Review of phenotypic markers used in flow cytometric analysis of MGUS and MM, and applicability of flow cytometry in other plasma cell disorders

Detection of clonal plasma cells in POEMS syndrome using multiparameter flow cytometry

POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein [M-protein], and skin changes) is a rare systemic disorder characterized by various symptoms caused by underlying plasma cell (PC) dyscrasia. Detection of monoclonal PCs is mandatory for the diagnosis of POEMS syndrome; however, the usefulness of EuroFlow-based next-generation flow cytometry (EuroFlow-NGF) in POEMS syndrome for detecting monoclonal PCs in bone marrow (BM) and the gating strategy suitable for flow cytometry study of POEMS syndrome remain unknown. We employed EuroFlow-NGF-based single-tube eight-color multiparameter flow cytometry (MM-flow) and established a new gating strategy (POEMS-flow) to detect the monoclonal PCs in POEMS syndrome, gating CD38 broadly from dim to bright and CD45 narrowly from negative to dim compared to MM-flow. MM-flow detected monoclonal PCs in 9/25 (36.0%) cases, including 2/2 immunofixation electrophoresis (IFE)-negative cases (100%). However, POEMS-flow detected monoclonal PCs in 18/25 cases (72.0%), including 2/2 IFE-negative cases (100%). POEMS-flow detected monoclonal PCs with immunophenotypes of CD19- in 17/18 (94.4%). In six cases where post-treatment samples were available, the size of the clones was significantly reduced after the treatment (P = 0.031). POEMS-flow can enhance the identification rate of monoclonal PCs in POEMS syndrome and become a valuable tool for the diagnosis of POEMS syndrome.

Past, Present, and a Glance into the Future of Multiple Myeloma Treatment

Multiple myeloma (MM) is a challenging hematological cancer which typically grows in bone marrow. MM accounts for 10% of hematological malignancies and 1.8% of cancers. The recent treatment strategies have significantly improved progression-free survival for MM patients in the last decade; however, a relapse for most MM patients is inevitable. In this review we discuss current treatment, important pathways for proliferation, survival, immune suppression, and resistance that could be targeted for future treatments.

Multiple Myeloma Immunophenotype Related to Chromosomal Abnormalities Used in Risk Assessment

(1) Background: At diagnosis, multiplemyeloma risk estimation includes disease burden, end-organ damage, and biomarkers, with increasing emphasis on genetic abnormalities. Multicolor flow cytometry (MFC) is not always considered in risk estimation. We demonstrate associations found between genetic abnormalities and antigen expression of plasma cells measured by MFC. (2) Methods: Single nucleotide polymorphism microarray (SNP-A) karyotyping as well as MFC using standardized next-generation flow (NGF) panels and instrument settings were performed from bone marrow aspirates at the time of diagnosis. (3) Results: We uncovered specific immunophenotype features related to different genetic risk factors. Specifically, we found higher malignant/normal plasma cell ratio and lower expression of CD27, CD38, CD45, CD56, CD117 and CD138 in higher-risk genetic groups or risk categories.

Outcomes of stem cell mobilization and engraftment in patients with multiple myeloma according to CD56 expression status

BACKGROUND

The molecular mechanism underlying the mobilization and engraftment of CD34+ cells is poorly understood. The most relevant factors in the regulation of stem cell release and engraftment include chemokines, adhesion molecules, and chemokine receptors. Previously, it was suggested that the absence of CD56 expression could be used as a predictive factor for mobilization failure at the time of diagnosis. Here, we investigated the effect of CD56 expression status on both mobilization and engraftment processes. Additionally, other factors affecting mobilization and engraftment efficacy were investigated.

METHODS

Data from 79 multiple myeloma patients undergoing autologous stem cell transplantation between 2015 and 2020 were analyzed for peripheral stem cell mobilization and posttransplant neutrophil and platelet engraftment according to CD56 expression on myeloma cells.

RESULTS

No difference in either the median number of CD34+ cells collected or time to engraftment was found between the CD56+ and CD56- groups. The age of the patients (p = 0.025) and peak number of circulating CD34+ cells in peripheral blood (p = 0.005) were important predictors for a higher number of collected CD34+ cells. The average time to recovery of leukocytes and platelets after transplantation was markedly correlated with the number of transplanted stem cells and peak number of circulating CD34+ cells in peripheral blood, respectively (p = 0.049 and p = 0.003).

CONCLUSIONS

Our results indicated no effect of CD56 expression status on the mobilization and engraftment of PBSCs. Our results also support the notion that the peak number of circulating CD34+ cells in peripheral blood is clinically important for rapid platelet engraftment following HPC transplantation.

Primary Plasma Cell Leukemia Revealed by a Mandibular Lesion: A Case Report

Primary plasma cell leukemia (PCL) is a rare and aggressive hematological malignancy exhibiting a circulating plasma cell count exceeding 20% of peripheral blood leukocytes or an absolute plasma cell count >2000/mm3. We report a case of a 37-year-old woman presented to the Department of Hematology with a two-month history of growth inside the oral cavity in the upper jaw and weakness. The physical examination revealed a voluminous mass involving the left side of the maxillary gingiva. The maxillofacial computerized tomography (CT) scan confirmed the presence of a solid tissue mass at the left upper maxilla. A biopsy sample obtained from the lesion showed a plasma cell infiltration. The laboratory findings revealed anemia, renal impairment with high levels of creatinine and calcium. Serum protein electrophoresis found a monoclonal peak at IgG lambda, a high level of lambda free light. The diagnosis was subsequently confirmed by a peripheral-blood smear revealed 25% of plasma cells and bone marrow aspiration with 50% of plasma cell infiltration. Primary plasma-cell leukemia (pPCL) was confirmed. The patient received VTD chemotherapy (bortezomib, thalidomide, and dexamethasone) followed by autologous stem cell transplant (ASCT), which resulted in complete remission. At the six-month follow-up, the patient relapsed with extramedullary multiple lesions under ineffective rescue therapy. Response to frontline treatments may be significant initially but short-lived with a dismal median overall survival below one year. This case report aims to highlight the need for awareness among clinicians of the relevance of examining other associated clinical features of pPCL, given its aggressive course and rapid progress without the therapy.

