Imaging flow cytometric detection of del(17p) in bone marrow and circulating plasma cells in multiple myeloma

BACKGROUND

Detection of del(17p) in myeloma is generally performed by fluorescence in situ hybridization (FISH) on a slide with analysis of up to 200 nuclei. The small cell sample analyzed makes this a low precision test. We report the utility of an automated FISH method, called "immuno-flowFISH", to detect plasma cells with adverse prognostic risk del(17p) in bone marrow and blood samples of patients with myeloma.

METHODS

Bone marrow (n = 31) and blood (n = 19) samples from 35 patients with myeloma were analyzed using immuno-flowFISH. Plasma cells were identified by CD38/CD138-immunophenotypic gating and assessed for the 17p locus and centromere of chromosome 17. Cells were acquired on an AMNIS ImageStreamX MkII imaging flow cytometer using INSPIRE software.

RESULTS

Chromosome 17 abnormalities were identified in CD38/CD138-positive cells in bone marrow (6/31) and blood (4/19) samples when the percent plasma cell burden ranged from 0.03% to 100% of cells. Abnormalities could be identified in 14.5%-100% of plasma cells.

CONCLUSIONS

The "immuno-flowFISH" imaging flow cytometric method could detect del(17p) in plasma cells in both bone marrow and blood samples of myeloma patients. This method was also able to detect gains and losses of chromosome 17, which are also of prognostic significance. The lowest levels of 0.009% (bone marrow) and 0.001% (blood) for chromosome 17 abnormalities was below the detection limit of current FISH method. This method offers potential as a new means of identifying these prognostically important chromosomal defects, even when only rare cells are present and for serial disease monitoring.

Liquid Biopsies as Non-Invasive Tools for Mutation Profiling in Multiple Myeloma: Application Potential, Challenges, and Opportunities

Over the last decades, the survival of multiple myeloma (MM) patients has considerably improved. However, despite the availability of new treatments, most patients still relapse and become therapy-resistant at some point in the disease evolution. The mutation profile has an impact on MM patients' outcome, while typically evolving over time. Because of the patchy bone marrow (BM) infiltration pattern, the analysis of a single bone marrow sample can lead to an underestimation of the known genetic heterogeneity in MM. As a result, interest is shifting towards blood-derived liquid biopsies, which allow for a more comprehensive and non-invasive genetic interrogation without the discomfort of repeated BM aspirations. In this review, we compare the application potential for mutation profiling in MM of circulating-tumor-cell-derived DNA, cell-free DNA and extracellular-vesicle-derived DNA, while also addressing the challenges associated with their use.

Rapid generation of human recombinant monoclonal antibodies from antibody-secreting cells using ferrofluid-based technology

Monoclonal antibodies (mAbs) are one of the most important classes of biologics with high therapeutic and diagnostic value, but traditional methods for mAbs generation, such as hybridoma screening and phage display, have limitations, including low efficiency and loss of natural chain pairing. To overcome these challenges, novel single B cell antibody technologies have emerged, but they also have limitations such as in vitro differentiation of memory B cells and expensive cell sorters. In this study, we present a rapid and efficient workflow for obtaining human recombinant monoclonal antibodies directly from single antigen-specific antibody secreting cells (ASCs) in the peripheral blood of convalescent COVID-19 patients using ferrofluid technology. This process allows the identification and expression of recombinant antigen-specific mAbs in less than 10 days, using RT-PCR to generate linear Ig heavy and light chain gene expression cassettes, called "minigenes", for rapid expression of recombinant antibodies without cloning procedures. This approach has several advantages. First, it saves time and resources by eliminating the need for in vitro differentiation. It also allows individual antigen-specific ASCs to be screened for effector function prior to recombinant antibody cloning, enabling the selection of mAbs with desired characteristics and functional activity. In addition, the method allows comprehensive analysis of variable region repertoires in combination with functional assays to evaluate the specificity and function of the generated antigen-specific antibodies. Our approach, which rapidly generates recombinant monoclonal antibodies from single antigen-specific ASCs, could help to identify functional antibodies and deepen our understanding of antibody dynamics in the immune response through combined antibody repertoire sequence analysis and functional reactivity testing.

Exploring the efficacy and safety of anti-BCMA chimeric antigen receptor T-cell therapy for multiple myeloma: Systematic review and meta-analysis

Objective

Multiple myeloma (MM) is a bone marrow cancer that profoundly affects plasma cells involved in the immune response. Myeloma cells alter the average production of cells in the bone marrow. Anti-B-cell maturation antigen (BCMA) chimeric antigen receptor (CAR) T-cell therapy allows genetic modifications of an individual's T-cells to increase the expression of CARs used to identify and attach BCMA proteins to the malignant cells. Our main objective is to perform a systematic review and meta-analysis to explore the efficacy and safety of anti-BCMA CAR T-cell therapy for MM.

Material and Methods

We searched five databases, PubMed, CNKI, EMBASE, Cochrane, Web of Science, and CNKI, for studies published on anti-BCMA,CAR-T-cell treatment for MM. Inclusion criteria involved prospective single-arm studies either single or multi-center, in various MM phases and studies that reported anti-BCMA,CAR-T-cell treatment for MM. We excluded non-English publications and conference papers. All statistical analyses were performed in R software and Review Manager 5.4.1.

Results

Thirteen articles were included in the analysis. We found that the overall response survival complete response increase was statistically significant. Similarly, the reduction in cytokine release syndrome grades 3 and 4 and neurotoxicity after follow-up was statistically significant. However, the reduction in minimal residual disease negativity (MRDN) was not statistically significant.

