Malignant hematopoietic cell lines: in vitro models for the study of multiple myeloma and plasma cell leukemia

The Route of the Malignant Plasma Cell in Its Survival Niche: Exploring “Multiple Myelomas”

Growing evidence points to multiple myeloma (MM) and its stromal microenvironment using several mechanisms to subvert effective immune and anti-tumor responses. Recent advances have uncovered the tumor-stromal cell influence in regulating the immune-microenvironment and have envisioned targeting these suppressive pathways to improve therapeutic outcomes. Nevertheless, some subgroups of patients include those with particularly unfavorable prognoses. Biological stratification can be used to categorize patient-, disease- or therapy-related factors, or alternatively, these biological determinants can be included in a dynamic model that customizes a given treatment to a specific patient. Genetic heterogeneity and current knowledge enforce a systematic and comprehensive bench-to-bedside approach. Given the increasing role of cancer stem cells (CSCs) in better characterizing the pathogenesis of solid and hematological malignancies, disease relapse, and drug resistance, identifying and describing CSCs is of paramount importance in the management of MM. Even though the function of CSCs is well-known in other cancer types, their role in MM remains elusive. With this review, we aim to provide an update on MM homing and resilience in the bone marrow micro milieu. These data are particularly interesting for clinicians facing unmet medical needs while designing novel treatment approaches for MM.

The aspartyl protease DDI2 drives adaptation to proteasome inhibition in multiple myeloma

Proteasome inhibitors, such as bortezomib, are first-line therapy against multiple myeloma (MM). Unfortunately, patients frequently become refractory to this treatment. The transcription factor NRF1 has been proposed to initiate an adaptation program that regulates proteasome levels. In the context of proteasome inhibition, the cytosolic protease DDI2 cleaves NRF1 to release an active fragment that translocates to the nucleus to promote the transcription of new proteasome subunits. However, the contribution of the DDI2-NRF1 pathway to bortezomib resistance is poorly understood. Here we show that upon prolonged bortezomib treatment, MM cells become resistant to proteasome inhibition by increasing the expression of DDI2 and consequently activation of NRF1. Furthermore, we found that many MM cells became more sensitive to proteasome impairment in the context of DDI2 deficiency. Mechanistically, we demonstrate that both the protease and the HDD domains of DDI2 are required to activate NRF1. Finally, we show that partial inhibition of the DDI2-protease domain with the antiviral drug nelfinavir increased bortezomib susceptibility in treated MM cells. Altogether, these findings define the DDI2-NRF1 pathway as an essential program contributing to proteasome inhibition responses and identifying DDI2 domains that could be targets of interest in bortezomib-treated MM patients.

IgA Monoclonal Gammopathy with Pseudohyperphosphatemia

Monoclonal gammopathies (MGs) reflect conditions in which abnormal amounts of immunoglobulins are produced by a clone that developed from a single pro-B germ cell. They range from asymptomatic, benign disorders such as monoclonal gammopathy of undetermined significance to malignant plasma cell and lymphoid disorders, including multiple myeloma and Waldenstorm macroglobulinemia. The identification of the particular subtype of immunoglobulin molecule is done by serum immunofixation by use of specific antisera directed against different subtypes of immunoglobulin classes. However depending upon the characteristic position taken up by migrating M band on protein electrophoresis due to its molecular weight and charge, serum protein electrophoresis can itself reveal the nature of the immunoglobulin without the need to do serum immunofixation. IgA mostly migrates to beta globulin region and may often be missed out for lack of a sharp, discrete M band in gamma globulin region. Systemic manifestations of MG can be attributed to the physicochemical properties of the monoclonal immunoglobulin, to its antibody activity or to other mechanisms. We describe a case of IgA MG with pseudohyperphosphatemia.

The Role of NKL Homeobox Genes in T-Cell Malignancies

Homeobox genes encode transcription factors controlling basic developmental processes. The homeodomain is encoded by the homeobox and mediates sequence-specific DNA binding and interaction with cofactors, thus operating as a basic regulatory platform. Similarities in their homeobox sequences serve to arrange these genes in classes and subclasses, including NKL homeobox genes. In accordance with their normal functions, deregulated homeobox genes contribute to carcinogenesis along with hematopoietic malignancies. We have recently described the physiological expression of eleven NKL homeobox genes in the course of hematopoiesis and termed this gene expression pattern NKL-code. Due to the developmental impact of NKL homeobox genes these data suggest a key role for their activity in the normal regulation of hematopoietic cell differentiation including T-cells. On the other hand, aberrant overexpression of NKL-code members or ectopical activation of non-code members has been frequently reported in lymphoid and myeloid leukemia/lymphoma, demonstrating their oncogenic impact in the hematopoietic compartment. Here, we provide an overview of the NKL-code in normal hematopoiesis and discuss the oncogenic role of deregulated NKL homeobox genes in T-cell malignancies.

A blueprint from nature: miRNome comparison of plasma cells and CHO cells to optimize therapeutic antibody production

Chinese Hamster Ovary (CHO) cells are the most frequently used biopharmaceutical production hosts, although industry is presently suffering from their variable recombinant product quality, insufficient long-term stability and low productivity. Here, we present an effort to address overall cell line engineering by a novel bottom-up microRNA (miRNA) screening approach. miRNAs are small non-coding RNAs known to regulate global gene expression at the post-transcriptional level and have proved to serve as promising tools for cell line engineering for over a decade. Here the miRNome of plasma cells (PCs) has been analyzed as the natural blueprint for optimized production and secretion of antibodies. Performing comparative miRNome cross-species expression analysis of four murine/human PC-derived (PCD) and two CHO cell lines showed 147 conserved miRNAs to be differentially expressed between PCDs and CHOs. Conducting a targeted miRNA screen of this PC-specific miRNA subset revealed 14 miRNAs to improve bioprocess relevant parameters in CHO cells, among them the PC-characteristic miR-183 cluster. Finally, miRNA target prediction tools and transcriptome analysis were combined to elucidate differentially regulated lysine degradation and fatty acid metabolism pathways in monoclonal antibody (mAb) expressing CHO-DG44 and CHO-K1 cells, respectively. Thus, substantial new insights into molecular and cellular mechanisms of biopharmaceutical production cell lines can be gained by targeted bottom-up miRNA screenings.

