Promiscuous translocations into immunoglobulin heavy chain switch regions in multiple myeloma

Understanding biology to tackle the disease: Multiple myeloma from bench to bedside, and back

Multiple myeloma (MM) is a cancer of antibody-producing plasma cells. The pathognomonic laboratory finding is a monoclonal immunoglobulin or free light chain in the serum and/or urine in association with bone marrow infiltration by malignant plasma cells. MM develops from a premalignant condition, monoclonal gammopathy of undetermined significance (MGUS), often via an intermediate stage termed smoldering multiple myeloma (SMM), which differs from active myeloma by the absence of disease-related end-organ damage. Unlike MGUS and SMM, active MM requires therapy. Over the past 6 decades, major advancements in the care of MM patients have occurred, in particular, the introduction of novel agents (ie, proteasome inhibitors, immunomodulatory agents) and the implementation of hematopoietic stem cell transplantation in suitable candidates. The effectiveness and good tolerability of novel agents allowed for their combined use in induction, consolidation, and maintenance therapy, resulting in deeper and more sustained clinical response and extended progression-free and overall survival. Previously a rapidly lethal cancer with few therapeutic options, MM is the hematologic cancer with the most novel US Food and Drug Administration-approved drugs in the past 15 years. These advances have resulted in more frequent long-term remissions, transforming MM into a chronic illness for many patients.

High prevalence of immunoglobulin light chain gene aberrations as revealed by FISH in multiple myeloma and MGUS

Multiple myeloma (MM) is a malignant B-cell neoplasm characterized by an uncontrolled proliferation of aberrant plasma cells in the bone marrow. Chromosome aberrations in MM are complex and represent a hallmark of the disease, involving many chromosomes that are altered both numerically and structurally. Nearly half of the cases are nonhyperdiploid and show IGH translocations with the following partner genes: CCND1, FGFR3 and MMSET, MAF, MAFB, and CCND3. The remaining 50% are grouped into a hyperdiploid group that is characterized by multiple trisomies involving chromosomes 3, 5, 7, 9, 11, 15, 19, and 21. In this study, we analyzed the immunoglobulin light chain kappa (IGK, 2p12) and lambda (IGL, 22q11) loci in 150 cases, mostly with MM but in a few cases monoclonal gammopathy of undetermined significance (MGUS), without IGH translocations. We identified aberrations in 27% (= 40 patients) including rearrangements (12%), gains (12%), and deletions (4.6%). In 6 of 18 patients with IGK or/and IGL rearrangements, we detected a MYC rearrangement which suggests that MYC is the translocation partner in the majority of these cases.

In multiple myeloma, 14q32 translocations are nonrandom chromosomal fusions driving high expression levels of the respective partner genes

In studies of patients with multiple myeloma (MM), gene expression profiling (GEP) of myeloma cells demonstrates substantially higher expression of MMSET, FGFR3, CCND3, CCND1, MAF, and MAFB--the partner genes of 14q32 translocations--than GEP of plasma cells from healthy individuals. Interphase fluorescent in situ hybridization (FISH) was used to discriminate between chromosomal translocations involving different regions of the immunoglobulin heavy chain (IGH) genes at 14q32. With special probes designed for the constant region (IGHC) and the variable region (IGHV), IGH translocations were shown to be definite, nonrandom chromosomal fusions of IGHC with the loci of FGFR3, CCND1, CCND3, MAF, and MAFB genes; and IGHV with the locus of MMSET gene. When correlated with GEP results, the IGH translocations were found to drive expression levels of the partner genes to significantly higher levels (spikes) than copy-number variations. Hence, 42% of IGH translocations were identified among newly diagnosed MM patients (448/1,060). As GEP has become essential for assessing cancer risk, this novel approach is highly consistent with the cytogenetic features of the chromosomal translocations to effectively stratify molecular subgroups of MM on the basis of gene expression profiles of the IGH translocation partner genes in myeloma cells. © 2014 Wiley Periodicals, Inc.

Promiscuous MYC locus rearrangements hijack enhancers but mostly super-enhancers to dysregulate MYC expression in multiple myeloma

MYC locus rearrangements – often complex combinations of translocations, insertions, deletions, and inversions - in multiple myeloma (MM) were thought to be a late progression event, which often did not involve immunoglobulin genes. Yet germinal center activation of MYC expression has been reported to cause progression to MM in an MGUS prone mouse strain. Although previously detected in 16% of MM, we find MYC rearrangements in nearly 50% of MM, including smoldering MM, and they are heterogeneous in some cases. Rearrangements reposition MYC near a limited number of genes associated with conventional enhancers, but mostly with super-enhancers (e.g., IGH, IGL, IGK, NSMCE2, TXNDC5, FAM46C, FOXO3, IGJ, PRDM1). MYC rearrangements are associated with a significant increase of MYC expression that is monoallelic, but MM tumors lacking a rearrangement have bi-allelic MYC expression at significantly higher levels than in MGUS. We also show that germinal center activation of MYC does not cause MM in a mouse strain that rarely develops spontaneous MGUS. It appears that increased MYC expression at the MGUS/MM transition usually is bi-allelic, but sometimes can be mono-allelic if there is a MYC rearrangement. Our data suggests that MYC rearrangements, regardless of when they occur during MM pathogenesis, provide one event that contributes to tumor autonomy.

High-risk multiple myeloma: different definitions, different outcomes?

Multiple myeloma (MM) is a clonal plasma cell malignancy. Although MM is still not completely curable, it can be maintained at the level of a long-term chronic condition. Irrespective of the treatment strategy, relapse is still a major problem for most patients. Approximately 10% to 15% of all MM patients relapse early and have poor prognosis and outcome. Currently, there are many ways of identifying these high-risk patients using cytogenetics or molecular biology. Despite these various approaches to definition of high risk patients, a clear definition of high-risk MM has not been widely accepted. In this review, we discuss and compare various approaches, and their strengths and weaknesses in early identification of high-risk MM patients.

