Circulating clonal cells in multiple myeloma do not express CD34 mRNA, as measured by single-cell and real-time RT-PCR assays

Normal myeloid progenitor cell subset-associated gene signatures for acute myeloid leukaemia subtyping with prognostic impact

Acute myeloid leukaemia (AML) is characterised by phenotypic heterogeneity, which we hypothesise is a consequence of deregulated differentiation with transcriptional reminiscence of the normal compartment or cell-of-origin. Here, we propose a classification system based on normal myeloid progenitor cell subset-associated gene signatures (MAGS) for individual assignments of AML subtypes. We generated a MAGS classifier including the progenitor compartments CD34⁺/CD38^- for haematopoietic stem cells (HSCs), CD34⁺/CD38⁺/CD45RA^- for megakaryocyte-erythroid progenitors (MEPs), and CD34⁺/CD38⁺/CD45RA⁺ for granulocytic-monocytic progenitors (GMPs) using regularised multinomial regression with three discrete outcomes and an elastic net penalty. The regularisation parameters were chosen by cross-validation, and MAGS assignment accuracy was validated in an independent data set (N = 38; accuracy = 0.79) of sorted normal myeloid subpopulations. The prognostic value of MAGS assignment was studied in two clinical cohorts (TCGA: N = 171; GSE6891: N = 520) and had a significant prognostic impact. Furthermore, multivariate Cox regression analysis using the MAGS subtype, FAB subtype, cytogenetics, molecular genetics, and age as explanatory variables showed independent prognostic value. Molecular characterisation of subtypes by differential gene expression analysis, gene set enrichment analysis, and mutation patterns indicated reduced proliferation and overrepresentation of RUNX1 and IDH2 mutations in the HSC subtype; increased proliferation and overrepresentation of CEBPA mutations in the MEP subtype; and innate immune activation and overrepresentation of WT1 mutations in the GMP subtype. We present a differentiation-dependent classification system for AML subtypes with distinct pathogenetic and prognostic importance that can help identify candidates poorly responding to combination chemotherapy and potentially guide alternative treatments.

Evaluation of in vitro effects of various targeted drugs on plasma cells and putative neoplastic stem cells in patients with multiple myeloma

Multiple myeloma (MM) is a malignancy characterized by monoclonal paraproteinemia and tissue plasmocytosis. In advanced MM cytopenia and osteopathy may occur. Although several effective treatment strategies have been developed in recent years, there is still a need to identify new drug targets and to develop more effective therapies for patients with advanced MM. We examined the effects of 15 targeted drugs on growth and survival of primary MM cells and 5 MM cell lines (MM.1S, NCI-H929, OPM-2, RPMI-8226, U-266). The PI3-kinase blocker BEZ235, the pan-BCL-2 inhibitor obatoclax, the Hsp90-targeting drug 17AAG, and the Polo-like kinase-1 inhibitor BI2536, were found to exert major growth-inhibitory effects in all 5 MM cell lines tested. Moreover, these drugs suppressed the in vitro proliferation of primary bone marrow-derived MM cells and induced apoptosis at pharmacologic drug concentrations. Apoptosis-inducing effects were not only seen in the bulk of MM cells but also in MM stem cell-containing CD138⁻/CD20⁺/CD27⁺ memory B-cell fractions. Synergistic growth-inhibitory effects were observed in MM cell lines using various drug combinations, including 17AAG+BI2536 in MM.1S, OPM-2, RPMI-8226, and U-266 cells, 17AAG+BEZ235 in MM.1S, OPM-2, RPMI-8226, and U-266 cells, 17AAG+obatoclax in MM.1S, NCI-H929, OPM-2, and RPMI-8226 cells, BI2536+BEZ235 in MM.1S, NCI-H929, OPM-2, and RPMI-8226 cells, BI2536+obatoclax in MM.1S, OPM-2 and RPMI-8226 cells, and BEZ235+obatoclax in MM.1S and RPMI-8226 cells. Together, our data show that various targeted drugs induce profound and often synergistic anti-neoplastic effects in MM cells which may have clinical implications and may contribute to the development of novel treatment strategies in advanced MM.

Clinical drug resistance linked to interconvertible phenotypic and functional states of tumor-propagating cells in multiple myeloma

The phenotype and function of cells enriched in tumor-propagating activity and their relationship to the phenotypic architecture in multiple myeloma (MM) are controversial. Here, in a cohort of 30 patients, we show that MM composes 4 hierarchically organized, clonally related subpopulations, which, although phenotypically distinct, share the same oncogenic chromosomal abnormalities as well as immunoglobulin heavy chain complementarity region 3 area sequence. Assessed in xenograft assays, myeloma-propagating activity is the exclusive property of a population characterized by its ability for bidirectional transition between the dominant CD19(-)CD138(+) plasma cell (PC) and a low frequency CD19(-)CD138(-) subpopulation (termed Pre-PC); in addition, Pre-PCs are more quiescent and unlike PCs, are primarily localized at extramedullary sites. As shown by gene expression profiling, compared with PCs, Pre-PCs are enriched in epigenetic regulators, suggesting that epigenetic plasticity underpins the phenotypic diversification of myeloma-propagating cells. Prospective assessment in paired, pretreatment, and posttreatment bone marrow samples shows that Pre-PCs are up to 300-fold more drug-resistant than PCs. Thus, clinical drug resistance in MM is linked to reversible, bidirectional phenotypic transition of myeloma-propagating cells. These novel biologic insights have important clinical implications in relation to assessment of minimal residual disease and development of alternative therapeutic strategies in MM.

