(1/1794) Arsenic trioxide and melarsoprol induce apoptosis in plasma cell lines and in plasma cells from myeloma patients.
Recent data have renewed the interest for arsenic-containing compounds as anticancer agents. In particular, arsenic trioxide (As2O3) has been demonstrated to be an effective drug in the treatment of acute promyelocytic leukemia by inducing programmed cell death in leukemic cells both in vitro and in vivo. This prompted us to study the in vitro effects of As2O3 and of another arsenical derivative, the organic compound melarsoprol, on human myeloma cells and on the plasma cell differentiation of normal B cells. At pharmacological concentrations (10(-8) to 10(-6) mol/L), As2O3 and melarsoprol caused a dose- and time-dependent inhibition of survival and growth in myeloma cell lines that was, in some, similar to that of acute promyelocytic leukemia cells. Both arsenical compounds induced plasma cell apoptosis, as assessed by 4',6-diamidino-2-phenylindole staining, detection of phosphatidylserine at the cell surface using annexin V, and by the terminal deoxynucleotidyl transferase-mediated nick end labeling assay. As2O3 and melarsoprol also inhibited viability and growth and induced apoptosis in plasma-cell enriched preparations from the bone marrow or blood of myeloma patients. In nonseparated bone marrow samples, both arsenical compounds triggered death in myeloma cells while sparing most myeloid cells, as demonstrated by double staining with annexin V and CD38 or CD15 antibodies. In primary myeloma cells as in cell lines, interleukin 6 did not prevent arsenic-induced cell death or growth inhibition, and no synergistic effect was observed with IFN-alpha. In contrast to As2O3, melarsoprol only slightly reduced the plasma cell differentiation of normal B cells induced by pokeweed mitogen. Both pokeweed mitogen-induced normal plasma cells and malignant plasma cells showed a normal nuclear distribution of PML protein, which was disrupted by As2O3 but not by melarsoprol, suggesting that the two arsenical derivatives acted by different mechanisms. These results point to the use of arsenical derivatives as investigational drugs in the treatment of multiple myeloma. (+info)
(2/1794) Plasma cell development in synovial germinal centers in patients with rheumatoid and reactive arthritis.
Plasma cells are found surrounding the inflammatory infiltrates of macrophages, T, and B cells in the synovial tissue of patients with rheumatoid and reactive arthritis. This characteristic arrangement suggests that in the synovial tissue CD20+ B cells differentiate into plasma cells. To examine clonal relationships, we have used micromanipulation to separately isolate CD20+ B cells and plasma cells from single infiltrates. DNA was extracted, and from both populations the VH/VL gene repertoires was determined. The data show that in the inflamed synovial tissue activated B cells are clonally expanded. During proliferation in the network of follicular dendritic cells, V gene variants are generated by the hypermutation mechanism. Surprisingly, we do not find identical rearrangements between CD20+ B cells and plasma cells. Nevertheless, the finding of clonally related plasma cells within single infiltrates suggests that these cells underwent terminal differentiation in the synovial tissue. These results indicate that B cell differentiation in the synovial tissue is a dynamic process. Whereas CD20+ B cells may turnover rapidly, plasma cells may well be long lived and thus accumulate in the synovial tissue. The analysis of individual B cells recovered from synovial tissue opens a new way to determine the specificity of those cells that take part in the local immune reaction. This will provide new insights into the pathogenesis of chronic inflammatory diseases like rheumatoid or reactive arthritis. (+info)
(3/1794) Human herpesvirus 8 in hematologic diseases.
Human herpesvirus type 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV) is a new member of the g-herpesvirus family. It is an unusual herpesvirus in that it carries a large number of genes that encode oncoproteins or cell signaling proteins. In addition to being the causative agent of both HIV-associated and non-HIV-associated Kaposi's sarcoma this DNA tumor virus has been implicated in the pathogenesis of several diseases. These include multiple myeloma (MM), Waldenstom's macroglobulinemia (WM), multicentric Castleman's disease (MCD), body cavity-based lymphoma (BCBL), and various other conditions such as sarcoidosis and pemphigus. While the causative role of the viral infection is fairly certain in the development of BCBL and multicentric Castleman's disease, HHV-8 may act through a different mechanism to induce plasma cell malignancies. It has been suggested though the finding is still controversial - that infection of bone marrow stromal dendritic cells by HHV-8 might be a key factor in the etiology and pathogenesis of monoclonal gammopathies. The aim of this review is to provide a short introduction into the tumorigenic potential of HHV-8 as well as to detail the available data and possible mechanisms on the involvement of this virus in different hematologic diseases. (+info)
(4/1794) Toward a role of dendritic cells in the germinal center reaction: triggering of B cell proliferation and isotype switching.
