B-lymphocyte stimulator (BLyS) stimulates immunoglobulin production and malignant B-cell growth in Waldenstrom macroglobulinemia

GLI3 Is Required for M2 Macrophage Polarization and M2-Mediated Waldenström Macroglobulinemia Growth and Survival

Waldenstrom macroglobulinemia (WM) is a non-Hodgkin B-cell lymphoma, characterized by bone marrow infiltration with plasma cells and lymphocytes. The tumor microenvironment (TME) plays an important role in mediating WM cell biology, but the effects of macrophages on WM biology remains unclear. Here, we investigated the effects of macrophages on WM growth and survival and identified a novel role for transcription factor GLI3 in macrophage polarization. We found that co-culture of M0 and M2 macrophages promoted WM cell growth and survival, and co-culture WM cells with M0 macrophages induced M2-like phenotypes. Interestingly, GLI3 expression was induced in M2 macrophages (not M1), leading us to perform analysis of macrophages from mice lacking Gli3 in myeloid cells (M-Gli3-/- mice). A subset of differentially expressed genes implicated a role for GLI3 in macrophage polarization. Macrophages from M-Gli3-/- mice did not induce WM cell proliferation and reduced survival compared to M2 macrophages from WT mice. In addition, in vitro polarization of M0 macrophages from M-Gli3-/- was not able to induce M2 markers such as CD163, despite inducing iNos expression (M1 marker). Taken together, these results suggest a role for M2 macrophages in promoting WM cell growth and identify GLI3 as a modulator of macrophage polarization.

Past and present discovery of the BAFF/APRIL system - A bibliometric study from 1999 to 2023

Cytokines from the Tumour Necrosis Factor (TNF) family are important regulators of both physiological and pathological processes. The discovery of novel TNF ligands and receptors, BAFF and APRIL, have opened up new possibilities for scientists to explore the effect of these cytokines on the human immune system. The role of BAFF/APRIL system in B lymphocytes is particularly important for survival and maintenance of homeostasis. Aberrant expression of the system is associated with various immunological disorders. Hence, this study provides a comprehensive overview of the past and present BAFF/APRIL system research development in a bibliometric perspective. To our best knowledge, this is the first ever bibliometric analysis conducted focusing on the BAFF/APRIL system. A total of 1055 relevant documents were retrieved from WoSCC. Microsoft Excel, VOSviewer, and Biblioshiny of R studio were bibliometric tools used to analyse the scientific literature. From 1999, the annual publications showed an upward trend, with Journal of Immunology being the most productive journal. USA leads the race for BAFF/APRIL system research developments. Pascal Schneider, a senior researcher affiliated with University of Lausanne, Switzerland was recognised as the most productive author and institution in the BAFF/APRIL system research field. The research focus transitioned from focusing on the role of the system in B cell biology, to immunological disorders and finally to development of BAFF/APRIL targeting drugs. Despite several studies elucidating briefly the pathway mechanism of BAFF/APRIL system in B-cell selection, substantial research on the mechanism of action in disease models and T cell activation and development of immunomodulating drugs from natural origins remains largely unexplored. Therefore, future research focusing on these areas are crucial for the deeper understanding of the system in disease manifestations and progression allowing a better treatment management for various immunological disorders.

Waldenström Macroglobulinemia: Mechanisms of Disease Progression and Current Therapies

Waldenström macroglobulinemia is an indolent, B-cell lymphoma without a known cure. The bone marrow microenvironment and cytokines both play key roles in Waldenström macroglobulinemia (WM) tumor progression. Only one FDA-approved drug exists for the treatment of WM, Ibrutinib, but treatment plans involve a variety of drugs and inhibitors. This review explores avenues of tumor progression and targeted drug therapy that have been investigated in WM and related B-cell lymphomas.

B-cell maturation antigen targeting strategies in multiple myeloma treatment, advantages and disadvantages

B cell maturation antigen (BCMA), a transmembrane glycoprotein member of the tumor necrosis factor receptor superfamily 17 (TNFRSF17), highly expressed on the plasma cells of Multiple myeloma (MM) patients, as well as the normal population. BCMA is used as a biomarker for MM. Two members of the TNF superfamily proteins, including B-cell activating factor (BAFF) and A proliferation-inducing ligand (APRIL), are closely related to BCMA and play an important role in plasma cell survival and progression of MM. Despite the maximum specificity of the monoclonal antibody technologies, introducing the tumor-specific antigen(s) is not applicable for all malignancies, such as MM that there plenty of relatively specific antigens such as GPCR5D, MUC1, SLAMF7 and etc., but higher expression of BCMA on these cells in comparison with normal ones can be regarded as a relatively exclusive marker. Currently, different monoclonal antibody (mAb) technologies applied in anti-MM therapies such as daratuzumab, SAR650984, GSK2857916, and CAR-T cell therapies are some of these tools that are reviewed in the present manuscript. By the way, the structure, function, and signaling of the BCMA and related molecule(s) role in normal plasma cells and MM development, evaluated as well as the potential side effects of its targeting by different CAR-T cells generations. In conclusion, BCMA can be regarded as an ideal molecule to be targeted in immunotherapeutic methods, regarding lower potential systemic and local side effects.

Increased Production of B-Cell Activating Cytokines and Altered Peripheral B-Cell Subset Distribution during HIV-Related Classical Hodgkin Lymphoma

Simple Summary

Patients with HIV are at high risk of developing Hodgkin’s lymphoma. This is potentially due to alterations in blood circulating B-lymphocytes and their activating cytokines. We analyzed the distribution of circulating B-lymphocytes and the level of the activating cytokines IL6, IL10 and BAFF in 38 patients with HIV-related Hodgkin’s lymphoma during a 2-year follow-up. We also compared their characteristics at diagnosis with (1) pre-diagnosis serum samples and (2) samples from control HIV-infected subjects without lymphoma. We found an increase in activating cytokines in cases compared to controls. The level of activating cytokines increased in advanced lymphoma. It decreased over time during follow-up. B-lymphocytic count was similar between patients and controls, but their subset distribution differed. There was an overrepresentation of naive B-lymphocytes over memory B-lymphocytes in HIV-associated Hodgkin lymphoma patients, more pronounced in those with advanced lymphoma. Follow-up showed an increase in B-lymphocytic count with an even greater proportion of naive B-cells. Together this suggests that in HIV-infected patients, Hodgkin lymphoma is associated with an altered blood distribution of B-lymphocytic subsets and an increased production of activating cytokines. This environment may contribute to the process of tumorigenesis.