Identification and Characterization of Tumor-Initiating Cells in Multiple Myeloma

BACKGROUND

Treatment failures in cancers, including multiple myeloma (MM), are most likely due to the persistence of a minor population of tumor-initiating cells (TICs), which are noncycling or slowly cycling and very drug resistant.

METHODS

Gene expression profiling and real-time quantitative reverse transcription polymerase chain reaction were employed to define genes differentially expressed between the side-population cells, which contain the TICs, and the main population of MM cells derived from 11 MM patient samples. Self-renewal potential was analyzed by clonogenicity and drug resistance of CD24+ MM cells. Flow cytometry (n = 60) and immunofluorescence (n = 66) were applied on MM patient samples to determine CD24 expression. Therapeutic effects of CD24 antibodies were tested in xenograft MM mouse models containing three to six mice per group.

RESULTS

CD24 was highly expressed in the side-population cells, and CD24+ MM cells exhibited high expression of induced pluripotent or embryonic stem cell genes. CD24+ MM cells showed increased clonogenicity, drug resistance, and tumorigenicity. Only 10 CD24+ MM cells were required to develop plasmacytomas in mice (n = three of five mice after 27 days). The frequency of CD24+ MM cells was highly variable in primary MM samples, but the average of CD24+ MM cells was 8.3% after chemotherapy and in complete-remission MM samples with persistent minimal residual disease compared with 1.0% CD24+ MM cells in newly diagnosed MM samples (n = 26). MM patients with a high initial percentage of CD24+ MM cells had inferior progression-free survival (hazard ratio [HR] = 3.81, 95% confidence interval [CI] = 5.66 to 18.34, P < .001) and overall survival (HR = 3.87, 95% CI = 16.61 to 34.39, P = .002). A CD24 antibody inhibited MM cell growth and prevented tumor progression in vivo.

CONCLUSION

Our studies demonstrate that CD24+ MM cells maintain the TIC features of self-renewal and drug resistance and provide a target for myeloma therapy.

Multiparameter Flow Cytometry for the Identification of Neoplastic Plasma Cells in POEMS Syndrome with IgG-kappa Gammopathy: Successful Treatment Using Lenalidomide and Dexamethasone

A 72-year-old man presented with a 6-month history of systemic edema. Hyperpigmentation, hemangioma, pleural effusion, IgG-kappa-type monoclonal protein, high vascular endothelial growth factor values, renal failure, and nerve conduction study abnormalities were also present. Multiparameter flow cytometry (MFC) showed 0.2% neoplastic plasma cells (CD38-, CD56-, and kappa-positive; CD19-, CD27-, and lambda-negative) in the bone marrow leading to POEMS syndrome. Cases involving kappa-type POEMS syndrome are extremely rare. A kidney biopsy revealed membranous proliferative glomerulonephritis-like changes in our case. Lenalidomide-dexamethasone therapy improved the renal function. Detection of neoplastic plasma cells by MFC was useful for the accurate diagnosis and treatment evaluation.

The Covalent CDK7 Inhibitor THZ1 Potently Induces Apoptosis in Multiple Myeloma Cells In Vitro and In Vivo

PURPOSE

The goal of this study was to characterize the activity of the covalent CDK7 inhibitor THZ1 in multiple myeloma models.

EXPERIMENTAL DESIGN

Multiple myeloma lines were exposed to varying THZ1 concentrations alone or with carfilzomib or ABT-199, after which apoptosis was monitored by flow cytometry, protein expression by Western blot analysis, mRNA by RT-PCR. Analogous studies were performed in cells ectopically expressing c-MYC, MCL-1, or BCL-XL, or CRISPER-Cas CDK7 sgRNA knockout. Primary multiple myeloma cells were exposed to THZ1 ± carfilzomib or ABT-199. In vivo effects of THZ1 were examined in a systemic U266 xenograft model.

RESULTS

THZ1 markedly diminished multiple myeloma cell proliferation and survival despite bortezomib or stromal cell resistance in association with G₂-M arrest, inactivation of CTD RNA Pol II, dephosphorylation of CDKs 7 as well as 1, 2, and 9, and MCL-1, BCL-xL, and c-MYC mRNA or protein downregulation. Ectopic MCL-1, c-MYC, or BCL-X_L expression significantly protected cells from THZ1 lethality. Both THZ1 and CRISPR-Cas CDK7 knockout sharply diminished multiple myeloma cell proliferation and significantly increased carfilzomib and ABT-199 lethality. Parallel effects and interactions were observed in primary CD138⁺ (N = 22) or primitive multiple myeloma cells (CD138^-/CD19⁺/CD20⁺/CD27⁺; N = 16). THZ1 administration [10 mg/kg i.p. twice daily (BID), 5 days/week] significantly improved survival in a systemic multiple myeloma xenograft model with minimal toxicity and induced similar events observed in vitro, for example, MCL-1 and c-MYC downregulation.

