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Multiple myeloma (MM) is a cancer of plasma cells (PCs) expressing immunoglobulin heavy chain (IgH) postswitch isotypes. The discovery of earlier stage cells related to postswitch PCs, called preswitch clonotypic IgM (cIgM) cells led to the hypothesis that cIgM cells may be MM progenitors, replenishing the tumor throughout malignancy. cIgM cells may do this by undergoing class switch recombination (CSR), a process detectable in postswitch PCs as multiple IgH switch junctions associated with a single clonotypic IgH V/D/J. We addressed this with a specific clonotypic-switch polymerase chain reaction (PCR), informative for 32 of 41 cases. Here we made 2 significant discoveries: (1) in all cases, we detected only a single clonotypic switch fragment that persists over time (1-7.6 years), and (2) we detected ongoing mutation upstream of the switch junction in 5 of 6 patients, often targeting the intronic enhancer, a key control region in IgH expression. The presence of a single, unchanging clonotypic switch junction suggests that cIgM cells are not MM-PC progenitors; rather, postswitch PCs arise from a single cIgM cell, and MM-PC progenitors reside in the postswitch population. Furthermore, mutations revealed here provide a new marker to identify MM-PC progenitors and aggressive clones that evolve throughout malignancy.

Analysis of clonotypic isotype class switching (CSR) in Waldenström macroglobulinemia (WM) and IgM monoclonal gammopathy of undetermined significance (MGUS) reveals a normal initial phase of B-cell activation as determined by constitutive and inducible expression of activation-induced cytidine deaminase (AID). Switch μ (Sμ) analysis shows that large deletions are not common in WM or IgM MGUS. In CD40L/IL-4-stimulated WM cultures from 2 patients, we observed clonotypic IgG exhibiting intraclonal homogeneity associated with multiple hybrid Sμ/Sγ junctions. This suggests CSR had occurred within WM cells. Nevertheless, the estimated IgG/IgM-cell frequency was relatively low (1/1600 cells). Thus, for the majority of WM B cells, CSR does not occur even when stimulated in vitro, suggesting that the WM cell is constitutively unable to or being prevented from carrying out CSR. In contrast to WM, the majority of IgM MGUS clones exhibit intraclonal heterogeneity of IgH VDJ. Furthermore, most IgM MGUS accumulate more mutations in the upstream Sμ region than do WM, making them unlikely WM progenitors. These observations suggest that switch sequence analysis may identify the subset of patients with IgM MGUS who are at risk of progression to WM.

In this study, we show that the hyaluronan synthase 1 (HAS1) gene undergoes aberrant intronic splicing in multiple myeloma (MM). In addition to HAS1 full length (HAS1FL), we identify 3 novel splice variants of HAS1, HAS1Va, HAS1Vb, and HAS1Vc, detected in patients with MM or monoclonal gammopathy of undetermined significance (MGUS). HAS1Vb and HAS1Vc undergo intronic splicing with creation of a premature stop codon. MM cells expressing one or more HAS1 variants synthesize extracellular and/or intracellular hyaluronan (HA). Expression of the HAS1Vb splice variant was significantly correlated with reduced survival (P = .001). Together, alternative HAS1 gene splicing, the correlations between HAS1 splicing and HA synthesis, and the correlations between HAS1 splicing and reduced survival of MM patients support the hypothesis that the family of HAS1 protein plays a significant role in disease progression. Further, expression of HAS1Vb, in conjunction with HAS1FL and/or other HAS1 variants, may lead to accumulation of intracellular HA molecules and an impact on receptor for HA-mediated motility (RHAMM)-mediated mitotic abnormalities in MM. This study highlights the potential importance of HAS1 and its alternative splicing in pathophysiology of MGUS and MM. (Blood. 2005;105: 4836-4844)

Genetic variations in the hyaluronan synthase 1 gene (HAS1) influence HAS1 aberrant splicing. HAS1 is aberrantly spliced in malignant cells from multiple myeloma (MM) and Waldenstrom macroglobulinemia (WM), but not in their counterparts from healthy donors. The presence of aberrant HAS1 splice variants predicts for poor survival in multiple myeloma (MM). We evaluated the influence of inherited HAS1 single nucleotide polymorphisms (SNP) on the risk of having a systemic B cell malignancy in 1414 individuals compromising 832 patients and 582 healthy controls, including familial analysis of an Icelandic kindred. We sequenced HAS1 gene segments from 181 patients with MM, 98 with monoclonal gammopathy of undetermined significance (MGUS), 72 with Waldenstrom macroglobulinemia (WM), 169 with chronic lymphocytic leukemia (CLL), as well as 34 members of a monoclonal gammopathy-prone Icelandic family, 212 age-matched healthy donors and a case-control cohort of 295 breast cancer patients with 353 healthy controls. Three linked single nucleotide polymorphisms (SNP) in HAS1 intron3 are significantly associated with B-cell malignancies (range p = 0.007 to p = 10(-5)), but not MGUS or breast cancer, and predict risk in a 34 member Icelandic family (p = 0.005, Odds Ratio = 5.8 (OR)), a relatively homogeneous cohort. In contrast, exon3 SNPs were not significantly different among the study groups. Pooled analyses showed a strong association between the linked HAS1 intron3 SNPs and B-cell malignancies (OR = 1.78), but not for sporadic MGUS or for breast cancer (OR

Although the mechanism(s) underlying mobilization of hematopoietic progenitor cells (HPCs) is unknown, detachment from the bone marrow (BM) microenvironment and motility are likely to play a role. This work analyzes the motile behavior of HPCs and the receptors involved. CD34+45lo/medScatterlo/med HPCs from granulocyte colony-stimulating factor (G-CSF)–mobilized blood and mobilized BM were compared with steady-state BM for their ability to bind hyaluronan (HA), their expression of the HA receptors RHAMM and CD44, and their motogenic behavior. Although RHAMM and CD44 are expressed by mobilized blood HPCs, function blocking monoclonal antibodies (MoAbs) identified RHAMM as a major HA binding receptor, with a less consistent participation by CD44. Permeabilization of mobilized blood HPCs showed a pool of intracellular (ic) RHAMM and a smaller pool of icCD44. In contrast, steady-state BM HPCs have significantly larger pools of icRHAMM and icCD44. Also, in contrast to mobilized blood HPCs, for steady-state BM HPCs, MoAbs to RHAMM and CD44 act as agonists to upregulate HA binding. The comparison between mobilized and steady-state BM HPCs suggests that G-CSF mobilization is associated with depletion of intracellular stores of HA receptors and modulates HA receptor usage. To confirm that mobilization alters the HA receptor distribution and usage by HPCs, samples of BM were collected at the peak of G-CSF mobilization in parallel with mobilized blood samples. HA receptor distribution of mobilized BM HPCs was closely matched with mobilized blood HPCs and different from steady-state BM HPCs. Mobilized BM HPCs had lower pools of icHA receptors, similar to those of mobilized blood HPCs. Treatment of mobilized BM HPCs with anti-RHAMM MoAb decreased HA binding, in contrast to steady-state BM HPCs. Thus, G-CSF mobilization may stimulate an autocrine stimulatory loop for HPCs in which HA interacts with basal levels of RHAMM and/or CD44 to stimulate receptor recycling. Consistent with this, treatment of HPCs with azide, nystatin, or cytochalasin B increased HA binding, implicating an energy-dependent process involving lipid rafts and the cytoskeleton. Of the sorted HPCs, 66% were adherent and 27% were motile on fibronectin plus HA. HPC adherence was inhibited by MoAbs to β1 integrin and CD44, but not to RHAMM, whereas HPC motility was inhibited by MoAb to RHAMM and β1 integrin, but not to CD44. This finding suggests that RHAMM and CD44 play reciprocal roles in adhesion and motility by HPCs. The G-CSF–associated alterations in RHAMM distribution and the RHAMM-dependent motility of HPCs suggest a potential role for HA and RHAMM in trafficking of HPCs and the possible use of HA as a mobilizing agent in vivo.

Although the mechanism(s) underlying mobilization of hematopoietic progenitor cells (HPCs) is unknown, detachment from the bone marrow (BM) microenvironment and motility are likely to play a role. This work analyzes the motile behavior of HPCs and the receptors involved. CD34+45lo/medScatterlo/med HPCs from granulocyte colony-stimulating factor (G-CSF)–mobilized blood and mobilized BM were compared with steady-state BM for their ability to bind hyaluronan (HA), their expression of the HA receptors RHAMM and CD44, and their motogenic behavior. Although RHAMM and CD44 are expressed by mobilized blood HPCs, function blocking monoclonal antibodies (MoAbs) identified RHAMM as a major HA binding receptor, with a less consistent participation by CD44. Permeabilization of mobilized blood HPCs showed a pool of intracellular (ic) RHAMM and a smaller pool of icCD44. In contrast, steady-state BM HPCs have significantly larger pools of icRHAMM and icCD44. Also, in contrast to mobilized blood HPCs, for steady-state BM HPCs, MoAbs to RHAMM and CD44 act as agonists to upregulate HA binding. The comparison between mobilized and steady-state BM HPCs suggests that G-CSF mobilization is associated with depletion of intracellular stores of HA receptors and modulates HA receptor usage. To confirm that mobilization alters the HA receptor distribution and usage by HPCs, samples of BM were collected at the peak of G-CSF mobilization in parallel with mobilized blood samples. HA receptor distribution of mobilized BM HPCs was closely matched with mobilized blood HPCs and different from steady-state BM HPCs. Mobilized BM HPCs had lower pools of icHA receptors, similar to those of mobilized blood HPCs. Treatment of mobilized BM HPCs with anti-RHAMM MoAb decreased HA binding, in contrast to steady-state BM HPCs. Thus, G-CSF mobilization may stimulate an autocrine stimulatory loop for HPCs in which HA interacts with basal levels of RHAMM and/or CD44 to stimulate receptor recycling. Consistent with this, treatment of HPCs with azide, nystatin, or cytochalasin B increased HA binding, implicating an energy-dependent process involving lipid rafts and the cytoskeleton. Of the sorted HPCs, 66% were adherent and 27% were motile on fibronectin plus HA. HPC adherence was inhibited by MoAbs to β1 integrin and CD44, but not to RHAMM, whereas HPC motility was inhibited by MoAb to RHAMM and β1 integrin, but not to CD44. This finding suggests that RHAMM and CD44 play reciprocal roles in adhesion and motility by HPCs. The G-CSF–associated alterations in RHAMM distribution and the RHAMM-dependent motility of HPCs suggest a potential role for HA and RHAMM in trafficking of HPCs and the possible use of HA as a mobilizing agent in vivo.

