Surface antigen expression of human neoplastic plasma cells includes molecules associated with lymphocyte recirculation and adhesion

Lymphocyte Subsets and Inflammatory Cytokines of Monoclonal Gammopathy of Undetermined Significance and Multiple Myeloma

Almost all multiple myeloma (MM) cases have been demonstrated to be linked to earlier monoclonal gammopathy of undetermined significance (MGUS). Nevertheless, there are no identified characteristics in the diagnosis of MGUS that have been helpful in differentiating subjects whose cancer may progress to a malignant situation. Regarding malignancy, the role of lymphocyte subsets and cytokines at the beginning of neoplastic diseases is now incontestable. In this review, we have concentrated our attention on the equilibrium between the diverse lymphocyte subsets and the cytokine system and summarized the current state of knowledge, providing an overview of the condition of the entire system in MGUS and MM. In an age where the therapy of neoplastic monoclonal gammopathies largely relies on drugs capable of acting on the immune system (immunomodulants, immunological checkpoint inhibitors, CAR-T), detailed knowledge of the the differences existing in benign and neoplastic forms of gammopathy is the main foundation for the adequate and optimal use of new drugs.

Nodular Lesions of the Liver in Multiple Myeloma: A Role for Cytoadhesion Molecules?

Two patients with multiple myeloma and in vivo macroscopic nodular lesions of the liver are presented. The clinical aspects of this very unusual condition are briefly reviewed. In particular, the expression on neoplastic plasma cells of the cytoadhesion molecules CD56 and CD11a, which are involved in the cellular process of recirculation and homing, suggests a possible role for such markers in this atypical localization of the disease.

Cell-surface serglycin promotes adhesion of myeloma cells to collagen type I and affects the expression of matrix metalloproteinases

Serglycin (SG) is mainly expressed by hematopoetic cells as an intracellular proteoglycan. Multiple myeloma cells constitutively secrete SG, which is also localized on the cell surface in some cell lines. In this study, SG isolated from myeloma cells was found to interact with collagen type I (Col I), which is a major bone matrix component. Notably, myeloma cells positive for cell-surface SG (csSG) adhered significantly to Col I, compared to cells lacking csSG. Removal of csSG by treatment of the cells with chondroitinase ABC or blocking of csSG by an SG-specific polyclonal antibody significantly reduced the adhesion of myeloma cells to Col I. Significant up-regulation of expression of the matrix metalloproteinases MMP-2 and MMP-9 at both the mRNA and protein levels was observed when culturing csSG-positive myeloma cells on Col I-coated dishes or in the presence of soluble Col I. MMP-9 and MMP-2 were also expressed in increased amounts by myeloma cells in the bone marrow of patients with multiple myeloma. Our data indicate that csSG of myeloma cells affects key functional properties, such as adhesion to Col I and the expression of MMPs, and imply that csSG may serve as a potential prognostic factor and/or target for pharmacological interventions in multiple myeloma.

Expression and Functional Role of CD54/Intercellular Adhesion Molecule-1 (ICAM-1) on Human Blood Cells

CD54/Intercellular Adhesion Molecule-1 (ICAM-1) is a cell adhesion molecule largely distributed among normal and neoplastic tissues. Through the binding to its ligand(s) CD54 plays a key role in cell to cell interactions leading to the immune response. Recently, CD54 expression has been investigated on hematopoietic cells: the antigen is predominantly expressed in the early stages of normal hematopoiesis and during the activation of blood cells. As regards to hematological malignancies, CD54 is strongly expressed on neoplastic cells from "stem cell derived" neoplasms. In AML, CD54 expression is related with other differentiation-linked molecules such as CD34 and HLA-DR and is significantly correlated with FAB morphological classification. In lymphoproliferative disorders, a high CD54 expression is associated with germinal centre lymphomas. This review summarizes our current understanding of CD54 with emphasis on recent advances and reference to unresolved issues such as its prognostic role in the clinical outcome of oncohematological diseases.

FcγRIIb controls bone marrow plasma cell persistence and apoptosis

The survival of long-lived plasma cells, which produce most serum immunoglobulin, is central to humoral immunity. We found here that the inhibitory Fc receptor FcgammaRIIb was expressed on plasma cells and controlled their persistence in the bone marrow. Crosslinking FcgammaRIIb induced apoptosis of plasma cells, which we propose contributes to the control of their homeostasis and suggests a method for therapeutic deletion. Plasma cells from mice prone to systemic lupus erythematosus did not express FcgammaRIIb and were protected from apoptosis. Human plasmablasts expressed FcgammaRIIb and were killed by crosslinking, as were FcgammaRIIb-expressing myeloma cells. Our results suggest that FcgammaRIIb controls bone marrow plasma cell persistence and that defects in it may contribute to autoantibody production.

A negative-selection strategy for depleting myeloma cells from patients' BM and/or leukapheresis blood

BACKGROUND

Autologous transplantation improves survival in multiple myeloma patients, however, most eventually relapse. As an attempt towards improving relapse-free survival, we designed a negative-selection purging strategy, to remove myeloma cells from leukapheresis harvests using MAbs specific for Ags on myeloma cells.

METHODS

CD38 is highly expressed on myeloma plasma cells, but expressed at lower levels on normal progenitors and absent on in vivo repopulating cells. We evaluated depletion of CD38-expressing cells, with or without depletion of B-cell Ag-expressing cells. Using myeloma BM or blood cells diluted into allogeneic G-CSF primed leukapheresis cells, bispecific tetrameric Ab complexes that bind dextran iron particles were used to label and retain cells in a magnetic column, StemSep. Depletion efficacy was measured by semi-quantitative allele-specific oligonucleotide (ASO)-PCR amplification of patients' clonotypic IgH gene.

RESULTS

Low (0.2 microg/mL) concentrations of anti-CD38 with CD19 and CD20 complexes depleted approximately 3-5 logs of clonotypic cells, with recovery of approximately 19% of colony-forming cells, approximately 50% primitive progenitors measured by LTCIC and retention of non-obese diabetic /SCID engrafting ability. Scale-up experiments using leukapheresis harvests and 0.5-1 x 10(10) cell capacity columns demonstrated no loss of log depletion of highly positive cells, or recovery of unlabelled cells.

