Multi-Parameter Flow Cytometry(FC) Can Detect Proliferating Myeloma Cells After Treatment: Implications for Targeting the Myeloma Proliferative Component

Abstract Abstract 4995 Background: Multiple myeloma results from an accumulation of monoclonal nonproliferating plasma cells arising from a small subpopulation of proliferating myeloma cells. In an effort to optimize detection of the human myeloma cell growth fraction and obviate the need for slide review, a novel FC strategy was developed combining elements of light chain restriction, surface antigen expression, and ploidy analysis. Methods: Bone marrow cells from 41 patients with plasma cell proliferative disorders were lysed with ACK and resuspended in 3% BSA. Cells were stained using a 6-color assay with anti-CD45, anti-CD38, anti-CD138, and anti-CD19. Cells were washed and 100 ul Caltag solution A was added for 15 min. Cells were washed and 100 ul of Caltag solution B, anti-kappa and anti-lambda were added for 10 min. Cells were washed and 100 ul PBS and 3 ul RNAse are added for 15 min. Cells were washed and 400 ul of a 1:1000 solution of 3uM DAPI in Tris 0.1% NP-40 was added. Cells were incubated at 4°C for 45 minutes before running on a FACSCanto instrument for ploidy determination. All patients were analyzed both by flow cytometry and the slide based plasma cell labeling index. Results: Forty-one patients were studied; 34 demonstrated a proliferative fraction and 7 had too few plasma cells for analysis after therapy. Of the 34 patients, 6 had MGUS/SMM, 5 newly diagnosed MM, 7 amyloid, and 16 were treated MM. The mean percent proliferating cells were 1.1% (range 0 – 8.6%) with PCLI and 1.4% (range 0.1 – 12.7%) by flow. The correlation between PCLI and flow gave a RSquare value of 0.54. Twelve patients with a PCLI of 0% had a flow proliferation between 0.1 – 1.4% (mean 0.49%). Treated patients received lenalidomide, dexamethasone, bortezomib, and/or autologous transplantation. All 16 treated myeloma patients with adequate plasma cells had a flow proliferation between 0.2 – 12.7% (mean 2.2%). Conclusion: Flow cytometry offers a useful way to detect the proliferative myeloma component at diagnosis and after treatment. The continued presence of proliferating myeloma cells after treatment may explain why most patients relapse and offers another important marker to monitor and cell population to target in patients with active disease. Disclosures: Kumar: Celgene: Consultancy, Research Funding; Millennium: Research Funding; Merck: Consultancy, Research Funding; Novartis: Research Funding; Genzyme: Consultancy, Research Funding; Cephalon: Research Funding.

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The Proliferative Potential of Myeloma Plasma Cells Manifest in the SCID-hu Host

Blood ◽

10.1182/blood.v94.10.3576.422k01_3576_3582 ◽

1999 ◽

Vol 94 (10) ◽

pp. 3576-3582 ◽

Cited By ~ 125

Author(s):

Shmuel Yaccoby ◽

Joshua Epstein

Keyword(s):

Bone Marrow ◽

Plasma Cell ◽

Blood Cells ◽

Plasma Cells ◽

Bone Marrow Cells ◽

Severe Combined Immunodeficiency ◽

Proliferative Potential ◽

Myeloma Cells ◽

Host System ◽

Human Bones

The low proliferative activity of myeloma plasma cells prompted the notion that the clonotypic B cells that exist in the blood and bone marrow of all myeloma patients contain the proliferative myeloma cells (stem cell). We have exploited our severe combined immunodeficiency (SCID)-hu host system for primary myeloma to investigate whether myeloma plasma cells are capable of sustained proliferation. Purified CD38++CD45− plasma cells consistently grew and produced myeloma and its manifestations in SCID-hu hosts (8 of 9 experiments). In contrast, the plasma cell-depleted bone marrow cells from 6 patients did not grow or produce myeloma in SCID-hu hosts. Similarly, whereas plasma-cell containing blood cells from 4 patients grew and produced myeloma in hosts, neither the PC-depleted blood cells from 3 of the patients nor a blood specimen that did not contain plasma cells grew in SCID-hu hosts, regardless of their CD19-expressing cell contents. Also, in hosts injected with blood cells, although the myeloma cells were able to disseminate through the murine host system, they were only able to grow in the human bones within a human microenvironment and were not detectable in the murine blood or other organs. Interestingly, the circulating plasma cells appear to grow more avidly in the SCID-hu hosts than their bone marrow counterparts, suggesting that they represent a subpopulation of the plasma cells in the bone marrow. Although our studies clearly demonstrate the proliferative potential of myeloma plasma cells, they are suggestive, not conclusive, as to the existence of a preplasmacytic myeloma progenitor cell.