Conclusion

Using anti-BCMA CAR T-cell therapy in MM was highly efficacious and safe in lowering the adverse outcomes and improving the survival outcomes, complete response, and overall response.

Utilizing 3D Models to Unravel the Dynamics of Myeloma Plasma Cells' Escape from the Bone Marrow Microenvironment

Recent therapeutic advancements have markedly increased the survival rates of individuals with multiple myeloma (MM), doubling survival compared to pre-2000 estimates. This progress, driven by highly effective novel agents, suggests a growing population of MM survivors exceeding the 10-year mark post-diagnosis. However, contemporary clinical observations indicate potential trends toward more aggressive relapse phenotypes, characterized by extramedullary disease and dominant proliferative clones, despite these highly effective treatments. To build upon these advances, it is crucial to develop models of MM evolution, particularly focusing on understanding the biological mechanisms behind its development outside the bone marrow. This comprehensive understanding is essential to devising innovative treatment strategies. This review emphasizes the role of 3D models, specifically addressing the bone marrow microenvironment and development of extramedullary sites. It explores the current state-of-the-art in MM modelling, highlighting challenges in replicating the disease's complexity. Recognizing the unique demand for accurate models, the discussion underscores the potential impact of these advanced 3D models on understanding and combating this heterogeneous and still incurable disease.

Label-free microfluidic chip for segregation and recovery of circulating leukemia cells: clinical applications in acute myeloid leukemia

We present a label-free microfluidic chip for the segregation of circulating leukemia cells (CLCs) from blood samples, with a focus on its clinical applications in Acute Myeloid Leukemia (AML). The microfluidic chip achieved an approximate capture efficiency of 92%. The study analyzed a comprehensive set of 66 blood specimens from AML patients in different disease stages, including newly diagnosed and relapsing cases, patients in complete remission, and those in partial remission. The results showed a significant difference in CLC counts between active disease stages and remission stages (p < 0.0001), with a proposed threshold of 5 CLCs to differentiate between the two. The microfluidic chip exhibited a sensitivity of 95.4% and specificity of 100% in predicting disease recurrence. Additionally, the captured CLCs were subjected to downstream molecular analysis using droplet digital PCR, allowing for the identification of genetic mutations associated with AML. Comparative analysis with bone marrow aspirate processing by FACS demonstrated the reliability and accuracy of the microfluidic chip in tracking disease burden, with highly agreement results obtained between the two methods. The non-invasive nature of the microfluidic chip and its ability to provide real-time insights into disease progression make it a promising tool for the proactive monitoring and personalized patient care of AML.

Precision Isolation of Circulating Leukemia Cells in Chronic Myelogenous Leukemia Patients Using a Novel Microfluidic Device and Its Clinical Applications

Chronic Myelogenous Leukemia (CML) is a prevalent hematologic malignancy characterized by the malignant transformation of myeloid cells and their proliferation in the peripheral blood. The management of CML poses significant challenges, particularly in detecting and eradicating minimal residual disease, which is crucial for preventing relapse and improving survival outcomes. Traditional minimal residual disease detection methods, such as bone marrow aspiration, are invasive and have limitations which include the potential for sampling errors and false negatives. This study introduces a novel label-free microfluidic chip designed for the segregation and recovery of circulating leukemia cells, offering a non-invasive liquid biopsy approach with potential applications in precision medicine. Over July 2021 to October 2023, we recruited 56 CML patients across various disease stages and collected blood samples for analysis using our microfluidic device. The device demonstrated high efficacy in isolating circulating leukemia cells, with an optimal capture efficiency of 78% at a sample flow rate of 3 mL/h. Our results indicate that the microfluidic device can efficiently segregate and quantify circulating leukemia cells, providing a detailed understanding of CML progression and treatment response. The significant reduction in circulating leukemia cell counts in patients in complete remission highlights the device's potential in monitoring treatment efficacy. Furthermore, the device's sensitivity in detecting minimal residual disease could offer a more reliable prognostic tool for therapeutic decision-making in CML management.

Liquid biopsy-based monitoring of residual disease in multiple myeloma by analysis of the rearranged immunoglobulin genes-A feasibility study

The need for sensitive monitoring of minimal/measurable residual disease (MRD) in multiple myeloma emerged as novel therapies led to deeper responses. Moreover, the potential benefits of blood-based analyses, the so-called liquid biopsy is prompting more and more studies to assess its feasibility. Considering these recent demands, we aimed to optimize a highly sensitive molecular system based on the rearranged immunoglobulin (Ig) genes to monitor MRD from peripheral blood. We analyzed a small group of myeloma patients with the high-risk t(4;14) translocation, using next-generation sequencing of Ig genes and droplet digital PCR of patient-specific Ig heavy chain (IgH) sequences. Moreover, well established monitoring methods such as multiparametric flow cytometry and RT-qPCR of the fusion transcript IgH::MMSET (IgH and multiple myeloma SET domain-containing protein) were utilized to evaluate the feasibility of these novel molecular tools. Serum measurements of M-protein and free light chains together with the clinical assessment by the treating physician served as routine clinical data. We found significant correlation between our molecular data and clinical parameters, using Spearman correlations. While the comparisons of the Ig-based methods and the other monitoring methods (flow cytometry, qPCR) were not statistically evaluable, we found common trends in their target detection. Regarding longitudinal disease monitoring, the applied methods yielded complementary information thus increasing the reliability of MRD evaluation. We also detected indications of early relapse before clinical signs, although this implication needs further verification in a larger patient cohort.