DISCUSSION

These results compare favorably with other purging techniques and allow the retention of most normal BM cells, including T cells, which may be important for immunity. These results support the development of a clinical trial using this strategy for purging myeloma cells.

Circulating immunoglobulin A- and immunoglobulin G-secreting hybridoma cells in peripheral blood preferably migrate to female genital tracts. The role of sex hormones

Antigen-specific circulating immunoglobulin-secreting cells (ISC) migrate to various secondary and tertiary lymphoid tissues. To understand the migration of the cells into the genital tract and its regulation by sex hormones, spleen-derived SG2 hybridoma cells secreting immunoglobulin G2b (IgG2b) and Peyer's patch-derived PA4 hybridoma cells secreting polymer IgA were labelled with 3H-TdR, and intravenously injected into syngeneic mice of both sexes. Using flow cytometry, surface molecular markers of plasma cells, CD38 and CD138, and adhesion molecules, CD49d, CD162, and CD11a were found to be positive in SG2 and PA4 cells, but CD62L, alpha4beta7 and CD44 were not expressed on these cells. The relative distribution indexes (RDIs) of the cells in genital tract and other tissues were measured. The means of RDIs of SG2 and PA4 cells in female genital tissues were 6.5 and 4.5 times as many as the means in male genital tissues, respectively. The treatment of ovariectomized mice with beta-oestradiol significantly increased the RDIs of PA4 cells in cervix and vagina, but decreased the RDIs of SG2 cells in vagina, horn of uterus, uterus and rectum (P<0.05). Progesterone treatment increased the RDIs of PA4 cells in vagina and rectum (P<0.05). The treatment with testosterone significantly increased the RDIs of SG2 and PA4 cells in epididymis and accessory sex glands (P<0.05). These results demonstrate that the female genital tract is the preferable site for the migration of circulating hybridoma cells to the male genital tract, and sex hormones play an important role in regulation of the migration of circulating ISC to genital tracts.

Immunophenotypic Aberrations, DNA Content, and Cell Cycle Analysis of Plasma Cells in Patients with Myeloma and Monoclonal Gammopathies

We describe the immunophenotypic and gross DNA defects in 55 patients with myeloma and 50 patients with monoclonal gammopathy and review the literature on this subject (MedLine, 1994-2000). Our data confirmed previous reports indicating that in myeloma nearly all marrow plasma cells are abnormal (98.7 +/- 8.1%). In monoclonal gammopathy the fraction of abnormal plasma cells was 35.0 +/- 32.8%. In both myeloma and monoclonal gammopathy, the most frequent aberrant phenotypic features consisted of absence of expression of CD19, strong expression of CD56, and decreased intensity of expression of CD38; aberrant expression of CD10, CD20, CD22, or CD28 was observed in less than one-third of myeloma cases. The vast majority of cases had two or more phenotypic aberrations. In the DNA studies, 7% of myeloma cases were biclonal and 93% of cases were monoclonal. In those studies with only one plasma cell mitotic cycle, 37% had normal DNA content and 63% were aneuploid (hyperploid, 61%; hypoploid, 2%). The mean percentages of plasma cells in S- and G2M phases were 4.9 +/- 8.5 and 4.4 +/- 6.9%, respectively. Thirty-eight percent of cases had more than 3% of plasma cells in S phase. In monoclonal gammopathy, the DNA index of abnormal plasma cells ranged from 0.89 to 1.30 and the percentage of diploid (31%) and aneuploid (69%) cases was not different from the results found in myeloma. The differences in percentage of abnormal plasma cells in S- (7.4 +/- 8.6%) and G2M-phases (2.4 +/- 1.7%) in patients with monoclonal gammopathy were not statistically significant.

Prognostic factors in multiple myeloma

There is significant variation in the survival of patients with myeloma. This article reviews the major prognostic factors in myeloma and the evidence supporting their usefulness in clinical practice and research. The factors reviewed include serum beta 2-microglobulin, bone marrow plasma cell labeling index, cytogenetics, plasmablastic morphology, and other standard clinical laboratory variables. Novel factors such as bone marrow angiogenesis are also discussed. A combination of independent factors provides greater prognostic information than any one factor alone, and survival data using various combinations of prognostic factors are presented.

The role of adhesion receptors in the pathogenesis of multiple myeloma

There is now an improved understanding of the types of adhesion receptors present on normal and malignant plasma cells. This knowledge has been helpful in identifying plasma cells and in beginning to understand the pathogenesis of myeloma. Future research is needed to delineate the signaling pathways used by the plasma cell after the adhesion receptor binds to its ligands. This information should help in designing more effective therapy for this fatal disease.

Monoclonal gammopathies and associated skin disorders

The monoclonal gammopathies are characterized by clonal proliferation of plasma cells and other clonally related cells in the B-cell lineage. These disorders include monoclonal gammopathy of undetermined significance, multiple myeloma, Waldenström macroglobulinemia, heavy chain diseases, plasmacytoma, and primary amyloidosis. Many skin disorders have been described in association with monoclonal gammopathies. This article provides an introduction to the definition, detection, natural course, and spectrum of monoclonal gammopathies and a brief discussion of pathogenesis. The article also reviews the skin disorders associated with monoclonal gammopathies, categorizes the association, and evaluates the strength of the association.

Comparison of Interleukin-1β Expression by In Situ Hybridization in Monoclonal Gammopathy of Undetermined Significance and Multiple Myeloma

We investigated whether interleukin-1β (IL-1β) is differentially expressed in plasma cells from monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM) patients because IL-1β appears to play a major role in the development of lytic bone lesions, the major clinical feature distinguishing MGUS from myeloma. In situ hybridization (ISH) for IL-1β was performed using bone marrow aspirates from 51 MM, 7 smoldering MM, 21 MGUS, and 5 normal control samples. Using the ISH technique IL-1β mRNA was detectable in the plasma cells from 49 of 51 patients with active myeloma and 7 of 7 patients with smoldering myeloma. In contrast, 5 of 21 patients with MGUS and 0 of 5 normal controls had detectable IL-1β message. Bone lesions were present in 40 of the 51 MM patients analyzed, and all 40 patients had IL-1β mRNA by ISH. These results show that greater than 95% of MM patients but less than 25% of MGUS patients are positive for IL-1β production. In the future, continued follow-up of IL-1β positive and negative MGUS patients should determine whether aberrant expression of plasma cell IL-1β is predictive of those MGUS patients that will eventually progress to active myeloma.

