Comparison of the Transcriptomic Signatures in Pediatric and Adult CML

Introduction Pediatric chronic myeloid leukemia (CML) accounts for 10-15% of pediatric myeloid leukemias and 2-9% of all pediatric leukemias. There are several unique characteristics of CML diagnosed in children, adolescents, and young adults, compared to adults. They present with higher white blood counts and larger spleens, suggesting that the biology of pediatric CML is different from adult CML. We hypothesize that the differences in clinical presentation of pediatric CML patients are due to unique molecular characteristics that differ from adult CML patients. To test this hypothesis, we studied the transcriptomic signature of pediatric CD34+ CML cells compared to adult CML and normal age-matched bone marrow CD34+ cells. Methods CD34+ cells were isolated by FACS from pediatric CML (n=9), adult CML (n=10), pediatric normal (n=10) and adult normal (n=10) bone marrow samples. Total RNA was isolated from cells, and cDNA libraries were generated. Prepared libraries were sequenced on the Illumina HiSeq 4000 instrument. Raw sequences were trimmed and aligned to the hg38 reference genome with STAR/2.5.1b aligner. Gene level counts were determined with STAR -quantMode option using gene annotations from GENCODE (p5). Differential gene expression and pathway analysis were conducted with R/3.5.3. Counts were normalized with trimmed mean of M-values (TMM) from the EdgeR/ 3.24.3 package and further transformed with VOOM from the Limma/ 3.38.3 package. A linear model using the empirical Bayes analysis pipeline also from Limma was then used to obtain p-values, adjusted p-values and log-fold changes (LogFC). We performed three comparisons: (1) Pediatric CML vs Normal, (2) Adult CML vs Normal, and (3) Pediatric CML vs Adult CML. A False Discovery Rate (FDR) of £ .05 and absolute log2 fold-change > 1 was used to define differentially expressed genes in each comparison. Over-representation analysis was used to identify potentially unique pathways based on differentially expressed genes. Clinical and demographic features at diagnosis were extracted for pediatric and adult CML patients and compared using Fisher's exact test (categorical variables) or Wilcoxon rank sum test (continuous variables). Results Pediatric patients were diagnosed with CML at a median of 11 years (interquartile range (IQR): 10-14) compared to 54 years (IQR: 33-62) for adult patients. At diagnosis, pediatric patients had higher platelet counts (p=0.001) and larger spleen sizes (p=0.010) than adult patients, whereas the white blood cell count and phase at diagnosis did not differ. We found 606 genes (210 up- and 396 down-regulated) differentially expressed in pediatric CML CD34+ cells compared to pediatric normal controls. Interestingly, transcriptional regulators involved in blood cell differentiation including GATA1, TAL1, and KLF1 were differentially enriched in pediatric CML. In comparing adult CML patients to normal adult CD34+ cells, we found 920 genes (379 up- and 541 down-regulated) differentially expressed. Among all dysregulated genes we identified (1352 genes), 174 genes (54 up- and 120-down-regulated) overlapped when comparing pediatric and adult CML patients. Significantly enriched pathways in both adult and pediatric CML cells included PI3K/AKT signaling, MAPK signaling, and Notch/Wnt signaling, which have been previously reported. We found 437 unique genes that were dysregulated only in pediatric CML (270 up- and 167 down-regulated). Notch/Wnt signaling and Rho signaling pathways were significantly enriched. DLC1, a tumor suppressor gene that encodes a RhoGTPase-activating protein, has been known to be downregulated in solid tumors and hematologic malignancies. Interestingly, our data showed that DLC1 is significantly upregulated by 3-fold (p=0.0238) in pediatric CML, but not adult CML CD34+ cells. In addition, we observed that ABR, an inducer of C/EBPa that encodes an activator of RhoGEF and GTPase, was significantly downregulated by 2-fold (p=0.0119) in pediatric but not in adult CML CD34+ cells. Conclusion These results demonstrate unique molecular characteristics of pediatric CML that may contribute to the clinical differences at presentation between adult and pediatric disease. A better understanding of the particular biology of pediatric CML might impact the treatment of those patients in the future. Disclosures Gotlib: Deciphera: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: co-chair of the Study Steering Committee and Research Funding; Blueprint Medicines Corporation: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Chair of the Response Adjudication Committee and Research Funding, Research Funding.

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A Calreticulin Neoepitope-Directed Monoclonal Antibody Can Overcome JAK Inhibitor Resistance and Block TPO-Independent Megakaryocyte Differentation

Blood ◽

10.1182/blood-2021-154332 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 3597-3597

Author(s):

Denis Tvorogov ◽

Chloe AL Thompson-Peach ◽

Johannes Foßelteder ◽

Mara Dottore ◽

Frank Stomski ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Research Funding ◽