Stemness of B-cell progenitors in multiple myeloma bone marrow

PURPOSE

In myeloma, B cells and plasma cells show a clonal relationship. Clonotypic B cells may represent a tumor-initiating compartment or cancer stem cell responsible for minimal residual disease in myeloma.

EXPERIMENTAL DESIGN

We report a study of 58 patients with myeloma at time of diagnosis or relapse. B cells in bone marrow were evaluated by multicolor flow cytometry and sorting. Clonality was determined by light chain and/or immunoglobulin chain gene rearrangement PCR. We also determined aldehyde dehydrogenase activity and colony formation growth. Drug sensitivity was tested with conventional and novel agents.

RESULTS

Marrow CD19+ cells express a light chain identical to plasma cells and are therefore termed light chain restricted (LCR). The LCR B-cell mass is small in both newly diagnosed and relapsed patients (≤ 1%). Few marrow LCR B cells (~10%) are CD19+/CD34+, with the rest being more differentiated CD19+/CD34- B cells. Marrow LCR CD19+ B cells exhibit enhanced aldehyde dehydrogenase activity versus healthy controls. Both CD19+/CD34+ and CD19+/CD34- cells showed colony formation activity, with colony growth efficiency optimized when stroma-conditioned medium was used. B-cell progenitors showed resistance to melphalan, lenalidomide, and bortezomib. Panobinostat, a histone deacetylase inhibitor, induced apoptosis of LCR B cells and CD138+ cells. LCR B cells are CD117, survivin, and Notch positive.

CONCLUSIONS

We propose that antigen-independent B-cell differentiation stages are involved in disease origination and progression in myeloma. Furthermore, investigations of myeloma putative stem cell progenitors may lead to novel treatments to eradicate the potential reservoir of minimal residual disease.

Identification of translocation products but not K-RAS mutations in memory B cells from patients with multiple myeloma

BACKGROUND

Several laboratories have shown that cells with a memory B-cell phenotype can have the same clonotype as multiple myeloma tumor cells.

DESIGN AND METHODS

The aim of this study was to determine whether some memory B cells have the same genetic alterations as their corresponding multiple myeloma malignant plasma cells. The methodology included sorting multiple myeloma or memory B cells into RNA stabilizing medium for generation of subset-specific polymerase chain reaction complementary DNA libraries from one or 100 cells.

RESULTS

Cells with the phenotype of tumor plasma cells (CD38(++)CD19(-)CD45(-/+)CD56(-/+/++)) or memory B cells (CD38(-)/CD19(+)/CD27(+)) were isolated by flow activated cell sorting. In samples from all four patients with multiple myeloma and from two of the three with monoclonal gammopathy of undetermined significance, we identified memory B cells expressing multiple myeloma-specific oncogenes (FGFR3; IGH-MMSET; CCND1 high) dysregulated by an IGH translocation in the respective tumor plasma cells. By contrast, in seven patients with multiple myeloma, each of whom had tumor plasma cells with a K-RAS61 mutation, a total of 32,400 memory B cells were analyzed using a sensitive allele-specific, competitive blocker polymerase chain reaction assay, but no K-RAS mutations were identified.

CONCLUSIONS

The increased expression of a specific "early" oncogene of multiple myeloma (monoclonal gammopathy of undetermined significance) in some memory B cells suggests that dysregulation of the oncogene occurs in a precursor B-cell that can generate memory B cells and transformed plasma cells. However, if memory B cells lack "late" oncogene (K-RAS) mutations but express the "early" oncogene, they cannot be involved in maintaining the multiple myeloma tumor, but presumably represent a clonotypic remnant that is only partially transformed.

Phenotyping studies of clonotypic B lymphocytes from patients with multiple myeloma by flow cytometry

CONTEXT

Clonotypic B lymphocytes, monoclonal B lymphocytes sharing identical, rearranged IGH-CDR3 sequences with the patient's myeloma cells, have been detected in the peripheral blood of patients with multiple myeloma. These cells have been postulated to act as a therapy-resistant tumor reservoir that drives recurrence.

OBJECTIVE

To characterize clonotypic B lymphocytes for future investigation of their role in myeloma pathogenesis.

DESIGN

Harvests of cryopreserved peripheral blood stem-cells from 20 myeloma patients were enriched for clonotypic B lymphocytes. Cytoplasmic immunoglobulin light chain and surface immunophenotype were analyzed by flow cytometry. IGH-CDR3 gene-rearrangement pattern was performed to determine clonality. Posttransplant remission rate was compared with the percentage of clonotypic B lymphocytes.

