Correlation of Hemophagocytosis with Clinical Criteria of Hemophagocytic Lymphohistiocytosis and Recommendations for Screening Bone Marrow Samples in Adult Patients

Introduction Hemophagocytic lymphohistiocytosis (HLH) is a rare condition resulting from a dysregulated inflammatory response. It can prove difficult to diagnose and portends a poor prognosis. Bone marrow (BM) biopsy is an easily accessible test that is often used to identify the presence of hemophagocytosis and assess for underlying malignancy. Currently there are no evidence-based guidelines on the reporting of hemophagocytosis on BM biopsy and no reports of a correlation between hemophagocytosis with the clinical diagnostic criteria for HLH. We therefore aimed to assess if the amount of hemophagocytosis identified in the BM biopsy correlates with HLH-2004 criteria. Secondary aims were to evaluate inter-observer variability in reporting hemophagocytosis, and to formulate recommendations for screening in BM specimens. Method A retrospective review of bone marrow biopsies from adult patients under investigation for HLH was undertaken independently by 2 hematopathologists who were blinded to the original biopsy report. Relevant clinical and laboratory data was extracted from medical records. The average number of actively hemophagocytic cells in each slide prepared from BM aspirates were quantified into 0, 1, 2-4 and ≥5. On trephine samples, hemophagocytosis was reported as either 'present' or 'absent', with the assistance of the CD68 immunohistochemical stain. Cases with discordance pertaining to the degree of hemophagocytosis were reviewed by both assessors to reach a consensus. Results Sixty-two specimens from 59 patients were available for assessment. An underlying hematological condition was identified in 34 cases (58%). The most common underlying hematological condition was lymphoma, found in 15 cases (25%). There was a significant association between the amount of hemophagocytosis identified on the aspirate samples and the number of HLH-2004 criteria met (p<0.05). In patients where hemophagocytosis was present (n=31), there was a significant correlation between the amount of hemophagocytosis and ferritin levels (p<0.05). Interobserver variability was present in 63% of cases. Based on our review, we make the following recommendations for reporting of hemophagocytosis in the BM samples:> 1. Count only macrophages ingesting intact hemopoietic cells. W2. Quantify the average number of active histiocytes per aspirate slide. W3. Count histiocytes away from particles where the cellular outline is clear. W4. Avoid counting conglomerates of histiocytes where the cellular margins are indistinct W5. On the aspirate specimen, assess for hemophagocytosis on both the trail and squash preparations. W6. Delineating hemophagocytosis on trephine samples is difficult without the use of a CD68 immunohistochemical stain. Interestingly, a study by Ho et al found no association between the BM histologic findings and the probability of hemophagocytosis (Ho et al, American Journal of Clinical Pathology, 2014). This difference highlights the need for standardised reporting of BM specimens. Conclusion Our findings indicate that the amount of hemophagocytosis present on BM samples correlates with the number of HLH-2004 criteria met. We found marked interobserver variability which we anticipate can be rectified with our recommendations on the reporting of hemophagocytosis. Disclosures Talaulikar: Takeda: Research Funding; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

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Association between Megakaryocyte Abnormalities on Bone Marrow Smear and Response to Thrombopoietin Receptor Agonists in Adult Patients with Primary Immune Thrombocytopenia

Blood ◽

10.1182/blood-2021-151435 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 3160-3160

Author(s):

Ondine Walter ◽

Agnès Ribes ◽

Johanne Germain ◽

Jean-Baptiste Rieu ◽

Thibault Comont ◽

...

