Insights into extramedullary tumour cell growth revealed by expression profiling of human plasmacytomas and multiple myeloma

Beyond the marrow: insights from comprehensive next-generation sequencing of extramedullary multiple myeloma tumors

Extramedullary multiple myeloma (EMM) is an aggressive form of multiple myeloma (MM). This study represents the most comprehensive next-generation sequencing analysis of EMM tumors (N = 14) to date, uncovering key molecular features and describing the tumor microenvironment. We observed the co-occurrence of 1q21 gain/amplification and MAPK pathway mutations in 79% of EMM samples, suggesting that these are crucial mutational events in EMM development. We also demonstrated that patients with mutated KRAS and 1q21 gain/amplification at the time of diagnosis have a significantly higher risk of EMM development (HR = 2.4, p = 0.011) using data from a large CoMMpass dataset. We identified downregulation of CXCR4 and enhanced cell proliferation, along with reduced expression of therapeutic targets (CD38, SLAMF7, GPRC5D, FCRH5), potentially explaining diminished efficacy of immunotherapy. Conversely, we identified significantly upregulated EZH2 and CD70 as potential future therapeutic options. For the first time, we report on the tumor microenvironment of EMM, revealing CD8+ T cells and NK cells as predominant immune effector cells using single-cell sequencing. Finally, this is the first longitudinal study in EMM revealing the molecular changes from the time of diagnosis to EMM relapse.

Proteomic and Metabolomic Analysis of Bone Marrow and Plasma from Patients with Extramedullary Multiple Myeloma Identifies Distinct Protein and Metabolite Signatures

Multiple myeloma (MM) is an incurable haematological malignancy of plasma cells in the bone marrow. In rare cases, an aggressive form of MM called extramedullary multiple myeloma (EMM) develops, where myeloma cells enter the bloodstream and colonise distal organs or soft tissues. This variant is associated with refractoriness to conventional therapies and a short overall survival. The molecular mechanisms associated with EMM are not yet fully understood. Here, we analysed the proteome of bone marrow mononuclear cells and blood plasma from eight patients (one serial sample) with EMM and eight patients without extramedullary spread. The patients with EMM had a significantly reduced overall survival with a median survival of 19 months. Label-free mass spectrometry revealed 225 proteins with a significant differential abundance between bone marrow mononuclear cells (BMNCs) isolated from patients with MM and EMM. This plasma proteomics analysis identified 22 proteins with a significant differential abundance. Three proteins, namely vascular cell adhesion molecule 1 (VCAM1), pigment epithelium derived factor (PEDF), and hepatocyte growth factor activator (HGFA), were verified as the promising markers of EMM, with the combined protein panel showing excellent accuracy in distinguishing EMM patients from MM patients. Metabolomic analysis revealed a distinct metabolite signature in EMM patient plasma compared to MM patient plasma. The results provide much needed insight into the phenotypic profile of EMM and in identifying promising plasma-derived markers of EMM that may inform novel drug development strategies.

Characterization of monoclonal gammopathy of undetermined significance progression to multiple myeloma through meta-analysis of GEO data

The etiology of monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM) is still obscure as are the processes that enable the progression of MGUS to MM. Understanding the unique vs. shared transcriptomes can potentially elucidate why individuals develop one or the other. Furthermore, highlighting key pathways and genes involved in the pathogenesis of MM or the development of MGUS to MM may allow the discovery of novel drug targets and therapies. We employed STARGEO platform to perform three separate meta-analysis to compare MGUS and MM transcriptomes. For these analyses we tagged (1) 101 MGUS patient plasma cells from bone marrow samples and 64 plasma cells from healthy controls (2) 383 MM patient CD138+ cells from bone marrow and the 101 MGUS samples in the first analysis as controls (3) 517 MM patient peripheral blood samples and 97 peripheral blood samples from healthy controls. We then utilized Ingenuity Pathway Analysis (IPA) to analyze the unique genomic signatures within and across these samples. Our study identified genes that may have unique roles in MGUS (GADD45RA and COMMD3), but also newly identified signaling pathways (EIF2, JAK/STAT, and MYC) and gene activity (NRG3, RBFOX2, and PARP15) in MGUS that have previously been shown to be involved in MM suggesting a spectrum of molecular overlap. On the other hand, genes such as DUSP4, RN14, LAMP5, differentially upregulated in MM, may be seen as tipping the scales from benignity to malignancy and could serve as drug targets or novel biomarkers for risk of progression. Furthermore, our analysis of MM identified newly associated gene/pathway activity such as inhibition of Wnt-signaling and defective B cell development. Finally, IPA analysis, suggests the multifactorial, oncogenic qualities of IFNγ signaling in MM may be a unifying pathway for these diverse mechanisms and prompts the need for further studies.

Solitary hyoid plasmacytoma with unicentric Castleman disease: A case report and review of literature

BACKGROUND

Solitary plasmacytoma and unicentric Castleman disease (UCD) are rare lymphoproliferative disorders characterized by monoclonal plasma cells and a single set of locally enlarged lymph nodes, respectively.

CASE SUMMARY

A 48-year-old Han Chinese man presented to our department with a neck mass and progressive foreign body sensation in his throat. ¹⁸F-FDG positron emission tomography revealed focally increased radioactivity centered around the hyoid, and computed tomography (CT) revealed osteolytic lesions. Histopathology revealed Castleman-like features and CD138/CD38-positive mature plasma cells. Systemic work-up ruled out the possibility of POEMS syndrome, lymphoma, and multiple myeloma, leading to a final diagnosis of solitary hyoid plasmacytoma with UCD. The patient underwent partial hyoid resection and selective neck dissection, followed by intensity-modulated radiotherapy. 99mTc-MDP single-photon emission computed tomography/CT reevaluation showed neither local recurrence nor distant bone metastasis at the 40-mo follow-up.

CONCLUSION

The diagnostic process and differential diagnosis of this rare case provided valuable educational information to clinicians.

Deciphering spatial genomic heterogeneity at a single cell resolution in multiple myeloma

Osteolytic lesions (OL) characterize symptomatic multiple myeloma. The mechanisms of how malignant plasma cells (PC) cause OL in one region while others show no signs of bone destruction despite subtotal infiltration remain unknown. We report on a single-cell RNA sequencing (scRNA-seq) study of PC obtained prospectively from random bone marrow aspirates (BM) and paired imaging-guided biopsies of OL. We analyze 148,630 PC from 24 different locations in 10 patients and observe vast inter- and intra-patient heterogeneity based on scRNA-seq analyses. Beyond the limited evidence for spatial heterogeneity from whole-exome sequencing, we find an additional layer of complexity by integrated analysis of anchored scRNA-seq datasets from the BM and OL. PC from OL are characterized by differentially expressed genes compared to PC from BM, including upregulation of genes associated with myeloma bone disease like DKK1, HGF and TIMP-1 as well as recurrent downregulation of JUN/FOS, DUSP1 and HBB. Assessment of PC from longitudinally collected samples reveals transcriptional changes after induction therapy. Our study contributes to the understanding of destructive myeloma bone disease.