Abstract

Classical Hodgkin Lymphoma incidence increases in HIV-1-infected patients (HIV-cHL). HIV infection is associated with higher B-cell activation. Here, in 38 HIV-cHL patients from the French cohort ANRS-CO16 Lymphovir, we examined longitudinally over 24 months the serum levels of the B-cell activating cytokines IL10, IL6, and BAFF, and blood distribution of B-cell subsets. Fourteen HIV-cHL patients were also compared to matched HIV-infected controls without cHL. IL10, IL6, and BAFF levels were higher in HIV-cHL patients than in controls (p < 0.0001, p = 0.002, and p < 0.0001, respectively). Cytokine levels increased in patients with advanced-stage lymphoma compared to those with limited-stage (p = 0.002, p = 0.03, and p = 0.01, respectively). Cytokine levels significantly decreased following HIV-cHL diagnosis and treatment. Blood counts of whole B-cells were similar in HIV-cHL patients and controls, but the distribution of B-cell subsets was different with higher ratios of naive B-cells over memory B-cells in HIV-cHL patients. Blood accumulation of naive B-cells was more marked in patients with advanced cHL stages (p = 0.06). During the follow-up, total B-cell counts increased (p < 0.0001), and the proportion of naive B-cells increased further (p = 0.04). Together the results suggest that in HIV-infected patients, cHL is associated with a particular B-cell-related environment that includes increased production of B-cell-activating cytokines and altered peripheral distribution of B-cell subsets. This B-cell-related environment may fuel the process of tumorigenesis.

Post-relapse survival in Waldenstrom macroglobulinemia patients experiencing therapy failure following autologous transplantation

Waldenström macroglobulinemia (WM) is a rare B-cell lymphoproliferative malignancy. Autologous hematopoietic cell transplantation (auto-HCT) is considered in a subset of WM patients with relapsed disease. While registry data has shown a benefit for auto-HCT in relapsed WM, there is a paucity of data on outcomes of patients relapsing after auto-HCT. Eligibility criteria included adult patients with relapsed/refractory WM who underwent auto-HCT between 2007 and 2017. The primary endpoint was post-relapse overall survival (PR-OS). Secondary endpoints were to identify factors prognostic of PR-OS. Of the 48 patients with WM who underwent auto-HCT, 22 (46%) experienced relapse following auto-HCT. Median PR-OS of relapsed WM patients after auto-HCT (n = 22) was not reached (NR) (95% confidence interval [CI]: 17.5 months-NR). Among patients who relapsed <1 year versus ≥1 year from auto-HCT, the median PR-OS was 18.4 months (95%CI: 0.8-NR) months and NR (95%CI: 17.5-NR), respectively (p = 0.06). Of note, disease status at the time of transplant, CR/VGPR versus partial remission did not appear to impact PR-OS. The median PR-OS was significantly longer in patients who received ibrutinib in the post-transplant setting compared to those who did not (NR vs. 18.4 months, 95%CI: 9.1-NR, p = 0.02). On univariable analysis, the presence of complex karyotype (RR = 4.87, 95% CI = 1.22-19.53) and a higher number of prior lines of therapy (RR = 1.81, 95% CI = 1.23-2.67) were associated with a significantly higher risk of relapse. This is the only study to date that evaluated outcomes of WM patients who relapsed following auto-HCT and provides a benchmark for future trials evaluating survival following auto-HCT relapse.

Belantamab Mafodotin (GSK2857916) Drives Immunogenic Cell Death and Immune-mediated Antitumor Responses In Vivo

B-cell maturation antigen (BCMA) is an attractive therapeutic target highly expressed on differentiated plasma cells in multiple myeloma and other B-cell malignancies. GSK2857916 (belantamab mafodotin, BLENREP) is a BCMA-targeting antibody-drug conjugate approved for the treatment of relapsed/refractory multiple myeloma. We report that GSK2857916 induces immunogenic cell death in BCMA-expressing cancer cells and promotes dendritic cell activation in vitro and in vivo GSK2857916 treatment enhances intratumor immune cell infiltration and activation, delays tumor growth, and promotes durable complete regressions in immune-competent mice bearing EL4 lymphoma tumors expressing human BCMA (EL4-hBCMA). Responding mice are immune to rechallenge with EL4 parental and EL4-hBCMA cells, suggesting engagement of an adaptive immune response, immunologic memory, and tumor antigen spreading, which are abrogated upon depletion of endogenous CD8⁺ T cells. Combinations with OX40/OX86, an immune agonist antibody, significantly enhance antitumor activity and increase durable complete responses, providing a strong rationale for clinical evaluation of GSK2857916 combinations with immunotherapies targeting adaptive immune responses, including T-cell-directed checkpoint modulators.

The BCMA-Targeted Fourth-Generation CAR-T Cells Secreting IL-7 and CCL19 for Therapy of Refractory/Recurrent Multiple Myeloma

Chimeric antigen receptor (CAR) technology has revolutionized cancer treatment, particularly in malignant hematological tumors. Currently, the BCMA-targeted second-generation CAR-T cells have showed impressive efficacy in the treatment of refractory/relapsed multiple myeloma (R/R MM), but up to 50% relapse remains to be addressed urgently. Here we constructed the BCMA-targeted fourth-generation CAR-T cells expressing IL-7 and CCL19 (i.e., BCMA-7 × 19 CAR-T cells), and demonstrated that BCMA-7 × 19 CAR-T cells exhibited superior expansion, differentiation, migration and cytotoxicity. Furthermore, we have been carrying out the first-in-human clinical trial for therapy of R/R MM by use of BCMA-7 × 19 CAR-T cells (ClinicalTrials.gov Identifier: NCT03778346), which preliminarily showed promising safety and efficacy in first two enrolled patients. The two patients achieved a CR and VGPR with Grade 1 cytokine release syndrome only 1 month after one dose of CAR-T cell infusion, and the responses lasted more than 12-month. Taken together, BCMA-7 × 19 CAR-T cells were safe and effective against refractory/relapsed multiple myeloma and thus warranted further clinical study.

B-cell maturation antigen expression across hematologic cancers: a systematic literature review

B-cell maturation antigen (BCMA) plays a critical role in regulating B-cell proliferation and survival. There is evidence for BCMA expression in various hematologic malignancies, suggesting that BCMA may play an important role as a biomarker or therapeutic target in these diseases. Given advances in understanding the role of BCMA in B-cell development and the promise of BCMA as a therapeutic target, a systematic review is needed to rigorously assess the evidence for BCMA expression and identify areas of consensus and future research. The objective of this review was to summarize the evidence on BCMA protein and mRNA expression across hematologic malignancies. Using a PubMed database search up to 28 August 2019, a systematic literature review of publications reporting BCMA expression in patients with hematologic malignancies was conducted. Data from published congress abstracts presented at the American Society of Clinical Oncology and the American Society of Hematology were also searched. Studies that assessed BCMA expression (protein or mRNA) in patients of any age with hematologic malignancies were included. A total of 21 studies met inclusion criteria and were included in the review. BCMA was expressed in several hematologic malignancies, including multiple myeloma (MM), chronic lymphocytic leukemia, acute B-lymphoblastic leukemia, non-Hodgkin lymphoma (NHL), and Hodgkin lymphoma. BCMA was expressed at uniformly high levels across all 13 MM studies and at low to moderate levels in acute myeloid leukemia and acute lymphoblastic leukemia. These results suggest that BCMA is a relevant target in MM as well as in a subset of B-cell leukemia. BCMA expression in Hodgkin lymphoma and NHL varied across studies, and further research is needed to determine the utility of BCMA as an antibody target and biomarker in these diseases. Differences in sample type, timing of sample collection, and laboratory technique used may have affected the reporting of BCMA levels.

