Ectopic expression of MAFB gene in human myeloma cells carrying (14;20)(q32;q11) chromosomal translocations

ARK5 enhances cell survival associated with mitochondrial morphological dynamics from fusion to fission in human multiple myeloma cells

5' adenosine monophosphate-activated protein kinase-related kinase 5 (ARK5) is involved in mitochondrial ATP production and associated with poor prognosis of multiple myeloma (MM). However, the molecular mechanisms of ARK5 in MM remain largely unknown. This study examined the pathogenic role of ARK5 in mitochondria by using genetically modified isogenic cell clones with or without ARK5 in human myeloma cell lines, KMS-11 and Sachi, which overexpress ARK5. The biallelic knockout of ARK5 (ARK5-KO) inhibited cell proliferation, colony formation, and migration with increased apoptosis. Mitochondrial fusion was enhanced in ARK5-KO cells, unlike in ARK5 wild-type (ARK5-WT) cells, which exhibited increased mitochondrial fission. Furthermore, ARK5-KO cells demonstrated a lower phosphorylated dynamin-related protein 1 at serine 616, higher protein expression of mitofusin-1 (MFN1) and MFN2, optic atrophy 1 with a lower level of ATP, and higher levels of lactate and reactive oxygen species than ARK5-WT cells. Our findings suggest that ARK5-enhanced myeloma cells can survive associated mitochondrial fission and activity. This study first revealed the relationship between ARK5 and mitochondrial morphological dynamics. Thus, our outcomes show novel aspects of mitochondrial biology of ARK5, which can afford a more advanced treatment approach for unfavorable MM expressing ARK5.

Hypoxia-induced oxidative stress promotes therapy resistance via upregulation of heme oxygenase-1 in multiple myeloma

BACKGROUND

Multiple myeloma (MM) is a hematopoietic malignancy for which proteasome inhibitors have become available in recent years. However, many patients develop resistance to these drugs during treatment. Therefore, it is important to elucidate the mechanisms underlying resistance acquisition by proteasome inhibitors. Side population (SP) cells, which have a high drug efflux capacity and hypoxic responses in the microenvironment have both provided important insights into drug resistance in MM; however, little is known about the characteristics of SP cells in hypoxic microenvironments.

METHODS

We performed cDNA microarray analysis for SP and non-SP obtained from RPMI-8226 and KMS-11 cell lines cultured for 48 h in normoxic and hypoxic conditions (1% O₂ ). Genes specifically upregulated in hypoxic SP were examined.

RESULTS

Our comprehensive gene expression analysis identified HMOX1, BACH2, and DUX4 as protein-coding genes that are specifically highly expressed in SP cells under hypoxic conditions. We have shown that HMOX1/heme oxygenase-1 (HMOX1/HO-1) is induced by hypoxia-inducible reactive oxygen species (ROS) and reduces ROS levels. Furthermore, we found that HMOX1 contributes to hypoxia-induced resistance to proteasome inhibitors in vitro and in vivo. Excessive ROS levels synergistically enhance bortezomib sensitivity. In clinical datasets, HMOX1 had a strong and significantly positive correlation with MAFB but not MAF. Interestingly, hypoxic stimulation increased MAFB/MafB expression in myeloma cells; in addition, the knockdown of MAFB under hypoxic conditions suppressed HMOX1 expression.

CONCLUSION

These results suggest that the hypoxia-ROS-HMOX1 axis and hypoxia-induced MafB may be important mechanisms of proteasome inhibitor resistance in hypoxic microenvironments.

The role and regulation of Maf proteins in cancer

The Maf proteins (Mafs) belong to basic leucine zipper transcription factors and are members of the activator protein-1 (AP-1) superfamily. There are two subgroups of Mafs: large Mafs and small Mafs, which are involved in a wide range of biological processes, such as the cell cycle, proliferation, oxidative stress, and inflammation. Therefore, dysregulation of Mafs can affect cell fate and is closely associated with diverse diseases. Accumulating evidence has established both large and small Mafs as mediators of tumor development. In this review, we first briefly describe the structure and physiological functions of Mafs. Then we summarize the upstream regulatory mechanisms that control the expression and activity of Mafs. Furthermore, we discuss recent studies on the critical role of Mafs in cancer progression, including cancer proliferation, apoptosis, metastasis, tumor/stroma interaction and angiogenesis. We also review the clinical implications of Mafs, namely their potential possibilities and limitations as biomarkers and therapeutic targets in cancer.

Macrophage-Specific, Mafb-Deficient Mice Showed Delayed Skin Wound Healing

Macrophages play essential roles throughout the wound repair process. Nevertheless, mechanisms regulating the process are poorly understood. MAFB is specifically expressed in the macrophages in hematopoietic tissue and is vital to homeostatic function. Comparison of the skin wound repair rates in macrophage-specific, MAFB-deficient mice (Mafb^f/f::LysM-Cre) and control mice (Mafb^f/f) showed that wound healing was significantly delayed in the former. For wounded GFP knock-in mice with GFP inserts in the Mafb locus, flow cytometry revealed that their GFP-positive cells expressed macrophage markers. Thus, macrophages express Mafb at wound sites. Immunohistochemical (IHC) staining, proteome analysis, and RT-qPCR of the wound tissue showed relative downregulation of Arg1, Ccl12, and Ccl2 in Mafb^f/f::LysM-Cre mice. The aforementioned genes were also downregulated in the bone marrow-derived, M2-type macrophages of Mafb^f/f::LysM-Cre mice. Published single-cell RNA-Seq analyses showed that Arg1, Ccl2, Ccl12, and Il-10 were expressed in distinct populations of MAFB-expressing cells. Hence, the MAFB-expressing macrophage population is heterogeneous. MAFB plays the vital role of regulating multiple genes implicated in wound healing, which suggests that MAFB is a potential therapeutic target in wound healing.

Increasing genomic discovery in newly diagnosed multiple myeloma: defining disease biology and its correlation to risk

Our understanding of MM genomics has expanded rapidly in the past 5-10 years as a consequence of cytogenetic analyses obtained in routine clinical practice as well as the ability to perform whole-exome/genome sequencing and gene expression profiling on large patient data sets. This knowledge has offered new insights into disease biology and is increasingly defining high-risk genomic patterns. In this manuscript, we present a thorough review of our current knowledge of MM genomics. The epidemiology and biology of chromosomal abnormalities including both copy number abnormalities and chromosomal translocation are described in full with a focus on those most clinically impactful such as 1q amplification and del(17p) as well as certain chromosome 14 translocations. A review of our ever-expanding knowledge of genetic mutations derived from recent whole-genome/exome data sets is then reviewed including those that drive disease pathogenesis from precursor states as well as those that may impact clinical outcomes. We then transition and attempt to elucidate how both chromosomal abnormalities and gene mutations are evolving our understanding of disease risk. We conclude by offering our perspectives moving forward as to how we might apply whole-genome/exome-level data in addition to routine cytogenetic analyses to improve patient outcomes as well as further knowledge gaps that must be addressed.

