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This study was supported by the Centro de Investigación Biomédica en Red—Área de Oncología—del Instituto de Salud Carlos III (CIBERONC; CB16/12/00369; and CB16/12/00489), Instituto de Salud Carlos III/Subdirección General de Investigación Sanitaria (FIS No. PI13/02196), Asociación Española Contra el Cáncer (GCB120981SAN and the Accelerator Award), CRIS against Cancer foundation grant 2014/0120, and the Black Swan Research Initiative of the International Myeloma Foundation.

This article belongs to the Special Issue Advances in Multiple Myeloma Research and Treatment., [Simple Summary] Although the majority of patients with myeloma who achieve undetectable minimal residual disease show prolonged survival, some of them relapse shortly afterwards. False-negative results due to hemodiluted bone marrow samples could explain this inconsistency, but there is no guidance on how to evaluate them. We analyzed three cell populations normally absent in peripheral blood in 1404 aspirates obtained in numerous disease settings and in 85 healthy adults. Pairwise comparisons according to age and treatment showed significant variability, thus suggesting that hemodilution should be preferably evaluated with references obtained after receiving identical regimens. Leveraging the minimal residual disease results from 118 patients, we showed that a comparison with age-matched healthy adults could also inform on potential hemodilution. Our study supports the routine assessment of bone marrow cellularity to evaluate hemodilution, using as reference values either treatment-specific or from healthy adults if the former are unavailable., [Abstract] Background: Whereas, in most patients with multiple myeloma (MM), achieving undetectable MRD anticipates a favorable outcome, some others relapse shortly afterwards. Although one obvious explanation for this inconsistency is the use of nonrepresentative marrow samples due to hemodilution, there is no guidance on how to evaluate this issue. Methods: Since B-cell precursors, mast cells and nucleated red blood cells are normally absent in peripheral blood, we analyzed them in 1404 bone marrow (BM) aspirates obtained in numerous disease settings and in 85 healthy adults (HA). Results: First, we confirmed the systematic detection of the three populations in HA, as well as the nonreduced numbers with aging. Pairwise comparisons between HA and MM patients grouped according to age and treatment showed significant variability, suggesting that hemodilution should be preferably evaluated with references obtained from patients treated with identical regimens. Leveraging the MRD results from 118 patients, we showed that a comparison with HA of similar age could also inform on potential hemodilution. Conclusions: Our study supports the routine assessment of BM cellularity to evaluate hemodilution, since reduced BM-specific cell types as compared to reference values (either treatment-specific or from HA if the former are unavailable) could indicate hemodilution and a false-negative MRD result., This study was supported by grants from the Centro de Investigación Biomédica en Red—Área de Oncología—del Instituto de Salud Carlos III (CIBERONC; CB16/12/00369, CB16/12/00400, CB16/12/00233 and CB16/12/00284); Instituto de Salud Carlos III/Subdirección General de Investigación Sanitaria and co-financed by FEDER funds (FIS No. PI15/01956, PI15/02049, PI15/02062, PI18/01709, PI18/01673 and PI19/01451); the Cancer Research UK (C355/A26819), FCAECC and AIRC under the Accelerator Award Programme (EDITOR); the Black Swan Research Initiative of the International Myeloma Foundation and the European Research Council (ERC) 2015 Starting Grant (Contract 680200 MYELOMANEXT). This study was supported by the Riney Family Multiple Myeloma Research Program Fund.

© 2021 by the authors., Monocyte/macrophages have been shown to be altered in monoclonal gammopathy of undetermined significance (MGUS), smoldering (SMM) and active multiple myeloma (MM), with an impact on the disruption of the homeostasis of the normal bone marrow (BM) microenvironment., This research was funded by the Biomedical Research Networking Center Consortium CIBER-CIBERONC (CB16/12/00400, CB16/12/00369 and CB16/12/00233-FEDER), PI13/01412- FEDER, from the Instituto de Salud Carlos III (ISCIII), Ministerio de Economía y Competitividad, Madrid, Spain; the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (grant agreement ERC-2015-AdG 695655 (TiMaScan); and the Black Swan Research Initiative of the International Myeloma Foundation (Los Angeles, CA, USA), (grant IMF13/IMF16)

