DUSP6 Mediates Resistance to JAK2 Inhibition and Drives Myeloproliferative Neoplasm Disease Progression

Abstract Myeloproliferative neoplasms (MPNs) are clonally derived from hematopoietic stem/progenitor cells (HSPCs) and typically harbor somatic mutations in one of three genes (JAK2, CALR, MPL) leading to aberrant activation of JAK-STAT signaling. While small molecule inhibitors of JAK2 provide symptomatic benefit for MPN patients, they do not eradicate the underlying malignant clone, nor do they prevent disease progression. Chronic MPNs exhibit a propensity for transformation to secondary acute myeloid leukemia (sAML), for which the underlying mechanisms remain poorly understood, resulting in limited treatment options and dismal clinical outcomes. To understand alterations to the transcriptional landscape underlying MPN disease progression, we performed bulk transcriptome profiling on myelofibrosis (MF) and sAML patient CD34+ HSPCs. Differential gene expression analysis revealed upregulation of dual-specificity phosphatase 6 (DUSP6), which encodes a MAPK phosphatase that regulates ERK signaling, in sAML CD34+ cells. Elevated DUSP6 protein expression accompanying disease progression was confirmed via MPN patient bone marrow immunofluorescence and imaging mass cytometry analysis. We performed further single cell RNA sequencing (scRNA-seq) in conjunction with TotalSeq surface protein marker detection on more than 50,000 sorted CD34+ cells of serial samples from three patients at chronic MPN and sAML stages, and two healthy controls, which revealed DUSP6 among the top 21 genes elevated in all three paired samples across disease progression. Subsequent differentiation trajectory pseudotime analysis demonstrated concomitant elevation of DUSP6 across state trajectories and disease progression. Genetic and pharmacologic targeting of DUSP6 followed by biochemical and mass cytometry analysis identified signaling inhibition through S6 and JAK/STAT, establishing them as novel, non-canonical effectors of DUSP6. DUSP6 inhibition also led to potent suppression of cell proliferation, induction of apoptosis and cell cycle arrest, and reduction of inflammatory cytokine production in primary MPN samples. Furthermore, ectopic DUSP6 expression augmented proliferation and mediated JAK2 inhibitor resistance, while DUSP6 inhibition reduced colony-forming potential of JAK2 inhibitor-persistent patient cells. Mechanistically, DUSP6 suppression dampened S6 signaling via inhibition of RSK1 (RPS6KA1), which we identified as a second indispensable candidate associated with poor clinical outcome via Kaplan-Meier overall survival (Log-rank p = 0.0005) and multivariate (RPS6KA1 expression hazard ratio = 1.60, 95% confidence interval: 1.10, 2.34) analyses of the TCGA LAML cohort. Strong correlation was observed (r = 0.68; p = 0.0009) between RPS6KA1 and DUSP6 expression in CD34+ HSPCs, and pharmacologic inhibition of RSK1 with BI-D1870 suppressed proliferation and colony formation across AML cell lines and primary samples. DUSP6 inhibition in vivo via small molecule inhibitor BCI resolved pathologically elevated hematocrit and white blood cell counts and reduced splenomegaly in Jak2 V617F knock-in mice. In the MPL W515L retroviral transplant model, BCI suppressed leukocytosis while reducing reticulin fibrosis and prolonging survival. In patient-derived xenograft (PDX) model of NSGS mice engrafted with sAML patient CD34+ cells, BCI treatment or DUSP6 knockdown reduced peripheral blood hCD45+ engraftment. Importantly, BCI treatment did not pathologically cause cytopenias or decrease spleen weights in wild-type mice, nor did it reduce hCD45+ engraftment in NSGS PDX mice engrafted with healthy donor CD34+ cells. Lastly, NSGS PDX mice engrafted with MF patient CD34+ cells ectopically expressing DUSP6 demonstrated marked leukocytosis, splenomegaly, and early lethality. These findings underscore DUSP6 in driving MPN disease progression and therapeutic resistance, and highlight the DUSP6-RSK1 axis as a novel, druggable pathway in myeloid malignancies. Figure 1 Figure 1. Disclosures Oh: Abbvie: Membership on an entity's Board of Directors or advisory committees; Blueprint Medicines: Membership on an entity's Board of Directors or advisory committees; Celgene Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Constellation: Membership on an entity's Board of Directors or advisory committees; CTI Biopharma: Membership on an entity's Board of Directors or advisory committees; Disc Medicine: Membership on an entity's Board of Directors or advisory committees; Geron: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees; Kartos Therapeutics: Membership on an entity's Board of Directors or advisory committees; PharamaEssentia: Membership on an entity's Board of Directors or advisory committees; Sierra Oncology: Membership on an entity's Board of Directors or advisory committees.

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Lower Hematopoietic Progenitor Cell Counts and Yields at Subsequent Donations Is Influenced By a Shorter Inter-Donation Interval between the First and Subsequent Mobilizations

Blood ◽

10.1182/blood-2019-123492 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 1962-1962

Author(s):

Sandhya R. Panch ◽

Brent R. Logan ◽

Jennifer A. Sees ◽

Bipin N. Savani ◽

Nirali N. Shah ◽

...

Keyword(s):

Stem Cell ◽

Board Of Directors ◽

Peripheral Blood ◽

Research Funding ◽

Time Interval ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Peripheral Blood Cd34 ◽