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A Novel Role For Histone Deacetylase 11 (HDAC11) In Plasma Cell Differentation and Survival

Blood ◽

10.1182/blood.v122.21.1907.1907 ◽

2013 ◽

Vol 122 (21) ◽

pp. 1907-1907

Author(s):

Eva Sahakian ◽

Jason B. Brayer ◽

John Powers ◽

Mark Meads ◽

Allison Distler ◽

...

Keyword(s):

Gene Expression ◽

Multiple Myeloma ◽

Bone Marrow ◽

B Cells ◽

Plasma Cell ◽

Research Funding ◽

Plasma Cells ◽

Myeloma Cells ◽

Peripheral Blood Plasma

Abstract The role of HDACs in cellular biology, initially limited to their effects upon histones, is now appreciated to encompass more complex regulatory functions that are dependent on their tissue expression, cellular compartment distribution, and the stage of cellular differentiation. Recently, our group has demonstrated that the newest member of the HDAC family of enzymes, HDAC11, is an important regulator of IL-10 gene expression in myeloid cells (Villagra A Nat Immunol. 2009). The role of this specific HDAC in B-cell development and differentiation is however unknown. To answer this question, we have utilized a HDAC11 promoter-driven eGFP reporter transgenic mice (TgHDAC11-eGFP) which allows the monitoring of the dynamic changes in HDAC11 gene expression/promoter activity in B-cells at different maturation stages (Heinz, N Nat. Rev. Neuroscience 2001). First, common lymphoid progenitors are devoid of HDAC11 transcriptional activation as indicated by eGFP expression. In the bone marrow, expression of eGFP moderately increases in Pro-B-cells and transitions to the Pre- and Immature B-cells respectively. Expression of eGFP doubles in the B-1 stage of differentiation in the periphery. Of note, examination of both the bone marrow and peripheral blood plasma cell compartment demonstrated increased expression of eGFP/HDAC11 mRNA at the steady-state. These results were confirmed in plasma cells isolated from normal human subjects in which HDAC11 mRNA expression was demonstrated. Strikingly, analysis of primary human multiple myeloma cells demonstrated a significantly higher HDAC11 mRNA expression in malignant cells as compared to normal plasma cells. Similar results were observed in 4/5 myeloma cell lines suggesting that perhaps HDAC11 expression might provide survival advantage to malignant plasma cells. Support to this hypothesis was further provided by studies in HDAC11KO mice in which we observed a 50% decrease in plasma cells in both the bone marrow and peripheral blood plasma cell compartments relative to wild-type mice. Taken together, we have unveiled a previously unknown role for HDAC11 in plasma cell differentiation and survival. The additional demonstration that HDAC11 is overexpressed in primary human myeloma cells provide the framework for specifically targeting this HDAC in multiple myeloma. Disclosures: Alsina: Millennium: Membership on an entity’s Board of Directors or advisory committees, Research Funding. Baz:Celgene Corporation: Research Funding; Millenium: Research Funding; Bristol Myers Squibb: Research Funding; Novartis: Research Funding; Karyopharm: Research Funding; Sanofi: Research Funding.