RESULTS

Clonotypic B lymphocytes expressing CD34(+/-), CD38(+), CD184(+), CD31(+/-), CD50(+/-), CD138(-), CD19(-), CD20(-), and the same immunoglobulin light chain as the patients' known myeloma cells were identified in 12 of 20 patients (60%). Progenitor B lymphocytes expressing similar surface immunophenotype but opposite light chains were identified in the same patients. Polymerase chain reaction for IGH rearrangement showed clonal rearrangement pattern in clonotypic lymphocytes but not in B lymphocytes expressing light chains opposite to myeloma cells. There was no statistically significant correlation between the percentage of clonotypic B lymphocytes and response to autologous transplant.

CONCLUSIONS

Clonotypic B lymphocytes expressing CD34, but not CD19, were identified in stem cell harvests from patients with myeloma and could represent progenitor cells of neoplastic plasma cells. However, the same or similar immunophenotyping can be detected in both clonotypic B lymphocytes and benign progenitor B cells, suggesting clonality analysis might be needed to determine clonotypic B lymphocytes in patients with myeloma. Further studies are warranted to study the role of clonotypic B lymphocytes in the pathogenesis of myeloma.

Regulation of the CD56 promoter and its association with proliferation, anti-apoptosis and clinical factors in multiple myeloma

Multiple myeloma (MM) is an incurable B-cell malignancy characterised by uncontrolled growth and accumulation of malignant plasma cells in the bone marrow. Aberrant expression of CD56 in patients with MM is thought to contribute to a worsened disease course and metastasis. We therefore investigated the regulation of the CD56 promoter in relation to typical clinical factors. We used qPCR and FACS to measure the expression levels of CD56, and potential regulatory factors in patients with MM and related these with MM progression/prognosis. The transcription factors BTBD3, Pax5, RUNX1 and MMSET were positively associated with CD56 expression, as was CYCLIN D1, which is involved in disease progression, anti-apoptosis and proliferation. RUNX1 was negatively associated with the survival of stem-cell transplanted patients. Our findings propose four potential activators of the CD56 promoter and for CD56 to be involved in proliferation and anti-apoptosis, leading to disease progression in MM.

Myeloma cell expression of 10 candidate genes for osteolytic bone disease. Only overexpression of DKK1 correlates with clinical bone involvement at diagnosis

Osteolytic bone disease (OBD) in multiple myeloma (MM) is caused by interactions between MM cells and the bone marrow microenvironment and is characterized by increased osteoclastic bone resorption and decreased osteoblastic bone formation. Recently, the role of osteoblast inhibition has come into focus, especially the possible role of overexpression of DKK1, an inhibitor of the Wnt signalling pathway. Further, CKS2, PSME2 and DHFR have also been reported as candidate genes for OBD. We studied the gene expression by quantitative reverse transcription polymerase chain reaction of TNFSF11 (RANKL), TNFSF11A (RANK), TNFRSF11B (OPG), CCL3 (MIP1A), CCL4 (MIP1B), PTHR1 (PTHrp), DKK1, CKS2, PSME2 and DHFR in purified, immunophenotypic FACS-sorted plasma cells from 171 newly diagnosed MM patients, 20 patients with monoclonal gammopathy of undetermined significance and 12 controls. The gene expressions of the analysed genes were correlated with radiographically assessed OBD. Only overexpression of DKK1 was correlated to the degree of OBD. Myeloma cells did not express TNFSF11A, TNFSF11, or TNFRSF11B, and very rarely expressed CCL3 and PTHR11. CCL4, CKS2, PSME2 and DHFR were variably expressed, but the expression of these genes showed no correlation with OBD. In contrast, loss of PSME2 expression in MM plasma cells was significantly correlated with OBD.

Dysregulation ofCD47and the ligands thrombospondin 1 and 2 in multiple myeloma

CD47 and thrombospondin 1 and 2 (TSP1 and TSP2) expression were analysed by real-time reverse transcription polymerase chain reaction in fluorescence-activated cell sorted plasma cells (PCs) from patients at consecutive stages of multiple myeloma (MM) development. 80% of MM patients, but only 39% of patients with monoclonal gammopathy of undetermined significance (MGUS) expressed CD47; median expression level increased 10-fold with progression from MGUS to MM. Elevated TSP1/TSP2 levels occurred in bone marrow cultures from MM patients compared with healthy donors. CD47 and TSP1/TSP2 may have a potential role in the pathophysiology of MM, probably in the interaction between MM PCs and the microenvironment.

