scholarly journals Inability of a monoclonal anti-light chain antibody to detect clonal plasma cells in a patient with multiple myeloma by multicolor flow cytometry

2012 ◽  
Vol 84B (1) ◽  
pp. 30-32 ◽  
Author(s):  
Jeroen F. van Velzen ◽  
Dorine van den Blink ◽  
Andries C. Bloem
Keyword(s):  
Multiple Myeloma ◽  
Flow Cytometry ◽  
Light Chain ◽  
Plasma Cells ◽  
Multicolor Flow Cytometry ◽  
Light Chain Antibody

Immunoglobulin Heavy/Light Chain Immunoassays for Response Evaluation in Multiple Myeloma: Comparison with Immunofixation, Serum Free Light Chain, and Multicolor Flow- Cytometry

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3366-3366 ◽  
Author(s):  
Yasuhito Suehara ◽  
Keisuke Seike ◽  
Kouta Fukumoto ◽  
Manabu Fujisawa ◽  
Masafumi Fukaya ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Flow Cytometry ◽  
Light Chain ◽  
Conflicts Of Interest ◽  
Free Light Chain ◽  
Multicolor Flow Cytometry ◽  
Serum Free ◽  
Serum Free Light Chain ◽  
Normal Ranges ◽  
Best Response

Abstract BACKGROUND: Monitoring of multiple myeloma (MM) patients is required to assess and determine the treatment response. The serum immunoglobulin (Ig) heavy/light chain immunoassays are a new method that enables separate quantification of the different light chain types of each Ig class, i.e., IgGk, IgGl, IgAk, and IgAl. Although the contribution of these tests to disease evaluation has been assessed, available data are still limited. Here, we compared the serum Ig heavy/light chain immunoassays with the conventional methods for disease evaluation. PATIENTS AND METHODS: Three hundred and three samples were obtained from a total of 101 patients with IgG and IgA type MM recruited at Kameda Medical Center and Kanazawa University Hospital. The median age of the patients was 68 years (range: 44 – 89). The median follow-up was 36 months (range: 2.5 – 189.6). The proportions of patients in International Scoring System (ISS) stages I, II, and III were 25%, 35%, and 40%, respectively. Paraprotein type was IgG in 64 patients (44 Gk, 20 Gl) and IgA in 37 (20 Ak, 17 Al). Samples were taken at various times after treatment and analyzed retrospectively with serum Ig heavy/light chain immunoassays (Hevylite®; Binding Site, Birmingham, UK) on a SPAPLUS® turbidimeter. The heavy/light chain ratio (HLCR) was calculated with the Ig' k (either G or A) as the numerator and compared to normal ranges (IgGk:3.84-12.07g/L; IgGl:1.91-6.74g/L; IgGk/IgGl: 1.12-3.21; IgAk:0.57-2.08g/L; IgAl:0.44-2.04g/L; IgAk/IgAl:0.78-1.94). Results were compared to serum protein electrophoresis (SPEP), immunofixation electrophoresis (IFE), and serum free light chain immunoassays (FLC). HLC-pair suppression was defined as the uninvolved immunoglobulin of the same isotype 50% below the lower limit of the normal range (IgGk, IgGl, IgAk, IgAl). Residual neoplastic plasma cells (MM-PCs) in bone marrow samples were assessed by multicolor flow cytometry (MFC) simultaneously in 140 samples from 64 patients at very good partial response (VGPR), complete response (CR), and stringent CR (sCR). The MFC negativity was defined at a level of < 10-4 MM-PCs. Overall survival (OS) and progression-free survival (PFS) were estimated by the Kaplan–Meier method, and survival was compared using the log rank test. RESULTS: Myeloma responses were assessed serially after induction therapy and were assigned according to international response criteria. Patients' samples at various responses were: sCR, n = 86 (28%); CR, n = 31 (10%); VGPR, n = 116 (38%); and PR, n = 70 (23%). Normal HLCR was obtained at sCR, CR, and VGPR in 73 (85%), 28 (90%), and 69 (59%) cases, respectively. Discordance in the depth of response between standard electrophoretic methods and HLCR was more commonly seen in IgG compared to IgA MM; possibly reflecting the dose dependent half life of IgG immunoglobulins. In the sera from patients who achieved a CR or better, abnormal HLCR and FLC ratio were seen at rates of 12.8% and 26.5%, respectively. Discordance between normalization of HLCR and FLC ratio was seen in 42% of patients with a CR or better; however, a good correlation between normalization of HLCR and FLC ratio was still observed (Fisher's exact test, P = 0.004). Among the 71 sera from patients with a CR or better in which simultaneous MFC data were available, 16 (22.5%) sera were MFC-negative. Among the patients who achieved a VGPR or better, patients with a normal HLCR had fewer MM-PCs than those with an abnormal HLCR (median 9.8x10-4vs. 46.0x10-4, respectively, P=0.062), although the difference was not statistically significant. Abnormal HLCR in CR samples was seen more frequently in patients with IgA type (19%) than IgG type (7.7%). Longer PFS and OS were observed in patients who achieved HLCR normalization at best response than in those who did not (PFS; 83.8 months vs. 41.8 month, respectively, P = 0.016 and OS; not reached vs. not reached, P = 0.018). When patients at best response were divided into with or without uninvolved HLC pair suppression, the latter group showed significantly better OS compared to the former group (not reached vs. not reached, P=0.019). CONCLUSIONS: The findings presented here suggest the potential usefulness of heavy/light chain immunoassays for monitoring of myeloma response in patients with IgA myeloma and residual MM-PC assessment at VGPR or better. Presence of abnormal HLCR at best response and HLC pair suppression were also associated with poorer survival. Disclosures No relevant conflicts of interest to declare.