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The growth fraction of human myeloma cells

Blood ◽

10.1182/blood.v57.2.333.bloodjournal572333 ◽

1981 ◽

Vol 57 (2) ◽

pp. 333-338 ◽

Cited By ~ 3

Author(s):

B Drewinko ◽

R Alexanian ◽

H Boyer ◽

B Barlogie ◽

SI Rubinow

Keyword(s):

Multiple Myeloma ◽

Growth Kinetics ◽

Plasma Cells ◽

Tritiated Thymidine ◽

High Growth ◽

Growth Fraction ◽

Proliferating Cells ◽

Myeloma Cells ◽

Tumor Mass ◽

Kinetics Of

Greater reductions of tumor load in patients with multiple myeloma may result from therapeutic strategies that are based on a better knowledge of growth kinetics. We have previously shown that the labeling index of myeloma cells remains unchanged when tumor mass is reduced and that the cells of relapsing patients have differnt biologic properties than the cells present before melphalan-prednisone therapy. This study investigated the growth fraction (GF) of myeloma cells at various disease stages using continuous i.v. infusions of tritiated thymidine. We studied 17 patients on 22 occasions (4 untreated, 2 unresponsive, 6 in remission, and 10 in relapse). All untreated an unresponsive patients and 5 of 6 patients in remission had a GF of less than 4%. GF was defined in these studies as the maximum percentage of labeled plasma cells exposed continuously to tritiated thymidine. Relapsing patients, with the most rapid tumor doubling times, had GF ranging from 14% to 83%. The plasma cell transit time through the proliferative compartment for all of the relapsing patients ranged from 6.6 to 11.9 days and the calculated intrinsic cell loss ranged from 50% to 86%. These findings support our model for the growth kinetics of multiple myeloma that assumes that the entire tumor mass issues from a small proportion of proliferating cells and that the growth kinetics of myeloma cells in relapsing patterns differ from those in untreated and unresponsive patients. Therapeutic trials with cycle-active agents need further investigation in selected relapsing patients who are likely to have a high growth fraction.

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Myeloma Exosomes Prime the Microenvironment to Support Survival and Growth of Myeloma Cells

Blood ◽

10.1182/blood.v128.22.2067.2067 ◽

2016 ◽

Vol 128 (22) ◽

pp. 2067-2067 ◽

Cited By ~ 2

Author(s):

Bangzheng Chen ◽

Sharmin Khan ◽

Bozena M Laska ◽

Gareth J Morgan ◽

Shmuel Yaccoby ◽

...

Keyword(s):

Bone Marrow ◽

Research Funding ◽

Healthy Donor ◽

Plasma Cells ◽

Bone Marrow Cells ◽

Bone Marrow Microenvironment ◽

Control Group ◽

Myeloma Cells ◽

Expression Of Genes ◽

Survival And Growth

Abstract Introduction Myeloma bone marrow serum primes healthy donor (HD) bone marrow cells to support the survival and growth of myeloma plasma cells (MMPC) in co-culture. Following interaction with the MMPC, the phenotype of the HD bone marrow stroma changes and the expression of immune regulatory factors is increased while expression of genes associated with osteoblastogenesis and WNT signaling is suppressed. The aim of this study was to determine whether exosomes in the myeloma bone marrow serum have a role in priming the microenvironment. Methods Serum was separated from clotted bone marrow aspirates from myeloma patients obtained during scheduled clinic visits, and from healthy donors of similar ages. Exosomes were prepared from 1-2 ml of serum using Invitrogen's Total Exosome Isolation kit according to manufacturer's instruction. Exosomes were 30-130 nm in diameter as determined by Dynamic Light Scatter on a Brookhaven Instruments Corp. ZetaPlus Particle Sizing Software, and visualized by scanning electron microscopy. Small RNA (≤200 nucleotides) was isolated using Qiagen's miRNeasy kits, quality and quantity assessed with Qubit 2. 96 microRNAs (miRs) were analyzed by qRT-PCR on Fluidigm's BioMark platform using 96x96 multiplex chips and normalized to spiked in C. elegance miR mimetic. Primary CD138-expressing cells were isolated from EDTA-anticoagulated bone marrow aspirates. Luciferase-expressing stroma-dependent myeloma cells were described previously (Bam, BMC Cancer 2015:864). Healthy donor mesenchymal stem cells (MSC) were prepared from bone particles obtained during orthopedic surgery, and cultured in a-MEM supplemented with 10% FBS. Primary myeloma cells or luciferase-expressing stroma dependent myeloma cells were added to wells containing monolayers of MSC in α-MEM supplemented with 10% FBS in 96 well culture plates. For each experiment 3 conditions were used: A control group, a group to which 10% myeloma bone marrow serum was added, and a third group to which exosomes isolated from a matching bone marrow serum aliquot were added. The number of primary MMPC dictated that these experiments were carried out in duplicates, while the stroma dependent cells were plated in 5 replicates. Viable primary cells counts or luciferase bioluminescence were evaluated after 4 days of co-culture. Results Exosomes supported survival and growth of primary MMPC in co-culture with HD MSC, but had no effect on MMPC cultured alone, indicating that the myeloma bone marrow serum exosomes prime the MSC to support the MMPC. Exosomes from 5 of the 7 patients supported growth of stroma-dependent myeloma cells co-cultured with HD MSC. In a representative experiment, the bioluminescence of stroma-dependent myeloma cells was 46% higher in co-cultures supplemented with bone marrow serum (p=7.3E-6) and 23% higher (p=2.0E-6) when exosomes were used. The effect was reproduced when primary MMPC were used: in a representative experiment, the number of primary MPC recovered from the co-cultures supplemented with bone marrow serum was 41% higher, and when supplemented with exosomes 28% higher than in controls. Primary MMPC did not survive in the absence of MSCs and bone marrow serum or exosomes did not enhance their survival. Conclusions Exosome from bone marrow serum of myeloma patients prime the bone marrow microenvironment to support survival and growth of primary MMPC. Bone marrow serum is more effective, indicating that other factors in the serum are also important. The differences in microRNA contents between healthy donor and myeloma exosomes may provide an insight of the regulatory mechanisms molding the myeloma bone marrow microenvironment. Disclosures Morgan: Univ of AR for Medical Sciences: Employment; Celgene: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; Bristol Meyers: Consultancy, Honoraria; Janssen: Research Funding.