Comparison of Interleukin-1β Expression by In Situ Hybridization in Monoclonal Gammopathy of Undetermined Significance and Multiple Myeloma

We investigated whether interleukin-1β (IL-1β) is differentially expressed in plasma cells from monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM) patients because IL-1β appears to play a major role in the development of lytic bone lesions, the major clinical feature distinguishing MGUS from myeloma. In situ hybridization (ISH) for IL-1β was performed using bone marrow aspirates from 51 MM, 7 smoldering MM, 21 MGUS, and 5 normal control samples. Using the ISH technique IL-1β mRNA was detectable in the plasma cells from 49 of 51 patients with active myeloma and 7 of 7 patients with smoldering myeloma. In contrast, 5 of 21 patients with MGUS and 0 of 5 normal controls had detectable IL-1β message. Bone lesions were present in 40 of the 51 MM patients analyzed, and all 40 patients had IL-1β mRNA by ISH. These results show that greater than 95% of MM patients but less than 25% of MGUS patients are positive for IL-1β production. In the future, continued follow-up of IL-1β positive and negative MGUS patients should determine whether aberrant expression of plasma cell IL-1β is predictive of those MGUS patients that will eventually progress to active myeloma.

Interdependence between cytokines and cell adhesion molecules to induce interleukin-6 production by stromal cells in myeloma

Bone marrow (BM) environment is thought to support the growth of myeloma cells and thus to play an important role in the pathogenesis of multiple myeloma (MM). Because interleukin-6 (IL-6) is an essential growth factor in MM, we have examined the effects of two myeloma cell lines (U266 and ARH-77) on the IL-6 production by BM stromal cells in a co-culture system. These cell lines strongly stimulate the IL-6 production and IL-6 triggering was partially dependent on physical contact between lines and stroma. The percentages of cell adhesion to stromal layers were 39% and 25% respectively for ARH77 and U266 cell lines. Inhibition studies with blocking monoclonal antibodies showed the importance of CD49d/CD106 and CD11a/CD54 interactions in the stimulation of IL-6 production by stromal cells. However, cell-to-cell contact was not an absolute requirement for IL-6 production. Cytokines, of which TNF-alpha and IL-1beta produced by MM or accessory cells, were also able to stimulate IL-6 production by fibroblasts and show additive effects. In adhesion assays, TNF-alpha and IL-1beta were able to increase the adhesion of MM cells to stromal cells. CD54 was upregulated by IL-1beta, TNF-alpha or a contact with MM cells while CD106 expression was not, suggesting only a functional change of this molecule. However, the role of monoclonal antibodies, directed against these factors, confirmed the role of TNF-alpha in the IL-6 production by stromal cells, while any IL-1beta intervention was not shown in our co-culture system. IL-6 favoured and maintained adhesion of MM cells to stromal cells spontaneously since its reintroduction in the favoured co-culture system restored their decreased adhesion observed on a glutaraldehyde fixed stromal layer. Overall our data suggest a functional overlap between cytokines and adhesion molecules for the paracrine IL-6 production.

Biology of the Transition of Monoclonal Gammopathy of Undetermined Significance (MGUS) to Multiple Myeloma

BACKGROUND: Approximately 25% of patients with monoclonal gammopathy of undetermined significance (MGUS) eventually develop multiple myeloma (MM) or a related plasma cell disorder that is universally fatal. In this report, we examine the changes that occur in the clonal plasma cell that are likely to be important in the progression of MGUS to active myeloma. METHODS: Studies that investigate the mechanisms involved in the multistep pathogenesis of monoclonal gammopathies are reviewed. Cytokines such as IL-6 and IL-1-beta, adhesion molecules, viruses, and oncogenes including ras, bcl-2, Rb, and p53 are discussed. RESULTS: IL-1-beta is produced by plasma cells from virtually all MM patients but is undetectable in most MGUS patients. IL-1-beta has potent osteoclast activating factor activity, can increase the expression of adhesion molecules, and can induce paracrine IL-6 production. The increased production of adhesion molecules could explain why myeloma cells are found predominantly in the bone marrow. Subsequently, these "fixed" monoclonal plasma cells could now stimulate osteoclasts through the production of IL-1-beta and paracrine generation of IL-6 resulting in osteolytic disease. With continued progression of the myeloma, the monoclonal plasma cells may later acquire the ability to produce IL-6 in an autocrine fashion that will be manifested clinically by an elevated labeling index. CONCLUSIONS: A better understanding of the progression of MGUS to myeloma may lead to novel therapeutic strategies to prevent the development of MM.

Expression of beta 1 integrins (very late antigens-4 and -5) on myeloma cells and clinical correlates in patients with multiple myeloma

beta 1 Integrins are considered to be essential for the differentiation of bone-marrow B cells through an interaction with fibronectin-expressed bone-marrow stromal cells. The expression of very late antigens-4 (VLA-4) and -5 (VLA-5) by CD38bright bone-marrow cells in patients with multiple myeloma was measured by flow cytometry using specific monoclonal antibodies. The percentage of CD38bright bone-marrow cells appeared to correlated with that of bone-marrow plasma cells as judged by examination of bone-marrow smears (r = 0.911, P < 0.0001). Expression of VLA-4 and VLA-5 by CD38bright cells varied between patients, but the expression of VLA-4 was always equal to or greater than that of VLA-5. The ratio of VLA-4 to VLA-5 expression (VLA-4:VLA-5 ratio) was calculated and compared with the clinical features of the myeloma patients. A high VLA-4:VLA-5 ratio (> 2.0) was associated with the presence of plasmacytomas and urinary Bence-Jones protein was more common in this group. No other correlations between the clinical features of the disease and the expression of beta 1 integrins were found.