Intratumor Heterogeneity of MIF Expression Correlates With Extramedullary Involvement of Multiple Myeloma

Macrophage migration inhibitory factor (MIF) has been shown to promote disease progression in many malignancies, including multiple myeloma (MM). We previously reported that MIF regulates MM bone marrow homing and knockdown of MIF favors the extramedullary myeloma formation in mice. Here, based on MIF immunostaining of myeloma cells in paired intramedullary and extramedullary biopsies from 17 patients, we found lower MIF intensity in extramedullary MM (EMM) versus intramedullary MM (IMM). Flow cytometry and histology analysis in xenograft models showed a portion of inoculated human MM cells lost their MIF expression (MIF^Low) in vivo. Of note, IMM had dominantly MIF^High cells, while EMM showed a significantly increased ratio of MIF^Low cells. Furthermore, we harvested the extramedullary human MM cells from a mouse and generated single-cell transcriptomic data. The developmental trajectories of MM cells from the MIF^High to MIF^Low state were indicated. The MIF^High cells featured higher proliferation. The MIF^Low ones were more quiescent and harbored abundant ribosomal protein genes. Our findings identified in vivo differential regulation of MIF expression in MM and suggested a potential pathogenic role of MIF in the extramedullary spread of disease.

Role and Therapeutic Targeting of SDF-1α/CXCR4 Axis in Multiple Myeloma

Simple Summary

The SDF-1α/CXCR4 axis plays crucial roles in proliferation, survival, invasion, dissemination, and drug resistance in multiple myeloma. This review summarizes the pleiotropic role of the SDF-1α/CXCR4 axis in multiple myeloma and introduces the SDF-1α/CXCR4 axis-targeted therapies in multiple myeloma.

Abstract

The C-X-C chemokine receptor type 4 (CXCR4) is a pleiotropic chemokine receptor that is expressed in not only normal hematopoietic cells but also multiple myeloma cells. Its ligand, stromal cell-derived factor 1α (SDF-1α) is produced in the bone marrow microenvironment. The SDF-1α/CXCR4 axis plays a pivotal role in the major physiological processes associated with tumor proliferation, survival, invasion, dissemination, and drug resistance in myeloma cells. This review summarizes the pleiotropic role of the SDF-1α/CXCR4 axis in multiple myeloma and discusses the future perspective in the SDF-1α/CXCR4 axis-targeted therapies in multiple myeloma.

Tumor Microenvironment Proteomics: Lessons From Multiple Myeloma

Although the "seed and soil" hypothesis was proposed by Stephen Paget at the end of the 19th century, where he postulated that tumor cells (seeds) need a propitious medium (soil) to be able to establish metastases, only recently the tumor microenvironment started to be more studied in the field of Oncology. Multiple myeloma (MM), a malignancy of plasma cells, can be considered one of the types of cancers where there is more evidence in the literature of the central role that the bone marrow (BM) microenvironment plays, contributing to proliferation, survival, migration, and drug resistance of tumor cells. Despite all advances in the therapeutic arsenal for MM treatment in the last years, the disease remains incurable. Thus, studies aiming a better understanding of the pathophysiology of the disease, as well as searching for new therapeutic targets are necessary and welcome. Therefore, the present study aimed to evaluate the protein expression profiling of mononuclear cells derived from BM of MM patients in comparison with these same cell types derived from healthy individuals, in order to fill this gap in MM treatment. Proteomic analysis was performed using the mass spectrometry technique and further analyses were done using bioinformatics tools, to identify dysregulated biological pathways and/or processes in the BM microenvironment of patients with MM as a result of the disease. Among the pathways identified in this study, we can highlight an upregulation of proteins related to protein biosynthesis, especially chaperone proteins, in patients with MM. Additionally, we also found an upregulation of several proteins involved in energy metabolism, which is one of the cancer hallmarks. Finally, with regard to the downregulated proteins, we can highlight mainly those involved in different pathways of the immune response, corroborating the data that has demonstrated that the immune system of MM is impaired and, therefore, the immunotherapies that have been studied recently for the treatment of the disease are extremely necessary in the search for a control and a cure for these patients who live with the disease.

Game of Bones: How Myeloma Manipulates Its Microenvironment

Multiple myeloma is a clonal disease of long-lived plasma cells and is the second most common hematological cancer behind Non-Hodgkin's Lymphoma. Malignant transformation of plasma cells imparts the ability to proliferate, causing harmful lesions in patients. In advanced stages myeloma cells become independent of their bone marrow microenvironment and form extramedullary disease. Plasma cells depend on a rich array of signals from neighboring cells within the bone marrow for survival which myeloma cells exploit for growth and proliferation. Recent evidence suggests, however, that both the myeloma cells and the microenvironment have undergone alterations as early as during precursor stages of the disease. There are no current therapies routinely used for treating myeloma in early stages, and while recent therapeutic efforts have improved patients' median survival, most will eventually relapse. This is due to mutations in myeloma cells that not only allow them to utilize its bone marrow niche but also facilitate autocrine pro-survival signaling loops for further progression. This review will discuss the stages of myeloma cell progression and how myeloma cells progress within and outside of the bone marrow microenvironment.

Extramedullary Disease in Multiple Myeloma

PURPOSE OF REVIEW

Extramedullary disease (EMD) is a rare but recognized manifestation of multiple myeloma (MM), characterized by involvement of several organs including skin, liver, lymphatic system, pleura, and central nervous system. The incidence is about 3-5% in newly diagnosed MM patients, but has been reported in up to 20% patients in the relapsed MM setting.

RECENT FINDINGS

Presence of EMD has been associated with more aggressive phenotype of MM, elevated serum lactate dehydrogenase (LDH) enzyme, and high-risk cytogenetics [deletion 17p, translocation (4;14), translocation (14;16)]. There are several hypotheses of how EMD occurs, including factors leading to bone marrow emancipation and hematogenous spread. The treatment schema usually follows that of high-risk MM. The current review summarizes the disease characterization data, along with available data on clinical activity of available anti-MM agents for this entity.