What is new in the treatment of Waldenstrom macroglobulinemia?

Waldenstrom macroglobulinemia (WM) is a rare type of non-Hodgkin lymphoma. The diagnosis of WM is established by the presence of lymphoplasmacytic lymphoma in the bone marrow or other organs, a monoclonal IgM paraproteinemia and the recurrent MYD88 L265P somatic mutation. Some patients with WM can be asymptomatic, in which case treatment is not indicated. However, most patients with WM will become symptomatic during the course of the disease, due to anemia, hyperviscosity, neuropathy, or other processes, necessitating therapy. Current treatment options for symptomatic WM patients include alkylating agents, proteasome inhibitors and anti-CD20 monoclonal antibodies. The approval of the oral Bruton tyrosine kinase (BTK) inhibitor ibrutinib alone and in combination with rituximab has expanded the treatment options for WM patients. The present Perspective would focus on exciting treatment strategies under development for WM patients, such as proteasome inhibitors (e.g., ixazomib), BTK inhibitors (e.g., acalabrutinib, zanubrutinib, vecabrutinib), BCL2 inhibitors (e.g., venetoclax), and anti-CXCR4 antibodies (e.g., ulocuplumab), among others. It is certainly an exciting time for WM therapy development with novel and promising treatment options in the horizon.

The Role of B-Cell Maturation Antigen in the Biology and Management of, and as a Potential Therapeutic Target in, Multiple Myeloma

B-cell maturation antigen (BCMA) was originally identified as a cell membrane receptor, expressed exclusively on late stage B-cells and plasma cells (PCs). Investigations of BCMA as a target for therapeutic intervention in multiple myeloma (MM) were initiated in 2007, using cSG1 as a naked antibody (Ab) as well as an Ab-drug conjugate (ADC) targeting BCMA, ultimately leading to ongoing clinical studies for previously treated MM patients. Since then, multiple companies have developed anti-BCMA-directed ADCs. Additionally, there are now three bispecific antibodies in development, which bind to both BCMA and CD3ε on T-cells. This latter binding results in T-cell recruitment and activation, causing target cell lysis. More recently, T-cells have been genetically engineered to recognize BCMA-expressing cells and, in 2013, the first report of anti-BCMA-chimeric antigen receptor T-cells showed that these killed MM cell lines and human MM xenografts in mice. BCMA is also solubilized in the blood (soluble BCMA [sBCMA]) and MM patients with progressive disease have significantly higher sBCMA levels than those responding to treatment. sBCMA circulating in the blood may limit the efficacy of these anti-BCMA-directed therapies. When sBCMA binds to B-cell activating factor (BAFF), BAFF is unable to perform its major biological function of inducing B-cell proliferation and differentiation into Ab-secreting PC. However, the use of γ-secretase inhibitors, which prevent shedding of BCMA from PCs, may improve the efficacy of these BCMA-directed therapies.

Targeting IL-6 receptor reduces IgM levels and tumor growth in Waldenström macroglobulinemia

The tumor microenvironment (TME) plays an important role in cancer cell biology and is implicated in resistance to therapy. In Waldenström macroglobulinemia (WM), a subtype of Non-Hodgkin lymphoma, the TME modulates WM biology by secreting cytokines that promote the malignant phenotype. In previous work, we have shown that TME-IL-6 promotes WM cell growth and IgM secretion in WM. Tocilizumab/Actemra is an anti-IL-6R antibody, which can competitively block IL-6 binding to the IL-6R. We investigated the efficacy of Tocilizumab in a preclinical mouse model of WM that considers the role of the TME in disease biology. Hairless SCID mice were subcutaneously implanted with BCWM.1 or RPCI-WM1 and bone marrow stromal cells. Groups of mice were treated with Tocilizumab or control antibody three times/week for 5 weeks and the effect on tumor burden and disease biology were evaluated. Although Tocilizumab had no effect on mice survival, there was a significant reduction in tumor growth rate in mice injected with RPCI-WM1 cells treated with Tocilizumab. In mice injected with BCWM.1 cells, there was a significant reduction in human IgM secretion in mice sera with Tocilizumab treatment. There was no significant change in mice weight suggesting Tocilizumab induced no toxicities to the mice. Taken together, our data found that administration of Tocilizumab to tumor bearing mice, results in a significant reduction in tumor volume and IgM secretion. Therefore, the evaluation of the role of Tocilizumab in WM patients may provide therapeutic efficacy by reducing IgM production and slowing the rate of tumor growth.

Circulatory levels of B-cell activating factor of the TNF family in patients with diabetic foot ulcer: Association with disease progression

Enhanced and prolonged expression of tumor necrosis factor alpha (TNF-α), a potent pro-inflammatory cytokine is evidenced during the chronic wound healing process of infected diabetic foot ulcer (IDFU). B-cell activating factor (BAFF) is the member of TNF-α family, which implicit in B-cell dysfunction. This study was aimed to evaluate the role of BAFF in diabetic foot ulcer (DFU) patients and to correlate its association with other family of inflammatory cytokines. Circulating levels of BAFF and other cytokines were measured in IDFU (n = 44) and non-IDFU patients (n = 40) using multiplexed bead-based cytokine immunoassay. A stepwise significant increase was observed in both circulatory BAFF and C-reactive protein (CRP) during the disease progression. The area under the receiver operating characteristic curve (AUC_ROC ) for BAFF was found to be high (0.89; [95% CI: 0.73-1.0]), when compared to CRP (0.68; [95% CI: 0.61-0.76]). Optimum diagnostic cutoff level for BAFF was found to be ≥2.35 pg/mL with 62.0% sensitivity and 85.7% specificity. Further, BAFF levels showed a significant positive correlation with CRP among IDFU patients. With respect to other family cytokines, BAFF levels were positively correlated with TNF-α, interferon family cytokines such as IFN-α2, IL-28A/IFN-λ2, IFN-γ, and IL-10 family cytokines such as IL-19, IL-22, and IL-26 and negatively correlated with IL-6 receptor family such as gp130/sIL-6Rβ. Hence, our data suggest that devising therapeutic strategies to reduce the levels of BAFF may contribute in amelioration of IDFU.