The Development of a Model for the Homing of Multiple Myeloma Cells to Human Bone Marrow

Prior in vitro studies have suggested a role of adhesion molecules, bone marrow stromal cells (BMSCs), and cytokines in the regulation of human multiple myeloma (MM) cell growth and survival. Although in vivo models have been developed in severe combined immunodeficient (SCID) mice that support the growth of human MM within the murine BM microenvironment, these xenograft models do not permit a study of the role of adhesion proteins in human MM cell-human BMSC interactions. We therefore established an in vivo model of human MM using SCID mice implanted with bilateral human fetal bone grafts (SCID-hu mice). For the initial tumor innoculum, human MM derived cell lines (1 × 104 or 5 × 104 ARH-77, OCI-My5, U-266, or RPMI-8226 cells) were injected directly into the BM cavity of the left bone implants in irradiated SCID-hu mice. MM cells engrafted and proliferated in the left human fetal bone implants within SCID-hu mice as early as 4 weeks after injection of as few as 1 × 104 MM cells. To determine whether homing of tumor cells occurred, animals were observed for up to 12 weeks after injection and killed to examine for tumor in the right bone implants. Of great interest, metastases to the right bone implants were observed at 12 weeks after the injection of 5 × 104 MM cells, without spread of human MM cells to murine BM. Human MM cells were identified on the basis of characteristic histology and monoclonal human Ig. Importantly, monoclonal human Ig and human interleukin-6 (IL-6), but not human IL-1β or tumor necrosis factor-α, were detectable in sera of SCID-hu mice injected with MM cells. In addition, specific monoclonal Ig light chain deposition was evident within renal tubules. This in vivo model of human MM provides for the first time a means for identifying adhesion molecules that are responsible for specific homing of human MM cells to the human, as opposed to murine, BM microenvironment. Moreover, induction of human IL-6 suggests the possibility that regulation of MM cell growth by this cytokine might also be investigated using this in vivo model.

The Development of a Model for the Homing of Multiple Myeloma Cells to Human Bone Marrow

Prior in vitro studies have suggested a role of adhesion molecules, bone marrow stromal cells (BMSCs), and cytokines in the regulation of human multiple myeloma (MM) cell growth and survival. Although in vivo models have been developed in severe combined immunodeficient (SCID) mice that support the growth of human MM within the murine BM microenvironment, these xenograft models do not permit a study of the role of adhesion proteins in human MM cell-human BMSC interactions. We therefore established an in vivo model of human MM using SCID mice implanted with bilateral human fetal bone grafts (SCID-hu mice). For the initial tumor innoculum, human MM derived cell lines (1 × 104 or 5 × 104 ARH-77, OCI-My5, U-266, or RPMI-8226 cells) were injected directly into the BM cavity of the left bone implants in irradiated SCID-hu mice. MM cells engrafted and proliferated in the left human fetal bone implants within SCID-hu mice as early as 4 weeks after injection of as few as 1 × 104 MM cells. To determine whether homing of tumor cells occurred, animals were observed for up to 12 weeks after injection and killed to examine for tumor in the right bone implants. Of great interest, metastases to the right bone implants were observed at 12 weeks after the injection of 5 × 104 MM cells, without spread of human MM cells to murine BM. Human MM cells were identified on the basis of characteristic histology and monoclonal human Ig. Importantly, monoclonal human Ig and human interleukin-6 (IL-6), but not human IL-1β or tumor necrosis factor-α, were detectable in sera of SCID-hu mice injected with MM cells. In addition, specific monoclonal Ig light chain deposition was evident within renal tubules. This in vivo model of human MM provides for the first time a means for identifying adhesion molecules that are responsible for specific homing of human MM cells to the human, as opposed to murine, BM microenvironment. Moreover, induction of human IL-6 suggests the possibility that regulation of MM cell growth by this cytokine might also be investigated using this in vivo model.

Expression of adhesion molecules in malignant plasma cells in multiple myeloma: comparison with normal plasma cells and functional significance

Malignant plasma cells in multiple myeloma are predominantly confined to the bone marrow, where they stimulate cytokine production by stromal cells and bone cells leading to osteoclast activation and formation of the characteristic lytic lesions in the skeleton. Adhesion molecules are critically involved in the cellular interactions between myeloma cells and stromal elements and may represent novel therapeutic targets to reduce osteolytic bone disease in multiple myeloma. Here, we review the literature on the adhesion molecule repertoire expressed by malignant plasma cells and discuss the evidence that adhesive interactions between myeloma cells and stromal cells stimulate production of bone-resorbing cytokines.

CD40/CD40 ligand interactions in normal, reactive and malignant lympho-hematopoietic tissues

CD40 is a 48 Kd integral membrane protein expressed by cells of B cells, origin, dentritic cells, monocytes, epithelial cells, endothelial cells and tumor cells including carcinomas, B cell lymphomas/leukemias and Hodgkin and Reed-Sternberg (HRS) cells of Hodgkin's disease (HD). CD40 has been clustered as a member of the nerve growth factor (NGF)/tumor necrosis factor (TNF) receptor superfamily with the corresponding counterstructure, the CD40 ligand (L) being mainly expressed by activated CD4+ T cells, but also some activated CD8+ T cells, basophils, eosinophils, mast cells and stromal cells. CD40L shares significant amino acid homology with TNF particularly in its extracellular domain ("TNF homology region") and is therefore viewed as a member of the TNF ligand superfamily. Binding of CD40L+ T cells to CD40+ B cells is thought to play a major role in T cell-dependent B cell activation, B cell proliferation, Ig isotype switching, memory B cell formation and rescue of B cells from apoptotic death in germinal centers. Mutations of the CD40L gene have been associated with the X-linked hyper-IgM immunodeficiency syndrome, pointing to the critical role of the CD40/CD40L interaction in the T cell-B cell interplay. Accordingly, expression of CD40 by human lympho-hematopoietic tumors has been shown in most of the B cell neoplasias, H-RS cells and HD and some carcinomas. In contrast, CD40L+ tumor cells are almost invariably restricted to CD4+/CD8- T cell lymphomas. Overall, functional CD40/CD40L interactions appear to be critical for cellular activation signals during immune responses and neoplastic tumor cell growth. The understanding of the biology of CD40L has improved our diagnostic and therapeutic repertoire in the management of several human diseases, including CD40+ tumors.