© The Author(s) 2021., Light chain (AL) amyloidosis is caused by a small B-cell clone producing light chains that form amyloid deposits and cause organ dysfunction. Chemotherapy aims at suppressing the production of the toxic light chain (LC) and restore organ function. However, even complete hematologic response (CR), defined as negative serum and urine immunofixation and normalized free LC ratio, does not always translate into organ response. Next-generation flow (NGF) cytometry is used to detect minimal residual disease (MRD) in multiple myeloma. We evaluated MRD by NGF in 92 AL amyloidosis patients in CR. Fifty-four percent had persistent MRD (median 0.03% abnormal plasma cells). There were no differences in baseline clinical variables in patients with or without detectable MRD. Undetectable MRD was associated with higher rates of renal (90% vs 62%, p = 0.006) and cardiac response (95% vs 75%, p = 0.023). Hematologic progression was more frequent in MRD positive (0 vs 25% at 1 year, p = 0.001). Altogether, NGF can detect MRD in approximately half the AL amyloidosis patients in CR, and persistent MRD can explain persistent organ dysfunction. Thus, this study supports testing MRD in CR patients, especially if not accompanied by organ response. In case MRD persists, further treatment could be considered, carefully balancing residual organ damage, patient frailty, and possible toxicity., This study was supported by a grant from CARIPLO “Molecular mechanisms of Ig toxicity in age-related plasma cell dyscrasias no. 2015-0591”, by a grant from the Black Swan Research Initiative from the International Myeloma Foundation “Automated multidimensional flow cytometry for high-sensitive screening and to monitor response in AL amyloidosis”, by a grant from CARIPLO “Structure–function relation of amyloid: understanding the molecular bases of protein misfolding diseases to design new treatments no. 2013-0964”, by a grant from the Amyloidosis Foundation “Investigating new therapies to treat AL amyloidosis”, and by a grant from Cancer Research UK, FCAECC and AIRC under the Accelerator Award 2017 Program “Early detection and intervention: understanding the mechanisms of transformation and hidden resistance of incurable hematological malignancies”, by a grant from CARIPLO “Harnessing the plasma cell secretory capacity against systemic light chain amyloidosis” (no. 2018-0257), by a grant from the Italian Ministry of Health “Towards effective, patient-tailored anti-plasma cell therapies in AL amyloidosis: predicting drug response and overcoming drug resistance” (GR-2018-12368387). This study has also supported the Centro de Investigación Biomédica en Red—Área de Oncología—del Instituto de Salud Carlos III (CIBERONC; CB16/12/00369, CB16/12/00400, and CB16/12/00489) and the Instituto de Salud Carlos III/Subdirección General de Investigación Sanitaria (FIS No. PI13/02196). G.P. is supported in part by the Bart Barlogie Young Investigator Award from the International Myeloma Society (IMS). P.M. is supported in part by a fellowship grant form Collegio Ghislieri (Pavia). We acknowledge the study coordinator and data manager Anna Carnevale Baraglia.

© 2021 by the authors., B-cell regeneration during therapy has been considered as a strong prognostic factor in multiple myeloma (MM). However, the effects of therapy and hemodilution in bone marrow (BM) B-cell recovery have not been systematically evaluated during follow-up. MM (n = 177) and adult (≥50y) healthy donor (HD; n = 14) BM samples were studied by next-generation flow (NGF) to simultaneously assess measurable residual disease (MRD) and residual normal B-cell populations. BM hemodilution was detected in 41 out of 177 (23%) patient samples, leading to lower total B-cell, B-cell precursor (BCP) and normal plasma cell (nPC) counts. Among MM BM, decreased percentages (vs. HD) of BCP, transitional/naïve B-cell (TBC/NBC) and nPC populations were observed at diagnosis. BM BCP increased after induction therapy, whereas TBC/NBC counts remained abnormally low. At day+100 postautologous stem cell transplantation, a greater increase in BCP with recovered TBC/NBC cell numbers but persistently low memory B-cell and nPC counts were found. At the end of therapy, complete response (CR) BM samples showed higher CD19− nPC counts vs. non-CR specimens. MRD positivity was associated with higher BCP and nPC percentages. Hemodilution showed a negative impact on BM B-cell distribution. Different BM B-cell regeneration profiles are present in MM at diagnosis and after therapy with no significant association with patient outcome., This work has been supported by the International Myeloma Foundation-Black Swan Research Initiative, the EuroFlow Consortium (grant LSHB-CT-2006-018708); Centro de Investigación Biomédica en Red de Cáncer (CIBER-ONC; Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain and FONDOS FEDER), numbers: CB16/12/00400, CB16/12/00233, CB16/12/00369, CB16/12/00489 and CB16/12/00480; grant from Bilateral Cooperation Program between Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-CAPES (Brasília/Brazil) and Dirección General de Políticas Universitárias (DGPU)-Ministério de Educación, Cultura y Deportes (Madrid/Spain) number DGPU 311/15; Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro of Brazil (FAPERJ) numbers: E26/110.105/2014 and E26/102.191/2013; grant from Conselho Nacional de Desenvolvimento Científico e Tecnológico of Brazil (CNPQ), number: 400194/2014-7. R.M.d.P. was supported by a grant from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES/DGPU), number: 000281/2016-06 and CAPES/PROEX 641/2018, Brazil; Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro of Brazil (FAPERJ) number: E01/200/537/2018.

