Citron Rho-interacting kinase silencing causes cytokinesis failure and reduces tumor growth in multiple myeloma

Citron Rho-interacting serine/threonine kinase (CIT) is a serine/threonine kinase that acts as a key component of the midbody and is essential for cytokinesis. CIT has been reported to be highly expressed in some tumor tissues and to play a role in cancer proliferation; however, the significance of CIT has not been investigated in multiple myeloma (MM). Here, we identified, by protein microarray and immunohistochemistry, that CIT is 1 of the upregulated proteins in the plasma cells of MM patients compared with healthy controls. Analysis of a gene expression profile data set showed that MM patients with high CIT gene expression had significantly worse overall survival compared with MM patients with low CIT gene expression. CIT silencing in MM cell lines induced cytokinesis failure and resulted in decreased MM cell proliferation in vitro and in vivo. TP53 expression was found to be an independent predictor of CIT dependency, with low-TP53 cell lines exhibiting a strong dependency on CIT. This study provides the rationale for CIT being a potential therapeutic target in MM in future trials.

Profiling of circulating exosomal miRNAs in patients with Waldenström Macroglobulinemia

Waldenström Macroglobulinemia (WM) is a low-grade B-cell lymphoma characterized by disease progression from IgM MGUS to asymptomatic and then symptomatic disease states. We profiled exosomes from the peripheral blood of patients with WM at different stages (30 smoldering/asymptomatic WM, 44 symptomatic WM samples and 10 healthy controls) to define their role as potential biomarkers of disease progression. In this study, we showed that circulating exosomes and their miRNA content represent unique markers of the tumor and its microenvironment. We observed similar levels of miRNAs in exosomes from patients with asymptomatic (smoldering) and symptomatic WM, suggesting that environmental and clonal changes occur in patients at early stages of disease progression before symptoms occur. Moreover, we identified a small group of miRNAs whose expression correlated directly or inversely with the disease status of patients, notably the known tumor suppressor miRNAs let-7d and the oncogene miR-21 as well as miR-192 and miR-320b. The study of these miRNAs’ specific effect in WM cells could help us gain further insights on the mechanisms underlying WM pathogenesis and reveal their potential as novel therapeutic targets for this disease.

Multiple Myeloma and the Immune Microenvironment

One of the great advances in the field of cancer therapy in recent years is the emergence of immune therapies. Immune therapies, especially immune checkpoint inhibitors, have shown promising results in pre-clinical models and clinical trials of solid tumors, such as melanoma, breast cancer and lung cancer. Therapeutic strategies targeting the immune microenvironment have also been applied to hematological malignancies such as multiple myeloma (MM), a plasma cell neoplasia characterized by clonal proliferation of malignant plasma cells mainly in the bone marrow (BM). MM is associated with both cellular and humoral immune deficiencies, indicating that the evolution of the disease from a precursor state (monoclonal gammopathy of undetermined significance (MGUS) and smoldering MM (sMM)) is associated with an immunosuppressive milieu that fosters immune escape and tumor growth. Despite significant advances in treatment, MM is mostly an incurable disease. Therefore, it is vital to develop novel therapeutic agents that not only target the MM clone itself but also the MM immune microenvironment. However, the complexity of the BM microenvironment and heterogeneity of tumor cell clones make it a difficult task for developing appropriate immune therapies of MM. In this article, we review the current knowledge of the interaction between malignant plasma cells and the bone marrow immune microenvironment during disease progression.

Blocking IFNAR1 inhibits multiple myeloma-driven Treg expansion and immunosuppression

Despite significant advances in the treatment of multiple myeloma (MM), most patients succumb to disease progression. One of the major immunosuppressive mechanisms that is believed to play a role in myeloma progression is the expansion of regulatory T cells (Tregs). In this study, we demonstrate that myeloma cells drive Treg expansion and activation by secreting type 1 interferon (IFN). Blocking IFN α and β receptor 1 (IFNAR1) on Tregs significantly decreases both myeloma-associated Treg immunosuppressive function and myeloma progression. Using syngeneic transplantable murine myeloma models and bone marrow (BM) aspirates of MM patients, we found that Tregs were expanded and activated in the BM microenvironment at early stages of myeloma development. Selective depletion of Tregs led to a complete remission and prolonged survival in mice injected with myeloma cells. Further analysis of the interaction between myeloma cells and Tregs using gene sequencing and enrichment analysis uncovered a feedback loop, wherein myeloma-cell-secreted type 1 IFN induced proliferation and expansion of Tregs. By using IFNAR1-blocking antibody treatment and IFNAR1-knockout Tregs, we demonstrated a significant decrease in myeloma-associated Treg proliferation, which was associated with longer survival of myeloma-injected mice. Our results thus suggest that blocking type 1 IFN signaling represents a potential strategy to target immunosuppressive Treg function in MM.