Soluble PD-1 ligands regulate T-cell function in Waldenstrom macroglobulinemia

Although immune checkpoint molecules regulate the progression of certain cancers, their significance in malignant development of Waldenstrom macroglobulinemia (WM), an incurable low-grade B-cell lymphoma, remains unknown. Recently, cytokines in the bone marrow (BM) microenvironment are shown to contribute to the pathobiology of WM. Here, we investigated the impact of cytokines, including interleukin-6 (IL-6) and IL-21, on immune regulation and particularly on the programmed death-1 (PD-1) and its ligands PD-L1 and PD-L2. We showed that IL-21, interferon γ, and IL-6 significantly induced PD-L1 and PD-L2 gene expression in WM cell lines. Increased PD-L1 and PD-L2 messenger RNA was also detected in patients' BM cells. Patients' nonmalignant BM cells, including T cells and monocytes, showed increased PD-L1, but minimal or undetectable PD-L2 surface expression. There was also very modest PD-L1 and PD-L2 surface expression by malignant WM cells, suggesting that ligands are cleaved from the cell surface. Levels of soluble ligands were higher in patients' BM plasma and blood serum than controls. Furthermore, IL-21 and IL-6 increased secreted PD-L1 in the culture media of WM cell lines, implying that elevated levels of soluble PD-1 ligands are cytokine mediated. Soluble PD-1 ligands reduced T-cell proliferation, phosphorylated extracellular signal-regulated kinase and cyclin A levels, mitochondrial adenosine triphosphate production, and spare respiratory capacity. In conclusion, we identify that soluble PD-1 ligands are elevated in WM patients and, in addition to surface-bound ligands in WM BM, could regulate T-cell function. Given the capability of secreted forms to be bioactive at distant sites, soluble PD-1 ligands have the potential to promote disease progression in WM.

Targeting B Cell Maturation Antigen (BCMA) in Multiple Myeloma: Potential Uses of BCMA-Based Immunotherapy

The approval of the first two monoclonal antibodies targeting CD38 (daratumumab) and SLAMF7 (elotuzumab) in late 2015 for treating relapsed and refractory multiple myeloma (RRMM) was a critical advance for immunotherapies for multiple myeloma (MM). Importantly, the outcome of patients continues to improve with the incorporation of this new class of agents with current MM therapies. However, both antigens are also expressed on other normal tissues including hematopoietic lineages and immune effector cells, which may limit their long-term clinical use. B cell maturation antigen (BCMA), a transmembrane glycoprotein in the tumor necrosis factor receptor superfamily 17 (TNFRSF17), is expressed at significantly higher levels in all patient MM cells but not on other normal tissues except normal plasma cells. Importantly, it is an antigen targeted by chimeric antigen receptor (CAR) T-cells, which have already shown significant clinical activities in patients with RRMM who have undergone at least three prior treatments, including a proteasome inhibitor and an immunomodulatory agent. Moreover, the first anti-BCMA antibody–drug conjugate also has achieved significant clinical responses in patients who failed at least three prior lines of therapy, including an anti-CD38 antibody, a proteasome inhibitor, and an immunomodulatory agent. Both BCMA targeting immunotherapies were granted breakthrough status for patients with RRMM by FDA in Nov 2017. Other promising BCMA-based immunotherapeutic macromolecules including bispecific T-cell engagers, bispecific molecules, bispecific or trispecific antibodies, as well as improved forms of next generation CAR T cells, also demonstrate high anti-MM activity in preclinical and even early clinical studies. Here, we focus on the biology of this promising MM target antigen and then highlight preclinical and clinical data of current BCMA-targeted immunotherapies with various mechanisms of action. These crucial studies will enhance selective anti-MM response, transform the treatment paradigm, and extend disease-free survival in MM.

B-cell activating factor deficiency suppresses splenomegaly during Leishmania donovani infection

B-cell activating factor (BAFF) is a critical regulator for B-cell development and differentiation. We previously reported elevation of serum BAFF levels in patients with visceral leishmaniasis (VL). In this study, we examined if BAFF is involved in pathologies during infection of Leishmania donovani. BALB/cA mice infected with L. donovani showed significant elevation in serum BAFF and IgG levels as seen in VL patients. In contrast, elevation of serum IgG by L. donovani infection was significantly suppressed in BAFF-deficient mice. The spleen weight of the BAFF-deficient mice after infection was significantly lower than that of the infected wild-type mice, whereas comparable degree of hepatomegaly and anemia were observed in those mice. In the enlarged spleen of L. donovani-infected wild-type mice, increase of CD19⁺ lymphocytes was more prominent than that of CD3⁺ cells, suggesting the contribution of B cell increase to splenomegaly during VL. Besides, increase of CD19⁺ lymphocytes was not found in BAFF-deficient mice after L. donovani infection. Taken together, these results suggest that BAFF is involved in strong B cell activation, which has a pathological role in splenomegaly but not in hepatomegaly or anemia, during VL.

Novel Molecular Mechanism of Regulation of CD40 Ligand by the Transcription Factor GLI2

The interaction between tumor cells and their surrounding microenvironment is essential for the growth and persistence of cancer cells. This interaction is mediated, in part, by cytokines. Although the role of cytokines in normal and malignant cell biology is well established, many of the molecular mechanisms regulating their expression remain elusive. In this article, we provide evidence of a novel pathway controlling the transcriptional activation of CD40L in bone marrow-derived stromal cells. Using a PCR-based screening of cytokines known to play a role in the biology of bone marrow malignancies, we identified CD40L as a novel GLI2 target gene in stromal cells. CD40L plays an important role in malignant B cell biology, and we found increased Erk phosphorylation and cell growth in malignant B cells cocultured with CD40L-expressing stromal cells. Further analysis indicated that GLI2 overexpression induced increased CD40L expression, and, conversely, GLI2 knockdown reduced CD40L expression. Using luciferase and chromatin immunoprecipitation assays, we demonstrate that GLI2 directly binds and regulates the activity of the CD40L promoter. We found that the CCR3-PI3K-AKT signaling modulates the GLI2-CD40L axis, and GLI2 is required for CCR3-PI3K-AKT-mediated regulation of the CD40L promoter. Finally, coculture of malignant B cells with cells stably expressing human CD40L results in increased Erk phosphorylation and increased malignant B cell growth, indicating that CD40L in the tumor microenvironment promotes malignant B cell activation. Therefore, our studies identify a novel molecular mechanism of regulation of CD40L by the transcription factor GLI2 in the tumor microenvironment downstream of CCR3 signaling.

Targeting cell adhesion and homing as strategy to cure Waldenström's macroglobulinemia

Most B-cell malignancies strictly depend on signals from the microenvironment for their survival and proliferation. This niche-dependency can be regarded as their Achilles' heel and provides an excellent target for therapy. Waldenström's macroglobulinemia (WM) is characterized by the accumulation of neoplastic post-germinal center B cells within the bone marrow (BM). Interestingly, one third of the patients carry activating mutations in the chemokine receptor CXCR4, a key mediator of B cell and plasma cell homing to the BM. We have previously shown that signals from the B-cell antigen receptor (BCR) and from chemokine receptors play a central role in controlling the interaction of normal and malignant B cells with their microenvironment by regulating the activity of integrin adhesion molecules. Apart from controlling the homing and retention of lymphocytes within their growth- and survival niches, integrins also emit signals that directly promote cell growth and survival. By analogy to the successful treatment with BTK inhibitors, we propose that targeting pathways controlling integrin-mediated retention of the WM cells in the BM, thereby inducing 'homelessness' (anoikis) by mobilization of the malignant cells from their protective niches, may be an efficient treatment strategy for WM.