The search for biomarkers based on the mechanism of drug action has not been thoroughly addressed in the therapeutic approaches to multiple myeloma (MM), mainly because of the difficulty in analyzing proteins obtained from purified plasma cells. Here, we investigated the prognostic impact of the expression of 12 proteins involved in the mechanism of action of bortezomib, lenalidomide, and dexamethasone (VRD), quantified by capillary nanoimmunoassay, in CD138-purified samples from 174 patients with newly diagnosed MM treated according to the PETHEMA/GEM2012 study. A high level of expression of 3 out of 5 proteasome components tested (PSMD1, PSMD4, and PSMD10) negatively influenced survival. The 5 analyzed proteins involved in lenalidomide’s mode of action were associated with time to progression (TTP); low levels of cereblon and IRF4 protein and high levels of Ikaros, AGO2, and Aiolos were significantly associated with shorter TTP. Although the glucocorticoid receptor (GCR) level by itself had no significant impact on MM prognosis, a high XPO1 (exportin 1)/GCR ratio was associated with shorter TTP and progression-free survival (PFS). The multivariate Cox model identified high levels of PSMD10 (hazard ratio [HR] TTP, 3.49; P = .036; HR PFS, 5.33; P = .004) and Ikaros (HR TTP, 3.01, P = .014; HR PFS, 2.57; P = .028), and low levels of IRF4 protein expression (HR TTP, 0.33; P = .004; HR PFS, 0.35; P = .004) along with high-risk cytogenetics (HR TTP, 3.13; P < .001; HR PFS, 2.69; P = .002), as independently associated with shorter TTP and PFS. These results highlight the value of assessing proteins related to the mechanism of action of drugs used in MM for predicting treatment outcome., This study was funded by the Instituto de Salud Carlos III, cofinanced by FEDER grant PI16/01074; the Gerencia Regional de Salud, Junta de Castilla y Leon grants GRS1654/A/17, GRS1849/ ´ A/18, and GRS2058/A/19; and a Brian D. Novis, Black Swan Research Initiative research grant from the International Myeloma Foundation. The WES platform was acquired thanks to the INNOCAMPUS program (CEI10-1-0010).

© The Author(s) 2020., Smoldering multiple myeloma (SMM) is an asymptomatic precursor state of multiple myeloma (MM). Recently, MM was redefined to include biomarkers predicting a high risk of progression from SMM, thus necessitating a redefinition of SMM and its risk stratification. We assembled a large cohort of SMM patients meeting the revised IMWG criteria to develop a new risk stratification system. We included 1996 patients, and using stepwise selection and multivariable analysis, we identified three independent factors predicting progression risk at 2 years: serum M-protein >2 g/dL (HR: 2.1), involved to uninvolved free light-chain ratio >20 (HR: 2.7), and marrow plasma cell infiltration >20% (HR: 2.4). This translates into 3 categories with increasing 2-year progression risk: 6% for low risk (38%; no risk factors, HR: 1); 18% for intermediate risk (33%; 1 factor; HR: 3.0), and 44% for high risk (29%; 2–3 factors). Addition of cytogenetic abnormalities (t(4;14), t(14;16), +1q, and/or del13q) allowed separation into 4 groups (low risk with 0, low intermediate risk with 1, intermediate risk with 2, and high risk with ≥3 risk factors) with 6, 23, 46, and 63% risk of progression in 2 years, respectively. The 2/20/20 risk stratification model can be easily implemented to identify high-risk SMM for clinical research and routine practice and will be widely applicable., The data collection study was conducted by the International Myeloma Foundation as an International Myeloma Working Group project supported in part by a grant funded by Janssen.

Multiple myeloma (MM) patients undergo repetitive bone marrow (BM) aspirates for genetic characterization. Circulating tumor cells (CTCs) are detectable in peripheral blood (PB) of virtually all MM cases and are prognostic, but their applicability for noninvasive screening has been poorly investigated. Here, we used next-generation flow (NGF) cytometry to isolate matched CTCs and BM tumor cells from 53 patients and compared their genetic profile. In eight cases, tumor cells from extramedullary (EM) plasmacytomas were also sorted and whole-exome sequencing was performed in the three spatially distributed tumor samples. CTCs were detectable by NGF in the PB of all patients with MM. Based on the cancer cell fraction of clonal and subclonal mutations, we found that ~22% of CTCs egressed from a BM (or EM) site distant from the matched BM aspirate. Concordance between BM tumor cells and CTCs was high for chromosome arm-level copy number alterations (≥95%) though not for translocations (39%). All high-risk genetic abnormalities except one t(4;14) were detected in CTCs whenever present in BM tumor cells. Noteworthy, ≥82% mutations present in BM and EM clones were detectable in CTCs. Altogether, these results support CTCs for noninvasive risk-stratification of MM patients based on their numbers and genetic profile., This study was supported by the Centro de Investigación Biomédica en Red—Área de Oncología—del Instituto de Salud Carlos III (CIBERONC; CB16/12/00236, CB16/12/00369, CB16/12/00489, and CB16/12/00400); by Cancer Research UK [C355/A26819] and FC AECC and AIRC under the Accelerator Award Program; by the Instituto de Salud Carlos III, FCAECC and co-financed by FEDER (ERANET-TRANSCAN-2 iMMunocell AC17/00101); the Spanish Ministry of Science and Innovation and co-financed by FSE (Torres Quevedo fellowship, PTQ-16-08623); the Black Swan Research Initiative of the International Myeloma Foundation; European Research Council (ERC) under the European Commission’s H2020 Framework Programme (MYELOMANEXT, 680200); the Qatar National Research Fund (QNRF) Award No. 7-916-3-237; the AACR-Millennium Fellowship in Multiple Myeloma Research (15-40-38-PAIV); the Leukemia Research Foundation; and the Multiple Myeloma Research Foundation (MMRF) under the 2019 Research Fellowship Award.

