Obinutuzumab versus Rituximab in transplant-eligible Mantle cell lymphoma patients.

Obinutuzumab (O) and Rituximab (R) are two CD antibodies that have never been compared in a prospective randomised trial in mantle cell lymphoma (MCL). Herein, we report the long-term outcome of the LYMA-101 (NCT02896582) trial, in which newly diagnosed MCL patients were treated with chemotherapy plus O before transplantation followed by O maintenance (O group). We then compared these patients to those treated with the same treatment design with Rituximab instead of O (R group) (NCT00921414). A propensity score matching (PSM) was used to compare the two populations (O vs R groups) in terms of MRD at the end of induction (EOI), PFS and OS. In LYMA-101, the estimated five-year PFS and OS since inclusion (n=85) were 83.4% (95%CI: 73.5-89.8%) and 86.9% (95%CI: 77.6-92.5%), respectively. At EOI, patients treated in the O group had more frequent bone marrow MRD negativity than those treated in the R group (83.1% vs 63.4% Chi2 p=0.007). The PSM resulted in 2 sets of 82 patients with comparable characteristics at inclusion. From treatment initiation, the O group had a longer estimated five-year PFS (p=0.029; 82.8% versus 66.6%, HR 1.99, IC95 1.05-3.76) and OS (p=0.039; 86.4% versus 71.4% (HR 2.08, IC95 1.01-4.16) compared to the R group. Causes of death were comparable in the 2 groups, the most common cause being lymphoma. Obinutuzumab prior to transplantation and in maintenance provides better disease control and enhances PFS and OS, as compared to Rituximab in transplant-eligible MCL patients.

Ibrutinib, obinutuzumab, and venetoclax in relapsed and untreated patients with mantle cell lymphoma: a phase 1/2 trial.

Ibrutinib, obinutuzumab, and venetoclax demonstrate synergy in preclinical models of mantle cell lymphoma (MCL). OAsIs (NCT02558816), a single-arm multicenter prospective phase 1/2 trial, aimed to determine the maximum tolerated dose of venetoclax in combination with fixed doses of ibrutinib and obinutuzumab, in relapsed MCL patients. At the venetoclax MTD, extension cohorts were opened for relapsed and untreated patients. Safety and efficacy were secondary objectives. Minimal residual disease (MRD) was assessed by allele-specific oligonucleotide quantitative polymerase chain reaction. Between 14 October 2015 and 29 May 2018, 48 patients were enrolled. No dose-limiting toxicity was reported, and venetoclax at 400 mg per day was chosen for extension. Eighteen (75%) relapsed and 8 (53%) untreated patients experienced grade 3/4 adverse events. The complete response rate assessed by positron emission tomography at the end of cycle 6 was 67% in relapsed and 86.6% in untreated patients. MRD clearance for evaluable patients was seen in 71.5% of relapsed (10/14 patients) and 100% of untreated MRD-evaluable patients (n = 12) at the end of 3 cycles. The median follow-up for relapsed patients was 17 months (range, 10-35 months). The 2-year progression-free survival (PFS) was 69.5% (95% confidence interval [CI], 52.9%-91.4%) and 68.6% (95% CI, 49.5%-95.1%) for overall survival. The median follow-up was 14 months (range, 5-19) for untreated patients, the 1-year PFS was 93.3% (95% CI, 81.5%-100%). The combination of obinutuzumab, ibrutinib, and venetoclax is well tolerated and provides high response rates, including at the molecular level, in relapsed and untreated MCL patients. This trial was registered at www.clinicaltrials.gov as #NCT02558816.

Long-term analysis of the RiBVD phase II trial reveals the unfavorable impact of TP53 mutations and hypoalbuminemia in older adults with mantle cell lymphoma; for the LYSA group.