We have reported previously that in vitro generated dendritic cells (DC) can directly regulate B cell responses. Recently, germinal center DC (GCDC) were identified within B cell follicles. Due to their particular localization, we have tested in the present study whether GCDC could contribute to key events characteristic of the GC reaction. Our present results demonstrate that 1) ex vivo GCDC induce a dramatic GC B cell expansion upon CD40 and IL-2 activation and drive plasma cell differentiation, 2) this property is shared by GCDC and blood DC, but not by Langerhans cells, 3) IL-12 production by GCDC is critical in GC B cell expansion and differentiation, and 4) importantly, GCDC also induce IL-10-independent isotype switching toward IgG1. These observations support the novel concept that GCDC directly contribute to the germinal center reaction. (+info)
(5/1794) The degrees of plasma cell clonality and marrow infiltration adversely influence the prognosis of AL amyloidosis patients.
BACKGROUND AND OBJECTIVE: Primary amyloidosis is a lethal form of plasma cell (PC) dyscrasia characterized by deposits of monoclonal immunoglobulin light chains that cause organ dysfunction. In contrast to multiple myeloma, the amyloid clone is typically indolent and of small size, and marrow PC clonality is not always apparent. This is generally investigated by analyzing the light chain isotype ratio in bone marrow PC. We investigated whether the degree of PC infiltration (PC%) and clonality (PC isotype ratio) affected survival in 56 consecutive patients with primary amyloidosis. DESIGN AND METHODS: PC% was determined by morphologic examination. Immunofluorescence microscopy was used to determine the PC light chain isotype ratio. Statistical analysis was carried out using Cox regression models. RESULTS: The degrees of PC clonality and infiltration were inversely correlated with survival (PC isotype ratio, p = 0.001; PC%, p = 0.008). The two variables were weakly correlated (p = 0.02; r = 0.3). Bone marrow PC isotype ratio demonstrated a powerful independent prognostic value at multivariate analysis when analyzed together with congestive heart failure (the major known negative prognostic factor) and PC%. k/l ratio cut-off values of 0.2 (l patients, p = 0.022) and 16 (k patients, p = 0.03) discriminated two groups with a similar number of patients and significantly different survivals. INTERPRETATION AND CONCLUSIONS: PC clonality and marrow infiltration are important parameters that influence prognosis, presumably because they reflect the amount of pathogenic light chain synthesis. (+info)
(6/1794) Bone marrow neovascularization, plasma cell angiogenic potential, and matrix metalloproteinase-2 secretion parallel progression of human multiple myeloma.
To assess whether the progression of plasma cell tumors is accompanied by angiogenesis and secretion of matrix-degrading enzymes, bone marrow biopsy specimens from 20 patients with monoclonal gammopathy of undetermined significance (MGUS), 18 patients with nonactive multiple myeloma (MM), and 26 patients with active MM were evaluated for their angiogenic potential and matrix-metalloproteinase (MMP) production. A fivefold increase of the factor VIII+ microvessel area was measured by a planimetric method of point counting in the bone marrow of patients with active MM as compared with nonactive MM and MGUS patients (P <.01). When serum-free conditioned media (CM) of plasma cells isolated from the bone marrow of each patient were tested in vivo for their angiogenic activity in the chick embryo chorioallantoic membrane (CAM) assay, the incidence of angiogenic samples was significantly higher (P <. 01) in the active MM group (76%) compared with nonactive MM (33%) and MGUS (20%) groups. Moreover, a linear correlation (P <.01) was found between the extent of vascularization of the bone marrow of a given patient and the angiogenic activity exerted in the CAM assay by the plasma cells isolated from the same bone marrow. In vitro, a significantly higher fraction of the plasma cell CM samples from the active MM group stimulated human umbilical vein endothelial cell (HUVEC) proliferation (53%, P <.01), migration (42%, P <.05), and/or monocyte chemotaxis (38%, P <.05) when compared with nonactive MM and MGUS groups (ranging between 5% and 15% of the samples). Also, immunoassay of plasma cell extracts showed significantly higher (P <. 01) levels of the angiogenic basic fibroblast growth factor (FGF)-2 in the active MM patients than in nonactive MM and MGUS patients (153 +/- 59, 23 +/- 17, and 31 +/- 18 pg FGF-2/100 micrograms of protein, respectively). Accordingly, neutralizing anti-FGF-2 antibody caused a significant inhibition (ranging from 54% to 68%) of the biological activity exerted on cultured endothelial cells and in the CAM assay by plasma cell CM samples from active MM patients. Finally, in situ hybridization of bone marrow plasma cells and gelatin-zymography of their CM showed that active MM patients express significantly higher (P <.01) levels of MMP-2 mRNA and protein when compared with nonactive MM and MGUS patients, whereas MMP-9 expression was similar in all groups. Taken together, these findings indicate that the progression of plasma cell tumors is accompanied by an increase of bone marrow neovascularization. This is paralleled by an increased angiogenic and invasive potential of bone marrow plasma cells, which is dependent, at least in part, by FGF-2 and MMP-2 production. Induction of angiogenesis and secretion of MMPs by plasma cells in active disease may play a role in their medullary and extramedullary dissemination, raising the hypothesis that angiostatic/anti-MMP agents may be used for therapy of MM. (+info)
(7/1794) Murine plasmacytomas, carrier of the t(12;15) chromosomal translocation, develop from immature/mature B cells not from differentiated plasma cells.