36 p.-6 fig., The interaction of multiple myeloma (MM) cells with the bone marrow (BM) microenvironment promotes MM cell retention, survival and resistance to different anti‐MM agents, including proteasome inhibitors (PIs) such as bortezomib (BTZ). The α4β1 integrin is a main adhesion receptor mediating MM cell‐stroma interactions and MM cell survival, and its expression and function are downregulated by BTZ, leading to inhibition of cell adhesion‐mediated drug resistance (CAM‐DR) and MM cell apoptosis. Whether decreased α4β1 expression and activity is maintained or recovered upon development of resistance to BTZ represents an important question, as a potential rescue of α4β1 function could boost MM cell survival and disease progression. Using BTZ‐resistant MM cells, we found that they not only rescue their α4β1 expression, but its levels were higher than in parental cells. Increased α4β1 expression in resistant cells correlated with enhanced α4β1‐mediated cell lodging in the BM, and with disease progression. BTZ‐resistant MM cells displayed enhanced NF‐κB pathway activation relative to parental counterparts, which contributed to upregulated α4 expression and to α4β1‐dependent MM cell adhesion. These data emphasize the upregulation of α4β1 expression and function as a key event during resistance to BTZ in MM, which might indirectly contribute to stabilize this resistance, as stronger MM cell attachment to BM stroma will regain CAM‐DR and MM cell growth and survival. Finally, we found a strong correlation between high ITGB1 (integrin β1) expression in MM and poor progression‐free survival (PFS) and overall survival (OS) during treatment of MM patients with BTZ and IMIDs, and combination of high ITGB1 levels and presence of the high‐risk genetic factor amp1q causes low PFS and OS. These results unravel a novel prognostic value for ITGB1 in myeloma., This work was supported by grants SAF2014-53059-R and SAF2017-85146-R from the Ministerio de Ciencia, Innovación y Universidades (MCIU) to JT; SAF2017-89672-R from MCIU to FM; by the Research Institute Hospital 12 de Octubre (i+12) and grants from Instituto de Salud Carlos III (ISCIII) and CIBERONC to JML; by grants from ISCIII PI16/02024,PI17/00701 and PI19/01352, TRASCAN (EPICA and Immunocell), Fundació La Marató de TV3, the Accelerator award CRUK/AIRC/AECC joint funder-partnership, CIBERONC(CB16/12/00489) and co-financed with FEDER funds MINECO Explora (RTHALMY),Gobierno de Navarra, Departamento de Salud 40/2016 and Departamento de Industria (Proyecto Estrategico, Reto Genomica, DIANA) and Fundación Ramón Areces (PREMAMM) to FP and XA The study was also supported by the Multiple Myeloma Research Foundation Networks of excellence, the International Myeloma Foundation (Brian van Novis), and the Qatar National Research Fund award 7-916-3-237.

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., This study was supported by the Centro de Investigación Biomédica en Red —Área de Oncología— del Instituto de Salud Carlos III (CIBERONC; CB16/12/00369, CB16/12/00489, and CB16/12/00400), Cancer Research UK, FCAECC and AIRC under the Accelerator Award Programme, Instituto de Salud Carlos III and Asociación Española Contra el Cáncer by ERA-NET TRANSCAN-2 Programme (AC17/00101), the Black Swan Research Initiative of the International Myeloma Foundation, the European Research Council (ERC) 2015 Starting Grant (MYELOMANEXT, 680200), the Czech Science Foundation through Project No. 19-25354Y, the European Regional Development Fund—Project ENOCH (No. CZ.02.1.01/0.0/0.0/16_019/0000868), and the Ministry of Health of the Czech Republic (15-29667A).

Early diagnosis and risk stratification are key to improve outcomes in light-chain (AL) amyloidosis. Here we used multidimensional-flow-cytometry (MFC) to characterize bone marrow (BM) plasma cells (PCs) from a series of 166 patients including newly-diagnosed AL amyloidosis (N = 94), MGUS (N = 20) and multiple myeloma (MM, N = 52) vs. healthy adults (N = 30). MFC detected clonality in virtually all AL amyloidosis (99%) patients. Furthermore, we developed an automated risk-stratification system based on BMPCs features, with independent prognostic impact on progression-free and overall survival of AL amyloidosis patients (hazard ratio: ≥ 2.9;P ≤.03). Simultaneous assessment of the clonal PCs immunophenotypic protein expression profile and the BM cellular composition, mapped AL amyloidosis in the crossroad between MGUS and MM; however, lack of homogenously-positive CD56 expression, reduction of B-cell precursors and a predominantly-clonal PC compartment in the absence of an MM-like tumor PC expansion, emerged as hallmarks of AL amyloidosis (ROC-AUC = 0.74;P, This study was supported by the Centro de Investigación Biomédica en Red – Área de Oncología—del Instituto de Salud Carlos III (CIBERONC; CB16/12/00369, CB16/12/00400 and CB16/12/00489), Instituto de Salud Carlos III/Subdirección General de Investigación Sanitaria (FIS No. PI13/02196), Asociación Española Contra el Cáncer (GCB120981SAN and Accelerator Award), the Black Swan Research Initiative of the International Myeloma Foundation, and the European Research Council (ERC) 2015 Starting Grant (MYELOMANEXT).