Carfilzomib Based Treatment Strategies in the Management of Relapsed/Refractory Multiple Myeloma with Extramedullary Disease

Published experience with carfilzomib in patients with relapsed/refractory multiple myeloma (RRMM) and extramedullary disease (EMD) is still limited. The current study aimed to assess the efficacy and safety of carfilzomib containing therapy regimens in EMD. We retrospectively analyzed 45 patients with extramedullary RRMM treated with carfilzomib from June 2013 to September 2019. The median age at the start of carfilzomib was 64 (range 40-80) years. Twenty (44%) and 25 (56%) patients had paraosseous manifestation and EMD without adjacency to bone, respectively. The serological overall response rate (ORR) was 59%. Extramedullary response was evaluable in 33 patients, nine (27%) of them achieved partial remission (PR) (ORR = 27%). In 15 (33%) patients, we observed no extramedullary response despite serological response. The median progression-free survival (PFS) and overall survival (OS) were five (95% CI, 3.5-6.5) and ten (95% CI, 7.5-12.5) months, respectively. EMD without adjacency to bone was associated with a significantly inferior PFS (p = 0.004) and OS (p = 0.04) compared to paraosseous lesions. Carfilzomib based treatment strategies showed some efficacy in heavily pretreated patients with extramedullary RRMM but could not overcome the negative prognostic value of EMD. Due to the discrepancy between serological and extramedullary response, evaluation of extramedullary response using imaging is mandatory in these patients.

Identification of Key Genes and Pathways in Myeloma side population cells by Bioinformatics Analysis

Background: Multiple myeloma (MM) is the second most common hematological malignancy, which is still incurable and relapses inevitably, highlighting further understanding of the possible mechanisms. Side population (SP) cells are a group of enriched progenitor cells showing stem-like phenotypes with a distinct low-staining pattern with Hoechst 33342. Compared to main population (MP) cells, the underlying molecular characteristics of SP cells remain largely unclear. This bioinformatics analysis aimed to identify key genes and pathways in myeloma SP cells to provide novel biomarkers, predict MM prognosis and advance potential therapeutic targets. Methods: The gene expression profile GSE109651 was obtained from Gene Expression Omnibus database, and then differentially expressed genes (DEGs) with P-value <0.05 and |log2 fold-change (FC)| > 2 were selected by the comparison of myeloma light-chain (LC) restricted SP (LC/SP) cells and MP CD138⁺ cells. Subsequently, gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis, protein-protein interaction (PPI) network analysis were performed to identify the functional enrichment analysis of the DEGs and screen hub genes. Cox proportional hazards regression was used to select the potential prognostic DEGs in training dataset (GSE2658). The prognostic value of the potential prognostic genes was evaluated by Kaplan-Meier curve and validated in another external dataset (MMRF-CoMMpass cohort from TCGA). Results: Altogether, 403 up-regulated and 393 down-regulated DEGs were identified. GO analysis showed that the up-regulated DEGs were significantly enriched in innate immune response, inflammatory response, plasma membrane and integral component of membrane, while the down-regulated DEGs were mainly involved in protoporphyrinogen IX and heme biosynthetic process, hemoglobin complex and erythrocyte differentiation. KEGG pathway analysis suggested that the DEGs were significantly enriched in osteoclast differentiation, porphyrin and chlorophyll metabolism and cytokine-cytokine receptor interaction. The top 10 hub genes, identified by the plug-in cytoHubba of the Cytoscape software using maximal clique centrality (MCC) algorithm, were ITGAM, MMP9, ITGB2, FPR2, C3AR1, CXCL1, CYBB, LILRB2, HP and FCER1G. Modules and corresponding GO enrichment analysis indicated that myeloma LC/SP cells were significantly associated with immune system, immune response and cell cycle. The predictive value of the prognostic model including TFF3, EPDR1, MACROD1, ARHGEF12, AMMECR1, NFATC2, HES6, PLEK2 and SNCA was identified, and validated in another external dataset (MMRF-CoMMpass cohort from TCGA). Conclusions: In conclusion, this study provides reliable molecular biomarkers for screening, prognosis, as well as novel therapeutic targets for myeloma LC/SP cells.

Classification of Solitary Plasmacytoma, Is it more Intricate than Presently Suggested? A Commentary

A query regarding the definition and the classification of solitary plasmacytoma is apparently still pending. The clinical course, the response to treatment and the propensity to progress to plasma cell myeloma, are all a function of the classification which must be established on a firm basis. Solitary plasmacytoma should be recognized in the continuum of the plasma cell neoplasms. Moreover, whether the solitary plasmacytoma of bone and the extramedullary type of the tumor represent two distinct disease entities, exhibiting separate biological characteristics, has not been finally established. To appraise the similarities and differences between these two types of lesion, we have scrutinized recent investigations relating their classification. A commentary highlighting our conclusions follows.

Distinct Clinical Outcomes between Paramedullary and Extramedullary Lesions in Newly Diagnosed Multiple Myeloma

This retrospective study aimed to compare the clinical features of paramedullary lesions (PLs) and extramedullary lesions (ELs) of plasmacytomas at diagnosis, using positron emission tomography integrated with computed tomography, using glucose labeled with the positron-emitting radionuclide ¹⁸F (¹⁸F-FDG-PET/CT) in newly diagnosed multiple myeloma (NDMM), and to address their prognostic impact. Sixty-four patients with NDMM presenting ELs (n=22) and/or PLs (n=42) were included. Patients with ELs at initial presentation had unfavorable laboratory parameters of calcium and lactate dehydrogenase, a higher percentage of bone marrow plasma cells, and showed a trend toward advanced international staging system (ISS), compared to patients with PLs. Using X-ray imaging, high bone disease (HBD) was observed in 50% and 71% of patients with ELs and PLs, respectively. After a median follow-up of 29.2 months (range, 3.4–76.5 months) in survivors, patients with ELs had a significantly lower overall survival (OS) (p=0.033) than patients with PLs did, whereas the progression-free survival (PFS) did not differ significantly (p=0.818). However, the PFS after 1^st progression was significantly worse in patients with ELs than in those with PLs (p=0.017). In the multivariate analyses, the negative impact of initial ELs on OS (p=0.033) was sustained. Our results demonstrated the different clinical features and outcomes of ELs and PLs in NDMM. Patients with initial ELs showed a shorter PFS after 1^st progression, which translated into poor OS, providing insight into the different biological effect of ELs.