Multiple Myeloma Cells Depend on the DDI2/NRF1-mediated Proteasome Stress Response for Survival

Multiple myeloma (MM) cells suffer from baseline proteotoxicity due to an imbalance between the load of misfolded proteins awaiting proteolysis and the capacity of the ubiquitin-proteasome system to degrade them. This intrinsic vulnerability is at the base of MM sensitivity to agents that perturb proteostasis such as proteasome inhibitors (PIs), the mainstay of modern-day myeloma therapy. De-novo and acquired PI resistance are important clinical limitations, adversely affecting prognosis. The molecular mechanisms underpinning PI resistance are only partially understood, limiting the development of drugs that can overcome it. The transcription factor NRF1 is activated by the aspartic protease DDI2 upon proteasome insufficiency and governs proteasome biogenesis. In this work, we show that MM cells exhibit baseline NRF1 activation and are dependent upon DDI2 for survival. DDI2 knock out (KO) is cytotoxic for MM cells, both in vitro and in vivo. Protein structure-function studies show that DDI2 KO blocks NRF1 cleavage and nuclear translocation, causing impaired proteasome activity recovery upon irreversible proteasome inhibition, thereby increasing sensitivity to PI. Add-back of wild-type, but not of catalytically-dead DDI2, fully rescues these phenotypes. We propose that DDI2 is an unexplored, promising molecular target in MM by disrupting the proteasome stress response and exacerbating proteotoxicity.

An Overview of Organoid and 3-Dimensional Models in Multiple Myeloma

ABSTRACT

Multiple myeloma is a hematological malignancy of differentiated B cells that resides primarily in bone marrow niches. Its interaction with the microenvironment is known to provide a survival advantage and plays an important role in drug resistance. Despite the increased efficacy of new treatment drugs, clinical results oftentimes fall short of in vitro observations, and this disease remains incurable. Conventional 2-dimensional cultures used to perform chemosensitivity assays and the established multiple myeloma cells lines commonly used do not replicate the conditions seen in vivo. This review presents various 3-dimensional culture platforms for myeloma that attempt to overcome this obstacle by incorporating aspects of the tumor microenvironment. The unique features of each model and contributions they have provided in personalized medicine, tumor physiology, and chemosensitivity assays will be summarized.

NKL-Code in Normal and Aberrant Hematopoiesis

Simple Summary

Gene codes represent expression patterns of closely related genes in particular tissues, organs or body parts. The NKL-code describes the activity of NKL homeobox genes in the hematopoietic system. NKL homeobox genes encode transcription factors controlling basic developmental processes. Therefore, aberrations of this code may contribute to deregulated hematopoiesis including leukemia and lymphoma. Normal and abnormal activities of NKL homeobox genes are described and mechanisms of (de)regulation, function, and diseases exemplified.

Abstract

We have recently described physiological expression patterns of NKL homeobox genes in early hematopoiesis and in subsequent lymphopoiesis and myelopoiesis, including terminally differentiated blood cells. We thereby systematized differential expression patterns of eleven such genes which form the so-called NKL-code. Due to the developmental impact of NKL homeobox genes, these data suggest a key role for their activity in normal hematopoietic differentiation processes. On the other hand, the aberrant overexpression of NKL-code-members or the ectopical activation of non-code members have been frequently reported in lymphoid and myeloid leukemia/lymphoma, revealing the oncogenic potential of these genes in the hematopoietic compartment. Here, I provide an overview of the NKL-code in normal hematopoiesis and instance mechanisms of deregulation and oncogenic functions of selected NKL genes in hematologic cancers. As well as published clinical studies, our conclusions are based on experimental work using hematopoietic cell lines which represent useful models to characterize the role of NKL homeobox genes in specific tumor types.

Personalized oncology and BRAFK601N melanoma: model development, drug discovery, and clinical correlation

PURPOSE

Mutations in BRAF are the most prominent activating mutations in melanoma and are increasingly recognized in other cancers. There is currently no accepted treatment regimen for patients with mutant BRAF^K601N melanoma, and the study of melanoma driven by BRAF mutations at the 601 locus is lacking due to a paucity of cellular model systems. Therefore, we sought to better understand the treatment and clinical approach to patients with mutant BRAF^K601N melanoma and subsequently develop a novel personalized oncology platform for rare or treatment-refractory cancers.

METHODS

We developed and characterized the first patient-derived, naturally occurring BRAF^K601N melanoma model, described herein as OHRI-MEL-13, and assessed efficacy using the Prestwick Chemical Library and select targeted therapeutics.

RESULTS

OHRI-MEL-13 exhibits loss of heterozygosity of BRAF, closely mimics the original tumor's gene expression profile, is tumorigenic in immune-deficient murine models, and is available for public accession through American Type Culture Collection. We present in silico modeling data, which illustrates the therapeutic failure of BRAF^V600E-targeted therapies in BRAF^K601N mutants. Our platform elucidated a unique role for MEK inhibition with cobimetinib, which resulted in short-term clinical success by reducing the metastatic burden.

CONCLUSION

Our model of BRAF^K601N-activated melanoma was developed, thoroughly characterized, and made available for public accession. This model served to demonstrate the feasibility of a novel personalized oncology platform that could be optimized at an institutional level for rare variant or treatment-refractory cancers. We also demonstrate the clinical utility of monotherapy MEK inhibition in a case of BRAF^K601N melanoma.

Evaluating the efficacy of multiple myeloma cell lines as models for patient tumors via transcriptomic correlation analysis

Multiple myeloma (MM) cell lines are routinely used to model the disease. However, a long-standing question is how well these cell lines truly represent tumor cells in patients. Here, we employ a recently described method of transcriptional correlation profiling to compare similarity of 66 MM cell lines to 779 newly diagnosed MM patient tumors. We found that individual MM lines differ significantly with respect to patient tumor representation, with median R ranging from 0.35 to 0.54. ANBL-6 was the “best” line, markedly exceeding all others (p < 2.2e−16). Notably, some widely used cell lines (RPMI-8226, U-266) scored poorly in our patient similarity ranking (48 and 52 of 66, respectively). Lines cultured with interleukin-6 showed significantly improved correlations with patient tumor (p = 9.5e−4). When common MM genomic features were matched between cell lines and patients, only t(4;14) and t(14;16) led to increased transcriptional correlation. To demonstrate the utility of our top-ranked line for preclinical studies, we showed that intravenously implanted ANBL-6 proliferates in hematopoietic organs in immunocompromised mice. Overall, our large-scale quantitative correlation analysis, utilizing emerging datasets, provides a resource informing the MM community of cell lines that may be most reliable for modeling patient disease while also elucidating biological differences between cell lines and tumors.