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VS38 Identifies Myeloma Cells With Dim CD38 Expression and Plasma Cells Following Daratumumab Therapy, Which Interferes With CD38 Detection for 4 to 6 Months

American Journal of Clinical Pathology ◽

10.1093/ajcp/aqz153 ◽

2019 ◽

Cited By ~ 1

Author(s):

Elizabeth L Courville ◽

Sophia Yohe ◽

Paula Shivers ◽

Michael A Linden

Keyword(s):

Flow Cytometry ◽

Plasma Cell ◽

Fluorescence Intensity ◽

Plasma Cells ◽

Myeloma Cells ◽

Flow Cytometry Data ◽

Cd38 Expression ◽

Cell Percentage ◽

Significant Difference ◽

Institutional Experience

Abstract Objectives We report our institutional experience using VS38 to evaluate plasma cells by flow cytometry. Methods Flow cytometry data were reanalyzed to compare plasma cell percentages between the standard panel and VS38 panel. Natural killer (NK) and plasma cell CD38 median fluorescence intensity (MFI) values were calculated. Results Our cohort included 63 specimens from 38 patients. Twenty-six had received daratumumab (monoclonal anti-CD38 therapy) between less than 1 month and 17 months prior. For NK and plasma cells, CD38 MFI values were suppressed for 0 to 4 months and started to increase 4 to 6 months after last exposure. There was no significant difference in clonal plasma cell percentage calculated by the VS38 and standard panels; however, identification and quantification using the VS38 panel were easier. Conclusions VS38 is a viable alternative to bright CD38 to identify plasma cells and particularly helpful in myeloma cases with dim CD38 and after daratumumab. Daratumumab interference with CD38 identification persists 4 to 6 months after the last exposure.

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Molecular Characterization of Bone Marrow and Peripheral Blood Compartments from Patients with Plasma Cell Leukemia in the Mmrf Commpass Study

Blood ◽

10.1182/blood-2019-130697 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 1782-1782

Author(s):

Sheri Skerget ◽

Austin Christofferson ◽

Sara Nasser ◽

Christophe Legendre ◽

The MMRF CoMMpass Network ◽

...