Between 2011 and 2012, a phase II trial evaluated the use of the RiBVD (Rituximab, Bendamustine, Velcade and Dexamethasone) combination as first-line treatment for mantle cell lymphoma (MCL) patients aged over 65. We have now re-examined the classic prognostic factors, adding an assessment of the mutation status of TP53. Patients (n=74; median age 73 years) were treated with the RiBVD combination. Median Progression Free Survival (mPFS) was 79 months, and median Overall Survival (mOS) was 111 months. TP53 mutation status was available for 54/74 (73%) patients. TP53 mutations (TP53mt) were found in 12 patients (22.2%). In multivariate analysis, among the prognostic factors (PF) evaluated, only TP53mt and an albumin level below 3.6 g/dL (Alb<3.6 g/dL) were independently associated with a shorter mPFS. A hazard ratio (HR) of 3.16 (1.3-9.9, p=0.014) was obtained for TP53mt versus TP53wt, and 3.6 (1.39-9.5, p=0.009) for Alb<3.6 g/dL vs Alb≥3.6 g/dL. In terms of mOS, multivariate analysis identified three PFs: TP53mt (HR: 5.9 (1.77-19.5, p=0.004)), Alb<3.6 g/dL (HR: 5.2 (1.46-18.5, p=0.011)), and ECOG=2 (HR: 3.7 (1.31-10.6, p=0.014)). Finally, a score combining TP53 status and albumin level distinguished three populations based on the presence of 0, 1, or 2 PF. For these populations, mPFS was 7.8 years, 28 months and 2.5 months, respectively. Our prolonged follow-up confirmed the efficacy of the RiBVD regimen, comparing it favorably to other regimens. TP53mt and hypoalbuminemia emerge as strong PF that can be easily integrated into prognostic scores for older adult patients with MCL.

[Contribution and limits of lean management in the organization and working of a pathology department]. / Apports et limites du lean management dans l'organisation et le fonctionnement d'un service de Pathologie.

INTRODUCTION: In order to validate our strategy of continuous improvement and to identify new ways to increase performance, an evaluation of all the procedures was conducted in our department using the principles of lean management. MATERIAL AND METHODS: Lean-6-sigma methodology (Gemba Walk, Value StreamMapping, spaghetti diagram, Kaizen workshop and priorization matrix) was used to analyze the procedures of the conventional and molecular sectors, and to identify bottlenecks, actions without added value and solutions. RESULTS: The audit identified bottlenecks in pre-analytical (registration), analytical (cytology, immunohistochemistry, sequencing, pathologists) and post-analytical processes (absence of secretaries, delivery of reports by mail). It underlined a suboptimal flow of people and materials, the heavy impact of an increasing work load (8%/year) in reception and microscopy even though we had outsourced, and an often critical work place schedule for technicians which prevent them from achieving tasks without added value (quality control, validation of methods and protocols) or even daily tasks (cutting, immunohistochemistry). After completing the 72 actions aimed at managing overproduction, improving working conditions and developing new activities, turn-around time was partially under control and the automation process was well advanced. DISCUSSION AND CONCLUSION: The audit validated our strategy of continuous improvement and advanced the standardization of our working conditions. Even if the turn-around time for reports was shortened, the audit initiated a positive medical and technical dynamic that should help us to implement the next steps of our reorganization (automation and extension of the department).

Rituximab after Autologous Stem-Cell Transplantation in Mantle-Cell Lymphoma.

BACKGROUND: Mantle-cell lymphoma is generally incurable. Despite high rates of complete response after initial immunochemotherapy followed by autologous stem-cell transplantation, patients have relapses. We investigated whether rituximab maintenance therapy at a dose of 375 mg per square meter of body-surface area administered every 2 months for 3 years after transplantation would prolong the duration of response. METHODS: In a phase 3 trial involving 299 patients who were younger than 66 years of age at diagnosis, we randomly assigned 240 patients to receive rituximab maintenance therapy or to undergo observation after autologous stem-cell transplantation (120 patients per group); 59 patients did not undergo randomization. The primary end point was event-free survival (with an event defined as disease progression, relapse, death, allergy to rituximab, or severe infection) after transplantation among patients who underwent randomization. RESULTS: After four courses of immunochemotherapy induction (rituximab, dexamethasone, cytarabine, and a platinum derivative [R-DHAP]), the overall response rate was 89%, and the complete response rate 77%. Transplantation was performed in 257 patients. The median follow-up from randomization after transplantation was 50.2 months (range, 46.4 to 54.2). Starting from randomization, the rate of event-free survival at 4 years was 79% (95% confidence interval [CI], 70 to 86) in the rituximab group versus 61% (95% CI, 51 to 70) in the observation group (P=0.001). The rate of progression-free survival at 4 years was 83% (95% CI, 73 to 88) in the rituximab group versus 64% (95% CI, 55 to 73) in the observation group (P<0.001). The rate of overall survival was 89% (95% CI, 81 to 94) in the rituximab group versus 80% (95% CI, 72 to 88) in the observation group (P=0.04). According to a Cox regression unadjusted analysis, the rate of overall survival at 4 years was higher in the rituximab group than in the observation group (hazard ratio for death, 0.50; 95% CI, 0.26 to 0.99; P=0.04). CONCLUSIONS: Rituximab maintenance therapy after transplantation prolonged event-free survival, progression-free survival, and overall survival among patients with mantle-cell lymphoma who were younger than 66 years of age at diagnosis. (Funded by Roche and Amgen; LyMa ClinicalTrials.gov number, NCT00921414 .).