Lessons Learned from Proteasome Inhibitors, the Paradigm for Targeting Protein Homeostasis in Cancer

Targeting aberrant protein homeostasis (proteostasis) in cancer is an attractive therapeutic strategy. However, this approach has thus far proven difficult to bring to clinical practice, with one major exception: proteasome inhibition. These small molecules have dramatically transformed outcomes for patients with the blood cancer multiple myeloma. However, these agents have failed to make an impact in more common solid tumors. Major questions remain about whether this therapeutic strategy can be extended to benefit even more patients. Here we discuss the role of the proteasome in normal and tumor cells, the basic, preclinical, and clinical development of proteasome inhibitors, and mechanisms proposed to govern both intrinsic and acquired resistance to these drugs. Years of study of both the mechanism of action and modes of resistance to proteasome inhibitors reveal these processes to be surprisingly complex. Here, we attempt to draw lessons from experience with proteasome inhibitors that may be relevant for other compounds targeting proteostasis in cancer, as well as extending the reach of proteasome inhibitors beyond blood cancers.

Deregulated NKL Homeobox Genes in B-Cell Lymphoma

Recently, we have described physiological expression patterns of NKL homeobox genes in early hematopoiesis and in subsequent lymphopoiesis. We identified nine genes which constitute the so-called NKL-code. Aberrant overexpression of code-members or ectopically activated non-code NKL homeobox genes are described in T-cell leukemia and in T- and B-cell lymphoma, highlighting their oncogenic role in lymphoid malignancies. Here, we introduce the NKL-code in normal hematopoiesis and focus on deregulated NKL homeobox genes in B-cell lymphoma, including HLX, MSX1 and NKX2-2 in Hodgkin lymphoma; HLX, NKX2-1 and NKX6-3 in diffuse large B-cell lymphoma; and NKX2-3 in splenic marginal zone lymphoma. Thus, the roles of various members of the NKL homeobox gene subclass are considered in normal and pathological hematopoiesis in detail.

Cancer Cell Lines Are Useful Model Systems for Medical Research

Cell lines are in vitro model systems that are widely used in different fields of medical research, especially basic cancer research and drug discovery. Their usefulness is primarily linked to their ability to provide an indefinite source of biological material for experimental purposes. Under the right conditions and with appropriate controls, authenticated cancer cell lines retain most of the genetic properties of the cancer of origin. During the last few years, comparing genomic data of most cancer cell lines has corroborated this statement and those that were observed studying the tumoral tissue equivalents included in the The Cancer Genome Atlas (TCGA) database. We are at the disposal of comprehensive open access cell line datasets describing their molecular and cellular alterations at an unprecedented level of accuracy. This aspect, in association with the possibility of setting up accurate culture conditions that mimic the in vivo microenvironment (e.g., three-dimensional (3D) coculture), has strengthened the importance of cancer cell lines for continuing to sustain medical research fields. However, it is important to consider that the appropriate use of cell lines needs to follow established guidelines for guaranteed data reproducibility and quality, and to prevent the occurrence of detrimental events (i.e., those that are linked to cross-contamination and mycoplasma contamination).

Identification of the xenograft and its ascendant sphere-forming cell line as belonging to EBV-induced lymphoma, and characterization of the status of sphere-forming cells

Background

We have characterized the human cell line arised from the Epstein–Barr virus (EBV) positive multiple myeloma aspirate subjected to the long-term cultivation. This cell line has acquired the ability to form free-floating spheres and to produce a xenograft upon transplantation into NOD/SCID mice.

Methods

Cells from both in vitro culture and developed xenografts were investigated with a number of analytical approaches, including pathomorphological analysis, FISH analysis, and analysis of the surface antigens and of the VDJ locus rearrangement.

Results

The obtained results, as well as the confirmed presence of EBV, testify that both biological systems are derived from B-cells, which, in turn, is a progeny of the EBV-transformed B-cellular clone that supplanted the primordial multiple myeloma cells. Next we assessed whether cells that (i) were constantly present in vitro in the investigated cell line, (ii) were among the sphere-forming cells, and (iii) were capable of internalizing a fluorescent TAMRA-labeled DNA probe (TAMRA+ cells) belonged to one of the three types of undifferentiated bone marrow cells of a multiple myeloma patient: CD34+ hematopoietic stem cells, CD90+ mesenchymal stem cells, and clonotypic multiple myeloma cell.

Conclusion

TAMRA+ cells were shown to constitute the fourth independent subpopulation of undifferentiated bone marrow cells of the multiple myeloma patient. We have demonstrated the formation of ectopic contacts between TAMRA+ cells and cells of other types in culture, in particular with CD90+ mesenchymal stem cells, followed by the transfer of some TAMRA+ cell material into the contacted cell.

Electronic supplementary material

The online version of this article (10.1186/s12935-019-0842-x) contains supplementary material, which is available to authorized users.

The insulin-like growth factor system in multiple myeloma: diagnostic and therapeutic potential

Multiple myeloma (MM) is a highly heterogeneous plasma cell malignancy. The MM cells reside in the bone marrow (BM), where reciprocal interactions with the BM niche foster MM cell survival, proliferation, and drug resistance. As in most cancers, the insulin-like growth factor (IGF) system has been demonstrated to play a key role in the pathogenesis of MM. The IGF system consists of IGF ligands, IGF receptors, IGF binding proteins (IGFBPs), and IGFBP proteases and contributes not only to the survival, proliferation, and homing of MM cells, but also MM-associated angiogenesis and osteolysis. Furthermore, increased IGF-I receptor (IGF-IR) expression on MM cells correlates with a poor prognosis in MM patients. Despite the prominent role of the IGF system in MM, strategies targeting the IGF-IR using blocking antibodies or small molecule inhibitors have failed to translate into the clinic. However, increasing preclinical evidence indicates that IGF-I is also involved in the development of drug resistance against current standard-of-care agents against MM, including proteasome inhibitors, immunomodulatory agents, and corticoids. IGF-IR targeting has been able to overcome or revert this drug resistance in animal models, enhancing the efficacy of standard-of-care agents. This finding has generated renewed interest in the therapeutic potential of IGF-I targeting in MM. The present review provides an update of the impact of the different IGF system components in MM and discusses the diagnostic and therapeutic potentials.