Myeloma stem cell concepts, heterogeneity and plasticity of multiple myeloma

Multiple myeloma (MM) is a haematological malignancy characterized by the accumulation of clonal plasma cells (PCs) in the bone marrow (BM). Although novel therapeutic strategies have prolonged survival of patients, the disease remains difficult to treat with a high risk of relapse. The failure of therapy is thought to be associated with a persistent population of the so-called MM stem cells or myeloma initiating cells (MIC) that exhibit tumour-initiating potential, self-renewal and resistance to chemotherapy. However, the population responsible for the origin and sustainability of tumour mass has not been clearly characterized so far. This review summarizes current myeloma stem cell concepts and suggests that high phenotypic and intra-clonal heterogeneity, together with plasticity potential of MM might be other contributing factors explaining discrepancies among particular concepts and contributing to the treatment failure.

Transcriptional repression of Bim by a novel YY1-RelA complex is essential for the survival and growth of Multiple Myeloma

Multiple Myeloma (MM) is an incurable plasma cell cancer that is caused by several chromosomal translocations and gene deletions. Although deregulation of several signaling pathways including the Nuclear Factor-Kappa B (NF-κB) pathway has been reported in MM, the molecular requirement and the crosstalk between NF-κB and its target genes in MM cell survival has been largely unclear. Here, we report that Yin Yang1 (YY1), a target gene for NF-κB, is hyperexpressed in most MM tumor cells obtained from human patients, exhibits constitutive nuclear localization, and is essential for survival of MM cells. Mechanistically, we report a novel YY1-RelA complex formation, which is essential to transcriptionally repress a proapoptotic gene Bim. In line with this, depletion of YY1 or RelA resulted in elevated levels of Bim and apoptosis. Moreover, both YY1 and RelA are recruited to the Bim promoter and are required to repress the Bim promoter. Importantly, depletion of YY1 or RelA almost completely impaired the colony forming ability of MM progenitor cells suggesting that both RelA and YY1 are essential for the survival and growth of MM progenitor cells. Moreover, depletion of either YY1 or RelA completely inhibited MM tumor growth in xenograft models for human myeloma. Thus, a novel RelA-YY1 transcriptional repression complex is an attractive drug target in MM.

Characterization of IGH locus breakpoints in multiple myeloma indicates a subset of translocations appear to occur in pregerminal center B cells

IGH translocations in myeloma can occur through at least 5 mechanisms. t(11;14) and t(14;20) DH-JH rearrangement-mediated translocations occur indicating these appear to occur in a pregerminal center cell.

Significance of oligoclonal bands after stem cell transplantation in multiple myeloma cases

OBJECTIVE

To determine the characteristics of oligoclonal bands that are frequently detected by serum protein electrophoresis (SPEP) and immunofixation electrophoresis (IFE) after stem cell transplantation.

METHODS

We retrospectively analyzed 56 patients with multiple myeloma (MM) undergoing transplantation, and standard immunofixation electrophoresis was used to identify and quantify paraproteins.

RESULTS

The median follow-up was 35 months (range, 10-76 months) and 21 patients relapsed. Twelve (25.0%) demonstrated oligoclonal bands after a median time 1.4 months (range, 1-3 months), with a median duration of 5.8 months (range, 1-15 months). The majority patients with oligoclonal bands had normal quantities of immunoglobulins and the one year event free survival (EFS) was 92%, even higher than for patients without OBs (P=0.002).

CONCLUSION

Oligoclonal bands frequent develop post-transplantation in MM cases. In the vast majority of patients, they may not represent relapsed disease, and more likely represent a transient phenomenon representing recovery of impaired immunoglobulin production.

Report from the European Myeloma Network on interphase FISH in multiple myeloma and related disorders

The European Myeloma Network has organized two workshops on fluorescence in situ hybridization in multiple myeloma. The first aimed to identify specific indications and consensus technical approaches of current practice. A second workshop followed a quality control exercise in which 21 laboratories analyzed diagnostic cases of purified plasma cells for recurrent abnormalities. The summary report was discussed at the EHA Myeloma Scientific Working Group Meeting 2010. During the quality control exercise, there was acceptable agreement on more than 1,000 tests. The conclusions from the exercise were that the primary clinical applications for FISH analysis were for newly diagnosed cases of MM or frank relapse cases. A range of technical recommendations included: 1) material should be part of the first draw of the aspirate; 2) samples should be sent at suitable times to allow for the lengthy processing procedure; 3) most importantly, PCs must be purified or specifically identified; 4) positive cut-off levels should be relatively conservative: 10% for fusion or break-apart probes, 20% for numerical abnormalities; 5) informative probes should be combined to best effect; 6) in specialist laboratories, a single experienced analyst is considered adequate; 7) at least 100 PC should be scored; 8) essential abnormalities to test for are t(4;14), t(14;16) and 17p13 deletions; 9) suitable commercial probes should be available for clinically relevant abnormalities; 10) the clinical report should be expressed clearly and must state the percentage of PC involved and the method used for identification; 11) a retrospective European based FISH data bank linked to clinical data should be generated; and 12) prospective analysis should be centralized for upcoming trials based on the recommendations made. The European Myeloma Network aims to build on these recommendations to establish standards for a common European data base to define subgroups with prognostic significance.

Preclinical evaluation of a novel SIRT1 modulator SRT1720 in multiple myeloma cells

SIRT1 belongs to the silent information regulator 2 (Sir2) protein family of enzymes and functions as a NAD(+) -dependent class III histone deacetylase. Here, we examined the anti-multiple myeloma (MM) activity of a novel oral agent, SRT1720, which targets SIRT1. Treatment of MM cells with SRT1720 inhibited growth and induced apoptosis in MM cells resistant to conventional and bortezomib therapies without significantly affecting the viability of normal cells. Mechanistic studies showed that anti-MM activity of SRT1720 is associated with: (i) activation of caspase-8, caspase-9, caspase-3, poly(ADP) ribose polymerase; (ii) increase in reactive oxygen species; (iii) induction of phosphorylated ataxia telangiectasia mutated/checkpoint kinase 2 signalling; (iv) decrease in vascular endothelial growth factor-induced migration of MM cells and associated angiogenesis; and (v) inhibition of nuclear factor-κB. Blockade of ATM attenuated SRT1720-induced MM cell death. In animal tumour model studies, SRT1720 inhibited MM tumour growth. Finally, SRT1720 enhanced the cytotoxic activity of bortezomib or dexamethasone. Our preclinical studies provide the rationale for novel therapeutics targeting SIRT1 in MM.