Toll-like receptors mediate proliferation and survival of multiple myeloma cells

Multiple myeloma (MM) is an incurable B-cell malignancy characterized by accumulation of malignant plasma cells in bone marrow (BM) and recurrent or persistent infections. Toll-like receptors (TLRs) are essential in the host defense against infections and today 10 human TLRs (TLR1-TLR10) and one TLR-homolog (RP105) have been characterized. B cells express several TLRs (mainly TLR1, 6, 7, 9, 10 and RP105) and TLR-initiated responses in B cells include proliferation, anti-apoptosis effect and plasma cell (PC) differentiation. The present study was designed to analyze the role of TLRs in MM. We show that frequent expressions of TLRs were detected in cell lines from MM patients (minimum six TLRs in each). In comparison, only few TLRs (mainly TLR1 and or RP105) were found expressed in PCs from BM of healthy donors. In addition, TLR-specific ligands induce increased proliferation and survival of the MM cell lines, partially due to an autocrine interleukin-6 production. Importantly, we demonstrate that also PC from MM patients proliferates in response to TLR-specific ligands. In conclusion, TLR-ligands may contribute to increased growth and survival of MM cells in MM patients.

Serum YKL-40 concentrations in newly diagnosed multiple myeloma patients and YKL-40 expression in malignant plasma cells

OBJECTIVES

A potential role in cancer biology is suggested for YKL-40 (CHI3L1, HC gp-39). The purpose of this study was to evaluate the clinical value of serum YKL-40 (sYKL-40) in multiple myeloma (MM) and to examine YKL-40 expression in malignant plasma cells (MM PCs).

METHODS

sYKL-40 was measured by enzyme-linked immunosorbent assay (ELISA) in 82 patients with newly diagnosed MM. YKL-40 expression in immunophenotypically defined plasma cells was investigated by double-labelled immunohistochemistry in 21 MM patients and by real-time reverse transcriptase polymerase chain reaction (RT-PCR) in cDNA archives generated by global RT-PCR in seven controls, 14 patients with monoclonal gammopathy of undetermined significance (MGUS), 45 MM patients, nine patients with extramedullary myeloma (exMM), and seven human myeloma cell lines (HMCLs).

RESULTS

sYKL-40 was elevated above a constructed reference range for healthy controls in 29% of the patients investigated. Patients with elevated sYKL-40 had reduced overall survival and event-free survival when compared to patients with normal sYKL-40, but sYKL-40 level was defeated by beta(2)-microglobulin in the multivariate analyses. Intramedullary MM PCs lacked significant expression of YKL-40, but high levels of YKL-40 expression were seen in extramedullary MM PCs from one exMM patient and in six HMCLs. Further investigations of other bone marrow (BM) cells showed YKL-40 expression in megakaryocytes, neutrophils and adherent cells from long-term BM cultures.

CONCLUSIONS

In newly diagnosed MM-patients, a sYKL-40 elevated above the reference range predicts a poor clinical outcome, and YKL-40 is expressed by other BM cells than MM PCs. At this point, routine measurements of sYKL-40 are not warranted, but YKL-40 should be considered as a potential player in the pathophysiology of MM.

Quality assessment of autografting by probability evaluation: model estimation by clinical end-points in newly diagnosed multiple myeloma patients

BACKGROUND

Pre-transplant clinical evaluation of autografting is an important step in predicting post-transplant support, complications and safety. Today, unfavorable outcomes such as early death or graft failure are rare, making them unsuitable for quality assessment of supportive autografting. However, end-points constructed from frequently occurring clinical events may estimate clinically relevant prognostic models.

METHODS

The present retrospective analysis was based on two consecutive clinical trials in the Nordic area including up to 640 newly diagnosed multiple myeloma patients.

RESULTS

In the model, the efficacy (time on antibiotics and use of transfusions) was influenced by pre-transplant variables, including sex, nationality, serum creatinine, hemoglobin, disease stage at diagnosis, response following induction therapy, length of priming and average graft CD34+ cell number per day of harvest. The toxicity end-point (time to blood cell recovery) was influenced by nationality, marrow plasma cell percentage, serum creatinine, M-component isotype, response to induction therapy, length of priming and graft CD34+ cell number. The safety (early disease recurrence or death) was influenced by serum creatinine, hemoglobin, treatment response and CD34+ cell number.

DISCUSSION

In conclusion, the model illustrates that intervention strategies in quality assessment of autografting may benefit from probability estimates of graded clinical end-points.

Identification of ID-1 as a potential target gene of MMSET in multiple myeloma

The frequently detected t(4;14)(p16.3;q32) translocation in multiple myeloma (MM) results in a dysregulation of two potential oncogenes: multiple myeloma SET domain (MMSET) and fibroblast growth factor receptor 3 (FGFR3). As the expression of FGFR3 is undetectable in 30% of the t(4;14)+ MM patients, MMSET has been suggested to play an important role in the malignant transformation associated with the t(4;14) translocation. Screening with a real-time polymerase chain reaction (PCR) found complex expression patterns of the MMSET transcripts in fluorescence-activated cell sorted (FACS)-purified plasma cells (PCs) from 15 t(4;14)+ MM patients. In addition, potential target genes of MMSET type I and II were identified, using microarray analyses of MMSET transfected cell lines. Subsequently, the expression of potential target genes was verified by real-time PCR in FACS-purified PCs from 15 t(4;14)+ and 22 t(4;14)- MM patients. We suggest that the inhibitor of differentiation 1 (ID-1) is a target gene of MMSET, based on its upregulation in MMSET transfected cell lines and a significant association between the t(4;14) translocation and ID-1 expression in MM patients (P = 0.002). As high levels of ID-1 are associated with cancer, our findings indicate that MMSET promotes oncogenic transformation in t(4;14)+ MM patients by transcriptional activation of ID-1 expression.