Multiple Myeloma Cells Express Key Immunoregulatory Cytokines and Modulate the Monocyte Migratory Response

Multiple myeloma (MM) is a plasma cell disorder that still remains incurable. The immune dysfunction of the host is a striking characteristic of MM, leading to tumor growth and reducing the survival rate of patients. Monocytes are precursors of conventional dendritic cells (DCs), a major player in the immunity mechanisms driving protective T cell responses against tumor. Herein, we report that human MM RPMI 8226 cell line shows a pronounced chemoattractant activity for monocytes and also expresses enhanced levels of the leukocyte chemotactic cytokines CXCL12, CCL5, MIP-1β, and CXCL10 in association with elevated levels of both key immunoregulatory interleukins such as IL-4 and IL-10. This cytokine profile was observed together with reduced expression of IFN-γ by MM RPMI 8226 cell line, a determinant interleukin involved in the acquisition of cellular-mediated protective responses against tumor cells. We further demonstrate that MM RPMI 8226 cell line expresses elevated levels of soluble form of the intercellular adhesion molecule-1 known to inhibit antitumoral T cell responses. This attractive modulation of immune responses by MM cells might provide a means to impair early antitumor responses during the establishment of cytokine-mediated immunosuppressive tumor niche.

Activation of the ileal neuroendocrine tumor cell line P-STS by acetylcholine is amplified by histamine: role of H3R and H4R

Neuroendocrine tumors may present with pseudoallergic reactions like diarrhea and idiopathic anaphylaxis. Here we present the P-STS human ileal neuroendocrine cell line as a model cell line for these tumors. Neuroendocrine markers and changes in cytoplasmic calcium concentration ([Ca2+]i) in response to several possible activators of 5-hydroxytryptamine (5-HT) release were analyzed. P-STS cells still expressed chromogranin A and synaptophysin after 2 years of culture. Tryptophan hydroxylase 1 mRNA and a low amount of 5-HT were also detected. Acetylcholine (ACh) caused a rise in [Ca2+]i. Somatostatin inhibited, whereas histamine (HA) but not the HA receptor ligand betahistine enhanced activation by ACh. The [Ca2+]i response to ACh/HA was inhibited by the HA receptor H3 (H3R) agonist methimepip and by the antidepressant imipramine. Further [Ca2+]i response studies indicated the presence of H4Rs and of a functional calcium sensing receptor. High or low affinity IgE receptor protein or mRNA were not detected. Taken together, neuroendocrine markers and response to intestinal neurotransmitters approve the P-STS cell line as a valuable model for enterochromaffin cells. Enhancement of their ACh-induced pro-secretory response by HA, with a role for H3R and H4R, suggests an amplifying role of neuroendocrine cells in allergen-induced diarrhea or anaphylaxis.

VOLIN and KJON-Two novel hyperdiploid myeloma cell lines

Multiple myeloma can be divided into two distinct genetic subgroups: hyperdiploid (HRD) or nonhyperdiploid (NHRD) myeloma. Myeloma cell lines are important tools to study myeloma cell biology and are commonly used for preclinical screening and testing of new drugs. With few exceptions human myeloma cell lines are derived from NHRD patients, even though about half of the patients have HRD myeloma. Thus, there is a need for cell lines of HRD origin to enable more representative preclinical studies. Here, we present two novel myeloma cell lines, VOLIN and KJON. Both of them were derived from patients with HRD disease and shared the same genotype as their corresponding primary tumors. The cell lines' chromosomal content, genetic aberrations, gene expression, immunophenotype as well as some of their growth characteristics are described. Neither of the cell lines was found to harbor immunoglobulin heavy chain translocations. The VOLIN cell line was established from a bone marrow aspirate and KJON from peripheral blood. We propose that these unique cell lines may be used as tools to increase our understanding of myeloma cell biology. © 2016 Wiley Periodicals, Inc.

Establishment of cell lines from both myeloma bone marrow and plasmacytoma: SNU_MM1393_BM and SNU_MM1393_SC from a single patient

Purpose. We tried to establish clinically relevant human myeloma cell lines that can contribute to the understanding of multiple myeloma (MM). Materials and Methods. Mononuclear cells obtained from MM patient's bone marrow were injected via tail vein in an NRG/SCID mouse. Fourteen weeks after the injection, tumor developed at subcutis of the mouse. The engraftment of MM cells into mouse bone marrow (BM) was also observed. We separated and cultured cells from subcutis and BM. Results. After the separation and culture of cells from subcutis and BM, we established two cell lines originating from a single patient (SNU_MM1393_BM and SNU_MM1393_SC). Karyotype of the two newly established MM cell lines showed tetraploidy which is different from the karyotype of the patient (diploidy) indicating clonal evolution. In contrast to SNU_MM1393_BM, cell proliferation of SNU_MM1393_SC was IL-6 independent. SNU_MM1393_BM and SNU_MM1393_SC showed high degree of resistance against bortezomib compared to U266 cell line. SNU_MM1393_BM had the greater lethality compared to SNU_MM1393_SC. Conclusion. Two cell lines harboring different site tropisms established from a single patient showed differences in cytokine response and lethality. Our newly established cell lines could be used as a tool to understand the biology of multiple myeloma.

The glutathione synthesis inhibitor buthionine sulfoximine synergistically enhanced melphalan activity against preclinical models of multiple myeloma

Melphalan (L-PAM) has been an integral part of multiple myeloma (MM) treatment as a conditioning regimen before stem cell transplant (SCT). After initial response, most treated patients experience relapse with an aggressive phenotype. Increased glutathione (GSH) in MM may mediate resistance to L-PAM. We demonstrated that the GSH synthesis inhibitor buthionine sulfoximine (BSO) synergistically enhanced L-PAM activity (inducing 2–4 logs of cell kill) against nine MM cell lines (also in the presence of marrow stroma or cytokines) and in seven primary MM samples (combination indices <1.0). In MM cell lines, BSO significantly (P<0.05) depleted GSH, increased L-PAM-induced single-strand DNA breaks, mitochondrial depolarization, caspase cleavage and apoptosis. L-PAM depleted GSH, but GSH rapidly recovered in a L-PAM-resistant MM cell line unless also treated with BSO. Treatment with N-acetylcysteine antagonized BSO+L-PAM cytotoxicity without increasing GSH. In human MM xenografted into beige-nude-xid mice, BSO significantly depleted MM intracellular GSH and significantly increased apoptosis compared with L-PAM alone. BSO+L-PAM achieved complete responses (CRs) in three MM xenograft models including maintained CRs >100 days, and significantly increased the median event-free survival relative to L-PAM alone. Combining BSO with L-PAM warrants clinical testing in advanced MM.