Liquid biopsy by analysis of circulating myeloma cells and cell-free nucleic acids: a novel noninvasive approach of disease evaluation in multiple myeloma

Multiple myeloma (MM) is an incurable hematological cancer with high spatial- and temporal-heterogeneity. Invasive single-point bone marrow sampling cannot capture the tumor heterogeneity and is difficult to repeat for serial assessments. Liquid biopsy is a technique for identifying and analyzing circulating MM cells and cell products produced by tumors and released into the circulation, allowing for the minimally invasive and comprehensive detection of disease burden and molecular alterations in MM and monitoring treatment response and disease progression. Furthermore, liquid biopsy can provide complementary information to conventional detection approaches and improve their prognostic values. This article reviewed the technologies and applications of liquid biopsy in MM.

Circulating Tumour Cells, Cell Free DNA and Tumour-Educated Platelets as Reliable Prognostic and Management Biomarkers for the Liquid Biopsy in Multiple Myeloma

Simple Summary

Even though the presently employed biomarkers in the detection and management of multiple myeloma are demonstrating encouraging results, the mortality percentage of the malignancy is still elevated. Thus, searching for new diagnostic or prognostic markers is pivotal. Liquid biopsy allows the examination of circulating tumour DNA, cell-free DNA, extracellular RNA, and cell free proteins, which are released into the bloodstream due to the breakdown of tumour cells or exosome delivery. Liquid biopsy can now be applied in clinical practice to diagnose, and monitor multiple myeloma, probably allowing a personalized treatment of the disease.

Abstract

Liquid biopsy is one of the fastest emerging fields in cancer evaluation. Circulating tumour cells and tumour-originated DNA in plasma have become the new targets for their possible employ in tumour diagnosis, and liquid biopsy can define tumour burden without invasive procedures. Multiple Myeloma, one of the most frequent hematologic tumors, has been the target of therapeutic progresses in the last few years. Bone marrow aspirate is the traditional tool for diagnosis, prognosis, and genetic evaluation in multiple myeloma patients. However, this painful procedure presents a relevant drawback for regular disease examination as it requires an invasive practice. Moreover, new data demonstrated that a sole bone marrow aspirate is incapable of expressing the multifaceted multiple myeloma genetic heterogeneity. In this review, we report the emerging usefulness of the assessment of circulating tumour cells, cell-free DNA, extracellular RNA, cell-free proteins, extracellular vesicles, and tumour-educated platelets to evaluate the changing mutational profile of multiple myeloma, as early markers of disease, reliable predictors of prognosis, and as useful tools to perform less invasive monitoring in multiple myeloma.

Review of Multiple Myeloma Genetics including Effects on Prognosis, Response to Treatment, and Diagnostic Workup

Multiple myeloma is a disorder of the monoclonal plasma cells and is the second most common hematologic malignancy. Despite improvements in survival with newer treatment regimens, multiple myeloma remains an incurable disease and most patients experience multiple relapses. Multiple myeloma disease initiation and progression are highly dependent on complex genetic aberrations. This review will summarize the current knowledge of these genetic aberrations, how they affect prognosis and the response to treatment, and review sensitive molecular techniques for multiple myeloma workup, with the ultimate goal of detecting myeloma progression early, allowing for timely treatment initiation.

Enrichment-Free Single-Cell Detection and Morphogenomic Profiling of Myeloma Patient Samples to Delineate Circulating Rare Plasma Cell Clones

Multiple myeloma is an incurable malignancy that initiates from a bone marrow resident clonal plasma cell and acquires successive mutational changes and genomic alterations, eventually resulting in tumor burden accumulation and end-organ damage. It has been recently recognized that myeloma secondary genomic events result in extensive sub-clonal heterogeneity both in localized bone marrow areas and circulating peripheral blood plasma cells. Rare genomic subclones, including myeloma initiating cells, could be the drivers of disease progression and recurrence. Additionally, evaluation of rare myeloma cells in blood for disease monitoring has numerous advantages over invasive bone marrow biopsies. To this end, an unbiased method for detecting rare cells and delineating their genomic makeup enables disease detection and monitoring in conditions with low abundant cancer cells. In this study, we applied an enrichment-free four-plex (CD138, CD56, CD45, DAPI) immunofluorescence assay and single-cell DNA sequencing for morphogenomic characterization of plasma cells to detect and delineate common and rare plasma cells and discriminate between normal and malignant plasma cells in paired blood and bone marrow aspirates from five patients with newly diagnosed myeloma (N = 4) and monoclonal gammopathy of undetermined significance (n = 1). Morphological analysis confirms CD138+CD56+ cells in the peripheral blood carry genomic alterations that are clonally identical to those in the bone marrow. A subset of altered CD138+CD56- cells are also found in the peripheral blood consistent with the known variability in CD56 expression as a marker of plasma cell malignancy. Bone marrow tumor clinical cytogenetics is highly correlated with the single-cell copy number alterations of the liquid biopsy rare cells. A subset of rare cells harbors genetic alterations not detected by standard clinical diagnostic methods of random localized bone marrow biopsies. This enrichment-free morphogenomic approach detects and characterizes rare cell populations derived from the liquid biopsies that are consistent with clinical diagnosis and have the potential to extend our understanding of subclonality at the single-cell level in this disease. Assay validation in larger patient cohorts has the potential to offer liquid biopsy for disease monitoring with similar or improved disease detection as traditional blind bone marrow biopsies.