Dysregulation of the c-myc gene by chromosomal translocation in >95% of murine plasmacytomas (MPCs) is an obligatory requirement for the transformation of B lymphocytes into MPCs. However, it is still unknown whether sIg+ B cells or differentiated plasma cells are the legitimate precursor cells from which MPCs develop. To address this question, C.B-17 scid/scid (SCID) mice were reconstituted with splenic surface Ig-positive (sIg+) B lineage cells originating from BALB/cRb6.15 (B/cRb6.15) or human IL-6 transgene-congenic BALB/cRb8.12 mice (B/cRb8.12 IL-6-Tg). Six of 80 SCID mice reconstituted with B/cRb6.15 sIg+ B cells developed MPCs after pristane (2,6,10,14-tetramethylpentadecane) treatment followed by Abelson murine leukemia virus (A-MuLV) infection (incidence 7.5%) and four of 40 after pristane treatment alone (incidence 10%). Similarly, in 20 SCID mice reconstituted with B/cRb8.12 IL-6-Tg splenic sIg+ B cells the MPC incidence was 10%. Karyotype analysis revealed that all the translocations were of typical t(12;15) type and all tumors carried the Rb6.15 or Rb8.12 marker chromosome, indicating their donor cell origin. In contrast, none of the 48 SCID mice reconstituted with plasma cells obtained from the lymph nodes of B/cRb8.12 IL-6-Tg mice developed MPCs when treated either with pristane plus A-MuLV (20 mice) or with pristane alone (28 mice), although the transferred plasma cells were still functional in the recipient SCID mice 6 months after transfer. The findings indicate that the malignant transformation triggered by Ig/myc juxtaposition occurs more in immature (sIgM+) and/or mature (sIgM+/sIgD+, sIgG+ and sIgA+) B cells than in differentiated G0 or cycling plasma cells. We inferred that immature and/or mature B cells and not differentiated plasma cells are most likely the principal source of precursor cells from which the typical t(12;15) MPCs develop. (+info)
(8/1794) In vitro induction of the expression of multiple IgA isotype genes in rabbit B cells by TGF-beta and IL-2.
The rabbit genome has 13 different Calpha genes that are expressed at different levels in mucosal tissues. To analyze the factors involved in the differential expression of these Calpha genes, we cloned and sequenced the promoters of the Ialpha regions that control the expression of sterile mRNA. We found that all Calpha genes, including Calpha3 and Calpha8, which are not expressed, and Calpha4, which is expressed at high levels, have similar nucleotide sequences in the Ialpha region, and all contain the recognition elements for TGF-beta in the promoter. B lymphocytes from popliteal lymph nodes or Peyer's patch activated in vitro could be induced by TGF-beta to express sterile IgA transcripts of all IgA isotypes, except Calpha2, Calpha3, and Calpha8. Many single B lymphocytes transcribed sterile mRNA of more than one IgA isotype, which demonstrates that transcription of sterile mRNA alone does not regulate the IgA isotype switch. The addition of IL-2 led to the expression of transcripts of mature IgA of all isotypes, except Calpha2, Calpha3, and Calpha8. The predominantly expressed isotype in these experiments was Calpha4. With the use of an IgA4-specific mAb we found that IgA4+ plasma cells are unevenly distributed throughout the small intestine such that many of the IgA+ plasma cells in the duodenum-jejunum produced IgA4, whereas in the lower part of the ileum IgA4-producing cells were almost absent. Because the microbial flora varies throughout the intestine, we suggest that the microbial flora creates different local environments and thus affects either isotype switching or homing of IgA-expressing cells. (+info)