The importance of the genomic landscape in Waldenström's Macroglobulinemia for targeted therapeutical interventions

The Literature has recently reported on the importance of genomics in the field of hematologic malignancies, including B-cell lymphoproliferative disorders such as Waldenström's Macrolgobulinemia (WM). Particularly, whole exome sequencing has led to the identification of the MYD88L265P and CXCR4C1013G somatic variants in WM, occurring in about 90% and 30% of the patients, respectively. Subsequently, functional studies have demonstrated their functional role in supporting WM pathogenesis and disease progression, both in vitro and in vivo, thus providing the pre-clinical evidences for extremely attractive targets for novel therapeutic interventions in WM. Of note, recent evidences have also approached and defined the transcriptome profiling of WM cells, revealing a signature that mirrors the somatic aberrations demonstrated within the tumor clone. A parallel research field has also reported on microRNAs (miRNAs), highlighting the oncogenic role of miRNA-155 in WM. In the present review, we focus on the latest reports on genomics and miRNAs in WM, providing an overview of the clinical relevance of the latest acquired knowledge about genomics and miRNA aberrations in WM.

Cryptococcal-related meningoencephalitis in a patient with sarcoidosis and CD4 lymphocytopenia: thorough immunological characterization of lymphocyte homeostasis

Cryptococcal meningoencephalitis is the most common infective complication observed in patients with CD4 lymphocytopenia, including sarcoidosis. T-cell immunity is well characterized in HIV-related infections and data regarding immunity in cryptococcosis animal models is now available; on the contrary, little is known about the immune status in non-HIV-related infections. We report on reduced production of new T cells observed in a patient with sarcoidosis, CD4 lymphocytopenia, and cryptococcal-related meningoencephalitis. Although T cells presented with an intact proliferative capacity, they were oligoclonally expanded showing an effector memory phenotype. However, the deleterious activity of effector memory cells could have been controlled by the expansion of the regulatory T cell subset with the highest suppressive capability. This information provides a better understanding of the immune response to Cryptococcus occurring in non-HIV-associated cases, the predisposition to infection, and the role of different cell subtypes in controlling the disease in humans.

Platelets Enhance Multiple Myeloma Progression via IL-1β Upregulation

Purpose: Tumor cell-platelet interactions contribute to tumor progression and metastasis in solid tumors. However, the role of platelets in hematological malignancies is not clear. We investigated the association of platelet activation status with clinical stages in multiple myeloma (MM) patients and explored the role of platelets in MM progression.Experimental Design: Platelets were obtained from healthy donors and MM patients. We examined platelet activation status in MM patients by flow cytometry and transmission electron microscopy. We also observed the enriched pathways that are involved with platelet activation in RNA sequencing of platelets. MM cell lines were used to assess the effect of platelets on MM cell proliferation in vitro and their engraftment in vivo RNA sequencing of MM cell lines was performed to explore molecular mechanisms underlying MM cell-platelet interaction and a CRISPR/Cas9 knockout approach was used for validation.Results: Platelets from MM patients were highly activated with disease progression. RNA sequencing of platelets revealed that genes involved in platelets were enriched in patients with smoldering MM (SMM) or MM. Platelets promoted MM cell proliferation in vitro and contributed to tumor engraftment in bone marrow in vivo RNA sequencing revealed that IL-1β was upregulated in MM cell lines co-cultured with platelets, whereas IL-1β knockout in MM cell lines abrogated the effects of platelets on MM cell proliferation and engraftment in vivoConclusions: Platelets from MM patients were highly activated with disease progression. IL-1β is critical to platelet-mediated MM progression and might be a potential target for MM treatment. Clin Cancer Res; 24(10); 2430-9. ©2018 AACR.