Keyword(s):

Cell Cycle ◽

Multiple Myeloma ◽

Bone Marrow ◽

Flow Cytometry ◽

Plasma Cell ◽

Peripheral Blood ◽

Research Funding ◽

Plasma Cells ◽

Cell Cycle Control ◽

Cell Leukemia

Plasma cell leukemia (PCL) is rare but represents an aggressive, advanced form of multiple myeloma (MM) where neoplastic plasma cells (PCs) escape the bone marrow (BM) and circulate in the peripheral blood (PB). Traditionally, PCL is defined by the presence of >20% circulating plasma cells (CPCs), however, recent studies have suggested that PCL be redefined as the presence of >5% CPCs. The Multiple Myeloma Research Foundation CoMMpass study (NCT01454297) is a longitudinal, observational clinical study with 1143 newly diagnosed MM patients. BM-derived MM samples were characterized using whole genome (WGS), exome (WES), and RNA (RNAseq) sequencing at diagnosis and each progression event. When >5% CPCs were detected by flow cytometry, PCs were enriched independently from both compartments, and T-cells were selected from the PB as a control for WGS and WES. This substudy within CoMMpass provides the largest, most comprehensively characterized dataset of matched MM and PCL samples to date, which can be leveraged to better understand the molecular drivers of PCL. At diagnosis, 813/1143 CoMMpass patients had flow cytometry data reporting the percent PCs in PB, of which 790 had <5%, 17 had 5-20%, and 6 had >20% CPCs. Survival analyses revealed that patients with 5-20% CPCs (median = 20 months) had poor overall survival (OS) outcomes compared to patients with <5% CPCs (median = 74 months, p < 0.001), and no significant difference in outcome was observed between patients with 5-20% and >20% (median = 38 months) CPCs. Patients with 1-5% CPCs (median = 50 months, HR = 2.45, 95% CI = 1.64 - 3.69, p < 0.001) also exhibited poor OS outcomes compared to patients with <1% CPCs (median = 74 months), suggesting that patients with >1% CPCs are a higher risk population, even if they do not meet the PCL threshold. Using a cutoff of >5% CPCs, 23/813 (2.8%) patients presented with primary PCL (pPCL) at diagnosis. Of these patients, 7 (30%) were hyperdiploid (HRD), of whom 1 had a CCND1 and 1 had a MYC translocation; while 16 (70%) were nonhyperdiploid (NHRD), all of whom had a canonical immunoglobulin translocation (6 CCND1, 5 WHSC1, 3 MAF, 1 MAFA, and 1 MAFB). Of 124 patients with serial sample collections, 5 (4%) patients without pPCL had >5% CPCs at progression, and thus relapsed with secondary PCL (sPCL). Of the 5 sPCL patients, 2 (40%) were NHRD with a CCND1 or MAF translocation; while 3 (60%) were HRD, 1 with a WHSC1 translocation. Median time to diagnosis of sPCL was 22 months (range = 2 - 31 months), and patients with sPCL (median = 22 months) and pPCL (median = 30 months) exhibited poor OS outcomes as compared to MM patients (74 months, p < 0.001). Sequencing data was available for 15 pPCL and 5 sPCL samples. For 12 patients with WES, WGS, and RNAseq performed on their PCL tumor sample, an integrated analysis identified recurrent, complete loss-of-function (LOF) events in only CDKN2C/FAF1, SETD2, and TRAF3. Five pPCL patients had complete LOF of a gene involved in G1/S cell cycle control, including CDKN2C, CDKN2A, CDKN1C, and ATM. These LOF events were not observed in NHRD t(11;14) PCL patients, suggesting that CCND1 overexpression and LOF of genes involved in G1/S cell cycle control may represent independent drivers of PCL. Comparing WES and WGS data between matched MM and PCL tumor samples revealed a high degree of similarity in mutation and copy number profile. However, differential expression analysis performed for 13 patients with RNAseq data comparing their MM and PCL tumors revealed 27 up- and 39 downregulated genes (padj < 0.01, FDR = 0.1) in PCL versus MM. Pathway analysis revealed an enrichment (p < 0.001) for genes involved in adhesion and diapedesis, including upregulation of ITGB2, PF4, and PPBP, and downregulation of CCL8, CXCL12, MMP19, and VCAM1. The most significantly downregulated gene in PCL (log2FC = -6.98) was VCAM1, which plays a role in cell adhesion, and where loss of expression (TPM < 0.01) was observed across all PCL samples. Upregulation of four S100 genes including S100A8, S100A9, S100A12, and S100P, which have been implicated in tumor growth, metastasis, and immune evasion, was also observed in PCL. Interestingly, a S100A9 inhibitor has been developed and may represent a novel treatment option for PCL patients. In summary, PCL was found to be associated with molecular events dysregulating G1/S cell cycle control coupled with subtle changes in transcription that likely occur in a subclonal population of the MM tumor. Disclosures Lonial: Genentech: Consultancy; GSK: Consultancy; BMS: Consultancy; Janssen: Consultancy, Research Funding; Karyopharm: Consultancy; Takeda: Consultancy, Research Funding; Celgene Corporation: Consultancy, Research Funding; Amgen: Consultancy.