Review of Multiple Myeloma Genetics including Effects on Prognosis, Response to Treatment, and Diagnostic Workup

Multiple myeloma is a disorder of the monoclonal plasma cells and is the second most common hematologic malignancy. Despite improvements in survival with newer treatment regimens, multiple myeloma remains an incurable disease and most patients experience multiple relapses. Multiple myeloma disease initiation and progression are highly dependent on complex genetic aberrations. This review will summarize the current knowledge of these genetic aberrations, how they affect prognosis and the response to treatment, and review sensitive molecular techniques for multiple myeloma workup, with the ultimate goal of detecting myeloma progression early, allowing for timely treatment initiation.

Multiple myeloma with high-risk cytogenetics and its treatment approach

Despite substantial advances in anti-myeloma treatments, early recurrence and death remain an issue in certain subpopulations. Cytogenetic abnormalities (CAs) are the most widely accepted predictors for poor prognosis in multiple myeloma (MM), such as t(4;14), t(14;16), t(14;20), gain/amp(1q21), del(1p), and del(17p). Co-existing high-risk CAs (HRCAs) tend to be associated with an even worse prognosis. Achievement of sustained minimal residual disease (MRD)-negativity has recently emerged as a surrogate for longer survival, regardless of cytogenetic risk. Information from newer clinical trials suggests that extended intensified treatment can help achieve MRD-negativity in patients with HRCAs, which may lead to improved outcomes. Therapy should be considered to include a 3- or 4-drug induction regimen (PI/IMiD/Dex or PI/IMiD/Dex/anti-CD38 antibody), auto-transplantation, and consolidation/maintenance with lenalidomide ± a PI. Results from ongoing clinical trials for enriched high-risk populations will reveal the precise efficacy of the investigated regimens. Genetic abnormalities of MM cells are intrinsic critical factors determining tumor characteristics, which reflect the natural course and drug sensitivity of the disease. This paper reviews the clinicopathological features of genomic abnormalities related to adverse prognosis, focusing on HRCAs that are the most relevant in clinical practice, and outline current optimal therapeutic approaches for newly diagnosed MM with HRCAs.

Multiple Myeloma: Molecular Pathogenesis and Disease Evolution

BACKGROUND

Multiple myeloma is the second most common hematologic malignancy, which to date remains incurable despite advances in treatment strategies including the use of novel substances such as proteasome inhibitors, immunomodulatory drugs, and monoclonal antibodies.

SUMMARY

The bone marrow-based disease is preceded by the 2 sequential premalignant conditions: monoclonal gammo-pathy of undetermined significance and smoldering myeloma. Plasma cell leukemia and extramedullary disease occur, when malignant clones lose their dependency on the bone marrow. Key genetic features of these plasma cell dyscrasias include chromosomal aberrations such as translocations and hyperdiploidy, which occur during error-prone physiologic processes in B-cell development. Next-generation sequencing studies have identified mutations in major oncogenic pathways and tumor suppressors, which contribute to the pathogenesis of multiple myeloma and have revealed insights into the clonal evolution of the disease, particularly along different lines of therapy. More recently, the importance of epigenetic alterations and the role of the bone marrow microenvironment, including immune and osteogenic cells, have become evident. Key Messages: We herein review the current knowledge of the pathogenesis of multiple myeloma, which is crucial for the development of novel targeted therapeutic strategies. These can contribute to the endeavor to make multiple myeloma a curable disease.

Synergistic Effects of Venetoclax and Daratumumab on Antibody-Dependent Cell-Mediated Natural Killer Cytotoxicity in Multiple Myeloma

The prognosis of multiple myeloma (MM) has drastically improved owing to the development of new drugs, such as proteasome inhibitors and immunomodulatory drugs. Nevertheless, MM is an extremely challenging disease, and many patients are still refractory to the existing therapies, thus requiring new treatment alternatives. Venetoclax is a selective, orally bioavailable inhibitor of BCL-2 that shows efficacy in MM not only as a single agent but also in combination therapy, especially for MM patients with translocation t(11;14). However, many patients are refractory to this drug. Here, we treated the MM cell lines KMS12PE and KMS27 with a combination treatment of venetoclax targeting BCL-2 and daratumumab targeting CD38 to evaluate the synergistic cytotoxicity of these drugs in vitro. MM cell lines were co-cultured with natural killer (NK) cells at an effector:target ratio of 0.3:1 in the presence of serial concentrations of daratumumab and venetoclax, and the resulting apoptotic MM cells were detected by flow cytometry using annexin V. These results indicated that the antibody-dependent cell-mediated NK cytotoxicity was enhanced in KMS12PE and KMS27 cells harboring t(11;14) with a high BCL-2 expression, suggesting that the combination treatment of venetoclax and daratumumab should be especially effective in patients with these characteristics.

Genetic Predictors of Mortality in Patients with Multiple Myeloma

Multiple myeloma (MM) is a heterogeneous disease featured by clonal plasma cell proliferation and genomic instability. The advent of next-generation sequencing allowed unraveling the complex genomic landscape of the disease. Several recurrent genomic aberrations including immunoglobulin genes translocations, copy number abnormalities, complex chromosomal events, transcriptomic and epigenomic deregulation, and mutations define various molecular subgroups with distinct outcomes. In this review, we describe the recurrent genomic events identified in MM impacting patients’ outcome and survival. These genomic aberrations constitute new markers that could be incorporated into a prognostication model to eventually guide therapy at every stage of the disease.

Functional analysis of large MAF transcription factors and elucidation of their relationships with human diseases

The large MAF transcription factor group is a group of transcription factors with an acidic region, a basic region, and a leucine zipper region. Four types of MAF, MAFA, MAFB, c-MAF, and NRL, have been identified in humans and mice. In order to elucidate the functions of the large MAF transcription factor group in vivo, our research group created genetically modified MAFA-, MAFB-, and c-MAF-deficient mice and analyzed their phenotypes. MAFA is expressed in pancreatic β cells and is essential for insulin transcription and secretion. MAFB is essential for the development of pancreatic endocrine cells, formation of inner ears, podocyte function in the kidneys, and functional differentiation of macrophages. c-MAF is essential for lens formation and osteoblast differentiation. Furthermore, a single-base mutation in genes encoding the large MAF transcription factor group causes congenital renal disease, eye disease, bone disease, diabetes, and tumors in humans. This review describes the functions of large MAF transcription factors in vivo and their relationships with human diseases.

Gain/Amplification of Chromosome Arm 1q21 in Multiple Myeloma

Simple Summary

Multiple myeloma (MM), a plasma cell neoplasm, is an incurable hematological malignancy. Gain/amplification of chromosome arm 1q21 (1q21+) is the most common adverse genomic abnormality associated with disease progression and drug resistance. While possible mechanisms of 1q21+ occurrence and candidate genes in the 1q21 amplicon have been suggested, the precise pathogenesis of MM with 1q21+ is unknown. Herein, we review the current knowledge about the clinicopathological features of 1q21+ MM, which can assist in effective therapeutic approaches for MM patients with 1q21+.