Cell Counts ◽

Cd34 Cells

Introduction: Approximately 7% of unrelated hematopoietic stem cell (HSC) donors are asked to donate a subsequent time to the same or different recipient. In a recent large CIBMTR study of second time donors, Stroncek et al. incidentally found that second peripheral blood stem cell (PBSC) collections had lower total CD34+ cells, CD34+ cells per liter of whole blood processed, and CD34+ cells per kg donor weight. Based on smaller studies, the time between the two independent PBSC donations (inter-donation interval) as well as donor sex, race and baseline lymphocyte counts appear to influence CD34+ cell yields at subsequent donations. Our objective was to retrospectively evaluate factors contributory to CD34+ cell yields at subsequent PBSC donation amongst NMDP donors. Methods. The study population consisted of filgrastim (G-CSF) mobilized PBSC donors through the NMDP/CIBMTR between 2006 and 2017, with a subsequent donation of the same product. evaluated the impact of inter-donation interval, donor demographics (age, BMI, race, sex, G-CSF dose, year of procedure, need for central line) and changes in complete blood counts (CBC), on the CD34+ cell yields/liter (x106/L) of blood processed at second donation and pre-apheresis (Day 5) peripheral blood CD34+ cell counts/liter (x106/L) at second donation. Linear regression was used to model log cell yields as a function of donor and collection related variables, time between donations, and changes in baseline values from first to second donation. Stepwise model building, along with interactions among significant variables were assessed. The Pearson chi-square test or the Kruskal-Wallis test compared discrete variables or continuous variables, respectively. For multivariate analysis, a significance level of 0.01 was used due to the large number of variables considered. Results: Among 513 PBSC donors who subsequently donated a second PBSC product, clinically relevant decreases in values at the second donation were observed in pre-apheresis CD34+ cells (73.9 vs. 68.6; p=0.03), CD34+cells/L blood processed (32.2 vs. 30.1; p=0.06), and total final CD34+ cell count (x106) (608 vs. 556; p=0.02). Median time interval between first and second PBSC donations was 11.7 months (range: 0.3-128.1). Using the median pre-apheresis peripheral blood CD34+ cell counts from donation 1 as the cut-off for high versus low mobilizers, we found that individuals who were likely to be high or low mobilizers at first donation were also likely to be high or low mobilizers at second donation, respectively (Table 1). This was independent of the inter-donation interval. In multivariate analyses, those with an inter-donation interval of >12 months, demonstrated higher CD34+cells/L blood processed compared to donors donating within a year (mean ratio 1.15, p<0.0001). Change in donor BMI was also a predictor for PBSC yields. If donor BMI decreased at second donation, so did the CD34+cells/L blood processed (0.74, p <0.0001). An average G-CSF dose above 960mcg was also associated with an increase in CD34+cells/L blood processed compared to donors who received less than 960mcg (1.04, p=0.005). (Table 2A). Pre-apheresis peripheral blood CD34+ cells on Day 5 of second donation were also affected by the inter-donation interval, with higher cell counts associated with a longer time interval (>12 months) between donations (1.23, p<0.0001). Further, independent of the inter-donation interval, GCSF doses greater than 960mcg per day associated with higher pre-apheresis CD34+ cells at second donation (1.26, p<0.0001); as was a higher baseline WBC count (>6.9) (1.3, p<0.0001) (Table 2B). Conclusions: In this large retrospective study of second time unrelated PBSC donors, a longer inter-donation interval was confirmed to be associated with better PBSC mobilization and collection. Given hematopoietic stem cell cycling times of 9-12 months in humans, where possible, repeat donors may be chosen based on these intervals to optimize PBSC yields. Changes in BMI are also to be considered while recruiting repeat donors. Some of these parameters may be improved marginally by increasing G-CSF dose within permissible limits. In most instances, however, sub-optimal mobilizers at first donation appear to donate suboptimal numbers of HSC at their subsequent donation. Disclosures Pulsipher: CSL Behring: Membership on an entity's Board of Directors or advisory committees; Miltenyi: Research Funding; Bellicum: Consultancy; Amgen: Other: Lecture; Jazz: Other: Education for employees; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Medac: Honoraria. Shaw:Therakos: Other: Speaker Engagement.

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Plerixafor (Mozobi ®)Plus G-CSF Is More Effective Than Placebo Plus G-CSF in Mobilizing CD34+ Hematopoietic Stem Cells in Patients with Multiple Myeloma Who Have Low (<20 cells/μl) Peripheral Blood CD34+ Cell Count.

Blood ◽

10.1182/blood.v114.22.3230.3230 ◽

2009 ◽

Vol 114 (22) ◽

pp. 3230-3230 ◽

Cited By ~ 1

Author(s):

Auayporn P. Nademanee ◽

Edward Stadtmauer ◽

Ivana N Micallef ◽

Patrick Stiff ◽

Sachin Marulkar ◽

...

Keyword(s):

Placebo Group ◽

Cell Count ◽

Board Of Directors ◽

Research Funding ◽

Fold Increase ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Cell Counts ◽

Cd34 Cells ◽

Equity Ownership

Abstract Abstract 3230 Poster Board III-167 Background Pre-apheresis peripheral blood (PB) CD34+ cells of < 20 cells/μl is a significant risk factor for poor hematopoietic stem cell (HSC) mobilization and collection in patients with multiple myeloma (MM) undergoing autologous HSC transplantation (auto-HSCT). PB CD34+ cells are routinely monitored to optimize the timing and success of HSC collection after mobilization with cytokines ± chemotherapy. This analysis was designed to compare the efficacy of plerixafor + G-CSF to placebo + G-CSF for mobilization in patients with MM who had pre-apheresis PB CD34+ cell counts < 20 cells/μl. We hypothesized that the addition of plerixafor to G-CSF would improve the stem cell yield in these patients with baseline CD34+ cells < 20 cells/μl. Methods Data were obtained from a prospective, randomized, double-blind, placebo-controlled, phase 3 clinical trial that compared the safety and efficacy of plerixafor (0.24 mg/kg/day SC) + G-CSF (10 μg/kg/day) to placebo + G-CSF for mobilization and auto-HSCT in patients with MM. PB CD34+ cell count was measured on Day 4, prior to first plerixafor/placebo dose, and on Day 5, 10-11 hours post study treatment. The proportion of patients achieving the minimal (≥2 × 106 CD34+ cells/kg) or optimal (≥6 × 106 CD34+ cells/kg) cell doses in 2 apheresis days, apheresis yields, and time to engraftment were compared between the plerixafor and placebo groups for PB CD34+ cell count <10 cells/μl (PB<10) and <20 cells/μl (PB<20). Results In the plerixafor group (n=148), 27 (18%) and 56 (38%) patients had Day 4 PB CD34+ cells/μl <10 and <20 which was as expected identical to the 30 (19%) and 60 (39%) patients in the placebo group, respectively (n=154). Patient characteristics were similar in both groups. Plerixafor + G-CSF resulted in a statistically significant increase in the absolute PB CD34+ cells/ml on Day 5 compared to placebo + G-CSF (p<0.001; Table 1). For patients with PB <10, the median fold increase in PB CD34+ cells in the plerixafor (n = 27) vs. placebo (n = 30) groups was 9.6 vs. 2 (p<0.001). Similarly, for patients with PB <20 the median fold increase in PB CD34+ cells in the plerixafor (n = 56) vs. placebo (n = 60) groups was 6.6 vs. 2 (p<0.001).The median CD34+ cell yield after 2 aphereses was significantly higher in the plerixafor vs. placebo group: 5.44 vs.1.68 × 106 cells/kg (p<0.001; PB<10) and 7.06 vs. 3.27 × 106 cells/kg (p<0.001; PB <20). The proportion of patients achieving ≥2 × 106 CD34+ cells/kg in 2 aphereses was significantly higher in the plerixafor group compared to the placebo group: 92.6% vs. 43.3 % in patients with PB<10 (p<0.001), and 94.6% vs. 66.7% in patients with PB<20 (p<0.001). Similarly, the proportion of patients achieving ≥6 × 106 CD34+ cells/kg in 2 apheresis days was significantly higher in the plerixafor vs. placebo group: 40.7% vs. 3.3 % in patients with PB<10 (p<0.001), and 55.4% vs. 15% in patients with PB<20 (p<0.001). The median time to platelet (19-20 days) and neutrophil (11 days) engraftment was similar in both groups. Conclusions These data demonstrate that in patients with MM who are predicted to fail mobilization based on low PB CD34+ cell count, the addition of plerixafor to G-CSF allows for 2-day collection of the minimal and optimal cell dose in a greater proportion of patients compared to G-CSF alone. Thus, addition of plerixafor to G-CSF can decrease the risk of poor mobilization in patients with MM who have PB CD34+ cell counts < 20 or even < 10 cells/μl. Disclosures Nademanee: Genzyme Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Stadtmauer:Genzyme Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Micallef:Genzyme Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding. Stiff:Genzyme Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Marulkar:Genzyme Corporation: Employment, Equity Ownership. Calandra:Genzyme Corporation: Consultancy, Equity Ownership. DiPersio:Genzyme: Honoraria.