Protein analysis in bone marrow samples from patients with multiple myeloma has been limited by the low concentration of proteins obtained after CD138 cell selection. A novel approach based on capillary nano-immunoassay could make it possible to quantify dozens of proteins from each myeloma sample in an automated manner. Here we present a method for the accurate and robust quantification of the expression of multiple proteins extracted from CD138-purified multiple myeloma samples frozen in RLT Plus buffer, which is commonly used for nucleic acid preservation and isolation. Additionally, the biological and clinical value of this analysis for a panel of 12 proteins essential to the pathogenesis of multiple myeloma was evaluated in 63 patients with newly diagnosed multiple myeloma. The analysis of the prognostic impact of CRBN/Cereblon and IKZF1/Ikaros mRNA/protein showed that only the protein levels were able to predict progression-free survival of patients; mRNA levels were not associated with prognosis. Interestingly, high levels of Cereblon and Ikaros proteins were associated with longer progression-free survival only in patients who received immunomodulatory drugs and not in those treated with other drugs. In conclusion, the capillary nano-immunoassay platform provides a novel opportunity for automated quantification of the expression of more than 20 proteins in CD138 primary multiple myeloma samples., This work was funded by a grant from the International Myeloma Foundation’s Black Swan Research Initiative® and “Gerencia Regional de Salud, Junta de Castilla y León” (BIO/SA35/14). WES™ platform was acquired thanks to INNOCAMPUS Program (CEI10-1-0010).

© The Author(s) 2018., Here, we investigated for the first time the frequency and number of circulating tumor plasma cells (CTPC) in peripheral blood (PB) of newly diagnosed patients with localized and systemic plasma cell neoplasms (PCN) using next-generation flow cytometry (NGF) and correlated our findings with the distinct diagnostic and prognostic categories of the disease. Overall, 508 samples from 264 newly diagnosed PCN patients, were studied. CTPC were detected in PB of all active multiple myeloma (MM; 100%), and smoldering MM (SMM) patients (100%), and in more than half (59%) monoclonal gammopathy of undetermined significance (MGUS) cases (p, This work has been supported by the International Myeloma Foundation-Black Swan Research Initiative and the EuroFlow Consortium; Centro de Investigación Biomédica en Red de Cáncer (CIBER-ONC; Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain and FONDOS FEDER), numbers: CB16/12/00400, CB16/12/00369, CB16/12/00489 and CB16/12/00233; grant SA079U14 from the Consejería de Educación, Junta de Castilla y León, Valladolid, Spain and; grant DTS15/00119 from Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain. Acuerdo de colaboración con Fundación de Hemoterapia y Hemodonación de Castilla y León, Valladolid, Spain. This study was also supported by the Qatar National Research Fund (QNRF) Award No. 7-916-3-237, the AACR-Millennium Fellowship in Multiple Myeloma Research (15-40-38-PAIV), ERA-NET TRANSCAN-2 (iMMunocell), by a 2017 Leonardo Grant (BZG10931) for Researchers and Cultural Creators, BBVA Foundation, and the European Research Council (ERC) 2015 Starting Grant (MYELOMANEXT).

