were t(11;14), 36 t(4;14), 11 musculoaponeurotic fibrosarcoma (MAF) translocations, and 23 other or unknown IgH translocation partner. Time to progression (TTP) to symptomatic multiple myeloma was significantly shorter in patients with the t(4;14) compared with patients with t(11;14), median 28 versus 55 months, respectively, P = 0.025. The median TTP was 28 months with t(4;14) (high-risk), 34 months with trisomies alone (intermediate-risk), 55 months with t(11;14), MAF translocations, other/unknown IgH translocations, monosomy13/del(13q) without other abnormalities, and those with both trisomies and IgH translocations (standard-risk), and not reached in patients with no detectable abnormalities (low-risk), P = 0.001. There was a trend to shorter TTP with deletion 17p (median TTP, 24 months). Overall survival from diagnosis of SMM was significantly inferior with t(4;14) compared with t(11;14), median 105 versus 147 months, respectively, P = 0.036.
smoldering multiple myeloma; cytogenetics; prognosis; biomarker
Multiple myeloma accounts for ~10% of all hematologic malignancies.
The diagnosis requires 10% or more clonal plasma cells on bone marrow examination or a biopsy proven plasmacytoma plus evidence of end-organ damage felt to be related to the underlying plasma-cell disorder.
Patients with 17p deletion, t(14;16), t(14;20), or high-risk gene expression profiling signature have high-risk myeloma. Patients with t(4;14) translocation, karyotypic deletion 13, or hypodiploidy are considered to have intermediate-risk disease. All others are considered to have standard-risk myeloma.
Standard-risk patients are treated with nonalkylator-based therapy such as lenalidomide plus low-dose dexamethasone (Rd) followed by autologous stem-cell transplantation (ASCT). An alternative strategy is to continue initial therapy after stem-cell collection, reserving ASCT for first relapse. Intermediate-risk and high-risk patients are treated with a bortezomib-based induction followed by ASCT and then bortezomib-based maintenance. Patients not eligible for ASCT can be treated with Rd for standard risk disease, or with a bortezomib-based regimen if intermediate-risk or high-risk features are present. To reduce toxicity, when using bortezomib, the once-weekly subcutaneous dose is preferred; similarly, when using dexamethasone, the low-dose approach (40 mg once a week) is preferred, unless there is a need for rapid disease control.
Management of refractory disease
Patients with indolent relapse can be treated first with two-drug or three-drug combinations. Patients with more aggressive relapse often require therapy with a combination of multiple active agents. The most promising new agents in development are pomalidomide and carfilizomib.
Dysregulation of oncogenes by translocation to the IgH locus (14q32) is a seminal event in the pathogenesis of B-cell tumours1. In multiple myeloma (MM), translocations to the IgH locus have been reported at an incidence of 20–60%. For most translocations, the partner chromosome is unknown (14q+); for the others, a diverse array of chromosomal partners have been identified, with 11q13 (cyclin D1) the only chromosome that is frequently involved2–6. Recently, we developed a Southern-blot assay that detects translocation breakpoint fragments in most MM tumours, including those with no translocation detected by conventional karyotyping6. In a continuing analysis of translocations in 21 myeloma cell lines and primary tumours, we show that the novel, karyotypically silent translocation t(4;14)(p16.3;q32.3) is present in five lines and at least three of ten primary tumours. The chromosome-4 breakpoints are clustered in a 70-kb region centromeric to the fibroblast growth factor receptor 3 gene (FGFR3), the apparent dysregulated oncogene. Two lines and one primary tumour with this translocation selectively express an FGFR3 allele containing activating mutations identified previously in thanatophoric dwarfism. We propose that after the t(4;14) translocation, somatic mutation during tumour progression frequently generates an FGFR3 protein that is active in the absence of ligand.
Activation of fibroblast growth factor receptors is a common oncogenic event. Little is known about the determinants of sensitivity to FGFR inhibition and how these may vary between different oncogenic FGFRs. Using parallel RNA interference genetic screens we demonstrate that EGFR limits sensitivity to FGFR inhibition in FGFR3 mutant and translocated cell lines, but not in other FGFR driven cell lines. We also identify two distinct mechanisms through which EGFR limits sensitivity. In partially FGFR3 dependent lines, inhibition of FGFR3 results in transient down-regulation of MAPK signalling that is rescued by rapid upregulation of EGFR signalling. In cell lines that are intrinsically resistant to FGFR inhibition, EGFR dominates signalling via repression of FGFR3, with EGFR inhibition rescued by delayed up-regulation of FGFR3 expression. Importantly, combinations of FGFR and EGFR inhibitors overcome these resistance mechanisms in vitro and in vivo. Our results illustrate the power of parallel RNA interference screens in identifying common resistance mechanisms to targeted therapies.