Biological Characterization and Clinical Relevance of Circulating Tumor Cells: Opening the Pandora's Box of Multiple Myeloma

Simple Summary

Bone marrow (BM) aspirates are mandatory for diagnosis and follow-up of patients with multiple myeloma (MM). However, they present two important caveats: Their invasiveness and limited scope to capture the broad tumor heterogeneity. Conversely, circulating tumor cells (CTCs) are detectable in the peripheral blood of patients with precursor and malignant disease states and have strong prognostic value. Moreover, the high genetic and transcriptomic overlap between both plasma cell compartments suggests that CTCs might reflect with notable precision the medullar clone. Furthermore, the study of CTCs could be used as a model to identify mechanisms favoring BM egression and disease spreading. Here, we summarize the state of the art on MM CTCs and provide insights on what they may offer in research and clinical scenarios.

Abstract

Bone marrow (BM) aspirates are the gold standard for patient prognostication and genetic characterization in multiple myeloma (MM). However, they represent an important limitation for periodic disease monitoring because they entail an aggressive procedure. Moreover, recent findings show that a single BM aspirate is unable to reflect the complex MM heterogeneity. Recent advances in flow cytometry, microfluidics, and “omics” technologies have opened Pandora’s box of MM: The detection and isolation of circulating tumor cells (CTCs) offer a promising and minimally invasive alternative for tumor assessment and metastasis study. CTCs are detectable in premalignant and active MM states, and their enumeration has strong prognostic value, to the extent that it is challenging current stratification systems. In addition, CTCs reflect with high precision both intra- and extra-medullary disease at the phenotypic, genomic, and transcriptomic levels. Despite this high resemblance between tumor clones in distinct locations, some subtle (not random) differences might shed some light on the metastatic process. Thus, it has been suggested that a hypoxic and pro-inflammatory microenvironment could induce an arrest in proliferation forcing tumor cells to recirculate. Herein, we summarize data on the characterization of MM CTCs as well as their clinical and research potential.

The Minimal Residual Disease Using Liquid Biopsies in Hematological Malignancies

Simple Summary

Monitoring the response to treatment in hematologic malignancies is essential in defining the best way to optimize patient management. In general, achieving a deeper response has been shown to lead to a better prognosis, and the techniques used to study the minimal residual disease (MRD) are becoming more precise. The use of liquid biopsies, that is, analyzing the presence of alterations in nucleic acids, usually in peripheral blood or other biological fluids, is being studied and optimized with increasingly innovative molecular techniques, such as next-generation sequencing (NGS) in the monitoring of the MRD, avoiding, in many cases, more invasive tests in different hematological neoplasms. Currently, liquid biopsies are not standardized for the MRD monitoring, but there is increasing evidence of its correlation with other techniques to measure responses to treatments and patient outcomes.

Abstract

The study of cell-free DNA (cfDNA) and other peripheral blood components (known as “liquid biopsies”) is promising, and has been investigated especially in solid tumors. Nevertheless, it is increasingly showing a greater utility in the diagnosis, prognosis, and response to treatment of hematological malignancies; in the future, it could prevent invasive techniques, such as bone marrow (BM) biopsies. Most of the studies about this topic have focused on B-cell lymphoid malignancies; some of them have shown that cfDNA can be used as a novel way for the diagnosis and minimal residual monitoring of B-cell lymphomas, using techniques such as next-generation sequencing (NGS). In myelodysplastic syndromes, multiple myeloma, or chronic lymphocytic leukemia, liquid biopsies may allow for an interesting genomic representation of the tumor clones affecting different lesions (spatial heterogeneity). In acute leukemias, it can be helpful in the monitoring of the early treatment response and the prediction of treatment failure. In chronic lymphocytic leukemia, the evaluation of cfDNA permits the definition of clonal evolution and drug resistance in real time. However, there are limitations, such as the difficulty in obtaining sufficient circulating tumor DNA for achieving a high sensitivity to assess the minimal residual disease, or the lack of standardization of the method, and clinical studies, to confirm its prognostic impact. This review focuses on the clinical applications of cfDNA on the minimal residual disease in hematological malignancies.

Monitoring multiple myeloma in the peripheral blood based on cell-free DNA and circulating plasma cells

With the advent of novel, highly effective therapies for multiple myeloma (MM), classical serologic monitoring appears insufficient for response assessment and prediction of relapse. Moreover, serologic studies in MM are hampered by interference of therapeutic antibodies. The detection of malignant plasma cell clones by next generation sequencing (NGS) or multiparameter flow cytometry (MFC) circumvents these difficulties and can be performed in the peripheral blood (pB) by targeting circulating cell-free DNA (cfDNA) or circulating plasma cells (CPCs), thus also avoiding an invasive sampling procedure. Here, we applied NGS of VJ light chain (LC) rearrangements in cfDNA and MFC of magnetically-enriched CD138-positive CPCs (me-MFC) to investigate disease burden in unselected MM patients. Sequencing was successful for 114/130 (87.7%) cfDNA samples and me-MFC results were analyzable for 196/205 (95.6%) samples. MM clones were detectable in 38.9% of samples taken at initial diagnosis or relapse (ID/RD), but only in 11.8% of samples taken during complete remission (CR). Circulating MM plasma cells were present in 83.3% of ID/RD samples and 9.9% of CR samples. Residual disease assessment by NGS or me-MFC in samples taken during very good partial remission or CR was 80% concordant. Notably, 4/4 (NGS) and 5/8 (me-MFC) positive CR samples were from patients with oligo- or non-secretory myeloma. The time to progression was shorter if there was evidence of residual myeloma in the pB. Together, our findings indicate that our two novel analytical approaches accurately indicate the course of MM and may be particularly valuable for monitoring patients with serologically non-trackable disease.