The receptor for hyaluronan (HA)-mediated motility (RHAMM) controls motility by malignant cells in myeloma and is abnormally expressed on the surface of most malignant B and plasma cells in blood or bone marrow (BM) of patients with multiple myeloma (MM). RHAMM cDNA was cloned and sequenced from the malignant B and plasma cells comprising the myeloma B lineage hierarchy. Three distinct RHAMM gene products, RHAMMFL, RHAMM−48, and RHAMM−147, were cloned from MM B and plasma cells. RHAMMFL was 99% homologous to the published sequence of RHAMM. RHAMM−48 and RHAMM−147 variants align with RHAMMFL, but are characterized by sequence deletions of 48 bp (16 amino acids [aa]) and 147 bp (49 aa), respectively. The relative frequency of these RHAMM transcripts in MM plasma cells was determined by cloning of reverse-transcriptase polymerase chain reaction (RT-PCR) products amplified from MM plasma cells. Of 115 randomly picked clones, 49% were RHAMMFL, 47% were RHAMM−48, and 4% were RHAMM−147. All of the detected RHAMM variants contain exon 4, which is alternatively spliced in murine RHAMM, and had only a single copy of the exon 8 repeat sequence detected in murine RHAMM. RT-PCR analysis of sorted blood or BM cells from 22 MM patients showed that overexpression of RHAMM variants is characteristic of MM B cells and BM plasma cells in all patients tested. RHAMM also appeared to be overexpressed in B lymphoma and B-chronic lymphocytic leukemia (CLL) cells. In B cells from normal donors, RHAMMFL was only weakly detectable in resting B cells from five of eight normal donors or in chronically activated B cells from three patients with Crohn’s disease. RHAMM−48 was detectable in B cells from one of eight normal donors, but was undetectable in B cells of three donors with Crohn’s disease. RHAMM−147 was undetectable in normal and Crohn’s disease B cells. In situ RT-PCR was used to determine the number of individual cells with aggregate RHAMM transcripts. For six patients, 29% of BM plasma cells and 12% of MM B cells had detectable RHAMM transcripts, while for five normal donors, only 1.2% of B cells expressed RHAMM transcripts. This work suggests that RHAMMFL, RHAMM−48, and RHAMM−147 splice variants are overexpressed in MM and other B lymphocyte malignancies relative to resting or in vivo–activated B cells, raising the possibility that RHAMM and its variants may contribute to the malignant process in B-cell malignancies such as lymphoma, CLL, and MM.

In multiple myeloma (MM), the VDJ rearrangement of the immunoglobulin heavy chain expressed by MM plasma cells provides a unique clonotypic marker. Although clonotypic MM cells have been found in the circulation, their number has been controversial. Our objective was to provide direct evidence, using single-cell assays, for the frequency of clonotypic cells in blood of 18 MM patients, and to confirm their identity as B cells. The clonotypic Ig heavy-chain (IgH) VDJ was determined from single plasma cells using consensus reverse transcriptase-polymerase chain reaction (RT-PCR), subcloning, and sequencing. For all patients, using patient-specific primers, clonotypic transcripts were amplified from 10 or more individual plasma cells. Using in situ RT-PCR, for all patients greater than 80% of plasma cells were found to be clonotypic. Three separate methods, RT-PCR, single-cell RT-PCR, and in situ RT-PCR, were used to analyze clonotypic cells in peripheral blood mononuclear cells (PBMC) from MM patients. Sequencing of the IgH transcripts expressed by individual cells obtained by limiting dilution of freshly isolated PBMC from a MM patient showed that all B cells expressed an identical CDR3. This intraclonal homogeneity indicates an escape from antigenic-selection, characteristic of malignant B cells. For this patient, the frequency of clonotypic PBMC, about 25%, was comparable to the number of PBMC B cells (34%). Because the PBMC included less than 1% plasma cells, virtually all clonotypic PBMC must be B cells. Using single-cell RT-PCR, clonotypic IgH transcripts were identified in individual sorted B cells from blood. To accurately quantify the number of clonotypic B cells, sorted B cells derived from 18 MM patients (36 samples) and 18 healthy donors (53 samples) were analyzed using in situ RT-PCR with patient-specific primers. Clonotypic transcripts were not detectable among normal B cells. For the 18 MM patients, a mean of 66% ± 4% (SE) of blood B cells were clonotypic (range, 9% to 95%), with mean absolute number of 0.15 ± .02 × 109/L blood. Over time in individual patients, conventional chemotherapy transiently decreased circulating clonotypic B cells. Their numbers were increased in granulocyte colony-stimulating factor (G-CSF)– mobilized blood of one patient. However, clonotypic B cells of a one patient became undetectable after allogeneic transplant, correlating with complete remission. Although contributions to MM spread and progression is likely, their malignant status and impact has yet to be clarified. Their high frequency in the blood, and their resistence to conventional chemotherapy suggests that the number of circulating clonotypic cells should be clinically monitored, and that therapeutic targeting of these B cells may benefit myeloma patients. © 1998 by The American Society of Hematology.

We investigated the ability of blood B cells, bone marrow (BM) plasma cells, and terminal leukemic plasma cells (T-PCL) from patients with multiple myeloma (MM) to migrate on extracellular matrix proteins. Hyaluronan (HA), but not collagen type I, collagen type IV, or laminin, promoted migration of MM blood B cells, as determined by time-lapse video microscopy. Between 13% and 20% of MM blood B cells migrated on HA with an average velocity of 19 micron/min, and greater than 75% of MM blood B cells exhibited vigorous cell movement and plasma membrane deformation, as did circulating T-PCL and extraskeletal plasma cells from patients with MM. In contrast, plasma cells obtained from BM of patients with MM lacked motility on all substrates tested and did not exhibit cell membrane protrusions or cellular deformation. MM blood B cells and MM plasma cells from all sources examined expressed the HA- binding receptors receptor for HA-mediated motility (RHAMM) and CD44. On circulating MM B cells, both RHAMM and CD44 participated in HA- binding, indicating their expression ex vivo in an activated conformation. In contrast, for the majority of BM plasma cells in the majority of patients with MM, expression of RHAMM or CD44 was not accompanied by HA binding. A minority of patients did have HA-binding BM plasma cells, involving both RHAMM and CD44, as evidenced by partial blocking with monoclonal antibodies (MoAbs) to RHAMM or to CD44. Despite HA binding by both RHAMM and CD44, migration of MM blood B cells on HA was inhibited by anti-RHAMM but not by anti-CD44 MoAbs, indicating that RHAMM but not CD44 mediates motility on HA. Thus, circulating B and plasma cells in MM exhibit RHAMM- and HA-dependent motile behavior indicative of migratory potential, while BM plasma cells are sessile. We speculate that a subset(s) of circulating B or plasma cells mediates malignant spread in myeloma.

Multiple myeloma (MM) is characterized by a plasma cell infiltrate of the bone marrow (BM). However, late-stage monotypic B cells have been detected in the blood. This work analyzes the effects of clinical treatment on late stage CD19+ B cells present in 752 blood samples from 152 MM patients. MM patients have 2 to 8 times as many circulating CD19+ cells as do normal donors. Analysis of the Ig heavy chain (IgH) gene rearrangements using polymerase chain reaction indicates that the CD19+ population includes cells sharing the same clonotypic CDR3 region as is detected in the BM plasma cells, for patients analyzed during chemotherapy or in relapse. They are also monotypic as defined by their cytoplasmic or surface expression of Ig kappa or lambda light chain. The light chain restriction is the same as that of the BM plasma cells. Individual patients observed over 1- to 2-year periods exhibit considerable variation in the number of B cells present in blood; this number does not correlate with the concentration of serum monoclonal Ig. The monoclonal blood CD19+ cells are not eliminated by any of the chemotherapy regimens analyzed and remain at high levels during transient remissions. Patients in the progressive phase of disease or in relapse have significantly higher numbers of B cells than do patients in transient remission or untreated patients. During periods when the quantity of blood B cells approaches normal, phenotypically their quality is highly abnormal, with physical and phenotypic heterogeneity. Most B cells express CD45R0, a high density of CD38, and CD56 characteristic of late-stage B or pre-plasma cells. CD38hi blood B cells had a cyclical presence. We conclude that monoclonal B cells in the blood of myeloma patient populations include drug-resistant reservoirs of clonotypic cells that may underlie relapse.

The peripheral blood lymphocytes from 42 patients with multiple myeloma (MM) and 13 patients with monoclonal gammopathy of undetermined significance (MGUS) were studied by three-color immunofluorescence (IF) using antibodies directed to a broad range of B-cell markers (CD19, CD20, CD21, CD24), CALLA (CD10), PCA-1 (a plasma cell marker), and to the high and low molecular weight isoforms of the leukocyte common antigen, CD45RA (p205/220) and CD45RO (p 180). CD45RA is expressed on pre-B and B cells, and a transition from CD45RA to CD45RO defines differentiation towards plasma cells. Peripheral blood mononuclear cells (PBMC) from patients with myeloma included a large subset of B- lineage cells (mean of 39% to 45%) that were CALLA+ and PCA-1+ in all patients studied, including newly diagnosed patients and patients undergoing chemotherapy. Southern blot analysis indicated the presence of monoclonal Ig rearrangements in PBMC and a substantial reduction in the germ-line bands consistent with the presence of a large monoclonal B-cell subset. Avoidance of purification methods involving depletion of adherent cells was essential for detection of the abnormal B cells. Phenotypically, this abnormal B-cell population corresponded to late B or early pre-plasma cells (20% to 80% of PBMC), as defined by the concomitant expression of low densities of CD19 and CD20, moderate densities of CALLA and PCA-1, and strong expression of CD45RO on all B cells, with weakly coexpressed CD45RA on a small proportion. Heterogeneity in the expression of CD45RA and CD45RO within the abnormal B-cell population from any given patient suggested multiple differentiation stages. Abnormal B cells similar to those in MM were also detected in MGUS, although as a lower proportion of PBMC (26%). Abnormal B cells from patients with MGUS expressed predominantly the CD45RO isoform, but had a lower proportion of CALLA+ and PCA-1+ cells than were found on B cells from MM. This work indicates that the large subset of circulating monoclonal B lymphocytes from myeloma patients are at a late stage in B-cell differentiation, continuously progressing towards the plasma cell stage.

To characterize genetic contributions toward aberrant splicing of the hyaluronan synthase 1 (HAS1) gene in multiple myeloma (MM) and Waldenstrom macroglobulinemia (WM), we sequenced 3616 bp in HAS1 exons and introns involved in aberrant splicing, from 17 patients. We identified a total of 197 HAS1 genetic variations (GVs), a range of 3 to 24 GVs/patient, including 87 somatic GVs acquired in splicing regions of HAS1. Nearly all newly identified inherited and somatic GVs in MM and/or WM were absent from B chronic lymphocytic leukemia, nonmalignant disease, and healthy donors. Somatic HAS1 GVs recurred in all hematopoietic cells tested, including normal CD34+ hematopoietic progenitor cells and T cells, or as tumor-specific GVs restricted to malignant B and plasma cells. An in vitro splicing assay confirmed that HAS1 GVs direct aberrant HAS1 intronic splicing. Recurrent somatic GVs may be enriched by strong mutational selection leading to MM and/or WM.