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Plerixafor (Mozobil ®)Plus G-CSF Is Effective in Mobilizing Hematopoietic Stem Cells in Patients with Concurrent Thrombocytopenia Undergoing Autologous Hematopoietic Stem Cell Transplantation.

Blood ◽

10.1182/blood.v114.22.3229.3229 ◽

2009 ◽

Vol 114 (22) ◽

pp. 3229-3229 ◽

Cited By ~ 1

Author(s):

Ivana N Micallef ◽

Eric Jacobsen ◽

Paul Shaughnessy ◽

Sachin Marulkar ◽

Purvi Mody ◽

...

Keyword(s):

Stem Cell ◽

Platelet Count ◽

Board Of Directors ◽

Research Funding ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Platelet Counts ◽

Cd34 Cells ◽

Low Platelet Count ◽

Equity Ownership

Abstract Abstract 3229 Poster Board III-166 Introduction Low platelet count prior to mobilization is a significant predictive factor for mobilization failure in patients with non-Hodgkin's lymphoma (NHL) or Hodgkin's disease (HD) undergoing autologous hematopoietic stem cell (HSC) transplantation (auto-HSCT; Hosing C, et al, Am J Hematol. 2009). The purpose of this study is to assess the efficacy of HSC mobilization with plerixafor plus G-CSF in patients with concomitant thrombocytopenia undergoing auto-HSCT. Methods Patients who had failed successful HSC collection with any mobilization regimen were remobilized with plerixafor plus G-CSF as part of a compassionate use program (CUP). Mobilization failure was defined as the inability to collect 2 ×106 CD34+ cells/kg or inability to achieve a peripheral blood count of ≥10 CD34+ cells/μl without having undergone apheresis. As part of the CUP, G-CSF (10μg/kg) was administered subcutaneously (SC) every morning for 4 days. Plerixafor (0.24 mg/kg SC) was administered in the evening on Day 4, approximately 11 hours prior to the initiation of apheresis the following day. On Day 5, G-CSF was administered and apheresis was initiated. Plerixafor, G-CSF and apheresis were repeated daily until patients collected the minimum of 2 × 106 CD34+ cells/kg for auto-HSCT. Patients in the CUP with available data on pre-mobilization platelet counts were included in this analysis. While patients with a platelet count <85 × 109/L were excluded from the CUP, some patients received waivers and were included in this analysis. Efficacy of remobilization with plerixafor + G-CSF was evaluated in patients with platelet counts ≤ 100 × 109/L or ≤ 150 × 109/L. Results Of the 833 patients in the plerixafor CUP database, pre-mobilization platelet counts were available for 219 patients (NHL=115, MM=66, HD=20 and other=18.). Of these, 92 patients (NHL=49, MM=25, HD=8 and other=10) had pre-mobilization platelet counts ≤ 150 × 109/L; the median platelet count was 115 × 109/L (range, 50-150). The median age was 60 years (range 20-76) and 60.4% of the patients were male. Fifty-nine patients (64.1%) collected ≥2 × 109 CD34+ cells/kg and 13 patients (14.1%) achieved ≥5 × 106 CD34+ cells/kg. The median CD34+ cell yield was 2.56 × 106 CD34+ cells/kg. The proportion of patients proceeding to transplant was 68.5%. The median time to neutrophil and platelet engraftment was 12 days and 22 days, respectively. Similar results were obtained when efficacy of plerixafor + G-CSF was evaluated in 29 patients with platelet counts ≤ 100 × 109/L (NHL=12, MM=10, HD=3 and other=4). The median platelet count in these patients was 83 × 109/L (range, 50-100). The median age was 59 years (range 23-73) and 60.4% of the patients were male. The minimal and optimal cell dose was achieved in 19(65.5%) and 3(10.3%) patients, respectively. The median CD34+ cell yield was 2.92 × 106 CD34+ cells/kg. The proportion of patients proceeding to transplant was 62.1%. The median time to neutrophil and platelet engraftment was 12 days and 23 days, respectively. Conclusions For patients mobilized with G-CSF alone or chemotherapy ±G-CSF, a low platelet count prior to mobilization is a significant predictor of mobilization failure. These data demonstrate that in patients with thrombocytopenia who have failed prior mobilization attempts, remobilization with plerixafor plus G-CSF allows ∼65% of the patients to collect the minimal cell dose to proceed to transplantation. Thus, in patients predicted or proven to be poor mobilizers, addition of plerixafor may increase stem cell yields. Future studies should investigate the efficacy of plerixafor + G-CSF in front line mobilization in patients with low platelet counts prior to mobilization. Disclosures Micallef: Genzyme Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding. Jacobsen:Genzyme Corporation: Research Funding. Shaughnessy:Genzyme Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Marulkar:Genzyme Corporation: Employment, Equity Ownership. Mody:Genzyme Corporation: Employment, Equity Ownership. van Rhee:Genzyme Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

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Diacylglycerol Enhances Hematopoietic Stem/Progenitor Cell Development and Engraftment Via MAP Kinase Activation

Blood ◽

10.1182/blood.v122.21.174.174 ◽

2013 ◽

Vol 122 (21) ◽

pp. 174-174

Author(s):

Vera Binder ◽

Pulin Li ◽

Francesca Barrett ◽

Alex Leung ◽

Leonard I. Zon

Keyword(s):

Cord Blood ◽

Map Kinase ◽

Board Of Directors ◽

Marrow Transplantation ◽

Fluorescent Protein ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Cd34 Cells ◽