Single-cell profiling of tumour evolution in multiple myeloma - opportunities for precision medicine

Multiple myeloma (MM) is a haematological malignancy of plasma cells characterized by substantial intraclonal genetic heterogeneity. Although therapeutic advances made in the past few years have led to improved outcomes and longer survival, MM remains largely incurable. Over the past decade, genomic analyses of patient samples have demonstrated that MM is not a single disease but rather a spectrum of haematological entities that all share similar clinical symptoms. Moreover, analyses of samples from monoclonal gammopathy of undetermined significance and smouldering MM have also shown the existence of genetic heterogeneity in precursor stages, in some cases remarkably similar to that of MM. This heterogeneity highlights the need for a greater dissection of underlying disease biology, especially the clonal diversity and molecular events underpinning MM at each stage to enable the stratification of individuals with a high risk of progression. Emerging single-cell sequencing technologies present a superlative solution to delineate the complexity of monoclonal gammopathy of undetermined significance, smouldering MM and MM. In this Review, we discuss how genomics has revealed novel insights into clonal evolution patterns of MM and provide examples from single-cell studies that are beginning to unravel the mutational and phenotypic characteristics of individual cells within the bone marrow tumour, immune microenvironment and peripheral blood. We also address future perspectives on clinical application, proposing that multi-omics single-cell profiling can guide early patient diagnosis, risk stratification and treatment strategies.

Identification of novel combined biomarkers in the diagnosis of multiple myeloma

PURPOSE

Multiple myeloma (MM) is a haematological malignant disease with a clonal proliferation of plasma cells, and timely surveillance is helpful to improve the survival rate of patients with MM. However, there is a lack of simple and effective biomarkers for the diagnosis, prognosis, and residual disease evaluation of MM.

MATERIAL & METHODS

In the detection cohort, we used the samples from six newly diagnosed MM patients and six control subjects. Plasma proteins were labelled with dimethyl reagents and enriched by lectin AANL6, then the deglycosylated peptides were identified by LC-MS/MS. Differentially expressed proteins were used for further exploration. In the validation cohort, we used 90 newly diagnosed patients with MM and 70 cases of unrelated diseases as controls. The diagnosis performance was analysed by ROC analysis using SPSS.

RESULTS

In this study, we show, using lectin blots with AANL6, that glycosylation levels were higher in MM patients than in controls. After AANL6 enrichment, we detected 58 differentially expressed proteins using quantitative proteomics. We further validated one candidate Fibulin-1 (FBLN1). Using an Elisa assay, we showed that FBLN1 expression was increased in plasma of 90 cases of MM, and which was significantly correlated with DKK1 expression. ROC analysis showed that these two markers had a 95.7% specificity for determining the diagnosis of MM.

CONCLUSION

These data suggest that the MM cases display increased glycosylation after AANL6 enrichment and that the combined expression of FBLN1 and DKK1 can be used as an effective diagnostic biomarker.

Minimal Residual Disease in Multiple Myeloma: Potential for Blood-Based Methods to Monitor Disease

In recent years, the life expectancy of Multiple Myeloma (MM) patients has substantially improved, but this cancer remains incurable with increasing incidence in the developed world. Most MM patients will eventually relapse due to residual drug-resistant cancerous cells that survive treatment, commonly referred to as minimal residual disease (MRD). Methods to improve MRD detection in MM patients are generating considerable interest as a means of monitoring patients' response to treatment. In clinical laboratories, these methods currently require bone marrow aspirates which are invasive and frequently miss detection of localised disease due to the spatial heterogeneity of disease infiltration. By simplifying serial sampling and allowing for the detection of extramedullary disease, a blood-based method could significantly impact treatment duration and intensity and minimise chemotherapy-induced toxicity. This review will describe the current blood-based techniques available to detect MRD in MM and compare their potential to evaluate patient prognosis and drive therapeutic decisions.

Stimulus-Responsive Microfluidic Interface Enables Efficient Enrichment and Cytogenetic Profiling of Circulating Myeloma Cells

Minimal residual disease (MRD) provides an independent prognostic factor for multiple myeloma (MM) patients. However, clinical MRD assays suffer from highly invasive sampling, insufficient detection sensitivity, and high cost. Herein, a stiMulus-Responsive ligand-Decorated microfluidic chip (MRD-Chip) was developed for efficient capture and controlled release of circulating myeloma cells (CMCs) in the peripheral blood for noninvasive myeloma evaluation. The CD138 antibody-decorated herringbone chip with a disulfide linker was designed to enhance the collision probability between blood cells and capture antibodies, leading to high capture efficiency of CMCs. More importantly, the captured CMCs can be nondestructively released via a thiol-exchange reaction, allowing them to be used for subsequent cellular and molecular analysis. By fluorescence in situ hybridization assay, we successfully identified the cytogenetic abnormalities (chromosome 1q21 amplification and p53 deletion) of CMCs in clinical samples. Overall, with the merits of noninvasive sampling, high capture efficiency (70.93%), high throughput (1.5 mL/h), and nondestructive release of target cells (over 90% viability) for downstream analysis, our strategy provides new opportunities for myeloma evaluation, such as prognosis assessment, efficacy monitoring, and mechanism research of disease relapse and drug resistance.

Circulating Plasma Cells as a Biomarker to Predict Newly Diagnosed Multiple Myeloma Prognosis: Developing Nomogram Prognostic Models

Background: To investigate the prognostic value of circulating plasma cells (CPC) and establish novel nomograms to predict individual progression-free survival (PFS) as well as overall survival (OS) of patients with newly diagnosed multiple myeloma (NDMM).