Multiple myeloma (MM) is a B-lineage malignancy characterized by diverse genetic subtypes and clinical outcomes. The recurrent immunoglobulin heavy chain (IgH) switch translocation, t(4;14)(p16;q32), is associated with poor outcome, though the mechanism is unclear. Quantitative reverse-transcription–polymerase chain reaction (RT-PCR) for proposed target genes on a panel of myeloma cell lines and purified plasma cells showed that only transcripts originating from the WHSC1/MMSET/NSD2 gene are uniformly dysregulated in all t(4;14)POS patients. The different transcripts detected, multiple myeloma SET domain containing protein (MMSET I), MMSET II, Exon 4a/MMSET III, and response element II binding protein (RE-IIBP), are produced by alternative splicing and alternative transcription initiation events. Translation of the various transcripts, including those from major breakpoint region 4-2 (MB4-2) and MB4-3 breakpoint variants, was confirmed by transient transfection and immunoblotting. Green fluorescent protein (GFP)–tagged MMSET I and II, corresponding to proteins expressed in MB4-1 patients, localized to the nucleus but not nucleoli, whereas the MB4-2 and MB4-3 proteins concentrate in nucleoli. Cloning and localization of the Exon 4a/MMSET III splice variant, which contains the protein segment lost in the MB4-2 variant, identified a novel protein domain that prevents nucleolar localization. Kinetic studies using photobleaching suggest that the breakpoint variants are functionally distinct from wild-type proteins. In contrast, RE-IIBP is universally dysregulated and also potentially functional in all t(4;14)POS patients irrespective of fibroblast growth factor receptor 3 (FGFR3) expression or breakpoint type.

Contains fulltext : 48545.pdf (Publisher’s version ) (Closed access) Cancer testis antigens (CTAs) are tumor-specific antigens that may be useful targets for cancer vaccines. Here, CTA expression was examined in multiple myeloma (MM), a B-cell cancer characterized by malignant plasma cells (PCs) in the bone marrow (BM), and monoclonal gammopathy of undetermined significance (MGUS), a condition that can progress to MM. We screened a panel of patient BMs at different stages of malignancy for CTA expression by reverse transcription polymerase chain reaction RT-PCR. Here, SSX (synovial sarcoma, X chromosome) emerged as a promising candidate for an MM vaccine, having a profile similar to currently studied CTA, NY-ESO-1, and MAGE. SSX1, 2, 4, and 5 expression was studied further in 114 MM (total SSX, 61% of patients; SSX1, 42%; SSX2, 23%; SSX4, 38%; SSX5, 35%), 45 MGUS (total SSX, 24% of patients; SSX1, 9%; SSX4, 20%), and 12 control (0/12, 0%) subjects. Several expression patterns were observed, the most predominant being co-expression of SSX1, 2, 4, and 5 (called group A expression, in 20% of MM), which correlated with reduced survival (P=0.0006). Of the four genes, SSX2 had the strongest association with reduced survival (P=0.0001). SSX protein expression ranged from 13.5% of PCs in an SSX1/SSX4 co-expressor to as high as 88% of PCs in group A expressor, exceeding reported frequencies of NY-ESO-1 and MAGE in MM. In single PCs from group A patients, we detected variable degrees of SSX co-expression, emphasizing the heterogeneity of CTA expression within tumor cell populations. These results demonstrate that SSX is a frequently expressed CTA in MM and highlight its potential as an MM vaccine candidate.

Analysis of clonotypic immunoglobulin M (IgM) from 15 patients with Waldenstrom macroglobulinemia (WM) showed a strong preferential use of the VH3/JH4 gene families. Identification of the WM IgM V/D/J was validated using single-cell analysis, confirming its presence in most B cells. Despite the extensive hypermutated VH genes in 13 of 15 patients, statistical analysis of framework/complementary-determining region (FR/CDR) mutation patterns suggests that they might have escaped antigenic selection. Neither intraclonal diversity nor isotype switching was detectable. Membranous and secreted forms of clonotypic IgM transcripts were present in bone marrow and blood. Single-cell analysis showed that clonotypic B cells coexpress CD20, surface IgM (sIgM), and sIgD but that they lack CD138. Most B cells lacked memory marker CD27 despite their hypermutated variable regions otherwise suggestive of memory status. At diagnosis, circulating B cells in WM are largely clonotypic. However, when monoclonal IgM levels are decreased, clonotypic frequencies are substantially reduced despite elevated CD20+ cells, shown to be polyclonal by DNA sequencing and CDR3 fragment analysis. Thus, WM includes the expansion of circulating, polyclonal B cells. Overall, this work suggests that WM may originate from a largely VH3-restricted, somatically mutated, predominantly CD27-IgM+IgD+ population that cannot undergo class switching, suggestive of B cells that might have bypassed the germinal center. (Blood. 2004;104:2134-2142)

The unique IgM VDJ sequence that characterizes the malignant clone in Waldenstrom's macroglobulinemia (WM), termed clonotypic, was identified for 12 WM patients. The majority of WM patients (92%) had a clonotypic IgM from the VH3 family, with predominantly long CDR3 regions, characteristic of those found in antigen-stimulated populations. Clonotypic IgM transcripts were detected in both blood and bone marrow (BM), clearly identifying a blood-borne compartment of WM. Abnormal numbers of CD20(+) B cells were usually detectable and expressed surface IgM. In most cases these cells also expressed surface IgD. Most WM patients lacked detectable CD138(+) plasma cells in either blood or BM. Longitudinal analysis suggests that phenotypic identification of B cells in blood of WM patients is insufficient for monitoring disease. Although serum IgM had decreased and clonotypic transcripts were very weak for one patient, the number of CD20(+) B cells increased dramatically. The lack of clonotypic transcripts suggests that the majority of these circulating B cells were polyclonal and were not part of the WM clone, indicating that monitoring of clonotypic IgM provides the most accurate identifier of WM cells.

This study analyzed the frequency and clinical significance of t(4;14)(p16;q32) in multiple myeloma (MM) among 208 patients with MM and 52 patients with monoclonal gammopathy of undetermined significance (MGUS); diagnosed between 1994 and 2001. Patients with the translocation were identified using reverse transcription–polymerase chain reaction (RT-PCR) to detect hybrid immunoglobulin heavy chain (IgH)–MMSET transcripts from the der(4) chromosome. We found 31 (14.9%) t(4;14)+ MM patients and 1 (1.9%) t(4;14)+ MGUS patient. IgH-MMSET hybrid transcripts were detected in bone marrow (BM) and blood. Breakpoint analysis revealed that 67.7% of t(4;14)+ patients expressed hybrid transcripts potentially encoding full-length MMSET, whereas the remainder lacked one or more amino terminal exons. Expression of fibroblast growth factor receptor 3 (FGFR3), presumptively dysregulated on der(14), was detected by RT-PCR in only 23 of 31 (74%) patients with t(4;14)+ MM. Patients lacking FGFR3 expression also lacked detectable der(14) products. Longitudinal analysis of 53 MM patients with multiple BM and blood samples showed that, over time, BM from t(4;14)+ patients remained positive and that t(4;14)− patients did not acquire the translocation. IgH-MMSET hybrid transcripts and FGFR3 transcripts disappeared from blood during response to therapy. No correlation was observed between the occurrence of t(4;14) and known prognostic indicators. However, we find the t(4;14) translocation predicts for poor survival (P = .006; median, 644 days vs 1288 days; hazard ratio [HR], 2.0), even in FGFR3 nonexpressors (P = .003). The presence of t(4;14) is also predictive of poor response to first-line chemotherapy (P = .05). These results indicate a significant clinical impact of the t(4;14) translocation in MM that is independent of FGFR3 expression.

Background: The diagnosis of acute myeloid leukemia (AML), response to treatment and disease recurrence are most commonly assessed with bone marrow studies. Recommendations from leading experts (Bain, 2001) and guidelines of the European LeukemiaNET (Dohner, 2010) and the National Comprehensive Cancer network (O’Donnell, 2012) suggest that only the bone marrow aspirate (BMA) is necessary to assess residual disease while the trephine biopsy (TB) is necessary only when an aparticulate BMA is obtained. In contrast, guidelines of the International Council for Standardization in Hematology (Lee, 2008) suggest that BMA and the TB should be routinely performed together as they provide complementary information. Due to these conflicting recommendations we sought to determine whether the TB provides additional sensitivity for the detection of residual leukemia following intensive chemotherapy for AML. Methods: A single centre retrospective chart review was conducted of bone marrow studies of all AML patients who had received intensive chemotherapy from 2004 – 2013. Those lacking a TB were excluded. Residual disease was assessed by morphological examination of the BMA and TB +/- immunostaining but minimal residual disease (MRD) analysis was not performed. Results: 598 bone marrow studies from 227 patients were evaluated. The median age of the patients was 54.6 (range 18 -77) with 70% age < 60. Forty-four percent were female. Cytogenetics were favorable in 30 (13%), intermediate in 146 (64%), high-risk in 44 (19%) and failed in 7 (3%) of the patients. Of the 598 bone marrow samples 198 (33%) were interim marrows performed 14 days following initiation of induction or re-induction chemotherapy (D14 marrow), 251(42%) were recovery marrows following induction/re-induction chemotherapy (EOI marrow) and 149 (25%) were during follow-up. The BMA was considered to be acellular/hypocellular in 31%, hemodilute in 16.4% and aparticulate/pauciparticulate in 27.3% of samples. As per guidelines > 200 cells were counted in 99.8% of the aspirate samples to ascertain remission status. The median length of the TB segments was 1.85 cm (0.2 – 7.0 cm) and it was considered inadequate in 12.7%, of good or excellent quality in 24.9% and adequate for residual disease assessment in the remainder of cases. Approximately 19 % of TB samples had mild to significant hemorrhagic artifact. The bone marrow cellularity could not be assessed in 1.2% of samples but was patchy in 0.5%, aplastic in 2.8%, hypocellular in 36%, normocellular in 23.6%, hypercellular in 23.2%, packed in 6% and was not described in 6.7% of the cases. Residual leukemia was identified in 33.1% of BMA and in 33.3% of TB samples. The BMA and the TB findings were concordant in 562 of 598 (94%) of cases. In 3.5% (21) of cases residual leukemia was seen in the TB but not the BMA whereas in 2.5% (15) of cases the BMA detected residual disease but the TB failed to do so. The TB led to a change in diagnosis from ‘No Leukemia’ to ‘Residual Disease’ in 5.1% of D14 marrows, 3.6% of EOI marrows and in 1.3% of follow-up marrows with no statistically significant difference between the groups (p=0.178). There was no relationship between a change in diagnosis and whether patients received an anthracycline or a non-anthracycline based chemotherapy regimen (4.4% vs. 3.2%, p=1.0). The TB, however, led to a change in diagnosis more commonly in patients with favorable risk karyotype relative to those with intermediate risk karyotype (20% vs. 6.2%, p= 0.02) but not relative to those with unfavorable risk karyotype (20% vs. 13.6%, p=0.53). Hemodilute bone marrow samples were more likely to have a TB related change in diagnosis relative to undilute samples (8.2% versus 2.6%, p=0.01) as were aparticulate/pauciparticulate samples relative to particulate samples (8% vs. 1.9%, p=0.00046). However, in multivariate analysis, only an aparticulate/pauciparticulate sample was associated with TB related change in diagnosis (p=0.015, OR = 3.6). Conclusions: Our data demonstrate that, following intensive chemotherapy, the BMA alone may fail to identify residual leukemia particularly when the BMA is aparticulate/pauciparticulate. In these situations the TB provides additional sensitivity for the detection of residual disease. Further studies are required to evaluate the need for the TB in particulate samples when combined with MRD analysis. Disclosures No relevant conflicts of interest to declare.