Abstract

Multiple myeloma (MM), a plasma cell neoplasm, is an incurable hematological malignancy characterized by complex genetic and prognostic heterogeneity. Gain or amplification of chromosome arm 1q21 (1q21+) is the most frequent adverse chromosomal aberration in MM, occurring in 40% of patients at diagnosis. It occurs in a subclone of the tumor as a secondary genomic event and is more amplified as the tumor progresses and a risk factor for the progression from smoldering multiple myeloma to MM. It can be divided into either 1q21 gain (3 copies) or 1q21 amplification (≥4 copies), and it has been suggested that the prognosis is worse in cases of amplification than gain. Trisomy of chromosome 1, jumping whole-arm translocations of chromosome1q, and tandem duplications lead to 1q21+ suggesting that its occurrence is not consistent at the genomic level. Many studies have reported that genes associated with the malignant phenotype of MM are situated on the 1q21 amplicon, including CKS1B, PSMD4, MCL1, ANP32E, and others. In this paper, we review the current knowledge regarding the clinical features, prognostic implications, and the speculated pathology of 1q21+ in MM, which can provide clues for an effective treatment approach to MM patients with 1q21+.

Multiple Myeloma: Available Therapies and Causes of Drug Resistance

Multiple myeloma (MM) is the second most common blood cancer. Treatments for MM include corticosteroids, alkylating agents, anthracyclines, proteasome inhibitors, immunomodulatory drugs, histone deacetylase inhibitors and monoclonal antibodies. Survival outcomes have improved substantially due to the introduction of many of these drugs allied with their rational use. Nonetheless, MM patients successively relapse after one or more treatment regimens or become refractory, mostly due to drug resistance. This review focuses on the main drugs used in MM treatment and on causes of drug resistance, including cytogenetic, genetic and epigenetic alterations, abnormal drug transport and metabolism, dysregulation of apoptosis, autophagy activation and other intracellular signaling pathways, the presence of cancer stem cells, and the tumor microenvironment. Furthermore, we highlight the areas that need to be further clarified in an attempt to identify novel therapeutic targets to counteract drug resistance in MM patients.

Plasma cell myeloma positive for t(14;20) with relapse in the central nervous system

t(14;20)(q32;q11)/IGH-MAFB is a rare chromosomal abnormality in plasma cell myeloma (PCM), accounting for 1-2% of PCM cases. Patients with this translocation may have a poor prognosis. However, the clinicopathological features and response to novel agents have not been well clarified. We present a 63-year-old Japanese female with PCM positive for t(14;20). The tumor responded well to a proteasome inhibitor, bortezomib, and the patient achieved complete remission. Six months after remission, tumor relapse was noted in the left cerebellum and the right frontal lobe of the cerebrum. After whole brain radiation therapy, the tumor masses decreased in size. The patient was followed up with best-care support, but died of the disease 29 months after the initial PCM diagnosis. t(14;20)-positive PCM responded well to bortezomib at the time of the initial treatment. The CNS tumor involvement, which is rare in PCM, may be associated with the clinical aggressiveness of the t(14;20)-positive form of this myeloma.

Cell of Origin and Genetic Alterations in the Pathogenesis of Multiple Myeloma

B cell activation and differentiation yields plasma cells with high affinity antibodies to a given antigen in a time-frame that allows for host protection. Although the end product is most commonly humoral immunity, the rapid proliferation and somatic mutation of the B cell receptor also results in oncogenic mutations that cause B cell malignancies including plasma cell neoplasms such as multiple myeloma. Myeloma is the second most common hematological malignancy and results in over 100,000 deaths per year worldwide. The genetic alterations that occur in the germinal center, however, are not sufficient to cause myeloma, but rather impart cell proliferation potential on plasma cells, which are normally non-dividing. This pre-malignant state, referred to as monoclonal gammopathy of undetermined significance or MGUS, provides the opportunity for further genetic and epigenetic alterations eventually resulting in a progressive disease that becomes symptomatic. In this review, we will provide a brief history of clonal gammopathies and detail how some of the key discoveries were interwoven with the study of plasma cells. We will also review the genetic and epigenetic alterations discovered over the past 25 years, how these are instrumental to myeloma pathogenesis, and what these events teach us about myeloma and plasma cell biology. These data will be placed in the context of normal B cell development and differentiation and we will discuss how understanding the biology of plasma cells can lead to more effective therapies targeting multiple myeloma.

Germline Risk Contribution to Genomic Instability in Multiple Myeloma

Genomic instability, a well-established hallmark of human cancer, is also a driving force in the natural history of multiple myeloma (MM) - a difficult to treat and in most cases fatal neoplasm of immunoglobulin producing plasma cells that reside in the hematopoietic bone marrow. Long recognized manifestations of genomic instability in myeloma at the cytogenetic level include abnormal chromosome numbers (aneuploidy) caused by trisomy of odd-numbered chromosomes; recurrent oncogene-activating chromosomal translocations that involve immunoglobulin loci; and large-scale amplifications, inversions, and insertions/deletions (indels) of genetic material. Catastrophic genetic rearrangements that either shatter and illegitimately reassemble a single chromosome (chromotripsis) or lead to disordered segmental rearrangements of multiple chromosomes (chromoplexy) also occur. Genomic instability at the nucleotide level results in base substitution mutations and small indels that affect both the coding and non-coding genome. Sometimes this generates a distinctive signature of somatic mutations that can be attributed to defects in DNA repair pathways, the DNA damage response (DDR) or aberrant activity of mutator genes including members of the APOBEC family. In addition to myeloma development and progression, genomic instability promotes acquisition of drug resistance in patients with myeloma. Here we review recent findings on the genetic predisposition to myeloma, including newly identified candidate genes suggesting linkage of germline risk and compromised genomic stability control. The role of ethnic and familial risk factors for myeloma is highlighted. We address current research gaps that concern the lack of studies on the mechanism by which germline risk alleles promote genomic instability in myeloma, including the open question whether genetic modifiers of myeloma development act in tumor cells, the tumor microenvironment (TME), or in both. We conclude with a brief proposition for future research directions, which concentrate on the biological function of myeloma risk and genetic instability alleles, the potential links between the germline genome and somatic changes in myeloma, and the need to elucidate genetic modifiers in the TME.

MAFb protein confers intrinsic resistance to proteasome inhibitors in multiple myeloma

Background

Multiple myeloma (MM) patients with t(14;20) have a poor prognosis and their outcome has not improved following the introduction of bortezomib (Bzb). The mechanism underlying the resistance to proteasome inhibitors (PIs) for this subset of patients is unknown.