CONCLUSIONS

THZ1 potently reduces multiple myeloma cell proliferation through transcriptional downregulation of MCL-1, BCL-X_L, and c-MYC in vitro and in vivo. It warrants further attention as a therapeutic agent in multiple myeloma.

An ontology for representing hematologic malignancies: the cancer cell ontology

BACKGROUND

Within the cancer domain, ontologies play an important role in the integration and annotation of data in order to support numerous biomedical tools and applications. This work seeks to leverage existing standards in immunophenotyping cell types found in hematologic malignancies to provide an ontological representation of them to aid in data annotation and analysis for patient data.

RESULTS

We have developed the Cancer Cell Ontology according to OBO Foundry principles as an extension of the Cell Ontology. We define classes in Cancer Cell Ontology by using a genus-differentia approach using logical axioms capturing the expression of cellular surface markers in order to represent types of hematologic malignancies. By adopting conventions used in the Cell Ontology, we have created human and computer-readable definitions for 300 classes of blood cancers, based on the EGIL classification system for leukemias, and relying upon additional classification approaches for multiple myelomas and other hematologic malignancies.

CONCLUSION

We have demonstrated a proof of concept for leveraging the built-in logical axioms of the ontology in order to classify patient surface marker data into appropriate diagnostic categories. We plan to integrate our ontology into existing tools for flow cytometry data analysis to facilitate the automated diagnosis of hematologic malignancies.

Flow Cytometric Evaluation of Traditional and Novel Surface Markers for the Diagnosis of Plasma Cell Dyscrasias

Increasing interest has been expressed for flow cytometric immunophenotyping for diagnosis and monitoring in plasma cell dyscrasias over the last decades. The aim of this investigation was to compare the expression strength of various cell surface markers used traditionally or currently under investigation on normal and abnormal PC populations. We enrolled 295 consecutive patients undergoing bone marrow aspiration in the workup of monoclonal gammopathies, selecting 54 normal and 241 abnormal PC populations via flow cytometry to characterize the expression of CD45, CD38, CD138, CD19, CD56, CD20, CD27, CD28, CD81, CD117 and CD200 on the cell surface of PCs. We observed significant differences in the expression strength of all assessed markers between normal and abnormal PC populations in all markers except for CD20. While none of them was conclusive on its own, the combination of CD81 positivity and CD117 negativity was present in 98.1% of normal PC populations tested. In contrast, particularly CD117 positivity, but also CD81 negativity was indicative of an abnormal PC phenotype. Our results highlight the descriptive value of CD81 and CD117 for the allocation of bone marrow PCs to a normal or abnormal phenotype.

Lower number of 5-hydroxymethylcytosine-expressing cells in plasma cell myeloma than in reactive plasma cell hyperplasia: a useful immunohistochemical approach for identification of neoplastic plasma cells

Plasma cell myeloma (PCM) is a haematological malignancy defined by aberrant proliferation of plasma cells in the bone marrow. For the diagnosis of PCM, immunostaining of light chains or surface marker analyses by flow cytometry is needed but sometimes difficult. Aberrant methylation at the carbon-5 position of cytosine results in 5-methylcytosine (5-mC), which is a well-known epigenetic hallmark of cancer in mammals. 5-mC is oxidised to 5-hydroxymethylcytosine (5-hmC), and low 5-hmC levels occur in several cancers and haematopoietic malignancies. We compared the expression of 5-hmC by immunohistochemistry (IHC) in neoplastic plasma cells in 31 PCM cases and in non-neoplastic plasma cells in 14 benign reactive lesions. The mean percentage of 5-hmC-positive cells was 7.8% and 81.5% in PCM and plasma cell hyperplasia, respectively. Thus, the frequency of 5-hmC-positive cells in PCM specimens was significantly lower than that in reactive plasma cell hyperplasia (p < 0.001 by Student's t-test). IHC of 5-hmC is a useful method for differentiating neoplastic plasma cells from non-neoplastic plasma cells in reactive lesions even in tiny tissue samples unsuitable for flow cytometric analyses or for immunoglobulin light chain IHC.

Immunotherapy: A Novel Era of Promising Treatments for Multiple Myeloma

Multiple myeloma (MM) remains an incurable hematological malignancy characterized by clonal proliferation of malignant plasma cells in bone marrow. In the last 20 years, the introduction of autologous stem cell transplantation, followed by proteasome inhibitors and immunomodulatory agents, increased the survival of MM patients by 50%. However, still a high proportion of patients relapse and become refractory, especially, high-risk patients with adverse cytogenetics where these treatment combinations have shown limited benefit. Therefore, novel strategies, such as immunotherapy, have been developed in the last few years to help improve the survival of these patients. Immunotherapy treatments include a high number of different strategies used to attack the tumor cells by using the immune system. Here, we will review the most successful immunotherapy strategies published up to date in patients with relapsed or refractory (R/R) MM, including monoclonal antibodies targeting specific antigens on the tumor cells, antibodies combined with cytotoxic drugs or Antibodies Drug Conjugates, immune checkpoint inhibitors which eliminate the barriers that damper immune cells and prevent them from attacking tumor cells, bi-specific T-cell engagers antibodies (BiTEs), bi-specific antibodies and the infusion of chimeric antigen receptor-modified T cells. We overview the results of clinical studies that have been presented up to date and also review pre-clinical studies describing potential novel treatments for MM.