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Humoral Immunity and Plasma Cell Changes in Patients Responding to CD19-Specific Chimeric Antigen Receptor (CAR)-Modified T-Cell Adoptive Immunotherapy

Blood ◽

10.1182/blood.v124.21.1110.1110 ◽

2014 ◽

Vol 124 (21) ◽

pp. 1110-1110

Author(s):

Vijay Bhoj ◽

Michael C Milone ◽

Carl H. June ◽

David Porter ◽

Stephan A. Grupp ◽

...

Keyword(s):

Bone Marrow ◽

Flow Cytometry ◽

B Cells ◽

B Cell ◽

Plasma Cell ◽

Humoral Immunity ◽

Research Funding ◽

Plasma Cells ◽

Flow Cytometric ◽

Antibody Titers

Abstract Introduction: T cells engineered to express chimeric antigen receptors (CARs) recognizing CD19 (CART19) can eliminate malignant cells in acute lymphoblastic leukemia (ALL) and chronic lymphocytic leukemia (CLL). We and other groups have shown that persistent tumor eradication by CD19-specific T cell immunotherapy is accompanied by normal B-cell aplasia. It is assumed that responding patients cannot make new antibody responses post-successful CART19 treatment; however, the status of previously established humoral immunity in these patients is currently unknown. Understanding the consequence of successful CART19 therapy on established humoral immunity has implications for both the clinical management of CART19-treated patients as well as the potential application of this therapy to non-malignant diseases such as autoimmunity and transplantation. Methods: We performed a prospective, observational study of adult and pediatric patients with ALL and adults with relapsed/refractory CLL, who were enrolled in clinical trials of CART19 at our institution. Serum antibody titers to previously-generated vaccine or vaccine-related pathogens (Streptococcus pneumoniae, Tetanus toxoid, Hemophilus influenza type-B (HIB), Measles, Mumps, and Rubella) were determined along with a quantitative assessment of B-cell and plasma cell frequencies in blood and bone marrow aspirates. Specimens were collected during pre-established study assessments or additional time points when collected as required for clinical management. Due to the challenges of assessing plasma cells, multiple methods were employed for their quantification in fresh specimens including flow cytometry and immunohistochemistry (IHC). Flow cytometric assessment of plasma cells was performed on freshly obtained marrow samples. Only patients with at least 3 months of B-cell aplasia in the absence of regular intravenous immunoglobulin (IVIg) infusions were included in the study. Results: All patients had no evidence of leukemia or peripheral B cells post-CART19 infusion at the time of this study. Compared to pre-CART19 serum titers, antibodies to S. pneumoniae remained stable or increased in 9 of 12 patients despite lack of circulating B-cells. Antibody titers to Tetanus toxoid were stable or increased in 13 of 14 patients. Anti-HIB levels were stable or increased in 9 of 11 patients and antibodies to Measles, Mumps and Rubella were stable or increased in 12 of 13, 11 of 13, and 12 of 13 patients, respectively. Flow cytometric analysis of bone marrow aspirates after CART19 infusion revealed three patients with persistence of CD38+ CD138+ plasma cells (at 1, 3 and 9 months post infusion, respectively) despite a complete absence of peripheral CD19+ B cells. In 9 patients, CD20 and CD138 IHC analysis of bone marrow core biopsies revealed a decrease in plasma cell (ranges: 1-5% pre-CART19, 0-<1% post-CART19), consistent with our previously published data. Finally, in another subset of patients, neither B cells nor plasma cells were detectable by flow cytometry of aspirate material or IHC of core biopsies collected either pre- or post-CART19 treatment. Conclusions: The stable or increased titers of antibodies to previous vaccines are surprising and may, in part, reflect improved marrow function as a result of leukemia eradication. The demonstration of plasma cells in a subset of patients in the absence of detectable tumor or normal B cells provides strong evidence for the existence of a population of plasma cells that are resistant to lysis by CART19 cells. This is consistent with antibody titers to previously generated vaccine antigens, which remain stable despite effective CART19 treatment. The additional finding of a decrease in CD138+ cells in several patients by IHC suggests that some populations of plasma cells are either targeted directly by CART19 or have a short half-life (e.g. plasmablasts); CD138 is not sufficient to distinguish these populations. Overall, these results indicate that long-lived plasma cells are resistant to CART19, likely due to a loss of CD19 during plasma cell differentiation. Continued analysis of remaining plasma cells in the absence of ongoing B-cell maturation as a result of CART19 persistence may provide important information on turnover rates of these long-lived cells in humans. Disclosures Bhoj: Novartis: Research Funding. Milone:Novartis: Patents & Royalties, Research Funding. June:Novartis: Research Funding, Royalty income Patents & Royalties. Porter:Novartis: Patents & Royalties, Research Funding. Grupp:Novartis: Research Funding. Melenhorst:Novartis: Research Funding. Lacey:Novartis: Research Funding. Mahnke:Novartis: Research Funding.