A phase 2 study of rituximab, bendamustine, bortezomib and dexamethasone for first-line treatment of older patients with mantle cell lymphoma.

We present results of a prospective, multicenter, phase II study evaluating rituximab, bendamustine, bortezomib and dexamethasone as first-line treatment for patients with mantle cell lymphoma aged 65 years or older. A total of 74 patients were enrolled (median age, 73 years). Patients received a maximum of six cycles of treatment at 28-day intervals. The primary objective was to achieve an 18-month progression-free survival rate of 65% or higher. Secondary objectives were to evaluate toxicity and the prognostic impact of mantle cell lymphoma prognostic index, Ki67 expression, [18F]fluorodeoxyglucose-positron emission tomography and molecular minimal residual disease, in peripheral blood or bone marrow. With a median follow-up of 52 months, the 24-month progression-free survival rate was 70%, hence the primary objective was reached. After six cycles of treatment, 91% (54/59) of responding patients were analyzed for peripheral blood residual disease and 87% of these (47/54) were negative. Four-year overall survival rates of the patients who did not have or had detectable molecular residual disease in the blood at completion of treatment were 86.6% and 28.6%, respectively (P<0.0001). Neither the mantle cell lymphoma index, nor fluorodeoxyglucose-positron emission tomography nor Ki67 positivity (cut off of ≥30%) showed a prognostic impact for survival. Hematologic grade 3-4 toxicities were mainly neutropenia (51%), thrombocytopenia (35%) and lymphopenia (65%). Grade 3-4 non-hematologic toxicities were mainly fatigue (18.5%), neuropathy (15%) and infections. In conclusion, the tested treatment regimen is active as frontline therapy in older patients with mantle cell lymphoma, with manageable toxicity. Minimal residual disease status after induction could serve as an early predictor of survival in mantle cell lymphoma. ClinicalTrials.gov: NCT 01457144.

Haploinsufficiency for NR3C1, the gene encoding the glucocorticoid receptor, in blastic plasmacytoid dendritic cell neoplasms.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and highly aggressive leukemia for which knowledge on disease mechanisms and effective therapies are currently lacking. Only a handful of recurring genetic mutations have been identified and none is specific to BPDCN. In this study, through molecular cloning in an index case that presented a balanced t(3;5)(q21;q31) and molecular cytogenetic analyses in a further 46 cases, we identify monoallelic deletion of NR3C1 (5q31), encoding the glucocorticoid receptor (GCR), in 13 of 47 (28%) BPDCN patients. Targeted deep sequencing in 36 BPDCN cases, including 10 with NR3C1 deletion, did not reveal NR3C1 point mutations or indels. Haploinsufficiency for NR3C1 defined a subset of BPDCN with lowered GCR expression and extremely poor overall survival (P = .0006). Consistent with a role for GCR in tumor suppression, functional analyses coupled with gene expression profiling identified corticoresistance and loss-of-EZH2 function as major downstream consequences of NR3C1 deletion in BPDCN. Subsequently, more detailed analyses of the t(3;5)(q21;q31) revealed fusion of NR3C1 to a long noncoding RNA (lncRNA) gene (lincRNA-3q) that encodes a novel, nuclear, noncoding RNA involved in the regulation of leukemia stem cell programs and G1/S transition, via E2F. Overexpression of lincRNA-3q was a consistent feature of malignant cells and could be abrogated by bromodomain and extraterminal domain (BET) protein inhibition. Taken together, this work points to NR3C1 as a haploinsufficient tumor suppressor in a subset of BPDCN and identifies BET inhibition, acting at least partially via lncRNA blockade, as a novel treatment option in BPDCN.

Lymphocytes degranulation in liver in hepatitis C virus carriers is associated with IFNL4 polymorphisms and ALT levels.