Methods

IC50 of Bzb and carfilzomib (CFZ) in human myeloma cell lines (HMCLs) were established by MTT assay. Gene Expression profile (GEP) analysis was used to determine gene expression in primary myeloma cells. Immunoblotting analysis was performed for MAFb and caspase family proteins. Immunofluorescence staining was used to detect the location of MAFb protein in MM cells. Lentiviral infections were used to knock-down MAFb expression in two lines. Apoptosis detection by flow cytometry and western blot analysis was performed to determine the molecular mechanism MAFb confers resistance to proteasome inhibitors.

Results

We found high levels of MAFb protein in cell lines with t(14;20), in one line with t(6;20), in one with Igλ insertion into MAFb locus, and in primary plasma cells from MM patients with t(14;20). High MAFb protein levels correlated with higher IC50s of PIs in MM cells. Inhibition of GSK3β activity or treatment with Bzb or CFZ prevented MAFb protein degradation without affecting the corresponding mRNA level indicating a role for GSK3 and proteasome inhibitors in regulation of MAFb stability. Silencing MAFb restored sensitivity to Bzb and CFZ, and enhanced PIs-induced apoptosis and activation of caspase-3, − 8, − 9, PARP and lamin A/C suggesting that high expression of MAFb protein leads to insensitivity to proteasome inhibitors.

Conclusion

These results highlight the role of post-translational modification of MAFb in maintaining its protein level, and identify a mechanism by which proteasome inhibitors induced stabilization of MAFb confers resistance to proteasome inhibitors, and provide a rationale for the development of targeted therapeutic strategies for this subset of patients.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4602-4) contains supplementary material, which is available to authorized users.

The NF-κB Activating Pathways in Multiple Myeloma

Multiple myeloma(MM), an incurable plasma cell cancer, represents the second most prevalent hematological malignancy. Deregulated activity of the nuclear factor kappaB (NF-κB) family of transcription factors has been implicated in the pathogenesis of multiple myeloma. Tumor microenvironment-derived cytokines and cancer-associated genetic mutations signal through the canonical as well as the non-canonical arms to activate the NF-κB system in myeloma cells. In fact, frequent engagement of both the NF-κB pathways constitutes a distinguishing characteristic of myeloma. In turn, NF-κB signaling promotes proliferation, survival and drug-resistance of myeloma cells. In this review article, we catalog NF-κB activating genetic mutations and microenvironmental cues associated with multiple myeloma. We then describe how the individual canonical and non-canonical pathways transduce signals and contribute towards NF-κB -driven gene-expressions in healthy and malignant cells. Furthermore, we discuss signaling crosstalk between concomitantly triggered NF-κB pathways, and its plausible implication for anomalous NF-κB activation and NF-κB driven pro-survival gene-expressions in multiple myeloma. Finally, we propose that mechanistic understanding of NF-κB deregulations may provide for improved therapeutic and prognostic tools in multiple myeloma.

SUMOylated MAFB promotes colorectal cancer tumorigenesis

The transcription factor, v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog B (MAFB), promotes tumorigenesis in some cancers. In this study, we found that MAFB levels were increased in clinical colorectal cancer (CRC) samples, and higher expression correlated with more advanced TNM stage. We identified MAFB amplifications in a majority of tumor types in an assessment of The Cancer Genome Atlas database. Altered MAFB levels due to gene amplification, deletion, mutation, or transcription upregulation occurred in 9% of CRC cases within the database. shRNA knockdown experiments demonstrated that MAFB deficiency blocked CRC cell proliferation by arresting the cell cycle at G0/G1 phase in vitro. We found that MAFB could be SUMOylated by SUMO1 at lysine 32, and this modification was critical for cell cycle regulation by MAFB in CRC cells. SUMOylated MAFB directly regulated cyclin-dependent kinase 6 transcription by binding to its promoter. MAFB knockdown CRC cell xenograft tumors in mice grew more slowly than controls, and wild-type MAFB-overexpressing tumors grew more quickly than tumors overexpressing MAFB mutated at lysine 32. These data suggest that SUMOylated MAFB promotes CRC tumorigenesis through cell cycle regulation. MAFB and its SUMOylation process may serve as novel therapeutic targets for CRC treatment.

MAFA missense mutation causes familial insulinomatosis and diabetes mellitus

We report a disease-causing mutation in the β-cell–enriched MAFA transcription factor. Strikingly, the missense p.Ser64Phe MAFA mutation was associated with either of two distinct phenotypes, multiple insulin-producing neuroendocrine tumors of the pancreas—a condition known as insulinomatosis—or diabetes mellitus, recapitulating the physiological properties of MAFA both as an oncogene and as a key islet β-cell transcription factor. The implication of MAFA in these human phenotypes will provide insights into how this transcription factor regulates human β-cell activity as well as into the mechanisms of Maf-induced tumorigenesis.

The β-cell–enriched MAFA transcription factor plays a central role in regulating glucose-stimulated insulin secretion while also demonstrating oncogenic transformation potential in vitro. No disease-causing MAFA variants have been previously described. We investigated a large pedigree with autosomal dominant inheritance of diabetes mellitus or insulinomatosis, an adult-onset condition of recurrent hyperinsulinemic hypoglycemia caused by multiple insulin-secreting neuroendocrine tumors of the pancreas. Using exome sequencing, we identified a missense MAFA mutation (p.Ser64Phe, c.191C>T) segregating with both phenotypes of insulinomatosis and diabetes. This mutation was also found in a second unrelated family with the same clinical phenotype, while no germline or somatic MAFA mutations were identified in nine patients with sporadic insulinomatosis. In the two families, insulinomatosis presented more frequently in females (eight females/two males) and diabetes more often in males (12 males/four females). Four patients from the index family, including two homozygotes, had a history of congenital cataract and/or glaucoma. The p.Ser64Phe mutation was found to impair phosphorylation within the transactivation domain of MAFA and profoundly increased MAFA protein stability under both high and low glucose concentrations in β-cell lines. In addition, the transactivation potential of p.Ser64Phe MAFA in β-cell lines was enhanced compared with wild-type MAFA. In summary, the p.Ser64Phe missense MAFA mutation leads to familial insulinomatosis or diabetes by impacting MAFA protein stability and transactivation ability. The human phenotypes associated with the p.Ser64Phe MAFA missense mutation reflect both the oncogenic capacity of MAFA and its key role in islet β-cell activity.

