Real-time quantitative PCR (qPCR) is a well-established tool for minimal residual disease (MRD) detection in mature lymphoid malignancies. Despite remarkable sensitivity and specificity, qPCR has some limitations, particularly in the need for a reference standard curve, based on target serial dilutions. In this study, we established droplet digital PCR (ddPCR) for MRD monitoring in multiple myeloma, mantle cell lymphoma, and follicular lymphoma and compared it head-to-head with qPCR. We observed that ddPCR has sensitivity, accuracy, and reproducibility comparable with qPCR. We then compared the two approaches in 69 patients with a documented molecular marker at diagnosis (18 multiple myelomas, 21 mantle cell lymphomas assessed with the immunoglobulin gene rearrangement, and 30 follicular lymphomas with the use of the BCL2/immunoglobulin gene major breakpoint region rearrangement). ddPCR was successful in 100% of cases, whereas qPCR failed to provide a reliable standard curve in three patients. Overall, 222 of 225 samples were evaluable by both methods. The comparison highlighted a good concordance (r = 0.94, P < 0.0001) with 189 of 222 samples (85.1%; 95% CI, 80.4%-89.8%) being fully concordant. We found that ddPCR is a reliable tool for MRD detection with greater applicability and reduced labor intensiveness than qPCR. It will be necessary to authorize ddPCR as an outcome predictor tool in controlled clinical settings and multilaboratory standardization programs.

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BackgroundMultiple myeloma (MM) is a plasma cell malignancy with a multifaceted immune dysfunction. Indoleamine 2,3-dioxygenase 1 (IDO1) degrades tryptophan into kynurenine (KYN), which inhibits effector T cells and promote regulatory T-cell (Treg) differentiation. It is presently unknown whether MM cells express IDO1 and whether IDO1 activity correlates with immune system impairment.MethodsWe investigated IDO1 expression in 25 consecutive patients with symptomatic MM and in 7 patients with either monoclonal gammopathy of unknown significance (MGUS; n=3) or smoldering MM (SMM; n=4). IDO1-driven tryptophan breakdown was correlated with the release of hepatocyte growth factor (HGF) and with the frequency of Treg cells and NY-ESO-1-specific CD8+ T cells.ResultsKYN was increased in 75% of patients with symptomatic MM and correlated with the expansion of CD4+CD25+FoxP3+ Treg cells and the contraction of NY-ESO-1-specific CD8+ T cells. In vitro, primary MM cells promoted the differentiation of allogeneic CD4+ T cells into bona fide CD4+CD25hiFoxP3hi Treg cells and suppressed IFN-γ/IL-2 secretion, while preserving IL-4 and IL-10 production. Both Treg expansion and inhibition of Th1 differentiation by MM cells were reverted, at least in part, by d,l-1-methyl-tryptophan, a chemical inhibitor of IDO. Notably, HGF levels were higher within the BM microenvironment of patients with IDO+ myeloma disease compared with patients having IDO- MM. Mechanistically, the antagonism of MET receptor for HGF with SU11274, a MET inhibitor, prevented HGF-induced AKT phosphorylation in MM cells and translated into reduced IDO protein levels and functional activity.ConclusionsThese data suggest that IDO1 expression may contribute to immune suppression in patients with MM and possibly other HGF-producing cancers.

The extracellular matrix (ECM) is a major component of the tumor microenvironment, contributing to the regulation of cell survival, proliferation, differentiation and metastasis. In multiple myeloma (MM), interactions between MM cells and the bone marrow (BM) microenvironment, including the BM ECM, are critical to the pathogenesis of the disease and the development of drug resistance. Nevertheless, composition of the ECM in MM and its role in supporting MM pathogenesis has not been reported. We have applied a novel proteomic-based strategy and defined the BM ECM composition in patients with monoclonal gammopathy of undetermined significance (MGUS), newly diagnosed and relapsed MM compared with healthy donor-derived BM ECM. In this study, we show that the tumor ECM is remodeled at the mRNA and protein levels in MGUS and MM to allow development of a permissive microenvironment. We further demonstrate that two ECM-affiliated proteins, ANXA2 and LGALS1, are more abundant in MM and high expression is associated with a decreased overall survival. This study points to the importance of ECM remodeling in MM and provides a novel proteomic pipeline for interrogating the role of the ECM in cancers with BM tropism.