Methods: One hundred ninetyone NDMM patients in Wuhan Union Hospital from 2017.10 to 2020.8 were included in the study. The entire cohort was randomly divided into a training (n = 130) and a validation cohort (n = 61). Univariate and multivariate analyses were performed on the training cohort to establish nomograms for the prediction of survival outcomes, and the nomograms were validated by calibration curves.

Results: When the cut-off value was 0.038%, CPC could well distinguish patients with higher tumor burden and lower response rates (P < 0.05), and could be used as an independent predictor of PFS and OS. Nomograms predicting PFS and OS were developed according to CPC, lactate dehydrogenase (LDH) and creatinine. The C-index and the area under receiver operating characteristic curves (AUC) of the nomograms showed excellent individually predictive effects in training cohort, validation cohort or entire cohort. Patients with total points of the nomograms ≤ 60.7 for PFS and 75.8 for OS could be defined as low-risk group and the remaining as high-risk group. The 2-year PFS and OS rates of patients in low-risk group was significantly higher than those in high-risk group (p < 0.001).

Conclusions: CPC is an independent prognostic factor for NDMM patients. The proposed nomograms could provide individualized PFS and OS prediction and risk stratification.

Functional Genomics Identify Distinct and Overlapping Genes Mediating Resistance to Different Classes of Heterobifunctional Degraders of Oncoproteins

Heterobifunctional proteolysis-targeting chimeric compounds leverage the activity of E3 ligases to induce degradation of target oncoproteins and exhibit potent preclinical antitumor activity. To dissect the mechanisms regulating tumor cell sensitivity to different classes of pharmacological "degraders" of oncoproteins, we performed genome-scale CRISPR-Cas9-based gene editing studies. We observed that myeloma cell resistance to degraders of different targets (BET bromodomain proteins, CDK9) and operating through CRBN (degronimids) or VHL is primarily mediated by prevention of, rather than adaptation to, breakdown of the target oncoprotein; and this involves loss of function of the cognate E3 ligase or interactors/regulators of the respective cullin-RING ligase (CRL) complex. The substantial gene-level differences for resistance mechanisms to CRBN- versus VHL-based degraders explains mechanistically the lack of cross-resistance with sequential administration of these two degrader classes. Development of degraders leveraging more diverse E3 ligases/CRLs may facilitate sequential/alternating versus combined uses of these agents toward potentially delaying or preventing resistance.

Adhesion molecule immunophenotype of bone marrow multiple myeloma plasma cells impacts the presence of malignant circulating plasma cells in peripheral blood

INTRODUCTION

Multiple myeloma (MM) patients with malignant plasma cells (MMPCs) in their bone marrow (BM) and malignant circulating plasma cells (MMCPCs) in the peripheral blood (PB) are an independent marker of a clinically aggressive disease, and it reflects a poor prognosis defined by a short time to progression and overall survival. We hypothesized that changes in ADM expression on BM MMPCs might contribute to MMCPC presence in the PB of relapsed/refractory multiple myeloma (RRMM) patients.

METHODS

We assessed the difference in expression of adhesion molecules and receptors related to cell-cell interaction: integrins, hyaluronic acid receptors, chemokine receptors and other proteins on healthy donor PCs, RRMM BM and PB MMPCs.

RESULTS

Adhesion immunophenotype showed a significant loss of many adhesion molecules when comparing BM MMPCs of MMCPC- and MMCPC+ MM patients (CD49d, CD49e, CD56, CD138). Further decrease of adhesion molecules was shown in MMCPCs (CD49d, CD49e, CD56, CD138, CD58), suggesting that loss of these molecules may allow cells to leave the BM.

CONCLUSIONS

Loss of adhesion molecule expression enables MMPCs to leave the BM milieu and enter the PB. These changes can be seen in both the PB and BM of MMCPC+ MM patient.

Detection of Circulating Tumor Plasma Cells in Monoclonal Gammopathies: Methods, Pathogenic Role, and Clinical Implications

Cancer dissemination and distant metastasis most frequently require the release of tumor cells into the blood circulation, both in solid tumors and most hematological malignancies, including plasma cell neoplasms. However, detection of blood circulating tumor cells in solid tumors and some hematological malignancies, such as the majority of mature/peripheral B-cell lymphomas and monoclonal gammopathies, has long been a challenge due to their very low frequency. In recent years, the availability of highly-sensitive and standardized methods for the detection of circulating tumor plasma cells (CTPC) in monoclonal gammopathies, e.g., next-generation flow cytometry (NGF), demonstrated the systematic presence of CTPC in blood in virtually every smoldering (SMM) and symptomatic multiple myeloma (MM) patient studied at diagnosis, and in the majority of patients with newly-diagnosed monoclonal gammopathies of undetermined significance (MGUS). These methods set the basis for further detailed characterization of CTPC vs. their bone marrow counterpart in monoclonal gammopathies, to investigate their role in the biology of the disease, and to confirm their strong impact on patient outcome when measured both at diagnosis and after initiating therapy. Here, we review the currently available techniques for the detection of CTPC, and determine their biological features, physiopathological role and clinical significance in patients diagnosed with distinct diagnostic categories of plasma cell neoplasms.

Minimal Residual Disease in Multiple Myeloma: Current Landscape and Future Applications With Immunotherapeutic Approaches

The basic principle that deeper therapeutic responses lead to better clinical outcomes in cancer has emerged technologies capable of detecting rare residual tumor cells. The need for ultra-sensitive approaches for minimal residual disease (MRD) detection is particularly evident in Multiple Myeloma (MM), where patients will ultimately relapse despite the achievement of complete remission, which is commonplace due to remarkable therapeutic advances. Consequently, current response criteria on MM have been amended based on MRD status and MRD negativity is now considered the most dominant prognostic factor and the most valuable indicator for a subsequent relapse. However, there are particular limitations and several aspects for MRD assessment that remain open. This review summarizes current data on MRD in the clinical management of MM, highlights open issues and discusses the challenges and the endless opportunities arising for both patients and clinicians. Furthermore, it focuses on the current status of MRD in clinical trials, its dynamics in addressing debatable aspects in the clinical handling and its potential role as the prevailing factor for future MRD-driven tailored therapies.