Transcription factor MafB may play an important role in secondary hyperparathyroidism

The transcription factor MafB is essential for development of the parathyroid glands, the expression of which persists after morphogenesis and in adult parathyroid glands. However, the function of MafB in adult parathyroid tissue is unclear. To investigate this, we induced chronic kidney disease (CKD) in wild-type and MafB heterozygote (MafB+/-) mice by feeding them an adenine-supplemented diet, leading to secondary hyperparathyroidism. The elevated serum creatinine and blood urea nitrogen levels in heterozygous and wild-type mice fed the adenine-supplemented diet were similar. Interestingly, secondary hyperparathyroidism, characterized by serum parathyroid hormone elevation and enlargement of parathyroid glands, was suppressed in MafB+/- mice fed the adenine-supplemented diet compared to similarly fed wild-type littermates. Quantitative RT-PCR and immunohistochemical analyses showed that the increased expression of parathyroid hormone and cyclin D2 in mice with CKD was suppressed in the parathyroid glands of heterozygous CKD mice. A reporter assay indicated that MafB directly regulated parathyroid hormone and cyclin D2 expression. To exclude an effect of a developmental anomaly in MafB+/- mice, we analyzed MafB tamoxifen-induced global knockout mice. Hypocalcemia-stimulated parathyroid hormone secretion was significantly impaired in MafB knockout mice. RNA-sequencing analysis indicated PTH, Gata3 and Gcm2 depletion in the parathyroid glands of MafB knockout mice. Thus, MafB appears to play an important role in secondary hyperparathyroidism by regulation of parathyroid hormone and cyclin D2 expression. Hence, MafB may represent a new therapeutic target in secondary hyperparathyroidism.

Proteome alterations associated with transformation of multiple myeloma to secondary plasma cell leukemia

Plasma cell leukemia is a rare and aggressive plasma cell neoplasm that may either originate de novo (primary PCL) or by leukemic transformation of multiple myeloma (MM) to secondary PCL (sPCL). The prognosis of sPCL is very poor, and currently no standard treatment is available due to lack of prospective clinical studies. In an attempt to elucidate factors contributing to transformation, we have performed super-SILAC quantitative proteome profiling of malignant plasma cells collected from the same patient at both the MM and sPCL stages of the disease. 795 proteins were found to be differentially expressed in the MM and sPCL samples. Gene ontology analysis indicated a metabolic shift towards aerobic glycolysis in sPCL as well as marked down-regulation of enzymes involved in glycan synthesis, potentially mediating altered glycosylation of surface receptors. There was no significant change in overall genomic 5-methylcytosine or 5-hydroxymethylcytosine at the two stages, indicating that epigenetic dysregulation was not a major driver of transformation to sPCL. The present study constitutes the first attempt to provide a comprehensive map of the altered protein expression profile accompanying transformation of MM to sPCL in a single patient, identifying several candidate proteins that can be targeted by currently available small molecule drugs. Our dataset furthermore constitutes a reference dataset for further proteomic analysis of sPCL transformation.

Genomics of Multiple Myeloma

Multiple myeloma (MM) is characterized by wide variability in the chromosomal/genetic changes present in tumor plasma cells. Genetically, MM can be divided into two groups according to ploidy and hyperdiploidy versus nonhyperdiploidy. Several studies in gene expression profiling attempted to identify subentities in MM without convincing results. These studies mostly confirmed the cytogenetic data and subclassified patients according to 14q32 translocations and ploidy. More-recent data that are based on whole-exome sequencing have confirmed this heterogeneity and show many gene mutations but without a unifying mutation. These newer studies have shown the frequent alteration of the mitogen-activated protein kinase pathway. The most interesting data have demonstrated subclonality in all patients with MM, including subclonal mutations of supposed driver genes KRAS, NRAS, and BRAF.

Genomic Aberrations in Multiple Myeloma

Multiple myeloma (MM) is a genetically complex disease. The past few years have seen an evolution in cancer research with the emergence of next-generation sequencing (NGS), enabling high throughput sequencing of tumors-including whole exome, whole genome, RNA, and single-cell sequencing as well as genome-wide association study (GWAS). A few inherited variants have been described, counting for some cases of familial disease. Hierarchically, primary events in MM can be divided into hyperdiploid (HDR) and nonhyperdiploid subtypes. HRD tumors are characterized by trisomy of chromosomes 3, 5, 7, 9, 11, 15, 19, and/or 21. Non-HRD tumors harbor IGH translocations, mainly t(4;14), t(6;14), t(11;14), t(14;16), and t(14;20). Secondary events participate to the tumor progression and consist in secondary translocation involving MYC, copy number variations (CNV) and somatic mutations (such as mutations in KRAS, NRAS, BRAF, P53). Moreover, the dissection of clonal heterogeneity helps to understand the evolution of the disease. The following review provides a comprehensive review of the genomic landscape in MM.

APOBEC family mutational signatures are associated with poor prognosis translocations in multiple myeloma

We have sequenced 463 presenting cases of myeloma entered into the UK Myeloma XI study using whole exome sequencing. Here we identify mutations induced as a consequence of misdirected AID in the partner oncogenes of IGH translocations, which are activating and associated with impaired clinical outcome. An APOBEC mutational signature is seen in 3.8% of cases and is linked to the translocation-mediated deregulation of MAF and MAFB, a known poor prognostic factor. Patients with this signature have an increased mutational load and a poor prognosis. Loss of MAF or MAFB expression results in decreased APOBEC3B and APOBEC4 expression, indicating a transcriptional control mechanism. Kataegis, a further mutational pattern associated with APOBEC deregulation, is seen at the sites of the MYC translocation. The APOBEC mutational signature seen in myeloma is, therefore, associated with poor prognosis primary and secondary translocations and the molecular mechanisms involved in generating them.

Role of additional chromosomal changes in the prognostic value of t(4;14) and del(17p) in multiple myeloma: the IFM experience

In multiple myeloma, cytogenetic changes are important predictors of patient outcome. In this setting, the most important changes are deletion 17p, del(17p), and translocation of chromosomes 4 and 14, t(4;14), conferring a poor outcome. However, a certain degree of heterogeneity is observed in the survival of these high-risk patients. We hypothesized that other chromosomal changes may impact the outcome. We retrospectively analyzed a large series of 242 patients displaying either t(4;14) (157 patients) or del(17p) (110 patients), 25 patients presenting both abnormalities, using single nucleotide polymorphism array. In patients with t(4;14), del(1p32), del22q, and >30 chromosomal structural changes negatively impacted progression-free survival (PFS). For overall survival (OS), del(13q14), del(1p32), and the number of chromosomal structural changes worsened the prognosis of patients. For patients with del(17p), del6q worsened the prognosis of patients, whereas trisomy 15 and monosomy 14 were found to have a protective effect on PFS. For OS, del(1p32) worsened the prognosis of patients, whereas having >8 numerical changes was found to have a protective effect on survival. This study, which is the largest series of high-risk patients analyzed with the most modern genomic technique, identified 1 main factor negatively impacting survival: del(1p32).

Genetics of multiple myeloma: another heterogeneity level?

Our knowledge of myeloma genetics remained limited and lagged behind many other hematologic malignancies because of the inherent difficulties in generating metaphases within the malignant plasma cell clone. With the development of molecular techniques (microarrays and next-generation sequencing), our understanding has been highly improved in the past 5 years. These studies have not only confirmed the prevalence of wide heterogeneity in myeloma at the molecular level, but has also provided a much clearer picture of the disease pathogenesis and progression. Whether these data will enable improvements in the therapeutic approach is still a matter of debate. The next improvement will come from detailed analyses of these molecular features to try to move from a treatment fitted to every patient to individualized therapies, taking into account the complexity of the chromosomal changes, the mutation spectrum, and subclonality evolution.