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The growth fraction of human myeloma cells

Blood ◽

10.1182/blood.v57.2.333.333 ◽

1981 ◽

Vol 57 (2) ◽

pp. 333-338 ◽

Cited By ~ 92

Author(s):

B Drewinko ◽

R Alexanian ◽

H Boyer ◽

B Barlogie ◽

SI Rubinow

Keyword(s):

Multiple Myeloma ◽

Growth Kinetics ◽

Plasma Cells ◽

Tritiated Thymidine ◽

High Growth ◽

Growth Fraction ◽

Proliferating Cells ◽

Myeloma Cells ◽

Tumor Mass ◽

Kinetics Of

Abstract Greater reductions of tumor load in patients with multiple myeloma may result from therapeutic strategies that are based on a better knowledge of growth kinetics. We have previously shown that the labeling index of myeloma cells remains unchanged when tumor mass is reduced and that the cells of relapsing patients have differnt biologic properties than the cells present before melphalan-prednisone therapy. This study investigated the growth fraction (GF) of myeloma cells at various disease stages using continuous i.v. infusions of tritiated thymidine. We studied 17 patients on 22 occasions (4 untreated, 2 unresponsive, 6 in remission, and 10 in relapse). All untreated an unresponsive patients and 5 of 6 patients in remission had a GF of less than 4%. GF was defined in these studies as the maximum percentage of labeled plasma cells exposed continuously to tritiated thymidine. Relapsing patients, with the most rapid tumor doubling times, had GF ranging from 14% to 83%. The plasma cell transit time through the proliferative compartment for all of the relapsing patients ranged from 6.6 to 11.9 days and the calculated intrinsic cell loss ranged from 50% to 86%. These findings support our model for the growth kinetics of multiple myeloma that assumes that the entire tumor mass issues from a small proportion of proliferating cells and that the growth kinetics of myeloma cells in relapsing patterns differ from those in untreated and unresponsive patients. Therapeutic trials with cycle-active agents need further investigation in selected relapsing patients who are likely to have a high growth fraction.

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Eight-Color Flow Cytometry Phenotypic Markers and Disease Progression in Monoclonal Gammopathy of Unknown Significance

Blood ◽

10.1182/blood-2021-148228 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2713-2713

Author(s):

Naveen K Yarlagadda ◽

Meera Mohan ◽

Shebli Atrash ◽

Sravani Gundarlapalli ◽

Shadiqul Hoque ◽

...