Inhibiting TLR9 and other UNC93B1-dependent TLRs paradoxically increases accumulation of MYD88L265P plasmablasts in vivo

The MYD88(L265P) mutation is found in 2% to 10% of chronic lymphocytic leukemia, 29% of activated B-cell type diffuse large B-cell lymphoma and 90% of Waldenström macroglobulinemia, making it conceptually attractive to treat these malignancies with inhibitors of endosomal Toll-like receptors (TLR9, TLR7) that activate MYD88. Here we show that genetic inhibition of endosomal TLRs has the opposite effect on accumulation of MYD88(L265P) B cells in vitro and in vivo. Activated mature B cells from wild-type, Unc93b1(3d/3d)-mutant, or Tlr9-deficient mice were transduced with retrovirus encoding MYD88(L265P) and analyzed either in vitro or after transplantation into Rag1(-/-) recipient mice. Unc93b1(3d/3d) mutation, which blocks TLR9 and TLR7 signaling, or Tlr9 deficiency suppressed MYD88(L265P) B-cell growth in vitro but paradoxically increased in vivo accumulation of MYD88(L265P) B cells as CD19(low) plasmablasts by 10- to 100-fold. These results reveal an unexpected, powerful inhibitory effect of TLR9 on MYD88(L265P) B-cell proliferation and differentiation that appears independent of TLR7, and they provide a preclinical indicator for caution in clinical trials of TLR7/9 inhibitors for MYD88(L265P) B-cell malignancies.

Modulation of the IL-6 Receptor α Underlies GLI2-Mediated Regulation of Ig Secretion in Waldenström Macroglobulinemia Cells

Ig secretion by terminally differentiated B cells is an important component of the immune response to foreign pathogens. Its overproduction is a defining characteristic of several B cell malignancies, including Waldenström macroglobulinemia (WM), where elevated IgM is associated with significant morbidity and poor prognosis. Therefore, the identification and characterization of the mechanisms controlling Ig secretion are of great importance for the development of future therapeutic approaches for this disease. In this study, we define a novel pathway involving the oncogenic transcription factor GLI2 modulating IgM secretion by WM malignant cells. Pharmacological and genetic inhibition of GLI2 in WM malignant cells resulted in a reduction in IgM secretion. Screening for a mechanism identified the IL-6Rα (gp80) subunit as a downstream target of GLI2 mediating the regulation of IgM secretion. Using a combination of expression, luciferase, and chromatin immunoprecipitation assays we demonstrate that GLI2 binds to the IL-6Rα promoter and regulates its activity as well as the expression of this receptor. Additionally, we were able to rescue the reduction in IgM secretion in the GLI2 knockdown group by overexpressing IL-6Rα, thus defining the functional significance of this receptor in GLI2-mediated regulation of IgM secretion. Interestingly, this occurred independent of Hedgehog signaling, a known regulator of GLI2, as manipulation of Hedgehog had no effect on IgM secretion. Given the poor prognosis associated with elevated IgM in WM patients, components of this new signaling axis could be important therapeutic targets.

Factors regulating immunoglobulin production by normal and disease-associated plasma cells

Immunoglobulins are molecules produced by activated B cells and plasma cells in response to exposure to antigens. Upon antigen exposure, these molecules are secreted allowing the immune system to recognize and effectively respond to a myriad of pathogens. Immunoglobulin or antibody secreting cells are the mature form of B lymphocytes, which during their development undergo gene rearrangements and selection in the bone marrow ultimately leading to the generation of B cells, each expressing a single antigen-specific receptor/immunoglobulin molecule. Each individual immunoglobulin molecule has an affinity for a unique motif, or epitope, found on a given antigen. When presented with an antigen, activated B cells differentiate into either plasma cells (which secrete large amounts of antibody that is specific for the inducing antigen), or memory B cells (which are long-lived and elicit a stronger and faster response if the host is re-exposed to the same antigen). The secreted form of immunoglobulin, when bound to an antigen, serves as an effector molecule that directs other cells of the immune system to facilitate the neutralization of soluble antigen or the eradication of the antigen-expressing pathogen. This review will focus on the regulation of secreted immunoglobulin by long-lived normal or disease-associated plasma cells. Specifically, the focus will be on signaling and transcriptional events that regulate the development and homeostasis of long-lived immunoglobulin secreting plasma cells.

Elevation of serum B-cell activating factor levels during visceral leishmaniasis

Elevation of serum B-cell activating factor (BAFF) is one of the characteristics of immunological disorders, including autoimmunity, but the levels of BAFF in infectious diseases have not been studied well. Here, we showed the elevation of serum BAFF in patients with visceral leishmaniasis (VL). The mean serum BAFF value in VL patients (4.65 ng/mL) was 4.3 times higher than that of healthy controls (1.08 ng/mL), and 90% of VL patients showed serum BAFF above the cutoff that was calculated as the mean + 3 SDs of the controls. This report is the first on elevation of serum BAFF during VL.

Regulatory roles of the tumor necrosis factor receptor BCMA

B cell maturation antigen (BCMA) is a tumor necrosis family receptor (TNFR) member that is predominantly expressed on terminally differentiated B cells and, upon binding to its ligands B cell activator of the TNF family (BAFF) and a proliferation inducing ligand (APRIL), delivers pro-survival cell signals. Thus, BCMA is mostly known for its functional activity in mediating the survival of plasma cells that maintain long-term humoral immunity. The expression of BCMA has also been linked to a number of cancers, autoimmune disorders, and infectious diseases that suggest additional roles for BCMA activity. Despite recent advances in our understanding of the roles for the related TNFR members BAFF-R and transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI), the signaling pathway used by BCMA for mediating plasma cell survival as well as its putative function in certain disease states are not well understood. By examining the expression, regulation, and signaling targets of BCMA, we may gain further insight into this receptor and how it operates within cells in both health and disease. This information is important for identifying new therapeutic targets that may be relevant in treating diseases that involve the BAFF/APRIL cytokine network.

B cell activating factor inhibition impairs bacterial immunity by reducing T cell-independent IgM secretion

B cell activating factor of the tumor necrosis factor family (BAFF) is an essential survival factor for B cells and has been shown to regulate T cell-independent (TI) IgM production. During Ehrlichia muris infection, TI IgM secretion in the spleen was BAFF dependent, and antibody-mediated BAFF neutralization led to an impairment of IgM-mediated host defense. The failure of TI plasmablasts to secrete IgM was not a consequence of alterations in their generation, survival, or early differentiation, since all occurred normally in infected mice following BAFF neutralization. Gene expression characteristic of plasma cell differentiation was also unaffected by BAFF neutralization in vivo, and except for CD138, plasmablast cell surface marker expression was unaffected. IgM was produced, since it was detected intracellularly, and impaired secretion was not due to a failure to express the IgM secretory exon. Addition of BAFF to plasmablasts in vitro rescued IgM secretion, suggesting that BAFF signaling can directly regulate secretory processes. Our findings indicate that BAFF signaling can modulate TI host defense by acting at a late stage in B cell differentiation, via its regulation of terminal plasmablast differentiation and/or IgM secretion.