scholarly journals Daratumumab Interferes with Flow Cytometric Evaluation of Multiple Myeloma

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 5630-5630 ◽  
Author(s):  
Sudhir Perincheri ◽  
Richard Torres ◽  
Christopher A Tormey ◽  
Brian R Smith ◽  
Henry M Rinder ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Flow Cytometry ◽  
Cell Population ◽  
Plasma Cell ◽  
Light Chain ◽  
Plasma Cells ◽  
Kappa Light Chain ◽  
Positive Events ◽  
History Of

Abstract The diagnosis of multiple myeloma (MM) requires the demonstration of clonal plasma cells at ≥10% marrow cellularity or a biopsy-proven bony or extra-medullary plasmacytoma, plus one or more myeloma-defining events. Clinical laboratories use multi-parameter flow cytometry (MFC) evaluation of cytoplasmic light chain expression in CD38-bright, CD45-dim or CD138-positive, CD45dim cells to establish plasma cell clonality with a high-degree of sensitivity and specificity. Daratumumab, a humanized IgG1 kappa monoclonal antibody targeting CD38, has been shown to significantly improve outcomes in refractory MM, and daratumumab was granted breakthrough status in 2013. Daratumumab is currently approved for treatment of MM patients who have failed first-line therapies. It has been noted that daratumumab can interfere in blood bank assays for antibody screening, as well as serum protein electrophoresis (SPEP). We describe for the first time daratumumab interference in the assessment of plasma cell neoplasms by MFC; daratumumab interfered with both CD38- and CD138-based gating strategies in three MM patients. Patient A is a 68 year old man with a 10 year history of MM who had failed multiple therapies. He had then been treated with daratumumab for two months, stopping therapy 25 days prior to bone marrow assessment. Patient B is a 53 year old man with a 3 year history MM who had failed numerous treatments. He had been receiving daratumumab monotherapy for two months at the time of his bone marrow studies. On multiple marrow aspirates at times of relapse prior to receiving daratumumab, both patients had demonstrated CD38-bright positive CD45dim/negative plasma cells expressing aberrant CD56, as well as kappa light chain restriction; mature B cells were polyclonal in both. Patient C is a 65 year old man with a four-year history of MM status post autologous stem cell transplantation, who had been receiving carfilzomib and pomalidomide following relapse and continues to have rising lambda light chains and rib pain. He now has abnormal plasma cells in blood worrisome for plasma cell leukemia. Bone marrow aspirates from patients A and B, and blood from patient C demonstrated near absence of CD38-bright events as detected by MFC (Figure 1). Hypothesizing that these results were due to blocking of the CD38 antigen by daratumumab, gating on CD138-positive events was assessed; surprisingly, virtually no CD138-positive events were detected by MFC. All 3 samples demonstrated a CD56-positive CD45dim population; when light chain studies were employed using specific gating on the CD56-positive population, light chain restriction was demonstrated in all patients (Figure 1). Aspirate morphology confirmed numerous abnormal, nucleolated plasma cells (Figure 2A), thus excluding a sampling error. CD138 and CD38 expression was also tested on the marrow biopsy cores from both patients. In contrast to MFC, immunohistochemistry (IHC) showed positive labeling of plasma cells with both CD138 (Figure 2B) and CD38 (Figure 2C). The reason for the labeling discrepancy between MFC and IHC is unknown. The different antibodies in the assays may target different epitopes; alternatively, tissue fixation/decalcification may dissociate the anti-CD38 therapeutic monoclonal from its target. Detection of clonal plasma cell populations is important for assessing response to therapy. Laboratories relying primarily on MFC to assess marrow aspirates without a concomitant biopsy may falsely diagnose remission or significant disease amelioration in daratumumab-treated patients. MFC is generally highly sensitive for monitoring minimal residual disease (MRD) in MM, but daratumumab-treated patients should have their biopsy evaluated to confirm the MRD assessment by MFC. We were able to detect large numbers of plasma cells and also demonstrate clonality in our patients based on an alternative MFC marker, aberrant CD56 expression, an approach that may not be possible in all cases. Figure 1 Flow cytometry showing near-absence of CD38-bright elements in the marrow of patient A (top panels). Gating on CD56-positive cells in the same sample reveals a kappa light chain-restricted plasma cell population (bottom panels). Figure 1. Flow cytometry showing near-absence of CD38-bright elements in the marrow of patient A (top panels). Gating on CD56-positive cells in the same sample reveals a kappa light chain-restricted plasma cell population (bottom panels). Figure 1 The marrow aspirate from Fig. 1 shows abnormal plasma cells (A). Immunohistochemistry on the concomitant biopsy shows the presence of numerous CD138-positive (B) and CD38-positive (C) plasma cells. Figure 1. The marrow aspirate from Fig. 1 shows abnormal plasma cells (A). Immunohistochemistry on the concomitant biopsy shows the presence of numerous CD138-positive (B) and CD38-positive (C) plasma cells. Disclosures No relevant conflicts of interest to declare.