Persistence of minimal residual disease (MRD) after treatment for myeloma predicts inferior outcomes, but within MRD-positive patients there is great heterogeneity with both early and very late relapses. Among different MRD techniques, flow cytometry provides additional information about antigen expression on tumor cells, which could potentially contribute to stratify MRD-positive patients. We investigated the prognostic value of those antigens required to monitor MRD in 1265 newly diagnosed patients enrolled in the GEM2000, GEM2005MENOS65, GEM2005MAS65 and GEM2010MAS65 protocols. Overall, CD19 pos, CD27 neg, CD38 lo, CD45 pos, CD81 pos, CD117 neg and CD138 lo expression predicted inferior outcomes. Through principal component analysis, we found that simultaneous CD38 low CD81 pos CD117 neg expression emerged as the most powerful combination with independent prognostic value for progression-free survival (HR:1.69; P=0.002). This unique phenotypic profile retained prognostic value among MRD-positive patients. We then used next-generation flow to determine antigen stability throughout the course of the disease, and found that the expression of antigens required to monitor MRD is mostly stable from diagnosis to MRD stages, except for CD81 whose expression progressively increased from baseline to chemoresistant tumor cells (14 vs 28%). Altogether, we showed that the phenotypic profile of tumor cells provides additional prognostic information, and could be used to further predict risk of relapse among MRD-positive patients., On behalf of the GEM (Grupo Español de Mieloma)/PETHEMA (Programa para el Estudio de la Terapéutica en Hemopatías Malignas) cooperative study group. This study was supported by the Centro de Investigación Biomédica en Red – Área de Oncología - del Instituto de Salud Carlos III (CIBERONC; CB16/12/00369; CB16/12/00400; CB16/12/00233; CB16/12/00284), formerly named as Cooperative Research Thematic Network (Grants No. RD12/0036/0058, RD12/0036/0048, RD12/0036/0046, and RD12/0036/0061) of the Red de Cancer (Cancer Network of Excellence); Instituto de Salud Carlos III/Subdirección General de Investigación Sanitaria; funded in part by the European Regional Development Fund (FIS No. 98/1239, 00/10160, 01/0089, 02/0089, 02/0905, G03/136, PI051284, PI06033906/1354, PS09/01897/01370, PI12/01761, PI12/ 02311, PI13/01469, PI14/01867, G03/136); Sara Borrell (No. CD13/00340); Asociación Española Contra el Cáncer (GCB120981SAN). This study was also supported internationally by the Black Swan Research Initiative of the International Myeloma Foundation, the Qatar National Research Fund (QNRF) Award No. 7-916-3-237, the AACR-Millennium Fellowship in Multiple Myeloma Research (15-40-38-PAIV), the Leukemia Research Foundation, and the European Research Council (ERC) 2015 Starting Grant (MYELOMANEXT).

Flow cytometry has become a highly valuable method to monitor minimal residual disease (MRD) and evaluate the depth of complete response (CR) in bone marrow (BM) of multiple myeloma (MM) after therapy. However, current flow-MRD has lower sensitivity than molecular methods and lacks standardization. Here we report on a novel next generation flow (NGF) approach for highly sensitive and standardized MRD detection in MM. An optimized 2-tube 8-color antibody panel was constructed in five cycles of design-evaluation-redesign. In addition, a bulk-lysis procedure was established for acquisition of ⩾107 cells/sample, and novel software tools were constructed for automatic plasma cell gating. Multicenter evaluation of 110 follow-up BM from MM patients in very good partial response (VGPR) or CR showed a higher sensitivity for NGF-MRD vs conventional 8-color flow-MRD -MRD-positive rate of 47 vs 34% (P=0.003)-. Thus, 25% of patients classified as MRD-negative by conventional 8-color flow were MRD-positive by NGF, translating into a significantly longer progression-free survival for MRD-negative vs MRD-positive CR patients by NGF (75% progression-free survival not reached vs 7 months; P=0.02). This study establishes EuroFlow-based NGF as a highly sensitive, fully standardized approach for MRD detection in MM which overcomes the major limitations of conventional flow-MRD methods and is ready for implementation in routine diagnostics., This work has been supported by the International Myeloma Foundation-Black Swan Research Initiative, the Red Temática de Investigación Cooperativa en Cáncer (RTICC); grant SA079U14 from the Consejería de Educación, Junta de Castilla y León, Valladolid, Spain and; grant DTS15/00119 from Instituto de Salud Carlos III, Ministerio de Economía y Competitividad, Madrid, Spain.

On behalf of the GEM (Grupo Español de Mieloma)/PETHEMA (Programa para el Estudio de la Terapéutica en Hemopatías Malignas) Cooperative Study Group., [Purpose]: To perform a critical analysis on the impact of depth of response in newly diagnosed multiple myeloma (MM). [Patients and Methods]: Data were analyzed from 609 patients who were enrolled in the GEM (Grupo Español de Mieloma) 2000 and GEM2005MENOS65 studies for transplant-eligible MM and the GEM2010MAS65 clinical trial for elderly patients with MM who had minimal residual disease (MRD) assessments 9 months after study enrollment. Median follow-up of the series was 71 months. [Results]: Achievement of complete remission (CR) in the absence of MRD negativity was not associated with prolonged progression-free survival (PFS) and overall survival (OS) compared with near-CR or partial response (median PFS, 27, 27, and 29 months, respectively; median OS, 59, 64, and 65 months, respectively). MRD-negative status was strongly associated with prolonged PFS (median, 63 months; P < .001) and OS (median not reached; P < .001) overall and in subgroups defined by prior transplantation, disease stage, and cytogenetics, with prognostic superiority of MRD negativity versus CR particularly evident in patients with high-risk cytogenetics. Accordingly, Harrell C statistics showed higher discrimination for both PFS and OS in Cox models that included MRD (as opposed to CR) for response assessment. Superior MRD-negative rates after different induction regimens anticipated prolonged PFS. Among 34 MRD-negative patients with MM and a phenotypic pattern of bone marrow involvement similar to monoclonal gammopathy of undetermined significance at diagnosis, the probability of >operational cure> was high; median PFS was 12 years, and the 10-year OS rate was 94%. [Conclusion]: Our results demonstrate that MRD-negative status surpasses the prognostic value of CR achievement for PFS and OS across the disease spectrum, regardless of the type of treatment or patient risk group. MRD negativity should be considered as one of the most relevant end points for transplant-eligible and elderly fit patients with MM., Supported by the Centro de Investigación Biomédica en Red – Area de Oncologia - del Instituto de Salud Carlos III (CIBERONC; CB16/12/00369; CB16/12/00400; CB16/12/00233; CB16/12/00284), formerly named as Cooperative Research Thematic Network (Grants No. RD12/0036/0058, RD12/0036/0048, RD12/0036/0046, and RD12/0036/0061) of the Red de Cancer (Cancer Network of Excellence); Instituto de Salud Carlos III/Subdirección General de Investigación Sanitaria; funded in part by the European Regional Development Fund (FIS No. 98/1239, 00/10160, 01/0089, 02/0089, 02/0905, G03/136, PI051284, PI06033906/1354, PS09/01897/01370, PI12/01761, PI12/02311, PI13/01469, PI14/01867, G03/136); Sara Borrell (No. CD13/00340); Asociación Española Contra el Cáncer (No. GCB120981SAN); and Federación Española de Enfermedades Raras. Also supported internationally by the Black Swan Research Initiative of the International Myeloma Foundation and the European Research Council 2015 Starting Grant (MYELOMANEXT).