Malignant pirates of the immune system

At great human cost, cancer is the largest genetic experiment ever conducted. This review highlights how lymphoid malignancies have genetically perverted normal immune signaling and regulatory mechanisms for their selfish oncogenic goals of unlimited proliferation, perpetual survival and evasion of the immune response.

Genomic stratification of multiple myeloma treated with novel agents

Cytogenetic testing is now routinely performed for the prognostic work-up of multiple myeloma (MM). The abnormalities del(17p), t(4;14) and del(13q) have been established as predictors of poor outcome in patients with MM treated with conventional chemotherapy or stem cell transplant; chromosome 1q gains and 1p losses have also been identified as novel prognostic factors. In recent years, bortezomib and lenalidomide have emerged as effective treatments for both relapsed/refractory and newly diagnosed MM. However, the effect of cytogenetic abnormalities is unclear among patients with MM treated with these novel agents. Here we review recent studies that analyze the impact of specific genomic aberrations on the outcome of MM treated with bortezomib and/or lenalidomide.

Rapid high-resolution mapping of balanced chromosomal rearrangements on tiling CGH arrays

The diagnosis and classification of many cancers depends in part on the identification of large-scale genomic aberrations such as chromosomal deletions, duplications, and balanced translocations. Array-based comparative genomic hybridization (array CGH) can detect chromosomal imbalances on a genome-wide scale but cannot reliably identify balanced chromosomal rearrangements. We describe a simple modification of array CGH that enables simultaneous identification of recurrent balanced rearrangements and genomic imbalances on the same microarray. Using custom tiling oligonucleotide arrays and gene-specific linear amplification primers, translocation CGH (tCGH) maps balanced rearrangements to ∼100-base resolution and facilitates the rapid cloning and sequencing of novel rearrangement breakpoints. As proof of principle, we used tCGH to characterize nine of the most common gene fusions in mature B-cell neoplasms and myeloid leukemias. Because tCGH can be performed in any CGH-capable laboratory and can screen for multiple recurrent translocations and genome-wide imbalances, it should be of broad utility in the diagnosis and classification of various types of lymphomas, leukemias, and solid tumors.

Novel therapies in MM: from the aspect of preclinical studies

During the last decade, thalidomide, lenalidomide, and bortezomib have been approved by the US Food and Drug Administration for the treatment of MM; however, MM remains incurable. The development and progression of multiple myeloma (MM) is a complex multi-step process involving genetic abnormalities in tumor cells at both early and late stages. Moreover, soluble factors and cell-cell contact within the tumor bone marrow (BM) microenvironment promotes MM cell growth, survival, and drug resistance. A number of novel agents targeting both tumor cells and growth factors in the BM milieu have been developed. Currently they are under evaluation in preclinical studies, as single agents and/or in combination, to improve outcome of MM patients.

Dominant genetic aberrations and coexistent EBV infection in HIV-related oral plasmablastic lymphomas

We present common cytogenetic features in the largest cohort of plasmablastic lymphoma (PBL) of the oral cavity published to date. This cohort included 45 patients, 32 of whom had a known HIV status, of which 31 were HIV positive. Ninety eight per cent of all PBL cases were known to be EBV positive. In line with previous studies, we found that rearrangements of the MYC gene was the most common genetic abnormality seen in 60% of cases with the immunoglobulin heavy chain (IGH) locus as a partner in 51% of cases. Additional complex genetic aberrations were frequent, in particular, an increased copy number of the CCND1 gene was seen in 41% of cases with true amplification of CCND1 in 15% of cases. Aneuploidy was also observed for the BCL6 gene in 28% of cases. Interestingly, rearrangements of both IGH genes were detected in 16% of cases with t(14;18) and t(11;14) respectively involved in conjunction with a t(8;14) in two cases. These bi-allelic IGH rearrangements have not been described before in oral PBL. Our results reinforce the notion that EBV infection and MYC rearrangements are important events in the pathogenesis of oral PBL. The genetic diversity and complexity observed in these cases, underlines the importance to genetically characterise PBL patients at presentation as this may inform the choice of more effective treatment modalities.

In vitro and in vivo selective antitumor activity of a novel orally bioavailable proteasome inhibitor MLN9708 against multiple myeloma cells

PURPOSE

The success of bortezomib therapy for treatment of multiple myeloma (MM) led to the development of structurally and pharmacologically distinct novel proteasome inhibitors. In the present study, we evaluated the efficacy of one such novel orally bioactive proteasome inhibitor MLN9708/MLN2238 in MM using well-established in vitro and in vivo models.

EXPERIMENTAL DESIGN

MM cell lines, primary patient cells, and the human MM xenograft animal model were used to study the antitumor activity of MN2238.

RESULTS

Treatment of MM cells with MLN2238 predominantly inhibits chymotrypsin-like activity of the proteasome and induces accumulation of ubiquitinated proteins. MLN2238 inhibits growth and induces apoptosis in MM cells resistant to conventional and bortezomib therapies without affecting the viability of normal cells. In animal tumor model studies, MLN2238 is well tolerated and inhibits tumor growth with significantly reduced tumor recurrence. A head-to-head analysis of MLN2238 versus bortezomib showed a significantly longer survival time in mice treated with MLN2238 than mice receiving bortezomib. Immununostaining of MM tumors from MLN2238-treated mice showed growth inhibition, apoptosis, and a decrease in associated angiogenesis. Mechanistic studies showed that MLN2238-triggered apoptosis is associated with activation of caspase-3, caspase-8, and caspase-9; increase in p53, p21, NOXA, PUMA, and E2F; induction of endoplasmic reticulum (ER) stress response proteins Bip, phospho-eIF2-α, and CHOP; and inhibition of nuclear factor kappa B. Finally, combining MLN2238 with lenalidomide, histone deacetylase inhibitor suberoylanilide hydroxamic acid, or dexamethasone triggers synergistic anti-MM activity.

CONCLUSION

Our preclinical study supports clinical evaluation of MLN9708, alone or in combination, as a potential MM therapy.