FGFR3; EGFR; siRNA screen; Bladder cancer
Multiple myeloma (MM) is a clinically and genetically heterogenous cancer where tumour cells have dysregulated expression of a D-type cyclin, often in association with a recurrent IgH translocation. Patients whose tumour cells express cyclin D2, with the translocation t(4;14) or t(14;16), generally have more proliferative disease and inferior outcomes. The phosphatidylinositol-3-kinase (PI3K) pathway is a major regulator of D-type cyclin expression and cell cycle entry. We evaluated the effect of PI3K pathway blockade on cell cycle behaviour in MM cells, investigating differences between cyclin D2- and cyclin D1-expressing tumours. MM cell lines and primary bone marrow CD138+ MM cells were exposed to the pan-PI3K/mTOR inhibitor, PI-103, and assessed for cell cycle profiles, [3H]-thymidine uptake and cell cycle proteins. We report, in both cell lines and primary MM cells, that PI-103 induced cell cycle arrest with downregulation of cyclin D2 and CDK4/6 in MM cells expressing cyclin D2 via t(4;14) or t(14;16) translocations. Cells expressing cyclin D1 via t(11;14) were insensitive to PI-103, despite exhibiting inhibition of downstream signalling targets. In primary MM cells, PI-103 enhanced the anti-proliferative effects of anti-MM agents. Treatment paradigms including blockade of the PI3K/mTOR pathway should be targeted at patients with IgH translocations associated with cyclin D2 overexpression.
multiple myeloma; cyclin D; cell cycle; PI3K/mTOR; PI-103
Ectopic activation of fibroblast growth factor receptor 3 (FGFR3) is associated with several cancers, including multiple myeloma (MM). FGFR3 inhibition in these cells inhibits proliferation and induces apoptosis, validating FGFR3 signaling as a therapeutic target in t(4;14) MM cases. We have identified the PI3K regulatory subunit, p85α, as a novel interactor of FGFR3 by yeast two-hybrid, and confirmed an interaction with both p85α and p85β in mammalian cells. The interaction of FGFR3 with p85 is dependent upon receptor activation. In contrast to the Gab1-mediated association of FGFRs with p85, the FGFR3-p85 interaction we observed requires FGFR3 Y760, previously identified as a PLCγ binding site. The interaction of p85 with FGFR3 does not require PLCγ, suggesting the p85 interaction is direct and independent of PLCγ binding. FGFR3 and p85 proteins also interact in MM cell lines which consistently express p85α and p85β, but not p50 or p55 subunits. siRNA knockdown of p85β in MM cells caused an increased ERK response to FGF2. These data suggest that an endogenous negative regulatory role for the p85-FGFR3 interaction on the Ras/ERK/MAPK pathway may exist in response to FGFR3 activity and identifies a novel therapeutic target for MM.
Multiple myeloma (MM) is a clonal plasma cell malignancy clinically characterized by osteolytic lesions, immunodeficiency, and renal disease. There are an estimated 750,000 people diagnosed with MM worldwide, with a median overall survival of 3 – 5 years. Besides chromosomal aberrations, translocations, and mutations in essential growth and tumor-suppressor genes, accumulating data strongly highlight the pathophysiologic role of the bone marrow (BM) microenvironment in MM pathogenesis. Based on this knowledge, several novel agents have been identified, and treatment options in MM have fundamentally changed during the last decade. Thalidomide, bortezomib, and lenalidomide have been incorporated into conventional cytotoxic and transplantation regimens, first in relapsed and refractory and now also in newly diagnosed MM. Despite these significant advances, there remains an urgent need for more efficacious and tolerable drugs. Indeed, a plethora of preclinical agents awaits translation from the bench to the bedside. This article reviews the scientific rationale of new therapy regimens and newly identified therapeutic agents – small molecules as well as therapeutic antibodies – that hold promise to further improve outcome in MM.