Heterogeneity in the multiple myeloma tumor clone

Multiple Myeloma (MM) is a plasma cell malignancy which is characterized by a very heterogeneous disease outcome. Heterogeneity in plasma cell characteristics, including morphology, maturation status, immunophenotype and genetic abnormalities partly account for the variable disease outcome. Although the plasma cell is the predominant cell type in MM, several studies have shown that less mature B cells, which are clonally related to the malignant plasma cells, are present in the bone marrow and peripheral blood of MM patients. The significance of these so-called myeloma clonotypic B cells in the disease process remains largely unknown. In this review the role of myeloma clonotypic B cells and myeloma tumor clone heterogeneity in relation to prognosis and clinical outcome are discussed.

In multiple myeloma clonotypic CD38- /CD19+ / CD27+ memory B cells recirculate through bone marrow, peripheral blood and lymph nodes

It is believed that myeloma cells are derived from a germinal center (GC) or post GC B cell. The GC B cell can differentiate into both a memory B cell and a plasma cell (PC). In this study, we investigated the recirculating potential of memory B cells clonally related to the myeloma PC (termed clonotypic). The V(H)DJ(H) immunoglobulin gene rearrangement of the myeloma clone was identified for 10 myeloma patients and allele-specific oligonucleotides (ASO) IgH RT-PCR assays were designed for each patient. Memory B cells (CD38- /CD19+ /CD27+) and their subsets defined by the monoclonal antibodies CD62L, CCR6, CXCR4, CXCR5, CCR7 were flow-sorted as single cells and analyzed by ASO RT-PCR analysis. In addition, aspirated peripheral lymph nodes (PLN) of 7 myeloma patients in complete or partial remission were analyzed for the presence of clonotypic cells. Circulating clonotypic memory B cells were identified in PBMNC of 7/10 patients and both CD62L positive and negative clonotypic memory B cells were identified. Furthermore, comparable frequencies of clonotypic cells were found in the CCR6 +/- and CXCR4 +/- memory B cell subsets, whereas all clonotypic memory and later stage B cells were CXCR5 positive. In accordance with their immunophenotype, clonotypic memory B-cells were identified in peripheral blood, bone marrow and PLNs. Clonotypic memory B-cells were present in the majority of myeloma patients and seem to have the same diverse recirculating/homing capacity as normal memory B cells.

Possible roles for activating RAS mutations in the MGUS to MM transition and in the intramedullary to extramedullary transition in some plasma cell tumors

To assess a possible role in tumor progression, the occurrence and type of K- and N-RAS mutations were determined in purified tumor cells, including samples from patients with premalignant monoclonal gammopathy of undetermined significance (MGUS), multiple myeloma (MM), and extramedullary plasma cell (PC) tumors (ExPCTs). Immunophenotypic aberrant PCs were flow sorted from 20 MGUS, 58 MM, and 13 ExPCT patients. One RAS mutation was identified in 20 MGUS tumors (5%), in contrast to a much higher prevalence of RAS mutations in all stages of MM (about 31%). Further, oncogene analyses showed that RAS mutations are not evenly distributed among different molecular subclasses of MM, with the prevalence being increased in MM-expressing cyclin D1 (P = .015) and decreased in MM with t(4;14) (P = .055). We conclude that RAS mutations often provide a genetic marker if not a causal event in the evolution of MGUS to MM. Surprisingly, RAS mutations were absent in bone marrow tumor cells from all patients with ExPCT, a result significantly different from intramedullary MM (P = .001). From 3 of 6 patients with paired intramedullary and extramedullary PCs and identical immunoglobulin heavy chain gene (IgH) sequences, RAS mutations were identified only in extramedullary PCs, suggesting a role for RAS mutations in the transition from intramedullary to extramedullary tumor.

Occurrence of dysregulated oncogenes in primary plasma cells representing consecutive stages of myeloma pathogenesis: indications for different disease entities

This study investigated the expression pattern in primary plasma cells (PCs) of putative oncogenes suggested to be involved in multiple myeloma (MM) development. cDNA archives were generated by global reverse transcription polymerase chain reaction from CD38++/CD19-/CD56-/++ aberrant PCs of a prospective cohort of 96 subjects, including healthy individuals, patients with monoclonal gammopathies of undetermined significance (MGUS), MM and MM with extramedullary manifestations (ExMM). The cDNA archives were analysed quantitatively for expression of the cyclin D1, fibroblast growth factor receptor 3 (FGFR3), C-MYC, C-MAF and cyclin D3 oncogenes. In addition, all patients were screened for IGH-MMSET hybrid transcripts. None of the analysed oncogenes was randomly distributed. C-MYC and cyclin D3 expression increased at the extramedullary transformation stage. Furthermore, C-MYC and cyclin D3 expression in CD56+ MM was similar to MGUS, whereas CD56- MM was similar to ExMM. FGFR3/IGH-MMSET was only observed among CD56+ MM patients, whereas an increased frequency of C-MAF dysregulation was seen among CD56- MM. High cyclin D1 expression levels were identified at similar frequencies at all stages, whereas the frequency of patients with low cyclin D1 levels increased during MM development. These data support the stepwise transformation model accumulating genetic alterations and proliferative capacity during MM initiation and development resulting in different clinical entities.