Bone Marrow Stroma and Vascular Contributions to Myeloma Bone Homing

PURPOSE OF THE REVIEW

Herein we dissect mechanisms behind the dissemination of cancer cells from primary tumor site to the bone marrow, which are necessary for metastasis development, with a specific focus on multiple myeloma.

RECENT FINDINGS

The ability of tumor cells to invade vessels and reach the systemic circulation is a fundamental process for metastasis development; however, the interaction between clonal cells and the surrounding microenvironment is equally important for supporting colonization, survival, and growth in the secondary sites of dissemination. The intrinsic propensity of tumor cells to recognize a favorable milieu where to establish secondary growth is the basis of the "seed and soil" theory. This theory assumes that certain tumor cells (the "seeds") have a specific affinity for the milieu of certain organs (the "soil"). Recent literature has highlighted the important contributions of the vascular niche to the hospitable "soil" within the bone marrow. In this review, we discuss the crucial role of stromal cells and endothelial cells in supporting primary growth, homing, and metastasis to the bone marrow, in the context of multiple myeloma, a plasma cell malignancy with the unique propensity to primarily grow and metastasize to the bone marrow.

Metformin Affects Cortical Bone Mass and Marrow Adiposity in Diet-Induced Obesity in Male Mice

Obesity during maturation can affect the growing skeleton directly and indirectly, although these effects and the mechanisms behind them are not fully understood. Our objective was to determine how a high-fat diet with or without metformin treatment affects skeletal development. We also sought to characterize changes that occur in white adipose tissue, circulating metabolites, lipids, and gut microbiota. A diet-induced obesity C57BL/6J mouse model was used to test the effects of obesity and metformin on bone using bone histomorphometry and microcomputed tomography. Bone marrow adipose tissue was quantified with osmium tetroxide microcomputed tomography and histology. Dual-energy x-ray absorptiometry was used to analyze body composition. Hematoxylin and eosin staining was used to assess changes in white adipose depots, mass spectrometry was used for circulating lipids and protein metabolite analysis, and ribosomal RNA sequencing was used for gut microbiome analysis. Mice fed a high fat-diet since wean displayed increased medullary areas and decreased osteoblast numbers in the long bones; this phenotype was partially normalized by metformin. Marrow and inguinal adipose expansion was also noted in obese mice, and this was partially normalized by metformin. A drug-by-diet interaction was noted for circulating lipid molecules, protein metabolites, and gut microbiome taxonomical units. Obesity was not detrimental to trabecular bone in growing mice, but bone marrow medullary expansion was observed, likely resulting from inhibition of osteoblastogenesis, and this was partially reversed by metformin treatment.

A novel in vivo model for studying conditional dual loss of BLIMP-1 and p53 in B-cells, leading to tumor transformation

The tumor suppressors B-lymphocyte-induced maturation protein-1 (BLIMP-1) and p53 play a crucial role in B-cell lymphomas, and their inactivation contributes to the pathogenesis of a wide spectrum of lymphoid malignancies, including diffuse large B-cell lymphomas (DLBCLs). Patients with activated B-cell-like (ABC) DLBCL may present with loss of BLIMP-1, c-Myc over-expression, decreased p53, and poor prognosis. Nevertheless, there is a lack of in vivo models recapitulating the biology of high-grade ABC DLBCL. We therefore aimed to develop an in vivo model aiming to recapitulate the phenotype observed in this cohort of patients. A Cre-Lox approach was used to achieve inactivation of both p53 and BLIMP-1 in murine B-cells. Contextual ablation of BLIMP-1 and p53 led to development of IgM-positive B-cell lymphoma with an aggressive phenotype, supported by c-Myc up-regulation, and accumulation of somatic mutations, as demonstrated by whole exome sequencing. Sensitivity of B-tumor cells to BTK inhibition was demonstrated. This model mirrors what reported in patients with ABC DLBLC, and therefore represents a novel model for studying the biology of ABC-DLBCL harboring the dual loss of BLIMP-1/p53 and c-Myc over-expression.