BACKGROUND: Anthracycline based treatment for acute myeloid leukemia (AML) can be associated with significant morbidity and mortality amongst older patients or those with significant co-morbidities. Furthermore, for patients with previous anthracycline exposure or preexisting cardiac disease anthracyclines pose an increased risk of cardiotoxicity. For such patients intensive treatment options are limited. The FLAG (fludarabine, cytarabine and filgrastim) regimen is a non-anthracycline based chemotherapy useful for relapsed/refractory AML and as initial therapy for “fit” eligible patients. We present our experience using FLAG as first line therapy in a cohort of newly diagnosed AML patients with advanced age, significant co-morbidities or preexisting cardiac disease. METHODS: A single institution retrospective chart review was undertaken of patients treated with FLAG as frontline therapy from 2004 – 2013 with follow-up until June 2014. All patients were considered ineligible for standard ‘3+7’ treatment by the attending physician. RESULTS: Over the study period 56 patients received FLAG. Due to patient refusal or induction complications bone marrow assessments to ascertain remission status were not performed in 10 patients – to minimize bias these patients were evaluated for toxicity and overall survival (OS) but excluded from complete remission (CR) and relapse free survival (RFS) analysis. Of the 56 patients, 68% were males. The median age was 69 (21 – 80) with 79% aged ≥ 60 and 43% aged ≥ 70. Fifty-five percent (31) of the patients had primary AML and cytogenetics were favorable in 5% (3), intermediate in 66% (37), poor-risk in 21% (12) and failed in 7% (4). Forty-six percent (26) were treated with FLAG due to preexisting cardiac disease and others due to advanced age (20%), poor performance status (16%), co-morbidities (16%) or previous anthracycline exposure (2%). The ages of patients treated with FLAG due to cardiac disease or other reasons was similar (63.5 years vs. 66.9 years, p=0.27). Amongst patients with cardiac disease a pre-chemotherapy cardiac evaluation revealed wall motion abnormalities in 39% and an ejection fraction (EF) ranging from 33% - 81% with a borderline (≤ 50-51%) EF in 46%. Febrile neutropenia was observed in 82% (46) of patients, 27% (15) required intensive care support and the induction mortality was 16% (9). Amongst patients evaluated for a CR (46/56), 48% (22/46) obtained a CR. Although a CR was seen in 100% (3/3), 46% (15/33) and 37% (3/8) of patients with favorable, intermediate and poor-risk cytogenetics respectively there was no statistically significant difference (p=0.22) between groups. A CR was obtained in two additional patients following a second course of FLAG for an overall CR rate of 52% (24/46). Of these 24 patients, 8 (33.3%) received no additional treatment while 16 (66.7%) received consolidative chemotherapy. Of 10 eligible patients, 4 proceeded to an allogeneic stem cell transplant (allo-SCT) including two with preexisting cardiac disease. Of patients not transplanted 50% (10/20) eventually relapsed. There was no difference in relapse rates for those receiving FLAG for age/co-morbidities vs. cardiac disease (60% vs. 40%, p= 0.66) or for patients age The median OS for the 56 patients was 278 days with 1 and 2 year survivals of 44% and 22% respectively. The median OS for patient’s age < 60 was higher than those age ≥ 60 (1102 days vs. 218 days, p=0.009) but there was no difference in the OS between patients treated with FLAG for cardiac disease and those treated for other reasons (305 days vs. 254 days, p=0.202). The median survival of patients with favorable, intermediate and unfavorable risk cytogenetics was 523 days, 311 days and 87 days respectively but this was not statistically significant (p=0.25) likely due to limited patient numbers. Conclusions: The FLAG regimen is a non-anthracycline based regimen that may serve as an alternative to the standard ‘3+7’ induction for AML in older adults or those with significant co-morbidities including preexisting cardiac disease. It is associated with comparable remission rates and overall survival in older patients. In addition, it may allow some patients with preexisting cardiac disease to proceed to allo-SCT. Disclosures No relevant conflicts of interest to declare.

Multiple myeloma (MM) is identified by unique immunoglobulin heavy chain (IgH) variable diversity joining region gene rearrangements, termed clonotypic, and an M protein termed the “clinical” isotype. Transcripts encoding clonotypic pre and postswitch IgH isotypes were identified in MM peripheral blood mononuclear cells (PBMCs), bone marrow (BM), and mobilized blood. For 29 patients, 38 BM, 17 mobilized blood, and 334 sequential PBMC samples were analyzed at diagnosis, before and after transplantation for 2 to 107 months. The clinical clonotypic isotype was readily detectable and persisted throughout treatment. Eighty-two percent of BM and 38% of PBMC samples also expressed nonclinical clonotypic isotypes. Clonotypic immunoglobulin M (IgM) was detectable in 68% of BM and 25% of PBMC samples. Nonclinical clonotypic isotypes were detected in 41% of mobilized blood samples, but clonotypic IgM was detected in only 12%. Patients with persistent clonotypic IgM expression had adverse prognostic features at diagnosis (lower hemoglobin, higher β2-microglobulin) and higher numbers of BM plasma cells compared with patients with infrequent/absent clonotypic IgM. Patients with persistent clonotypic IgM expression had significantly poorer survival than patients with infrequent IgM expression (P

Myeloma is incurable because the malignant stem cell is not eradicated by treatment. Thus, identification of the malignant hierarchy of B lineage cells in myeloma is required to identify potentially generative components and to evaluate their drug resistance properties. BM plasma cells are usually depleted by chemotherapy, but clonotypic B cells survive melphalan/prednisone as well as combination chemotherapy. In vitro, circulating and bone marrow-localized myeloma plasma cells show defective drug export, despite their phenotypic expression of P-glycoprotein, the mdr1 gene product. In contrast to plasma cells, circulating myeloma clonotypic B cells exhibit very efficient drug export. This suggests that circulating clonotypic MM B cells comprise a reservoir of drug resistant disease in myeloma although their stem cell potential remains to be confirmed. The malignant clone in each myeloma patient is defined by a unique IgH VDJ gene rearrangement. Using methods that exclude the possibility that a frequent but non-malignant clone has inadvertently been identified, and after confirming that the sequence identified is expressed by nearly all bone marrow plasma cells, we show that the drug resistant set of myeloma B cells is clonally related to the malignant plasma cells in myeloma. Clonotypic MM B cells survive chemotherapy, persist during clinically defined "minimal residual disease" and remain after autologous transplantation. Thus their malignant status is an important consideration. If malignant, they must be considered in the design of therapy. If non-malignant, they would be expected to have minimal impact on the disease process. A variety of evidence provides strong support for the view that clonotypic drug resistant B cells are malignant and may include the generative compartment of myeloma. The P-gp+ set of clonotypic B cells is extensively DNA aneuploid, an attribute of malignancy. All clonotypic B cells overexpress RHAMM, a novel oncogene involved in malignant spread. Finally, the population of clonotypic B cells lacks intraclonal heterogeneity. Since intraclonal heterogeneity is driven by the response to antigens, its absence in these cells indicates that they are no longer antigen-responsive. Since antigen-independent clonal expansion is characteristic of lymphoid malignancies, these observations provide further proof that clonotypic B cells in myeloma are malignant. Thus, the drug resistance of these cells is highly relevant to understanding why myeloma remains incurable despite the initial chemosensitivity of most bone marrow plasma cells.

A 71-year-old male with severe autoimmune hemolysis with both cold agglutinins and warm antibodies was intolerant of prednisone and cyclophosphamide. Rituximab was given during a 60-day period when he required 41 units of packed cells to maintain hemoglobin above 75 g/l. Two weeks later hemoglobin stabilized at 95 g/l, and further transfusions were not required. A second course of rituximab was given 4 months later for continued hemolysis. A satisfactory hemoglobin was maintained for 9 months from initial treatment, when hemoglobin again fell to 65 g/L. A prompt response to a third course of rituximab was obtained. This is the second patient with both cold agglutinins and warm antibodies with severe hemolytic anemia who has had a prompt response to rituximab. This treatment should be considered when a rapid response is needed or when a patient has failed to respond to more standard therapies.

Summary. We report two patients with Felty's syndrome and chronic skin ulcers treated successfully with recombinant granulocyte colony stimulating factor (GCSF). In both cases granulocytes returned to the normal range within days of starting treatment, and their cutaneous ulcers improved. In one patient granulocytes were maintained at normal levels with a regimen of GCSF 3 μg/kg twice weekly for 14 months.

Circulating monoclonal B cells in peripheral blood from patients with multiple myeloma or with monoclonal gammopathy of undetermined significance (MGUS) have previously been shown to express CD19, CD20, and PCA-1 and are predominantly CD45R0+, characterizing them as very late stage B cells. This work shows that the abnormal B cells are monoclonal as defined by their exclusive expression of either kappa or lambda light chain mRNA, and that the same type of light chain mRNA is expressed in both bone marrow plasma cells and blood B cells. These abnormal tumour-related circulating B cells express high densities of CD11b, a beta 2-integrin, which is expressed in a conformationally active state as defined by reactivity with monoclonal antibody 7E3. Normal peripheral blood B cells which do not bear CD11b acquire a high density after stimulation with pokeweed mitogen (PWM). At day 4 of culture, the expression of CD11b on normal CD19+ B cells was nearly comparable to that of the circulating myeloma late stage B cells. After PWM stimulation of circulating myeloma B cells the expression of CD11b was gradually lost during 4 days of culture, suggesting that its expression is dynamically regulated. Two patients with no phenotypically abnormal B cells in their blood at diagnosis acquired a large subset of CD11b+ B cells 4 weeks after initiation of chemotherapy. In most patients, a subset of the circulating myeloma B cells express a low density of CD5. The proportion of CD19+ B cells in the bone marrow expressing CD11b was much reduced compared with peripheral blood B cells, and CD11b was not detectable on plasma cells in the bone marrow, suggesting a sequential relationship of the B-cell subsets detected in our population of patients, involving gradual loss of CD11b concurrent with the loss of CD19 during B lineage differentiation. These cells appear to represent a continuously differentiating monoclonal B lineage culminating in the CD11b- plasma cell entrenched in the bone marrow. We speculate that the expression of conformationally active CD11b on the abnormal B cells in peripheral blood mononuclear cells of myeloma patients facilitates transendothelial migration of circulating myeloma B cells to the bone marrow.