High XBP1 expression is a marker of better outcome in multiple myeloma patients treated with bortezomibMultiple myeloma (MM) is a hematologic tumor characterized by accumulation of monoclonal plasma cells (PCs) in the bone marrow (BM) producing antigen-specific immunoglobulins. The transcription factor X box binding protein 1 (XBP1), the interferon regulatory factor 4 (IRF4) and the transcriptional repressor B lymphocite-induced maturation protein 1 (BLIMP1) are essential to drive physiological plasmacytic differentiation.1,2 XBP1 is particularly required for the last stages of B-cell differentiation into PC, and, consistently, XBP1-deficient mice display normal Blymphocite development up to germinal center, but are unable to produce PCs.2 High mRNA levels of IRF4, BLIMP1 and XBP1 have been detected in malignant PC and are negative prognostic factors in patients treated with standard chemotherapy or thalidomide.3,4 Lenalidomide seems to overcome the negative prognostic impact of IRF4 overexpression, due to its rapid downregulation following treatment. Bortezomib induces better responses in patients with high levels of XBP1. 5,6We assessed the prognostic role of gene-driven plasmacytic differentiation in a large cohort of patients treated with bortezomib. RNA expression of three genes involved in PCs differentiation was investigated in purified PCs (CD138 + BM fraction) of well-characterized patients with newly diagnosed MM. One hundred and fifty-one patients enrolled in two multicenter clinical trials (the PAD-MEL100-LP-L and the VMP-VMPT) were assessed.7,8 PCs were purified using anti-CD138-coated magnetic MicroBeads and AutoMACS Pro Separator (Miltenyi Biotech GmbH, Germany) following manufacturer specifications. Gene expression was investigated on isolated PCs with more than 90% of purity assessed by flow cytometry. RNA was extracted using the DNA/RNA Purification Kit (Norgen, Thorold, Canada). Complementary DNA was produced using High capacity cDNA RT Kit (Applied Biosytem, Foster Ciy, CA, USA). Quantitative PCR to measure RNA expression of XBP1, IRF4 and BLIMP1 was performed with the Abi Prism 7900HT (Applied Biosystems, Carlsbad, CA, USA) using a relative quantification based on ΔΔCt approach and GUSB (b-glucuronidase) as housekeeping gene. All RNA determinations were performed using the following assays: © F e r r a t a S t o r t i F o u n d a t i o ning to gene expression using the median value as cut off.Response to therapy and clinical outcome were assessed following IMWG criteria. 9 The progression-free survival (PFS) and overall survival (OS) were estimated by the Cox proportional hazard model, comparing the risk factors by the Wald test; best response was treated as a time-dependent variable. Patients' characteristics were compared by the Fisher's exact test for the categorical variables and the Mann-Whitney test for the continuous ones. All reported P-values were two-sided, at the conventional 5% significance level. Data were analyzed as of January 2013 by SPSS 21.0.0 and R 3.0.1 package surviva...

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Writing-review and editing: all the authors All the authors approved the final version of the manuscript and agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

BACKGROUND: Minimal residual disease (MRD) is one of the most relevant prognostic factors in patients with multiple myeloma (MM); however, the impact of maintenance therapy on MRD levels remains unclear. Among patients with newly diagnosed MM (NDMM) who received lenalidomide maintenance until they developed disease progression, the role of MRD status as a predictor of progression-free survival (PFS) was evaluated by multiparameter flow cytometry (MFC) and allelic-specific oligonucleotide real-time quantitative polymerase chain reaction (ASO-RQ-PCR) analysis. METHODS: Seventy-three patients with NDMM enrolled in the RV-MM-EMN-441 (clinical trials.gov identifier, NCT01091831) and RV-MM-COOP-0556 (clinicaltrials.gov identifier, NCT01208766; European Myeloma Network EMN02/HO95 MM Trial) phase 3 trials who achieved at least a very good partial response after intensification/consolidation were included. The median patient age was 57 years (interquartile range, 53-61 years), and all patients received lenalidomide maintenance until they developed progression. MRD was evaluated on bone marrow after intensification/consolidation, after 6 courses of maintenance, and every 6 months thereafter until clinical relapse using both ASO-RQ-PCR (sensitivity, 10 −5 ) and MFC (sensitivity, from 10 −4 to 10 −5 ). RESULTS: After intensification/consolidation, 33 of 72 patients (46%) achieved a molecular complete response (m-CR), and 44 of 70 (63%) achieved a flow complete response (flow-CR). Almost 27% of patients who were MRD-positive after consolidation became MRDnegative during maintenance. After a median follow-up of 38 months, PFS was prolonged in patients who achieved negative MRD status during maintenance according to results from both ASO-RQ-PCR analysis (hazard ratio, 0.29; 95% confidence interval, 0.14-0.62; P = .0013) and MFC (hazard ratio, 0.19; 95% confidence interval, 0.09-0.41; P < .001). The impact of negative MRD status on PFS was similar in all subgroups (ASCT and no-ASCT; International Staging System stages I, II, and III; high-risk and standard-risk cytogenetics), and the two techniques were highly correlated. CONCLUSIONS: MRD status is a stronger predictor of PFS than standard risk factors, and lenalidomide maintenance further increases the rate of negative MRD results. Cancer 2019;125:750-760.