Liquid Culture ◽

Jak Inhibitor ◽

Advisory Committees ◽

Nsg Mice ◽

Cd34 Cells ◽

Calr Mutations ◽

Bone Marrow Engraftment

Abstract Introduction: Mutations within the gene encoding calreticulin (CALR) are the second most common genetic aberration associated with primary myelofibrosis (PMF), observed in 70% of non-JAK2 V617F cases. Importantly, patients with CALR mutations do not effectively respond to JAK inhibitor therapy and no mutation specific therapy is currently in use. Virtually all CALR mutations identified in PMF are small insertions or deletions clustered within exon 9 leading to a neo-epitope peptide sequence which is thought to directly or indirectly activate the thrombopoietin receptor (TpoR) by a poorly defined mechanism. Here we engineered a neo-epitope specific monoclonal antobody that has striking biological activity against ruxolitinib persistent cells. Methods TF-1 TpoR cells expressing TpoR were supplemented with 20 ng/mL of TPO. Rats were immunised with a CALR mutant peptide coupled to KLH. Serum from the immunised rats was screened by enzyme linked immunoassay, to verify a strong titre to the peptide immunogen. Primary PMF CD34+ cells were cultured in StemCell Pro with human SCF, IL-6 and IL-9. NSG mice were used to for engraftment studies after 150 cGy irradiation. Results: We engineered a panel of rat monoclonal antibodies after immunization with a 30 amino acid peptide corresponding to the C-terminal mutant CALR neoepitope sequence with an extra cysteine residue. Clone 4D7 showed superior activity of detecting mutant but not wild type CALR protein with a binding affinity of 13.5 pM and dissociation constant of 1.53 nM as measured by I 125-Scatchard. Treatment with 4D7 resulted in a significant (5-7-fold) increase in the amount of full-length mutant CALR protein in conditioned media. 4D7 inhibited Tpo-independent cell growth over 6 days in TF-1 cells expressing MPL and mutant CALR at 2, 10 and 20 µg. 4D7 blocked constitutive factor-independent phospho-STAT5 and phospho-ERK after incubation exclusively in mutant CALR cells but not in TF-1 cells expressing TpoR alone and increased the sub-G 0 fraction was observed compared to IgG control (P = 0.001, n = 3 independent experiments) consistent with induction of an apoptotic response. We tested activity in purified primary CD34+ cells obtained from patients with CALR mutant myelofibrosis using two orthogonal assays: - (i) Tpo-independent megakaryocyte differentiation in liquid culture and (ii) Tpo-independent megakaryocyte colony formation on a collagen-based medium. 4 out of 4 patient samples that displayed robust Tpo-independent growth of CD41+CD61+ megakaryocyte progenitors showed inhibition by 4D7 of at least 50%. Similarly, we saw dramatic reduction in the absolute numbers of primary Tpo-independent megakaryocyte colonies cultured on collagen (colony-forming unit-mega) treated with 4D7 in multiple patient samples (decrease of 46%, P = 0.0001, Student's t-test, n = 4 independent patient samples) Importantly, secretion of mutant CALR protein was neither upregulated nor downregulated by ruxolitinib, indicating ruxolitinib is unlikely to alter mutant CALR trafficking in patients. 4D7 had strong inhibitory activity on cells that were resistant to ruxolitinib, in both liquid culture at 96 hours or colony formation. To test whether 4D7 could block mutant CALR-dependent proliferation in vivo, we developed two distinct xenograft models, a bone marrow engraftment model, which measures mutant CALR dependent proliferation in the bone marrow microenvironment, and a chloroma model, which mimics extravascular infiltration of mutant CALR leukaemia, by injection of TPO-independent TF-1 cells in NSG mice. In the bone marrow engraftment model 4D7 treatment (12 mg/kg twice weekly via intraperitoneal injection) lowered peripheral blood engraftment of human CD33 myeloid cells at 3 weeks, bone marrow engraftment and significantly prolonged survival compared to IgG control (P=0.004, HR=0.2). In the chloroma model, 4D7 treatment resulted in significant decrease in tumour growth measured at 3 weeks (P<0.01) and improved overall survival (P=0.02, HR=0.07) compared to IgG control Conclusion: Together, these results suggest an immunotherapeutic approach may have clinical utility CALR-driven myeloproliferative neoplasms and CALR mutant acute myeloid leukaemia, as well as activity in CALR mutant patients that develop resistance/persistence to ruxolitinib. Disclosures Ross: Bristol Myers Squib: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Keros Therapeutics: Consultancy, Honoraria. Reinisch: Celgene: Research Funding; Pfizer: Consultancy.

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Transcriptome Profiling of Pediatric Myeloproliferative Neoplasms Demonstrates Dysregulation of Platelet-Relevant Genes and Enrichment of Inflammatory and JAK2 Mediated Complement Pathways

Blood ◽

10.1182/blood-2019-125103 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 4203-4203

Author(s):

Nicole Kucine ◽

Amanda R. Leonti ◽

Aishwarya Krishnan ◽

Rhonda E. Ries ◽

Ross L. Levine ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Platelet Activation ◽

Research Funding ◽

Mononuclear Cells ◽

Myeloproliferative Neoplasms ◽

Differentially Expressed ◽

Rna Seq ◽

Advisory Committees ◽

Normal Controls

Introduction : Myeloproliferative neoplasms (MPNs) are rare clonal bone marrow disorders in children characterized by high blood counts, predisposition to clotting events, and the potential to transform to myelofibrosis or acute myeloid leukemia (AML). Children with MPNs have lower rates of the known driver mutations (in JAK2, MPL, and CALR) than adult patients, and the underlying pathways and molecular derangements in young patients remain unknown. Given the lack of knowledge about pediatric MPNs, it is critical that we gain a better understanding of the dysregulated pathways in these diseases, which is necessary for improving disease understanding and broadening treatment options in children. Therefore, the objective of this work was to identify differentially expressed genes and pathways between children with MPNs and healthy controls, as well as children with AML, to guide further study. Methods : Mononuclear cells were extracted from peripheral blood of pediatric MPN patients (n=20) and pediatric and young adult AML patients (n=1410), and bone marrow of normal controls (NC, n=68). AML patient samples were being evaluated as part of a Children's Oncology Group planned analysis. To identify an expression profile unique to MPNs, transcriptome data from MPN patients was contrasted against NC and AML patients. All samples were ribodepleted and underwent Illumina RNA-Seq to generate transcriptome expression data. All analyses were performed in R. Differentially expressed genes were identified using the voom function from the limma package (v. 3.38.3), and enriched pathways were identified using the pathfindR package (v. 1.3.1). Unsupervised hierarchical clustering and heatmap generation was performed using the ComplexHeatmap package (v. 1.20.0). Results : MPN patient samples showed a unique expression signature, distinct from both AML patients and normal controls. Unsupervised PCA plot (Figure 1A) and heatmaps (Figure 1B) show that MPN samples cluster together. There were 4,012 differentially expressed (DE) genes in MPNs compared to NC and 6,743 DE genes in MPNs compared to AML patients. There were 2,493 shared genes between the 2 groups (Figure 1C.) Significantly DE genes between MPNs and other groups included multiple platelet-relevant genes including PF4 (CXCL4), PF4V1, P2RY12, and PPBP (CXCL7). Interestingly, PF4V1 was the most DE gene in MPNs compared to AML, and third highest versus NC. Dysregulation of some of these genes has been seen in adult MPNs, as well as thrombosis. Further comparison of transcriptome profiles between children with (n=13) and without (n=7)JAK2 mutations showed upregulation of three genes, CFB, C2, and SERPING1, which are all known complement genes, implicating complement activation in JAK2-mutated MPN patients. Complement activation has previously been reported in adult MPNs. Pathway enrichment analysis shows a number of immune and inflammatory pathways as enriched in MPN patients compared to both AML and NC. There were 179 enriched pathways in MPNs compared to AML and 142 compared to NC, with 134 common pathways (Figure 1D.) The systemic lupus erythematosus pathway was the most heavily enriched pathway in MPNs compared to both AML and NC. Additional pathways with significant enrichment include hematopoietic cell lineage, cytokine-cytokine interactions, DNA replication, and various infection-relevant pathways. The JAK-STAT signaling pathway was also enriched in MPNs compared to both AML and NC, as was the platelet activation pathway. Conclusion: Transcriptome evaluation of childhood MPNs shows enrichment of numerous inflammatory and immune pathways, highlighting that, as in adult MPNs, inflammation is implicated in pediatric MPNs. Furthermore, specific complement genes were upregulated in JAK2-mutant MPN. Upregulation of platelet-specific genes implies potential insights into disease mechanisms and warrants more study. Variations in the cell populations may account for some of the differences seen, however all samples were largely mononuclear cells, making their comparisons reasonable. Further analysis of this early data is needed to better assess inflammatory changes and platelet activation in pediatric MPNs, as are larger sample sizes. Individual cells may have differential expression of various genes, and future experiments with single-cell RNA-seq would be helpful to further elucidate differences. Disclosures Levine: Novartis: Consultancy; Loxo: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Research Funding; Gilead: Consultancy; Roche: Consultancy, Research Funding; Lilly: Honoraria; Amgen: Honoraria; Qiagen: Membership on an entity's Board of Directors or advisory committees; Imago Biosciences: Membership on an entity's Board of Directors or advisory committees; C4 Therapeutics: Membership on an entity's Board of Directors or advisory committees; Prelude Therapeutics: Research Funding; Isoplexis: Membership on an entity's Board of Directors or advisory committees.