Background: Philadelphia chromosome negative chronic myeloproliferative disorders (CMPD) are a group of hematopoietic stem cell disorders associated with elevated blood counts, abnormal bone marrow morphology, and often with coagulopathy. The JAK2 617V>F mutation is reported to be present in approximately half of the CMPD classified as essential thrombocythemia (ET). The mutation is currently used in diagnosis. Its relation to prognosis is unclear. Aim: The goal of this study was to determine the prognostic relevance of JAK2 617V>F mutational status in ET patients. Methods: A 12-year retrospective review of laboratory and medical records identified 255 cases of ET. The diagnosis was based on PVSG or WHO criteria. Peripheral blood, bone marrow, cytogenetics, and other laboratory findings at the time of diagnosis were catalogued. Clinical complications before and after diagnosis were documented. For cases where JAK2 617V>F status was unknown, we used InvivoScribe RFLP kit assay utilizing polyacrylamide gel electrophoresis analysis on archived bone marrow or peripheral blood samples (5% analytical sensitivity). The associations were calculated as odds ratio (OR) with 95% confidence interval (CI). Differences in continuous variables were tested using Student’s t-test and Mann-Whitney U test. Chi-square test and Fisher’s Exact test were used to compare differences in proportions. A difference was considered significant if P Results: Complete laboratory and clinical data were available for 227 cases of ET (male:female = 0.6; mean age, 65.9 years; mean follow up, 63.7 ± 2.5 months). 125 (55.1%) patients were heterozygous and 6 (2.6%) were homozygous positive for theJAK2 617V>F mutation and 96 (42.2%) were negative. There was no significant difference in sex, age of onset survival, karyotype, or treatment rate (with hydroxyurea or anagrelide) between JAK2 617V>F positive and negative groups. The presence of mutation at the time of diagnosis correlated with higher hemoglobin (141.8 ± 1.7 vs. 128.0 ± 2.3 g/L, P = Conclusion: Our data supports the reported incidence of JAK2 617V>F mutation in ET (58%). Presence of the JAK2 617V>F mutation in ET patients does not predict survival, gender, age of onset, karyotype, risk of venous thrombosis, or bleeding. The mutation does correlate with a higher risk of arterial thrombosis in our study population. This risk appears to be highest before diagnosis of ET and equalizes after diagnosis between mutation positive and negative patients, possibly reflecting better response to therapy in the former group.

In MM and WM, we identified aberrant HAS1 splice variants that were absent from normal donors (HD) and B-CLL. Here we sequenced multiple subclones from multiple cell subsets to show that aberrant HAS1 splicing results from cryptic splice sites activation. Aberrant splicing defects are the consequences of genetic variations (GVs) detected in the sequence of classical splicing elements as well as within exons and introns. To investigate HAS1 splicing in MM and WM patients, we sequenced the HAS1 gene segments involved in abnormal splicing events. HAS1 from buccal epithelial cells (BEC) represented the host genotype, and hematopoietic progenitors (HP), T, B and plasma cells (PC) as the normal and malignant components of the hematopoietic lineage in MM/WM. 197 GV were found in 16 MM or WM patients, but none in 9B-CLL, MGUS or HD. We found 60 germline (defined as present in BEC and hematopoietic cells) and 137 somatic GV (defined as GV found in HP, T, B and/or PC, but absent from BEC). These somatic GV include 97 tumor-specific GV found in MM and/or WM B and PC and 40 hematopoietic origin GV identified in HP, T, B and PC, but not in BEC. Some GV were recurrent, detected in more than one patient. Recurrent GV (24 in MM and 22 in WM) included both germline and somatic GVs, 6 tumor-specific, 6 hematopoietic and 14 germline origin GV, as well as 20 NCBI-SNPs. The distribution of GV indicated that some of the recurrent germline and somatic GV are restricted to MM, some are restricted to WM and some are shared by both MM and WM. None were found in B-CLL, MGUS or HD. The patterns of germline GV observed in MM and WM suggests that MM and WM patients, but not B-CLL, inherit recurrent germline GV that are necessary but not sufficient for progression to malignancy. Acquisition of recurrent, somatic HAS1 GV in HP further increases the risk of developing MM or WM. Transformation may become inevitable when tumor-specific recurrent GV are acquired. Interestingly, we detected increased homozygosity for the mutated allele of some germline GV in all cell types (PC, B, T, HPs and BECs) from MM and/or WM patients. These GV were detected in 75-90% of subclones analyzed. Mutational analysis of minigene constructs demonstrated a distribution of GV as clusters in the vicinity of HAS1splicing elements, allowing us to classify them as “splicing mutations”. This is supported by an in vitro splicing assay, which confirmed that a combination of germline and somatic GVs leads to aberrant HAS1 splicing (see abstract by Kriangkum et al., ASH 2007). Our study demonstrates that the impact of inherited and acquired GV on HAS1 gene splicing is manifested only in the context of accompanying tumor-specific HAS1 GV, that in combination give rise to the clinically significant aberrant splicing of HAS1. It also indicates that MM and WM are closely related at the genomic level, with the same recurrent somatic mutations independently arising in both diseases. Accumulation of somatically acquired HAS1 mutations in HP, in the context of inherited predispositions to MM and WM may represent a very early stage of pre-malignant development. Similar to leukemias, initiation events that contribute to MM and WM pathogenesis may arise from mutations which first accumulate during the non-malignant or pre-malignant stages of hematopoietic differentiation in progenitor cells.

In multiple myeloma (MM) and Waldenstrom’s macroglobulinemia (WM), we identified three alternatively and/or aberrantly spliced HAS1 transcripts—HAS1Va, HAS1Vb and HAS1Vc. Statistical analysis of samples taken from 172 untreated MM patients showed that expression of HAS1Vb, an intronic splice variant, strongly correlates with poor survival (P=0.005). We investigated the molecular basis of intron retention during HAS1 splicing in MM and WM patients. We speculated that aberrant HAS1 splicing and the associated reduced survival of MM patients, resulted from an accumulation of mutations in aberrantly spliced regions of HAS1. Exons and introns 3 and 4 of the HAS1 gene were sequenced, because they are hotspots for splicing aberrations. Sequencing of HAS1 was performed for a total 11 patients with WM and MM and 2 healthy donors. HAS1 gene templates for sequencing were isolated from a multiple sorted cell subpopulations, including malignant B and plasma cells (PC), non-malignant T cells and buccal epithelial cells (BECs), as well as hematopoietic progenitor cells (HPCs) from mobilized blood of MM patients. We detected sets of inherited and acquired genetic variations in HAS1 that were recurrent within 5–11 of the MM and WM patients analyzed, but absent from healthy donors. We also identified genetic variations that were unique to individual patients. Those HAS1 mutations found in all cell types tested, including BECs and from the hematopoietic cells (B, PC, T and HPCS) were classified as germline mutations. Those mutations found in hematopoietic cells but absent from BECs were classified as hematopoietic origin which acquired during the lifetime of the individual. Mutations identified only in malignant MM and WM B cells and PCs (absent from T cells, HPCs and BECs) were classified as acquired tumor specific mutations. Recurrent HAS1 mutations were found among both inherited and acquired sets of mutations. Some recurrent HAS1 mutations were common to both MM and WM. The high frequency of inherited HAS1 mutations suggests that they confer predisposition for developing MM or WM. Our sequencing analysis suggests that in MM and WM, sequential accumulation of genetic variations occurs as hematopoietic cells differentiate. Our data also suggest that hematopoietic origin mutations are necessary but by no means sufficient to drive HAS1 gene splicing. Effects of hematopoietic origin mutations on HAS1 splicing are manifested in malignant MM cells in context of additional tumor specific mutations, which are acquired by circulating B cells and passed to their plasma cell progeny. This suggests that mutations which lead to aberrant splicing of HAS1 pre-mRNA undergo mutational selection events, and leave a mutational “trace” throughout the hematopoietic cell lineage, including tumor cells. Existence of same mutational events detected in HAS1 gene from MM and WM supports the speculation that the precursors of both diseases may undergo a series of shared genetic events, diverging only when tumor specific mutations accumulate in distinct subsets of B lineage cells. In silico comparison of splicesomal assembly between wild type and mutated HAS1 gene gave a pattern that precisely predicts partial retention of intron and aberrant splicing of the HAS1 gene.

Malignant B lineage cells in Waldenstrom’s macroglobulinemia (WM) express a unique clonotypic VDJ associated with IgM. Studies of WM patients revealed a frequent incidence of biclonal B cells (16%) as defined by the presence of two distinct clonotypic VDJ sequences. This is the first report to estimate the frequency of biclonality in WM. Four WM cases are reported: two with distinct IgM clones (WM1-19 and WM1-09), one with distinct IgM/IgA clones (WM1-18), and one with related but diversified IgM/IgG clones (WM10). In 2 cases (WM1-19 and WM10), the two clonotypic signatures were found to be abundant in bone marrow (BM) but less frequent in blood, reminiscent of monoclonal WM cases. In WM1-19, single cell analysis showed that only one partner VDJ was expressed per cell, excluding the possibility of aberrant biallelic rearrangements. The distribution ratio between the two tumor clones was 2:1, suggestive of their mutual role in the clinical manifestation. In the other 2 cases (WM1-09 and WM1-18), partner clones were shown by CDR3 fragment analysis to be anatomically distinct, with one BM clonotypic signature and one in blood. In these 2 patients, the BM clone was hypermutated (6.2% and 3.8%) while the blood clone was germline or minimally mutated (0% and 1.0%). Partner clones lacked intraclonal diversity and Ig class switching, characteristic of malignant WM clones, suggesting relatively frequent transformation events throughout B lineage differentiation. The biological events leading to the appearance of clones in two different anatomic sites and the clinical implications remain to be understood. CDR3 fragment analysis in the longitudinal studies of WM1-09 and WM1-18 suggested that the repertoire of blood B cells may recover some level of diversity after successive cycles of treatment (WM1-18), while the persistence of the monoclonal peak (WM1-09) likely reflects a tumor that does not respond to treatment. In WM10, biclonal IgM/IgG B cell clones shared common VDJ gene rearrangement. The IgG clone displayed a higher mutation rate than did the IgM clone (9.7% vs. 6.1%). Increased somatic hypermutation in IgG consists mostly of replacement mutations that are clustered within the CDR regions, strongly supporting a contention that the IgG clone has undergone affinity maturation. There are 11 point mutations in the IgM that are not present in the IgG, suggesting that the two clones are distinctly different and belong to different branches of the genealogical tree. These distinct mutational signatures suggest that biclonal IgM/IgG clones are unlikely derived from clonal evolution. Overall, our results suggest that for the four biclonal WM evaluated here, the partner B cell clones appear to have undergone separate transformation events in the development of biclonality. The extent to which each partner clone contributes to disease progression and death, whether separately or in synergy, is as yet unknown.