Determinants of sensitivity to DZNep induced apoptosis in multiple myeloma cells

The 3-Deazaneplanocin A (DZNep), one of S-adenosylhomocysteine (AdoHcy) hydrolase inhibitors, has shown antitumor activities in a broad range of solid tumors and acute myeloid leukemia. Here, we examined its effects on multiple myeloma (MM) cells and found that, at 500 nM, it potently inhibited growth and induced apoptosis in 2 of 8 MM cell lines. RNA from un-treated and DZNep treated cells was profiled by Affymetrix HG-U133 Plus 2.0 microarray and genes with a significant change in gene expression were determined by significance analysis of microarray (SAM) testing. ALOX5 was the most down-regulated gene (5.8-fold) in sensitive cells and was expressed at low level in resistant cells. The results were corroborated by quantitative RT-PCR. Western-blot analysis indicated ALOX5 was highly expressed only in sensitive cell line H929 and greatly decreased upon DZNep treatment. Ectopic expression of ALOX5 reduced sensitivity to DZNep in H929 cells. Furthermore, down-regulation of ALOX5 by RNA interference could also induce apoptosis in H929. Gene expression analysis on MM patient dataset indicated ALOX5 expression was significantly higher in MM patients compared to normal plasma cells. We also found that Bcl-2 was overexpressed in DZNep insensitive cells, and cotreatment with DZNep and ABT-737, a Bcl-2 family inhibitor, synergistically inhibited growth and induced apoptosis of DZNep insensitive MM cells. Taken together, this study shows one of mechanisms of the DZNep efficacy on MM correlates with its ability to down-regulate the ALOX5 levels. In addition, DZNep insensitivity might be associated with overexpression of Bcl-2, and the combination of ABT-737 and DZNep could synergistically induced apoptosis. These results suggest that DZNep may be exploited therapeutically for a subset of MM.

The prognostic significance of cytogenetics and molecular profiling in multiple myeloma

Multiple myeloma (MM) is a plasma cell malignancy characterized by very complex cytogenetic and molecular genetic aberrations. In newly diagnosed symptomatic patients, the modal chromosome number is usually either hyperdiploid with multiple trisomies or hypodiploid with one of several types of immunoglobulin heavy chain (Ig) translocations. The chromosome ploidy status and Ig rearrangements are two genetic criteria that are used to help stratify patients into prognostic groups based on the findings of conventional cytogenetics and fluorescence in situ hybridization (FISH). In general, the hypodiploid group with t(4;14)(p16;q32) or t(14;16)(q32;q23) is considered a high-risk group, while the hyperdiploid patients with t(11;14)(q13;q32) are considered a better prognostic group. As the disease progresses, it becomes more proliferative and develops a number of secondary chromosome aberrations. These secondary aberrations commonly involve MYC rearrangements, del(13q), del(17p), and the deletion of 1p and/or amplification of 1q. Of the secondary aberrations, del(17p) is consistently associated with poor prognosis. All of these cytogenetic aberrations and many additional ones are now identified by means of high resolution molecular profiling. Gene expression profiling (GEP), array comparative genomic hybridization (aCGH), and single-nucleotide polymorphism (SNP) arrays have been able to identify novel genetic aberration patterns that have previously gone unrecognized. With the integration of data from these profiling techniques, new subclassifications of MM have been proposed which define distinct molecular genetic subgroups. In this review, the findings from conventional cytogenetics, interphase FISH, GEP, aCGH, and SNP profiles are described to provide the conceptual framework for defining the emerging molecular genetic subgroups with prognostic significance.

Pathogenesis of myeloma

Multiple myeloma (MM) is a neoplasm of post-germinal center, terminally differentiated B cells. It is characterized by a multifocal proliferation of clonal, long-lived plasma cells within the bone marrow (BM) and associated skeletal destruction, serum monoclonal gammopathy, immune suppression, and end-organ sequelae. MM is preceded by an age-progressive premalignant condition termed monoclonal gammopathy of undetermined significance. Unlike the genomes of most hematological malignancies, and similar to those of solid-tissue neoplasms, MM genomes are typified by numerous structural and numerical chromosomal aberrations as well as mutations in a number of oncogenes and tumor-suppressor genes, some of which have been linked to disease pathogenesis and clinical behavior. Recent studies have also defined the importance of interactions between the MM cells and their BM microenvironment, dysregulation in signaling pathways and in a specialized subpopulation of cells within the tumor (termed myeloma cancer stem cells) for tumor cell growth and survival, and the development of resistance to therapy.

Translocation of an antibody transgene requires AID and occurs by interchromosomal switching to all switch regions except the mu switch region

Immunoglobulin (Ig) class switch recombination (CSR) occurs most often by intrachromosomal recombinations between switch (S) regions located on a single chromosome, but it can also occur by interchomosomal recombinations between Ig heavy chain (Igh) S regions located on chomosomal homologs. Interchromosomal recombinations have also been found between chromosomes that are not homologs; examples are Igh/c-myc and Igh/transgene translocations. Most, but not all, studies have indicated that activation-induced cytidine deaminase (AID) is important in Igh/c-myc translocations. The role of AID has not been determined for Igh/transgene translocations. We now show that the majority of Igh/transgene translocations between non-homologs from an Ig transgenic mouse are dependent on AID, but we also find a small number of these translocations that can occur in the absence of AID. Surprisingly, our results also indicate that, although Sγ switch sequences in the endogenous Igh locus participate in chromosomal translocations with the non-homolog transgene-bearing chromosome, Sμ switch sequences do not. This contrasts with the fact that both endogenous Sμ and Sγ sequences participate in intrachromosomal CSR. Our findings suggest the operation of a regulatory mechanism that can differentially control the accessibility of Sμ and Sγ regions for non-homolog translocations even when both are accessible for intrachromosomal recombination.

Pathogenesis of non-Hodgkin's lymphoma

The understanding of the molecular pathogenesis of non-Hodgkin's lymphomas (NHL) has significantly improved in recent years. Advances in molecular biology and genetics lead to the identification and characterization of several oncogenic pathways involved in lymphomagenesis. This knowledge will ultimately lead to improved diagnostic and therapeutic strategies for patients with NHL. This review summarizes current concepts of the molecular pathogenesis of the most common NHL subtypes, with a special emphasis on diffuse large B-cell lymphoma, the most common lymphoma subtype.