Identification of a novel dendritic cell surface antigen defined by carbohydrate specific CD24 antibody cross-reactivity

Dendritic cells (DC) are characterized as leucocytes that lack mature lineage specific markers and stimulate naive T-lymphocyte proliferation in vitro and in vivo. The mouse heat stable antigen (HSA) participates in T lymphocyte co-stimulation and is expressed by DC isolated from thymus, skin and spleen. The human HSA homologue, CD24, is predominantly expressed by B lymphocytes and granulocytes, but its expression on DC has not been studied in detail. CD24 clearly participates in B-lymphocyte signalling but co-stimulatory activity for T lymphocytes has not yet been described. We have examined the expression of CD24 on human peripheral blood DC populations isolated directly or following in vitro culture. The CD24 antigen was absent from blood DC however, cross-reactive sialylated carbohydrate epitopes were detected on DC with some CD24 monoclonal antibodies (mAb). These CD24 mAb define a protein surface antigen, which is expressed by an immature or resting subpopulation of peripheral blood DC and is down-regulated following activation differentiation in vitro.

Very late antigen (VLA) expression by normal and neoplastic human plasma cells; including an assessment of antibodies submitted to the Vth International Workshop on Leucocyte Differentiation Antigens using human myeloma cell lines

The biology of normal plasma cells and the pathophysiology of human multiple myeloma remain poorly understood. Functional assays are scarce and at present cell phenotyping is providing the most information about how human plasma cells may behave. Three different types of human plasma cells: normal, fresh neoplastic myeloma cells and plasma cell lines, have been studied for their reactivity with antibodies to the beta-1 integrins (Very Late Antigens; VLAs), including a panel obtained from the Vth International Workshop on Leucocyte Differentiation Antigens. Most plasma cell targets express VLA-4 (CD49d positive) and the common beta chain recognized by CD29. CD49e (VLA-5) was occasionally positive. Other VLAs were not usually expressed. These data suggest the wide use by plasma cells of VLA-4, possibly as a ligand with fibronectin and high endothelial venules (HEV). Of other adhesion structures expressed by plasma cells, only CD44 is seen as frequently, and this is also a HEV ligand.

CD40 and the effect of anti-CD40-binding on human multiple myeloma clonogenicity

CD40 is a 48 kDa glycosylated phospoprotein that is a member of the tumor necrosis factor receptor (TNF-R) superfamily. CD40 was originally identified in B lymphocytes, and is found on monocytes, dendritic cells, some carcinoma cell lines, and the thymic epithelium. CD40 is expressed on normal pre-B through mature B stages of differentiation. For normal B cells, the cross-linking of CD40 induces cell cycle progression, long-term proliferation in vitro, IgE secretion, increased adhesion molecule (LFA-1) expression, and low level IL-6 secretion. The natural ligand of CD40 (CD40L, gp39, or T-BAM, for T-B cell activating molecule) was recently identified as an inducible molecule expressed transitionally on activated T cells. Although originally believed to be absent in normal and malignant plasma cells, CD40 has been demonstrated on the majority of myeloma cell lines and myeloma cells from plasma cell dyscrasia (PCD) patient specimens tested. CD40 activation modulated myeloma cell proliferation and clonogenicity in vitro, suggesting that the CD40 pathway is active in myeloma cell growth. For the IL-6 dependent cell line ANBL-6, CD40 activation was associated with autocrine IL-6 production. However, the IL-6 pathway does not appear to play a predominant role in CD40 activation of non-IL-6-dependent MM cell lines and patient primary bone marrow cultures. The possible pathophysiologic role of the CD40 receptor in human multiple myeloma is discussed.

High proportions of VLA-5- immature myeloma cells correlated well with poor response to treatment in multiple myeloma

Using two-colour phenotypic analysis with anti-CD38 antibody, human myeloma cells can be classified into VLA-5- immature and VLA-5+ mature cells. We examined the relationship between variations of these subpopulations and clinical responses during treatment in multiple myeloma (MM). 39 patients with MM were treated with combined chemotherapy. First estimation of clinical responses after induction therapy showed that early clinical responses were correlated with the percentage of immature myeloma cells present after induction therapy (P < 0.01), not at diagnosis. After three courses of cyclic maintenance therapy, immature myeloma cells significantly decreased in proportion along with a decrease in total myeloma cells in maintained or more responsive cases (P < 0.01). On the other hand, immature myeloma cells were still found in high proportions in nonresponsive cases with no change (NC) or minor response (MR) (P < 0.01). Furthermore, in relapsing cases from partial response (PR) or progressive disease (PD) from nonresponsive cases, immature myeloma cells increased markedly. Therefore these results show that high proportions of VLA-5- immature myeloma cells remaining after induction therapy and during maintenance therapy correlate well with a declining clinical course of MM during maintenance therapy.

Bone marrow of patients with active multiple myeloma: angiogenesis and plasma cell adhesion molecules LFA-1, VLA-4, LAM-1, and CD44

Bone marrow plasma cells and stromal cells in multiple myeloma (MM) have been shown to be capable of releasing cytokines with angiogenic properties. Plasma cells can also express adhesion molecules controlling their adhesive interactions with endothelial cells. In the present study, we have evaluated by immunohistochemistry the extent of angiogenesis in the bone marrow of: a) 51 patients with active and non-active MM; b) 25 patients with monoclonal gammopathy of undetermined significance (MGUS). Plasma cells were investigated by flow cytometry for the expression of the adhesion molecules LFA-1, VLA-4, LAM-1, and CD44. The results showed that, while angiogenesis was very low or absent in patients with MGUS and non-active MM, it increased markedly in those with active MM. The highest detectability of plasma cell adhesion molecules, except LAM-1, was also found in these patients. The functional significance of these findings is unknown. Their consistent occurrence in the bone marrow of active myeloma patients, however, strongly suggests that more frequent adhesive interactions between plasma cells and their microvasculature underlie tumor dissemination.