GSK3-mediated MAF phosphorylation in multiple myeloma as a potential therapeutic target

Multiple myeloma (MM) is an incurable haematological malignancy characterised by the proliferation of mature antibody-secreting plasma B cells in the bone marrow. MM can arise from initiating translocations, of which the musculoaponeurotic fibrosarcoma (MAF) family is implicated in ∼5%. MMs bearing Maf translocations are of poor prognosis. These translocations are associated with elevated Maf expression, including c-MAF, MAFB and MAFA, and with t(14;16) and t(14;20) translocations, involving c-MAF and MAFB, respectively. c-MAF is also overexpressed in MM through MEK/ERK activation, bringing the number of MMs driven by the deregulation of a Maf gene close to 50%. Here we demonstrate that MAFB and c-MAF are phosphorylated by the Ser/Thr kinase GSK3 in human MM cell lines. We show that LiCl-induced GSK3 inhibition targets these phosphorylations and specifically decreases proliferation and colony formation of Maf-expressing MM cell lines. Interestingly, bortezomib induced stabilisation of Maf phosphorylation, an observation that could explain, at least partially, the low efficacy of bortezomib for patients carrying Maf translocations. Thus, GSK3 inhibition could represent a new therapeutic approach for these patients.

Immunohistochemical staining for transcription factor MafB in alveolar macrophages is correlated with spirometric measures of airflow limitation in smokers

BACKGROUND AND OBJECTIVE

Alveolar macrophages (AM) play an important role in the pathogenesis of COPD, and their numbers are significantly increased in patients with COPD. We previously demonstrated that expression of the transcription factor, MafB, was upregulated in AM of mice exposed to cigarette smoke. The aim of this study was to investigate whether the expression of MafB is associated with the degree of airflow limitation (AFL) in smokers.

METHODS

Lung tissue specimens were obtained from male patients undergoing resection of small peripheral lung tumours. The patients were classified into three groups according to smoking index and FEV1 /FVC: (i) non-smokers or non-heavy ex-smokers without AFL (FEV1 /FVC ≥ 0.7, smoking index ≤ 400) (n=8); (ii) heavy current smokers without AFL (FEV1 /FVC ≥ 0.7, smoking index ≥ 800) (n=8); and (iii) heavy current smokers with AFL (FEV1 /FVC < 0.6, smoking index ≥ 800) (n=8). The intensity of immunostaining for MafB in AM was quantified by image analysis.

RESULTS

Immunostaining for MafB was significantly enhanced in AM of smokers with AFL compared with AM of subjects without AFL. Smoking index, FEV1/FVC and FEF(25-75%) (% predicted) were significantly correlated with the intensity of MafB immunostaining. Multiple linear regression analysis revealed that FEV1 % was also an independent negative predictor of the intensity of MafB immunostaining.

CONCLUSIONS

The degree of immunostaining for MafB in AM was correlated with the degree of AFL in smokers. MafB may be involved in the pathophysiology of COPD.

The ubiquitin-proteasomal system is critical for multiple myeloma: implications in drug discovery

Bortezomib is a specific inhibitor of proteasomes, the most important protease complexes in protein degradation. Bortezomib can induce apoptosis of a variety of cancer cells, including leukemia, lymphoma, multiple myeloma, breast cancers, prostate cancers, lung cancers, and so on. However, extensive studies and overall evaluation suggested that multiple myeloma is the most sensitive and the best responsive disease which was later approved by Food and Drug Administration for bortezomib treatment. Because proteasomes are an essential component in the ubiquitin-proteasomal protein degradation pathway, the discovery of bortezomib implicates that the UPS is critical for myeloma pathophysiology. The UPS also contains ubiquitin, ubiquitin-activating enzymes (E1), ubiquitin-conjugating enzymes (E2), ubiquitin ligases (E3) and deubiquitinases (Dubs). In this review, we examined and analyzed the recent advancements of the UPS components in multiple myeloma and its implications in drug discovery for myeloma treatment.

Molecular heterogeneity of multiple myeloma: pathogenesis, prognosis, and therapeutic implications

Multiple myeloma (MM) is characterized by a significant heterogeneity at the molecular level. The first level is the chromosomal one. Although cytogenetics is difficult to assess in MM, patients can be divided into two categories: hyperdiploidy and non-hyperdiploidy (about half in each group). Using molecular cytogenetic techniques, several subgroups of patients are identified, particularly on the basis of 14q32 translocations. This chromosomal heterogeneity is confirmed by genomic techniques (gene expression profiling or single nucleotide polymorphism/comparative genomic hybridization arrays). Unsupervised analyses of gene expression profiles identified several subgroups of patients, essentially on the basis of chromosomal abnormalities such as hyperdiploidy or 14q32 translocations. However, these analyses failed to separate MM into subentities, which could lead to specific therapeutic approaches, as is the case for non-Hodgkin's lymphomas. Nevertheless, these chromosomal/genomic data can be used for prognostication of patients. Specific chromosomal changes, such as loss of the short arm of chromosome 17, or specific gene expression profiles clearly identify patients with short survival. No molecular change so far has been associated with long survival or even cure, probably because of the short follow-up observed in all studies. So far, it is unclear how to use this massive amount of data to treat patients. Because of the complex and heterogeneous picture of the molecular profiles, it is unexpected that targeted therapies might play a role in MM. The only recognized indication is to propose bortezomib-based approaches for the treatment of patients displaying the translocation t(4;14).

A Novel Transgenic Mouse Model of the Human Multiple Myeloma Chromosomal Translocation t(14;16)(q32;q23)

Multiple myeloma (MM) is a currently incurable neoplasm of terminally differentiated B cells. The translocation and/or overexpression of c-MAF have been observed in human MM. Although c-MAF might function as an oncogene in human MM, there has been no report thus far describing the direct induction of MM by c-MAF overexpression in vivo. In this study, we have generated transgenic (TG) mice that express c-Maf specifically in the B-cell compartment. Aged c-Maf TG mice developed B-cell lymphomas with some clinical features that resembled those of MM, namely, plasma cell expansion and hyperglobulinemia. Quantitative RT-PCR analysis demonstrated that Ccnd2 and Itgb7, which are known target genes of c-Maf, were highly expressed in the lymphoma cells. This novel TG mouse model of the human MM t(14;16)(q32;q23) chromosomal translocation should serve to provide new insight into the role of c-MAF in tumorigenesis. Cancer Res; 71(2); 339–48. ©2011 AACR.

Translocation t(14;16) and multiple myeloma: is it really an independent prognostic factor?