scholarly journals Prognostic Impact of Immunophenotypic Response and Normalization of Serum Free Light Chain Among Patients with Multiple Myeloma

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2116-2116
Author(s):  
Kota Fukumoto ◽  
Manabu Fujisawa ◽  
Keisuke Seike ◽  
Yasuhito Suehara ◽  
Masafumi Fukaya ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Flow Cytometry ◽  
Light Chain ◽  
Maintenance Treatment ◽  
Plasma Cells ◽  
Prognostic Impact ◽  
Serum Free ◽  
Serum Free Light Chain ◽  
Better Than

Abstract Introduction: With the development of novel therapeutic agents, more than 30% of patients with multiple myeloma (MM) achieve complete response (CR) as defined by the International Myeloma Working Group (IMWG). However, most patients that achieve CR ultimately die due to relapse, suggesting the presence of minimal residual disease (MRD) in these patients. Multicolor flow cytometry (MFC) allows the detection of < 10-4 clonal plasma cells in normal bone marrow cells and has been used for detecting MRD after treatment. MFC-defined immunophenotypic response (IR) has emerged as a more relevant prognostic factor in patients with MM. However, the relevance of the prognostic impact of IR and the normalization of serum free light chain (sFLC) ratio remain unclear. We retrospectively analyzed the impact of IR, conventional immunofixation negative CR (CR), and CR plus FLC kappa/lambda (k/l) normal CR (sCR) on the prognosis of 83 patients with MM who obtained better than very good partial response (VGPR) at Kameda Medical Center, Kamogawa, Japan. Methods: Among the 164 patients treated at our hospital between April 2005 and July 2014, 83 patients that achieved more than VGPR were included in this study. The study population consisted of 49 males and 34 females with a median age of 71 years. All patients received at least one course of novel agent-containing therapeutic regimen. Autologous stem cell transplantation was performed 43 patients. Maintenance treatment was not systematically given, but patients failed to achieve CR continued to receive treatment until CR was obtained. Treatment responses were assessed using the IMWG criteria, and the best response to treatment during the course of disease was assessed by simultaneous analysis by serum immunofixation, sFLC measurements, and MFC analysis of bone marrow plasma cells. Identification of plasma cells MFC requires at least two markers (CD38 and either CD45 or CD138) by single-tube 6-color flow-cytometry. Neoplastic plasma cells were further identified from normal plasma cell based on differential expression of CD19 and CD45 characteristics. Patients were considered MRD negative (IR) when ≤ 50 neoplastic plasma cells were detected by MFC in the bone marrow samples at the sensitivity limit of 10-4. Overall survival (OS) and Time to next treatment (TNT) differences between curves were calculated by two-sided log-rank test. Subjects were classified into three categories, i.e., CR with MRD positive or negative and VGPR, and TNT and OS were compared between groups. Results: At a median follow-up of 44.8 months, 83 patients obtained better than VGPR, ie; CR, 55 patients, VGPR, 28 patients. Among the 55 patients who obtained CR, normalization of sFLC k/l and IR were achieved in 48 (88%) and 28 (51%) patients, respectively. Conversely, normal sFLC k/l ratio was achieved in 66 patients, 50 were in CR and 16 were in VGPR. IR was obtained in 34/83 (41%) patients. Among 48 CR patients with normal sFLC k/l (stringent CR), IR was obtained 27 patients (56%). All of the 7 CR patients with abnormal sFLC k/l (non-stringent CR) did not achieve IR. Kaplan–Meier estimated 3- and 5-year OS were 94% and 80% in patients with CR, 90% and 71% in