Multiple myeloma: biology of the disease

Multiple myeloma (MM) is a clonal B-cell malignancy characterized by the aberrant expansion of plasma cells within the bone marrow, as well as at extramedullary sites. Decades of scientific research are now beginning to unravel the intricate biology that underlies the pathophysiology of MM. In particular, the roles of cellular differentiation, molecular pathogenesis, and oncogenes involved in the natural history of MM are becoming clearer. This has enabled the identification of specific cytokines, adhesion molecules, and stromal cells that affect MM cell development, disease progression, and treatment responses. This review describes our current understanding regarding the biology of MM, and how this has led to a robust pipeline of novel therapeutic agents with the potential to overcome resistance to existing MM therapies and, therefore, further improve outcomes in patients with MM.

Advances in understanding monoclonal gammopathy of undetermined significance as a precursor of multiple myeloma

Monoclonal gammopathy of undetermined significance (MGUS) affects at least 3% of the population above the age of 50 and is the precursor to multiple myeloma (MM), an incurable malignancy of plasma cells. Recent advances in MGUS include: an improved understanding of the pathogenesis of MGUS and its progression to MM, involving molecular events intrinsic to the malignant plasma cell as well as the microenvironment; novel techniques to assess risk for progression to MM using serum-free light-chain analysis and immunophenotyping; and a renewed interest in chemoprevention of MM. In the future, continued improvement in our understanding of MGUS will lead to the development of better biomarkers for prognosis and therapies for chemoprevention of MM.

Over-expression of CCL3 MIP-1alpha in a blastoid mantle cell lymphoma with hypercalcemia

We analyzed a case with the blastoid variant of mantle cell lymphoma (MCL-BV), a rare subtype of B-cell lymphoma, presenting with marked hypercalcemia at diagnosis. Enzyme-linked immunosorbent assay (ELISA) showed elevated serum levels of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-1alpha (MIP-1alpha), and type I collagen telopeptide, but not parathyroid hormone, calcitriol or parathyroid hormone-related peptide at diagnosis, suggesting local osteoclastic hypercalcemia in this case. By reverse transcription polymerase chain reaction (RT-PCR) analysis, we found predominant expression of mRNA for MIP-1alpha in addition to those for receptor-activator of nuclear-factor kappa B ligand (RANKL), TNF-alpha, and IL-6 in lymphoma cells obtained from the patient. Furthermore, recombinant MIP-1alpha significantly stimulated (3)H-thymidine uptake by isolated MCL cells in vitro. Treatment with intravenous fluids, bisphosphonate, and methylprednisolone followed by combination chemotherapy promptly corrects the hypercalcemia and successfully induced complete remission, which was accompanied by a decrease of these cytokines in the serum, including MIP-1alpha. In the present case, MIP-1alpha, an osteoclast-activating factor produced by mantle lymphoma cells, may contribute to the development of hypercalcemia. It likely acts through RANKL expression in tumor cells and/or stroma cells, as indicated in multiple myeloma (MM) and adult T-cell leukemia/lymphoma (ATLL). Furthermore, MIP-1alpha is also involved in the development of an aggressive phenotype on MCL by stimulating proliferation of these lymphoma cells. In summary, the present study demonstrated that MIP-1alpha is an important factor in the development of both hypercalcemia and an aggressive phenotype in some types of B-cell lymphoma.

Monitoring bortezomib therapy in multiple myeloma: screening of cyclin D1, D2, and D3 via reliable real-time polymerase chain reaction and association with clinico-pathological features and outcome

Cyclins D1, D2, and D3 (CCND1, 2, 3) are regulated by proteasomal degradation. Their overexpression in multiple myeloma (MM) has prognostic value. We performed this pilot study to analyze a possible association between CCND1-3 overexpression and response to treatment with the proteasome inhibitor bortezomib, since a specific prognostic marker for bortezomib response has not been reported, but would be ideal to predict who benefits most from bortezomib in times of several potentially efficient therapeutic options. Bone marrow (BM) specimens of 20/47 consecutive patients were available for reliable CCND1-3 analyses by real-time PCR. With CCND1 overexpression in 9/20 patients, the risk for progression after bortezomib treatment was significantly decreased (HR 0.102, 95% CI 0.021-0.498, p = 0.0048) and progression-free survival substantially prolonged (p = 0.0011). Our study is the first to suggest that overexpressed CCND1 in MM is an independent prognostic marker associated with a more durable response to bortezomib. These preliminary results warrant a larger study.

A novel orally active proteasome inhibitor ONX 0912 triggers in vitro and in vivo cytotoxicity in multiple myeloma

Bortezomib therapy has proven successful for the treatment of relapsed, relapsed/refractory, and newly diagnosed multiple myeloma (MM). At present, bortezomib is available as an intravenous injection, and its prolonged treatment is associated with toxicity and development of drug resistance. Here we show that the novel proteasome inhibitor ONX 0912, a tripeptide epoxyketone, inhibits growth and induces apoptosis in MM cells resistant to conventional and bortezomib therapies. The anti-MM activity of ONX-0912 is associated with activation of caspase-8, caspase-9, caspase-3, and poly(ADP) ribose polymerase, as well as inhibition of migration of MM cells and angiogenesis. ONX 0912, like bortezomib, predominantly inhibits chymotrypsin-like activity of the proteasome and is distinct from bortezomib in its chemical structure. Importantly, ONX 0912 is orally bioactive. In animal tumor model studies, ONX 0912 significantly reduced tumor progression and prolonged survival. Immununostaining of MM tumors from ONX 0912-treated mice showed growth inhibition, apoptosis, and a decrease in associated angiogenesis. Finally, ONX 0912 enhances anti-MM activity of bortezomib, lenalidomide dexamethasone, or pan-histone deacetylase inhibitor. Taken together, our study provides the rationale for clinical protocols evaluating ONX 0912, either alone or in combination, to improve patient outcome in MM.