The hyaluronan synthase 1 (HAS1) gene, which maps to chromosomal location 19 q3.14 undergoes aberrant intronic splicing in malignant B cells from MM and WM patients. We previously detected up-regulation of HAS1 gene in MM and WM, and identified three aberrantly spliced transcripts of this gene, termed HAS1Va, HAS1Vb and HAS1Vc. With a much larger patient cohort, statistical analysis of samples taken from 201 untreated MM patients showed that expression of HAS1Vb strongly correlates with poor survival (P=0.005). Furthermore, for MM patients with lytic bone disease, those patients having both lytic lesions and expression of HAS1Vb had statistically shorter survival than those with lytic lesions but lacking HAS1Vb (p=0.02). Our gene expression analysis at the single cell level demonstrates that 76–97% of individual CD20+ IgM+ WM cells obtained from BM aspirates and PBMC expressed HAS1Va or HAS1Vb variants. Exon skipping and partial intron retention in the HAS1 gene, detected in WM and MM cells, can result from activation of cryptic splicing elements. In turn, activation of cryptic splicing elements can be promoted by mutations, including SNPs, which serve as frequent genetic markers along the chromosome. We analyzed the frequency of the HAS1 833 A/G SNP located upstream of alternatively spliced exon 4, on exon 3. Bioinformatic analysis demonstrated that HAS1 833 A/G SNP overlaps with an exonic splicing enhancer motif of HAS1 and in the mutated allele this exonic splicing enhancer is abrogated. The genotype of G/G and A/G was found respectively in 90% and 10% of 60 WM cases, 85% and 15% of 117 MM cases and 40% and 60% of 90 cancer-free cases. Our results demonstrate that the genotype G/G is significantly more frequent in WM and MM patients than in cancer free controls (p=0.0001for WM and p= 0.00003 MM). The genotype A/A was not detected in any of the 267 individuals tested to date, and is presumed lethal. Further, in MM and WM B cells, we identified recurrent mutations on HAS1 intron 4 that include alterations of a key splicing element, polypyrimidine tract that creates and/or activates a new splice site in precisely the position required for the splicing events that create HAS1Vb. Bioinformatic analysis indicates that these recurrent genomic variations in intron 4 alter splisosome assembly, leading to aberrant splicing of HAS1 and the predicted impact on malignant disease and patient survival. We speculate that SNPs in HAS1 provide the predisposing elements for MM and WM, and additional mutations within the genome of emerging malignant B cells are required for progression to malignant disease. Thus, aberrant splicing of the HAS1 gene in MM and MW patients may results from the presence of polymorphisms and recurrent mutations in the HAS1 gene. Our genotyping analysis suggests that SNPs and mutations in the HAS1 gene may contribute to oncogenic events in WM or MM.

Clonotypic B cells of Waldenstrom Macroglobulinemia (WM) are characterized as CD20+138− sIgM+sIgD+ cells that are not restricted to CD27 memory marker expression. Clonotypic VDJ sequences show VH3/JH4 gene bias, exhibit intraclonal homogeneity and do not undergo class switch recombination (CSR). To better understand the failure of CSR in WM, switch (S) region analysis, activation induced cytidine deaminase (AID) expression and CD40L/IL-4 activated clonal CSR were studied in comparison to IgM monogammopathy of undetermined significance (MGUS). Large internal deletions of Sμ that could hinder CSR were determined by analysis of CDR2/Sμ fragments amplified from genomic DNA of clonotypic WM or MGUS B cells. Deletions were found in only 1/12 WM and 0/4 IgM MGUS, suggesting that large deletions of Sμ are not common in WM or IgM MGUS. Sequence analysis of Sμ upstream regions revealed striking differences between WM and IgM MGUS. By comparing the 1.6 kb sequences upstream of Sμ tandem repeats, we found that WM clones exhibit less mutation (0–2 bp/1.6 kb or 0.57x10− 3 bp, n=11) than IgM MGUS (0–7 bp/1.6 kb or 2.5x10− 3 bp, n=4, p=0.001). The MGUS clones containing frequently mutated switch region also exhibited intraclonal diversity of IgM VDJ. These differences exclude most IgM MGUS from a precursor relationship with WM and may help to identify those less frequent IgM MGUS that are at risk of progression to WM. Only 2/17 WM and 0/5 IgM MGUS constitutively expressed AID but it can be induced by CD40L/IL-4 activation as shown in 4/4 WM and 3/3 IgM MGUS. Single cell analysis showed that both clonotypic and non-clonotypic B cells accounted for AID induction. Splice variants are colocalized with full-length transcripts in some individual cells from WM, IgM MGUS and normal donors. Thus, AID splice variants are generally present in activated B cells. Using enhanced PCR amplification protocols, clonotypic CDR2/Cγ transcripts were detectable post-stimulation in 2/4 WM and 2/3 IgM MGUS, suggesting that WM and IgM MGUS B cells are capable of CSR. For 2 WM activated in vitro, we detected clonal IgG transcripts, having variable-sized CDR2/Sγ 1 fragments and diversity of clonotypic Sμ/Sγ junctions. This indicates that clonotypic CSR occurred multiple times within the WM tumor population. Although this implies that persistent CSR occurs and although clonotypic IgM B cells were frequent (16%) in cultures, clonotypic IgG producing WM B cells were very rare, with a frequency of only 0.01%. Clonotypic IgG exhibited intraclonal homogeneity of the clonotypic VDJ, with a sequence identical to that of the clonotypic IgM VDJ, suggesting that clonotypic CSR is a post-transformation event. Clonotypic IgG may arise through CSR occurring in vitro, through clonal expansion of pre-existing post-switch WM B cells or both. Overall, our studies show that initial B cell activation as determined by AID induction is normal and that intact CSR machinery is functional in WM, although clonotypic CSR occurs at very low frequency. For the majority of WM B cells, CSR does not occur even when stimulated in vitro, suggesting that the WM cell is constitutively unable to undergo CSR or being prevented from CSR. Further, since mutations in upstream Sμ are found in most IgM MGUS, making them ineligible as WM progenitors, switch sequence analysis may help to identify those IgM MGUS at risk of progression.

Translocations involving the IgH locus are common genetic events in multiple myeloma (MM). A number of recurrent IgH translocations exist with t(11;14)(q13;q32) and t(4;14)(p16;q32) being the most common. These translocations predict for differential clinical outcomes, good versus poor, respectively. We have shown that ~70% of t(4;14) POS patients express the initially proposed target gene FGFR3. However, the t(4;14)POS/FGFR3NEG group of patients still fare poorly (P=0.01). Therefore, either the transformation event associated with t(4;14) is multifactorial or independent of FGFR3. The loss of FGFR3 expression is associated with the loss of der(14). However, der(4) is detectable in all t(4;14)POS patients at diagnosis and relapse, suggesting that it is biologically and clinically relevant. The der(4) chromosome is thought to result in the overexpression of MMSET. The genomic breakpoints associated with t(4;14) occur in the 5′ end of the MMSET locus. In 70% of patients (MB4-1), the breakpoints maintain the full length open reading frame of MMSET. In the remaining 30% (MB4-2 & MB4-3), the breakpoints occur downstream of the proper translation initiation site. Two principle transcripts originate from the MMSET gene. The first transcript initiates in the beginning of the MMSET locus and, as a result of alternative splicing of exon 12, produces either MMSET I or MMSET II. The second transcript initiates upstream of exon 10 and uses an alternative translation initiation site to produces RE-IIBP. MMSET I and II transcripts, produced by each breakpoint variant, and the RE-IIBP transcript, produced in all patients irrespective of breakpoint type, were cloned. Transcripts were C-terminally tagged with GFP and transiently transfected into HeLa cells. Anti-GFP immunoblots showed that all transcripts produced a protein product, even the MB4-2 and MB4-3 variants that utilize alternative translation initiation sites in exon 4 and 6, respectively. The wildtype/MB4-1 MMSET I and II constructs localized to the nucleus and were excluded from nucleoli. MMSET II is almost exclusively associated with chromatin while MMSET I localized diffusely. RE-IIBP localized primarily in cytoplasmic foci and to nucleoli. Unlike the full length MMSET proteins, the MB4-2/MB4-3 constructs localized to the nucleus but also localized in nucleoli. To determine if the N-terminus regulates the nuclear localization pattern, we cloned the N-terminal portion of MMSET, which is lost in the MB4-2 transcripts. As this construct localized to the nucleus and was excluded from nucleoli, therefore a domain required for the proper localization of MMSET is lost in the MB4-2/MB4-3 variants. Kinetic analysis of MMSET variants localized to the nucleoplasm shows that the association of MMSET II with chromatin is very stable, t1/2 130 sec, while the type II MB4-2 and MB4-3 breakpoint variants have reduced kinetics, t1/2 19 and 12 sec, respectively, suggesting a decreased stability of association. The reduction in kinetics is also seen in the type I variants. We verified the overexpression of RE-IIBP by quantitative RT-PCR on a panel of purified plasma cells and unpurified BMMC. RE-IIBP was overexpressed in t(4;14)POS patients, P=0.0009 and P=0.00006, respectively, making it the only overexpressed protein without altered function in all t(4;14)POS patients irrespective of FGFR3 expression or breakpoint type. Therefore, RE-IIBP may be of central importance to the poor outcome of t(4;14)POS MM patients.