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Treatment of Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN) in Pediatric Patients with Tagraxofusp, a CD123-Targeted Therapy

Blood ◽

10.1182/blood-2021-150393 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2317-2317

Author(s):

Naveen Pemmaraju ◽

Branko Cuglievan ◽

Joseph L Lasky ◽

Albert Kheradpour ◽

Nobuko Hijiya ◽

...

Keyword(s):

Bone Marrow ◽

Adverse Events ◽

Board Of Directors ◽

Research Funding ◽

Pediatric Patients ◽

Plasmacytoid Dendritic Cell ◽

Case Series ◽

Complete Response ◽

Retrospective Case ◽

Advisory Committees

Abstract BACKGROUND Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and clinically aggressive hematological malignancy that overexpresses CD123, the interleukin-3 (IL3) receptor alpha subunit. Although BPDCN predominantly affects older adults (median age of 65 years at diagnosis), cases of BPDCN have been reported across all age groups, including infants and children. There is limited data available in the literature on the efficacy and safety of treatments for pediatric patients with BPDCN. Tagraxofusp (TAG, SL-401) is a CD123-directed targeted therapy consisting of recombinant human IL3 linked to a truncated diphtheria toxin payload. A published multicohort prospective study, with prespecified multisystem endpoints, demonstrated the benefit of TAG in adult patients with untreated or relapsed BPDCN. Among the untreated patients, 72% had a complete response and 90% overall response rate; of these patients, 45% were bridged to stem cell transplantation. Adverse events included transaminase elevations, hypoalbuminemia, thrombocytopenia, and capillary leak syndrome (CLS). In a previous case report including 3 pediatric patients with BPDCN, TAG was well-tolerated without significant toxicities and showed encouraging initial clinical responses. TAG was FDA approved in 2018 for BPDCN treatment in adult and pediatric (≥2 years) patients and was recently approved in the EU as monotherapy for first-line treatment in adults. METHODS Here, we report on a multicenter, retrospective case series investigation involving pediatric patients diagnosed with BPDCN at 3 centers in the United States. All patients were treated with TAG according to local institutional guidelines as either first-line treatment (1L) or as a therapy for relapsed/refractory disease (R/R). Data was collected retrospectively via chart review and summarized descriptively. Assessments included tumor response to therapy, survival and safety (adverse events and laboratory abnormalities). RESULTS A total of 6 pediatric patients diagnosed with BPDCN and treated with TAG were included in this analysis. The median age for patients in this study was 15.5 years (range 10 - 21 years), and 4 of the 6 patients were female. Three patients were R/R and received systemic therapy prior to TAG administration, while 3 patients were treatment-naive. Four patients had bone marrow involvement, 2 patients had lymph node involvement, and all 6 patients had skin lesions at diagnosis. All patients received a TAG dose of 12 mcg/kg, with the exception of 1 patient who received 9 mcg/kg. At the time of data cut off, the number of cycles administered ranged from 1 to 4. TAG was well tolerated in these 6 patients. One patient experienced headaches, hot flashes, fatigue, and mouth sores, and low albumin was observed in one patient. No other adverse events were reported and CLS was not observed in these patients. One patient had a complete response to TAG therapy (bone marrow minimal residual disease negative), 2 patients had stable disease, and 3 patients did not have an observed response. In the three 1L patients, one patient had stable disease (no progression after 4 TAG cycles), and 1 patient with extensive disease (skin, bone marrow and central nervous system) had a complete response. Three patients bridged to a stem cell transplant (SCT); 2 were R/R and 1 was 1L. Median survival data for this cohort will be presented (5 of 6 patients remain alive). CONCLUSIONS This multicenter, retrospective case series of 6 pediatric patients with BPDCN expands our base of knowledge of BPDCN treatment in younger individuals. At the time of data cut off for this abstract, TAG, an approved treatment for BPDCN, was well tolerated in all patients. Treatment with TAG was associated with promising efficacy, including half of the patients with responses that allowed for bridging to SCT. Disclosures Pemmaraju: CareDx, Inc.: Consultancy; Plexxicon: Other, Research Funding; Samus: Other, Research Funding; ASH Communications Committee: Membership on an entity's Board of Directors or advisory committees; Aptitude Health: Consultancy; Springer Science + Business Media: Other; HemOnc Times/Oncology Times: Membership on an entity's Board of Directors or advisory committees; Blueprint Medicines: Consultancy; Bristol-Myers Squibb Co.: Consultancy; Dan's House of Hope: Membership on an entity's Board of Directors or advisory committees; ASCO Leukemia Advisory Panel: Membership on an entity's Board of Directors or advisory committees; Sager Strong Foundation: Other; Cellectis S.A. ADR: Other, Research Funding; Daiichi Sankyo, Inc.: Other, Research Funding; DAVA Oncology: Consultancy; Roche Diagnostics: Consultancy; MustangBio: Consultancy, Other; Abbvie Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; Celgene Corporation: Consultancy; Stemline Therapeutics, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding; LFB Biotechnologies: Consultancy; Clearview Healthcare Partners: Consultancy; Protagonist Therapeutics, Inc.: Consultancy; Affymetrix: Consultancy, Research Funding; Incyte: Consultancy; Novartis Pharmaceuticals: Consultancy, Other: Research Support, Research Funding; ImmunoGen, Inc: Consultancy; Pacylex Pharmaceuticals: Consultancy. Hijiya: Novartis: Consultancy; Stemline Therapeutics: Consultancy. Stein: Amgen: Consultancy, Speakers Bureau; Celgene: Speakers Bureau; Stemline: Speakers Bureau.

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Decreased Expression of CD62L and CD54 Correlates with Poor Cytogenetic Risk Group In Myelodysplastic Syndromes

Blood ◽

10.1182/blood.v116.21.2915.2915 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2915-2915

Author(s):

Canan Alhan ◽

Theresia M. Westers ◽

Claudia Cali ◽

Floortje L. Kessler ◽

Monique Terwijn ◽

...