Idiotype vaccination in multiple myeloma induced a reduction of circulating clonal tumor B cells

Myeloma cells express the idiotype (Id)-specific antigen that may be targeted by Id vaccination. Six patients with stage I IgG myeloma were immunized with the autologous purified M component together with the adjuvant cytokines interleukin 12 (IL-12) alone or in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF). The effect of Id vaccination on circulating clonal tumor B cells was monitored by a real-time allele-specific oligonucleotide polymerase chain reaction method. No other treatment was given. Reduction of blood tumor mass was observed in 4 of 6 patients, with one patient achieving a complete molecular remission in blood. In 3 of these 4 patients an Id-specific T-cell response was induced. In the remaining 2 patients with an unchanged level of blood tumor cells, one patient mounted a T-cell response, whereas the other did not. No significant change in the serum M protein level was noted. Id vaccination may target clonal B cells, suggesting that this strategy might be conducive to achieving tumor control. The clinical significance of these findings remains to be established.

Feasibility of fludarabine added to VAD during induction therapy in multiple myeloma: a randomised phase II-study

Multiple myeloma (MM) is considered to be an essentially incurable haematological malignant disease, probably because of the existence of resistant clonal precursor cell with self-renewal capacity. Recent data have indicated that the myeloma cell hierarchy includes circulating clonal memory B cells, which differ considerably from the classical end-stage plasma cells, infiltrating the bone marrow. The pathophysiological significance of these cells is unknown, but hypothetically they may serve as 'sleeping' myeloma stem cells responsible for and 'feeding' post-treatment relapse and progression. The present study evaluates the toxicity and feasibility of fludarabine, added to the VAD-induction regimen in MM, and investigates the effect on the myeloma cell hierarchy. Nineteen patients were randomised to receive either four cycles of VAD (n = 9) or two cycles of VAD, followed by two cycles of VAD combined with 5 days fludarabine 25 mg/m2/day i.v. (n = 10). Toxicity evaluation showed more profound neutropenia in the fludarabine-treated patients and two infectious episodes in each study arm: three were fever of unknown origin while one, in the fludarabine-arm, was a local skin infection at the insertion site of the central venous line. Nine of the fludarabine-treated patients responded to treatment (two complete remission, seven partial remission), compared with five responders (all PR) in the control-arm. The effects on the blood circulating myeloma compartments identified an increased reduction of CD19+ B cells and myeloma plasma cells in the fludarabine-arm. In conclusion, adding fludarabine to VAD induction in multiple myeloma is feasible and may be clinically effective by reducing the myeloma clone.

FGFR3 dysregulation in multiple myeloma: frequency and prognostic relevance

The t(4:14) translocation affects two potential oncogenes, FGFR3 and MMSET, in multiple myeloma (MM). We investigated the frequency of FGFR3 dysregulation and its prognostic value in MM. FGFR3 mRNA levels were determined in 110 diagnostic bone marrow (BM) samples from MM patients. In addition, selected BM samples were screened for elevated MMSET mRNA levels. 14.5% (16/110) of MM BM samples showed dysregulated FGFR3 expression. Follow-up of 76 MM patients showed no significant difference between FGFR3 dysfunction and survival (P = 0.3) or correlation with known prognostic factors. Further, no linear relation was observed between FGFR3 and MMSET levels.

The CD19 compartment in myeloma includes a population of clonal cells persistent after high-dose treatment

Peripheral blood-localized clonal cells in patients with multiple myeloma (MM) have been reported to be insensitive to chemotherapy and it has been suggested that these cells may include the proliferative compartment in myeloma. In this study, circulating clonal CD19+ cells levels were determined in 10 patients with MM by performing patient-specific RT-PCR on single flow-sorted CD19+ cells. A variable proportion of CD+ cells being clonal were identified (0.101-6.130%, mean 1.019%). In 10/10 MM patients clonal CD19+ cells were found after high-dose treatment and peripheral blood stem cell transplantation. In conclusion, CD19+ clonal cells include a population of cells persistent after high dose chemotherapy that may be responsible for relapse.