MicroRNA: important player in the pathobiology of multiple myeloma

Recent studies have revealed a pivotal role played by a class of small, noncoding RNAs, microRNA (miRNA), in multiple myeloma (MM), a plasma cell (PC) malignancy causing significant morbidity and mortality. Deregulated miRNA expression in patient's PCs and plasma has been associated with tumor progression, molecular subtypes, clinical staging, prognosis, and drug response in MM. A number of important oncogenic and tumor suppressor miRNAs have been discovered to regulate important genes and pathways such as p53 and IL6-JAK-STAT signaling. miRNAs may also form complex regulatory circuitry with genetic and epigenetic machineries, the deregulation of which could lead to malignant transformation and progression. The translational potential of miRNAs in the clinic is being increasingly recognized that they could represent novel biomarkers and therapeutic targets. This review comprehensively summarizes current progress in delineating the roles of miRNAs in MM pathobiology and management.

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

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

Nestin expression throughout multistep pathogenesis of multiple myeloma

The stem cell marker nestin (NES) is found in dividing cells of developing and regenerating tissues. Upon terminal differentiation, NES expression is diminished but may be re-expressed following injury or in cancer. Surprisingly, we recently confirmed NES as a tumour-specific marker for mature CD138(+) 38(+) plasma cells (PC) in multiple myeloma (MM). The present study analysed NES expression throughout the spectrum of MM developmental stages, starting with individuals with no haematological malignancy, through monoclonal gammopathy of undetermined significance (MGUS) and MM to plasma cell leukaemia (PCL) and MM cell lines. NES was analysed in bone marrow PC of 163 MM, four PCL and nine MGUS patients, 10 individuals with no haematological malignancy and 6 myeloma cell lines (OPM-2, RPMI-8226, MOLP-8, U-266, EJM, NCI-H929) by flow cytometry and/or real-time polymerase chain reaction or immunochemistry. We observed a tendency of increased NES expression in parallel with disease progression. NES was evaluated as a reliable marker for accurate discrimination between MM patients and the control group. High NES levels were strongly associated with the presence of 1q21 gain. For the first time, NES was demonstrated to predict worse response to conventional therapy/novel agents. These results suggest that NES might become a useful clinical parameter with an important role in MM pathogenesis.

Establishment of a bortezomib-resistant Chinese human multiple myeloma cell line: MMLAL

BACKGROUND

A new human myeloma cell line, MMLAL, was established from the myelomatous pleural effusion of a 73-year-old Chinese patient suffering from symptomatic International stage III IgG/lambda myeloma. After a brief period of complete remission, he developed aggressive systemic relapse complicated by malignant pleural effusion with exclusive plasma cell infiltration. His disease remained chemo-refractory, and died six months after relapse.

METHODS

Purified mononuclear cells from the pleural effusion of the patient were cultured in the presence of IL-6. Continually growing cells were characterized by morphological, immunophenotypic, cytogenetic, fluorescence in situ hybridization (FISH) and TP53 mutation analyses. Cell proliferation was measured and compared with other myeloma cell lines by cell counting at day 3, 6, 9, and 12. Drug resistance against bortezomib, a proteasome inhibitor approved as a frontline chemotherapy for eligible myeloma patients, was evaluated and compared with other myeloma cell lines by MTT assay.

RESULTS

Immunophenotypic analysis of the myeloma cells confirmed strong expression of plasma cell markers CD38 and CD138 but not T-cell or natural killer-cell marker CD56. Cytogenetic analysis of the myeloma cells showed a hypodiploid composite karyotype including loss of chromosome 13 and 17 or deletion of the short arm of chromosome 17, i.e. del(17p), in the form of isochromosome 17q10. FISH confirmed a hypodiploid karyotype with TP53 deletion but absence of t(4;14). Sequencing analysis of the TP53 gene indicated absence of mutation. Cell counting revealed that the maximum viable cell density was about 2.5 X 106 cells/ml. Upon bortezomib treatment, MTT assay reported an IC50 of 72.17nM, suggesting a strong bortezomib resistance.

CONCLUSION

A hypodiploid with loss of chromosome 13 and loss or del(17p) human myeloma cell line, MMLAL, was established from the pleural effusion of a Chinese myeloma patient.

Molecular events underlying interleukin-6 independence in a subclone of the CMA-03 multiple myeloma cell line

We explored the molecular mechanisms involved in the establishement of CMA-03/06, an IL-6-independent variant of the multiple myeloma cell line CMA-03 previously generated in our Institution. CMA-03/06 cells grow in the absence of IL-6 with a doubling time comparable with that of CMA-03 cells; neither the addition of IL6 (IL-6) to the culture medium nor co-culture with multipotent mesenchymal stromal cells increases the proliferation rate, although they maintain the responsiveness to IL-6 stimulation as demonstrated by STAT1, STAT3, and STAT5 induction. IL-6 independence of CMA-03/06 cells is not apparently due to the development of an autocrine IL-6 loop, nor to the observed moderate constitutive activation of STAT5 and STAT3, since STAT3 silencing does not affect cell viability or proliferation. When compared to the parental cell line, CMA-03/06 cells showed an activated pattern of the NF-κB pathway. This finding is supported by gene expression profiling (GEP) analysis identifying an appreciable fraction of modulated genes (28/308) in the CMA-03/06 subclone reported to be involved in this pathway. Furthermore, although more resistant to apoptotic stimuli compared to the parental cell line, CMA-03/06 cells display a higher sensibility to NF-κB inhibition induced by bortezomib. Finally, GEP analysis suggests an involvement of a number of cytokines, which might contribute to IL-6 independence of CMA-03/06 by stimulating growth and antiapoptotic processes. In conclusion, the parental cell-line CMA-03 and its variant CMA-03/06 represent a suitable model to further investigate molecular mechanisms involved in the IL-6-independent growth of myeloma cells.