BACKGROUND: The polymorphisms of IFNL4 are strongly associated with both spontaneous hepatitis C virus (HCV) clearance and response to peg-IFN-α/ribavirin treatment. To further establish the biological effects of the IFNL4 and rs1297860 variations, we studied the activity of liver immune cells. METHODS: Fresh liver samples were collected from HCV-infected patients before any treatment and from NASH patients as controls. Degranulation activity of each lymphocyte type was assessed by the surface expression of CD107a. IFNL4 polymorphisms and HCV genotypes were determined. RESULTS: In the liver, frequency of CD107a(+) immune cells was significantly higher in HCV patients compared to NASH patients. Higher degranulation activity was observed in lymphocytes of HCV patients with favorable IFNL4 genotypes compared to patients with unfavorable genotypes. Multivariate regression analyses indicated that serum ALT levels were dependent on both Metavir activity score and frequency of CD107a positive NKT cells. The high level of degranulation activity observed before treatment was associated with a high HCV RNA decline at the early stage of peg-IFN-α/ribavirin treatment in patients with favorable genotypes. CONCLUSIONS: These data underline that intrahepatic lymphocyte degranulation activity in HCV-infected patients is associated with IFNL4 polymorphisms and contributes to the clearance of HCV in patients with favorable genotypes under antiviral therapy.

Protein arginine methyltransferase 2 controls inflammatory signaling in acute myeloid leukemia.

Arginine methylation is catalyzed by protein arginine methyltransferases (PRMTs) and is involved in various cellular processes, including cancer development. PRMT2 expression is increased in several cancer types although its role in acute myeloid leukemia (AML) remains unknown. Here, we investigate the role of PRMT2 in a cohort of patients with AML, PRMT2 knockout AML cell lines as well as a Prmt2 knockout mouse model. In patients, low PRMT2 expressors are enriched for inflammatory signatures, including the NF-κB pathway, and show inferior survival. In keeping with a role for PRMT2 in control of inflammatory signaling, bone marrow-derived macrophages from Prmt2 KO mice display increased pro-inflammatory cytokine signaling upon LPS treatment. In PRMT2-depleted AML cell lines, aberrant inflammatory signaling has been linked to overproduction of IL6, resulting from a deregulation of the NF-κB signaling pathway, therefore leading to hyperactivation of STAT3. Together, these findings identify PRMT2 as a key regulator of inflammation in AML.

Prognostic value of postinduction medullary myeloid recovery by flow cytometry in acute myeloid leukemia.

Risk stratification and treatment response evaluation are key features in acute myeloid leukemia (AML) management. Immunophenotypic and molecular approaches all rely on the detection of persisting leukemic cells by measurable residual disease techniques. A new approach is proposed here by assessing medullary myeloid maturation by flow cytometry through a myeloid progenitor ratio (MPR). The normal MPR range was defined using reference normal bone marrows (n = 48). MPR was considered balanced if between 1 and 4 and unbalanced if < 1 or > 4. MPR was retrospectively assessed at baseline and post-induction for 206 newly diagnosed AML patients eligible for intensive treatment from two different French centers. All AML baseline MPR were unbalanced and thus significantly different from normal MPR (p < 0.0001). Patients with an unbalanced MPR after induction had worse 3-year overall survival (OS) (44.4% vs. 80.2%, HR, 2.96; 95% CI, 1.81-4.84, p < 0.0001) and 3-year relapse free survival (RFS) (38.7% vs. 64.4%, HR, 2.11; 95% CI, 1.39-3.18, p < 0.001). In multivariate analysis, postinduction unbalanced MPR was significantly associated with shorter OS and RFS regardless of the European LeukemiaNet 2010 risk stratification or NPM1/FLT3-ITD status. A balanced postinduction MPR conversely conferred favorable outcomes and reflects medullary myeloid recovery.