A single-arm, phase II study of the anti-Blys monoclonal antibody belimumab in symptomatic Waldenstrom macroglobulinemia

BACKGROUND

The B-lymphocyte stimulator (BLYS) protein is known to regulate immunoglobulin in normal B cells, and be overexpressed in B-cell malignancies, including Waldenstrom macroglobulinemia (WM).

PATIENTS AND METHODS

This trial evaluated the safety and activity of belimumab, a monoclonal antibody targeting BLYS, in 12 patients with WM in a single-arm phase II study.

RESULTS

Ten patients had stable disease with therapy, although no objective responses were seen. Correlative studies showed patients to have low or undetectable baseline serum levels of BLYS, with the administration of belimumab having no effect on B-cell numbers.

CONCLUSION

Belimumab cannot be recommended as a single-agent therapy for the treatment of symptomatic WM, although further evaluation in combination with other agents would be justified.

The bone marrow microenvironment in Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a lymphoplasmacytic lymphoma characterized by widespread involvement of the bone marrow (BM). The BM microenvironment serves as not only a site for disease involvement, but it also appears that the interaction of WM cells with the BM is essential for the pathogenesis of WM. The BM microenvironment consists of the cellular and noncellular compartments. The BM has been shown to regulate cell proliferation, cell cycle, and drug resistance as well as cell dissemination and cell trafficking of WM cells. A better understanding of the role of the BM microenvironment in the pathogenesis of WM can help guide better therapeutic strategies that can target the tumor clone and also regulate the BM microenvironment.

IL-21 in the bone marrow microenvironment contributes to IgM secretion and proliferation of malignant cells in Waldenstrom macroglobulinemia

Cytokines within the tumor microenvironment play an important role in supporting the growth and survival of B-cell malignancies. One such cytokine, IL-21, promotes the growth of myeloma and Hodgkin lymphoma cells while inducing apoptosis in chronic lymphocytic leukemia. However, the biologic significance of IL-21 has not been examined in Waldenstrom macroglobulinemia (WM), a B-cell lymphoma characterized by elevated serum IgM and a lymphoplasmacytic bone marrow infiltrate. We report here on the presence of IL-21 in the bone marrow of patients with WM and have identified activated T cells as the source of this cytokine. We readily detected the IL-21 receptor on malignant WM B cells and show that IL-21 significantly increases both IgM secretion and cellular proliferation of these cells with no effect on viability. IL-21 rapidly induces phosphorylation of STAT3 in WM cells, and treatment of the WM cell line MWCL-1 with a STAT3 inhibitor abolished the IL-21-mediated increases in cellular proliferation and IgM secretion. IL-21 also increased the expression of known STAT3 targets involved in B-cell differentiation, including BLIMP-1, XBP-1, IL-6, and IL-10. Overall, our data indicate that IL-21 in the bone marrow microenvironment significantly affects the biology of WM tumor cells through a STAT3-dependent mechanism.

Serum B-cell maturation antigen is elevated in multiple myeloma and correlates with disease status and survival

Although TNFRSF17 (also designated as B-cell maturation antigen (BCMA)) is expressed on tumour cells in B-cell malignancies, it has not been found in serum. The present study found that BCMA concentrations were higher in the supernatants of cultured bone marrow mononuclear cells from multiple myeloma (MM) patients than in healthy subjects. Serum BCMA levels were measured in samples from MM patients (n = 209), monoclonal gammopathy of undetermined significance (MGUS) individuals (n = 23) and age-matched controls (n = 40). BCMA was detected in the serum of untreated MM patients (n = 50) and levels were higher than in MGUS patients (P = 0·0157) and healthy subjects (P < 0·0001). Serum BCMA levels were higher among patients with progressive disease (n = 80) compared to those with responsive disease (n = 79; P = 0·0038). Among all MM patients, overall survival was shorter among patients whose serum BCMA levels were above the median (P = 0·001). We also demonstrated that sera from mice with human MM xenografts contained human BCMA, and levels correlated with the change in tumour volume in response to melphalan or cyclophosphamide with bortezomib. These results suggest that serum BCMA levels may be a new biomarker for monitoring disease status and overall survival of MM patients.

Cytokines as regulators of proliferation and survival of healthy and malignant peripheral B cells

Adaptive immunity depends on the production and maintenance of a pool of mature peripheral lymphocytes throughout life. The signals regulating the survival of mature splenic B cells have become a major focus in recent studies of B cell immunology. Lasting B cell persistence in the periphery is dependent on survival signals that are transduced by cell surface receptors. Cytokines have been shown to play a critical role in maintaining lymphocyte homeostasis. This review focuses on the role of cytokines and their receptors in the regulation of peripheral B cell survival, with an emphasis on those that have received relatively less attention in the literature.

Serum BAFF levels are related to angiogenesis and prognosis in patients with multiple myeloma

B-cell activating factor (BAFF) is a B-cell growth factor. We measured its serum levels and correlated them with parameters of disease activity, as serum levels of tumor necrosis factor-α and lactate dehydrogenase, bone marrow microvascular density and proliferating cell nuclear antigen expression, in 50 myeloma patients, in 22 of them in plateau phase and in 20 controls. All of them were higher in patients and in advanced disease while reduced in plateau phase. BAFF correlated with all the above markers. Higher BAFF levels predicted a shorter survival, suggesting an important prognostic marker and a possible therapeutic target in myeloma.

New insights into the pathogenesis and treatment of Waldenstrom macroglobulinemia

PURPOSE OF REVIEW

Waldenstrom macroglobulinemia is a distinct low-grade lymphoproliferative disease. There have been recent significant advances in understanding the underlying pathogenesis of this disease, including genetic and epigenetic regulators of tumor progression.

RECENT FINDINGS

Current studies have shown that the tumor microenvironment plays a critical role in cell proliferation, dissemination, and drug resistance.

SUMMARY

This review provides an update of the advances in the pathogenesis of factors both intrinsic (in the tumor clone) and extrinsic (in the bone marrow microenvironment) that regulate tumor progression in Waldenstrom macroglobulinemia. We next discuss novel agents that have been recently tested in clinical trials based on the advances observed in the pathogenesis of Waldenstrom macroglobulinemia.