Keyword(s):

Bone Marrow ◽

Flow Cytometry ◽

Healthy Volunteers ◽

Board Of Directors ◽

Myelodysplastic Syndromes ◽

Research Funding ◽

Risk Category ◽

Advisory Committees ◽

Cd34 Cells

Abstract Abstract 2915 Interactions in the bone marrow (BM) between haematopoietic progenitor cells (HPC) and the BM micro environment are important for the regulation of cell adhesion, proliferation, differentiation and survival. Expression of both CD62L (L-selectin) and CD54 (ICAM-1) on HPC demonstrated to play a role in signal transduction routes for proliferation and growth regulation. Especially CD54 is involved in uncontrolled proliferation and block of apoptosis. Previously, it was described that decreased expression of CD62L in acute myeloid leukemia (AML) was associated with a poor cytogenetic risk profile and an adverse clinical outcome (Graf M et al, Eur J Haematol 2003) Myelodysplastic syndromes are a group of clonal HPC disorders characterized by ineffective hematopoiesis and a propensity to evolve into AML. The International Prognostic Scoring System (IPSS) provides information on both survival and risk of development of an AML. The purpose of our study was to evaluate CD62L and CD54 expression on CD34+ cells in MDS patients by flow cytometry and to assess the value of a CD62L/CD54 ratio for prognostication. Bone marrow samples of 30 newly diagnosed MDS patients (3 RA(RS)/18 RCMD(RS), the <5% blasts group; 5 RAEB-1, 4 RAEB-2, the >5% blasts group), 16 AML patients with prior MDS and 26 healthy volunteers were analyzed for CD62L and CD54 expression on CD34+ cells by using flow cytometry. An adhesion index was calculated as a ratio of the percentage and MFI of CD62L and CD54 positive cells (as was reported by Buccisano et al, Eur J Haematol 2007). The CD62L/CD54 ratio was significantly decreased in MDS with <5% blasts (median 79.09 p<0.0001) as compared to healthy volunteers (median 480.4) and even more decreased in high risk MDS (median 14.67 p<0.0001 and p=0.001 as compared to healthy volunteers and MDS with <5% blasts, respectively) and AML with prior MDS (median 12.54, p<0.0001 and p=0.009 as compared to healthy volunteers and MDS with <5% blasts, respectively). The MDS patients were assigned to the good, intermediate or poor IPSS cytogenetic risk category. Cytogenetics was available for 22 MDS patients. The CD62L/CD54 ratio was significantly lower in the cytogenetic poor risk category compared with the good risk category (median 5.4 and median 70.79 respectively, p=0.018). Moreover, a low CD62L/CD54 ratio correlated significantly with poor cytogenetics, p=0.006. In the group of MDS patients with <5% blasts, 4 developed a refractory anemia with excess of blasts or AML within a follow up period of 12 months. There was a trend for a lower CD62L/CD54 ratio for MDS patients who developed an AML compared with patients who did not. In conclusion, the CD62L/CD54 ratio is significantly decreased in MDS compared with healthy volunteers and even more decreased in AML with prior MDS. Both CD62L and CD54 are involved in regulation of proliferation and apoptosis of the HPC. A decreased adhesion ratio in low risk MDS patients might reflect HPC damage at an early stage of the disease with an increased proliferative capacity and a decreased apoptotic profile. Interestingly, a low CD62L/CD54 ratio showed a significant inverse correlation with the IPSS cytogenetic risk category. Due to an absence of metaphases in a proportion of MDS patients, cytogenetics is not always available. The CD62L/CD54 ratio might serve as a surrogate marker for poor prognosis cytogenetics in case no karyotype is available. Low risk MDS patients who developed an AML within 12 months tended to have a lower CD62L/CD54 ratio. Although these results are promising, sample size and follow up period needs to be extended. The CD62L/CD54 ratio might add to prognostication of MDS patients and might identify MDS patients with <5% blasts who are at risk for development of an AML. Disclosures: Ossenkoppele: Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding. Van de Loosdrecht:Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding.

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Bone Marrow Mesenchymal Stem Cell (BM-MSC) Release Microvesicles/Exosomes That Incorporate Into Hematopoietic Cells From MDS Patients and May Modify Their Behaviour

Blood ◽

10.1182/blood.v122.21.863.863 ◽

2013 ◽

Vol 122 (21) ◽

pp. 863-863 ◽

Cited By ~ 1

Author(s):

Sandra Muntión ◽

Post Doc Fellowship ◽

Teresa Ramos ◽

Bruno Paiva ◽

Beatriz Roson ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Research Funding ◽

De Novo ◽

Annexin V ◽

Micro Rna ◽

Bioactive Molecules ◽

Advisory Committees ◽

Micro Rnas ◽

Cd34 Cells

Abstract A new mechanism of intercellular communication has been proposed consisting in the secretion of exosomes/ microvesicles (MVs). Such mechanism has been shown to modify the functional properties of recipient cells by the transfer of proteins, mRNA, or micro-RNAs. The hypothesis of the present work was that MSC from MDS patients could differentially modify the HPC properties throughout the shedding of MVs when compared with those from controls due to their different content. Material and methods: MVs were isolated from MSC from bone marrow (BM) samples 18 patients diagnosed with ‘de novo’ and untreated low risk MDS and from MSC from 12 healthy BM. BM-MSC at third passage were cultured in DMEM deprived of FCS, and supernatants were collected after 6 or 24 hours. MVs purification was performed in the majority of the experiments (16 MDS/ 9 Controls) using the ExoQuick-TC exosome precipitation solution (ExoQuick; System Biosiences). To confirm the isolation of MVs by exosome precipitation solution, in some cases (2 MDS/3 Controls) the MVs were obtained by ultracentrifugation; MVs identification was done by transmission electron microscopy (TEM) as well as by flow cytometry (FC). To evaluate if the micro-RNA content into MSC-MVs from patients and controls was different, expression analysis of miRNAs was done using Megaplex™ RT Primers pool (Applied Biosystems) and 384-well microfluidic cards (TaqMan® MicroRNA Array A) were loaded with retro-transcription product and PCR runs were performed on a 7900HT Fast Real-time PCR system (eight MVs from MDS and 4 from HD).To demonstrate the incorporation of MVs from MSC into human hematopoietic progenitors (HPC: CD34+ cells obtained by immunomagnetic selection) HPC were co-cultured with MVs from MSC. Incorporation of Vybrant Dil-labelled MVs into HPC was evaluated at 1, 3, 6, and 24 h. by FC. To detect the incorporation of MVs by confocal microscopy (CM) an intracellular primary Ab for CD90 (Santa Cruz, Biotechnology) was used as MVs marker and anti-CD45 to detect HPC. A Zeiss LSM 510 CM connected to a digital camera (Leica DC 100) were used to obtain confocal images. Apoptotic rate of CD34+ cells that had the MVs-MSC from MDS and controls were evaluated by FC by using APC H7 Annexin V DY634 (Immunostep) and 7AAD (BD Biosciences). Results: More than 95% of MVs isolated by ExoKit system from supernatants of cultured MSC from 6 HD and 6 MDS patients showed scatter intensities lower than of 6µm beads. We observed, in all cases, the same FC pattern. Also, MVs/exosomes isolated by ultracentrifugation (3 MDS/ 5 HD) showed the same FC pattern. MVs from MDS and controls isolated by ultracentrifugation were identified by TEM (fig1). When co-cultures of CD34+ HPC and MVs were studied in both HD and MDS, MVs were incorporated into HPC in all cases (fig2). When the content of miRNAS in the MVs from MDS and HD were compared significant differences were observed between both groups. Twenty-one out of 384 evaluated miRNAs were over-expressed in the MVs from patients compared with the controls. To confirm these results, the expression of miR10a and miR-132 was analyzed by RT-PCR. In both cases their expression was significantly increased in MVs from patients. Recently, it has been suggested that the cargo of these structures are bioactive molecules, therefore we explored the possibility that MVs could modify the behavior of the target cell. For this purpose we searched in which pathways the overexpressed miRNAs could be involved and apoptosis was among them. Since it is considered a very important process in MDS pathophysiology we compared apoptosis by FC, after co-culturing CD34+ cells with MVs from MSC of MDS and HD. Interestingly, preliminary results show that the MVs from MDS protected better from apoptosis CD34+ cells than MVs obtained from controls. In summary, in the present study we show that BM-MSC produce MVs/exosomes with different microRNAs content according to their origin, MDS or HD. These structures can be incorporated into HPC and can modify their properties. Funding: Instituto de Salud Carlos III. PI12/01775. Junta de Castilla y León.GRS 873/A/13. Portuguese FST Grant. SFRH/BD/86451/2012 Disclosures: Diez-Campelo: Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. San Miguel:Jansen, Celgene, Onyx, Novartis, Millenium: Membership on an entity’s Board of Directors or advisory committees. del Cañizo:Celgene: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Jansen-Cilag: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Arry: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity’s Board of Directors or advisory committees, Research Funding.