Keyword(s):

Bone Marrow ◽

Platelet Count ◽

Board Of Directors ◽

Research Funding ◽

Immune Thrombocytopenia ◽

Adult Patients ◽

Second Line ◽

Bone Marrow Smear ◽

Advisory Committees ◽

Thrombopoietin Receptor

Abstract Introduction: Immune thrombocytopenia (ITP) is an autoimmune disease due to peripheral destruction but also impaired central production of platelets. Autoimmune reaction directed against megakaryocytes (MKs) has been described, and may explain morphological abnormalities of MKs observed in some patients with primary ITP. Thrombopoietin receptor agonists (TPO-RAs) are indicated as second-line treatments for ITP, but no predictive factors of response used in clinical routine practice has been demonstrated. The utility of systematic bone marrow smears (BMS) at ITP diagnosis is discussed. Howerer, it is usually recommended before second-line treatments. Two studies have suggested an association between MK abnormalities and response to corticosteroids in primary ITP, but none have investigated this association for TPO-RAs. This study aimed to investigate the association between MK abnormalities and response to TPO-RAs in adult patients with primary ITP. Methods: The source of population was the CARMEN registry. The CARMEN (Cytopénies Auto-immunes: Registre Midi-PyréneEN) registry is aimed at the prospective follow-up of all incident ITP adults in the French Midi-Pyrénées region (South-West of France, 3 million inhabitants) since June 2013. Each investigator follows all adult patients (aged ≥18 years) with incident ITP in routine visit or hospital stay. ITP was defined by international definition (platelet count <100 x 10 9/L and exclusion of other causes of thrombocytopenia). The study population consisted in all patients included in the CARMEN registry between June 2013 and March 2018 with primary ITP, treated by TPO-RA and with a BMS before initiating TPO-RA. We excluded the patients with a number of MKs <10 MK on the BMS. Morphological abnormalities were established based on literature and defined by consensus among 3 expert cytologists (AR, JBR and VDM). All MKs present on each smear were analyzed. MKs were categorized by the presence of dysplasia (monolobed MK and/or separated nuclei and/or microMKs), and according to their stage of maturation (basophilic, granular and thrombocytogenic). All patients' medical charts were reviewed by two experts in ITP (OW and GM) to determine the response to TPO-RAs. Response was defined by a platelet count between 30 and 100 G/L with at least a doubling of basal platelet count according to the international definition. In case of subsequent exposure to both TPORAs in a single patient, response was defined by response to at least one TPO-RA in the main analysis. We performed a subgroup analysis by TPORAs. Results: During the study period, 451 patients with incident ITP were included in CARMEN-registry. Among them, 105 had been treated by TPO-RAs, including 65 with BMS before the exposure to TPORA. We then excluded 20 patients with secondary ITP and 7 with less than 10 MKs on the BMS. We finally included 38 patients in the analysis. Median age at diagnosis was 71 years (interquartile range - IQR: 31 - 94) and 34.2% were women. Thirty-three patients were treated with eltrombopag, 17 with romiplostim including 13 who were exposed to both TPORAs. Thirty-four (89.4%) achieved response. The median number of MKs analyzed per patient was 137 (IQR: 50 - 265). All results are presented in Table 1. In the main analysis, there was no significant difference in the median percentage of dysplastic MKs in responders (4.0%, 95% confidence interval - CI: 2.3 - 6.4) and non-responders (4.5%, 95% CI: 0.7 - 7.1). There was a trend for a higher proportion of granular MKs (4.5%, 95% CI: 3 - 6) and basophilic MKs (30.1%, 95% CI: 21.9 - 39.1) in non-responders comparing to responders (granular: 2.0%, 95% CI: 0 - 4.1; basophilic: 21.3%, 95% CI: 11.4 - 40.7). Results were similar in the subgroup of patients treated with eltrombopag (data not shown; the low number of patients treated with romiplostim precluded any analysis). Conclusion: In this study, neither MK abnormalities nor the pattern of MK maturation stages were significantly associated with response to TPO-RAs. These results do not support a systematic bone marrow smear in patients with primary ITP to look for morphological predictive factors of response to TPO-RA. Figure 1 Figure 1. Disclosures Comont: AstraZeneca: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding. Moulis: Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Grifols: 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; Sobi: Membership on an entity's Board of Directors or advisory committees; Argenx: Membership on an entity's Board of Directors or advisory committees.