Liquid biopsies for multiple myeloma in a time of precision medicine

Multiple myeloma (MM) is a challenging, progressive, and highly heterogeneous hematological malignancy. MM is characterized by multifocal proliferation of neoplastic plasma cells in the bone marrow (BM) and sometimes in extramedullary organs. Despite the availability of novel drugs and the longer median overall survival, some patients survive more than 10 years while others die rapidly. This heterogeneity is mainly driven by biological characteristics of MM cells, including genetic abnormalities. Disease progressions are mainly due to the inability of drugs to overcome refractory disease and inevitable drug-resistant relapse. In clinical practice, a bone marrow biopsy, mostly performed in one site, is still used to access the genetics of MM. However, BM biopsy use is limited by its invasive nature and by often not accurately reflecting the mutational profile of MM. Recent insights into the genetic landscape of MM provide a valuable opportunity to implement precision medicine approaches aiming to enable better patient profiling and selection of targeted therapies. In this review, we explore the use of the emerging field of liquid biopsies in myeloma patients considering current unmet medical needs, such as assessing the dynamic mutational landscape of myeloma, early predictors of treatment response, and a less invasive response monitoring.

Enrichment of circulating myeloma cells by immunomagnetic beads combined with flow cytometry for monitoring minimal residual disease and relapse in patients with multiple myeloma

Difficulty in regularly analyzing marrow myeloma cells (MMCs) and low frequency of circulating myeloma cells (CMCs) in blood presents challenges for monitoring minimal residual disease (MRD) in multiple myeloma (MM). We have developed a set of method for enrichment of CMCs by immunomagetic beads (IMB) combined with flow cytometry (IMB-FCM) based on CD38-APC/CD138-APC antibodies in U266-spiked samples and in 122 patient samples. U266 cell capture efficiency of CD38/CD138-IMB-FCM (6.960, 2.574) was 6- and 2-fold higher than that of FCM (1.032), and the sensitivity of FCM and IMB-FCM was 0.01% and 0.001%, respectively. In MM cohort, the positive rate of CMCs by IMB-FCM increased from 60.5~70.0 to 85~87.2% in newly diagnosed/relapsed and partial remission (PR) patients compared with by FCM (P < 0.05). Two complete remission (CR) patients contain certain amounts of CMCs by IMB-FCM while no CMCs and MMCs were detectable by FCM. Patients exhibiting PR and CR upon therapy had much lower CMC and MMC counts than newly diagnosed/relapsed patients (P < 0.005). Based on MRD measurement in BM and PB samples, all FCM-negative BM samples were also paired with FCM/IMB-FCM-negative PB samples among newly diagnosed, relapsed, and PR patients, and FCM-positive BM samples were accompanied by IMB-FCM-positive results in 88% of corresponding PB samples. CMCs strongly associated with other clinical biomarkers of disease burden, including elevated MMCs, β2-MG, sCrea, and DS and ISS stages, and more serious anemia, bone destruction, and renal impairment (P < 0.05). Logistic regression analysis revealed that elevated β2-MG and moderate-to-more anemia were significant risk factors for the presence of CMCs (P < 0.05). As a noninvasive "liquid biopsy" of monitoring MRD, the potential of IMB-FCM for CMC detection may complement or minimize bone marrow aspiration in future treatment of MM patients.

Mechanical segregation and capturing of clonal circulating plasma cells in multiple myeloma using micropillar-integrated microfluidic device

Multiple myeloma (MM), the disorder of plasma cells, is the second most common type of hematological cancer and is responsible for approximately 20% of deaths from hematological malignancies. The current gold standard for MM diagnosis includes invasive bone marrow aspiration. However, it lacks the sensitivity to detect minimal residual disease, and the nonuniform distribution of clonal plasma cells (CPCs) within bone marrow also often results in inaccurate reporting. Serum and urine assessment of monoclonal proteins, such as Kappa light chains, is another commonly used approach for MM diagnosis. Although it is noninvasive, the level of paraprotein elevation is still too low for detecting minimal residual disease and nonsecretive MM. Circulating CPCs (cCPCs) have been reported to be present in the peripheral blood of MM patients, and high levels of cCPCs were shown to correlate with poor survival. This suggests a potential noninvasive approach for MM disease progress monitoring and prognosis. In this study, we developed a mechanical property-based microfluidic platform to capture cCPCs. Using human myeloma cancer cell lines spiked in healthy donor blood, the microfluidic platform demonstrates high enrichment ratio (>500) and sufficient capture efficiency (40%-55%). Patient samples were also assessed to investigate the diagnostic potential of cCPCs for MM by correlating with the levels of Kappa light chains in patients.