Long non-coding RNA MALAT1 is an inducible stress response gene associated with extramedullary spread and poor prognosis of multiple myeloma

Extramedullary myeloma (EMM) occurs when myeloma develops outside the bone marrow; it often develops after chemotherapy and is associated with the acquisition of chemo-resistance and a fatal course. The mechanisms underlying extramedullary spread have not yet been fully elucidated. MALAT1 is a highly abundantly and ubiquitously expressed long non-coding RNA that plays important roles in cancer metastasis. The aims of this study were to clarify the association of MALAT1 with EMM and to elucidate the underlying mechanism of EMM formation under chemotherapeutic pressure. MALAT1 expression was significantly higher in multiple myeloma (MM) than in monoclonal gammopathy of undetermined significance. Furthermore, MALAT1 expression was markedly higher in EMM compared with that in corresponding intramedullary myeloma cells. A higher MALAT1 level was associated with shorter overall and progression-free survival. MALAT1 expression level was positively correlated with expression of HSP90AA1, HSP90AB1 and HSP90B1 but not with TP53 expression. MALAT1 was significantly upregulated by bortezomib and doxorubicin. Considering the known functions of MALAT1, our results suggest that it acts as a stress response gene that is upregulated by chemotherapy, thereby linking chemotherapy to EMM formation. Elucidating the biological implication of long non-coding RNA contributes to deeper understanding concerning the pathogenesis and investigation of novel therapeutic targets for MM.

Increased expression of the tight junction protein TJP1/ZO-1 is associated with upregulation of TAZ-TEAD activity and an adult tissue stem cell signature in carfilzomib-resistant multiple myeloma cells and high-risk multiple myeloma patients

Tight junction protein 1 (TJP1) has recently been proposed as a biomarker to identify multiple myeloma (MM) patients most likely to respond to bortezomib- and carfilzomib-based proteasome inhibitor regimens. Herein we report increased expression of TJP1 during the adaptive response mediating carfilzomib resistance in the LP-1/Cfz MM cell line. Moreover, increased TJP1 expression delineated a subset of relapsed/refractory MM patients on bortezomib-based therapy sharing an LP-1/Cfz-like phenotype characterized by activation of interacting transcriptional effectors of the Hippo signaling cascade (TAZ and TEAD1) and an adult tissue stem cell signature. siRNA-mediated knockdown of TJP1 or TAZ/TEAD1 partially sensitized LP-1/Cfz cells to carfilzomib. Connectivity Map analysis identified translation inhibitors as candidate therapeutic agents targeting this molecular phenotype. We confirmed this prediction by showing that homoharringtonine (omacetaxine mepesuccinate) — the first translation inhibitor to be approved by the U.S. Food and Drug Administration — displayed potent cytotoxic activity on LP-1/Cfz cells. Homoharringtonine treatment reduced the levels of TAZ and TEAD1 as well as the MM-protective proteins Nrf2 and MCL1. Thus, our data suggest the importance of further studies evaluating translation inhibitors in relapsed/refractory MM. On the other hand, use of TJP1 as a MM biomarker for proteasome inhibitor sensitivity requires careful consideration.

Large Plasmacytoma Occupying the Upper Limb in a Myeloma Patient

Extramedullary disease (EMD) is an issue for patients with multiple myeloma (MM), since extramedullary spread of MM is associated with an aggressive course and a poor prognosis. Moreover, the mechanism of EMD development is uncertain. Here, we present extensive extramedullary plasmacytoma occupying the left upper limb of a 66-year-old female patient with MM with an extremely aggressive course and multiple visceral organ involvement without bone marrow infiltration or plasma cell leukemia. EMD of this large size is extremely rare and this case may provide a clue for better understanding of clinical features of EMD in MM.

CD31 expression in plasmacytic/plasmablastic lesions

Although CD31 has been considered one of the better, if not the best, immunohistochemical marker of endothelial cells and thereby vascular neoplasia, it is not unequivocally specific to this group of tumors. We examined CD31 staining in 34 plasmacytic lesions including 15 plasma cell myelomas, 1 extraosseous plasmacytoma, 10 plasmablastic variants of myeloma, 5 plasmablastic non-Hodgkin lymphomas, and 3 reactive plasmacytic infiltrates. All reactive plasma cellular infiltrates, 93% of plasma cell myelomas, 80% of plasmablastic variants of myelomas, and 20% of plasmablastic non-Hodgkin lymphoma cases were CD31 positive with usually diffuse and strong membranous staining. When ERG staining was performed, none were ERG positive. Plasmablastic variant of myeloma is another large cell malignancy that has the potential to be mistaken for a poorly differentiated epithelioid vascular neoplasm if CD31 is presumed to be an explicit marker of endothelial cells.

SPARC expression in CML is associated to imatinib treatment and to inhibition of leukemia cell proliferation

Background

SPARC is a matricellular glycoprotein with growth-inhibitory and antiangiogenic activity in some cell types. The study of this protein in hematopoietic malignancies led to conflicting reports about its role as a tumor suppressor or promoter, depending on its different functions in the tumor microenvironment. In this study we investigated the variations in SPARC production by peripheral blood cells from chronic myeloid leukemia (CML) patients at diagnosis and after treatment and we identified the subpopulation of cells that are the prevalent source of SPARC.

Methods

We evaluated SPARC expression using real-time PCR and western blotting. SPARC serum levels were detected by ELISA assay. Finally we analyzed the interaction between exogenous SPARC and imatinib (IM), in vitro, using ATP-lite and cell cycle analysis.

Results

Our study shows that the CML cells of patients at diagnosis have a low mRNA and protein expression of SPARC. Low serum levels of this protein are also recorded in CML patients at diagnosis. However, after IM treatment we observed an increase of SPARC mRNA, protein, and serum level in the peripheral blood of these patients that had already started at 3 months and was maintained for at least the 18 months of observation. This SPARC increase was predominantly due to monocyte production. In addition, exogenous SPARC protein reduced the growth of K562 cell line and synergized in vitro with IM by inhibiting cell cycle progression from G1 to S phase.

Conclusion

Our results suggest that low endogenous SPARC expression is a constant feature of BCR/ABL positive cells and that IM treatment induces SPARC overproduction by normal cells. This exogenous SPARC may inhibit CML cell proliferation and may synergize with IM activity against CML.

Anti-Notch treatment prevents multiple myeloma cells localization to the bone marrow via the chemokine system CXCR4/SDF-1

Multiple myeloma (MM) is a deadly hematopoietic malignancy characterized by proliferation of malignant plasma cells in the bone marrow (BM) and bone disease. Interactions between myeloma and BM cells facilitate tumor progression and resistance to therapies. CXCR4 and its ligand Stromal cell-derived factor-1 (SDF-1) have a primary role in this process and are associated with poor prognosis. The Notch pathway is active in myeloma cells, resulting in increased proliferation, resistance to apoptosis and osteolytic activity. We hypothesized that the CXCR4/SDF-1 axis mediates the effects of Notch signals in myeloma cells. Here we show that Notch positively controls CXCR4/SDF-1 expression and functions in myeloma cell lines, and that forced CXCR4 activation partially rescues tumor cells from the outcomes of Notch inhibition. Additionally, we provide evidences that Notch blocking in vivo significantly reduces BM infiltration by human myeloma cells in mouse xenografts. This is the first evidence that a Notch-targeted approach effectively prevents MM cell migration, proliferation and resistance to apoptosis by reducing CXCR4 and SDF-1 levels.