[Background]: The B cell maturation process involves multiple steps, which are controlled by relevant pathways and transcription factors. The understanding of the final stages of plasma cell (PC) differentiation could provide new insights for therapeutic strategies in multiple myeloma (MM). Here, we explore the role of DEPTOR, an mTOR inhibitor, in the terminal differentiation of myeloma cells, and its potential impact on patient survival. [Methods]: The expression level of DEPTOR in MM cell lines and B cell populations was measured by real-time RT-PCR, and/or Western blot analysis. DEPTOR protein level in MM patients was quantified by capillary electrophoresis immunoassay. RNA interference was used to downregulate DEPTOR in MM cell lines. [Results]: DEPTOR knockdown in H929 and MM1S cell lines induced dedifferentiation of myeloma cells, as demonstrated by the upregulation of PAX5 and BCL6, the downregulation of IRF4, and a clear reduction in cell size and endoplasmic reticulum mass. This effect seemed to be independent of mTOR signaling, since mTOR substrates were not affected by DEPTOR knockdown. Additionally, the potential for DEPTOR to be deregulated in MM by particular miRNAs was investigated. The ectopic expression of miR-135b and miR-642a in myeloma cell lines substantially diminished DEPTOR protein levels, and caused dedifferentiation of myeloma cells. Interestingly, the level of expression of DEPTOR protein in myeloma patients was highly variable, the highest levels being associated with longer progression-free survival. [Conclusions]: Our results demonstrate for the first time that DEPTOR expression is required to maintain myeloma cell differentiation and that high level of its expression are associated with better outcome. Primary samples used in this study correspond to patients entered into GEM2010 trial (registered at www.clinicaltrials.gov as #NCT01237249, 4 November 2010)., This study was partially supported by the Instituto de Salud Carlos III (Fondo de Investigaciones Sanitarias: PI08/0568 and PI13/00111), Asociación Española Contra el Cáncer (AECC, GCB120981SAN), Gerencia Regional de Salud, Junta de Castilla y León grants (GRS 702/A/11, BIO/SA57/13 and BIO/SA35/14), the Spanish Myeloma Network Program (RD12/0036/0058), and the INNOCAMPUS Program (CEI10-1-0010). IMK was supported by the Instituto de Salud Carlos III (PS09/01897) and the International Myeloma Foundation’s Black Swan Research Initiative®. MES was supported by Contrato Miguel Servet (CP13/00080).

[Background]: Multiparameter flow cytometry (MFC) identification and characterization of plasma cells (PCs) is a useful tool to support diagnosis, prognostication, and monitoring of PC diseases (PCD). Currently, the number of MFC markers suited for the identification of PC remains limited. Moreover, antibody therapies against PC-associated markers further compromise the utility of the most widely used reagents (e.g., CD38). Despite markers other than CD38 and CD138 are recognized as potentially useful PC-identification markers, no study has comparatively evaluated their performance in combination with CD38 and CD138. Here we compared the utility of CD229, CD54, and CD319 for the identification of normal and aberrant PCs. [Methods]: Bone marrow (BM) samples from 5 healthy controls, two noninfiltrated nonHodgkin lymphoma cases and 46 PCD patients plus 3 extraosseous plasmocytomas, and normal peripheral blood (PB) specimens, were studied. [Results]: Our results showed adequate performance of all three markers once combined with CD38. In contrast, when combined with CD138 for the identification of PC, only CD229 provided a good discrimination between PCs and all other cells for all BM and PB samples analyzed; in contrast, CD54 and CD319 showed limited utility for the identification of PCs, mainly because of significant overlap of the staining for these two markers on PCs and other myeloid cells in the sample. [Conclusions]: From the three markers evaluated, CD229 may be considered as the most reliable marker to replace CD38 or CD138 for the identification of PCs in patients undergoing anti-CD38 or anti-CD138 therapy, until a better alternative is available., Grant sponsor: the Instituto de Salud Carlos III (Ministry of Economy and Competitivity, Madrid, Spain); Grant number: FEDER (RD12/0036/0048; Grant sponsors: EuroFlow Consortium, the International Myeloma Foundation-Black Swan Research Initiative, the Red Tematica de Investigacion Cooperativa en Cancer (RTICC)