bone marrow microenvironment; combination therapy; multiple myeloma
Multiple myeloma (MM) is a plasma-cell (PC) malignancy that is heterogeneous in its clinical presentation and prognosis. Monoclonal gammopathy of undetermined significance (MGUS) consistently preceded development of MM. The presence of primary IgH translocations and the universal overexpression of cyclin D genes led to a molecular classification of MM patients into different disease subtypes. Since Bcl-2 family proteins determine cell fate, we analyzed a publicly available Affymetrix gene expression of 44 MGUS and 414 newly diagnosed MM patients to investigate (1) the global change of Bcl-2 family members in MM versus MGUS (2) whether the four major subtypes defined as hyperdiploid, CyclinD1, MAF, and MMSET, display specific apoptotic machineries. We showed that among the main anti-apoptotic members (Bcl-2, Bcl-xL, and Mcl-1), Mcl-1 up-regulation discriminated MM from MGUS, in agreement with the prominent role of Mcl-1 in PC differentiation. Surprisingly, the expression of multi-domain pro-apoptotic Bak and Bax were increased during the progression of MGUS to MM. The combined profile of Bcl-2, Bcl-xL, and Mcl-1 was sufficient to distinguish MM molecular groups. While specific pro-apoptotic members expression was observed for each MM subtypes, CyclinD1 subgroup, was identified as a particular entity characterized by a low expression of BH3-only (Puma, Bik, and Bad) and multi-domain pro-apoptotic members (Bax and Bak). Our analysis supports the notion that MM heterogeneity is extended to the differential expression of the Bcl-2 family content in each MM subgroup. The influence of Bcl-2 family profile in the survival of the different patient groups will be further discussed to establish the potential consequences for therapeutic interventions. Finally, the use of distinct pro-survival members in the different steps of immune responses to antigen raises also the question of whether the different Bcl-2 anti-apoptotic profile could reflect a different origin of MM cells.
multiple myeloma; MGUS; Bcl-2 family; CCND1; MMSET, MAF
The histone lysine methyltransferase NSD2 (MMSET/WHSC1) is implicated in diverse diseases and commonly overexpressed in multiple myeloma due to a recurrent t(4;14) chromosomal translocation. However, the precise catalytic activity of NSD2 is obscure, preventing progress in understanding how this enzyme influences chromatin biology and myeloma pathogenesis. Here we show that dimethylation of histone H3 at lysine 36 (H3K36me2) is the principal chromatin-regulatory activity of NSD2. Catalysis of H3K36me2 by NSD2 is sufficient for gene activation. In t(4;14)-positive myeloma cells, the normal genome-wide and gene-specific distribution of H3K36me2 is obliterated, creating a chromatin landscape that selects for a transcription profile favorable for myelomagenesis. Catalytically active NSD2 confers xenograft tumor formation upon t(4;14)-negative cells, and promotes oncogenic transformation of primary cells in an H3K36me2-dependent manner. Together our findings establish H3K36me2 as the primary product generated by NSD2, and demonstrate that genomic disorganization of this canonical chromatin mark by NSD2 initiates oncogenic programming.
Overexpression of FGF receptor 3 (FGFR3) is implicated in the development of t(4;14)-positive multiple myeloma. While FGFR3 is frequently overexpressed and/or activated through mutations in bladder cancer, the functional importance of FGFR3 and its potential as a specific therapeutic target in this disease have not been elucidated in vivo. Here we report that inducible knockdown of FGFR3 in human bladder carcinoma cells arrested cell-cycle progression in culture and markedly attenuated tumor progression in xenografted mice. Further, we developed a unique antibody (R3Mab) that inhibited not only WT FGFR3, but also various mutants of the receptor, including disulfide-linked cysteine mutants. Biochemical analysis and 2.1-Å resolution crystallography revealed that R3Mab bound to a specific FGFR3 epitope that simultaneously blocked ligand binding, prevented receptor dimerization, and induced substantial conformational changes in the receptor. R3Mab exerted potent antitumor activity against bladder carcinoma and t(4;14)-positive multiple myeloma xenografts in mice by antagonizing FGFR3 signaling and eliciting antibody-dependent cell-mediated cytotoxicity (ADCC). These studies provide in vivo evidence demonstrating an oncogenic role of FGFR3 in bladder cancer and support antibody-based targeting of FGFR3 in hematologic and epithelial cancers driven by WT or mutant FGFR3.