Prognostic role of circulating exosomal miRNAs in multiple myeloma

Exosomes, secreted by several cell types, including cancer cells, can be isolated from the peripheral blood and have been shown to be powerful markers of disease progression in cancer. In this study, we examined the prognostic significance of circulating exosomal microRNAs (miRNAs) in multiple myeloma (MM). A cohort of 156 patients with newly diagnosed MM, uniformly treated and followed, was studied. Circulating exosomal miRNAs were isolated and used to perform a small RNA sequencing analysis on 10 samples and a quantitative reverse transcription polymerase chain reaction (qRT-PCR) array on 156 samples. We studied the relationship between miRNA levels and patient outcomes, including progression-free survival (PFS) and overall survival (OS). We identified miRNAs as the most predominant small RNAs present in exosomes isolated from the serum of patients with MM and healthy controls by small RNA sequencing of circulating exosomes. We then analyzed exosomes isolated from serum samples of 156 patients using a qRT-PCR array for 22 miRNAs. Two of these miRNAs, let-7b and miR-18a, were significantly associated with both PFS and OS in the univariate analysis and were still statistically significant after adjusting for the International Staging System and adverse cytogenetics in the multivariate analysis. Our findings support the use of circulating exosomal miRNAs to improve the identification of patients with newly diagnosed MM with poor outcomes. The results require further validation in other independent prospective MM cohorts.

Detection of newly produced T and B lymphocytes by digital PCR in blood stored dry on nylon flocked swabs

BACKGROUND

A normal number of T-cell receptor excision circles (TRECs) and K-deleting recombination excision circles (KRECs) is considered a biomarker for adequate new T- and B-cell production. In newborns, detection of TRECs and KRECs by real time PCR from dried blood spotted on filter paper is used for the screening of severe immunodeficiency. In adults, elderly and during diseases, where the number of TRECs is lower than in newborns and children, a large amount of DNA and a sensitive method of amplification are necessary to identify newly produced lymphocytes.

METHODS

DNA was prepared from blood of 203 healthy adults (range: 18-91 years old) absorbed for 10 s on flocked swabs and let to dry, or from peripheral blood mononuclear cells. DNA was subjected to digital PCR and to well established conventional real time PCR-based method using TREC- and KREC-specific primers and probes. The number of TRECs and KRECs was expressed per mL of blood. Statistical analysis was performed by nested ANOVA, Pearson coefficient of determination, and by linear regression tests.

RESULTS

The novel method for the storage of dried blood on nylon flocked swabs and the use of digital PCR allow quantification of TRECs and KRECs with high degree of sensitivity, specificity, accuracy, and precision. TRECs and KRECs were amplified by digital PCR in all tested blood samples, including those obtained from elderly individuals (>70 years old) and that were negative by real time PCR. Furthermore, values of TRECs and KRECs obtained by digital PCR were in the range of those acquired by real time PCR.

CONCLUSIONS

Our findings demonstrate that DNA isolation from dried blood on flocked swabs followed by digital PCR-based analysis represents a useful tool for studying new lymphocyte production in adults and elderly individuals. This suggests the potential use of the methodology when monitoring of clinical variables is limited by the number of molecules that can be amplified and detected, such as in patients with immunodeficiency or under immunosuppressive therapies.

B- and T-lymphocyte number and function in HIV+/HIV- lymphoma patients treated with high-dose chemotherapy and autologous bone marrow transplantation

Combination of anti-retroviral therapy, high-dose chemotherapy (HCT) and autologous stem cell transplantation (ASCT) has led to an improved survival of HIV⁺ non-Hodgkin lymphoma (NHL) patients. We compared T- and B-cell subset recovery and related capability to respond to in-vitro stimulation, as well as T-cell repertoire modifications of HIV⁺ and HIV⁻ NHL patients undergoing HCT and ASCT as first-line consolidation or salvage treatment, using sequential blood samples obtained before and at 3, 6, 12 and 24 months after ASCT. B lymphocyte recovery occurred earlier, reaching higher levels in HIV⁺ patients as compared to HIV⁻ patients and healthy controls; in particular, immature and naïve B cells were significantly higher in HIV⁺ patients who had received rituximab in the pre-ASCT period. These lymphocytes equally responded to in-vitro stimulation. Newly produced T cells similarly increased in HIV⁺ and HIV⁻ NHL patients, but their levels remained constantly lower than in healthy controls. T lymphocytes showed a reduced proliferative capacity, but their repertoire was reassorted by the treatment. The functional and numeric B-cell recovery and the qualitative modifications of T-cell receptor repertoire may explain, at least in part, the success of this aggressive therapeutic approach in HIV⁺ patients.