patients with VGPR. No significant differences were observed at 3- and 5-year OS between patients achieved CR and VGPR. Among the patients with VGPR or better response, patients with IR showed significantly longer TNT compared to those without IR. However, The patients who achieved CR and IR showed significantly longer TNT compared to those with VGPR (P=0.004), but CR patients without IR showed similar TNT curve with VGPR patients. Patients with both CR and IR showed longer TNT than those CR but without IR, although difference between the 2 groups was marginally significant (P=0.06). Although, patients with IR and normal sFLC showed significantly longer TNT compared to those with VGPR, it was not translated to longer OS reflecting the continuous maintenance treatment for VGPR patients. Conclusion: Although both achievement of CR, normalization of sFLC k/l, and IR appeared to confer on longer TNT and OS, obtaining IR seems to have greater implications for longer survival compared to CR or FLC k/l normalization. MFC analysis is a rapid, affordable, and easy performable method for measurement of MRD, and IR could be considered as a goal of treatment for patients with MM. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Minimal Residual Disease Analysis in Multiple Myeloma Patients By 6-Color Flow Cytometry: An Experience from Tertiary Care Center of North India

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 5343-5343
Author(s):  
Praveen Sharma ◽  
Man Updesh Singh Sachdeva ◽  
Neelam Varma ◽  
Parveen Bose ◽  
Pankaj Malhotra
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Flow Cytometry ◽  
Light Chain ◽  
Bone Marrow Aspirate ◽  
Plasma Cells ◽  
Residual Disease ◽  
Color Flow ◽  
Multiparametric Flow Cytometry ◽  
Minimal Residual

Abstract Therapeutic advances in multiple myeloma (MM) incorporating the use of high-dose melphalan, novel therapeutic immunomodulatory agents, proteasome inhibitors and supporting autologous stem-cell transplantation (ASCT) have improved response rates and overall survival. The detection of minimal residual disease (MRD) is recognized as a sensitive and rapid approach to evaluate treatment efficacy as a tool for predicting patient outcomes and guiding therapeutic decisions. MRD analysis is reflected by many different techniques, however, multiparametric flow cytometry is a sensitive, feasible and adequate method for monitoring residual disease. Studies from India related to this context are lacking. In the present study, we compare MRD levels in patients of multiple myeloma after chemotherapy/ASCT assessed by multiparametric flow cytometry, with M band status, immunofixation (IFE) and percentage of plasma cells on bone marrow aspirate. Seventeen patients of multiple myeloma were included in the study over a duration of one year, (Male=13, Female=4) with mean age of 56.8 years (range 44-80 years). MRD was analyzed using a dual laser 6 color-flow cytometer in 9 patients of ASCT (day 100) and 8 patients on chemotherapy alone (post-induction). Pre-titrated cocktail of CD38, CD138, CD19, CD45, cytoplasmic Kappa light chain, cytoplasmic lambda light chain, CD81, CD27, CD28 CD200 and CD10 were used in 6-color combination of three tubes for MRD analysis. MRD was detectable in 5 patients, mean of 0.61% (range of 0.07 - 6.44%). M band and IFE were positive in 2 patients, each. Bone marrow plasma cells ranged from 0 to 22%. MRD levels did not show significant correlation with percentage of plasma cells in bone marrow aspirate, however it had an statistical agreement with presence or absence of serum M-band and IFE. Patients are on regular follow up for their clinical and hematological response. Disclosures No relevant conflicts of interest to declare.