Equity Ownership ◽

Marrow Cells

Abstract Hematopoietic stem and progenitor cells (HSPCs) are exposed to a variety of intrinsic and extrinsic factors regulating all processes needed during development, and for successful engraftment after transplantation. In order to decipher the molecular pathways that may promote engraftment of HSPCs after marrow transplantation, we performed a competitive transplantation screen using chemical genetics in zebrafish. Green fluorescent protein-labeled kidney marrow cells (equivalent to mammalian bone marrow cells) were treated ex vivo with single compounds of a chemical library of known biologically active compounds, and administered by retro-orbital venous injection to lethally irradiated recipient zebrafish. About 500 chemicals were screened. Untreated kidney marrow cells labeled with a red fluorescent protein were used as competitors. Imaging-based assessment of short-term engraftment demonstrated that 1,2-Didecanoylglycerol, a membrane permeable but non-physiologic analogue of diacylglycerol (DAG), significantly improved engraftment compared to competitor cells. Follow-up by FACS analysis showed a 3.5 fold increase of long-term repopulating units after DAG treatment. To interrogate whether DAG treatment not only affects HSPCs under transplant conditions, but also during normal embryonic development, we treated zebrafish embryos within the time window of HSC formation in the dorsal aorta. DAG treatment increased expression of the HSPC markers Runx1 and c-myb in the AGM (Aorto-Gonad-Mesonephros). Treatment after HSC specification also led to an upregulation of HSPC markers in the caudal hematopoietic tissue (equivalent to fetal liver in mammals). These data suggest that DAG affects not only HSC formation, but also migration and engraftment of HSPCs as hematopoiesis transitions from the AGM to the CHT during development. To determine whether HSPCs respond to DAG in a cell autonomous manner, and to identify the underlying molecular mechanism, we treated human CD34+ cells from umbilical cord blood with DAG and performed RNA-seq analysis. Ingenuity Pathway Analysis of the 395 differentially expressed genes (q-value < 0.05) implicated the MAP kinase pathway as an upstream regulator. Human Phosphokinase array analysis of treated CD34+ showed ERK 1/2 activation. DAG is known to activate Protein Kinase C (PKC) with subsequent Raf kinase phosphorylation, which has the potential to activate ERK. Co-treatment of CD34+ cells with DAG and the ERK inhibitor PD98059 blocked upregulation of downstream ERK-targets (e.g. AREG, CSF2, EGR1, HMOX, SERPINE1, DUSP4, DUSP6), whereas the PI3K family inhibitor LY294002 and the p38 MAP kinase inhibitor SB202190 did not alter the effect of DAG on expression of these genes. This demonstrates that DAG activates ERK and its downstream targets. Our competitive marrow transplantation-based chemical screen has led to the discovery of 1,2-Didecanoylglycerol as a novel modulator of HSPC development and engraftment after transplantation. This discovery may be of clinical relevance to marrow or cord blood hematopoietic stem cell transplantation. Disclosures: Zon: FATE Therapeutics, Inc: Consultancy, Equity Ownership, Founder Other, Membership on an entity’s Board of Directors or advisory committees, Patents & Royalties; Stemgent, Inc: Consultancy, Membership on an entity’s Board of Directors or advisory committees, Stocks, Stocks Other; Scholar Rock: Consultancy, Equity Ownership, Founder, Founder Other, Membership on an entity’s Board of Directors or advisory committees, Patents & Royalties.

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RON Kinase Is a Novel Therapeutic Target for Philadelphia-Negative Myeloproliferative Neoplasms

Blood ◽

10.1182/blood-2021-148192 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 1462-1462

Author(s):

Lindsay Meg Gurska ◽

Rachel Okabe ◽

Meng Maxine Tong ◽

Daniel Choi ◽

Kristina Ames ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Research Funding ◽

Myeloproliferative Neoplasms ◽

Marrow Transplant ◽

Jak Inhibitor ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Stat Signaling ◽

Genetic Deletion

Abstract The Philadelphia-chromosome negative myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocytosis (ET), and primary myelofibrosis (PMF), are clonal hematopoietic stem cell disorders characterized by the proliferation of one or more myeloid lineage compartments. Activation of JAK/STAT signaling is a major driver of all Ph-negative MPNs. During disease progression, MPN patients experience increased pro-inflammatory cytokine secretion, leading to remodeling of the bone marrow microenvironment and subsequent fibrosis. The JAK inhibitor ruxolitinib is an approved targeted therapy for MPN patients and has shown promise in its ability to reduce splenomegaly and the cytokine storm observed in patients. However, JAK inhibitors alone are not sufficient to reduce bone marrow fibrosis or to eliminate the JAK2-mutated clone. Furthermore, JAK inhibitor persistence, or reactivation of JAK/STAT signaling upon chronic JAK inhibitor treatment, has been observed in both MPN mouse models and MPN patients. Therefore, there is an urgent need for new treatment options in MPN. The tyrosine kinase RON, a member of the MET kinase family, has well-characterized roles in erythroblast proliferation and pro-inflammatory cytokine production. RON can be phosphorylated by JAK2 to stimulate erythroblast proliferation. However, the role of RON in MPN pathogenesis is unknown. We found that the ALK/MET/RON/ROS1 inhibitor crizotinib inhibited colony formation by MPN patient CD34+ cells, regardless of their disease subtype, mutation status, or JAK2 inhibitor treatment history (Figure 1A). To determine whether this is due to inhibition of the JAK/STAT signaling pathway, we performed phospho-flow cytometry of STAT3 and STAT5 in myelofibrosis patient erythroblasts treated with crizotinib ex vivo as well as Western blot analysis in the JAK2-mutated cell lines SET2 and HEL. We found that crizotinib inhibits the phosphorylation of JAK2, STAT3, and STAT5 (Figure 1B). Since crizotinib has not been reported to directly inhibit JAK2, we asked whether these effects of crizotinib in MPN cells could be explained by RON inhibition. Consistent with this hypothesis, we observed that shRNA knockdown of multiple RON isoforms also decreases the phosphorylation of JAK2, STAT5, and STAT3 in HEL cells (Figure 1C-D). To determine whether crizotinib can alter the MPN disease course in vivo, we tested crizotinib by oral gavage in the MPLW515L bone marrow transplant murine model of myelofibrosis at 100mg/kg daily for 2 weeks. We showed that crizotinib decreased the disease burden of MPL-W515L mice, as evidenced by decreased spleen and liver weights (Figure 1E). To determine the effects of RON genetic deletion on MPN pathogenesis, we tested whether genetic deletion of Stk (mouse gene for RON) impairs disease progression in the JAK2V617F bone marrow transplant MPN model by transplanting Stk-/- c-Kit+ bone marrow cells transduced with the JAK2V617F-GFP retrovirus into lethally irradiated recipients. We observed a significant delay in disease onset in Stk-/- transplant recipients compared to WT controls (Figure 1F). However, we found that Stk-/- mice have normal numbers of hematopoietic stem and progenitor cells, and normal bone marrow myeloid colony forming capacity, suggesting that RON is a safe therapeutic target. To determine whether RON plays a role in the JAK inhibitor persistence phenotype, we generated persistent cells by treating SET2 cells with increasing doses of ruxolitinib over 8 weeks, and confirmed persistent proliferation and JAK/STAT activation. Interestingly, we found that RON phosphorylation is enhanced in JAK inhibitor persistent cells, and that dual inhibition of RON and JAK2 overcomes JAK inhibitor persistence in SET2 cells (Figure 1G-H), suggesting that RON may potentiate the JAK2 persistence phenotype in response to ruxolitinib. Importantly, we showed by immunoprecipitation that phospho-RON and phospho-JAK2 physically interact in JAK inhibitor persistent SET2 cells, and that this interaction is disrupted by crizotinib (Figure 1I). In summary, our data demonstrate that RON kinase is a novel mediator of JAK/STAT signaling in MPNs, and that it plays a particularly important role in JAK inhibitor persistence. Our work suggests that therapeutic strategies to inhibit RON, such as crizotinib, should be investigated in MPN patients. Figure 1 Figure 1. Disclosures Halmos: Guardant Health: Membership on an entity's Board of Directors or advisory committees; Apollomics: Membership on an entity's Board of Directors or advisory committees; TPT: Membership on an entity's Board of Directors or advisory committees; Eli-Lilly: Research Funding; Advaxis: Research Funding; Blueprint: Research Funding; Elevation: Research Funding; Mirati: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; GSK: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Boehringer-Ingelheim: Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Astra-Zeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Membership on an entity's Board of Directors or advisory committees, Research Funding. Gritsman: iOnctura: Research Funding.