Multiparameter Flow Cytometry Identification of Neoplastic Subclones: A New Biomarker in Monoclonal Gammopathy of Undetermined Significance and Multiple Myeloma

Multiparameter flow cytometry (MFC)-based clonality assessment is a powerful method of diagnosis and follow-up in monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma (MM). However, the relevance of intraclonal heterogeneity in immunophenotypic studies remains poorly understood. The main objective of this work was to characterize the different immunophenotypic subclones in MGUS and MM patients and to investigate their correlation with disease stages. An 8-color MFC protocol with 17 markers was used to identify the subclones within the neoplastic compartment of 56 MGUS subjects, 151 newly diagnosed MM patients, 30 MM subjects in complete remission with detectable minimal residual disease, and 36 relapsed/refractory MM patients. Two or more clusters were observed in > 85% of MGUS subjects, 75% of stage I MM patients, and < 15% in stage III. Likewise, a significant correlation between the dominant subclone size, secondary cytogenetic features, and changes in the expression of CD27, CD44, and CD81 was detected. The loss of intraclonal equilibrium may be an important factor related with kinetics and risk of progression not well considered to date in MFC studies. The MFC strategy used in this work can provide useful biomarkers in MGUS and MM.

Expression of TRPM8 in human reactive lymphoid tissues and mature B-cell neoplasms

Transient receptor potential melastatin 8 (TRPM8) is a member of the transient receptor potential superfamily of Ca²⁺ channels. The aim of the present study was to clarify TRPM8 expression in reactive lymphoid tissues and mature B-cell neoplasms. Reactive and neoplastic lymphoid tissues were used to evaluate TRPM8 expression by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). TRPM8⁺ cells were frequently detected in the follicular light zone and marginal zone of reactive lymphoid tissues. Double immunostaining revealed that TRPM8⁺ cells co-expressed cluster of differentiation (CD) 38, CD79a, CD138, interferon regulatory factor 4/melanoma associated antigen (mutated) 1, B cell CLL/lymphoma 6 and transmembrane activator and CAML interactor. TRPM8⁺ neoplastic cells were frequently detected in plasma cell myeloma. The positive band of TRPM8 mRNA was confirmed by RT-PCR in cases of myeloma. The present study is, to the best of our knowledge, the first to demonstrate the expression of TRPM8 in reactive lymphoid tissues and mature B-cell neoplasms, revealing that TRPM8 is frequently expressed in pre-plasmablasts, plasmablasts, plasma cells and mature B-cell lymphomas that are likely to differentiate into plasma cells.

Flow cytometric aberrancies in plasma cell myeloma and MGUS - correlation with laboratory parameters

BACKGROUND

Multiparametric flow cytometry is a useful tool for diagnosis of plasma cell (PC) dyscrasias and assessment of minimal residual disease in plasma cell myeloma (PCM). However, the immunophenotypic differences between the clonal PCs of PCM and those of monoclonal gammopathy of undetermined significance (MGUS) as well as the correlation of these flow cytometric markers with pertinent laboratory parameters have not been evaluated.

METHODS

We retrospectively identified all newly diagnosed treatment-naive PCM and MGUS patients between 09/2014 and 06/2015 who underwent 10-color flow-cytometric evaluation: CD45, CD38, CD138, cKappa, cLambda, CD19, CD27, CD28, CD56, CD117. FACSDiva analysis was used to identify antigenic aberrancies and associations with pertinent laboratory parameters were evaluated.

RESULTS

All cases demonstrated at least two aberrancies. There was a trend toward a greater number of aberrancies in PCM, with 68% showing >/= 4 aberrancies compared with 44% in MGUS (P = 0.11). The only marker more frequently aberrant in one disease class was CD19, aberrant in 68% of PCM and 25% of MGUS (P < 0.01). In PCM, significant associations were found for CD56 non-aberrancy (P = 0.05) and the presence of amyloid and CD27 aberrancy and normal serum albumin (P = 0.05). In MGUS, CD117 expression was associated with normal hemoglobin (P = 0.03).

CONCLUSIONS

The PCs of PCM show a trend toward more antigenic aberrancy than those of MGUS. There is significant association between the antigenic profiles of PCM/MGUS and clinical parameters including amyloidosis, albumin level, and hemoglobin. © 2018 International Clinical Cytometry Society.

CD24, CD27, CD36 and CD302 gene expression for outcome prediction in patients with multiple myeloma

Multiple myeloma (MM) is a B cell neoplasia characterized by clonal plasma cell (PC) proliferation. Minimal residual disease monitoring by multi-parameter flow cytometry is a powerful tool for predicting treatment efficacy and MM outcome. In this study, we compared CD antigens expression between normal and malignant plasma cells to identify new potential markers to discriminate normal from malignant plasma cells, new potential therapeutic targets for monoclonal-based treatments and new prognostic factors. Nine genes were significantly overexpressed and 16 were significantly downregulated in MMC compared with BMPC (ratio ≥2; FDR CD24, CD27, CD36 and CD302) was associated with a prognostic value in two independent cohorts of patients with MM (HM cohort and TT2 cohort, n=345). The expression level of these four genes was then used to develop a CD gene risk score that classified patients in two groups with different survival (P = 2.06E-6) in the HM training cohort. The prognostic value of the CD gene risk score was validated in two independent cohorts of patients with MM (TT2 cohort and HOVON65/GMMGHD4 cohort, n=282 patients). The CD gene risk score remained a prognostic factor that separated patients in two groups with significantly different overall survival also when using publicly available data from a cohort of relapsing patients treated with bortezomib (n=188). In conclusion, the CD gene risk score allows identifying high risk patients with MM based on CD24, CD27, CD36 and CD302 expression and could represent a powerful tool for simple outcome prediction in MM.