scholarly journals ABCG2 expression, function, and promoter methylation in human multiple myeloma

Blood ◽  
2006 ◽  
Vol 108 (12) ◽  
pp. 3881-3889 ◽  
Author(s):  
Joel G. Turner ◽  
Jana L. Gump ◽  
Chunchun Zhang ◽  
James M. Cook ◽  
Douglas Marchion ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Flow Cytometry ◽  
Drug Resistance ◽  
Protein Expression ◽  
Cell Lines ◽  
Promoter Methylation ◽  
Plasma Cells ◽  
Cancer Resistance ◽  
Response To Chemotherapy ◽  
Mrna And Protein Expression

AbstractWe investigated the role of the breast cancer resistance protein (BCRP/ABCG2) in drug resistance in multiple myeloma (MM). Human MM cell lines, and MM patient plasma cells isolated from bone marrow, were evaluated for ABCG2 mRNA expression by quantitative polymerase chain reaction (PCR) and ABCG2 protein, by Western blot analysis, immunofluorescence microscopy, and flow cytometry. ABCG2 function was determined by measuring topotecan and doxorubicin efflux using flow cytometry, in the presence and absence of the specific ABCG2 inhibitor, tryprostatin A. The methylation of the ABCG2 promoter was determined using bisulfite sequencing. We found that ABCG2 expression in myeloma cell lines increased after exposure to topotecan and doxorubicin, and was greater in logphase cells when compared with quiescent cells. Myeloma patients treated with topotecan had an increase in ABCG2 mRNA and protein expression after treatment with topotecan, and at relapse. Expression of ABCG2 is regulated, at least in part, by promoter methylation both in cell lines and in patient plasma cells. Demethylation of the promoter increased ABCG2 mRNA and protein expression. These findings suggest that ABCG2 is expressed and functional in human myeloma cells, regulated by promoter methylation, affected by cell density, up-regulated in response to chemotherapy, and may contribute to intrinsic drug resistance.

ABT-737, an Inhibitor of Bcl-2/Bcl-XL Proteins, Is Cytotoxic in Multiple Myeloma Cells.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1589-1589
Author(s):  
Michael Kline ◽  
Terry Kimlinger ◽  
Michael Timm ◽  
Jessica Haug ◽  
John A. Lust ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Flow Cytometry ◽  
Tumor Microenvironment ◽  
Cell Lines ◽  
Plasma Cells ◽  
Annexin V ◽  
Significant Activity ◽  
Rpmi 8226 ◽  
Dose Dependent