The hyaluronan synthase 1 gene (HAS1), which maps to chromosome location 19q13.4 encodes a plasma membrane protein, which synthesizes hyaluronan (HA), an extracellular matrix molecule. Previously, in WM patients we detected up-regulation of HAS1 transcripts and identified aberrant splice variants of this gene, termed HAS1Va, Vb, and Vc. In patients with multiple myeloma, expression of HAS1Vb either alone or in combination with HAS1 and other variants strongly correlates with poor survival (P=0.001). Our gene expression analysis of the HAS1 family members demonstrated that 76–97% of individual CD20+ IgM+ WM cells obtained from BM aspirates and from blood (PBMC) express HAS1Va or HAS1Vb aberrant splice variants, often in the absence of full length HAS1 transcripts. Aberrant splicing of HAS1 is the result of activation of cryptic splice sites, which lead to exon skipping and/or intron retention. In turn, activation of cryptic donor and acceptor splice sites of the gene can be promoted by the mutations occurring upstream of these sites and/or at the branch point of slicing. We measured the frequency of a known polymorphism in the HAS1 gene of 16 BM and 30 PB samples obtained from WM patients, in comparison with PBMC samples from 33 healthy donors. Our results indicate that in healthy individuals, the frequency of the two alleles each reached 50% perhaps reflecting stabilizing selection. The majority of healthy donors (61%) are heterozygous for the HAS1 gene polymorphism. In contrast, 92% of analyzed WM patients are homozygous for this same polymorphism. An expression analysis of HAS1 and variants in BM cells and PBMC obtained from the same group of WM patients demonstrated that only those patients who were homozygous for the HAS1 polymorphism express HAS1 and/or its variants. The few WM patients who are heterozygous for this polymorphism have no detectable expression of aberrantly spliced HAS1 variants or full length of HAS1, a phenotype identical to that of healthy donors. Thus, our observations so far suggest that polymorphisms in HAS1 may contribute to aberrations such as exon skipping and/or activation of a new cryptic splice site leading to aberrant splicing of HAS. Based on the results obtained thus far, we speculate that individuals who are homozygous for HAS1 polymorphism(s) are at enhanced risk of developing WM due to a predisposition towards aberrant HAS1 splicing and expression of HAS1 variants, with predicted oncogenic consequences. However, the study of a much larger number of patients and healthy donors is needed to confirm these speculations and to evaluate the prognostic significance of these findings.

Clonotypic B cells of Waldenstrom’s macroglobulinemia (WM) are characterized as CD20+IgM+IgD+ cells that are usually somatically mutated in IgH VDJ but for some patients, the clonotypic IgH VDJ is germline (unmutated).For both mutated and unmutated clones, WM lack ongoing somatic hypermutation (SHM) and class switch recombination (CSR). This may be due to abnormalities in switching and/or mutator genes. To understand the nature of unswitched tumor B cells, uracil DNA glycosylase (UDG) and activation-induced cytidine deaminase (AID), the two essential elements for CSR, were analysed in WM. Analysis of 12 WM clones characterized by somatic hypermutation showed that the mutation profile of VH genes had normal transition/transversion ratios at C or G, and thus did not suggest UDG abnormalities. Expression of AID was determined by single stage RT-PCR. Out of 14 patients studied (2 unmutated and 12 mutated VH clones), two of them (WM1-01 and WM1-08,with mutation rates of 0% and 6.2% respectively) gave positive bands. In WM1-01, despite having a germline IgH VDJ, AID is consistently expressed in two bone marrow samples collected three years apart and from which the identical unmutated clonotypic VDJ sequence was isolated. Full-length (FL) AID transcripts of WM have a conserved sequence, thus ruling out the possibility of functional defects due to point mutation. In addition, detection of AID in an unmutated VH clone suggested that lack of SHM does not result from an inability to produce AID. In addition to FL transcripts, three other splice variants were identified in both patients. Single cell analysis indicated that only a small compartment (10% or less), not all, of clonotypic B cells expressed AID, and multiple isoforms may be detectable in individual cells. Whether these splice variants that contain truncated C-terminal ends play a role in the regulation of CSR in WM remains to be investigated. Splice variants, nevertheless, may not characterize tumor B cells since up to 10% of AID-expressing normal activated B cells (n=3) also carried them. In vitro activation of clonotypic WM B cells by CD40L and IL4, using conditions that induced CSR in normal B cells, did not yield detectable class switching in WM B cells. In cultures of B cells from WM, the number of non-clonal B cells increased but the clonotypic B cells did not appear to expand, as indicated by the reduction of clonotypic IgM transcript at 5-days of culture. Thus, as well as failing to undergo somatic mutation or class switching, WM tumor B cells appear unresponsive to CD40L+IL4. They may be fundamentally unresponsive to signals for class switching and their clonal expansion may depend upon alternate signaling pathways.

Hyaluronan synthases, plasma membrane proteins encoded by the HAS genes, synthesize different sizes of hyaluronan (HA), an extracellular matrix molecule which is biologically active in malignant spread and signaling. HA is also a ligand for RHAMM, a receptor, shown by our laboratory to regulate mitotic events. We demonstrated that abnormal expression of RHAMM in model systems results in mitotic abnormalities that may lead to chromosomal missegregation in multiple myeloma (MM). In MM patients we detected overexpression of HAS1 transcripts and we have identified three aberrantly spliced variants of HAS1 designated as HAS1Va, Vb, and Vc. The statistical analysis of samples from 58 MM patients taken at the time of diagnosis showed that expression of HAS1Vb either alone or in combination with HAS1 and variants in MM cells strongly correlates with poor survival (P=0.001). This expression analysis of HAS1 and variants in MM patients suggests that, particularly HAS1Vb may contribute to early myelomagenesis since these transcripts are detected individually or in combination with other HAS1 variants in MM and MGUS patients at the time of diagnosis. Longitudinal analysis of HAS1 and its variants in 18 unselected MM patients showed expression of the family of HAS1 transcripts in a majority of these patients at diagnosis (65% of patients) and relapse (71.4% of patients). All three HAS1 variants are truncated as the result of exon skipping and/or intron retention. In general, partial retention of introns appears to be characteristic of the genes associated with a malignant phenotype. Alignment and protein motif screening analysis showed that all three variants of HAS1 retain the motif, which is responsible for the synthesis of HA. In silico analysis demonstrated that HAS1 variants are able to fold appropriately. Protein expression of HAS1 variants was detected by western blotting using lysates from MM cell lines. Enzymatic activity of family of HAS1 proteins was verified by a particle exclusion assay (PEA) and HA staining. Using these methods we detect HA matrix and intracellular HA around and in MM cells. Based on PEA analysis, both HAS1Va and HAS1Vb appear to synthesize extracellular HA. Synthesis of extracellular HA by MM cells may impact disease biology by contributing to drug resistance and could accommodate spread of MM cells by facilitating motility and malignant spread. Furthermore, HAS1Vb, the only variant with strong clinical impact, also appears to be the only splice variant that produces intracellular HA, a form of HA that may modulate RHAMM associations with the mitotic spindle. The HA binding motif of RHAMM overlaps with its centrosomal targeting domain. Strong perinuclear localization of intracellular HA, which branches out from the perinuclear compartment toward the MM cell plasma membrane suggests that these molecules may also contribute to the maintenance of cellular architecture by malignant MM cells. We speculate that at least part of the strong clinical impact of aberrant HAS1Vb intronic splicing reflects the predicted ability of intracellular HA synthesized by HAS1Vb to modulate the function of RHAMM by inhibiting centrosomal targeting, thereby promoting aberrant mitosis. If this working hypothesis is correct, HAS1 and its variants, particularly HAS1Vb, in concert with RHAMM may be key contributors to chromosomal instability in MM. Funded by CIHR and by CA80963 from NCI.

The objectives of this study were firstly, to compare the immunophenotype of patients with monoclonal gammopathy of undetermined significance (MGUS) with that of patients with newly diagnosed, untreated multiple myeloma (Unt. MM). Our second objective was to determine which variables might distinguish patients with MGUS and early MM. The CD4/CD8 ratio in both patient groups differed significantly from normal as a result of a decrease in the proportion of CD4+ cells. Similarly, surface immunoglobulin-positive (Ig+) B cells were significantly reduced in both groups. Also, some impairment of Ig secretion was observed. An in vitro specificity study of B cells showed an enriched proportion of B cells specific for tetanus toxoid (which may be indicative of enrichment for memory B cells) in both MGUS and Unt. MM patients. Further to this, in MM patients but not in MGUS patients, there was an enriched proportion of B cells specific for determinants on the F(ab')2 fragment of Ig. This suggests an anomalous auto-immune reactivity to polyclonal Ig molecules. In one of the two patients studied, who progressed from MGUS to MM, disease progression was accompanied by an increase in this anti-Ig reactivity. In both patients there was a decrease in CD4/CD8 ratio.

Patients with multiple myeloma suffer from often profound immunodeficiency that seriously compromises both longevity and quality of life. The cellular basis for the immunodeficiency is unknown and the mechanism(s) giving rise to and possibly maintaining it is also unknown. In this review, evidence defining cellular defects in the nonmalignant B and T peripheral blood lymphocyte pool is summarized and discussed in terms of possible mechanisms that could give rise to the abberrant immune phenotype characteristic of many patients. The abnormalities we have defined include a deficiency of mature B lymphocytes, presence of often large numbers of pre-B cells in the blood, arrested differentiation of B cells into immunoglobulin (lg)-secreting cells, and abnormal progenitorlike T cells in blood. The specificity repertoire of the remaining B lymphocyte population is heavily skewed toward recognition of idiotypic and shared epitopes on the variable region of Ig, perhaps reflecting immune reaction with the monoclonal myeloma Ig. This may begin as a response to tumor antigen that gradually progresses to autoimmunity. A second subset of B cells present at abnormally high frequency in myeloma patients is that of antigen-experienced memory B cells, which probably encountered antigen prior to the events leading to frank myeloma. In this instance, the high frequency reflects a decrease in aggregate numbers of B cells, although it seems likely that expansion of memory clones also occurs. This is exemplified by the set of memory B cells specific for tetanus toxoid, which are present at normal number but highly enriched frequency in myeloma PBL. Both the antitumor B cells (anti-idiotype, and anti-Ig) and the memory cells specific for environmental pathogens appear to be arrested in their differentiation to Ig-secretors as evidenced by the lack of serum antibody in patients. The above observations are interpreted in terms of the hypothesis that immunoregulatory events triggered by the monoclonal myeloma Ig establish and maintain the immunodeficiency. We speculate that autoimmune suppressor T cells specific for conserved determinants of Ig prevent pre-B cell differentiation to slg + B cells, and B cell terminal differentiation to Ig-secretors. If correct, this analysis could lead to therapeutic approaches for the reversal of the immunodeficiency and perhaps some degree of control over the malignant growth.

Although multiple myeloma is a disease of plasma cells, abnormalities have been detected in both B and T lymphocytes in peripheral blood. Although multiple myeloma patients are deficient in surface Ig (sIg)- positive B lymphocytes, analysis of lymphocytes present in blood indicates an abnormally large pool of circulating pre-B cells. These pre-B cells express BA-1, do not bear sIg, and contain cytoplasmic mu chains. High numbers of pre-B cells occur in 88% of individuals with frank myeloma and in 44% of individuals with monoclonal gammopathy of undetermined significance. Pre-B cells bearing BA-1 differ between patients in their expression of HLA-DR and receptors for peanut agglutinin (PNA). Those pre-B cells in myeloma patients are either BA- 1+ PNA- HLA-DR+ (54% of patients) or BA-1+ PNA+ HLA-DR- (30% of patients), or have a mixture of phenotypes (14% of patients). Pre-B cells of the PNA- phenotype are almost always HLA-DR+, and PNA+ pre-B cells are HLA-DR-. Within the same patient, the pre-B cell population varies by both quantitative and qualitative definitions. The number of pre-B cells may increase 460-fold and temporal shifts of surface phenotype from BA-1+ PNA- to BA-1+ PNA+ or vice versa have been detected. These observations indicate an abnormality in the B lymphocyte differentiation pathway leading to pre-B cells in the periphery that vary in number and cell surface phenotype, and that are unable to express sIg.