Clinical Relevance of Multicolour Flow Cytometry in Plasma Cell Disorders

Multicolor flow cytometric (MFC) immunophenotyping is one of the basic test that is needed in the evaluation of hematolymphoid malignancies. Previously, there has been some reluctance in the use of MFC in plasma cell disorders (PCD). It was mainly due tolack of standardization, inadequate experience and detection of the lower number of plasma cells by MFC as compared to morphology. However, MFC has gone through many technological advancements in the last few years and a wide variety of reagents are now commercially available which worldwide allowed the establishment of standardized sensitive MFC-based immunophenotypic assay for PCD. Various studies have proven that MFC has a high clinical relevance in the diagnosis and risk stratification of multiple myeloma, its precursor conditions and other PCDs. Moreover, recent studies have shown that MFC is a highly sensitive and reliable technique for the monitoring of clinical response in the era of novel therapies. In this review, we have discussed the various applications of MFC in the management of PCD and their clinical relevance.

International Myeloma Working Group consensus criteria for response and minimal residual disease assessment in multiple myeloma

Treatment of multiple myeloma has substantially changed over the past decade with the introduction of several classes of new effective drugs that have greatly improved the rates and depth of response. Response criteria in multiple myeloma were developed to use serum and urine assessment of monoclonal proteins and bone marrow assessment (which is relatively insensitive). Given the high rates of complete response seen in patients with multiple myeloma with new treatment approaches, new response categories need to be defined that can identify responses that are deeper than those conventionally defined as complete response. Recent attempts have focused on the identification of residual tumour cells in the bone marrow using flow cytometry or gene sequencing. Furthermore, sensitive imaging techniques can be used to detect the presence of residual disease outside of the bone marrow. Combining these new methods, the International Myeloma Working Group has defined new response categories of minimal residual disease negativity, with or without imaging-based absence of extramedullary disease, to allow uniform reporting within and outside clinical trials. In this Review, we clarify several aspects of disease response assessment, along with endpoints for clinical trials, and highlight future directions for disease response assessments.

Role of Flow Cytometry in the Diagnosis and Prognosis of Plasma Cell Myeloma

This article provides an overview of the role of flow cytometry in the diagnosis and follow-up of plasma cell myeloma. A brief introduction to the general immunophenotypic features of normal and myeloma plasma cells is provided, followed by a discussion of technical issues as they relate to the application of flow cytometry in this entity. The prognostic and therapeutic utility of flow cytometric immunophenotyping in myeloma is also analyzed, with an emphasis on the growing role of minimal residual analysis as potential biomarker for evaluating treatment efficacy and for tailoring risk-adapted treatment, in prospective clinical trials.

Bone marrow B lymphocytes in multiple myeloma and MGUS: Focus on distribution of naïve cells and memory subsets

BACKGROUND/AIMS

Multiple myeloma (MM) is caused by proliferation of clonal plasma cells (cPCs) in bone marrow (BM), associated with numerical and functional defects in immune subsets. An impairment of B cell compartment is involved in onset/progression of the disease.

METHODS

By flow cytometry, we studied distribution of naïve/transitional (IgD(+)CD27(-)), memory unswitched (IgD(+)CD27(+)), memory switched (IgD(-)CD27(+)) and double negative (DN) (IgD(-)CD27(-)) B lymphocytes in BM of control subjects, and responding and relapsing patients.

RESULTS

We observed an increased percentage of IgD(+)CD27(+) B cells in healthy controls vs responding patients (p<0.05). Treated non complete responders exhibited an expanded DN compartment vs stringent complete responders (p=0.011); in turn IgD(+)CD27(-) subpopulation was larger in stringent complete responders vs other responding patients (p=0.006). None of the studied B cell subsets showed clonal restriction. Correlation analysis revealed negative correlations between naïve/transitional and DN B cells in all groups, except in newly diagnosed subjects.

CONCLUSIONS

This may be considered a feasible start point to explore the importance of B cells in the immunosuppressive MM BM microenvironment, correlating these findings with immunosenescence and therapy related increased risk of infection. Moreover, we propose a possible role of naïve/transitional and DN B cells as predictive markers in treated patients.

Polychromatic flow cytometry is more sensitive than microscopy in detecting small monoclonal plasma cell populations

BACKGROUND

There is an emerging role for flow cytometry (FC) in the assessment of small populations of plasma cells (PC). However, FC's utility has been questioned due to consistent underestimation of the percentage of PC compared to microscopy.

METHODS

A retrospective study was performed on bone marrow samples analysed by 8-colour FC. Plasma cell populations were classified as polyclonal or monoclonal based on FC analysis. FC findings were compared with microscopy of aspirates, histology and immunohistochemistry of trephine biopsies, and immunofixation (IFX) of serum and/or urine.

RESULTS

FC underestimated PC compared to aspirate and trephine microscopy. The 10% diagnostic cutoff for MM on aspirate microscopy corresponded to a 3.5% cutoff on FC. Abnormal plasma cell morphology by aspirate microscopy and clonality by FC correlated in 229 of 294 cases (78%). However, in 50 cases, FC demonstrated a monoclonal population but microscopy reported no abnormality. In 15 cases, abnormalities were reported by microscopy but not by FC. Clonality assessment by trephine microscopy and FC agreed in 251/280 cases (90%), but all 29 discordant cases were monoclonal by FC and not monoclonal by microscopy. These cases had fewer PC and proportionally more polyclonal PC, and when IFX detected a paraprotein, it had the same light chain as in the PC determined by FC.