Long-Term Follow-Up of Rituximab Maintenance in Young Patients With Mantle-Cell Lymphoma Included in the LYMA Trial: A LYSA Study.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned coprimary or secondary analyses are not yet available. Clinical trial updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.The LYMA trial demonstrated the benefit of rituximab maintenance (RM) in first-line young patients with mantle-cell lymphoma. In this prolonged follow-up of 7.5 years (95% CI, 7.4 to 7.7) from inclusion, the median progression-free survival (PFS) and overall survival (OS) for the full population were not reached (NR) with a 7-year PFS of 55.5% (95% CI, 49.5 to 61) and OS of 69.5% (95% CI, 63.8 to 74.5). The EFS remained statistically superior in favor of RM (median NR v 5.8 years, P < .0001; HR, 0.39 [95% CI, 0.52 to 0.6] and 7-year estimate, 76.2% versus 46% for RM and observation, respectively). Similarly, RM prolonged PFS (estimated PFS at 7 years, 78.5% v 47.4% and HR, 0.36 [95% CI, 0.23 to 0.56] for RM and observation, respectively, P < .0001). The 7-year OS estimate was 83.2% versus 72.2%, respectively (P = .088, HR, 0.63 [95% CI, 0.37 to 1.08]). Cause of death was not significantly distinct between the two groups, with lymphoma being the leading cause with a very low rate of infection-related death. Overall, the PFS benefit of RM after autologous stem cell transplantation remains after 7-year follow-up, and RM was not associated with an increase in infection-related mortality, making this strategy a safe standard of care with long-term follow-up.

Telomeric damage in early stage of chronic lymphocytic leukemia correlates with shelterin dysregulation.

Cells of B-cell chronic lymphocytic leukemia (B-CLL) are characterized by short telomeres despite a low proliferative index. Because telomere length has been reported to be a valuable prognosis criteria, there is a great interest in a deep understanding of the origin and consequences of telomere dysfunction in this pathology. Cases of chromosome fusion involving extremely short telomeres have been reported at advanced stage. In the present study, we address the question of the existence of early telomere dysfunction during the B-CLL time course. In a series restricted to 23 newly diagnosed Binet stage A CLL patients compared with 12 healthy donors, we found a significant increase in recruitment of DNA-damage factors to telomeres showing telomere dysfunction in the early stage of the disease. Remarkably, the presence of dysfunctional telomeres did not correlate with telomere shortening or chromatin marks deregulation but with a down-regulation of 2 shelterin genes: ACD (coding for TPP1; P = .0464) and TINF2 (coding for TIN2; P = .0177). We propose that telomeric deprotection in the early step of CLL is not merely the consequence of telomere shortening but also of shelterin alteration.

Induced malignant genome reprogramming in somatic cells by testis-specific factors.

Germline cell differentiation is controlled by a specific set of genes whose expression is tightly locked into the repressed state in somatic cells. Large-scale epigenome alterations, now evidenced in nearly all cancers, lead to aberrant activation of these normally silenced genes, as attested by the many reports describing the expression of testis-specific factors, known as cancer-testis genes, in various cancer cells. Here, based on the literature, we argue that off-context activity of some of the testis-specific epigenome regulators can reprogram the somatic cell epigenome toward a malignant state by favoring self-renewal and sustaining cell proliferation under stressful conditions, thereby constituting a major oncogenic mechanism.

Cloned IGH VDJ targets as tools for personalized minimal residual disease monitoring in mature lymphoid malignancies; a feasibility study in mantle cell lymphoma by the Groupe Ouest Est d'Etude des Leucémies et Autres Maladies du Sang.

Molecular minimal residual disease (MRD) analysis is fast emerging as an essential clinical decision-making tool for the treatment and follow-up of mature B cell malignancies. Current EuroMRD consensus IGH real-time quantitative polymerase chain reaction RQ-PCR assays rely on flow cytometric assessment of diagnostic tumour burdens to construct 'normalized', patient-specific, diagnostic DNA-based MRD quantification standards. Here, we propose a new 'hybrid' assay that relies on plasmid-based quantification of patient-specific IGH VDJ targets by consensus IGH real time (RQ)-PCR, combined with EuroMRD guidelines, for MRD monitoring in lymphoid malignancies. This assay was evaluated for MRD assessment in a total of 273 samples from 29 mantle cell lymphoma (MCL) patients treated within a Groupe Ouest Est d'Etude des Leucémies et Autres Maladies du Sang (GOELAMS) Phase II trial and was feasible, reliable and consistently comparable to gold-standard MRD techniques (99% concordance across all samples including 32 samples within the quantitative range) when analysed in parallel (117 samples). Integrating clinical prognostic parameters and MRD status in peripheral blood at the post-induction stage was predictive of progression-free survival (P = 0·034) thus demonstrating the clinical utility of the approach. Plasmid-based standards for the quantification of IGH VDJ targets are therefore confirmed to offer new opportunities for further standardization and clinical evaluation of MRD-guided management of patients with mature B cell malignancies.