Epigenomics in Waldenstrom's macroglobulinaemia

Epigenomics refers to study of the epigenome, which represents changes in gene expression that are not induced by DNA sequence aberrations. For instance, DNA methylation, histone acetylation and microRNAs may modulate gene expression without altering the gene sequence. Waldenström's macroglobulinaemia (WM) is a low-grade B-cell lymphoma, classified as lymphoplasmacytic lymphoma, characterized by the presence of clonal lymphoplasmacytic cells in the bone marrow and serum monoclonal immunoglobulin-M in the circulation. It is a rare disease and, although indolent, it remains incurable with a median overall survival of 5-6 years. Most patients succumb to disease progression. WM cells present with aberrant histone hypoacetylation that may be explained, at least in part, via deregulated microRNAs, thus suggesting the use of histone deacetylase inhibitors or microRNA-based therapies in this disease.

Abstract 679: Dual conditional loss of BLIMP-1 and p53 in B-cells drives B-cell lymphomagenesis

The transcription factor p53 is a well defined tumor suppressor involved in the modulation of cell proliferation, cell cycle progression and programmed cell death. BLIMP-1 plays a crucial role in modulating B-cell terminal differentiation towards Ig-secreting plasma cells, and it also acts as a tumor suppressor, as documented in both diffuse large B-cell lymphoma and Burkitt lymphoma. Whether B-cell specific loss of both p53 and BLIMP-1 may favor a B-cell lymphoma phenotype remains unanswered. Therefore, we aimed to define the functional relevance of both p53 and BLIMP-1 n B-cell lymphomagenesis in vivo, and generated dual p53/BLIMP-1-floxed conditional inactivation in B-cells, using mice expressing Cre recombinase under the control of CD19 promoter. 100% of the generated CD19Cre/Cre/BLIMPF/F/p53F/F transgenic mice (referred as CD19/Bl-/p53-) presented with diffuse lymphadenomegalies, marked splenomegaly, and hepatomegaly, observed in 90.3% and 77.4% of the cases, respectively. Other clinical manifestations included presence of ascites and hind lymb paralysis that were documented in 12.9% and 19.3% of the cases. The CD19/Bl-/p53- showed worse survival compared to BLIMPF/F/p53F/F mice non-expressing the CD19/Cre recombinase, CD19Cre/Cre/p53F/F, or CD19Cre/Cre/BLIMPF/F (363, 469.5, 460.5, and 770 days, respectively).

H.E. staining of CD19/Bl-/p53–derived lymph nodes, defined a nodal architecture completely effaced by a relatively monomorphic population of large sized atypical lymphoid cells with finely clumped and dispersed chromatin, and multiple basophilic medium sized, paracentrally situated nucleoli. A “starry sky” pattern was also observed. Overall, these features are compatible with a BL-like or high-grade lymphomas. IHC analysis confirmed a marked positivity for B220 staining, whit negativity for TdT, Bcl6, CD138 and CD4, CD8. Tumors were confirmed to be B220+/IgM+, with either Igk- or Ig-lambda-restriction as demonstrated by flow cytometry. Moreover, tumors were shown to be either mono- or bi-clonal, as demonstrated by Southern blotting, thus further confirming the clonal transformation induced by dual BLIMP/p53 deletion in B cells.

Whole exome sequencing was performed from B220-selected cells obtained from pathological lymph nodes of CD19/Bl-/p53- mice (n: 3) and from matched tail-derived tissues, used as germline. Agilent SureSelectXT was used for library prep. WES was performed on the Illumina HiSeq 2500 platform. Tumor and matched normal DNA sequencing data were processed using the Broad Institute best practices pipeline. We have identified 213 SNVs. Among them, somatic mutations were mapped on genes involved in the regulation of focal adhesion, PDGF singaling, p53-downstream pathway, and lipoprotein metabolism.

These studies demonstrate that the specific dual inactivation of p53 and BLIMP in B-cells promotes oncogenic transformation, resulting in aggressive B-cell lymphoma development.