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Extracellular Vesicles Play an Important Role in Intercellular Communication Between Bone Marrow Stroma and Hematopoietic Progenitor Cells in Myeloproliferative Neoplasms

Blood ◽

10.1182/blood.v128.22.1957.1957 ◽

2016 ◽

Vol 128 (22) ◽

pp. 1957-1957

Author(s):

Teresa L. Ramos ◽

Luis Ignacio Sánchez-Abarca ◽

Beatriz Rosón ◽

Alba Redondo ◽

Concepción Rodríguez ◽

...

Keyword(s):

Bone Marrow ◽

Progenitor Cells ◽

Board Of Directors ◽

Intercellular Communication ◽

Research Funding ◽

Hematopoietic Progenitor Cells ◽

Rt Pcr ◽

Hematopoietic Progenitor ◽

Advisory Committees ◽

Cd34 Cells

Abstract The complex interplay between bone marrow-derived mesenchymal stromal cells (BM-MSC) and neoplastic hematopoietic cells is involved in the progression of myeloproliferative neoplastic (MPN) diseases. Extracellular vesicles (EV) have emerged as a complex cell-to-cell communication system within the neoplastic microenvironment. EV are able to reprogram recipient cells by transferring proteins, mRNA and microRNA from their cell of origin. We aimed to analyze the microRNA content of EV obtained from MPN BM-MSC, as well as the changes induced when these EV are incorporated into hematopoietic progenitor cells (HPC). EV were isolated from BM-MSC of MPN patients (n=22) and healthy donors (HD) (n=19) by ultracentrifugation. Characterization of EV by transmission electron microscopy (TEM), immunoblot, multiparametric flow cytometry (MFC) and NanoSight analysis revealed vesicles with a typical bilayer-membrane characteristic morphology with a size inferior to 500 nm, which were positive for various EV markers as CD63 and CD81, and for MSC markers as CD73, CD90 and CD44 (Figure 1). MicroRNA profiling by 384-well microfluidic cards (TaqMan® MicroRNA Array A) showed an overall increase in the microRNA expression in the MPN-MSC-derived EV, when compared to EV from donor MSC. Using RT-PCR, we observed that miR-155 was selectively enriched in EV released by MPN-MSC. An overexpression of this microRNA was observed in EV (p=0.032), while a downregulation was observed in BM-MSC (p=0.0078) (Figure 2). EV incorporation was demonstrated by fluorescence microscopy and MFC, where HPC (CD34+ cells obtained by immunomagnetic selection) were co-cultured with Vybrant Dil-labeled EV. For functional studies apoptosis and clonogenic assays (CFU-GM) were performed. We observed an increase in CD34+ cell viability after incorporating EV from BM-MSC (HD and MPN). Moreover, an increase (p=0.04) in miR-155 expression was observed when HD HPC incorporated EV from MPN-MSC. When neoplastic CD34+ cells incorporated the EV derived from MPN-MSC an increase of CFU-GM number was also observed. We suggest that EV released from MPN-MSC represent a mechanism of intercellular communication between malignant stromal and hematopoietic cells, through the transfer of genetic information that may be relevant in the pathophysiology of these diseases. Funding: GRS 1034/A/14 (C. Sanidad, JCYL) and FCT (SFRH/BD/86451/2012) Figure 1 EV characterization by TEM (A), Immunobloting - CD63 (B) and MFC (C). Scale bar: 200 and 500 nm. Figure 1. EV characterization by TEM (A), Immunobloting - CD63 (B) and MFC (C). Scale bar: 200 and 500 nm. Figure 2 Expression of miR-155. RT-PCR from EV released from HD and MPN-MSC (A), and the expression of miR-155 in BM-MSC (B). Figure 2. Expression of miR-155. RT-PCR from EV released from HD and MPN-MSC (A), and the expression of miR-155 in BM-MSC (B). Disclosures Sánchez-Guijo: Bristol-Myers-Squib: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Incyte: Consultancy, Honoraria. Del Cañizo:Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Jansen-Cilag: Membership on an entity's Board of Directors or advisory committees, Research Funding; Arry: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding.

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Tracking of AML-Associated Mutations Via Droplet Digital PCR Is Predictive of Outcomes Post-Transplant

Blood ◽

10.1182/blood-2018-99-110834 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 2138-2138 ◽

Cited By ~ 1

Author(s):

Amanda Winters ◽

Madeline Goosman ◽

Brett M Stevens ◽

Enkhtsetseg Purev ◽

Clayton Smith ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Research Funding ◽