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Expression of HMGA2 Collaborates with JAK2V617F to Progress Myeloproliferative Neoplasms

Blood ◽

10.1182/blood.v126.23.482.482 ◽

2015 ◽

Vol 126 (23) ◽

pp. 482-482

Author(s):

Koki Ueda ◽

Kazuhiko Ikeda ◽

Kazuei Ogawa ◽

Akiko Shichishima-Nakamura ◽

Kotaro Shide ◽

...

Keyword(s):

Disease Progression ◽

Conflicts Of Interest ◽

Myeloproliferative Neoplasms ◽

Jak2 V617f ◽

Primary Myelofibrosis ◽

Extramedullary Hematopoiesis ◽

Hematopoietic Stem ◽

Cell Counts ◽

Epigenetic Modifiers ◽

One Year

Abstract Myeloproliferative neoplasms (MPN) are characterized by chronic proliferation of myeloid cells, extramedullary hematopoiesis and occasional leukemic transformation. Mutations in JAK2, CALR and MPL have been established as drivers of myeloproliferative phenotype, but their roles in disease progression with clonal expansion remain unclear. In addition, studies have shown mutations in epigenetic modifiers including TET2, DNMT3A, ASXL1 and EZH2, and aberrant expressions of microRNAs in MPN, but downstream of these changes is also largely unknown. Recently, we showed high expression of HMGA2 mRNA partly correlated with reduced microRNA let-7 in granulocytes of patients with MPN, including 100% patients with primary myelofibrosis (MF) and 20% polycythemia vera and essential thrombocythemia (Harada-Shirado et al, Brit J Haematol, 2015). In mice, loss of epigenetic modifiers such as BMI1 and EZH2, along with the Arf/Ink4a knockout (Oguro et al, J Exp Med, 2012) or the JAK2 V617F (Sashida et al, ASH, 2013), leads to overexpression of HMGA2 with accelerating MPN. We have generated transgenic (Tg) mice of Hmga2 cDNA with truncated 3'UTR (ΔHmga2) lacking binding sites of let-7 thatrepresses expression of HMGA2 (Ikeda et al, Blood, 2011). Δ Hmga2 mice overexpress HMGA2 and develop MPN-like disease, and represent a clonal advantage in competitive repopulations with serial bone marrow (BM) transplants (BMT). Here, to clarify if HMGA2 affect JAK2 V617F+ hematopoiesis, we crossed Δ Hmga2+/- mice with JAK2 V617F+/- Tg mice (Shide et al, Leukemia, 2008). Δ Hmga2-/-JAK2 V617F-/- wild type (WT), Δ Hmga2+/-JAK2 V617F-/- (Δ Hmga2 -Tg), Δ Hmga2-/-JAK2 V617F+/- (JAK2 V617F-Tg) and Δ Hmga2+/-JAK2 V617F+/- (double-Tg) mice were born at expected Mendelian ratios and we could analyze 5 - 6 of each. At 3 months old, leukocytosis, thrombocytosis, anemia and splenomegaly were most severe in double-Tg compared with JAK2 V617F-Tg or Δ Hmga2 -Tg mice. Relative to WT, peripheral leukocyte and platelet counts were nearly 16- and 4-fold higher in double-Tg, while 3- and 2-fold higher in JAK2 V617F-Tg mice, respectively. Mean spleen weights were 0.067, 0.10, 0.83 and 2.8 g in WT, Δ Hmga2 -Tg, JAK2 V617F-Tg and double-Tg mice, while BM cell counts were 2.4, 2.8, 0.4 and 1.2 x 107/femur, respectively. However, JAK2 V617F-Tg and double-Tg equally showed MF whereas no MF was detected in WT and DHmga2-Tg, suggesting that HMGA2 partly recovers cellularity in fibrotic BM. In the absence and presence of JAK2 V617F, HMGA2 augments lineage- Sca1+ Kit+ cells (WT: Δ Hmga2-Tg: JAK2 V617F-Tg: double-Tg= 0.17%: 0.19%: 0.17%: 0.27% in BM cells), endogenous erythroid colonies (1: 11: 13: 21 CFU-E/104 BM cells) and CD71+ Ter119+ erythroblasts (23%: 29%: 5.7%: 10% in BM and 2.0%: 4.4%: 7.9%: 16% in spleen cells), indicating HMGA2 contributes to expansion of hematopoietic stem/progenitor cells (HSPC) and erythroid commitment in JAK2 V617F+ hematopoiesis. Most Δ Hmga2-Tg and JAK2 V617F-Tg survived for over one year, but all double-Tg mice died within 4 months after birth due to severe splenomegaly and MF with no acute leukemia. To study the effect of HMGA2 on JAK2 V617F+ HSPC activity, we performed BMT with 0.25 x 106 Ly5.2+Δ Hmga2-Tg, JAK2 V617F-Tg or double-Tg cells with 0.75 x 106 Ly5.1+ competitor WT cells to lethally irradiated Ly5.1+ WT mice. Proportions of Ly5.2+ cells were higher in recipients of Δ Hmga2 -Tg than double-Tg cells, while JAK2 V617F-Tg cells were almost rejected at 8 weeks after BMT. To confirm role of HMGA2 without let-7 repression in JAK2 V617F+ hematopoiesis, we performed another BMT with 1 x 104 KIT+ cells of JAK2 V617F-Tg mice transduced with retroviral vector of Hmga2 with each let-7 -site-mutated full-length 3'UTR (Hmga2-m7) to sublethally irradiated WT mice. Recipients of JAK2 V617F-Tg cells with Hmga2-m7 developed MPN-like disease, whereas donor cells were rejected in recipients of JAK2 V617F cells with empty vector. In conclusion, HMGA2 may play a crucial role in hematopoiesis harboring JAK2 V617F by expanding HSPC, leading to disease progression. Disclosures No relevant conflicts of interest to declare.