Mobilization of peripheral blood stem cells with chemotherapy and cytokines in multiple myeloma

In an attempt to offset the impaired hematopoietic progenitors' mobilization and collection which are frequently encountered in multiple myeloma (MM), we have started a pilot study to evaluate the ability of a combination of high-dose melphalan (HDM) and sequential s.c. administration of recombinant human interleukin 3 (rhIL-3) and rh-granulocyte colony-stimulating factor (G-CSF) to mobilize blood cells (BC) in MM patients. Two different schedules for administration were successively tested. Schedule A consisted of IL-3 (5 micrograms/kg/d) from day 7 to day 11 after HDM followed by G-CSF (5 micrograms/kg/d) from day 12 to day 20. Under schedule B, HDM was followed by IL-3 alone at the same dosage from day 1 to day 3, IL-3 and G-CSF (idem) from day 4 to day 7 and G-CSF alone from day 8 until completion of apheresis. Two patients (one previously untreated, one having received prior chemotherapy for one year) underwent schedule A; three patients (one previously untreated, two pretreated) underwent schedule B. The post-HDM aplasia was not shortened in schedule A patients in comparison to what we usually observed following HDM alone (25 days) correlated with a very moderate two- to three-fold CD34+ cell increase. Only one patient was further transplanted with apheresis products: the post-transplant granulocyte recovery was slower than usual (16 days versus 12 days) while platelet count never recovered over 20 x 10(9)/l. In contrast, the post-HDM aplasia was significantly shortened in two of the schedule B patients (3 to 10 days) and was followed by a 25- to 165-fold increase in CD34+ cells.(ABSTRACT TRUNCATED AT 250 WORDS)

The clonogenic precursor cell in multiple myeloma

Multiple myeloma is characterized by the monoclonal expansion of plasma cells in the bone marrow. Although the predominant cell type is the plasma cell, the initial oncogenic transformation is considered to take place in a more immature B cell. There is still much controversy about this precursor cell type. Phenotypic analysis of bone marrow and peripheral blood revealed that in multiple myeloma a great diversity exists in the phenotype of the cells considered to be involved. Because of the lack of a myeloma specific genetic lesion it is very difficult to trace back the cell in which the transforming event, leading to multiple myeloma, took place. The only real clonal marker is the idiotype of the immunoglobulin molecule expressed by the myeloma cells. With recombinant DNA technology it is now possible to produce clonal markers for each individual myeloma patient which recognize only the immunoglobulin genes expressed by the myeloma cell and its precursors. The sequences of these myeloma immunoglobulin genes do reveal a lot of information about the stage in the B-cell differentiation pathway in which the oncogenic event might have taken place. The presence of somatic mutations in a non-random fashion without intraclonal variation leads to the conclusion that the precursor myeloma cell could not possibly be a pre-B cell or stem cell but has to be a mature B cell that has been in contact with antigen and has past through the phase of somatic mutation, like a memory B cell or plasmablast.(ABSTRACT TRUNCATED AT 250 WORDS)

CD19 and immunophenotype of bone marrow plasma cells in monoclonal gammopathy of undetermined significance

AIMS

To determine whether a particular phenotype or antigen is preferentially related to monoclonal gammopathies of undetermined significance (MGUS).

METHODS

Bone marrow specimens from 56 patients with MGUS were stained immunocytochemically (ABC peroxidase) for CD38, CD56, CD9, CD10, CD19, CD20, CD22, and MB2. Specimens from patients recently diagnosed with multiple myeloma and reactive bone marrow samples were studied in parallel.

RESULTS

CD38 was expressed on all plasma cells from all MGUS samples tested, while 36% were positive for CD56, CD9 and MB2 were both expressed strongly; CD20 was moderately expressed, and staining for CD10 and CD22 was uncommon. For these five B cell antigens there was no clear difference between their expression in MGUS and in multiple myeloma. A great difference was found for CD19: in MGUS this antigen was expressed on 2-91% of plasma cells (mean 35%) and 77% patients had > 10% positive plasma cells; in multiple myeloma its expression was low and only 12% patients had > 10% positive plasma cells. When these results were converted to numbers of CD19 positive plasma cells per 100 nucleated bone marrow cells, reactive bone marrow and MGUS specimens had a similar number of positive plasma cells. There was no correlation between expression of any of the antigens tested.

CONCLUSIONS

Many of the so-called pre-B, B or activation antigens are present on plasma cells from MGUS specimens, and expression of CD9, CD10, CD20, CD22, MB2, and CD38 in MGUS was very similar to that in multiple myeloma. CD56 was frequently expressed in MGUS. In this series CD19 was highly expressed in MGUS but not in multiple myeloma. Plasma cells bearing this antigen could represent the non-neoplastic process and determination of its expression could be useful for the diagnosis of MGUS.

Cell surface expression and functional significance of adhesion molecules on human myeloma-derived cell lines

Multiple myeloma is characterized by the presence of malignant plasma cells predominantly localized in bone marrow. Our prior studies have suggested that human myeloma derived-cell lines adhere specifically to fibronectin and to bone marrow stromal cells (BMSCs) via beta 1 and beta 2 integrins as well as RGD peptide, and that tumour cell to BMSC contact triggers interleukin-6 (IL-6) secretion from BMSCs. Since IL-6 is a growth factor for myeloma, adhesion may be important in paracrine IL-6 mediated tumour cell growth. We therefore examined phenotypic expression of adhesion molecules on the U266 and IM-9 human myeloma-derived cell lines using the panel of monoclonal antibodies (MoAbs) directed at adhesion molecules submitted to the Vth International Conference on Human Leukocyte Differentiation Antigens. U266 and IM-9 myeloma cell lines express mainly CD29, CD49d, VLA-1, CD18, CD54, ICAM-2 and ICAM-3. In contrast, CD49b, VLA-3, CD49f, CD11b, VCAM-1, selectins and selectin-ligands were not expressed on these cell lines. Specific adherence of IM-9 cells to BMSC line LP101 was demonstrated which could be partially blocked by pre-incubation and culture of tumour cells with anti-beta 1 integrin, anti-beta 2 integrin, anti-CD49d, anti-VLA-5, anti-CD11a, anti-CD44 and anti-CD54 MoAbs. The combination of these MoAbs (anti-CD29, CD18, CD11a, CD49d, VLA-5, CD44, CD54, ICAM-2, ICAM-3 MoAbs) decreased but did not completely abrogate binding of IM-9 to BMSCs. Moreover, increases in IL-6 secretion from BMSCs after adherence of IM-9 cells were also partially blocked by these MoAbs. These findings suggest that multiple adhesion pathways may mediate adherence of myeloma cell lines to BMSCs, localizing tumour cells in the marrow microenvironment and triggering IL-6 secretion by BMSCs which may augment tumour cell growth.