Comprehensive analysis of tumor microenvironment cytokines in Waldenstrom macroglobulinemia identifies CCL5 as a novel modulator of IL-6 activity

Although proinflammatory and chemotactic cytokines can profoundly affect the tumor microenvironment, and many of them have been shown to have therapeutic efficacy in preclinical models, the role of these molecules in Waldenström macroglobulinemia (WM) remains poorly understood. In this study, simultaneous analysis of WM patient sera and bone marrow biopsies identified a set of dysregulated cytokines including CCL5, G-CSF, and soluble IL-2 receptor, that were significantly elevated in WM patients whereas IL-8 and EGF levels were significantly lower in these patients compared with healthy controls. Interestingly, CCL5 levels positively correlated with features of disease aggressiveness such as elevated IgM levels and bone marrow involvement. Functional analysis of tumor microenvironment revealed a functional correlation between CCL5 levels and IL-6 levels, a proinflammatory cytokine with an important role in normal and malignant B-cell biology. Furthermore, CCL5 stimulated IL-6 secretion in WM stromal cells resulting in increased IgM secretion by WM malignant cells via the JAK/STAT signaling pathway. Thus, together these results define a novel signaling network in the WM tumor microenvironment controlling IgM secretion and suggest CCL5 as a potential target for the treatment of this disease.

Phase I study of atacicept in relapsed/refractory multiple myeloma (MM) and Waldenström's macroglobulinemia

Atacicept, a specific inhibitor of BLys and APRIL, was used in a phase I study for 14 patients with myeloma (MM) and 4 with Waldenström's macroglobulinemia (WM). They received 1 cycle of 5 once-weekly s.c. injections, followed by an extension if in stable disease or in response. The maximum tolerated dose was not identified. Of 11 patients with MM who completed initial treatment, 5 patients were progression-free after cycle 1 and 4 patients were progression-free after extended therapy. Of 4 patients with WM, 3 patients were progression-free after cycle 1. Polyclonal immunoglobulin isotypes and total B cells were reduced. Plasma concentrations of soluble CD 138 decreased. Biological effect was more pronounced in WM. Of the 16 patients tested at baseline, 13 had measurable levels of free APRIL (≥25 ng/mL). In this small series, no correlations were apparent between baseline levels of free APRIL and biological or clinical response criteria.

Establishment and characterization of a novel Waldenstrom macroglobulinemia cell line, MWCL-1

Waldenström macroglobulinemia (WM) is a rare, lymphoplasmacytic lymphoma characterized by hypersecretion of immunoglobulin M (IgM) protein and tumor infiltration into the bone marrow and lymphatic tissue. Our understanding of the mechanisms driving the development and progression of WM is currently by the shortage of representative cell models available for study. We describe here the establishment of a new WM cell line, MWCL-1. Comprehensive genetic analyses have unequivocally confirmed a clonal relationship between this novel cell line and the founding tumor. MWCL-1 cells exhibit an immunophenotype consistent with a diverse, tumor clone composed of both small B lymphocytes and larger lymphoplasmacytic cells and plasma cells: CD3⁻, CD19⁺, CD20⁺, CD27⁺, CD38⁺, CD49D⁺, CD138⁺, cIgM⁺, and κ⁺. Cytogenetic studies identified a monoallelic deletion of 17p13 (TP53) in both the cell line and the primary tumor. Direct DNA resequencing of the remaining copy of TP53 revealed a missense mutation at exon 5 (V143A, GTG>GCG). In accordance with primary WM tumors, MWCL-1 cells retain the ability to secrete high amounts of IgM protein in the absence of an external stimulus. The genetic, immunophenotypic, and biologic data presented here confirm the validity of the MWCL-1 cell line as a representative model of WM.

Atacicept in relapsed/refractory multiple myeloma or active Waldenström's macroglobulinemia: a phase I study

Background:

Advanced multiple myeloma (MM) and Waldenström's macroglobulinemia (WM) are incurable B-cell malignancies. This is the first full clinical report of atacicept, a fusion protein that binds to and neutralises the B-cell survival factors, B-lymphocyte stimulator (BLyS) and A proliferation-inducing ligand (APRIL), in MM and WM.

Methods:

In this open-label phase-I study, 16 patients with advanced disease (12 MM, 4 WM) received one cycle of five once-weekly subcutaneous injections of atacicept (2, 4, 7 or 10 mg kg⁻¹). Patients with stable disease after cycle 1 entered an extension study (either two additional cycles (2, 4 and 7 mg kg⁻¹ cohorts) or 15 consecutive weekly injections of atacicept 10 mg kg⁻¹).

Results:

Atacicept was well tolerated, systemically and locally; the maximum tolerated dose was not identified. Of 11 patients with MM who completed initial treatment, five patients were progression-free after cycle 1 and four patients were progression-free after extended therapy. Of four patients with WM, three patients were progression-free after cycle 1. Consistent with atacicept's mechanism of action, polyclonal immunoglobulin isotypes and total B cells were reduced. Bone-marrow density, myeloma cell numbers and plasma concentrations of soluble CD138 also decreased.

Conclusion:

Atacicept is well tolerated in patients with MM and WM, and shows clinical and biological activity consistent with its mechanism of action.

Waldenstrom's macroglobulinemia: Recent advances in biology and therapy

Waldenstrom's macroglobulinemia (WM) is a B-cell disorder characterized by bone marrow infiltration with clonal lymphoplasmacytic cells (LPCs), along with an immunoglobulin M monoclonal gammopathy. Recent studies have led to several insights into disease biology as well as the development of an international staging system. Patients with asymptomatic macroglobulinemia should be observed without therapy. Options for frontline therapy include alkylating agents, nucleoside analogs, and rituximab, either as monotherapy or in combination. Although objective responses are common, complete remissions are infrequent. Several novel agents including proteasome inhibitors and thalidomide, as well as high-dose chemotherapy and stem cell transplantation are being incorporated into the therapeutic armamentarium in WM and show promising activity. This report provides an update on recent advances in biology and treatment of this disease.

Cytokines in the microenvironment of Waldenström's macroglobulinemia

Waldenström's macroglobulinemia (WM) is a lymphoplasmacytic lymphoma characterized by the overproduction of a monoclonal IgM protein that accumulates in the serum. Although the pathologic findings in this disease entity are reasonably well defined, the mechanisms that regulate malignant B-cell growth and monoclonal protein synthesis are less well understood. Cytokines are known to regulate many biologic processes in normal lymphocyte development including immunoglobulin production, and the presence of cytokines within the tumor microenvironment of WM is likely to contribute to malignant cell growth and survival as well as immunoglobulin production. Several studies have suggested that cytokines are potentially dysregulated in WM, however the precise role played by cytokines in WM biology is not clearly defined. This report therefore highlights our current understanding of the role of cytokines in the microenvironment of WM and how they affect malignant cell persistence and function in the bone marrow of patients.