Differential expression of CD56 and CD44 in the evolution of extramedullary myeloma

We report on the different expression of CD56 and CD44 in plasma cells (PCs) simultaneously collected from bone marrow, extramedullary locations and peripheral blood in seven patients with multiple myeloma. Extramedullary PCs showed absence of CD56. In the bone marrow, however, subsets with varying CD56 expression were found in five out of seven patients, with one subset corresponding to that of extramedullar PCs. This differs from the de novo downregulation of CD56 in PC leukaemia, and suggests different mechanisms of spread of myeloma cells. CD44 expression was generally upregulated on extramedullary PCs. In three of the patients we investigated the clonal origin of extramedullary myeloma cells by sequencing the variable portion of the heavy chain immunoglobulin gene in phenotypically defined PCs isolated from different locations. In each patient we found malignant PCs with different homing behaviour originating from a common precursor cell.

Efficacy and safety of CD34-selected and CD19-depleted autografting in multiple myeloma patients: a pilot study

OBJECTIVE

If multiple myeloma patients are to be cured after high-dose treatment supported by autologous stem cell transplantation, grafts must be purged of circulating myeloma cells. Myeloma cells are present in all grafts and have been identified as CD38(++)CD45(-) plasma cells, plasma blasts, and CD19(+) B cells.

MATERIALS AND METHODS

In an attempt to improve the purging strategy, we studied a two-step procedure consisting of CD34(+) enrichment followed by CD19 depletion. This article describes the evaluation of this sequential magnetic microbead selection after 18 procedures in 14 patients.

RESULTS

The processed autografts contained a median CD34 purity of 81% (range 21-99%) and a recovery of 47% (range 15-82%). Flow cytometric analysis documented the expected reduction of CD34(-) B cells and plasma cells, in most cases to a level below the sensitivity of flow cytometry. Real-time reverse transcriptase polymerase chain reaction documented a CD19 mRNA relative reduction to 0.042 (range 0.01-0.21). Allele-specific oligonucleotide IgH primers were designed for five patients. All products were positive for clonal myeloma cells before processing, but only 1 of 5 was negative after the procedure. The clinical outcome after reinfusion of the processed autografts was evaluated by blood cell recovery and found to be within the range expected from engraftment of unmanipulated autografts. One patient who had delayed platelet recovery associated with cytomegalovirus infection recovered after anti-cytomegalovirus treatment.

CONCLUSIONS

This pilot study documented engraftment after reinfusion of CD34-selected and CD19-depleted autografts. However, one patient suffered from unexpected prolonged thrombocytopenia. The efficacy of the procedure was evaluated and reduction of myeloma cells was indicated, with only one autograft free of clonal cells.

Mobilisation of tumour cells along with CD34+ cells to peripheral blood in multiple myeloma

BACKGROUND

Cells belonging to the malignant clone are found in the peripheral blood in myeloma patients. In order to minimise the content of tumour cells in the stem cell product it is crucial to perform stem cell harvest at a time when tumour cells in the peripheral blood are at a minimum.

OBJECTIVE

The aim of the study was to compare the mobilisation kinetics of normal CD34+ cells and myeloma plasma cells during mobilisation with either G-CSF alone or high-dose cyclophosphamide (HDCy) plus G-CSF.

DESIGN AND METHODS

Morning blood samples were drawn each day during mobilisation from start of G-CSF or HDCy and to the end of leukapheresis, and were analysed by flow cytometry for content of CD34+ cells and myeloma plasma cells (CD38+ + CD45-). Tumour cells were also estimated by a patient-specific real-time polymerase chain reaction (PCR) method based on the 5' nuclease TaqMan technology.

RESULTS

Flow cytometry data from 16 patients showed concomitant mobilisation of CD34+ cells and myeloma plasma cells. Seven patients were mobilised twice; first with G-CSF alone and then with HDCy plus G-CSF. There was no difference between the two mobilisation regimens regarding tumour cell mobilisation kinetics. Real-time PCR was performed in one patient and confirmed the mobilisation of tumour cells at the time when CD34+ blood cells were at a maximum.

CONCLUSIONS

Tumour cells are mobilised to the peripheral blood at the same time as CD34+ cells in multiple myeloma patients after priming with both G-CSF alone and HDCy in combination with G-CSF.

Purging of autologous peripheral-blood stem cells using CD34 selection does not improve overall or progression-free survival after high-dose chemotherapy for multiple myeloma: results of a multicenter randomized controlled trial

PURPOSE

Although high-dose chemotherapy supported by autologous peripheral-blood progenitor-cell (PBPC) transplantation improves response rates and survival for patients with multiple myeloma, all patients eventually develop progressive disease after transplantation. It has been hypothesized that depletion of malignant plasma cells from autografts may improve outcome by reducing infused cells contributing to relapse.

PATIENTS AND METHODS

A randomized phase III study using the CEPRATE SC System (Cellpro, Bothell, WA) to enrich CD34(+) autograft cells and passively purge malignant plasma cells was completed in 190 myeloma patients randomized to receive an autograft of CD34-selected or unselected PBPCs.

RESULTS

After CD34 selection, tumor burden was reduced by 1.6 to 6.0 logs (median, 3.1), with 54% of CD34-enriched products having no detectable tumor. Median time to count recovery, number of transfusions, transplantation-related mortality, and days in hospital were equivalent between the two transplantation arms. With a median follow-up of 37 months, 33 patients (36%) in the selected and 34 patients (35%) in the unselected arm had died (P =.784). Median overall survival in the selected arm was reached at 50 months and is not reached at this time in the unselected arm (P =.78). Median disease-free survival was 100 versus 104 weeks (P =.82), with 67% of patients in the selected arm and 66% of patients in the unselected arm relapsing.