Extramedullary multiple myeloma

Abstract Extramedullary disease (EMD), defined as a clonal plasmacytic infiltrate at anatomic sites distant from the bone marrow or adjacent soft tissue in a patient with underlying multiple myeloma, is present in a significant percentage of patients with multiple myeloma at some point during the course of their disease. The exact prevalence of EMD, however, has not been reproducibly described, with some series citing EMD in 6% of patients with myeloma, and others up to 20%. EMD is therefore an uncommon, but by no means rare, manifestation of multiple myeloma. Further observational series have suggested that EMD is a highly aggressive disease entity, with clinical behavior distinct from marrow-restricted myeloma. This article summarizes the current research on EMD and examines the opportunity for further research into the pathogenic, immunologic, cytogenetic, clinical, therapeutic and prognostic features of this hitherto poorly understood disease entity.

A phase I first-in-human study of TRC105 (Anti-Endoglin Antibody) in patients with advanced cancer

PURPOSE

TRC105 is a chimeric IgG1 monoclonal antibody that binds CD105 (endoglin). This first-in-human, phase I, open-label study assessed safety, pharmacokinetics, and antitumor activity of TRC105 in patients with advanced refractory solid tumors.

PATIENTS AND METHODS

Patients received escalating doses of intravenous TRC105 until disease progression or unacceptable toxicity using a standard 3 + 3 phase I design.

RESULTS

Fifty patients were treated with escalating doses of TRC105. The maximum tolerated dose (MTD) was exceeded at 15 mg/kg every week because of dose-limiting hypoproliferative anemia. TRC105 exposure increased with increasing dose, and continuous serum concentrations that saturate CD105 receptors were maintained at 10 mg/kg weekly (the MTD) and 15 mg/kg every 2 weeks. Common adverse events including anemia, telangiectasias, and infusion reactions reflected the mechanism of action of the drug. Antibodies to TRC105 were not detected in patients treated with TRC105 from Chinese hamster ovary cells being used in ongoing phase Ib and phase II studies. Stable disease or better was achieved in 21 of 45 evaluable patients (47%), including two ongoing responses at 48 and 18 months.

CONCLUSION

TRC105 was tolerated at 10 mg/kg every week and 15 mg/kg every 2 weeks, with a safety profile that was distinct from that of VEGF inhibitors. Evidence of clinical activity was seen in a refractory patient population. Ongoing clinical trials are testing TRC105 in combination with chemotherapy and VEGF inhibitors and as a single agent in prostate, ovarian, bladder, breast, and hepatocellular cancer.

Extramedullary disease in plasma cell myeloma: the iceberg phenomenon

Extramedullary (EM) plasmacytomas (EMPs) that are not progression of intramedullary (IM) plasma cell myeloma (PCM) are usually indolent. In contrast, EM spread of IM PCM is associated with a poor prognosis. The recently introduced Durie-Salmon PLUS staging system includes EM disease in the poor prognosis category. One study noted an increase in EM disease both at diagnosis and during follow-up of PCM in 2000-2007 compared with previous years raising concerns that adoption of novel agents (thalidomide, lenalidomide and bortezomib) and greater use of hematopoietic cell transplantation (HCT) might be contributory to this. It is uncertain if this is a true increase or merely greater detection due to the increasing use of more sensitive imaging techniques (computerized tomography, magnetic resonance imaging and ¹⁸F-fluorodeoxyglucose positron emission tomography) or a reflection of the evolving natural history of PCM in an era when patients are living longer (median overall survival before 1996 was 29.9 months vs 44.8 months after 1996). Recent studies suggest there are important biological differences between PCM with or without EM spread that are offering clues that might explain the propensity for dissemination and a more aggressive clinical course. For example, EM relapse in PCM with and without deletion 13 was 30.8 vs 5.6%, suggesting the biology of a plasma cell subclone before HCT can affect the nature of the relapse after HCT. This article will explore the clinical, biological and treatment implications of EM spread of PCM. In addition, the impact of extramedullary disease on the outcomes of autologous and allogeneic HCT for PCM will be analyzed. Allogeneic HCT early in the course of high-risk PCM with EM disease is a consideration since graft vs myeloma effects may be essential to achieve maximal survival benefits.

Soft-Tissue Plasmacytomas in Multiple Myeloma: Incidence, Mechanisms of Extramedullary Spread, and Treatment Approach

We provide an overview on soft-tissue extramedullary plasmacytomas (EMPs) in multiple myeloma (MM). We reviewed the incidence of EMPs in MM, myeloma bone marrow homing, possible mechanisms of extramedullary spread, and prognosis and response to therapy. The incidence of EMPs is 7% to 18% at MM diagnosis and up to 20% at relapse. The current notion that EMPs are more frequent after treatment with novel agents remains to be proven, especially considering that different patterns of disease recurrence can emerge as patients live longer in the era of novel drugs. Bone marrow genetic abnormalities are not associated with extramedullary spread per se, which also suggests that microenvironmental interactions are key. Possible mechanisms of extramedullary spread include decreased adhesion molecule expression and downregulation of chemokine receptors. EMPs usually show plasmablastic morphology with negative CD56 expression. High-dose therapy with autologous stem-cell transplantation (ASCT) can overcome the negative prognostic impact of extramedullary disease in younger selected patients. EMPs do not typically respond to thalidomide alone, but in contrast, responses to bortezomib have been reported. The incidence of EMPs in patients with MM is high and is associated with poor outcome in patients treated conventionally. A potential first-line treatment option seems to be a bortezomib-containing regimen followed by ASCT, whenever possible. Experimental studies on the mechanisms of myeloma cell adhesion, myeloma growth at extramedullary sites, and drug sensitivity are priorities for this area of continuing therapeutic challenge.

Dual inhibition of akt/mammalian target of rapamycin pathway by nanoparticle albumin-bound-rapamycin and perifosine induces antitumor activity in multiple myeloma

The phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway mediates multiple myeloma (MM) cell proliferation, survival, and development of drug resistance, underscoring the role of mTOR inhibitors, such as rapamycin, with potential anti-MM activity. However, recent data show a positive feedback loop from mTOR/S6K1 to Akt, whereby Akt activation confers resistance to mTOR inhibitors. We confirmed that suppression of mTOR signaling in MM cells by rapamycin was associated with upregulation of Akt phosphorylation. We hypothesized that inhibiting this positive feedback by a potent Akt inhibitor perifosine would augment rapamycin-induced cytotoxicity in MM cells. Perifosine inhibited rapamycin-induced phosphorylated Akt, resulting in enhanced cytotoxicity in MM.1S cells even in the presence of interleukin-6, insulin-like growth factor-I, or bone marrow stromal cells. Moreover, rapamycin-induced autophagy in MM.1S MM cells, as evidenced by electron microscopy and immunocytochemistry, was augmented by perifosine. Combination therapy increased apoptosis detected by Annexin V/propidium iodide analysis and caspase/poly(ADP-ribose) polymerase cleavage. Importantly, in vivo antitumor activity and prolongation of survival in a MM mouse xenograft model after treatment was enhanced with combination of nanoparticle albumin-bound-rapamycin and perifosine. Utilizing the in silico predictive analysis, we confirmed our experimental findings of this drug combination on PI3K, Akt, mTOR kinases, and the caspases. Our data suggest that mutual suppression of the PI3K/Akt/mTOR pathway by rapamycin and perifosine combination induces synergistic MM cell cytotoxicity, providing the rationale for clinical trials in patients with relapsed/refractory MM. Mol Cancer Ther; 9(4); 963-75. (c)2010 AACR.