Keyword(s):

Flow Cytometry ◽

Disease Progression ◽

Plasma Cell ◽

Research Funding ◽

Plasma Cells ◽

Cell Clone ◽

Clone Size ◽

Color Flow ◽

Unknown Significance ◽

M Spike

Abstract Introduction: Flow cytometric immunophenotyping is considered an indispensable tool for the diagnosis, classification, and monitoring of plasma cell disorders. Herein, we seek to study the clinical significance of expression of phenotype markers in monoclonal gammopathy of unknown significance (MGUS). Methods: We identified a cohort of patients with a diagnosis of MGUS from the institutional myeloma database. Bone marrow (BM) aspirate assessment was performed using 8-color immunophenotypic next-generation flow cytometric (NGF) analysis with a minimum sensitivity of 10 -5 cells at the time of diagnosis or first visit to our institution. BM aspirate samples were immunophenotyped on a FACSCanto II flow cytometer using antibodies (BD) to delineate normal and abnormal plasma cells [CD138 (V-500), CD38 (FITC), CD19 (PE-Cy7), CD45 (V-450), CD27 (PercpCy5.5), CD81 (APC-H-7), CD56 (APC) and CD20 (PE)]. The sensitivity or the Limit of Detection (LOD) for this assay was validated to 20 cells in 2 ×10 6 events (0.001%), and the reproducibility or Lower Limit of Quantitation (LLOQ) is 50 cells in 2 ×10 6 events. Clinical and laboratory variables were also collected. Based on previously published data, expression (CD19, CD45, CD81), and lack of expression (CD56, CD27, CD20) of the above-mentioned surface antigens were analyzed. Additional variables such as IgA isotype, size of M-protein (≥15 g/L), and abnormal free light chain ratio(abnFLR) (defined as <0.1 or >10) were included in regression fitting models. Results: A total of 157 patients with MGUS were included in this analysis. The median age at diagnosis was 60 years (range 24- 84), 84 (53 %) patients were female and 25 (16%) were African American. Overall, IgG Kappa (75/148, 50%) was the most common isotype. Fluorescent-in-situ hybridization (FISH) data were available in 35 patients with t (4:14) and t (14;16) seen in 3 patients each. At a median follow-up of 18.15 years (quantiles 11.35, 33.62), 28 patients experienced disease progression (25 to MM, 2 to Waldenstrom macroglobulinemia, and 1 Smoldering myeloma). The median progression-free survival of this cohort was 17.3 years. Among these, occurrences of the bone lesion (8/28; 28.6%) were the most common pattern of disease progression to MM. This analysis showed lower odds of progression with the expression of CD27 (OR-0.39, 95% CI 0.15-0.99) (figure 1A). Disease progression was more common in patients with an abnormal plasma cell clone size ≥ of 3.1% at diagnosis (60% vs. 12.5%, p=0.0005). An abnormal plasma cell clone of ≥3.1% at diagnosis, was associated with increased odds of progression (OR-10.79, 95% CI 4.02-28.98) and a shorter PFS (12.5 years versus NR, p=0.01) (figure 1B). Serum M-spike ≥1.5 g/dL (OR-3.54;95% 1.30-9.62) and abnFLR (OR-2.30, 95% CI 1.00-5.32) were also associated with a higher odds of progression. However, in this population, the presence of IgA isotype did not increase the odds of MGUS progression. In a stepwise regression model, serum M-spike≥1.5 g/dL, abnFLR, and the lack of expression of CD27 were associated with the risk of disease progression. Conclusion: In addition to previously published risk factors, our cohort shows that the expression of CD27 antigen by eight-color flow cytometry confers a lower risk of disease progression of MGUS. This is consistent with our previous report that CD27 is progressively down-regulated in the transition from normal plasma cells (NPC) to MGUS to MM (Zhan et al, Blood 2006). Furthermore, we show that size of the myeloma clone (≥ 3.1% ) is a possible surrogate marker for disease progression in MGUS. Figure 1: 1A shows forest plot of odds ratios for flow cytometry markers, IgA isotype, size of M protein, abnFLR and plasma cell clone size. 1B shows the Kaplan Meier estimates of PFS for patients stratifies by plasma cell clone size. Figure 1 Figure 1. Disclosures Mohan: Medical College of Wisconsin: Current Employment. Atrash: GSK: Research Funding; AMGEN: Research Funding; Jansen: Research Funding, Speakers Bureau.

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