Abstract Background: Multiple myeloma (MM) is a plasma cell proliferative disorder that is incurable with the currently available therapeutics. New therapies based on better understanding of the disease biology are urgently needed. MM is characterized by accumulation of malignant plasma cells predominantly in the bone marrow. These plasma cells exhibit a relatively low proliferative rate as well as a low rate of apoptosis. Elevated expression of the anti-apoptotic Bcl-2 family members has been reported in MM cell lines as well as in primary patient samples and may be correlated with disease stage as well as resistance to therapy. ABT-737 (Abbott Laboratories, Abbott Park, IL) is a small-molecule inhibitor designed to specifically inhibit anti-apoptotic proteins of the Bcl-2 family and binds with high affinity to Bcl-XL, Bcl-2, and Bcl-w. ABT-737 exhibits toxicity in human tumor cell lines, malignant primary cells, and mouse tumor models. We have examined the in vitro activity of this compound in the context of MM to develop a rationale for future clinical evaluation. Methods: MM cell lines were cultured in RPMI 1640 containing 10% fetal bovine serum supplemented with L-Glutamine, penicillin, and streptomycin. The KAS-6/1 cell line was also supplemented with 1 ng/ml IL-6. Cytotoxicity of ABT-737 was measured using the MTT viability assay. Apoptosis was measured using flow cytometry upon cell staining with Annexin V-FITC and propidium iodide (PI). Flow cytometry was also used to measure BAX: Bcl-2 ratios after ABT-737 treatment and cell permeabilization with FIX & PERM (Caltag Laboratories, Burlingame, CA) Results: ABT-737 exhibited cytotoxicity in several MM cell lines including RPMI 8226, KAS-6/1, OPM-1, OPM-2, and U266 with an LC50 of 5-10μM. The drug also had significant activity against MM cell lines resistant to conventional agents such as melphalan (LR5) and dexamethasone (MM1.R) with similar LC50 (5-10 μM), as well as against doxorubicin resistant cells (Dox40), albeit at higher doses. Furthermore, ABT-737 retained activity in culture conditions reflective of the permissive tumor microenvironment, namely in the presence of VEGF, IL-6, or in co-culture with marrow-derived stromal cells. ABT-737 was also cytotoxic to freshly isolated primary patient MM cells. Time and dose dependent induction of apoptosis was confirmed using Annexin V/PI staining of the MM cell line RPMI 8226. Flow cytometry analysis of cells treated with ABT-737 demonstrated a time and dose dependent increase in pro-apoptotic BAX protein expression without significant change in the Bcl-XL or Bcl-2 expression. Ongoing studies are examining the parameters and mechanisms of ABT-737 cytotoxicity to MM cells in more detail. Conclusion: ABT-737 has significant activity against MM cell lines and patient derived primary MM cells in vitro. It is able to overcome resistance to conventional anti-myeloma agents suggesting a different mechanism of toxicity that may replace or supplement these therapies. Additionally, it appears to be able to overcome resistance offered by elements of the tumor microenvironment. The results of these studies will form the framework for future clinical evaluation of this agent in the clinical setting.

CS1: A Potential New Therapeutic Target for the Treatment of Multiple Myeloma.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3457-3457 ◽  
Author(s):  
Eric D. Hsi ◽  
Roxanne Steinle ◽  
Balaji Balasa ◽  
Aparna Draksharapu ◽  
Benny Shum ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Flow Cytometry ◽  
B Cell ◽  
Mononuclear Cells ◽  
Plasma Cells ◽  
Target Cells ◽  
Dependent Manner ◽  
Myeloma Cells ◽  
Effector Cells

Abstract Background: To identify genes upregulated in human memory B and plasma cells, naïve B cell cDNA was subtracted from plasma cell and memory B cell cDNA. One gene that was highly expressed in plasma cells encodes CS1 (CD2 subset 1, CRACC, SLAMF7), a cell surface glycoprotein of the CD2 family. CS1 was originally identified as a natural killer (NK) cell marker. Monoclonal antibodies (mAbs) specific for CS1 were used to validate CS1 as a potential target for the treatment of multiple myeloma (MM). Methods: Anti-CS1 mAbs were generated by immunizing mice with a protein comprising of the extracellular domain of CS1. Two clones, MuLuc63 and MuLuc90, were selected to characterize CS1 protein expression in normal and diseased tissues and blood. Fresh frozen tissue analysis was performed by immunohistochemistry (IHC). Blood and bone marrow analysis was performed using flow cytometry with directly conjugated antibodies. HuLuc63, a novel humanized anti-CS1 mAb (derived from MuLuc63) was used for functional characterization in non-isotopic LDH-based antibody-dependent cellular cytotoxicity (ADCC) assays. Results: IHC analysis showed that anti-CS1 staining occurred only on mononuclear cells within tissues. The majority of the mononuclear cells were identified as tissue plasma cells by co-staining with anti-CD138 antibodies. No anti-CS1 staining was detected on the epithelia, smooth muscle cells or vessels of any normal tissues tested. Strong anti-CS1 staining was also observed on myeloma cells in 9 of 9 plasmacytomas tested. Flow cytometry analysis of whole blood from both normal healthy donors and MM patients showed specific anti-CS1 staining in a subset of leukocytes, consisting primarily of CD3−CD(16+56)+ NK cells, CD3+CD(16+56)+ NKT cells, and CD3+CD8+ T cells. Flow cytometry of MM bone marrow showed a similar leukocyte subset staining pattern, except that strong staining was also observed on the majority of CD138+CD45−/dim to + myeloma cells. No anti-CS1 binding was detected to hematopoietic CD34+CD45+ stem cells. To test if antibodies towards CS1 may have anti-tumor cell activity in vitro, ADCC studies using effector cells (peripheral blood mononuclear cells) from 23 MM patients and L363 MM target cells were performed. The results showed that HuLuc63, a humanized form of MuLuc63, induced significant ADCC in a dose dependent manner. Conclusions: Our study identifies CS1 as an antigen that is uniformly expressed on normal and neoplastic plasma cells at high levels. The novel humanized anti-CS1 mAb, HuLuc63, exhibits significant ADCC using MM patient effector cells. These results demonstrate that HuLuc63 could be a potential new treatment for multiple myeloma. HuLuc63 will be entering a phase I clinical study for multiple myeloma.