Myeloma is a malignant proliferation of monoclonal plasma cells. Although morphologically similar, several subtypes of the disease have been identified at the genetic and molecular level. These genetic subtypes are associated with unique clinico-pathological features and dissimilar outcome. At the top hierarchical level, myeloma can be divided into hyperdiploid and non-hyperdiploid subtypes. The latter is mainly composed of cases harboring IgH translocations, generally associated with more aggressive clinical features and shorter survival. The three main IgH translocations in myeloma are the t(11;14)(q13;q32), t(4;14)(p16;q32) and t(14;16)(q32;q23). Trisomies and a more indolent form of the disease characterize hyperdiploid myeloma. A number of genetic progression factors have been identified including deletions of chromosomes 13 and 17 and abnormalities of chromosome 1 (1p deletion and 1q amplification). Other key drivers of cell survival and proliferation have also been identified such as nuclear factor- B-activating mutations and other deregulation factors for the cyclin-dependent pathways regulators. Further understanding of the biological subtypes of the disease has come from the application of novel techniques such as gene expression profiling and array-based comparative genomic hybridization. The combination of data arising from these studies and that previously elucidated through other mechanisms allows for most myeloma cases to be classified under one of several genetic subtypes. This paper proposes a framework for the classification of myeloma subtypes and provides recommendations for genetic testing. This group proposes that genetic testing needs to be incorporated into daily clinical practice and also as an essential component of all ongoing and future clinical trials.
multiple myeloma; genetics; cytogenetics; molecular; prognosis; gene expression profiling
Multiple myeloma is a malignant proliferation of monoclonal plasma cells leading to clinical features that include hypercalcaemia, renal dysfunction, anaemia, and bone disease (frequently referred to by the acronym CRAB) which represent evidence of end organ failure. Recent evidence has revealed myeloma to be a highly heterogeneous disease composed of multiple molecularly-defined subtypes each with varying clinicopathological features and disease outcomes. The major division within myeloma is between hyperdiploid and nonhyperdiploid subtypes. In this division, hyperdiploid myeloma is characterised by trisomies of certain odd numbered chromosomes, namely, 3, 5, 7, 9, 11, 15, 19, and 21 whereas nonhyperdiploid myeloma is characterised by translocations of the immunoglobulin heavy chain alleles at chromosome 14q32 with various partner chromosomes, the most important of which being 4, 6, 11, 16, and 20. Hyperdiploid and nonhyperdiploid changes appear to represent early or even initiating mutagenic events that are subsequently followed by secondary aberrations including copy number abnormalities, additional translocations, mutations, and epigenetic modifications which lead to plasma cell immortalisation and disease progression. The following review provides a comprehensive coverage of the genetic and epigenetic events contributing to the initiation and progression of multiple myeloma and where possible these abnormalities have been linked to disease prognosis.
Dysregulation of the receptor tyrosine kinase fibroblast growth factor receptor 3 (FGFR3) plays a pathogenic role in a number of human hematopoietic malignancies and solid tumors. These include t(4;14) multiple myeloma associated with ectopic expression of FGFR3 and t(4;12)(p16;p13) acute myeloid leukemia associated with expression of a constitutively activated fusion tyrosine kinase, TEL-FGFR3. We recently reported that FGFR3 directly tyrosine phosphorylates RSK2 at Y529, which consequently regulates RSK2 activation. Here we identified Y707 as an additional tyrosine in RSK2 that is phosphorylated by FGFR3. Phosphorylation at Y707 contributes to RSK2 activation, through a putative disruption of the autoinhibitory αL-helix on the C terminus of RSK2, unlike Y529 phosphorylation, which facilitates ERK binding. Moreover, we found that FGFR3 interacts with RSK2 through residue W332 in the linker region of RSK2 and that this association is required for FGFR3-dependent phosphorylation of RSK2 at Y529 and Y707, as well as the subsequent RSK2 activation. Furthermore, in a murine bone marrow transplant assay, genetic deficiency in RSK2 resulted in a significantly delayed and attenuated myeloproliferative syndrome induced by TEL-FGFR3 as compared with wild-type cells, suggesting a critical role of RSK2 in FGFR3-induced hematopoietic transformation. Our current and previous findings represent a paradigm for tyrosine phosphorylation-dependent regulation of serine-threonine kinases.