SPARC: a matricellular regulator of tumorigenesis

Although many clinical studies have found a correlation of SPARC expression with malignant progression and patient survival, the mechanisms for SPARC function in tumorigenesis and metastasis remain elusive. The activity of SPARC is context- and cell-type-dependent, which is highlighted by the fact that SPARC has shown seemingly contradictory effects on tumor progression in both clinical correlative studies and in animal models. The capacity of SPARC to dictate tumorigenic phenotype has been attributed to its effects on the bioavailability and signaling of integrins and growth factors/chemokines. These molecular pathways contribute to many physiological events affecting malignant progression, including extracellular matrix remodeling, angiogenesis, immune modulation and metastasis. Given that SPARC is credited with such varied activities, this review presents a comprehensive account of the divergent effects of SPARC in human cancers and mouse models, as well as a description of the potential mechanisms by which SPARC mediates these effects. We aim to provide insight into how a matricellular protein such as SPARC might generate paradoxical, yet relevant, tumor outcomes in order to unify an apparently incongruent collection of scientific literature.

The molecular characterization and clinical management of multiple myeloma in the post-genome era

Cancer-causing mutations disrupt coordinated, precise programs of gene expression that govern cell growth and differentiation. Microarray-based gene-expression profiling (GEP) is a powerful tool to globally analyze these changes to study cancer biology and clinical behavior. Despite overwhelming genomic chaos in multiple myeloma (MM), expression patterns within tumor samples are remarkably stable and reproducible. Unique expression patterns associated with recurrent chromosomal translocations and ploidy changes defined molecular classes with differing clinical features and outcomes. Combined molecular techniques also dissected two distinct, reproducible forms of hyperdiploid disease and have molecularly defined MM with high risk for poor clinical outcome. GEP is now used to risk-stratify patients with newly diagnosed MM. Groups with high-risk features are evident in all GEP-defined MM classes, and GEP studies of serial samples showed that risk increases over time, with relapsed disease showing dramatic GEP shifts toward a signature of poor outcomes. This suggests a common mechanism of disease evolution and potentially reflects preferential expansion of therapy-resistant cells. Correlating GEP-defined disease class and risk with outcomes of therapeutic regimens reveals class-specific benefits for individual agents, as well as mechanistic insights into drug sensitivity and resistance. Here, we review modern genomics contributions to understanding MM pathogenesis, prognosis, and therapy.

The role of the matricellular protein SPARC in the dynamic interaction between the tumor and the host

Tumor growth is essentially the result of an evolving cross-talk between malignant and surrounding stromal cells (fibroblasts, endothelial cells and inflammatory cells). This heterogeneous mass of extracellular matrix and intermingled cells interact through cell-cell and cell-matrix contacts. Malignant cells also secrete soluble proteins that reach neighbor stromal cells, forcing them to provide the soil on which they will grow and metastasize. Different studies including expression array analysis identified the matricellular protein SPARC as a marker of poor prognosis in different cancer types. Further evidence demonstrated that high SPARC levels are often associated with the most aggressive and highly metastatic tumors. Here we describe the most recent evidence that links SPARC with human cancer progression, the controversy regarding its role in certain human cancers and the physiological processes in which SPARC is involved: epithelial-mesenchymal transition, immune surveillance and angiogenesis. Its relevance as a potential target in cancer therapy is also discussed.

The role of the matricellular protein SPARC in the dynamic interaction between the tumor and the host

Tumor growth is essentially the result of an evolving cross-talk between malignant and surrounding stromal cells (fibroblasts, endothelial cells and inflammatory cells). This heterogeneous mass of extracellular matrix and intermingled cells interact through cell-cell and cell-matrix contacts. Malignant cells also secrete soluble proteins that reach neighbor stromal cells, forcing them to provide the soil on which they will grow and metastasize. Different studies including expression array analysis identified the matricellular protein SPARC as a marker of poor prognosis in different cancer types. Further evidence demonstrated that high SPARC levels are often associated with the most aggressive and highly metastatic tumors. Here we describe the most recent evidence that links SPARC with human cancer progression, the controversy regarding its role in certain human cancers and the physiological processes in which SPARC is involved: epithelial-mesenchymal transition, immune surveillance and angiogenesis. Its relevance as a potential target in cancer therapy is also discussed.

A prototypic matricellular protein in the tumor microenvironment--where there's SPARC, there's fire

Within the tumor microenvironment is a dynamic exchange between cancer cells and their surrounding stroma. This complex biologic system requires carefully designed models to understand the role of its stromal components in carcinogenesis, tumor progression, invasion, and metastasis. Secreted protein acidic and rich in cysteine (SPARC) is a prototypic matricellular protein at the center of this exchange. Two decades of basic science research combined with recent whole genome analyses indicate that SPARC is an important player in vertebrate evolution, normal development, and maintenance of normal tissue homeostasis. Therefore, SPARC might also play an important role in the tumor microenvironment. Clinical evidence indicates that SPARC expression correlates with tumor progression, but tightly controlled animal models have shown that the role of SPARC in tumor progression is dependent on tissue and tumor cell type. In this Prospectus, we review the current understanding of SPARC in the tumor microenvironment and discuss current and future investigations of SPARC and tumor-stromal interactions that require careful consideration of growth factors, cytokines, proteinases, and angiotropic factors that might influence SPARC activity and tumor progression.