Citation Format: Aldo M. Roccaro, Yawara Kawano, Antonio Sacco, Jihye Park, Michele Moschetta, Yuji Mishima, Elizabeth Morgan, Ruben Carrasco, Irene Ghobrial. Dual conditional loss of BLIMP-1 and p53 in B-cells drives B-cell lymphomagenesis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 679.

Exosomes in Tumor Angiogenesis

Exosomes are small vesicles ranging in size between 30 and 150 nm, derived from the luminal membranes of the endosome and are constitutively released by fusion with the cell membrane. Several studies have revealed that exosomes play crucial roles in mediating local and systemic cell communication through the horizontal transfer of information in the form of nucleic material and proteins. This is particularly relevant in the context of the tumor-microenvironment cross talk. Here we describe the method of isolating exosomes and their role in modifying the tumor environment and more specifically in enabling metastasis and promoting angiogenesis.

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.

Epigenetics in Multiple Myeloma

Multiple myeloma is characterized by clonal proliferation of plasma cells within the bone marrow resulting in anemia, lytic bone lesions, hypercalcemia, and renal impairment. Despite advanced in our understanding of this complex disease in recent years, it is still considered an incurable malignancy. This is, in part, due to the highly heterogenous genomic and phenotypic nature of the disease, which is to date incompletely understood. It is clear that a deeper level of knowledge of the biological events underlying the development of these diseases is needed to identify new targets and generate effective novel therapies. MicroRNAs (miRNAs), which are single strand, 20-nucleotide, noncoding RNA's, are key regulators of gene expression and have been reported to exert transcriptional control in multiple myeloma. miRNAs are now recognized to play a role in many key areas such as cellular proliferation, differentiation, apoptosis and stress response. Substantial advances have been made in recent years in terms of our understanding of the biological role of miRNAs in a diverse range of hematological and solid malignancues, In multiple myeloma these advances have yielded new information of prognostic and diagnostic relevance which have helped to shed light on epigenetic regulation in this disease.

Targeting SDF-1 in multiple myeloma tumor microenvironment

Multiple myeloma (MM) is a type of B-cell malignancy that remains incurable to date. The bone marrow (BM) microenvironment plays a crucial role in MM progression. The chemokine SDF-1 (CXCL12) is an important actor of the BM microenvironment that has the ability to regulate numerous processes related to its malignant transformation during MM development. The activity of SDF-1 is mainly mediated by its specific receptor CXCR4, which is expressed at the surface of MM cells and various other BM cell types. Current treatments available for MM patients mainly target tumor cells but have limited effects on the BM microenvironment. In this context, SDF-1 and CXCR4 represent ideal targets for the normalization of the MM-supportive BM microenvironment. The present review focuses on the activity of SDF-1 in the MM BM microenvironment and the current efforts carried out to target the SDF-1/CXCR4 axis for treatment of MM.

Aberrant Levels of miRNAs in Bone Marrow Microenvironment and Peripheral Blood of Myeloma Patients and Disease Progression

The bone marrow (BM) microenvironment of multiple myeloma (MM) is reported to play a role in the biology of disease. In this study, we found that the extracellular BM microenvironment in MM contains a unique miRNA signature detectable by miRNA microarray and quantitative real-time PCR, which is partially represented in the peripheral blood. Eleven miRNAs were significantly decreased in both BM and serum of MM patients in comparison with controls. Evaluation of these miRNAs in plasma of a separate cohort of MM patients and controls confirmed significantly aberrant levels of let-7a, let-7b, let-7i, miR-15b, miR-16, and miR-20a in both serum and plasma. We then studied the myeloma precursor diseases and found that a subset of the MM miRNAs exhibited aberrant expression in monoclonal gammopathy of undetermined significance and smoldering myeloma. miRNA analysis of enriched CD138(+) plasma cells from MM and monoclonal gammopathy of undetermined significance found that most of the validated MM BM signature miRNAs were significantly decreased in MM plasma cells. Gene expression profiling indicated that multiple targets of the decreased miRNAs found increased expression in MM plasma cells, including ATF2, HRAS, HDAC4, TGFB1, TGFBR1, and mitogen-activated protein kinases. The findings suggest that these miRNAs are detectable in aberrant levels in the peripheral blood of patients with plasma cell proliferation and may play a role in aberrant plasma cell proliferation and disease progression.