CONCLUSIONS

FC was more sensitive in detecting monoclonal populations that were small or accompanied by polyclonal PC. This study supports the inclusion of FC in the evaluation of PC, especially in the assessment of small populations. © 2016 International Clinical Cytometry Society.

The Shreveport Myeloma Experience: Survival, Risk Factors and Other Malignancies in the Age of Stem Cell Transplantation

BACKGROUND

The overall prognosis of multiple myeloma has improved significantly over the last 15 years. We wondered whether the overall improvement would also be seen in unselected patients in an academic center in Northwest Louisiana with a high proportion of minority patients, and if second malignant neoplasms are relevant for our patients.

MATERIALS AND METHODS

Between 1998 and 2009, 215 patients were treated for multiple myeloma at our center and had complete follow-up until May 2013.

RESULTS

The mean survival of patients with multiple myeloma increased from 3.25 to 5.34 years, which is comparable to patients treated at larger centers. No prognostic difference was observed in the subgroups of myeloma patients. Among 215 patients followed for the development of secondary cancers, 16 already had a preexisting or concomitant malignancy (7.4%) and 10 developed secondary cancers. Our data indicate a significant background of histologically unrelated cancers and a cumulative incidence of new cancers of about 20% after 10 years of follow-up. Based on SEER data, preexisting or secondary cancers were not statistically increased in our population.

CONCLUSIONS

The use of autologous transplantation and the introduction of new agents resulted in a significant improvement in the prognosis of multiple myeloma. Other cancers are not statistically increased before or after multiple myeloma is diagnosed and are not prognostically relevant.

Utility of CD54, CD229, and CD319 for the identification of plasma cells in patients with clonal plasma cell diseases

BACKGROUND

Multiparameter flow cytometry (MFC) identification and characterization of plasma cells (PCs) is a useful tool to support diagnosis, prognostication, and monitoring of PC diseases (PCD). Currently, the number of MFC markers suited for the identification of PC remains limited. Moreover, antibody therapies against PC-associated markers further compromise the utility of the most widely used reagents (e.g., CD38). Despite markers other than CD38 and CD138 are recognized as potentially useful PC-identification markers, no study has comparatively evaluated their performance in combination with CD38 and CD138. Here we compared the utility of CD229, CD54, and CD319 for the identification of normal and aberrant PCs.

METHODS

Bone marrow (BM) samples from 5 healthy controls, two noninfiltrated nonHodgkin lymphoma cases and 46 PCD patients plus 3 extraosseous plasmocytomas, and normal peripheral blood (PB) specimens, were studied.

RESULTS

Our results showed adequate performance of all three markers once combined with CD38. In contrast, when combined with CD138 for the identification of PC, only CD229 provided a good discrimination between PCs and all other cells for all BM and PB samples analyzed; in contrast, CD54 and CD319 showed limited utility for the identification of PCs, mainly because of significant overlap of the staining for these two markers on PCs and other myeloid cells in the sample.

CONCLUSIONS

From the three markers evaluated, CD229 may be considered as the most reliable marker to replace CD38 or CD138 for the identification of PCs in patients undergoing anti-CD38 or anti-CD138 therapy, until a better alternative is available.

Flow cytometry in immunoglobulin light chain amyloidosis: Short review

Flow cytometry (FCM) has found its application in clinical diagnosis and evaluation of monoclonal gammopathies (MG). Although, research has been mainly focused on multiple myeloma (MM), nowadays FCM becomes to be potential tool in the field of AL amyloidosis. Clonal plasma cells identification and specific phenotype profile detection is important for diagnosis, monitoring and prognosis of AL amyloidosis. Therefore, FCM could be a perspective method for study not only MM but also AL amyloidosis. This review provides an overview and possibilities of FCM application in AL amyloidosis.

Correlation between CD117+ myeloma plasma cells and hematopoietic progenitor cells in different categories of patients

Background

Multiple myeloma (MM) is a neoplastic disorder of plasma cells interesting mainly the elderly. MM remains an incurable disease, mostly because of the strong interplay between clonal plasma cells (cPCs) and bone marrow (BM) microenvironment. Multiparameter flow cytometry (MFC) allows the simultaneous study of the cPC immunophenotype and alterations involving other cells in BM, but rarely these data are interpreted as connected. One exception to this habit are previous studies about relationship between CD117 cPC positivity and hematopoietic progenitor cell (HPC) distribution in newly diagnosed patients. Thus we were interested in verifying the distribution of BM CD34+ HPCs in healthy controls, and monoclonal gammopathy of undetermined significance (MGUS) patients and various categories of responding/relapsing MM subjects divided according to CD117 positivity.

Results

Our data completely agree with precedent reports as regards untreated patients. In the group with progression of disease, CD117- patients exhibited a lower CD34 + CD19-/CD34 + CD19+ ratio vs CD117+ subjects. Among CD117- cases, newly diagnosed patients exhibited differences in distribution of HPCs vs responding myeloma subjects and patients with progressive disease. These differences reached statistical significance comparing CD117- newly diagnosed with CD117- responding cases, as reflected by CD34 + CD19-/CD34 + CD19+ ratio. In turn, no differences emerged comparing CD117+ treated and untreated patients.

Conclusions

We demonstrate that administration of treatment and depth of reached response/presence of relapse imply a distinct regulation in distribution of CD34+ HPC subsets in CD117- and CD117+ patients. These differences become evident comparing untreated and treated CD117- patients, but they are impossible to detect in CD117+ cases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12979-015-0032-1) contains supplementary material, which is available to authorized users.