C-MAF Oncogene Dysregulation in Multiple Myeloma: Frequency and Biological Relevance

To investigate the frequency and possible biological consequences of c-maf dysregulation, we designed c-maf and IL-4 real-time RT-PCR assays for determination of c-maf and IL-4 mRNA levels. Using the c-maf real-time RT-PCR assay, we tested a panel of 14 B-cell lines, 135 diagnostic bone marrow (BM) samples from patients with multiple myeloma and 10 BM samples from normal donors. In B cell lines and flowsorted CD38++/CD19-/CD56++ myeloma plasma cells (N = 14) the c-maf/GAPDH and IL-4/GAPDH ratios were determined simultaneously using real time RT-PCR. All B cell lines used in the study were characterized by flow cytometry and tested for the presence of Ebstein-Barr virus (EBV). B-cell lines, that were PCR negative for EBV and had a phenotype typical for primary myeloma cells, expressed medium to high levels of c-maf mRNA. However, all EBV PCR positive cell lines, showed a more immature phenotype, lacked expression of aberrant surface markers and contained very low levels of c-maf mRNA. In 4.4% (6/135) of MM patients tested, a c-maf mRNA level comparable to the cell line RPMI 8226 containing at (16:22), translocation was found. In addition, all c-maf positive myeloma cell lines and CD38++/CD19-/CD56++ myeloma plasma cells tested were IL-4 negative. In conclusion, high levels of c-maf mRNA were observed in "true MM cell lines" and 4.4% of MM patients. Further, c-maf dysregulation in myeloma plasma cells did not cause induction of IL-4 transcription.

[Molecular pathology of plasma cell neoplasms]

Plasma cell myeloma (PCM) and related immunosecretory disorders are a group of B-cell proliferations with a wide clinical and prognostic spectrum, characterized by the production of monoclonal immunoglobulin by immortalized plasma cells. Recent years have seen an explosion in knowledge on the genetic basis and biology of these diseases, followed by improved clinical risk stratification and the introduction of novel therapeutic concepts, such as treatment with proteasome inhibitors or immunomodulatory substances. PCM is a common malignancy, accounting for approximately 10% of all hematological neoplasms. There is good evidence to support a multistep transformation process in plasma cell neoplasms, which corresponds to clinically discernible disease stages. Monoclonal gammopathy of unknown significance is a common asymptomatic precursor lesion for PCM which carries an approximately 1% annual risk for progression. Terminal disease stages are characterized by increasing genetic complexity and independence from bone marrow stromal cells and show a rapidly increasing tumour load with severe clinical symptoms. Modern diagnostics of plasma cell neoplasms require inclusion of clinical, morphological, immunophenotypical and cytogenetic features to allow for individual risk assessment and therapy planning.

DNA methylation analysis determines the high frequency of genic hypomethylation and low frequency of hypermethylation events in plasma cell tumors

Multiple myeloma (MM) is a plasma cell malignancy of the bone marrow, which evolves from a premalignant stage called monoclonal gammopathy of undetermined significance (MGUS). In some patients, an intermediate stage referred to as smoldering multiple myeloma (SMM) is clinically recognized, with the full-bore malignancy termed MM. We conducted a study to assess differential CpG methylation at 1,500 genic loci during MM progression and profiled CD138(+) plasma cells from MGUS, SMM, and MM specimens; human myeloma cell lines; and normal plasma cell (NPC) samples. We showed that the number of differentially methylated loci (DML) increased with tumor grade, and the vast majority were due to hypomethylation. Hierarchical clustering analysis revealed samples that coclustered tightly with NPC. These cases, referred to as "normal-like," contained significantly fewer DML when compared with their non-normal-like counterparts and displayed overall methylation levels resembling NPC. This study represents one of the first methylome interrogation studies in MM and points toward global hypomethylation at genic CpG loci as an important and early mechanism driving myelomagenesis. Determining the set of critical genes and pathways based on the myeloma methylome is expected to lead to an improved understanding of biological mechanisms involved in myelomagenesis.

Aggressive lymphomas

Genomewide molecular profiling has revealed new subtypes of lymphoma that originate from lymphocytes that differ in developmental stage and that use distinct oncogenic programs, yet are indistinguishable under the microscope. In this review, we discuss recent progress in the molecular genetics of aggressive lymphomas and focus on the most common form of this disease, diffuse large-B-cell lymphoma, which accounts for 30 to 40% of newly diagnosed lymphomas.

Ectopic expression of wild-type FGFR3 cooperates with MYC to accelerate development of B-cell lineage neoplasms

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 Emu 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 overexpressed 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.

Applying mass spectrometry based proteomic technology to advance the understanding of multiple myeloma

Multiple myeloma (MM) is the second most common hematological malignancy in adults. It is characterized by clonal proliferation of terminally differentiated B lymphocytes and over-production of monoclonal immunoglobulins. Recurrent genomic aberrations have been identified to contribute to the aggressiveness of this cancer. Despite a wealth of knowledge describing the molecular biology of MM as well as significant advances in therapeutics, this disease remains fatal. The identification of biomarkers, especially through the use of mass spectrometry, however, holds great promise to increasing our understanding of this disease. In particular, novel biomarkers will help in the diagnosis, prognosis and therapeutic stratification of MM. To date, results from mass spectrometry studies of MM have provided valuable information with regards to MM diagnosis and response to therapy. In addition, mass spectrometry was employed to study relevant signaling pathways activated in MM. This review will focus on how mass spectrometry has been applied to increase our understanding of MM.

Combination of novel proteasome inhibitor NPI-0052 and lenalidomide trigger in vitro and in vivo synergistic cytotoxicity in multiple myeloma

Our recent study demonstrated that a novel proteasome inhibitor NPI-0052 is distinct from bortezomib (Velcade) and, importantly, triggers apoptosis in multiple myeloma (MM) cells resistant to bortezomib. Here we demonstrate that combining NPI-0052 and lenalidomide (Revlimid) induces synergistic anti-MM activity in vitro using MM-cell lines or patient MM cells. NPI-0052 plus lenalidomide-induced apoptosis is associated with (1) activation of caspase-8, caspase-9, caspase-12, caspase-3, and poly(ADP) ribose polymerase; (2) activation of BH-3 protein BIM; (3) translocation of BIM to endoplasmic reticulum; (4) inhibition of migration of MM cells and angiogenesis; and (5) suppression of chymotrypsin-like, caspase-like, and trypsin-like proteasome activities. Importantly, blockade of BIM using siRNA significantly abrogates NPI-0052 plus lenalidomide-induced apoptosis. Furthermore, studies using biochemical inhibitors of caspase-8 versus caspase-9 demonstrate that NPI-0052 plus lenalidomide-triggered apoptosis is primarily dependent on caspase-8 signaling. In animal tumor model studies, low-dose combination of NPI-0052 and lenalidomide is well tolerated, significantly inhibits tumor growth, and prolongs survival. Taken together, our study provides the preclinical rationale for clinical protocols evaluating lenalidomide together with NPI-0052 to improve patient outcome in MM.