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Mgta-145, in Combination with Plerixafor in a Phase 1 Clinical Trial, Mobilizes Large Numbers of Human Hematopoietic Stem Cells and a Graft with Immunosuppressive Effects for Allogeneic Transplant

Blood ◽

10.1182/blood-2020-142804 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 31-32

Author(s):

Kevin A. Goncalves ◽

Sharon L. Hyzy ◽

Katelyn J. Hammond ◽

Patrick C. Falahee ◽

Haley Howell ◽

...

Keyword(s):

Single Dose ◽

Board Of Directors ◽

Phase 1 ◽

Allogeneic Transplant ◽

Publicly Traded ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Nsg Mice ◽

Healthy Donors ◽

Cd34 Cells

Background . The majority of hematopoietic stem cell (HSC) transplants are performed using peripheral blood mobilized with granulocyte-colony stimulating factor (G-CSF) given over 5 days. The goal of a successful transplant is to reliably mobilize optimal numbers of HSCs necessary for rapid and consistent multilineage engraftment. Infusion of mobilized allogeneic grafts results in significant acute and chronic graft-versus-host disease (GvHD) in up to 80% of allogeneic transplant recipients. A reliable and rapid method to mobilize HSC-rich grafts with reduced GvHD potential would be clinically meaningful. In a Phase 1 study of normal volunteers, MGTA-145 (GroβT), a CXCR2 agonist, when combined with plerixafor, a CXCR4 inhibitor, robustly and rapidly mobilized sufficient HSCs for a safe transplant after only a single day of dosing and apheresis/collection. Here, we phenotypically and functionally profile these mobilized grafts obtained from human volunteers and show that MGTA-145 + plerixafor mobilizes grafts with >10-fold higher engraftment potential (as measured by SCID-repopulating units in NSG mice), a marked reduction in xenogeneic GvHD, and enhanced overall survival compared to G-CSF or plerixafor alone grafts. Results . In healthy donors, a peak of 40 CD34+ cells/μL were mobilized with MGTA-145 + plerixafor (n=12 donors). 11 of 12 (92%) of these donors mobilized >20 CD34+ cells/μL with single day dosing compared to only 8 of 14 (57%) achieving the same CD34+ cell target treated with plerixafor alone. Eight donors were mobilized with a single dose of MGTA-145 + plerixafor and apheresed on the same day. A median of 4x106 (1.5-7.0x106) CD34+ cells/kg were obtained (n=8 donors) from a median 20 (13-20) L collection. 35.8 (18.5-40.9)% of these cells were CD90+CD45RA-, a CD34+ subset enriched for HSCs, compared to only 6.9 (5.3-9.0)% with G-CSF (p<0.001, n=3 donors). Mechanistically, MGTA-145 bound to CXCR2 on neutrophils and led to a modest and transient increase in plasma concentrations of matrix metalloproteinase 9 (MMP- 9), a downstream target on neutrophils. To assess engraftment, we transplanted mobilized peripheral blood cells from healthy donors after a 5-day regimen of G-CSF or a single dose of plerixafor alone or MGTA-145 + plerixafor at limit dilution into sublethally irradiated primary and secondary NSG mouse recipients (n=3 cell doses, n=7-8 mice/group). Multilineage human engraftment was measured by flow cytometry 16 weeks post-transplant and SCID-repopulating cell (SRC) number was calculated (Figure 1A). MGTA-145 + plerixafor mobilized grafts (n=4 donors) led to a 23-fold increase in engraftment compared to G-CSF mobilized grafts (p<0.001, n=3 donors) and 11-fold higher engraftment compared to plerixafor mobilized grafts (p<0.001, n=3 donors). Immune cell subsets (B, T, and NK cells and cell subsets) mobilized by MGTA-145 + plerixafor were similar to those mobilized by plerixafor alone. While CD3+ T-cell numbers were comparable between MGTA-145 + plerixafor and plerixafor alone, MGTA-145 + plerixafor mobilized 0.2 (0.0-0.6) x108/kg CD8+ T-cells, constituting 1.8 (0.5-4.8)% of the graft, a number and proportion significantly lower than that mobilized by either G-CSF or plerixafor alone. To determine the effect of the mobilization regimen on xenogeneic GvHD, we developed a xenograft GvHD model in NSG mice where 6x106 PBMCs from various graft sources were infused into sublethally-irradiated animals (n=3-6 donors per graft source). Notably, MGTA-145 + plerixafor mobilized grafts resulted in significantly less GvHD than G-CSF (p<0.01) or plerixafor (p<0.001) grafts (Figure 1B). In vivo cellular subset depletion studies suggested that the GvHD protective effect in MGTA-145 + plerixafor grafts may be in part due to immunosuppressive monocytes which were not present, or present to a lesser degree, in grafts from donors mobilized with G-CSF or plerixafor. Conclusions . These data demonstrate that MGTA-145 + plerixafor is a rapid, reliable, and G-CSF free method to obtain high numbers of HSCs with durable engraftment potential and a graft with highly immunosuppressive properties. These data suggest that MGTA-145 + plerixafor is an effective single-day mobilization/collection regimen for both autologous and allogeneic stem cell transplantation resulting in enhanced engraftment and reduced GvHD in this xenograft model. Disclosures Goncalves: Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Hyzy:Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company. Hammond:Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company. Falahee:Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company. Howell:Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company. Pinkas:Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company. Schmelmer:Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company. Hoggatt:Magenta Therapeutics: Consultancy, Current equity holder in publicly-traded company. Scadden:Magenta Therapeutics: Consultancy, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Devine:Magenta Therapeutics: Consultancy. DiPersio:Magenta Therapeutics: Membership on an entity's Board of Directors or advisory committees. Savage:Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company. Davis:Magenta Therapeutics: Current Employment, Current equity holder in publicly-traded company.