Multiple myeloma is a malignant tumour of plasma cells with a median survival of two to three years. Karyotypic instability is seen at the earliest stage of the disease and increases with disease progression, leading to extreme genetic abnormalities similar to solid tumours. Translocations involving the immunoglobulin heavy chain region on chromosome 14q32 are clearly important in the pathogenesis of most myelomas. This review focuses on the different genetic abnormalities found in myeloma and discusses possible pathogenetic mechanisms and the implications for biologically based treatments.
multiple myeloma; cytogenetics; fluorescence in situ hybridisation; chromosomal translocations
Contrary to Total Therapy 2 (TT2), FGFR3-translocation bore no adverse effects on outcome in Total Therapy 3 (TT3) with added bortezomib. DelTP53, another poor-risk feature in TT2, was examined for its prognostic consequences in TT3 present in 10% of 441 patients treated. Not affecting rate or duration of complete response, TP53 haplo-insufficiency also did not compromise, in the 83% with genomically defined low-risk myeloma, survival or event-free survival. FGFR+ and FGFR3− molecular subgroups fared worse in the presence of delTP53 when applying TT2 but not TT3. Thus, delTP53’s prognostic implications were protocol- as well as genome-defined risk- and molecular subgroup-dependent.
Myeloma; TP53; Bortezomib; Prognosis; Genomics
Multiple myeloma (MM) is characterized by recurrent chromosomal translocations. MMSET, identified by its fusion to the IgH locus in t(4;14) MM, is universally overexpressed in t(4;14) MM. In order to identify cell surface biomarkers associated with t(4;14) MM for small molecule or antibody based therapies, we knocked down MMSET expression with shRNA and generated a cell line pair from KMS11, a t(4;14) MM cell line. We used quantitative mass spectrometry to identify plasma membrane proteins associated with MMSET overexpression. Using this approach, 50 cell surface proteins were identified as differentially expressed between KMS11 and KMS11/shMMSET. Western blot and flow cytometry analysis indicated SLAMF7 was over-expressed in t(4;14) MM cell lines and down-regulated by MMSET shRNAs. SLAMF7 expression was also confirmed in primary t(4;14) MM samples by flow cytometry analysis. Quantitative RT-PCR and ChIP analysis indicated MMSET might regulate the transcription level of SLAMF7 and be an important functional element for SLAMF7 promoter activity. Furthermore, SLAMF7 shRNA could induce G1 arrest or apoptosis and reduce clonogenetic capacity in t(4;14) MM cells. Overall, these results illustrated SLAMF7 might be a novel cell surface protein associated with t(4;14) MM. It is potential to develop t(4;14) MM targeted therapy by SLAMF7 antibody mediated drug delivery.
SILAC; quantitative proteomics; oncotargets; multiple myeloma
The transcription factor IRF4 is required during an immune response for lymphocyte activation and the generation of immunoglobulin-secreting plasma cells1-3. Multiple myeloma, a malignancy of plasma cells, has a complex molecular etiology with several subgroups defined by gene expression profiling and recurrent chromosomal translocations4,5. Moreover, the malignant clone can sustain multiple oncogenic lesions, accumulating genetic damage as the disease progresses6,7. Current therapies for myeloma can extend survival but are not curative8,9. Hence, new therapeutic strategies are needed that target molecular pathways shared by all subtypes of myeloma. Using a loss-of-function, RNA-interference-based genetic screen we show here that IRF4 inhibition was toxic to myeloma cell lines, regardless of transforming oncogenic mechanism. Gene expression profiling and genome-wide chromatin immunoprecipitation analysis uncovered an extensive network of IRF4 target genes and identified MYC as a direct target of IRF4 in activated B cells and myeloma. Unexpectedly, IRF4 was itself a direct target of MYC transactivation, generating an autoregulatory circuit in myeloma cells. Though IRF4 is not genetically altered in most myelomas, they are nonetheless addicted to an aberrant IRF4 regulatory network that fuses the gene expression programs of normal plasma cells and activated B cells.
Multiple myeloma remains an incurable disease despite the introduction of the immunomodulatory drugs (IMiDs) thalidomide and lenalidomide and the proteasome inhibitor bortezomib that have improved the outcome of patients with both newly diagnosed and relapsed/refractory disease. However, patients who relapse after treatment with these agents or are refractory to them represent an unmet need and highlight the necessity for the development of novel anti-myeloma agents. Pomalidomide is an IMiD, structurally related to thalidomide, with enhanced antiangiogenic, antineoplastic, and anti-inflammatory properties and exhibiting potent anti-myeloma activity in vitro and in vivo. Pomalidomide has shown remarkable activity in patients who were refractory to both bortezomib and lenalidomide in Phase II and III studies. This paper reviews the chemistry and mechanisms of action of pomalidomide as well as all the available data from clinical trials on pomalidomide use in patients with refractory/relapsed multiple myeloma.
immunomodulatory drugs; cereblon; angiogenesis; lenalidomide; refractory
Lenalidomide and bortezomib are active in relapsed and relapsed/refractory multiple myeloma (MM). In preclinical studies, lenalidomide sensitized MM cells to bortezomib and dexamethasone. This phase I, dose-escalation study (ie, NCT00153933) evaluated safety and determined the maximum-tolerated dose (MTD) of lenalidomide plus bortezomib in patients with relapsed or with relapsed and refractory MM.