Molecular pathogenesis of multiple myeloma: basic and clinical updates

Multiple myeloma is divided into two distinct genetic subtypes based on chromosome content. Hyperdiploid myeloma is characterized by multiple trisomies of chromosomes 3, 5, 7, 9 11, 15, 19 and 21, and lacks recurrent immunoglobulin gene translocations. Non-hyperdiploid myeloma in contrast is characterized by chromosome translocations t(4;14), t(14;16), t(14;20), t(6;14) and t(11;14). A unifying event in the pathogenesis of multiple myeloma is the dysregulated expression of a cyclin D gene, either directly by juxtaposition to an immunoglobulin enhancer, as a result of ectopic expression of a MAF family transcription factor, or indirectly by as yet unidentified mechanisms. Secondary genetic events include rearrangements of MYC, activating mutations of NRAS, KRAS or BRAF, a promiscuous array of mutations that activate NFkB and deletions of 17p. Among the poor-risk genetic features are t(4;14), t(14;16), t(14;20), del 17p and gains of 1q. Available evidence supports the use of a risk-stratified approach to the treatment of patients with multiple myeloma, with the early and prolonged use of bortezomib particularly in patients with t(4;14) and del 17p.

The PI3K inhibitor GDC-0941 combines with existing clinical regimens for superior activity in multiple myeloma

The phosphatidylinositol 3'-kinase (PI3K) pathway is dysregulated in multiple myeloma (MM); we therefore tested a highly selective class I PI3K inhibitor, GDC-0941, for anti-myeloma activity. Functional and mechanistic studies were first performed in MM cell lines, then extended to primary MM patient samples cultured in vitro. GDC-0941 was then assessed as a single agent and in various combinations in myeloma tumor xenograft models. We show p110 α and β are the predominant PI3K catalytic subunits in MM and that a highly selective class I PI3K inhibitor, GDC-0941, has robust activity as a single agent to induce cell cycle arrest and apoptosis of both MM cell lines and patient myeloma cells. Mechanistic studies revealed an induction of cell cycle arrest at G0/G1, with decreased phospho-FoxO1/3a levels, decreased cyclin D1 and c-myc expression, and an increase in the cell cycle inhibitor, p27kip. Induction of apoptosis correlated with increased expression of the pro-apoptotic BH3-only protein BIM, cleaved caspase 3 and cleaved poly (ADP-ribose) polymerase (PARP). In vitro, GDC-0941 synergized with dexamethasone (Dex) and lenalidomide (combination index values of 0.3-0.4 and 0.4-0.8, respectively); in vivo GDC-0941 has anti-myeloma activity and significantly increases the activity of the standard of care agents in several murine xenograft tumor models (additional tumor growth inhibition of 37-53% (Dex) and 22-72% (lenalidomide)). These data provide a clear therapeutic hypothesis for the inhibition of PI3K and provide a rationale for clinical development of GDC-0941 in myeloma.

Molecular pathogenesis of multiple myeloma and its premalignant precursor

Multiple myeloma is a monoclonal tumor of plasma cells, and its development is preceded by a premalignant tumor with which it shares genetic abnormalities, including universal dysregulation of the cyclin D/retinoblastoma (cyclin D/RB) pathway. A complex interaction with the BM microenvironment, characterized by activation of osteoclasts and suppression of osteoblasts, leads to lytic bone disease. Intratumor genetic heterogeneity, which occurs in addition to intertumor heterogeneity, contributes to the rapid emergence of drug resistance in high-risk disease. Despite recent therapeutic advances, which have doubled the median survival time, myeloma continues to be a mostly incurable disease. Here we review the current understanding of myeloma pathogenesis and insight into new therapeutic strategies provided by animal models and genetic screens.

Characterization of ligand binding to the σ(1) receptor in a human tumor cell line (RPMI 8226) and establishment of a competitive receptor binding assay

The standard assay for the determination of σ(1) receptor affinities of novel compounds is a competitive binding assay using [(3)H]-(+)-pentazocine as radioligand and membrane preparations from guinea pig brain. Herein, a novel competitive binding assay was developed employing the hematopoietic cell line of human multiple myeloma (RPMI 8226), which expresses a large amount of the human σ(1) receptor. Membrane fragments of RPMI 8226 cells were prepared and characterized. A Western blot analysis confirmed the high density of σ(1) receptors in this cell line. Assay conditions were carefully optimized leading to an incubation period of 120 min, an incubation temperature of 37°C, and receptor material for each well was prepared from 300,000 cells. It was shown that a large excess (10 μM) of (+)-pentazocine, haloperidol, and di-o-tolylguanidine provided the same results during determination of the nonspecific binding. Saturation experiments with the radioligand [(3)H]-(+)-pentazocine led to a K(d)-value of 36±0.3 nM and a B(max)-value of 477±7 fmol/mg protein. These data resulted in approximately 122,000 σ(1) binding sites per cell. The assay was validated by using six known σ(1) ligands and eight σ(1) ligands prepared in our lab. The K(i)-values determined with RPMI 8226-derived receptor material are in good accordance with the K(i)-values obtained with guinea pig brain membrane preparations. Compared with guinea pig brain preparations, the RPMI 8226-derived receptor material represents a better standardized receptor material with a high density of human σ(1) receptors.

Large-scale protein profiling in human cell lines using antibody-based proteomics

Human cancer cell lines grown in vitro are frequently used to decipher basic cell biological phenomena and to also specifically study different forms of cancer. Here we present the first large-scale study of protein expression patterns in cell lines using an antibody-based proteomics approach. We analyzed the expression pattern of 5436 proteins in 45 different cell lines using hierarchical clustering, principal component analysis, and two-group comparisons for the identification of differentially expressed proteins. Our results show that immunohistochemically determined protein profiles can categorize cell lines into groups that overall reflect the tumor tissue of origin and that hematological cell lines appear to retain their protein profiles to a higher degree than cell lines established from solid tumors. The two-group comparisons reveal well-characterized proteins as well as previously unstudied proteins that could be of potential interest for further investigations. Moreover, multiple myeloma cells and cells of myeloid origin were found to share a protein profile, relative to the protein profile of lymphoid leukemia and lymphoma cells, possibly reflecting their common dependency of bone marrow microenvironment. This work also provides an extensive list of antibodies, for which high-resolution images as well as validation data are available on the Human Protein Atlas ( www.proteinatlas.org ), that are of potential use in cell line studies.