Plasma cell morphology in multiple myeloma and related disorders

Normal and reactive plasma cells (PC) are easy to ascertain on human bone marrow films, due to their small mature-appearing nucleus and large cytoplasm, the latter usually deep blue after Giemsa staining. Cytoplasm is filled with long strands of rough endoplasmic reticulum and one large Golgi apparatus (paranuclear hof), demonstrating that PC are dedicated mainly to protein synthesis and excretion (immunoglobulin). Deregulation of the genome may induce clonal expansion of one PC that will lead to immunoglobulin overproduction and eventually to one among the so-called PC neoplasms. In multiple myeloma (MM), the number of PC is over 10% in most patients studied. Changes in the morphology of myeloma PC may be inconspicuous as compared to normal PC (30-50% patients). In other instances PC show one or several morphological changes. One is related to low amount of cytoplasm, defining lymphoplasmacytoid myeloma (10-15% patients). In other cases (40-50% patients), named immature myeloma cases, nuclear-cytoplasmic asynchrony is observed: presence of one nucleolus, finely dispersed chromatin and/or irregular nuclear contour contrast with a still large and blue (mature) cytoplasm. A peculiar morphological change, corresponding to the presence of very immature PC named plasmablasts, is observed in 10-15% cases. Several prognostic morphological classifications have been published, as mature myeloma is related to favorable outcome and immature myeloma, peculiarly plasmablastic myeloma, is related to dismal prognosis. However, such classifications are no longer included in current prognostic schemes. Changes related to the nucleus are very rare in monoclonal gammopathy of unknown significance (MGUS). In contrast, anomalies related to the cytoplasm of PC, including color (flaming cells), round inclusions (Mott cells, Russell bodies), Auer rod-like or crystalline inclusions, are reported in myeloma cases as well as in MGUS and at times in reactive disorders. They do not correspond to malignant changes of PC but are related to abnormal synthesis, trafficking, or excretion of the immunoglobulin that is stored in excess within the cytoplasm. Occurrence of crystalline inclusions within PC may be the first anomaly leading to the diagnosis of adult Fanconi syndrome. After a historical perspective, the authors report on the various morphological aspects of PC that may occur in multiple myeloma and related disorders, and discuss about their clinical and pathophysiological significance. Today, morphological identification and accurate determination of % PC within bone marrow remain ancillary criteria for the diagnosis of MM and help for the diagnosis of rare renal disorders.

Dilemmas in treating smoldering multiple myeloma

Novel therapies hold promise for high-risk smoldering multiple myeloma (SMM). Recent studies suggest that modern combination approaches can be options for high-risk SMM to obtain deep molecular responses with favorable toxicity profiles. Although pioneering treatment trials based on small numbers of patients suggest progression-free and overall survival benefits, application of the data to real-life practice remains to be validated. Therapeutic modulation of disease tempo, disease burden, clonal evolution, and tumor microenvironment in SMM remains to be understood and calls for reliable biomarkers reflective of disease biology. Here, we review studies that open a new management platform for SMM, address ongoing dilemmas in practice and under investigation, and highlight emerging scientific questions in the era of SMM treatment.

Neoplastic plasma cell aberrant antigen expression patterns and their association with genetic abnormalities

Little is known about aberrant antigen expression patterns and their association with cytogenetic aberrations in multiple myeloma (MM). We examined the correlation between flow cytometry and florescence in situ hybridization (FISH) in 167 marrow specimens with MM. Gene expression profiling of CD56, CD117, CD52 and CD20 mRNA in plasma cells (PCs) from patients treated on Total Therapy 2 and Total Therapy 3 trials were also evaluated. Higher expression of CD56 and CD117 was associated with hyperdiploidy. High CD52 mRNA expression was associated with c-MAF and FGFR3 subgroups. Higher expression of CD56 mRNA, but lower Kit expression, were noted in association with FGFR3. In contrast, the c-MAF subgroup showed high Kit expression but lacked NCAM mRNA expression. CKS1B amplification showed positive correlation with CD52 (p=0.0065) but negative correlation with CD20 (p=0.0207). These findings indicate that phenotypic differences in MM are associated with distinct genetic subgroups, which potentially has important diagnostic and prognostic value.

Immunophenotype of normal and myelomatous plasma-cell subsets

Plasma cells (PCs) are essentially characterized by the co-expression of CD138 and CD38, which allows their identification in flow cytometry in bone marrow (BM), peripheral blood, or cell suspensions from tissues. These terminally differentiated B-cells may lose the expression of surface CD19 and that of CD20 while retaining CD27. When malignant, they can gain a number of other markers such as CD28, CD33, CD56, or CD117 and lose CD27. Moreover, since each PC is only able to produce a single type of immunoglobulins (Igs), they display isotypic restriction and clonal malignant PCs can be further characterized by their homogeneous expression of either kappa or lambda light chains. In multiple myeloma (MM), such PC clones produce the Ig identified in plasma as an abnormal peak. In the BM where they essentially accumulate, these PCs may however display various immunophenotypes. The latter were explored in a two-way approach. Firstly, the various subsets delineated by the selective or common expression of CD19 together with combined CD56/CD28 were explored in normal and MM BM. Then, other aberrant markers’ expression was investigated, i.e., CD20, CD27, CD33, CD56, CD117. These data were compared to literature information. They underline the vast heterogeneity of MM PCs possibly accounting for the various answers to therapy of MM patients.