Defining Complete Response in Multiple Myeloma: Role of the Serum Free Light Chain Assay and Multiparameter Flow Cytometry.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1479-1479 ◽  
Author(s):  
Roger G. Owen ◽  
J. Anthony Child ◽  
Andy C. Rawstron ◽  
Sue Bell ◽  
Kim Cocks ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Light Chain ◽  
Plasma Cells ◽  
Complete Response ◽  
Free Light Chain ◽  
Multiparameter Flow Cytometry ◽  
High Dose ◽  
Reference Laboratory ◽  
Serum Free ◽  
Serum Free Light Chain

Abstract It is becoming increasingly clear that the use of immunofixation (IF) to define complete response (CR) in MM has its limitations. Paraprotein concentration is not a direct measure of tumour bulk and maximal responses may take many months to achieve which inevitably underestimate CR rates in therapeutic schedules that contain the sequential use of different agents. The purpose of this study was to prospectively assess the applicability and value of the serum free light chain (SFLC) assay and multiparameter flow cytometry (MFC) to assess CR in the intensive pathway of the MRC Myeloma IX Trial. In this trial patients are initially randomised to induction with CVAD or CTD and patients with stable disease or better proceed to high dose melphalan (HDM) with stem cell support. There is a second randomisation to maintenance thalidomide or no further therapy. SFLC as well as standard serum and urine paraprotein assessments were performed in a central reference laboratory at the following time points: presentation, end of induction, day 100 post HDM and 3 monthly until relapse. Similarly MFC in which neoplastic plasma cells are identified and differentiated from normal plasma cells on the basis of CD19 and CD56 expression was evaluated (again in a central laboratory) at presentation, end of induction and day 100 following HDM and annually until relapse. An initial analysis of 207/1114 randomised patients was performed and the results are detailed below - End of induction Day 100 post HDM IF negative 16.3% 49.4% SFLC normal 46.1% 78.6% MFC negative 10.2% 50.7% The SFLC assay was informative in 95% of patients and provided for a more rapid assessment of response than conventional methods. A normal SFLC assay at the end of induction appeared to predict for attainment of an IF-neg CR at day 100 (70% IF-neg CR if SFLC normal vs 30% when SFLC abnormal at the end of induction). It should however be noted that 58% of patients who failed to achieve an IF-neg CR at day 100 had a normal SFLC assay. MFC provides for a direct assessment of residual neoplastic plasma cells. The assay was informative in 96.7% of patients and has a reproducible sensitivity of 0.01%. The majority of patients (89.8%) had detectable disease at the end of induction with a median of 0.7% neoplastic plasma cells (range 0.01–14%). Further cytoreduction was provided by the HDM such that 49.3% had flow detectable disease at day 100 with a median of 0.26% neoplastic plasma cells (range 0.02–8%). 30% of patients with IF-neg CR had detectable disease while 21% of patients with a persistent paraprotein had no detectable disease in their marrow. The majority of the latter patients had IgG paraproteins and it is postulated that many of these pts will ultimately achieve an IF-neg CR. We would conclude that given the kinetics of paraprotein clearance in MM it may be more appropriate to define CR on the basis of a normal SFLC assay and the absence of minimal residual disease by MFC. In this way it should be possible to more accurately define the CR rate achieved by individual components of multi-agent sequential regimens.

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