Targeting the bone marrow microenvironment in multiple myeloma

Multiple myeloma (MM) is characterized by clonal expansion of malignant plasma cells in the bone marrow (BM). Despite the significant advances in treatment, MM is still a fatal malignancy. This is mainly due to the supportive role of the BM microenvironment in differentiation, migration, proliferation, survival, and drug resistance of the malignant plasma cells. The BM microenvironment is composed of a cellular compartment (stromal cells, osteoblasts, osteoclasts, endothelial cells, and immune cells) and a non-cellular compartment. In this review, we discuss the interaction between the malignant plasma cell and the BM microenvironment and the strategy to target them.

CXCR4 Regulates Extra-Medullary Myeloma through Epithelial-Mesenchymal-Transition-like Transcriptional Activation

Extra-medullary disease (EMD) in multiple myeloma (MM) is associated with poor prognosis and resistance to chemotherapy. However, molecular alterations that lead to EMD have not been well defined. We developed bone marrow (BM)- and EMD-prone MM syngeneic cell lines; identified that epithelial-to-mesenchymal transition (EMT) transcriptional patterns were significantly enriched in both clones compared to parental cells, together with higher levels of CXCR4 protein; and demonstrated that CXCR4 enhanced the acquisition of an EMT-like phenotype in MM cells with a phenotypic conversion for invasion, leading to higher bone metastasis and EMD dissemination in vivo. In contrast, CXCR4 silencing led to inhibited tumor growth and reduced survival. Ulocuplumab, a monoclonal anti-CXCR4 antibody, inhibited MM cell dissemination, supported by suppression of the CXCR4-driven EMT-like phenotype. These results suggest that targeting CXCR4 may act as a regulator of EMD through EMT-like transcriptional modulation, thus representing a potential therapeutic strategy to prevent MM disease progression.

Incidence and clinical features of extramedullary multiple myeloma in patients who underwent stem cell transplantation

Extramedullary disease (EMD), defined as an infiltrate of clonal plasma cells at an anatomic site distant from the bone marrow, is an uncommon manifestation of multiple myeloma. Six hundred and sixty-three consecutive patients with multiple myeloma who underwent stem cell transplantation between January 2005 and December 2011 were assessed for the presence of EMD. A cohort of 55 patients with biopsy-proven EMD was identified, comprising 8·3% of the total study population. EMD was present at the time of diagnosis in 14·5% of cases and at the time of relapse in 76% of patients. The most common EMD presentations at relapse were liver involvement and pleural effusions. EMD specimens had high expression of CD44 (92%) and moderate expression of CXCR4. The median overall survival from time of myeloma diagnosis was 4·1 years (95% CI: 3·1, 5·1) and the median overall survival from time of EMD diagnosis was 1·3 years (95% CI: 0·8, 2·3). This report demonstrates that the incidence of EMD has not increased with the introduction of novel agents and stem cell transplantation. The most common EMD presentations in the relapsed setting were liver and pleural fluid. The presence of CD44 and CXCR4 expression may represent new markers of EMD that warrant further investigation.

Metabolic signature identifies novel targets for drug resistance in multiple myeloma

Drug resistance remains a major clinical challenge for cancer treatment. Multiple myeloma is an incurable plasma cell cancer selectively localized in the bone marrow. The main cause of resistance in myeloma is the minimal residual disease cells that are resistant to the original therapy, including bortezomib treatment and high-dose melphalan in stem cell transplant. In this study, we demonstrate that altered tumor cell metabolism is essential for the regulation of drug resistance in multiple myeloma cells. We show the unprecedented role of the metabolic phenotype in inducing drug resistance through LDHA and HIF1A in multiple myeloma, and that specific inhibition of LDHA and HIF1A can restore sensitivity to therapeutic agents such as bortezomib and can also inhibit tumor growth induced by altered metabolism. Knockdown of LDHA can restore sensitivity of bortezomib resistance cell lines while gain-of-function studies using LDHA or HIF1A induced resistance in bortezomib-sensitive cell lines. Taken together, these data suggest that HIF1A and LDHA are important targets for hypoxia-driven drug resistance. Novel drugs that regulate metabolic pathways in multiple myeloma, specifically targeting LDHA, can be beneficial to inhibit tumor growth and overcome drug resistance.