Use of transcriptional signatures induced in lymphoid and myeloid cell lines as an inflammatory biomarker in Type 1 diabetes

Inflammation is common to many disorders and responsible for tissue and organ damage. In many disorders, the associated peripheral cytokine milieu is dilute and difficult to measure, necessitating development of more sensitive and informative biomarkers for mechanistic studies, earlier diagnosis, and monitoring therapeutic interventions. Previously, we have shown that plasma of recent-onset (RO) Type 1 diabetes patients induces a disease-specific proinflammatory transcriptional profile in fresh peripheral blood mononuclear cells (PBMC) compared with that of healthy controls (HC). To eliminate assay variance introduced through the use of multiple donors or multiple draws of the same person over time, we evaluated human leukemia cell lines as potential surrogates for fresh PBMC. We 1) tested seven different cell lines in their power to differentiate RO from HC plasma and 2) compared the similarity of the signatures generated across the seven cell lines to that obtained with fresh PBMC. While each cell line tested exhibited a distinct transcriptional response when cultured with RO or HC plasma, the expression profile induced in any single cell line shared little identity with that of the other cell lines or fresh PBMC. In terms of regulated biological pathways, the transcriptional response of each cell line shared varying degrees of functional identity with fresh PBMC. These results indicate that use of human leukemia cell lines as surrogates for fresh PBMC has potential in detecting perturbations to the peripheral cytokine milieu. However, the response of each is distinct, possessing varying degrees of functional relatedness to that observed with PBMC.

Establishment and culture of leukemia-lymphoma cell lines

The advent of continuous human leukemia-lymphoma cell lines as a rich resource of abundant, accessible, and manipulable living cells has contributed significantly to a better understanding of the pathophysiology of hematopoietic tumors. The first leukemia-lymphoma cell lines were established in 1963 and since then large numbers of new cell lines have been described. The major advantages of continuous leukemia-lymphoma cell lines are the unlimited supply and worldwide availability of identical cell material and the infinite viable storability in liquid nitrogen. These cell lines are characterized generally by monoclonal origin and differentiation arrest, sustained proliferation in vitro under preservation of most cellular features, and by specific genetic alterations. Here some of the more promising techniques for establishing new leukemia-lymphoma cell lines and the basic principles for culturing these cells are described. Several clinical and cell culture parameters might have some influence on the success rate, e.g., choice of culture medium and culture conditions, specimen site of the primary cells, and status of the patient at the time of sample collection.

Effects of native human leukocyte interferon-alpha and recombinant human interferon-alpha on P3-X63-Ag8.653 mouse myeloma cell growth

Multiple myeloma (MM) remains largely incurable, although traditional chemotherapy and new compounds have been shown to produce a clinical response. Clinical studies were performed to determine the effectiveness of interferon-alpha (IFN-alpha) in MM, which has also recently been shown to function as a survival factor for MM cells. The effects of different doses of native human leukocyte interferon-alpha (nhIFN-alpha), recombinant human interferon-alpha2a (rhIFN-alpha2a) and recombinant human interferon-alpha2b (rhIFN-alpha2b) on in vitro P3-X63-Ag8.653 mouse myeloma cell growth were compared. A statistically significant dose-dependent reduction in cell viability following cell culture with nhIFN-alpha was observed. On the other hand, a statistically significant increase in cell viability was observed following cell culture with rhIFN-alpha2a and rhIFN-alpha2b, but only in relation to the control group and seemingly without dose dependency. These results highlight the importance of the type of human IFN-alpha used in the treatment and study of MM, and suggest that nhIFN-alpha may have a role in future personalized therapy approaches.

A comparison between protein profiles of B cell subpopulations and mantle cell lymphoma cells

Background

B-cell lymphomas are thought to reflect different stages of B-cell maturation. Based on cytogenetics and molecular markers, mantle cell lymphoma (MCL) is presumed to derive predominantly from naïve, pre-germinal centre (pre-GC) B lymphocytes. The aim of this study was to develop a method to investigate the similarity between MCL cells and different B-cell compartments on a protein expression level.

Methods

Subpopulations of B cells representing the germinal centre (GC), the pre-GC mantle zone and the post-GC marginal zone were isolated from tonsils using automated magnetic cell sorting (AutoMACS) of cells based on their expression of CD27 and IgD. Protein profiling of the B cell subsets, of cell lines representing different lymphomas and of primary MCL samples was performed using top-down proteomics profiling by surface-enhanced laser detection/ionization time-of-flight mass spectrometry (SELDI-TOF-MS).

Results

Quantitative MS data of significant protein peaks (p-value < 0.05) separating the three B-cell subpopulations were generated. Together, hierarchical clustering and principal component analysis (PCA) showed that the primary MCL samples clustered together with the pre- and post-GC subpopulations. Both primary MCL cells and MCL cell lines were clearly separated from the B cells representing the GC compartment.

Conclusion

AutoMACS sorting generates sufficient purity to enable a comparison between protein profiles of B cell subpopulations and malignant B lymphocytes applying SELDI-TOF-MS. Further validation with an increased number of patient samples and identification of differentially expressed proteins would enable a search for possible treatment targets that are expressed during the early development of MCL.

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

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

The oral protein-kinase C beta inhibitor enzastaurin (LY317615) suppresses signalling through the AKT pathway, inhibits proliferation and induces apoptosis in multiple myeloma cell lines

Deregulation of the protein kinase C (PKC) signalling pathway has been implicated in tumor progression. Here we investigated the PKC inhibitor enzastaurin for its activity against multiple myeloma (MM) cells. Enzastaurin suppresses cell proliferation in a large panel of human myeloma cell lines (HMCLs), with IC50 values ranging from 1.3 to 12.5 microM and induces apoptosis, which is prevented by the ZVAD-fmk broad caspase inhibitor. These results are consistent with decreased phosphorylation of AKT and GSK3-beta, a downstream target of the AKT pathway and a pharmacodynamic marker for enzastaurin. Furthermore, enzastaurin cytotoxicity is retained when HMCLs were cocultured with multipotent mesenchymal stromal cells. Enzastaurin has additive or synergistic cytotoxic effects with bortezomib or thalidomide. Considering the strong anti-myeloma activity of enzastaurin in vitro and in animal models and its safe toxicity profile, phase II studies in MM patients of enzastaurin alone or in combination with other drugs are warranted.