Control of apoptosis in human multiple myeloma by insulin-like growth factor I (IGF-I)

Human multiple myeloma (MM) is characterized by the expansion of neoplastic plasmablasts/plasma cells with complex genetic aberrations and high dependence for survival and growth on cytokines produced in the bone marrow microenvironment. As tools in the study of MM about 80 authentic MM cell lines and a few relevant in vivo mouse models are available. The dependence on insulin-like growth factor receptor (IGF-IR) signaling in the development and maintenance of the malignant phenotype in a variety of cancers is a rationale for attempts to improve tumor treatment by selectively inhibiting the IGF-IR in malignant cells by neutralizing antibodies, dominant negative IGF-IR, and IGF-IR siRNA. Testing the hypothesis that abrogating IGF-IR-mediated signaling of survival should make MM cells more susceptible to apoptosis, our studies have so far provided proof-of-principle by the demonstration that inhibition of a signaling pathway stimulating survival renders cells susceptible to drug-induced apoptosis when the drug (dexamethasone) and inhibitor (rapamycin) converge on the same target, that is p70(S6K). The recent publication of the three-dimensional structure of the IGF-IR kinase domain has facilitated the development of IGF-IR inhibitors of the cyclolignan family, that is picropodophyllin, with capacity to distinguish also in vivo between the IGF-IR and the insulin receptor. Studies in vitro and in vivo with picropodophyllin show promising effects, that is apoptosis induction and growth arrest, and have made it possible to evaluate the biological and therapeutic effects of inhibition of the IGF-IR signaling in MM.

Bone marrow large B cell lymphoma bearing cyclin D3 expression: clinical, morphologic, immunophenotypic, and genotypic analyses of seven patients

We report seven large B cell lymphoma patients showing the involvement of tumor cells with cyclin D3 (CCND3) expression in bone marrow (BM) at the initial diagnosis. All patients presented with B symptoms, splenomegaly, and anemia/thrombocytopenia lacking hemophagocytosis in the BM. Five of the seven patients had suffered from immunological diseases or cancers. The tumor cells were divided into those with a lymphoplasmacytoid or blastoid appearance. Six cases were confirmed to express CD5 antigen on tumor cells. Three cases presented a chromosomal translocation between CCND3 and the immunoglobulin heavy chain (IGH) loci, t(6;14)(p21;q32). Three and two cases showed unmutated and mutated sequences of the variable region of IGH (VH), respectively, and one case showed deletion of an entire segment of VH. Two cases with t(6;14)(p21;q32) showed an unmutated VH sequence and chromosomal translocation within the switch region of IGH. Further studies are required to determine whether CCND3 expression is associated with a unique subset of diffuse large B cell lymphoma.

OH-2, a hyperdiploid myeloma cell line without an IGH translocation, has a complex translocation juxtaposing MYC near MAFB and the IGK locus

Multiple myeloma can be classified into hyperdiploid (HRD) (with 48-74 chromosomes) and non-hyperdiploid tumors (usually with immunoglobulin heavy chain translocations). The OH-2 human myeloma cell line (HMCL) retains the same HRD genotype as the primary tumor, with extra copies of chromosomes 3, 7, 15, 19, and 21. Both OH-2 and primary cells have a complex secondary translocation in which the IGK 3' enhancer is inserted between MYC and MAFB, resulting in dysregulation of both oncogenes. OH-2 provides a unique example of an HMCL and the corresponding primary tumor that are shown to share the same HRD genotype.

Dysfunctional homologous recombination mediates genomic instability and progression in myeloma

A prominent feature of most if not all cancers is a striking genetic instability, leading to ongoing accrual of mutational changes, some of which underlie tumor progression, including acquisition of invasiveness, drug resistance, and metastasis. Thus, the molecular basis for the generation of this genetic diversity in cancer cells has important implications in understanding cancer progression. Here we report that homologous recombination (HR) activity is elevated in multiple myeloma (MM) cells and leads to an increased rate of mutation and progressive accumulation of genetic variation over time. We demonstrate that the inhibition of HR activity in MM cells by small inhibitory RNA (siRNAs) targeting recombinase leads to significant reduction in the acquisition of new genetic changes in the genome and, conversely, the induction of HR activity leads to significant elevation in the number of new mutations over time and development of drug resistance in MM cells. These data identify dysregulated HR activity as a key mediator of DNA instability and progression of MM, with potential as a therapeutic target.

Deregulation of c-Myc Confers distinct survival requirements for memory B cells, plasma cells, and their progenitors

Deregulation of the c-Myc oncogene is tightly associated with human and murine plasma cell (PC) neoplasms. Through the analysis of Ag-specific B cell responses in mice where Myc is targeted to the Igh Calpha locus, we show here that c-Myc dramatically impairs the primary and secondary Ab response. This impairment is differentiation stage specific, since germinal center B cell formation, affinity maturation, and class switch recombination were intact. Examination of PC viability revealed that c-Myc triggered apoptosis only upon final maturation when Ab is secreted and is resistant to the survival factor BAFF (B cell-activating factor belonging to the TNF family). In contrast, PC precursors (PC(pre)) that ultimately give rise to mature PCs survived normally and vigorously expanded with BAFF signaling. We further show that c-Myc also facilitates the apoptosis of memory B cells. Thus, Calpha-Myc controls both cellular arms of long-lived B cell immunity than previously anticipated. Only when deregulation of c-Myc was combined with enforced Bcl-x(L) expression were mature PCs able to survive in response to BAFF. These data indicate that the survival requirements for tumor-susceptible PC(pre) and PCs are distinct and that tumor progression likely develops as PC(pre) transition to functional PCs when apoptotic pathways such as members of the Bcl-2 family are disabled.