The characteristics of T and B lymphocyte profile and B lymphocyte specificity repertoire were compared in patients with Waldenstrom's macroglobulinemia (WM), IgM monoclonal gammopathy of undetermined significance (IgM MGUS), multiple myeloma (MM), and age-matched normal subjects. Patients with MM had both significantly reduced frequency and number of sIg+ (surface Ig) B cells, whereas patients with WM and IgM MGUS had a reduced frequency but normal numbers of sIg+ B cells in circulation as detected in a capping assay. WM was distinguished by the large numbers of cells in the peripheral blood lymphocyte (PBL) pool that expressed CD9 (BA-2) and CD24 (BA-1) and were monoclonal, based on light chain analysis using flow cytometry. The profile of T lineage cells showed that the ratio of CD4:CD8 was significantly reduced in both MM and WM due to a reduction in the CD4 set. The CD4+ cells were qualitatively abnormal as well, with an enriched proportion of the 4B4+ (CDw29) subset and decreased proportion of the Lp220+ (CD45R) subset. This appeared to be an effect of the disease process on the relatively immature Lp220+ set. From clonal analysis, those patients with WM or IgM MGUS (unlike MM patients) did not exhibit enhanced reactivity with auto-Ig determinants, and most WM patients (7/8) and half of the IgM MGUS patients (3/6) did not have enriched proportions of B cells reactive to tetanus toxoid (TT). The TT-specific B cells in both WM and IgM MGUS, in contrast to MM, appeared fully functional in secretion of anti-TT IgM in vivo. We speculate that the more severe immunodeficiency in MM may be controlled or exacerbated by the presence of an anti-Ig network. The absence of this network in WM allows a relatively more effective immune response, but the immunodeficiency that is observed in these patients involves some abnormality in normal lymphocyte differentiation (is also present in MM).

Under conditions of low shear and in the absence of laminar flow the addition of acetylsalicylic acid (ASA), but not of sodium salicylate, to human platelet-rich plasma (PRP) in vitro significantly inhibited platelet adherence to collagen (p < 0.001). Inhibition was of similar degree (17%) at ASA concentrations of 10 and 1,000 μM, but was less (10% inhibition) in PRP with erythrocytes added to 40% hematocrit. The ingestion of 600 mg ASA had negligible effect on platelet adherence in whole blood or in PRP. There was no correlation between the effects of ASA on adherence and on platelet aggregation in vitro or ex vivo. It is concluded that the effect of ASA on platelet adherence is unlikely to be important in vivo, except perhaps in vascular sites where flow is non-laminar and where shear rates and/or the physical forces on platelets are low.

The specificity repertoire of B lymphocytes from 14 multiple myeloma patients has been studied using the technique of Epstein-Barr virus (EBV) transformation of peripheral blood lymphocytes (PBL) coupled with clonal analysis by limiting dilution. We find that up to 100% of the B cells from myeloma patients undergoing EBV transformation secrete IgM specific for determinants on the F(ab')2 region of autologous and/or heterologous monoclonal immunoglobulin. In normal individuals 0.02-0.73% of the transformed B cells secrete IgM specific for F(ab')2 determinants. Two patients with monoclonal gammopathy of undetermined significance had only a weak reactivity to F(ab')2 fragments. The number of anti-F(ab')2 B cells was up to 145-fold greater in patients than in normal donors. The majority of antibodies from patient clones recognized determinants shared among 3-12 different F(ab')2 fragments, whereas those originating from normal donor B cells saw determinants expressed on only one or two of the panel of test F(ab')2 fragments. There was a preference for autologous M components and a high proportion of antiidiotypic reactivity in five of eight patients so analyzed. We speculate that these findings indicate the existence of an anti-F(ab')2 immunoregulatory network mediating patient immunodeficiency network mediating patient immunodeficiency, thereby creating an abnormality that may enable the progression of multiple myeloma.

Peripheral blood lymphocytes (PBLs) from multiple myeloma patients are defective in both proportion and absolute numbers of OKT4+ cells and have a normal proportion but reduced absolute number of OKT8+ cells. To assess the functional capabilities of the T cells in myeloma patients, we cloned the T cells in PBLs using limiting dilution conditions in which 100% of OKT4+ and OKT8+ T cells in normal PBLs are able to form a clone. In contrast, the OKT8+ cells from PBLs of five of seven multiple myeloma patients were severely compromised in their clonogenic potential; only 7% to 25% of OKT8+ T cells appeared to give rise to a clone. Clonogenic potential of the OKT4+ cells in patients was more nearly normal. Analysis of two multiple myeloma patients with abnormally low numbers of T cells in PBLs revealed the existence of abnormalities in the progenitors of T cell clones. In both patients, two to three times as many T cell clones were observed as would have been expected based on the number of PBLs cultured at limiting dilution, indicating that OKT4′8- cells in PBLs are capable of giving rise to OKT4+ and, at lower frequency, to OKT8+ clonal progeny in vitro. We conclude that purely quantitative assessment of T cell subsets should be interpreted with caution, since proportionately normal numbers of OKT8+ cells in patient PBLs are seriously compromised in their ability to give rise to clonal progeny in vitro, and since there appears to be a OKT4′8- population of T cells in PBLs that are committed to become OKT4+ or OKT8+ T cells, but are unable to do so in vivo.

Patients with multiple myeloma are generally immunodeficient, with pronounced depression in primary antibody responses. We have attempted to delineate the reasons for the humoral immunodeficiency by analyzing the specificity repertoire of the surface immunoglobulin (Ig)-positive B cells in patients with multiple myeloma or monoclonal gammopathy of undetermined significance (MGUS), in comparison with normal donors. B lymphocytes from 26 patients with multiple myeloma, 12 patients with MGUS, and 8 normal donors were transformed with Epstein-Barr virus (EBV) and cultured at limiting dilution for clonal analysis. The Ig secreted by each clone was analyzed for class and anti-tetanus toxoid (TT) specificity to determine the frequencies of IgM, IgG, anti-TT IgM, and anti-TT IgG antibody-secreting clones. Our objective was to establish whether the inability to mount humoral responses to common environmental pathogens was due to a lack of specific B cells or to inhibition of B-cell function. Our results indicate that the quantitative B-cell deficiency in patients was due to a nonrandom loss of selected sets of B cells. Although most patients had a reduced aggregate number of B cells, the number of TT-specific B cells was normal. There was, on average, a threefold increase in the proportion of the B-cell specificity repertoire devoted to recognition of TT. Forty-four percent of the patients with MGUS were also affected. In addition, the TT-specific B cells in multiple myeloma patients were severely compromised in their ability to secrete antibody or to differentiate to antibody-secreting cells in vivo. This arrest in differentiation appears to be extrinsic to the B cells, as they were fully able to secrete anti-TT antibody after transformation and culture in vitro. We postulate the existence of an autoimmune inhibitory network mediating the arrest in B-cell differentiation and the humoral immune deficiency.

The phenotypic distribution of T-lymphocyte subsets in peripheral blood from multiple myeloma (MM) patients shows a reduced proportion of CD4+ cells and a normal proportion of CD8+ cells. The decrease in CD4+ cells could be due to a random process, with all types of CD4+ cells being equally affected, or it could reflect a nonrandom process with selected subsets preferentially reduced. In order to distinguish between these possibilities, double immunofluorescence analysis was performed on blood samples from patients with MM, patients with monoclonal gammopathy of unknown significance (MGUS), and age-matched normal donors, using monoclonal anti-CD4 or anti-CD8 paired with antibodies to the common leukocyte marker Lp220 (CD45R) or 4B4 (CDw29). Normal peripheral blood lymphocytes (PBL) include two phenotypically and functionally distinct CD4+-cell subsets, identified as CD4+ Lp220+ 4B4- and CD4+ Lp220-4B4+, whereas the majority of CD8+ cells expresses Lp220 (70-85%). MM patients had a highly significant selective reduction of the CD4+ Lp220+ subset compared with normal controls (P less than 0.001). Although the percentage of CD4+ Lp220- cells was also reduced in some MM patients relative to normal donors, most of MM patients had an elevated Lp220-/Lp220+ ratio of CD4+ cells (P less than 0.001). The proportion of the two CD8+ subsets was also markedly abnormal. In the set of patients studied the abnormalities within the CD4+ and CD8+ lymphocytes were exclusive to patients with MM since patients with MGUS had normal proportion of CD4+ and CD8+ subsets.

Thrombotic thrombocytopenic purpura (TTP) is a disorder of unknown etiology. An immunologic basis has been suggested, although proof is lacking. The immunologic, hematologic, and autopsy findings in a case of TTP occurring 6 wk postpartum are described. Immunofluorescent studies revealed the presence of IgM and complement, as well as fibrin in the vicinity of the endothelium and in thrombi in small blood vessels in multiple organs. These findings suggest an active immunologic process in this case. While TTP is probably of diverse etiology, confirmation of these findings in further cases would provide a rational basis for the use of immunosuppressive therapy.

We have demonstrated a transition in the expression of CD45 isoforms, from the expression of the high molecular weight CD45R to the low molecular weight CD45 p180 isoform on normal and on monoclonal (possibly malignant) B cells undergoing differentiation into plasma cells. The differentiation into plasma cells was shown by the loss of CD20 and CD21 surface antigens, a reduced expression, but in our system not a complete loss, of CD19, and the expression of the plasma cell marker PCA-1. We used three-color immunofluorescence to demonstrate the shift from CD45R to CD45 p180 on CD19+CD20-CD21- cells in cultures of normal cells stimulated by pokeweed mitogen (PWM). Furthermore, tissue sections of extramedullary plasmacytomas, where plasma cells were defined by morphology and expression of cytoplasmic Ig, showed a complete loss of CD45R and CD45 p180 antigens, although the cells retained expression of CD45 common determinants. Finally, we have analysed PBMC from patients with Waldenstrom's macroglobulinemia (WM) at various stages of disease, and demonstrated that the monoclonal B cell subset present in their peripheral blood is heterogeneous in the expression of CD45 isoforms, including cells bearing only CD45R, those with a transitional CD45R+CD45 p180+ phenotype, and those expressing only CD45 p180. Upon stimulation in vitro these cells show greatly increased expression of CD45 p180. The differential expression of CD45 isoforms within a clonal B cell subset in the blood of these patients suggests that the monoclonal B cells in WM represent a continuously differentiating lineage of CD45R+ mature B cells giving rise to CD45 p180+ pre-plasma cells.(ABSTRACT TRUNCATED AT 250 WORDS)