Clinical, functional and genetic analysis of twenty-four patients with chronic granulomatous disease - identification of eight novel mutations in CYBB and NCF2 genes.

Chronic granulomatous disease is an inherited disorder in which phagocytes lack a functional NADPH oxidase and cannot produce superoxide anions. The most common form is caused by mutations in CYBB encoding gp91phox. We investigated 24 CGD patients and their families. Twenty-one mutations in CYBB were classified as X91(0), X91(+) or X91(-) variants according to cytochrome b (558) expression. Point mutations in encoding regions represented 50 % of the mutations found in CYBB, splice site mutations 27 %, deletions and insertions 23 %. Eight mutations in CYBB were novel leading to X91(0)CGD cases. Two of these were point mutations: c493G>T and a double mutation c625C>G in exon 6 and c1510C>T in exon 12 leading to a premature stop codon at Gly165 in gp91phox and missense mutations His209Arg/Thr503Ile respectively. Two novel splice mutations in 5'intronic regions of introns 1 and 6 were found. A novel deletion/insertion c1024_1026delCTG/insT results in a frameshift introducing a stop codon at position 346 in gp91phox. The last novel mutation was the insertion of a T at c1373 leading to a frameshift and a premature stop codon at position 484 in gp91phox. For the first time the precise size of two large mutations in CYBB was determined by array-comparative genomic hybridization and carriers' status were evaluated by multiplex ligation-dependent probe amplification assay. No clear correlation between clinical severity and CYBB mutations could be established. Of three mutations in CYBA, NCF1 and NCF2 leading to rare autosomal recessive CGD, one nonsense mutation c29G>A in exon 1 of NCF2 was new.

Accurate detection of the tumor clone in peripheral T-cell lymphoma biopsies by flow cytometric analysis of TCR-Vß repertoire.

Multiparametric flow cytometry has proven to be a powerful method for detection and immunophenotypic characterization of clonal subsets, particularly in lymphoproliferative disorders of the B-cell lineage. Although in theory promising, this approach has not been comparably fulfilled in mature T-cell malignancies. Specifically, the T-cell receptor-Vß repertoire analysis in blood can provide strong evidence of clonality, particularly when a single expanded Vß family is detected. The purpose of this study was to determine the relevance of this approach when applied to biopsies, at the site of tumor involvement. To this end, 30 peripheral T-cell lymphoma and 94 control biopsies were prospectively studied. Vß expansions were commonly detected within CD4+ or CD8+ T cells (97% of peripheral T-cell lymphoma and 54% of non-peripheral T-cell lymphoma cases); thus, not differentiating malignant from reactive processes. Interestingly, we demonstrated that using a standardized evaluation, the detection of a high Vß expansion was closely associated with diagnosis of peripheral T-cell lymphoma, with remarkable specificity (98%) and sensitivity (90%). This approach also identified eight cases of peripheral T-cell lymphoma that were not detectable by other forms of immunophenotyping. Moreover, focusing Vß expression analysis to T-cell subsets with aberrant immunophenotypes, we demonstrated that the T-cell clone might be heterogeneous with regard to surface CD7 or CD10 expression (4/11 cases), providing indication on 'phenotypic plasticity'. Finally, among the wide variety of Vß families, the occurrence of a Vß17 expansion in five cases was striking. To our knowledge, this is the first report demonstrating the power of T-cell receptor-Vß repertoire analysis by flow cytometry in biopsies as a basis for peripheral T-cell lymphoma diagnosis and precise T-cell clone identification and characterization.

Accurate hematopoietic stem cell frequency estimates by fitting multicell Poisson models substituting to the single-hit Poisson model in limiting dilution transplantation assays.

Limiting dilution transplantation assay (LDTA) is considered as the gold standard method to assess hematopoietic stem cell (HSC) content. Traditionally, HSC frequency estimates are based on the single-hit Poisson model (SHPM), which posits that one donor HSC is sufficient to generate a progeny of detectable differentiated cells above a threshold value in hosts. However, there is no clear support for this statement, and it is receivable that more than one donor HSC may be necessary to provide detectable reconstitution in hosts above the threshold level for detection, usually 0.5% to 1% of donor-derived cells. To address this hypothesis, we evaluated the ability of a class of multiCell Poisson models (C(≥1)PMs) to fit to LDTAs. In 7 of the 8 reanalyzed LDTAs, C(≥1)PMs plausibly compete with the traditional SHPM. Model averaging across the set of plausible models gives 1.32- to 5.88-fold increases in HSC frequencies compared with the SHPM.