A der(8)t(8;11) chromosome in the Karpas-620 myeloma cell line expresses only cyclin D1: yet both cyclin D1 and MYC are repositioned in close proximity to the 3'IGH enhancer

The Karpas-620 human myeloma cell line (HMCL) expresses high levels of Cyclin D1 (CCND1), but has a der(8)t(8;11) and a der(14)t(8;14), and not a conventional t(11;14). Fluorescent in situ hybridization (FISH) and array comparative genomic hybridization (aCGH) studies suggest that der(14)t(11;14) from a primary translocation underwent a secondary translocation with chromosome 8 to generate der(8)t(8;[14];11) and der(14)t(8;[11];14). Both secondary derivatives share extensive identical sequences from chromosomes 8, 11, and 14, including MYC and the 3' IgH enhancers. Der(14), with MYC located approximately 700 kb telomeric to the 3'IGH enhancer, expresses MYC. By contrast, der(8), with both CCND1 and MYC repositioned near a 3'IGH enhancer, expresses CCND1, which is telomeric of the enhancer, but not MYC, which is centromeric to the enhancer. The secondary translocation that dysregulated MYC resulted in extensive regions from both donor chromosomes being transmitted to both derivative chromosomes, suggesting a defect in DNA recombination or repair in the myeloma tumor cell.

Establishment of CD5 and CD10 double-positive mature B-cell line, WILL1, showing complex 8q24 translocation involving 14q32 and 6q27

We established a novel mature B-cell line from a CD5 and CD10 double-positive diffuse large B-cell lymphoma patient, designated as WILL1. WILL1 cells were positive for CD5, CD10, CD19, and CD20. Spectral karyotype (SKY) analysis revealed chromosome 8 signals on 6q27 as well as 14q32. Fluorescence in situ hybridization (FISH) analysis suggested that a translocation break occurred outside the immunoglobulin heavy chain (IGH) gene on 14q32. Moreover, fusion signals of IGH and C-MYC probes were detected on the derivative 6 and derivative 14 chromosomes. Southern blot analysis using a C-MYC exon II fragment failed to detect rearrangement, suggesting that the 8q24 breakpoints lay far up- or downstream of the C-MYC gene. WILL1 is a useful tool to analyze the pathogenesis of CD5 and CD10 double-positive diffuse large B-cell lymphoma, and for molecular cloning of the unique translocation breakpoints of 14q32 and 8q24 and a novel gene on 6q27.

Structure and consequences of IGH switch breakpoints in Burkitt lymphoma

The t(8;14) MYC/IGH breakpoint is the hallmark translocation of human Burkitt lymphoma (BL). The translocation breakpoint most often involves the immunoglobulin heavy-chain switch regions and is thought to be brought about by an aberrant class switch recombination (CSR) event. During CSR in normal germinal center B cells, DNA double-stranded breaks are introduced in Smu and one of the downstream switch regions (Sgamma, Salpha, or Sepsilon) that are juxtaposed and ligated to form the switch junction, with deletion of the intervening DNA. In contrast, aberrant switch recombination in BL exclusively involves only one switch region, resulting in a perfect reciprocal translocation. A functional consequence of this type of translocation is that IgM expression from the chromosome affected by the translocation is not necessarily disrupted.

IRF4 addiction in multiple myeloma

The transcription factor IRF4 (interferon regulatory factor 4) is required during an immune response for lymphocyte activation and the generation of immunoglobulin-secreting plasma cells. Multiple myeloma, a malignancy of plasma cells, has a complex molecular aetiology with several subgroups defined by gene expression profiling and recurrent chromosomal translocations. Moreover, the malignant clone can sustain multiple oncogenic lesions, accumulating genetic damage as the disease progresses. Current therapies for myeloma can extend survival but are not curative. Hence, new therapeutic strategies are needed that target molecular pathways shared by all subtypes of myeloma. Here we show, using a loss-of-function, RNA-interference-based genetic screen, that IRF4 inhibition is 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. Although IRF4 is not genetically altered in most myelomas, they are nonetheless addicted to an aberrant IRF4 regulatory network that fuses the gene expression programmes of normal plasma cells and activated B cells.

Role of genetics in prognostication in myeloma

As in other hematological malignancies, cytogenetics is becoming a major prognostic parameter in myeloma. Myeloma differs from other hemopathies particularly in technical aspects related to low proliferation and partial infiltrates. Thus, fluorescence in-situ hybridization (FISH) is probably the best method for cytogenetic assessment in myeloma, but it requires the identification of the malignant cells (morphologically, immunologically or through sorting). Several chromosomal abnormalities have been identified. Among them, the t(4;14) and t(14;16) translocations and the del(17p) are the most important for outcome prediction, all of them predicting a short overall survival. However, even in these genetically defined subgroups, an outcome heterogeneity is observed, suggesting the role of other factors (genetic or otherwise) in disease evolution.

The MMSET protein is a histone methyltransferase with characteristics of a transcriptional corepressor

MMSET, identified by its fusion to the IgH locus in t(4;14)-associated multiple myeloma, possesses domains found within chromatin regulators, including the SET domain. MMSET protein is overexpressed and highly associated with chromatin in myeloma cell lines carrying t(4;14). MMSET possesses methyltransferase activity for core histone H3 lysine 4 and histone 4 lysine 20, whereas MMSET made in cells only modified H4. Segments of MMSET fused to the Gal4 DNA binding domain repressed transcription of a chromatin-embedded Gal4 reporter gene. MMSET-mediated repression was associated with increased H4K20 methylation gene and loss of histone acetylation. Consistent with this repressive activity, MMSET could form a complex with HDAC1 and HDAC2, mSin3a, and the histone demethylase LSD1, suggesting that it is a component of corepressor complexes. Furthermore, MMSET coexpression enhances HDAC1- and HDAC2-mediated repression in transcriptional reporter assays. Finally, shRNA-mediated knockdown of MMSET compromised viability of a myeloma cell line, suggesting a biologic role for the protein in malignant cell growth. Collectively, these data suggest that, by acting directly as a modifier of chromatin as well as through binding of other chromatin-modifying enzymes, MMSET influences gene expression and potentially acts as a pathogenic agent in multiple myeloma.

Translocation t(6;14) as the sole chromosomal abnormality in adenoid cystic carcinoma of the base of tongue

We present an adenoid cystic carcinoma of the base of tongue in a 48-year-old male with a restricted chromosomal alteration by cytogenetic and spectral karyotypic analysis (SKY). SKY and G-banding analyses identified the t(6;14)(q25;q13) as the sole structural aberration in all metaphases analyzed. This finding supports a critical role for this event in the development of this tumor. The implications of chromosome 6q translocation in this case and in previously reported adenoid cystic carcinomas are highlighted and discussed.