Expression and localization of rabbit B-cell activating factor (BAFF) and its specific receptor BR3 in cells and tissues of the rabbit immune system

Rabbits are widely used for vaccine development, and investigations of human infectious and autoimmune diseases such as Systemic Lupus Erythematosus (SLE). For these applications, we cloned, sequenced and expressed rabbit B-cell Activating Factor (BAFF), and localized BAFF in cells and tissues of the rabbit immune system. The rabbit homolog of the human BAFF binding site (miniBR3 peptide) within the BAFF-specific receptor BR3 was synthesized. This 26-residue core domain binds to recombinant rabbit BAFF protein. Flow cytometric analyses using purified recombinant rabbit BAFF combined with real-time PCR findings revealed that BAFF detected on peripheral blood B-cells from normal rabbits is probably complexed to BAFF receptors rather than produced by the B-cells. BAFF was detected in developing appendix of young rabbits by immunohistochemical staining suggesting that BAFF plays a role during the period following birth when rabbit B-cell development and pre-immune antibody repertoire diversification and selection is occurring.

APRIL is overexpressed in cancer: link with tumor progression

Background

BAFF and APRIL share two receptors – TACI and BCMA – and BAFF binds to a third receptor, BAFF-R. Increased expression of BAFF and APRIL is noted in hematological malignancies. BAFF and APRIL are essential for the survival of normal and malignant B lymphocytes, and altered expression of BAFF or APRIL or of their receptors (BCMA, TACI, or BAFF-R) have been reported in various B-cell malignancies including B-cell non-Hodgkin's lymphoma, chronic lymphocytic leukemia, Hodgkin's lymphoma, multiple myeloma, and Waldenstrom's macroglobulinemia.

Methods

We compared the expression of BAFF, APRIL, TACI and BAFF-R gene expression in 40 human tumor types – brain, epithelial, lymphoid, germ cells – to that of their normal tissue counterparts using publicly available gene expression data, including the Oncomine Cancer Microarray database.

Results

We found significant overexpression of TACI in multiple myeloma and thyroid carcinoma and an association between TACI expression and prognosis in lymphoma. Furthermore, BAFF and APRIL are overexpressed in many cancers and we show that APRIL expression is associated with tumor progression. We also found overexpression of at least one proteoglycan with heparan sulfate chains (HS), which are coreceptors for APRIL and TACI, in tumors where APRIL is either overexpressed or is a prognostic factor. APRIL could induce survival or proliferation directly through HS proteoglycans.

Conclusion

Taken together, these data suggest that APRIL is a potential prognostic factor for a large array of malignancies.

Endoplasmic reticulum stress is a target for therapy in Waldenstrom macroglobulinemia

Waldenstrom macroglobulinemia (WM) is an incurable low-grade lymphoma characterized by bone marrow (BM) involvement of IgM secreting lymphoplasmacytic cells. The induction of unfolded protein response (UPR) genes ("physiologic" UPR) enables cells to differentiate into professional secretory cells capable of production of high amounts of endoplasmic reticulum (ER)-processed proteins, such as immunoglobulins. Ultimately, the initially cytoprotective UPR triggers an apoptotic cascade if ER stress is not corrected, called proapoptotic/terminal UPR. We show that WM cells inherently express the physiologic UPR machinery compared with normal BM cells, and that increased ER stress leads to proapoptotic/terminal UPR in WM cells. We therefore examined tunicamycin, ER stress inducer, for potential antitumor effects in WM. Tunicamycin induced significant cytotoxicity, apoptosis and cell-cycle arrest, and inhibited DNA synthesis in WM cell lines and primary BM CD19(+) cells from patients with WM with an inhibitory concentration (IC(50)) of 0.5 microg/mL to 1 microg/mL, but not in healthy donor cells. Importantly, coculture of WM cells in the context of the BM microenvironment did not inhibit tunicamycin-induced cytotoxicity. Finally, we demonstrate that ER stress inducer synergizes with other agents used in the treatment of WM. These preclinical studies provide a framework for further evaluation of ER stress inducing agents as therapeutic agents in WM.

Waldenstrom macroglobulinemia

In the past years, new developments have occurred both in the understanding of the biology of Waldenstrom Macroglobulinemia (WM) and in therapeutic options for WM. WM is a B-cell disorder characterized primarily by bone marrow infiltration with lymphoplasmacytic cells, along with demonstration of an IgM monoclonal gammopathy. Despite advances in therapy, WM remains incurable, with 5-6 years median overall survival of patients in symptomatic WM. Therapy is postponed for asymptomatic patients, and progressive anemia is the most common indication for initiation of treatment. The main therapeutic options include alkylating agents, nucleoside analogues, and rituximab. Studies involving combination chemotherapy are ongoing, and preliminary results are encouraging. No specific agent or regimen has been shown to be superior to another for treatment of WM. As such, novel therapeutic agents are needed for the treatment of WM. In ongoing efforts, we and others have sought to exploit advances made in the understanding of the biology of WM so as to better target therapeutics for this malignancy. These efforts have led to the development of several novel agents including the proteasome inhibitor bortezomib, and several Akt/mTor inhibitors, perifosine and Rad001, and immunomodulatory agents such as thalidomide and lenalidomide. Studies with monoclonal antibodies are ongoing and promising including the use of alemtuzumab, SGN-70, and the APRIL/BLYS blocking protein TACI-Ig atacicept. Other agents currently being tested in clinical trials include the PKC inhibitor enzastaurin, the natural product resveratrol, as well as the statin simvastatin. This report provides an update of the current preclinical studies and clinical efforts for the development of novel agents in the treatment of WM.

Lymphoma cell adhesion-induced expression of B cell-activating factor of the TNF family in bone marrow stromal cells protects non-Hodgkin's B lymphoma cells from apoptosis

This study explores whether lymphoma cell adhesion-induced B cell-activating factor (BAFF) expression in bone marrow stromal cells (BMSCs) protects B lymphoma cells from apoptosis. We first showed protection of lymphoma cells from apoptosis by conditioned medium of a stromal cell-lymphoma cell coculture, either spontaneous or induced by mitoxantrone, implying a role for soluble factor(s) in lymphoma cell survival. Addition of BAFF counteracted mitoxantrone-induced apoptosis and elicited a reduction in spontaneous apoptosis in primary lymphomas, suggesting a role of BAFF in sustaining B-cell survival. Abundant BAFF was detected in the BMSC cell line (HS-5) and primary BMSCs by flow cytometry, RT-PCR and immunoblotting. BAFF levels were 20- to 200-fold higher in BMSCs than in lymphoma cells, and lymphoma cell adhesion to BMSCs augmented BAFF secretion twofold through upregulation of BAFF gene expression. Finally, neutralization of BAFF by TACI-Ig or depletion of BAFF by small hairpin RNA (shRNA) in BMSCs significantly enhanced lymphoma cell response to chemotherapy and overcame stroma-mediated drug resistance, suggesting that lymphoma cells use BMSC-derived BAFF as a survival factor. These findings support the hypothesis that lymphoma cells interact with BMSCs, resulting in stromal niches with high BAFF concentration, and identify BMSC-derived BAFF as a functional determinant for B lymphoma cell survival in the bone marrow environment.