Immunohistochemical evaluation of 95 bone marrow reactive plasmacytoses

We histologically and immunohistochemically studied 95 bone marrow (BM) reactive plasmacytoses. Ten biopsies from plasma cell myeloma (PCM) patients served as a control group. In addition, we studied 10 monoclonal gammopathy of undetermined significance (MGUS) cases. Histologically, plasmacytosis varied between 5% and 25% with an interstitial pattern of plasma cell (PC) distribution being characteristically displayed. Immunohistochemically, we did not find any CD56/NCAM nor cyclin D1 expression in all biopsies (95 of 95, 100%), not even a weak, doubtful one; PCs were all polyclonal and CD138 positive. On the contrary, myeloma-associated PCs showed monoclonality for kappa- or lambda- light chain and strong CD56/NCAM immunoreactivity (8 of 10, 80%); four of them were cyclin D1 positive. Osteoblasts exhibited similar CD56/NCAM expression in both groups. Our data confirm the diagnostic utility of CD56/NCAM in the phenotypic characterization of polyclonal plasma cells, suggesting an important role of this particular immunomarker in the BM trephine study of polyclonal versus neoplastic plasmacytic infiltrations.

[Plasmacytic skin infiltration in multiple myeloma]

Authors present a case of a therapy-resistant multiple myeloma who developed plasmacytic skin infiltration in the course of the disease.

AIM

To define characteristics of skin infiltrating plasma cells, which differentiate them from those cells residing in the bone marrow in order to contribute to a better understanding of the epidermoinvasion process.

METHODS

Histidine decarboxylase is the only enzyme capable for histamine synthesis having significance in cell proliferation. Histidine decarboxylase was determined in skin samples and bone marrow slides by immunohistochemical procedures and in bone marrow cells using flow cytometry analysis.

RESULTS

The histidine decarboxylase expression of plasma cells participating in skin invasion disappeared, while that of bone marrow plasma cells remained.

CONCLUSIONS

Authors conclude that the histidine decarboxylase loss would serve as an evidence for the dedifferentiation of epidermoinvasive cells as being the result of fundamental changes in histamine metabolism. As extramedullary myeloma cells differ from those residing in the bone marrow, their therapeutical response might also be different.

Histopathologic, Immunohistochemical, and Cytologic Analysis of Feline Myeloma-Related Disorders: Further Evidence for Primary Extramedullary Development in the Cat

Feline myeloma-related disorders (MRD) are rare neoplasms of plasma cells. The multistep transformation model of myeloma in humans is based on the premise that plasma cells undergo neoplastic transformation primarily within the intramedullary compartment and that over time they become poorly differentiated and metastasize to extramedullary locations. Historically, diagnostic criteria used for human multiple myeloma have been applied to the cat, with the assumption that feline MRD commonly arises in the intramedullary compartment. Our objectives were to describe the features of feline MRD confirmed by cytology, histopathology, histochemistry, and immunohistochemistry and to categorize these tumors. A priori hypotheses were 1) tumor category predicts survival and 2) cats with well-differentiated tumors commonly have extramedullary involvement in contrast to human myeloma patients. This multicenter, retrospective study identified 26 MRD cases. There was good agreement between histopathologic and cytologic tumor categorization. Histochemistry and immunohistochemistry were shown to be valuable adjunct tests in the diagnosis of MRD. Cats with well-differentiated tumors had increased median survival relative to those with poorly differentiated tumors (254 versus 14 days). We have reported that marked extramedullary involvement at initial clinical presentation is significantly more common in the cat than in human MRD patients. In this study, we demonstrate that cats with well-differentiated tumors more commonly have extramedullary involvement than human myeloma patients with well-differentiated tumors (90% versus 20%, P < 0.0002). These results contrast strongly with the human myeloma model of primary intramedullary neoplastic transformation and suggest that primary extramedullary neoplastic transformation may be more common in feline MRD.

Calreticulin expression in the clonal plasma cells of patients with systemic light-chain (AL-) amyloidosis is associated with response to high-dose melphalan

In high doses with stem-cell transplantation, melphalan is an effective but toxic therapy for patients with systemic light-chain (AL-) amyloidosis, a protein deposition and monoclonal plasma cell disease. Melphalan can eliminate the indolent clonal plasma cells that cause the disease, an achievement called a complete response. Such a response is usually associated with extended survival, while no response (a less than 50% reduction) is not. Gene-expression studies and a stringently supervised analysis identified calreticulin as having significantly higher expression in the pretreatment plasma cells of patients with systemic AL-amyloidosis who then had a complete response to high-dose melphalan. Calreticulin is a pleiotropic calcium-binding protein found in the endoplasmic reticulum and the nucleus whose overexpression is associated with increased sensitivity to apoptotic stimuli. Real-time PCR and immunohistochemical staining also showed that expression of calreticulin was higher in the plasma cells of those with a complete response. Furthermore, wild-type murine embryonic fibroblasts were significantly more sensitive to melphalan than calreticulin knock-out murine embryonic fibroblasts. These data have important implications for understanding the activity of melphalan in plasma-cell diseases and support further investigation of calreticulin and its modulation in patients with systemic AL-amyloidosis receiving high-dose melphalan.

Efficacy and safety of bortezomib in patients with plasma cell leukemia

BACKGROUND

The prognosis of patients with plasma cell leukemia (PCL), an aggressive variant of multiple myeloma (MM), is usually poor. Bortezomib is the first proteasome inhibitor approved for the treatment of advanced MM. Currently available information regarding the role of bortezomib in PCL is scanty and derives from anecdotal, single-case reports.

METHODS

The authors conducted a retrospective survey of unselected Italian patients with primary or secondary PCL who were treated with bortezomib outside of clinical trials. Twelve evaluable patients were recorded who had received bortezomib for 1 to 6 cycles as either a single agent or variously combined with other drugs. Three patients were treated with bortezomib as frontline therapy, and 9 patients received bortezomib after 1 to 4 lines of chemotherapy, including autologous stem cell transplantation and thalidomide.

RESULTS

According to the International uniform response criteria of the International Myeloma Working Group, 5 partial responses (defined as a reduction in M-protein of >50%), 4 very good partial responses (defined as a reduction of >90% in M-protein), and 2 complete responses (defined as negative immunofixation) were achieved, for a response rate of 92%. Responses did not appear to be influenced by previous treatments or by other clinical or biologic parameters, including chromosome 13 deletion or the combination of bortezomib with other drugs. The median progression-free and overall survivals after bortezomib were 8 months and 12 months, respectively. At the time of last follow-up, 8 patients were alive 6 to 21 months after treatment with bortezomib, 4 of whom were in very good partial or complete responses. Grade 3/4 hematologic or neurologic toxicities (graded according to the Common Terminology Criteria for Adverse Events [CTCAE; version 3]) were reported to occur in 9 patients and 1 patient, respectively, whereas 6 patients experienced possible or documented infections.

CONCLUSIONS

Bortezomib appears to be an effective drug for PCL that could significantly improve the usually adverse clinical outcome of these patients.

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.