Digital Pcr ◽

Cytotoxic Chemotherapy ◽

Droplet Digital Pcr ◽

Published Data ◽

Advisory Committees ◽

P Values ◽

Donor Chimerism

Abstract Introduction: Allogeneic hematopoietic stem cell transplantation (HSCT) remains one of the only curative therapies for acute myeloid leukemia (AML) in adult patients. However, a high proportion of patients will relapse post-HSCT. Measurable residual disease (MRD) has emerged as highly predictive of relapse after chemotherapy and multiple studies have demonstrated inferior outcomes after HSCT for patients with pre-HSCT MRD. Fewer studies have evaluated post-HSCT MRD, but those have suggested that MRD is a powerful predictive tool in this setting as well. We have previously utilized droplet digital PCR (ddPCR) as an MRD platform to track 33 unique AML-associated mutations in a cohort of patients receiving either cytotoxic chemotherapy or targeted agents, and our preliminary data suggest that persistence or recurrence of these mutations during therapy is predictive of relapse and diminished overall survival. In the present study we sought to evaluate the utility of ddPCR specifically for post-HSCT MRD monitoring. Methods: Patients 18 years of age or older with AML who had received allogeneic HSCT were identified via retrospective chart review. Thirty-seven patients were identified who had sufficient diagnostic testing to identify AML-associated point mutations and had available DNA from serial bone marrow samples. Thirty-six of these patients had at least one pre-HSCT sample analyzed; post-HSCT day 28, day 80, and day 365 samples were available for 26, 25, and 11 patients, respectively. DdPCR was utilized to track 21 different AML-associated mutations in this patient cohort. MRD negativity was defined as variant allelic frequency (VAF) below the limit of detection for all assayed mutations (1-4 mutations per patient). Relapse-free (RFS) and overall (OS) survival were defined as time from date of transplant to relapse or death. Survival statistics were analyzed as Kaplan-Meyer curves, with p-values determined by the log-rank (Mantel-Cox) test. P-values less than 0.05 were considered statistically significant. Outcome data for all patients were censored July 6, 2018. Results: Median follow-up from time of HSCT was 13.3 months. Of the 37 patients included in this cohort, the majority (73%) received regimens containing cytotoxic chemotherapy prior to HSCT; the remainder (27%) received targeted therapies +/- low-intensity chemotherapy prior to HSCT. Only 6 of 36 patients (17%) were MRD negative pre-HSCT, all of whom had received cytotoxic chemotherapy. All 37 patients had one or more post-HSCT samples available for MRD assessment. Of these, 30 achieved MRD negativity after HSCT (81%). Post-HSCT MRD status was predictive of both RFS and OS (Figure 1). This replicates previously published data with respect to ddPCR-based MRD, but is based on evaluation of both more patients and more mutations. In agreement with previously published data showing high predictive value of the 1-month post-HSCT MRD, we found this timepoint specifically to be predictive of RFS and OS in the 26 patients for whom a sample was assayable (Figure 2). Neither outcomes nor MRD status by ddPCR varied based on conditioning regimen (myeloablative versus reduced-intensity) in our cohort (data not shown). We also compared ddPCR MRD status with whole bone marrow chimerism measured by short tandem repeat (STR) analysis. Concordance between MRD negativity and >95% donor chimerism was 69% at 1 month post-HSCT and 93% at 80 days post-HSCT. Of 8 discordant samples at the 1 month post-HSCT time point, 3 had donor chimerism <95% but were MRD negative, with no relapses to date. The other five patients had full donor chimerism with positive MRD, and 3 of 5 patients have relapsed. Of two discordant samples at 80 days post-HSCT, both involved full donor chimerism with persistence of MRD, and one patient has subsequently relapsed. Conclusions: ddPCR-based molecular MRD assessment is predictive of relapse-free and overall survival post-HSCT in patients with AML, and may be a powerful adjunct to surveillance measures already in clinical use, such as chimerism. Presence of molecular MRD specifically at 1 month post-transplant showed significant correlation with relapse and with overall mortality. Detection of AML-associated mutations at this and later time points in a prospective manner could in many cases allow salvage of patients prior to clinical relapse, thus improving survival for this high-risk population. Disclosures Pollyea: Gilead: Consultancy; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Curis: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Research Funding; Celyad: Consultancy, Membership on an entity's Board of Directors or advisory committees; Argenx: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding.

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Phase 2 Study of Monotherapy Galunisertib (LY2157299 Monohydrate) in Very Low-, Low-, and Intermediate-Risk Patients with Myelodysplastic Syndromes

Blood ◽

10.1182/blood.v126.23.1669.1669 ◽

2015 ◽

Vol 126 (23) ◽

pp. 1669-1669 ◽

Cited By ~ 13

Author(s):

David Valcarcel ◽

Amit Verma ◽

Uwe Platzbecker ◽

Valeria Santini ◽

Aristoteles Giagounidis ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Research Funding ◽