Characterization of MYC translocations in multiple myeloma cell lines

Translocations involving an MYC gene (c >> N >>L) are very late tumor progression events and provide a paradigm for secondary translocations in multiple myeloma. Using a combination of fluorescent in situ hybridization and comparative genomic hybridization arrays (aCGH), we have identified rearrangements of an MYC gene in 40 of 43 independent myeloma cell lines. A majority of MYC translocations involve an Ig locus (IgH > Iglambda >> Igkappa), but the breakpoints only infrequently occur near or within switch regions or V(D)J sequences. Surprisingly, about 40% of MYC translocations do not involve an Ig locus. The MYC translocations mostly are nonreciprocal translocations or insertions, often with the involvement of three chromosomes and sometimes with associated duplication, amplification, inversion, and other associated chromosomal abnormalities. High-density aCGH analyses should facilitate the cloning of MYC breakpoints, enabling the determination of their structures and perhaps elucidating how rearrangements not involving an Ig gene cause dysregulation of an MYC gene.

Gene transfer of Hodgkin cell lines via multivalent anti-CD30 scFv displaying bacteriophage

Background

The display of binding ligands, such as recombinant antibody fragments, on the surface of filamentous phage makes it possible to specifically attach these phage particles to target cells. After uptake of the phage, their internal single-stranded DNA is processed by the host cell, which allows transient expression of an encoded eukaryotic gene cassette. This opens the possibility to use bacteriophage as vectors for targeted gene therapy, although the transduction efficiency is very low.

Results

Here we demonstrate the display of an anti-CD30 single chain variable fragment fused to the major coat protein pVIII on the surface of bacteriophage. These phage particles showed an improved binding and transduction efficiency of CD30 positive Hodgkin-lymphoma cells, compared to bacteriophage with the anti-CD30 single chain variable fragment fused to the minor coat protein pIII.

Conclusion

We can conclude from the results that the postulated multivalency of the anti-CD30-pVIII displaying bacteriophage combined with disseminated display of the anti-CD30 scFv on the whole particle surface is responsible for the improved gene transfer rate. These results mark an important step towards the use of phage particles as a cheap and safe gene transfer vehicle for the gene delivery of the desired target cells via their specific surface receptors.

The Y-box binding protein YB-1 is associated with progressive disease and mediates survival and drug resistance in multiple myeloma

Current knowledge about molecular mechanisms underlying disease progression and drug resistance in multiple myeloma (MM) is still limited. Here, we analyzed the potential pathogenetic role of the Y-box binding protein YB-1 in MM. YB-1 is a member of the cold-shock domain protein superfamily and involved in various cellular functions such as proliferation. Immunohistochemical analyses revealed that neither normal bone marrow (BM) plasma cells (PCs), premalignant PCs of patients with monoclonal gammopathy of unknown significance (MGUS), nor MM cells with a mature morphology showed expression of YB-1 in situ. In contrast, YB-1 was strongly expressed in situ in normal PC precursor blasts as well as in a MM subset and in vitro in all of the evaluated MM cell lines. The YB-1-expressing MM cells were characterized by an immature morphology and a highly proliferative phenotype as defined by Ki 67 expression. We observed that siRNA-mediated knockdown of YB-1 decreased proliferation and induced apoptosis in MM cells even in the presence of BM stromal cells. Furthermore, we found that overexpression of YB-1 mediated resistance toward doxorubicin-induced apoptosis in MM cells. Thus, YB-1 contributes to disease progression, survival, and drug resistance in MM and might therefore provide an attractive therapeutic target.

The requirement for DNAM-1, NKG2D, and NKp46 in the natural killer cell-mediated killing of myeloma cells

Recent evidence suggests a role for natural killer (NK) cells in the control of multiple myeloma. We show that expression of the NK cell receptor DNAM-1 (CD226) is reduced on CD56(dim) NK cells from myeloma patients with active disease compared with patients in remission and healthy controls. This suggested that this receptor might play a role in NK-myeloma interactions. The DNAM-1 ligands Nectin-2 (CD112) and the poliovirus receptor (PVR; CD155) were expressed by most patient myeloma samples analyzed. NK killing of patient-derived myelomas expressing PVR and/or Nectin-2 was DNAM-1 dependent, revealing a functional role for DNAM-1 in myeloma cell killing. In myeloma cell lines, cell surface expression of PVR was associated with low levels of NKG2D ligands, whereas cells expressing high levels of NKG2D ligands did not express PVR protein or mRNA. Furthermore, NK cell-mediated killing of myeloma cell lines was dependent on either DNAM-1 or NKG2D but not both molecules. In contrast, the natural cytotoxicity receptor NKp46 was required for the killing of all myeloma cell lines analyzed. Thus, DNAM-1 is important in the NK cell-mediated killing of myeloma cells expressing the cognate ligands. The importance of NKp46, NKG2D, and DNAM-1 in myeloma killing mirrors the differential expression of NK cell ligands by myeloma cells, reflecting immune selection during myeloma disease progression.

Beta-defensin production by human colonic plasma cells: a new look at plasma cells in ulcerative colitis

BACKGROUND

Previously, we showed that colonic epithelium of ulcerative colitis (UC) patients expresses increased levels of mRNA for 3 antimicrobial peptides, human beta-defensin 2 (hBD-2), hBD-3, and hBD-4 compared to controls.

METHODS

Human colon mucosa was analyzed using double immunofluorescence staining, in situ hybridization, immunoelectron microscopy, and quantitative real-time reverse-transcriptase polymerase chain reaction (qRT-PCR) with specific antibodies and probes in the respective assays.

RESULTS

We demonstrate that lamina propria in colon from UC patients, Crohn's colitis patients, and controls contain cells that express hBD-2. These cells were identified as mature plasma cells by the highly specific CD138 marker, by their prominent IgA or IgG expression, and by their ultrastructural characteristics. By immunoelectron microscopy it was furthermore shown that the hBD-2 peptide was expressed in rough endoplasmic reticulum, the Golgi complex, and cytoplasmic vesicles, reflecting consecutive steps of synthesis and transport for secretion. Plasma cells were 2-3 times more abundant in UC colon than in control colon and Crohn's colitis. Moreover, plasma cells in UC colon expressed hBD-3 and hBD-4 mRNA. Additionally, hBD-2 mRNA expression was demonstrated in 3 out of 4 well-characterized plasma cell lines.

CONCLUSIONS

Mature colonic plasma cells can express multiple beta-defensins. In UC, defensin production by plasma cells is probably clinically relevant since plasma cells accumulate in large numbers between the distorted crypts and muscularis mucosae, first focally than diffusely, so as to protect against microbial attack.