Many trials in myeloma are stratified on cytogenetic abnormalities. Among them, the most commonly chosen are the t(4;14), the del(17p), and the t(14;16). If data are well established for t(4;14) and del(17p), very few data support the use of t(14;16). To address this issue, we retrospectively analyzed 1003 patients with newly diagnosed myeloma for this abnormality. We identified 32 patients with the t(14;16). Compared with patients lacking the t(14;16), we did not observe any difference in overall survival (P = .28). Moreover, in multivariate analyses, the t(14;16) was not prognostic (P = .39). In conclusion, our data do not support the use of t(14;16)-specific probes in the diagnostic panels of multiple myeloma.

SUMOylation negatively regulates transcriptional and oncogenic activities of MafA

Dysregulated expression of Maf proteins (namely c-Maf, MafA and MafB) leads to multiple myeloma in humans and oncogenic transformation of chicken embryonic fibroblasts. Maf proteins are transcriptional activators of tissue-specific gene expression and regulators of cell differentiation. For example, MafA is a critical regulator of crystallin genes and the lens differentiation program in chickens. In mammals, MafA is essential for the development of mature insulin-producing beta-cells of pancreas. It has been shown that MafA protein stability is regulated by phosphorylations at multiple serine and threonine residues. Here, we report that Maf proteins are also post-translationally modified by small ubiquitin-like modifier (SUMO) proteins at a conserved lysine residue in the amino-terminal transactivator domain. A SUMOylation-deficient mutant of MafA (K32R) was more potent than wild-type MafA in transactivating luciferase reporter construct driven by alphaA-crystallin or insulin gene promoter. In ovo electroporation into developing chicken embryo showed that the K32R mutant induced ectopic delta-crystallin gene expression more efficiently than the wild-type MafA. We also demonstrated that the K32R mutant had enhanced ability to induce colony formation of a chicken fibroblast cell line DF-1. Therefore, SUMOylation is a functional post-translational modification of MafA that negatively regulates its transcriptional and transforming activities.

Detection of Chromosome 13q Deletions and IgH Translocations in Patients with Multiple Myeloma by FISH: Comparison with Karyotype Analysis

Multiple myeloma (MM) is a plasma cell dyscrasia characterized by frequent 13q deletions and IgH translocations that have clinical prognostic significance. We evaluated clonal plasma cells by interphase fluorescence in situ hybridization (FISH) and combined with immunofluorescence detection of cytoplasmic light chain (cIg-FISH) for the presence of 13q deletions and IgH translocations. The FISH results were compared with conventional cytogenetic analysis. Of the 25 bone marrow specimens from MM patients, 11 (44%) had 13q deletions. IgH translocations involving cyclin D1 (t(11;14)) and FGFR3 (t(4;14)) were found in 32 and 36%, respectively. P53 deletions were detected in 20% of the cases. One patient had coexistence of t(ll;14) and t(4;14), which has not been previously reported. Conventional cytogenetic analysis was performed in 15 cases and revealed complex numerical and structural changes in 7. Karyotype analysis failed to detect 3 of 6 cases with 13q deletions, and also missed most of the IgH translocations and p53 deletions detected by cIg-FISH. On the other hand, the complex numerical and structural changes shown by conventional cytogenetics were not demonstrated by interphase FISH. Since 13q deletions, IgH translocations and a hypodiploid karyotype are significant prognostic factors for MM, our study illustrates the importance of combining conventional cytogenetics with interphase FISH analysis in patients with MM.

Identification of primary MAFB target genes in multiple myeloma

OBJECTIVE

In multiple myeloma (MM), seven primary recurrent translocations involving the immunoglobulin heavy chain locus have been identified. One of the partner loci maps to 20q12 and involves the MAFB gene resulting in its ectopic expression. We attempt here to identify MAFB target genes in MM.

MATERIALS AND METHODS

We used an inducible system to upregulate MAFB in MM cell lines not carrying the t(14;20). Microarray expression analysis was used to detect gene expression changes upon MAFB expression. These genes were further evaluated comparatively with gene expression profiles obtained from MM or plasma cell leukemia tumors carrying an activated MAFB gene. Functional implications of these upregulated genes were studied by testing their promoter activity in reporter assays. C-MAF was included comparatively as well.

RESULTS

The inducible cell lines identified a total of 284 modulated transcripts. After further evaluation using ex vivo data 14 common upregulated genes were found, common to the C-MAF pathway as well. The promoter activity of some of these secondary genes proved a functional relationship with MAFB. In connection with one of these secondary genes (NOTCH2), even tertiary upregulated genes were found. Functional studies indicated that inducible MAFB expression conferred antiapoptotic effects.

CONCLUSION

We identified 14 upregulated genes, and their downstream consequences in the combined MAFB/C-MAF pathway. Eleven of these genes are novel in the C-MAF pathway as well. These direct target genes may be responsible for the oncogenic transformation of MAF expressing myeloma cells.

A new MAFia in cancer

Like JUN and FOS, the Maf transcription factors belong to the AP1 family. Besides their established role in human cancer--overexpression of the large Maf genes promotes the development of multiple myeloma--they can display tumour suppressor-like activity in specific cellular contexts, which is compatible with their physiological role in terminal differentiation. However, their oncogenic activity relies mostly on the acquisition of new biological functions relevant to cell transformation, the most striking characteristic of Maf oncoproteins being their ability to enhance pathological interactions between tumour cells and the stroma.

Biologic and genetic characterization of the novel amyloidogenic lambda light chain-secreting human cell lines, ALMC-1 and ALMC-2

Primary systemic amyloidosis (AL) is a rare monoclonal plasma cell (PC) disorder characterized by the deposition of misfolded immunoglobulin (Ig) light chains (LC) in vital organs throughout the body. To our knowledge, no cell lines have ever been established from AL patients. Here we describe the establishment of the ALMC-1 and ALMC-2 cell lines from an AL patient. Both cell lines exhibit a PC phenotype and display cytokine-dependent growth. Using a comprehensive genetic approach, we established the genetic relationship between the cell lines and the primary patient cells, and we were also able to identify new genetic changes accompanying tumor progression that may explain the natural history of this patient's disease. Importantly, we demonstrate that free lambda LC secreted by both cell lines contained a beta structure and formed amyloid fibrils. Despite absolute Ig LC variable gene sequence identity, the proteins show differences in amyloid formation kinetics that are abolished by the presence of Na(2)SO(4). The formation of amyloid fibrils from these naturally secreting human LC cell lines is unprecedented. Moreover, these cell lines will provide an invaluable tool to better understand AL, from the combined perspectives of amyloidogenic protein structure and amyloid formation, genetics, and cell biology.

Genetic events in the pathogenesis of multiple myeloma

The genetics of myeloma has been increasingly elucidated in recent years. Recurrent genetic events, and also biologically distinct and clinically relevant genetic subtypes of myeloma have been defined. This has facilitated our understanding of the molecular pathogenesis of the disease. In addition, some genetic abnormalities have proved to be highly reproducible prognostic factors. With the expanding therapeutic armamentarium, it is time to include genetic assessment as part of clinical evaluation of myeloma patients to guide management. In this review we examine the role of various genetic abnormalities in the molecular pathogenesis of myeloma, and the use of such abnormalities in disease classification, prognosis and clinical management.