Intermediate Risk ◽

Phase 2 ◽

Eligibility Criteria ◽

Advisory Committees ◽

Cd34 Cells ◽

Risk Patients ◽

Ecog Ps

Abstract Introduction: Myelodysplastic syndromes (MDS) are characterized by bone marrow dysplasia and ineffective hematopoiesis. Zhou et al. showed that transforming growth factor-beta (TGF-β) signaling was constitutively activated in MDS CD34+ cells and that this over-activation and subsequent myelosuppression was based on reduced expression of SMAD7, the natural inhibitor of TGF-β, in MDS CD34+ cells (Zhou L et al. Cancer Res 2011;71:955-963). Galunisertib specifically inhibited the kinase activity of the TGF-β receptor type I (TGF-βRI) also known as ALK5 and its downstream signaling pathway theoretically replaced the SMAD7 function. Galunisertib reversed hematopoietic suppression in human MDS bone marrow assays, and in a murine model of TGF-β derived bone marrow failure. Based on these preclinical studies that demonstrate hematological improvement (HI) in MDS models following galunisertib treatment, a single-arm phase 2 part of a phase 2/3 proof-of-concept study in very low-, low-, and intermediate-risk patients with MDS was conducted. Methods: The primary objective of this study was to estimate the HI rate based on International Working Group (IWG) 2006 criteria in patients with very low-, low-, and intermediate-risk MDS by Revised International Prognostic Scoring System (IPSS-R), treated with galunisertib. Eligible patients were treated with galunisertib 300 mg/day (150 mg BID) orally for 14 days, followed by 14 days off, constituting a cycle of 28 days. Eligibility criteria permitted any prior therapy, all of which were required to be discontinued at least 28 days prior to initiation of galunisertib. Supportive therapies including ongoing transfusions were allowed. Eligibility criteria included confirmed diagnosis of MDS, anemia with hemoglobin ≤10.0 g/dL, and an Eastern Cooperative Oncology Group performance status (ECOG PS) ≤2. Safety was assessed and summarized using the Common Terminology Criteria for Adverse Events (CTCAE v4.0). Descriptive statistics were used to report baseline characteristics and response rates. Results: In this phase 2 study, 41 patients received galunisertib orally (N=39, 150 mg BID and N=2, 80 mg BID for PK comparison). Patients were 62% males. The median age was 71 years (range: 52-84), the majority of patients were classified as refractory cytopenia with multilineage dysplasia (66.7%) or refractory anemia with ringed sideroblasts (20.5%) based on WHO MDS classification. ECOG PS was 0/1 in 53.8%/46.2% of patients. Sixty-two percent of the patients received ≥6 cycles of treatment. Among the 39 patients receiving 150 mg BID, a total of 15 (38%) patients discontinued from the study within 6 cycles; one due to AE and 9 due to patient/physician decision. The most common possibly related any grade treatment-emergent adverse events (TEAEs) included fatigue (20.5%), diarrhea (15.4%), pyrexia (10.3%), vomiting (10.3%), anemia (7.7%), nausea (7.7%), urinary tract infection (7.7%), neutrophil count decreased (5.1%), and platelet count decreased (5.1%); 12 (30.8%) patients had grade 3/4 TEAEs, 4 (10.3%) were drug-related. One of the 39 patients was protocol ineligible and was removed from the efficacy analysis. Among the 38 evaluable patients in the ITT population, 14 of whom required fewer than 4 units of transfusion per 8 weeks, 10/38 (26%) patients achieved HI, defined as at least a continuous 8-week response with at least a 4-unit reduction in transfusion requirement from baseline or hemoglobin increase by at least 1.5 g/dL per 8-week period. Of these 10 patients, 4 became transfusion-independent, and 5 had transfusion reduction. In a subgroup of 24/38 patients who had a transfusion requirement of at least 4 units every 8 weeks at baseline, 9 (38%) of these patients achieved a transfusion reduction of at least 4 units. No apparent correlation between cytogenetics or MDS subtype including ringed sideroblasts and response was identified; however, only 14 patients had abnormal cytogenetics. No platelet or neutrophil responses were observed. Conclusion: Galunisertib is well tolerated in this MDS population where this ALK5 inhibitor was investigated for the first time. Patients most commonly discontinued from study treatment due to patient/physician decision and not for toxicity. The clinical endpoint of HI was observed in 26% of the ITT population, and no specific response sub-group was identified. Disclosures Valcarcel: GSK: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; NOVARTIS: Honoraria, Membership on an entity's Board of Directors or advisory committees; AMGEN: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; CELGENE: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Platzbecker:Boehringer: Research Funding; Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Santini:celgene, Janssen, Novartis, Onconova: Honoraria, Research Funding. Díez-Campelo:Celgene: Research Funding, Speakers Bureau; Novartis: Research Funding, Speakers Bureau; Janssen: Research Funding. Schlenk:Boehringer-Ingelheim: Honoraria; Pfizer: Honoraria, Research Funding; Arog: Honoraria, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Teva: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees. Gaidano:MorphoSys; Roche; Novartis; GlaxoSmithKline; Amgen; Janssen; Karyopharm: Honoraria, Other: Advisory boards; Celgene: Research Funding. Perez de Oteyza:Eli Lilly and Company: Research Funding. Cleverly:Eli Lilly and Company: Employment, Equity Ownership. Chiang:Eli Lilly and Copany: Employment. Lahn:Eli Lilly and Company: Other: Former employee. Desiaih:Eli Lilly and Company: Employment. Guba:Eli Lilly and Company: Employment, Equity Ownership. List:Celgene Corporation: Honoraria, Research Funding. Komrokji:Pharmacylics: Speakers Bureau; Novartis: Research Funding, Speakers Bureau; Incyte: Consultancy; Celgene: Consultancy, Research Funding.

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Increased Interleukin-8 (IL8)-CXCR2 Signaling Promotes Progression of Bone Marrow Fibrosis in Myeloproliferative Neoplasms

Blood ◽

10.1182/blood-2020-138843 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 6-7

Author(s):

Andrew Dunbar ◽

Min Lu ◽

Mirko Farina ◽

Young Park ◽

Julie Yang ◽

...

Keyword(s):

Bone Marrow ◽

Overall Survival ◽

Board Of Directors ◽

Research Funding ◽

Myeloproliferative Neoplasms ◽

Private Company ◽

Advisory Committees ◽

Cd34 Cells

Introduction: Elevated pro-inflammatory cytokines are a hallmark feature of myeloproliferative neoplasms (MPNs). The pro-inflammatory cytokine interleukin-8 (IL8) is increased in patients with myelofibrosis (MF) and correlates with adverse outcome, including overall survival. Previously, the Levine/Fang labs identified increased IL8 secretion from individual CD34+ stem cells in a subset of MF patients. The role of IL8 and its cognate receptors CXCR1/2 in MF pathogenesis has not been delineated. Methods: Single-cell cytokine assays were performed on isolated CD34+ cells from 60 clinically annotated MPN patients (20 MF, 20 PV, 20 ET) using a previously described micro-chip platform (Kleppe et al, Can Disc 2013). 10 healthy donors (CD34+ cells from hip replacements) were used as controls. Integrated RNA-Seq and Assay for Transposase-Accessible Chromatin followed by next-generation sequencing (ATAC-Seq) was performed on CD34+ cells from MPN patients with and without expanded IL8 secreting clones for gene expression/chromatin accessibility analysis. To model the role of IL8-CXCR2 on fibrosis in vivo, the human MPLW515L transplant model (hMPLW515L) of MF was used. Specifically, wild-type (WT) murine bone marrow (Creneg-Cxcr2f/f; Cxcr2WT) or marrow lacking the CXCR2 receptor (VavCre-Cxcr2f/f; Cxcr2KO)were retrovirally infected with MSCV-hMPLW515L-IRES-GFP and transplanted into lethally irradiated WT recipient mice and monitored for disease. Blood counts, chimerism, and flow cytometry were assayed. Moribund mice were sacrificed and assayed for grade reticulin fibrosis and overall survival. Results: Single-cell cytokine assays confirmed an increased proportion of IL8-secreting CD34+ cells in MF patients (40%) in comparison to other MPN sub-types (10% PV/0% ET) (Figure 1A). MF patients with expanded IL8 secreting clones (defined as >50% of total CD34+ cells) had increased leukocytosis (p<0.0001), larger spleen sizes (p=0.0004), greater prevalence of constitutional symptoms (p=0.0084), and higher-grade reticulin fibrosis in marrow (Figure 1B) in comparison to MF patients without prevalent IL8 clones. IHC confirmed increased IL8 expression in marrow biopsies from 8/15 MF patients in comparison to 0/4 normal controls (Figure 1C), and high IL8 expression was also observed in MF splenic megakaryocytes (MKs) as well as in splenic stromal/endothelial cells not seen in normal spleen (Figure 1D). Integrated RNA-Seq/ATAC-Seq analysis of IL8-high MF patients confirmed up-regulation of IL8-CXCR2 signaling and enrichment in pro-inflammatory pathways (i.e TNFa, NFkB, etc) by GSEA, as well as increased expression/accessibility of pro-inflammatory genes S100A8 and S100A9-previously implicated in fibrosis development. Flow analysis of IL8-high MF CD34+ cells revealed enhanced surface expression of CXCR2 and its analog CXCR1, such that MF was characterized by increased IL8 ligand and receptor expression (Figure 1E) and coincided with enhanced NFkB pathway activity (Figure 1F). Consistent with this, colony forming assays of cultured MF CD34+ cells revealed enhanced colony output when cultured with IL8 compared to WT CD34+ cells-an effect ameliorated by co-treatment with the CXCR1/2 antagonist Reparixin (Figure 1G). In vivo, hMPLW515L adoptive transplant with Cxcr2KO hematopoietic donor cells demonstrated improved leukocytosis, thrombocytosis (Figure 2A) and splenomegaly in comparison to Cxcr2WT hMPLW515L recipient mice. Pathologic analysis revealed a reduction in reticulin fibrosis in bone marrow (Figure 2B) and spleen, translating into an improvement in overall survival (Figure 2C). Notably, a significant reduction in dysplastic MKs-a hallmark feature of MF-was also observed in Cxcr2KO hMPLW515L mice (Figure 2D) supporting a role for CXCR2 signaling in MK proliferation. Conclusion: IL8 secreting clones are associated with increased symptom severity and fibrosis grade in MF. Gene expression of MF CD34+ IL8 secreting clones shows up-regulation of inflammatory genes S100A8/A9, implicated in myofibroblast proliferation. Cxcr2 KO abrogates fibrosis formation and prolongs survival in the hMPLW515L model, and CXCR1/2 inhibition impairs colony forming capacity of MF CD34+ cells. These data suggest pharmacologic inhibition of this pathway should be investigated as potential therapy in MF and in PV/ET patients at high risk of fibrotic transformation. Disclosures Fan: IsoPlexis: Current Employment, Current equity holder in private company; Singleron Biotechnologies: Current Employment, Current equity holder in private company. Levine:Morphosys: Consultancy; Prelude Therapeutics: Research Funding; Qiagen: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Gilead: Honoraria; Loxo: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy; Amgen: Honoraria; Astellas: Consultancy; Imago: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; C4 Therapeutics: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Isoplexis: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria, Research Funding; Roche: Consultancy, Honoraria, Research Funding; Lilly: Consultancy, Honoraria; Janssen: Consultancy. Hoffman:Protagonist: Consultancy; Abbvie: Membership on an entity's Board of Directors or advisory committees; Dompe: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Forbius: Consultancy.