Identification of an alternative CD20 transcript variant in B-cell malignancies coding for a novel protein associated to rituximab resistance.

Human CD20 is a B-cell lineage-specific marker expressed by normal and leukemic B cells from the pre-B to the plasma-cell stages and is a target for rituximab (RTX) immunotherapy. A CD20 reverse transcriptase-polymerase chain reaction (PCR) on B-cell lines cDNA yielded a short PCR product (DeltaCD20) corresponding to a spliced mRNA transcript linking the exon 3 and exon 7 ends. We established here that this novel, alternatively spliced CD20 transcript is expressed and detectable at various levels in leukemic B cells, lymphoma B cells, in vivo tonsil- or in vitro CD40L-activated B cells, and Epstein-Barr virus (EBV)-transformed B cells, but not in resting CD19(+)- or CD20(+)-sorted B cells from peripheral blood or bone marrow of healthy donors. The truncated CD20 sequence is within the reading frame, codes a protein of 130 amino acids ( approximately 15-17 kDa) lacking large parts of the 4 transmembrane segments, suggesting that DeltaCD20 is a nonanchored membrane protein. We demonstrated the translation into a DeltaCD20 protein which is associated with the membrane CD20 protein and showed its involvement in RTX resistance. Study of patient samples before and after RTX resistance or escape confirms our in vitro findings.

Genetics and Epigenetics in Neoplasms with Plasmacytoid Dendritic Cells.

Plasmacytoid Dendritic Cells (pDC) are type I interferon (IFN)-producing cells that play a key role in immune responses. Two major types of neoplastic counterparts for pDC are now discriminated: Blastic pDC Neoplasm (BPDCN) and Mature pDC Proliferation (MPDCP), associated with myeloid neoplasm. Two types of MPDCP are now better described: Chronic MyeloMonocytic Leukemia with pDC expansion (pDC-CMML) and Acute Myeloid Leukemia with pDC expansion (pDC-AML). Differential diagnosis between pDC-AML and BPDCN is particularly challenging, and genomic features can help for diagnosis. Here, we systematically review the cytogenetic, molecular, and transcriptional characteristics of BPDCN and pDC-AML. BPDCN are characterized by frequent complex karyotypes with recurrent MYB/MYC rearrangements as well as recurrent deletions involving ETV6, IKZF1, RB1, and TP53 loci. Epigenetic and splicing pathways are also particularly mutated, while original processes are dysregulated, such as NF-kB, TCF4, BCL2, and IFN pathways; neutrophil-specific receptors; and cholinergic signaling. In contrast, cytogenetic abnormalities are limited in pDC-AML and are quite similar to other AML. Interestingly, RUNX1 is the most frequently mutated gene (70% of cases). These typical genomic features are of potential interest for diagnosis, and also from a prognostic or therapeutic perspective.

Protein Arginine Methyltransferases as Therapeutic Targets in Hematological Malignancies.

Arginine methylation is a common post-translational modification affecting protein activity and the transcription of target genes when methylation occurs on histone tails. There are nine protein arginine methyltransferases (PRMTs) in mammals, divided into subgroups depending on the methylation they form on a molecule of arginine. During the formation and maturation of the different types of blood cells, PRMTs play a central role by controlling cell differentiation at the transcriptional level. PRMT enzymatic activity is necessary for many cellular processes in hematological malignancies, such as the activation of cell cycle and proliferation, inhibition of apoptosis, DNA repair processes, RNA splicing, and transcription by methylating histone tails' arginine. Chemical tools have been developed to inhibit the activity of PRMTs and have been tested in several models of hematological malignancies, including primary samples from patients, xenografts into immunodeficient mice, mouse models, and human cell lines. They show a significant effect by reducing cell viability and increasing the overall survival of mice. PRMT5 inhibitors have a strong therapeutic potential, as phase I clinical trials in hematological malignancies that use these molecules show promising results, thus, underlining PRMT inhibitors as useful therapeutic tools for cancer treatment in the future.