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.

VEGF is differentially regulated in multiple myeloma-derived cell lines by norepinephrine

Evidence from human and animal studies support the hypothesis that psychological stress can be a co-factor for the initiation and progression of cancer. Recent work from our laboratory and others have shown that the catecholamine hormone, norepinephrine (NE), may influence tumor progression of some solid epithelial tumors including nasopharyngeal carcinoma (NPC) and ovarian cancer by modulating the expression of proangiogenic and pro-metastatic factors, such as vascular endothelial growth factor (VEGF). In this study, we determined whether NE can likewise modulate the expression of VEGF in a lymphoid tumor, multiple myeloma (MM), a cancer of plasma cells. Three MM-derived cell lines, NCI-H929, MM-M1, and FLAM-76, were studied. The presence of beta1- and beta2-adrenergic receptors (ARs) was assessed using Western blotting. Cells were treated with 0, 1, and 10 microM NE for 1, 3, 6, and 24h and the levels of VEGF in culture supernatants were measured by ELISA. Immunoblots of cell lysates revealed the presence of beta1- and beta2-ARs in all three MM-derived cell lines. However, these MM-derived cell lines exhibited varying degrees of NE-dependent regulation of VEGF expression with FLAM-76 (the only IL-6-dependent cell line among the three) exhibiting the most significant stimulation, followed by MM-M1 cells and then NCI-H929. The data suggest that the ability of NE to regulate the expression of VEGF is not limited to solid epithelial tumors and suggests a possible regulatory role of catecholamine stress hormones in MM progression.

[Genetic abnormalities in multiple myeloma: role in oncogenesis and impact on survival]

PURPOSE

Recent development of interphase fluorescence in situ hybridization (FISH) allows analysis on non-proliferant plasma cells. We describe the most frequent genetic abnormalities in multiple myeloma and their prognostic value.

CURRENT KNOWLEDGE AND KEY POINTS

Most frequent genetic abnormalities are illegitimate rearrangements involving the IGH gene at 14q32 (60% of patients), hyperdiploidy (50 to 60% of patients), chromosome 13 deletion (40 to -50% of patients), chromosome 1q gain (30 to -40% of patients) chromosome 17 deletion (10% of patients). Some of these genetics abnormalities are observed in monoclonal gammopathy of undetermined significance (MGUS), a pre-malignant state. t(4;14) and t(14;16) translocations and chromosome 17 deletion negatively impact the overall survival. Patients with these genomic aberrations should be treated with specific treatment.

FUTURE PROSPECTS AND PROJECTS

Identification of genetic abnormalities is important for evaluation of prognosis and treatment protocol in multiple myeloma.

Enhanced Expression of MafB Inhibits Macrophage Apoptosis Induced by Cigarette Smoke Exposure

In the lungs of smokers, oxidative stress rises due to increase of free radicals and oxidants, including lipid peroxide (LPO). The functions of alveolar macrophages (AMs) are altered in such an environment, and their survival is prolonged against toxicities of cigarette smoke (CS) by an unknown mechanism. Whereas functions of AMs are potentially regulated by various transcriptional factors, their expressions and roles in smoking individuals have not been elucidated. Therefore, we investigated their expressions using murine model of CS exposure. Eight-week-old male B6C3F1 mice were whole-bodily exposed to CS (2 cigarettes/mouse/day, 5 d/wk) for 6 mo. Development of pulmonary emphysema in 6-mo CS-exposed mice was confirmed by a morphometric analysis. Among the transcriptional factors investigated, only MafB was upregulated in AMs from CS-exposed mice. DNA binding capacity of MafB for Maf recognition element was also increased in AMs from those mice. LPO was increased significantly in the lungs of CS-exposed mice. Because the end product of LPO, 4-hydroxy-2-nonenal, enhanced MafB expression and its transcriptional activity in a cultured macrophage cell line, LPO-related oxidative stress was suggested to be involved in the mechanism of MafB expression in CS-exposed lung. Furthermore, we established a macrophage cell line that can overexpress MafB and thereby clarify the role of MafB. Forced expression of MafB heightened cell viability and attenuated the occurrence of apoptosis in cells treated with CS-extract. These results suggest that enhanced MafB expression by oxidative stress inhibits AM cell death and prolongs their survival in the CS-exposed lung.

Molecular characterization of human multiple myeloma cell lines by integrative genomics: Insights into the biology of the disease

To investigate the patterns of genetic lesions in a panel of 23 human multiple myeloma cell lines (HMCLs), we made a genomic integrative analysis involving FISH, and both gene expression and genome-wide profiling approaches. The expression profiles of the genes targeted by the main IGH translocations showed that the WHSC1/MMSET gene involved in t(4;14)(p16;q32) was expressed at different levels in all of the HMCLs, and that the expression of the MAF gene was not restricted to the HMCLs carrying t(14;16)(q32;q23). Supervised analyses identified a limited number of genes specifically associated with t(4;14) and involved in different biological processes. The signature related to MAF/MAFB expression included the known MAF target genes CCND2 and ITGB7, as well as genes controlling cell shape and cell adhesion. Genome-wide DNA profiling allowed the identification of a gain on chromosome arm 1q in 88% of the analyzed cell lines, together with recurrent gains on 8q, 18q, 7q, and 20q; the most frequent deletions affected 1p, 13q, 17p, and 14q; and almost all of the cell lines presented LOH on chromosome 13. Two hundred and twenty-two genes were found to be simultaneously overexpressed and amplified in our panel, including the BCL2 locus at 18q21.33. Our data further support the evidence of the genomic complexity of multiple myeloma and reinforce the role of an integrated genomic approach in improving our understanding of the molecular pathogenesis of the disease. This article contains Supplementary Material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat.

Deletion (20q) as the sole abnormality in Waldenström macroglobulinemia suggests distinct pathogenesis of 20q11 anomaly

The deletion of the long arm of chromosome 20, or del(20q), is a common cytogenetic abnormality in various myeloid disorders but is less commonly seen in lymphoid neoplasms. Here we report a case of Waldenström macroglobulinemia with del(20q) as the sole cytogenetic anomaly. No translocation including immunoglobulin genes was identified by spectral karyotyping (SKY) analysis. Reviewing all 11 reported cases of plasma cell dyscrasia possessing sole del(20q), including our case, none of 4 cases with del(20q) as an initial anomaly developed myelodysplastic syndrome-acute myeloid leukemia (MDS/AML), but at least 3 cases with del(20q) appearing after chemotherapy developed MDS/AML at or after the time of del(20q). We propose that the del(20q) may have different clinical significance in plasma cell dyscrasia: one is when del(20q) appears at diagnosis and may involve the initial event of oncogenesis, and the other is when del(20q) appears after treatment and is associated with therapy-related and potential MDS/AML risk.