Immunophenotypic characterization and quantification of neoplastic bone marrow plasma cells by multiparametric flow cytometry and its clinical significance in Korean myeloma patients

Multiparametric flow cytometry (MFC) allows discrimination between normal and neoplastic plasma cells (NeoPCs) within the bone marrow plasma cell (BMPC) compartment. This study sought to characterize immunophenotypes and quantitate the proportion of NeoPCs in BMPCs to diagnose plasma cell myeoma (PCM) and evaluate the prognostic impact of this method. We analyzed the MFC data of the bone marrow aspirates of 76 patients with PCM and 33 patients with reactive plasmacytosis. MFC analysis was performed using three combinations: CD38/CD138/-/CD45; CD56/CD20/CD138/CD19; and CD27/CD28/CD138/CD117. The plasma cells of patients with reactive plasmacytosis demonstrated normal immunophenotypic patterns. Aberrant marker expression was observed in NeoPCs, with negative CD19 expression observed in 100% of cases, CD56+ in 73.7%, CD117+ in 15.2%, CD27- in 10.5%, CD20+ in 9.2%, and CD28+ in 1.3%. In PCM patients, more than 20% of NeoPCs/BMPCs were significantly associated with factors suggestive of poor clinical outcomes. Patients who were CD27- or CD56+/CD27-, demonstrated shorter overall survival than patients of other CD56/CD27 combinations. Our results support the clinical value of immunophenotyping and quantifying NeoPCs in PCM patients. This strategy could help to reveal poor prognostic categories and delineate surrogate markers for risk stratification in PCM patients.

Novel human multiple myeloma cell line UHKT-893

We established and characterized a new IL-6 dependent multiple myeloma (MM) cell line UHKT-893 from the bone marrow of a relapsed 57-year-old woman.

RESULTS

Using nephelometry, cells with plasma cell phenotype and morphology were found to secrete IgG and free kappa (κ)-light chain of immunoglobulin. κ-Light chain was also recognized intracellularly by flow cytometry and by mass spectrometry. VH4-39 region of IgVH genes was rearranged and somatically hypermutated. Cytogenetic analysis of cells revealed new chromosome abnormalities in all breakpoints unique in both MM patients and cell lines - t(1;6), t(1;11), t(5;15), t(5;21), +der(11;15) and der(16). IL-6 independent subline UHKT-893a was established by adaptation to descending IL-6 concentration, while the original cell line keeps on maintaining its IL-6 dependency.

CONCLUSION

The cell line provides a suitable material for cellular and molecular studies of tumor abnormalities, with potentially unique mutagenic features of myeloma disease. It may be utilized for human hybridoma construction and vaccine development. Both IL-6 dependent and independent cell clones represent an important model for studies of myeloma cell growth and resistance emerging during targeted therapy.

Simplified flow cytometric immunophenotyping panel for multiple myeloma, CD56/CD19/CD138(CD38)/CD45, to differentiate neoplastic myeloma cells from reactive plasma cells

Background

Flow cytometric immunophenotyping has been used to identify neoplastic plasma cell populations in patients with multiple myeloma (MM). Previous reports have described the use of several antigens, including CD38, CD138, CD56, CD117, CD52, CD19 and CD45, to distinguish distinct populations of plasma cells. The aim of this study was to evaluate a simplified immunophenotyping panel for MM analysis.

Methods

A total of 70 patients were enrolled in the study, 62 of which were newly diagnosed with MM (untreated), whereas the remaining 8 were undergoing bone marrow assessment as part of follow-up after treatment (treated). Treated cases included 3 patients with relapse and 5 patients with persistence of MM. Multiparametric flow cytometric immunophenotyping was performed using monoclonal antibodies against CD56, CD19, CD138 (CD38), and CD45.

Results

In differential counts, plasma cells in bone marrow (BM) accounted for 3.6-93.2% of the total nucleated cell count. The positive expression rates of CD56, CD19, CD138, and CD45 in neoplastic myeloma cells were 83.9%, 0%, 98.4%, and 37.1%, respectively, among the 62 untreated cases, and 75.0%, 0%, 87.5%, and 37.5%, respectively, among the 8 treated cases. CD19 expression of neoplastic plasma cells was negative in both untreated and treated cases.

Conclusion

The simplified immunophenotyping panel, CD56/CD19/CD138(CD38)/CD45, is useful for distinguishing neoplastic myeloma cells from reactive plasma cells in clinical practice. In addition, CD19 represents the most valuable antigen for identifying neoplastic myeloma cells in patients with MM.

CD200 expression in plasma cells of nonmyeloma immunoproliferative disorders: clinicopathologic features and comparison with plasma cell myeloma

The majority of plasma cell myelomas (PCMs) are positive for CD200, a membrane protein with immunosuppressive function. There are no flow cytometry data in the literature on plasma cell CD200 expression in other immunoproliferative disorders. Therefore we used flow cytometry to study the expression of CD200 on plasma cells in diagnostic bone marrow aspirates from 61 patients with monoclonal gammopathy of undetermined significance (MGUS) and 10 patients with lymphoplasmacytic lymphoma (LPL). For comparison, we evaluated CD200 expression in 74 PCM bone marrow biopsies. Thirty-three (54.1%) of 61 MGUS cases and 2 (20.0%) of 10 LPL cases were CD200+. Comparative clinicopathologic parameters for MGUS cases, based on CD200 expression status, showed no differences between the 2 groups. The proportion of CD200+ PCMs (73.0%) in our series was significantly higher than that of CD200+ MGUS (P = .030) and CD200+ LPL (P = .002) cases.