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Mouse Models of Myeloproliferative Neoplasms and Their Use In Preclinical Drug Testing

Blood ◽

10.1182/blood.v116.21.sci-35.sci-35 ◽

2010 ◽

Vol 116 (21) ◽

pp. SCI-35-SCI-35

Author(s):

Richard A. Van Etten

Keyword(s):

Board Of Directors ◽

Targeted Therapies ◽

Myeloproliferative Neoplasms ◽

Normal Population ◽

Hematopoietic Cells ◽

Advisory Committees ◽

Early Therapy ◽

Jak2 Inhibitor ◽

Advantages And Disadvantages ◽

Jak2 Inhibitors

Abstract Abstract SCI-35 The myeloproliferative neoplasms (MPNs) and related conditions, many of which are characterized by dysregulated tyrosine kinase (TK) signalling, can be modelled in mice by expressing the relevant mutant signalling molecules (for example, BCR-ABL1 or mutant JAK2) in mouse hematopoietic cells. There are two strategies to accomplish this: retroviral- or lentiviral gene transfer into hematopoietic cells followed by transplantation, and expression via a chromosomal transgene. Each method has advantages and disadvantages for modeling MPNs and for pre-clinical evaluation of molecularly targeted therapies. For BCR-ABL1, such preclinical studies have proven useful in predicting clinical responses to TK inhibitors in patients (Hu et al., Nat. Genet. 2004;36:453). The retroviral strategy has been used to model MPNs induced by JAK2V617F, JAK2 exon 12 mutants, and MPL W515L/K mutants (Lacout et al., Blood 2006;108:1652; Zaleskas et al., PLoS ONE 2006;1:e18; Pikman et al., PLoS Med. 2006;3:e270). For JAK2V617F, the models recapitulate predominantly the erythroid phenotype of PV, with polycythemia, splenomegaly, endogenous erythroid colonies (EEC), and progression to myelofibrosis (MF). Treatment with small molecule JAK2 inhibitors reverses polycythemia and splenomegaly, but the effects on EEC frequency, JAK2V617F allele burden, and MF are in general less profound, possibly reflecting a lack of discrimination between endogenous and mutant JAK2 by these drugs in vivo. MPL W515L induces more fulminant MPN and MF in mice, and while early therapy with a JAK2 inhibitor can prolong survival and decrease MF (Koppikar et al., Blood 2010;115:2919), it is less clear whether established MF responds to treatment. With the transgenic approach, a TK can be expressed at more physiologic levels. As JAK2V617F must associate with EpoR or MPL for signaling activity, competition between endogenous and mutant JAK2 might influence disease phenotype. Several transgenic models of JAK2V617F MPN have been published recently (Tiedt et al., Blood 2008;111:3931; Shide et al., Leukemia 2008;22:87), including “knock-in” models where JAK2V617F is conditionally expressed from the endogenous promoter (Akada et al., Blood 2010; 15:3589; Marty et al., Blood 2010;Epub May 14; Li et al., Blood 2010;Epub May 20). These models lend some experimental support for the concept that expression of JAK2V617F at levels similar to or higher than endogenous JAK2 causes erythrocytosis whereas lower expression favors thrombocytosis, but several variables, including origin of JAK2 and mouse strain, may confound the picture. The response of these transgenic mice to treatment with JAK2 inhibitors may differ from MPN patients in that they lack a normal population of HSC in their marrow and spleen, and are wholly dependent on JAK2V617F–associated hematopoiesis for blood cell production. Overall, these models should prove useful for guiding clinical trials of targeted therapies in the Ph− MPNs. Disclosures: Van Etten: AstraZeneca Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Cephalon Oncology: Membership on an entity's Board of Directors or advisory committees. Off Label Use: INCB18424 (JAK2 inhibitor) TG101348 (JAK2 inhibitor) AZD1480 (JAK2 inhibitor).

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Effect of Daratumumab-Containing Induction on CD34+ Hematopoietic Stem Cells before Autologous Stem Cell Transplantation in Multiple Myeloma

Blood ◽

10.1182/blood-2021-150360 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2764-2764

Author(s):

Ondrej Venglar ◽

Tereza Sevcikova ◽

Anjana Anilkumar Sithara ◽

Veronika Kapustova ◽

Jan Vrana ◽

...

Keyword(s):

Multiple Myeloma ◽

Stem Cell ◽

Board Of Directors ◽

Research Funding ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Platelet Recovery ◽

Cd34 Cells ◽

Fcm Analysis ◽

D 12

Abstract Introduction: Daratumumab (Dara) is an anti-CD38 monoclonal antibody representing a novel treatment agent for multiple myeloma (MM). Nonetheless, several studies have reported a Dara-related impairment of CD34+ hematopoietic stem cell (HSC) mobilization and post-autologous stem cell transplantation (ASCT) complications, including low yields of mobilized HSCs and delayed neutrophil engraftment. Impact of Dara on the mobilization process and HSCs remains poorly understood even though sufficient yields of CD34+ cells are necessary for a successful ASCT and subsequent patient recovery. Aims: To compare the effect of the Dara-containing (Dara-Bortezomib-Dexamethasone [D-VCd]) and conventional (Bortezomib-Thalidomide-Dexamethasone [VTd]) therapy on CD34+ HSCs. Methods: Transplant eligible MM patients were treated with D-VCd or VTd induction regimen followed by a cyclophosphamide + G-CSF mobilization and a high-dose melphalan D -1 before ASCT. Flow cytometry (FCM) screening of CD34+ subsets was performed in the bone marrow (BM) or apheresis product (AP) at three consecutive time points: 1) diagnostic BM (DG), 2) mobilization AP (MOB), 3) a day prior ASCT BM (D-1). Furthermore, RNA sequencing (RNAseq) of sorted CD34+ cells was performed on total RNA with ribo-depletion protocol in AP after the induction. D-VCd samples had lower RNA yields thus the D-VCd or VTd groups were processed as independent batches. Results: Clinical data revealed no significant differences in mobilization (p >0.050) likely due to a small cohort sizes (D-VCd n=5 vs VTd n=9), though a trend towards worse performance in D-VCd was observed. Median CD34+ cell yield was 3.08 vs 10.56 x 10 6/kg. Platelet recovery of >20x10 9/L was D+14 vs D+12 (range: 11-18 vs 10-16). Neutrophil recovery of >0.5x10 9/L was D+12 in both groups (range: 11-17 vs 11-12). In FCM analysis, DG (n=14), MOB D-VCd (n=5) vs VTd (n=9), D-1 D-VCd (n=7) vs VTd (n=15) were compared. CD34+ frequency (Fig. 1A) difference in MOB D-VCd vs VTd was insignificant (median: 1.15% vs 1.89%), whereas CD34+ fraction dropped in D-1 D-VCd (median: 0.52% vs 0.72%, p=0.027), albeit there was no significant reduction in D-1 D-VCd vs initial DG (median: 0.52% vs 0.45%). Differences in the distribution of certain HSC subsets were detected in the CD34+ pool (Fig. 1B-E). Frequency of multipotent progenitors (MPPs) (Fig. 1B) was increased in MOB D-VCd (median: 82.1% vs 66.2%, p=0.004). Frequency of lympho-myeloid-primed progenitor + granulocyte-monocyte progenitor (LMPP+GMP) (Fig. 1C) subset was reduced in D-VCd in both MOB (median: 1.7% vs 16.9%, p=0.042) and D-1 (median: 5.3% vs 14.0%; p=0.026). Erythro-myeloid progenitors (EMPs) (Fig. 1D) were reduced in MOB D-VCd (median: 10.7% vs 19.5%, p=0.042), while the frequency of EMPs increased in D-1 D-VCd (median: 20.8% vs 12.4%, p=0.045). No considerable differences were found in the expression of adhesion molecules CD44/HCAM or CD184/CXCR4. CD38 was strongly diminished in the whole D-VCd CD34+ fraction of MOB and D-1. To understand whether the differences in the mobilization efficacy after D-VCd induction were reflected in the expression profile of mobilized CD34+ cells, differential expression analysis was performed. Overall 133 significantly deregulated genes (p<0.05; log fold change >(-)1) between cohorts (D-VCd n=5 vs VTd n=5) were revealed (Fig. 2). Pathway analysis showed cellular response and localization as the most deregulated categories. The list of deregulated genes contained 25% of non-coding RNAs, some of which were linked to a protein localization in the cell (RN7SL1/2). The expression of adhesion molecules was inspected independently. Out of 59 HSC hallmark genes, only 8 were significantly altered in D-VCd. Interestingly, the main homing molecule CXCR4 seemed to be downregulated in D-VCd, while integrins A3 and B4 were upregulated. Conclusions: Despite the limited cohort sizes, a prospective trend of delayed neutrophil and platelet recovery was observed after D-VCd therapy. FCM analysis revealed a significant reduction of CD34+ subsets responsible, among others, for a reconstitution of neutrophils and megakaryocytes. A strong signal in transcriptome data which would potentially explain differential mobilization in D-VCd cohort was not detected, nevertheless, several genes with adhesive/homing and stem cell differentiation function were indeed altered. The results warrant further investigation. Figure 1 Figure 1. Disclosures Hajek: BMS: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharma MAR: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