Role of cytokines in the pathogenesis of monoclonal gammopathies

OBJECTIVE

To review data that postulate a role for cytokines and oncogenes in the pathogenesis of monoclonal gammopathies.

DESIGN

Published studies that provide evidence of the clinical progression of normal B cells to monoclonal gammopathy of undetermined significance (MGUS) to active myeloma are discussed.

RESULTS

On the basis of mouse plasmacytoma models, increased expression of c-myc in B lymphocytes may be the initial oncogenic event that leads to MGUS in humans. Over time, this monoclonal subpopulation may acquire additional genetic abnormalities, such as aberrant interleukin (IL) 1 beta expression. Because IL 1 beta has potent osteoclast activating factor activity, increased production of IL 1 beta by monoclonal plasma cells may be the genetic event responsible for the progression of MGUS to myeloma. The in vivo plasma cell labeling index (proliferative rate) is the most powerful prognostic factor in patients with myeloma. The proliferative compartment observed in myeloma may parallel normal B-cell development because cytoplasmic immunoglobulin-positive cells with the ability to proliferate exist normally. With continued progression of disease, the ratio of proliferating monoclonal plasmablasts to nonproliferating monoclonal plasma cells may increase under the influence of cytokines such as IL 6.

CONCLUSION

A more complete understanding of the basic biologic features of myeloma should lead to innovative therapies in the future.

The activation of human blood coagulation factor X on the surface of endothelial cells: a comparison with various vascular cells, platelets and monocytes

Rates of factor X activation on endothelial cells were compared with activation rates on other vascular cells, platelets, monocytes and negatively charged phospholipid vesicles. Factor VIIa-mediated factor X activation was observed on smooth muscle cells and fibroblasts in the absence of cell-perturbing agents, whereas endothelial cells required activation in order to allow extrinsic activation of factor X. On the other hand, unperturbed endothelial cells did promote intrinsic, factor VIII/IXa-dependent activation of factor X. The rate of factor X activation on these cells was about one-sixth of that on ionophore A23187-stimulated platelets. Also, smooth muscle cells and fibroblasts were able to activate factor X through the intrinsic pathway, although to a lesser extent than endothelial cells. Monocytes were ineffective in this respect. Prothrombin fragment 1, the prothrombin fragment containing the gamma-carboxyglutamic acid domain known to mediate binding of vitamin K-dependent coagulation factors to phospholipid surfaces, inhibited factor VIII/IXa-dependent factor X activation on endothelial cells (IC50 3.2 microM) to a lesser extent than on phospholipid vesicles (IC50 0.2 microM). Therefore, besides negatively charged phospholipids, other membrane constituents seem to be involved in endothelial cell mediated, intrinsic activation of factor X. Perturbation of endothelial cells with phorbol myristate acetate (PMA) or lipopolysaccharide (LPS) was without effect on intrinsic activation of factor X. This observation indicates that membrane constituents of endothelial cells involved in factor VIII/IXa-dependent activation of factor X are constitutively expressed.

Diagnostic criteria and histologic grading in multiple myeloma: histologic and immunohistologic analysis of 176 cases with clinical correlation

Diagnostic criteria in myeloma have not been completely standardized or tested for accuracy; furthermore, marrow findings of prognostic value have not been clearly identified. We studied 176 patients with myeloma to determine the relative value of marrow differential, tissue sections, and immunohistology singly or in concert in the diagnosis of myeloma and to correlate morphologic features with prognosis. Controls were patients with benign marrow plasmacytosis. Homogeneous nodules of plasma cells at least 1/2 high-power field and/or monotypic aggregates of plasma cells filling at least one interfatty marrow space correctly identified myeloma in 83.5% of cases, with no false positives. The current numerical criteria of marrow plasmacytosis > or = 10% occurred in 17.1% of the controls, and 39.7% of patients with myeloma had less than 10% marrow plasmacytosis at presentation. Myeloma was graded histologically into categories of none/minimal, moderate, and marked dysplasia on the basis of dysplastic features and mitoses; these categories correlated well with clinical outcome, with median length of survival of 32.9, 25.2, and 12.9 months, respectively (overall median length of survival of 123 patients with myeloma, 29.2 months). Packing of marrow by tumor and mitoses measuring at least 5/high-power field regardless of grade also was associated with a poor prognosis (median lengths of survival, 15.2 and 11 months, respectively). Myeloma may be diagnosed in the great majority of cases by demonstrating homogeneous nodules and/or monotypic aggregates of plasma cells in the marrow. Prognostic features were shown to include marked dysplasia, mitoses, packing of marrow by tumor, and clinical stage.

Use of granulocyte colony-stimulating factor (G-CSF) for mobilizing peripheral blood stem cells: risk of mobilizing clonal myeloma cells in patients with bone marrow infiltration

Peripheral blood stem cells have been used for autologous reconstitution of haemopoiesis after high dose cytotoxic therapy and produce similar disease response rates as autologous bone marrow transplants. Peripheral blood stem cell transplants are an especially attractive option for patients in whom marrow harvest is not feasible due to bone marrow damage or infiltration. Recombinant growth factors mobilize adequate numbers of stem cells from the marrow but their effect on tumour cell circulation kinetics is not known. We report a patient with multiple myeloma and bone marrow infiltration in whom the use of G-CSF for stem cell mobilization led to release of plasma cells into the peripheral circulation and contamination of the stem cell harvest.