Transcriptional profiling of circulating tumor cells in multiple myeloma: a new model to understand disease dissemination

The reason why a few myeloma cells egress from the bone marrow (BM) into peripheral blood (PB) remains unknown. Here, we investigated molecular hallmarks of circulating tumor cells (CTCs) to identify the events leading to myeloma trafficking into the bloodstream. After using next-generation flow to isolate matched CTCs and BM tumor cells from 32 patients, we found high correlation in gene expression at single-cell and bulk levels (r ≥ 0.94, P = 10^-16), with only 55 genes differentially expressed between CTCs and BM tumor cells. CTCs overexpressed genes involved in inflammation, hypoxia, or epithelial-mesenchymal transition, whereas genes related with proliferation were downregulated in CTCs. The cancer stem cell marker CD44 was overexpressed in CTCs, and its knockdown significantly reduced migration of MM cells towards SDF1-α and their adhesion to fibronectin. Approximately half (29/55) of genes differentially expressed in CTCs were prognostic in patients with newly-diagnosed myeloma (n = 553; CoMMpass). In a multivariate analysis including the R-ISS, overexpression of CENPF and LGALS1 was significantly associated with inferior survival. Altogether, these results help understanding the presence of CTCs in PB and suggest that hypoxic BM niches together with a pro-inflammatory microenvironment induce an arrest in proliferation, forcing tumor cells to circulate in PB and seek other BM niches to continue growing.

Minimal Residual Disease Assessment Within the Bone Marrow of Multiple Myeloma: A Review of Caveats, Clinical Significance and Future Perspectives

There is an increasing clinical interest in the measure and achievement of minimal residual disease (MRD) negativity in the bone marrow of Multiple Myeloma (MM) patients, as defined equally either by Multicolor Flow Cytometry (MFC) or by Next Generation Sequencing (NGS) technologies. At present, modern technologies allow to detect up to one on 104 or on 105 or even on 106 cells, depending on their throughput. MFC approaches, which have been progressively improved up to the so-called Next Generation Flow (NGF), and NGS, which proved clear advantages over ASO-PCR, can detect very low levels of residual disease in the BM. These methods are actually almost superimposable, in terms of MRD detection power, supporting the lack of unanimous preference for either technique on basis of local availability. However, some technical issues are still open: the optimal assay to use to detect either phenotype (e.g., next generation multidimensional flow cytometry, imaging) or genotype aberrations (e.g., ASO-RQ PCR, digital droplet PCR, NGS) and their standardization, the sample source (BM or peripheral blood, PB) and its pre-processing (red-cell lysis vs. Ficoll, fresh vs. frozen samples, requirement of CD138+ cells enrichment). Overall, MRD negativity is considered as the most powerful predictor of favorable long-term outcomes in MM and is likely to represent the major driver of treatment strategies in the near future. In this manuscript, we reviewed the main pitfalls and caveats of MRD detection within bone marrow in MM patients after front-line therapy, highlighting the improving of the currently employed technology and describing alternative methods for MRD testing in MM, such as liquid biopsy.

Potential Clinical Application of Genomics in Multiple Myeloma

Multiple myeloma is a heterogeneous disease with different characteristics, and genetic aberrations play important roles in this heterogeneity. Studies have shown that these genetic aberrations are crucial in prognostication and response assessment; recent efforts have focused on their possible therapeutic implications. Despite many emerging studies being published, the best way to incorporate these results into clinical practice remains unclear. In this review paper we describe the different genomic techniques available, including the latest advancements, and discuss the potential clinical application of genomics in multiple myeloma.

Comprehensive characterization of circulating and bone marrow-derived multiple myeloma cells at minimal residual disease

The presence or absence of minimal residual disease (MRD) in patients with multiple myeloma (MM) has emerged as a useful marker to determine the depth of remission. MRD negativity as an endpoint has been shown to be associated with improved progression-free survival in many studies. MRD detection is therefore part of numerous clinical trial protocols for MM. At the present time, two methodologies are most widely accepted for MRD detection: (1) multicolor flow cytometry and (2) next-generation sequencing-based clonotype detection. While both of those methodologies enable accurate quantification of MRD in the bone marrow (BM), with sensitivity as low as 10^-5 to 10^-6, there are several limitations to these methods. First, these approaches reveal the presence or absence of MRD but provide limited molecular information about MM. More comprehensive characterization of MM cells at the MRD stage may identify molecular mechanisms of drug resistance. Second, MRD detection in the BM is typically performed at one time point only, but more frequent detection may define the duration of the MRD status and thus refine its prognostic value. Third, less-invasive approaches that avoid the discomfort and risk associated with BM biopsy would be highly desirable, especially in elderly or frail patients. "Liquid biopsy" for the detection and characterization of circulating MM cells may address these issues. Although MRD detection in the peripheral blood at the same sensitivity as in the BM may be challenging, the identification of patients who do not achieve MRD negativity might reduce the need for BM biopsies. Here, we give an overview of approaches that have been described to detect and characterize MM cells when they occur at very low frequencies in the peripheral blood or in the BM, emphasizing recently described next-generation sequencing approaches for more comprehensive characterization of circulating MM cells.

Isolation of circulating plasma cells from blood of patients diagnosed with clonal plasma cell disorders using cell selection microfluidics

Blood samples from patients with plasma cell disorders were analysed for the presence of circulating plasma cells (CPCs) using a microfluidic device modified with monoclonal anti-CD138 antibodies. CPCs were immuno-phenotyped using a CD38/CD56/CD45 panel and identified in 78% of patients with monoclonal gammopathy of undetermined significance (MGUS), all patients with smouldering and symptomatic multiple myeloma (MM), and none in the controls. The burden of CPCs was higher in patients with symptomatic MM compared with MGUS and smouldering MM (p < 0.05). FISH analysis revealed the presence of chromosome 13 deletions in CPCs that correlated with bone marrow results. Point mutations in KRAS were identified, including different mutations from sub-clones derived from the same patient. The microfluidic assay represents a highly sensitive method for enumerating CPCs and allows for the cytogenetic and molecular characterization of CPCs.