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Failures and Successes in Pediatric Patients with Acute Myeloid Leukemia with First Relapse: A Large International Report on Current Treatment Strategies and Outcome

Blood ◽

10.1182/blood-2020-141774 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 6-7

Author(s):

Mareike Rasche ◽

Martin Zimmermann ◽

Emma Steidel ◽

Todd A. Alonzo ◽

Richard Aplenc ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Myeloid Leukemia ◽

Research Funding ◽

Pediatric Patients ◽

Advisory Committees ◽

First Relapse ◽

Pediatric Aml ◽

Acute Myeloid

BACKGROUND: Children with high risk acute myeloid leukemia (AML) still experience consistently high rates of relapse. Survival after first relapse increased from 21% between 1987 and 1997 up to 39% in recent studies. However, since 2009, there have been no publications on subsequent large pediatric AML relapse trials. As the indications for HSCT during first-line treatment have been extended since then, the current survival of these patients at relapse remains unclear. Herein, we report outcome results from the BFM and COG study group, which represents the largest available dataset analyzed for post-relapse survival. PATIENTS AND METHODS: Pediatric patients with first relapse of AML (no Down syndrome, secondary leukemia or FAB M3) have been analyzed from two large study groups with patients from the United States, Canada, Australia, New Zealand, Germany, Austria, Czech Republic and Switzerland. Out of 1222 patients in the BFM cohort (AML-BFM study 2004, registry 2012 and study 2012), 350 experienced at least one relapse and 197 of those had a first relapse after closure of the last I-BFM relapse trial (04/2009 through 2017). Within the Children's Oncology Group (COG) Phase 3 trials (AAML0531 and AAML1031, n=2119) 852 pediatric patients suffered a relapse. Five-year probability of overall survival (pOS) and event-free survival (pEFS) were calculated according to Kaplan-Meier. EFS was calculated for the BFM cohort as time from relapse to the next event (second relapse, death, failure to achieve a second remission or secondary malignancy) or until last follow-up, while OS reflects the time from relapse until death or last follow-up. The Cox proportional hazards model was used for multivariate analysis of outcomes. Living patients were censored at last follow-up with a median follow-up after relapse of 4·2 years (BFM) and 4·8 years (COG). Data have been frozen at 03/27/2020 (BFM) and 03/31/2020 (COG). RESULTS: In the 197 patients with relapse after closure of the last BFM relapse trial (04/2009 through 2017) the pOS at 5 years was 42±4% (BFM). The 5-year pOS in patients relapsing after COG trials 2006-2018 was 35±2% (n=852). Patients experiencing a relapse between 2014 to 2017 had a pOS of 49±6% (BFM, n=78) and 40±3% (COG, n=333). Risk classification at initial diagnosis and a short time from diagnosis to relapse predicted a diminished survival probability in both cohorts (see Table 1). However, the absence of full hematopoietic regeneration of the bone marrow after re-induction did not predict survival: Within the BFM dataset, a subgroup analysis in all patients receiving DNX-FLA (n=156) have been performed. Initial characteristics are comparable to the total cohort. Among these patients 147 were evaluable for response (7 excluded due to early death before evaluation, 2 for insufficient data). Eighty-nine (57%) achieved a CR (n=69) or CRp (n=20) and 52 (33%) no response. Overall survival was superior for patients with a CR/CRp (54±6% (CR/CRp) vs. 32±7% (No CR/CRp); p=0·0064), but long-term survival was still possible even with a poor re-induction response. Patients with a CRp had a comparable survival to those with a CR after a second re-induction (pOS 60±11% (CRp) vs. pOS 52±7% (CR); p=0·57). Patients with >5% leukemic blasts (n=32) had the lowest survival (pOS 27±9%). The 5-year pEFS for this cohort was 29±4% (pEFS 50±6% (CR) vs. pEFS 50±11% (CRp)). The analysis of post-relapse treatment showed that the vast majority of patients who survive had a HSCT following relapse. By landmark analysis, survival was significantly higher in patients with subsequent HSCT compared to that of non-transplanted patients (BFM: pOS 53±4%, n=154 vs. pOS 5±5%, n=21; p(Mantel-Byar)=0·0002). CONCLUSION: This is the largest report to date on post relapse survival in children with AML. Our analysis confirmed previously described risk factors for poor survival while also highlighting new findings contrary to established standards. Strikingly, the absence of full hematopoietic regeneration of the bone marrow after re-induction did not predict survival at first relapse, thereby questioning the current value of the established International Working Group Criteria published by Cheson et al for response-evaluation in pediatric AML. As the international pediatric AML community embarks on collaborative efforts to evaluate new therapies in children with relapsed AML, a comprehensive review of post relapse survival is critical. Disclosures Bourquin: Servier: Other: Travel Support. Reinhardt:Novartis: Membership on an entity's Board of Directors or advisory committees; CLS Behring: Research Funding; bluebird bio: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Roche: Research Funding; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding.

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