Cytotoxicity of a novel anti-ICAM-1 immunotoxin on human myeloma cell lines

We have generated a murine monoclonal antibody (UV3) which recognizes an epitope on ICAM-1 expressed on myeloma cells. By flow cytometric analysis, the epitope on ICAM-1 recognized by this antibody is strongly expressed on human myeloma cells, pre-B leukemia cells and Burkitt's lymphoma cell lines. Most human T cell lines are weakly positive. The antibody does not react with red blood cells, polymorphonuclear leukocytes (PMNs) or resting B lymphocytes from normal donors, and reacts very weakly with resting T cells. Immunohistochemical assays indicate that the antibody does not react with normal liver, kidney, heart, brain, thymus or lung. An immunotoxin (IT) was prepared by coupling UV3 to deglycosylated ricin A-chain (dgA). In protein synthesis inhibition assays it was highly cytotoxic to the human myeloma cell lines HS-SULTAN (IC50 = 1 x 10(-11)M) and ARH-77 (IC50 = 9 x 10(-11)M), but not to cell lines of T cell lineage or most cell lines of the B lineage. Our results suggest that the UV3-dgA may have therapeutic potential for the treatment of human multiple myeloma.

Multiple myeloma: 'early' plasma cell phenotype identifies patients with aggressive biological and clinical characteristics

The immunological phenotype of bone marrow myeloma cells and peripheral blood lymphocytes was evaluated in 38 untreated myeloma patients. A striking increase of monotypic cells expressing the same light chain as the M component was observed in bone marrow from 18/38 (47%) patients. A two-colour analysis clarified that the majority of myeloma cells co-expressed plasma cell and B lymphocyte markers (cyIg, CD38, CD56 and sIg), and were regarded as early-plasma cells (early-PC). In the remaining patients, myeloma cells expressed plasma cell markers only (late-PC). Phenotype corresponded to a distinct morphological pattern: early-PC showed a lympho-plasmocytoid feature with significantly lower diameters than late-PC (12.1 v 14.8 microns, P < 0.007). Moreover, the plasma cell labelling index was significantly increased in early-PC patients (1.2 v 0.5%, P < 0.04). In peripheral blood from patients with early-PC, monotypic cells co-expressing sIg and CD38, CD56, but not CD19, were also detected. These data suggest a recirculation of early-PC. Myeloma cells maintained their phenotypic pattern during the course of the disease. This observation suggests that the degree of maturation is an intrinsic characteristic of the myeloma cell population in individual patients. The evaluation of prognostic factors, such as beta 2-microglobulin, C-reactive protein and neopterin, showed a statistically significant increase in the early-PC patients, suggesting a poor outcome. In conclusion, myeloma cell phenotype allows identification of a myeloma variant with aggressive biological and clinical characteristics.

A novel flow cytometric assay for the quantification of adhesion of subsets within a heterogeneous cell population; analysis of lymphocyte function-associated antigen-1 (LFA-1)-mediated binding of bone marrow-derived primary tumour cells of patients with multiple myeloma

In a previous study the expression of the adhesion molecule LFA-1 on tumour cells in patients suffering from multiple myeloma (MM) was correlated with growth of the malignant plasma cells in vivo. Here we describe a novel in vitro flow cytometric adhesion assay (FCAA) which, based on scatter and fluorescence properties, was used to analyse the contribution of the LFA-1/intercellular adhesion molecule-1 (ICAM-1) adhesion pathway in the binding of bone marrow (BM)-derived LFA-1-positive primary tumour cells of patients with MM to interferon-gamma (IFN-gamma)-activated, ICAM-1-positive, human venous umbilical endothelial cells (huVEC) in vitro. To validate the FCAA, cells from different myeloma cell lines were labelled with the fluorescent dye CFDA or stained for CD38 expression, and LFA-1-mediated adhesion to IFN-gamma-activated endothelial cells was quantified. Results obtained with the FCAA were compared with a conventional adhesion assay employing 51Cr-labelled cells. Statistical analysis revealed that both assays gave similar results. This allowed analysis of the contribution of LFA-1 to the adhesive potential of malignant plasma cells in bone marrow mononuclear cells (BMMC) from MM patients to IFN-gamma-activated endothelial cells. The results prove that LFA-1 expressed on bone marrow-derived plasma cells from MM patients can be used for cellular adhesion to ICAM-1 expressed on adherent growing cells, and are suggestive for a role of the LFA-1/ICAM-1 adhesion pathway in the pathophysiology of MM. The FCAA described in this study is a generally applicable assay, allowing analysis of the interaction of distinct subpopulations with in vitro grown adherent cells of different origin.

ZB51: a monoclonal antibody reactive with human plasma cells

Several monoclonal antibodies have been raised in the past which react with human plasma cells but they have all shown additional reactions with other cell types. In this paper we describe a new monoclonal antibody, ZB51, which recognizes an intracellular antigen in normal plasma cells in cryostat tissue sections and cell smears, and which also reacts with neoplastic cells in most cases of myeloma and with plasma cell lines. The antibody shows minimal reactivity with a few eosinophils and myelocytes in bone marrow and stains a myeloid cell line. Whilst normal epithelium is not labelled, antibody ZB51 stains two carcinoma cell lines. Although it was not possible to characterize the target antigen in terms of molecular weight, the reactivity of antibody ZB51 with normal and neoplastic plasma cells makes it a useful new immunocytochemical reagent.

Multiple myeloma: the biology of malignant plasma cells

Multiple myeloma remains a difficult disorder to treat and cures are virtually unknown. Most modalities of treatment have been tried on an empirical basis, and a greater understanding of the nature of myeloma progenitors may lead to more specific therapies. In the past few years interest in the biology of myeloma plasma cells has increased and the current state of knowledge is summarised in this review. Myeloma clonogenic, or colony, assays have been attempted by many groups. Despite this, no direct equivalent is available of the CFU-GM assay for granulocyte-macrophage progenitors in normal marrow. No published methods have been exported widely to other laboratories. Recently, myeloma plasma cells were found to express a wide range of adhesion molecules permitting cell to cell and cell to stroma interactions. This finding may explain the difficulty of myeloma colony assays, since adhesive clumping must be prevented. The observation that interleukin (IL)-6 can stimulate myeloma plasma cells led to further work with other cytokines such as IL-3 and GM-CSF. The precise role of IL-6 in the usual case of bone marrow myeloma remains unclear however.