CONCLUSION

This phase III trial demonstrates that although CD34 selection significantly reduces myeloma cell contamination in PBPC collections, no improvement in disease-free or overall survival was achieved.

Frequency and kinetics of polyclonal and clonal B cells in the peripheral blood of patients being treated for multiple myeloma

Recent studies concerning the numbers of circulating clonal B cells in patients with multiple myeloma (MM) have reported conflicting data regarding the exact level and phenotype of clonal B cells and their response to treatment. In this report we document that the peripheral blood tumor burden at presentation was reduced by induction therapy to a low level, regardless of the initial tumor burden. However, the residual clonal compartment persisted before and after transplant. The level of clonal cells showed no correlation with CD19+cell levels. In a single patient with MM, high numbers of phenotypically aberrant clonal cells with altered CD19 expression were identified.

Frequency and kinetics of polyclonal and clonal B cells in the peripheral blood of patients being treated for multiple myeloma

Recent studies concerning the numbers of circulating clonal B cells in patients with multiple myeloma (MM) have reported conflicting data regarding the exact level and phenotype of clonal B cells and their response to treatment. In this report we document that the peripheral blood tumor burden at presentation was reduced by induction therapy to a low level, regardless of the initial tumor burden. However, the residual clonal compartment persisted before and after transplant. The level of clonal cells showed no correlation with CD19+cell levels. In a single patient with MM, high numbers of phenotypically aberrant clonal cells with altered CD19 expression were identified.

A comparative study of sequential priming and mobilisation of progenitor cells with rhG-CSF alone and high-dose cyclophosphamide plus rhG-CSF

Stem cell mobilisation can be achieved either by administration of rhG-CSF alone or after high-dose cyclophosphamide (HDCy) plus rhG-CSF. We have compared both mobilisation procedures intra-individually in 43 patients with haematological malignancies. Furthermore, the toxicity data were registered. The CD34+ cell yield was higher after mobilisation with HDCy plus rhG-CSF than after rhG-CSF alone in 21 out of 22 patients who were actually harvested after both procedures. If a patient mobilised insufficiently after rhG-CSF alone, the yield of CD34+ cells after the following HDCy priming was lower compared to patients who mobilised sufficiently after rhG-CSF priming alone. In 12 patients with B cell malignancies a reduced number of B cells such as CD10+, CD19+, CD20+ cells in bone marrow as well as in leukapheresis products was observed after HDCy plus rhG-CSF compared to rhG-CSF alone. Toxicity data revealed HDCy as a relatively toxic priming regimen with all patients hospitalised and 74% experiencing neutropenic fever and administration of intravenous antibiotics. In two patients, seizure-like episodes were observed during cyclophosphamide bolus infusion. In conclusion, HDCy increased the yield of CD34+cell and reduced B cells in leukapheresis products indicating reduced tumour cell load compared with rhG-CSF priming alone. The efficacy of HDCy priming is limited by its profound toxicity and morbidity. Studies evaluating efficacy and safety of lower doses of cyclophosphamide are needed. Bone Marrow Transplantation (2000) 26, 717-722.

Technical aspects and clinical impact of hematopoietic progenitor subset quantification

As high-dose therapy for malignancies is now being applied to newly diagnosed patients as adjuvant therapy, it has become a requirement that quality and safety assessment of hematopoietic stem cell grafts be evidence-based. This process has developed a new institution in medicine, the stem cell laboratory. In most cases this speciality has evolved from or within hematological research laboratories. However, the increased routine technologies applied in quality evaluation, ex vivo manipulation and safety assessment in stem cell handling naturally places this activity in transfusion medicine. Multiparametric flow cytometry can identify progenitor subsets in normal human bone marrow and peripheral blood, and such subset quantification has been used retrospectively to predict three-lineage engraftment following high-dose therapy for malignancies. Published single center data have suggested an impact on clinical outcome, and a standardized technique for subset enumeration needs to be established before prospective multicenter trials can be initiated to document the prognostic value of such quality assessment in autografting. Based on experiences of CD34 enumeration, which we consider to be the first step in quality assessment of hematopoietic stem cell grafts, this review discusses flow cytometry subset identification by lineage-specific differentiation markers, stromal-dependent adherence molecules, and regulatory growth factor receptors from a technical point of view. The aim of this review is:To recommend a simple method based on the experiences of the Nordic workshop III on subset identification; To present new molecular genetic-based methods for future use in quality assessment; and To propose new endpoints necessary for validation of the likely clinical impact of subsets in prospective trials. As sample differences between blood and marrow result in technical difficulties, this review only focuses on the methodology of identifying subsets in blood and leukapheresis products. Methods for subset analysis in diagnostic bone marrow samples will be covered in a forthcoming review.