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Multi-Lineage Dysplasia Assessment By Immunophenotype in Myeloproliferative Neoplasms (MPN): Correlation with Disease' Variant, Clinical Features and Molecular Genetics

Blood ◽

10.1182/blood-2019-125843 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 1668-1668

Author(s):

Francesco Mannelli ◽

Sara Bencini ◽

Benedetta Peruzzi ◽

Paola Guglielmelli ◽

Annalisa Pacilli ◽

...

Keyword(s):

Board Of Directors ◽

Myeloproliferative Neoplasms ◽

Expression Profiles ◽

Cell Number ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Phenotypic Profile ◽

Immature Cell ◽

Cell Compartments ◽

Disease Variant

Background. MPN are clonal disorders of hematopoietic stem cell (HSC) that include polycythemia vera (PV), essential thrombocytemia (ET) and myelofibrosis (MF), either secondary to ET-PV, or primary (PMF), including pre-fibrotic (pre-PMF) and overt. In MF, multi-lineage dysplasia (MLD) of varying degree can be detected by morphologic analysis of bone marrow (BM), but appraisal of MLD is intrinsically operator-dependent and lacks quantitative information. Multi-parameter flow cytometry (MFC) is used to study dysplasia by investigating aberrant antigen expression profiles during hematopoietic cells' differentiation and maturation, allowing: i) analysis of a much greater cell number; ii) standardization of data by referring to controls; iii) definition of scores to estimate MLD extent. Aim. The aim of the study was to assess MLD in MPN by MFC and correlate with disease' variant, clinical and biological features. Methods. Patients: pts were diagnosed according to 2016 WHO criteria. Driver and high molecular risk mutations (HMR) were determined. MFC: Different BM cell compartments were analyzed with a panel of 28 monoclonal antibodies (MoAb) by 2 acquisition steps: Step 1) HSC and progenitor (GMP and MEP) cells up to >5 x 106 cells/sample were studied by Lin/CD34/CD38/CD90/CD45/CD49f/CD45RA/CD135 MoAb. Step 2) Precursor and mature compartments (B-, neutrophilic, monocytic, erythroid, plasmacytoid dendritic cells, basophils) were identified within CD34+ and/or CD117+ subset. Uncommitted CD38+ precursors were obtained by subtraction. CD117-neg, maturing cells were identified by specific features, ie CD34, CD45 and scatter. MLD was assessed by 2 phenotypic scores: i) one validated by ELN in MDS (Ogata score) includes 4 parameters; ii) the second one, adapted from Matarraz et al (2010; Salamanca score), 63 parameters. Normal phenotypic profile was defined as the interval between mean value (M) ± 2SD per parameter in healthy donors' BM samples. Each parameter scored 0.5, 1 or 2 for values between M ± 2 SD and M ± 3 SD, M ± 3 SD and M ± 4 SD, and over M ± 4 SD of the normal profile, respectively. Results. 51 consecutive MPN pts at diagnosis were enrolled, including 30 MF (7 pre-PMF, 14 overt PMF, 9 post-PV/ET MF); 13 ET, 5 PV, 1 MPN-unclassifiable and 2 MDS/MPN. Median age was 59y (range 24-83). 19 (63.3%) MF patients had JAK2V617F, 9 (30.0%) CALR, 2 (6.7%) MPLW515L mutation. 11 pts (36.7%) harbored at least 1 HMR mutation. According to MIPSS, 6 (20.0%), 11 (36.7%) and 10 (33.3%) were low, intermediate and high risk. By comparing MF pts to controls and ET-PV, altered proportion of immature cell subsets was observed. Specifically, HSC and uncommitted progenitors in MF were increased of 3.8 and 1.5-fold, respectively whereas GMP and downstream precursors were significantly reduced 2 to >6-fold. No significant differences emerged comparing mature compartments, except for an increase of basophils and a decrease of pDC in MF subset (Table 1). When considering MLD, MF patients ranked higher scores for both the Ogata and Salamanca score. Furthermore, Salamanca score values had a trend to correlate with MIPSS risk categories, with median value of 7.75, 13.25 and 15.5 in low, intermediate and high category (KW test P=0.06). MF cases were separated according to Salamanca score ≥ or < to the median value of 13.5: pts with higher score were featured by significant differences in hemoglobin (11.9 vs 13.7 g/dL; P=.015), platelet count (330 vs 558 x109/L; P=.004), LDH (380 vs 275 U/L; P=.034), circulating CD34+ cells (60.4 vs 5.3/mL; P=.007). We also compared prePMF and ET pts, two categories with challenging differential diagnosis: prePMF displayed expansion of HSC (0.015) compared to ET (0.0056; P=0.028) and reduced proportions of downstream precursors, similar to what observed in MF vs non-MF comparison. Conversely, MLD scores were similar: Ogata 1.0 vs 1.0, Salamanca 9.0 vs 7.5 for ET and prePMF, respectively. Conclusions. The assessment of MLD by MFC correlated with MPN variants according to WHO; MF was associated with higher deviation from normal phenotypic profile. MLD scores delineated clinical phenotype and were consistent with MIPSS risk stratification. With the limits of number of pts analyzed, these preliminary data also support a biologic continuum of pre-PMF and MF, the first being characterized by abnormal expansion of immature cell compartments compared to ET but minimal signs of dysplastic maturation unlike overt MF. Disclosures Vannucchi: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Incyte: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Italfarmaco: Membership on an entity's Board of Directors or advisory committees; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

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