Patients and Methods
Patients received lenalidomide 5, 10, or 15 mg/d on days 1 through 14 and received bortezomib 1.0 or 1.3 mg/m2 on days 1, 4, 8, and 11 of 21-day cycles. Dexamethasone (20mg or 40 mg on days 1, 2, 4, 5, 8, 9, 11, and 12) was added for progressive disease after two cycles. Primary end points were safety and MTD determination.
Thirty-eight patients were enrolled across six dose cohorts. The MTD was lenalidomide 15 mg/d plus bortezomib 1.0 mg/m2. Dose-limiting toxicities (n = 1 for each) were grade 3 hyponatremia and herpes zoster reactivation and grade 4 neutropenia. The most common treatment-related, grades 3 to 4 toxicities included reversible neutropenia, thrombocytopenia, anemia, and leukopenia. Among 36 response-evaluable patients, 61% (90% CI, 46% to 75%) achieved minimal response or better. Among 18 patients who had dexamethasone added, 83% (90% CI, 62% to 95%) achieved stable disease or better. Median overall survival was 37 months.
Lenalidomide plus bortezomib was well tolerated and showed promising activity with durable responses in patients with relapsed and relapsed/refractory MM, including patients previously treated with lenalidomide, bortezomib, and/or thalidomide. The combination of lenalidomide, bortezomib, and dexamethasone is being investigated in a phase II study in this setting and in newly diagnosed MM.
Multiple myeloma (MM) is a neoplastic plasma cell disorder that results in end-organ damage (hypercalcemia, renal insufficiency, anemia, or skeletal lesions). Patients should not be treated unless they have symptomatic (end-organ damage) MM. They should be classified as having high-risk or standard-risk disease. Patients are classified as high risk in the presence of hypodiploidy or deletion of chromosome 13 (del) with conventional cytogenetics, the presence of t(4:14), t(14;16), t(14;20) translocations or del(17p) with fluorescence in situ hybridization. High-risk disease accounts for about 25% of patients with symptomatic MM. If the patient is deemed eligible for an autologous stem cell transplantation (ASCT), 3 or 4 cycles of lenalidomide and low-dose dexamethasone, or bortezomib and dexamethasone, or thalidomide and dexamethasone are reasonable choices. Stem cells should then be collected and one may proceed with an ASCT. If the patient has a complete response or a very good partial response (VGPR), the patient may be followed without maintenance therapy. If the patient has a less than VGPR, a second ASCT is encouraged. If the patient is in the high-risk group, a bortezomib-containing regimen to maximum response followed by 2 additional cycles of therapy is a reasonable approach. Lenalidomide and low-dose dexamethasone is another option for maintenance until progression. If the patient is considered ineligible for an ASCT, then melphalan, prednisone, and thalidomide is suggested for the standard-risk patient, and melphalan, prednisone, and bortezomib (MPV) for the high-risk patient. Treatment of relapsed or refractory MM is covered. The novel therapies—thalidomide, bortezomib, and lenalidomide—have resulted in improved survival rates. The complications of MM are also described. Multiple myeloma is a plasma cell neoplasm that is characterized by a single clone of plasma cells producing a monoclonal protein (M-protein). The malignant proliferation of plasma cells produces skeletal destruction that leads to bone pain and pathologic fractures. The M-protein might lead to renal failure, hyperviscosity syndrome, or through the suppression of uninvolved immunoglobulins, recurrent infections. Anemia and hypercalcemia are common complications.
Autologous stem cell transplantation; Bortezomib; Lenalidomide; Thalidomide
The chromosomal translocation t(4;14) deregulates MMSET (WHSC1/NSD2) expression and is a poor prognostic factor in multiple myeloma (MM). MMSET encodes two major protein isoforms. We have characterized the role of the shorter isoform (REIIBP) in myeloma cells and identified a clear and novel interaction of REIIBP with members of the SMN (survival of motor neuron) complex that directly affects the assembly of the spliceosomal ribonucleic particles. Using RNA-seq we show that REIIBP influences the RNA splicing pattern of the cell. This new discovery provides novel insights into the understanding of MM pathology, and potential new leads for therapeutic targeting.