A Transgenic Mouse Model of Plasma Cell Malignancy Shows Phenotypic, Cytogenetic, and Gene Expression Heterogeneity Similar to Human Multiple Myeloma

Multiple myeloma is an incurable plasma cell malignancy for which existing animal models are limited. We have previously shown that the targeted expression of the transgenes c-Myc and Bcl-X(L) in murine plasma cells produces malignancy that displays features of human myeloma, such as localization of tumor cells to the bone marrow and lytic bone lesions. We have isolated and characterized in vitro cultures and adoptive transfers of tumors from Bcl-xl/Myc transgenic mice. Tumors have a plasmablastic morphology and variable expression of CD138, CD45, CD38, and CD19. Spectral karyotyping analysis of metaphase chromosomes from primary tumor cell cultures shows that the Bcl-xl/Myc tumors contain a variety of chromosomal abnormalities, including trisomies, translocations, and deletions. The most frequently aberrant chromosomes are 12 and 16. Three sites for recurring translocations were also identified on chromosomes 4D, 12F, and 16C. Gene expression profiling was used to identify differences in gene expression between tumor cells and normal plasma cells (NPC) and to cluster the tumors into two groups (tumor groups C and D), with distinct gene expression profiles. Four hundred and ninety-five genes were significantly different between both tumor groups and NPCs, whereas 124 genes were uniquely different from NPCs in tumor group C and 204 genes were uniquely different from NPCs in tumor group D. Similar to human myeloma, the cyclin D genes are differentially dysregulated in the mouse tumor groups. These data suggest the Bcl-xl/Myc tumors are similar to a subset of plasmablastic human myelomas and provide insight into the specific genes and pathways underlying the human disease.

Endoglin (CD 105) is expressed on endothelial cells in the primary central nervous system lymphomas and correlates with survival

Endoglin (CD105) is predominantly expressed on the cellular lineages within the vascular system and it is overexpressed on proliferating endothelial cells that participate in neoangiogenesis, with a weak or negative expression in the vascular endothelium of normal tissues. To investigate the correlation between the CD105 expression and possible prognostic markers or progression in the primary central nervous system lymphomas (PCNSLs), the present study assessed 26 cases of PCNSL by immunostaining for CD105 and CD34. Intratumoral microvessel density (IMVD) was determined in the hotspots and interfaces at a magnification of x200. According to the mean value, the patients were classified into lower-IMVD and higher-IMVD groups. When CD34 was used as a marker of angiogenesis, the survival rates of these two groups demonstrated no significant difference. In contrast, when CD105 was used as a marker of angiogenesis, the survival rate of the lower-IMVD group was significantly higher than that for the higher-IMVD group (P < 0.01). In the group of CD34-immunostained vessels, no difference was observed in IMVD between the hotspots and interfaces (P = 0.31). In the group with CD105-immunostained vessels, a greater IMVD was observed in the hotspots than in the interfaces (P < 0.01). These results suggested that the growth of PCNSLs was dependent on angiogenesis, that IMVD as determined by anti-CD105 monoclonal antibody was a reliable prognostic marker in PCNSLs, and that PCNSLs may therefore not require sufficient neoangiogenesis at the start of PCNSLs, however, it may instead require a higher rate of neoangiogenesis as they infiltrate and destroy the brain parenchyma.

Importance of the bone marrow microenvironment in inducing the angiogenic response in multiple myeloma

Tumor microenvironment is essential for tumor cell proliferation, angiogenesis, invasion and metastasis through its provision of survival signals, secretion of growth and pro-angiogenic factors, and direct adhesion molecule interactions. This review examines its importance in the induction of an angiogenic response in multiple myeloma (MM). The encouraging results of preclinical and clinical trials in which MM has been treated by targeting the tumor microenvironment are also discussed.

Angiopoietin-1 and myeloma-induced angiogenesis

Multiple myeloma (MM) is a plasma cell malignancy characterized by an increase of the bone marrow angiogenesis. Angiopoietin-1 (Ang-1) is a critical factor in the regulation of physiological and pathological vessel formation that acts by binding to a specific receptor Tie2 expressed on endothelial cells. Recent evidences indicate that human MM cells produce Ang-1 and up-regulate its receptor Tie2 in bone marrow endothelial cells. An overexpression of Ang-1 has been also found in MM cells as compared to normal plasma cells. The correlation between Ang-1 expression and BM angiogenesis, demonstrated in MM patients, and the inhibitory effect of Tie2 blocking on MM-induced vessel formation suggest that Ang-1 production by MM cells is critically involved in the angiogenic process in MM. In this review we focalize our attention on Ang-1/Tie2 system and its role in MM-induced angiogenesis.

Angiogenic switch in multiple myeloma

Angiogenesis is the hallmark of cancer. Growing evidence indicates that an imbalance between pro- and anti-angiogenic molecules triggers the angiogenic switch during tumor progression. Several molecules, able to affect vascular formation and function, are now beginning to be elucidated. Recent data indicate that angiogenesis also occurs in hematological malignancies. In multiple myeloma it has been demonstrated that patients with active disease have an increase in bone marrow angiogenesis correlated with the progression of disease and an adverse prognosis. The pathophysiology of myeloma-induced angiogenesis is complex and involves either the direct production of angiogenic molecules by myeloma cells or their induction in the microenvironment. In this review we have focalized our attention on the main factors involved in the angiogenic switch that occurs in MM patients.

Changes in gene expression profiles of multiple myeloma cells induced by arsenic trioxide (ATO): possible mechanisms to explain ATO resistance in vivo

Multiple myeloma (MM) is an incurable plasma cell malignancy marked by eventual resistance to therapy. Although arsenic trioxide (ATO) can induce apoptosis in MM cell lines, the in vivo activity of ATO in MM has been disappointing. The existence of ATO resistance mechanisms in MM can be inferred. We sought to generate hypotheses for ATO resistance by studying the gene expression profiles of MM cells that survived in culture with 0.5 micromol/l ATO. Among the 31 genes whose quantitative levels of expression (QLE) significantly increased in ATO were haem oxygenase 1 (HO-1) and metallothionein-2A (MT-2A). Among the 56 genes whose QLE were significantly decreased were genes that modulate cell cycling [BTBD2 and IGFBP7 (mac25)] and sensitivity to reactive oxygen species (ROS) (BACH2). HO-1 exerts an anti-apoptotic effect in ischaemic cells, and MT-2A chelates ATO intracellularly. Inhibition of HO-1 with tin protoporphyrin enhances ROS in MM cells in ATO, and addition of N-acetylcysteine increases MT-2A. Protective antioxidant responses occur in MM cells exposed to ATO, and may occur in stromal cells as well, and act to quench ROS and provide diffusible anti-apoptotic factors. They may also involve cysteine-rich proteins that chelate ATO and modulate redox-sensitive residues on proteins, such as nuclear factor kappa B and p53. A better understanding of ATO resistance will enable ATO to be combined with other agents for MM.