The value of minimal residual disease (MRD) in multiple myeloma (MM) has been more frequently investigated in transplant-eligible patients than in elderly patients. Because an optimal balance between treatment efficacy and toxicity is of utmost importance in patients with elderly MM, sensitive MRD monitoring might be particularly valuable in this patient population. Here, we used second-generation 8-color multiparameter-flow cytometry (MFC) to monitor MRD in 162 transplant-ineligible MM patients enrolled in the PETHEMA/GEM2010MAS65 study. The transition from first- to second-generation MFC resulted in increased sensitivity and allowed us to identify 3 patient groups according to MRD levels: MRD negative (75 years (HR, 4.8; P < .001), as well as those with high-risk cytogenetics (HR, 12.6; P = .01). Using second-generation MFC, immune profiling concomitant to MRD monitoring also contributed to identify patients with poor, intermediate, and favorable outcomes (25%, 61%, and 100% OS at 3 years, respectively; P = .01), the later patients being characterized by an increased compartment of mature B cells. Our results show that similarly to transplant candidates, MRD monitoring is one of the most relevant prognostic factors in elderly MM patients, irrespectively of age or cytogenetic risk., This study was supported by Cooperative Research Thematic Network grants RD12/0036/0058, RD12/0036/0048, RD12/0036/0046, and RD12/0036/0061 of the Red de Cancer (Cancer Network of Excellence); Instituto de Salud Carlos III, Spain, Instituto de Salud Carlos III/Subdirección General de Investigación Sanitaria (FIS: PI060339; 06/1354; 02/0905; 01/0089/01-02; PS09/01897/01370; PI13/01469, PI14/01867, G03/136; Sara Borrell: CD13/00340 and CD12/00540); and Asociación Española Contra el Cáncer (GCB120981SAN). The study was also supported internationally by the Black Swan Research Initiative of the International Myeloma Foundation and a European Research Council 2015 starting grant.

The notion that plasma cells (PCs) are terminally differentiated has prevented intensive research in multiple myeloma (MM) about their phenotypic plasticity and differentiation. Here, we demonstrated in healthy individuals (n=20) that the CD19-CD81 expression axis identifies three bone marrow (BM)PC subsets with distinct age-prevalence, proliferation, replication-history, immunoglobulin-production, and phenotype, consistent with progressively increased differentiation from CD19+CD81+ into CD19-CD81+ and CD19-CD81- BMPCs. Afterwards, we demonstrated in 225 newly diagnosed MM patients that, comparing to normal BMPC counterparts, 59% had fully differentiated (CD19-CD81-) clones, 38% intermediate-differentiated (CD19-CD81+) and 3% less-differentiated (CD19+CD81+) clones. The latter patients had dismal outcome, and PC differentiation emerged as an independent prognostic marker for progression-free (HR: 1.7; P=0.005) and overall survival (HR: 2.1; P=0.006). Longitudinal comparison of diagnostic vs minimal-residual-disease samples (n=40) unraveled that in 20% of patients, less-differentiated PCs subclones become enriched after therapy-induced pressure. We also revealed that CD81 expression is epigenetically regulated, that less-differentiated clonal PCs retain high expression of genes related to preceding B-cell stages (for example: PAX5), and show distinct mutation profile vs fully differentiated PC clones within individual patients. Together, we shed new light into PC plasticity and demonstrated that MM patients harbouring less-differentiated PCs have dismal survival, which might be related to higher chemoresistant potential plus different molecular and genomic profiles., This study was supported by the Cooperative Research Thematic Network grants RD12/0036/0048, RD12/0036/0058, RD12/0036/0046, RD12/0036/0068, RD12/0036/0069, and RD12/0036/0061 of the Red de Cancer (Cancer Network of Excellence); Instituto de Salud Carlos III, Spain, Instituto de Salud Carlos III/Subdirección General de Investigación Sanitaria (FIS: PI060339; 06/1354; 02/0905; 01/0089/01-02; PS09-/01897/01370; PI13/01469, PI14/01867, G03/136; Sara Borrell: CD13/00340 and CD12/00540); Fundació La Marató de TV3 (20132130-31-32) and Asociación Española Contra el Cáncer (GCB120981SAN). The study was also supported internationally by the International Myeloma Foundation (IMF) Junior Grant, the Black Swan Research Initiative of the IMF, the Multiple Myeloma Research Foundation research fellow award, the Qatar National Research Fund (QNRF) Award No. 7-916-3-237, Marie Curie (LincMHeM-330598), the AACR-Millennium Fellowship in Multiple Myeloma Research (15-40-38-PAIV), Leukemia Research Foundation and the European Research Council (ERC) 2015 Starting Grant.