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Phase II Trial of Single Agent Panobinostat (LBH589) In Relapsed or Relapsed/Refractory Waldenstrom Macroglobulinemia

Blood ◽

10.1182/blood.v116.21.3952.3952 ◽

2010 ◽

Vol 116 (21) ◽

pp. 3952-3952 ◽

Cited By ~ 7

Author(s):

Irene Ghobrial ◽

Tiffany Poon ◽

Meghan Rourke ◽

Stacey Chuma ◽

Janet Kunsman ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Stable Disease ◽

Research Funding ◽

Bone Marrow Involvement ◽

Ct Scans ◽

Advisory Committees ◽

Bone Marrow Biopsies ◽

Grade 3

Abstract Abstract 3952 Introduction: This study aimed to determine the safety and activity of panobinostat (LBH589) in patients with relapsed or relapsed/refractory Waldenstrom Macroglobulinemia (WM). This was based on our preclinical studies showing that panobinostat induces significant activity in cell lines and patient samples. Methods: Eligibility criteria include: 1) patients with relapsed or relapsed/refractory WM with any prior lines of therapy, 2) measurable disease and symptomatic disease, 3) off prior chemotherapy> 3 weeks, or biological/novel therapy for WM > 2 weeks. Patients received panobinostat at 30 mg three times a week (Mondays, Wed and Fridays). Patients were assessed after every cycle for the first 6 cycles and then every 3 months thereafter. Subjects who had response or stable disease were allowed to continue on therapy until disease progression or unacceptable toxicity. A planned restaging was performed at the end of cycle 6 including CT scans and bone marrow biopsies. Results: Twenty-seven patients have been enrolled to date. The median age is 62 years (47-80), the median lines of prior therapy is 3 (range, 1–7). All of the patients received prior rituximab. The median hemoglobin at screening is 10.3 g/dL (range 8.2–14.3), the median IgM M-spike by protein electropheresis at study entry is 1.9 g/dL (range, 0.63–5.1), and median serum IgM at baseline is 3610 mg/dL (range, 804- 10, 300). The median bone marrow involvement at enrollment was high for patients with WM, 50%, range (5-95%), with more than 10 patients having 70% or higher bone marrow involvement at baseline. The median number of cycles on therapy is 4 (range 1 – 12). 4 of the patients came off due to toxicity. Minimal response (MR) or better has been achieved in 15 (60%) of patients, with 6 (24%) PR, 9 (36%) MR. In addition, 9 (36%) patients achieved stable disease and 1 (4%) showed progression. The median decrease in IgM is 1020 mg/dL (0- 3970 decrease in IgM) with a median % decrease of 37.13%. Responses were prompt. The median time to first response was 2 cycles (range, 2–4). Bone marrow biopsies at the end of study (or at 6 months follow up) are available on 7 patients, of which 3 showed a significant decrease in bone marrow involvement and 4 showed stable involvement. The 4 patients who had stable bone marrow disease showed 1 PR and 3 MR responses by paraprotein level. Grade 3 and 4 toxicities include 4 (15%) cases of anemia including 1 case of hemolytic anemia, 1 (3%) case of grade 4 leucopenia (but the patient had grade 3 leucopenia at baseline), 7 (26%) of neutropenia, 14 (52%) of thrombocytopenia, 1 (4%) grade 3 GI bleed due to thrombocytopenia, 1 (3%) Grade 4 hyperglycemia and 1 (3%) grade 3 syncope and 3 (27%) grade 3 fatigue. The most common grade 2 toxicities were thrombocytopenia, anemia, and fatigue. There were 5 (20%) cases of asymptomatic pulmonary infiltrates of ground glass opacity observed on routine CT scans in follow up. Of these, 3 came off study for other reasons not related to the pulmonary infiltrates, 1 received a course of corticosteroids and had improvement of infiltrates, and 1 had dose reduction of therapy. All patients except for 2 have been dose reduced due to thrombocytopenia, fatigue, diarrhea, or anemia. Dose reductions include 25 mg three times a week, 20 mg three times a week and 20 mg three times every other week. The protocol was amended to allow a starting dose of 25 mg three times a week, which is better tolerated than 30 mg in this patient population. Conclusions: Panobinostat is an active therapeutic agent in patients with relapsed or refractory WM, with an overall response rate of 60% in patients with relapsed or refractory WM. The dose schedule of 25 mg three times a week is better tolerated in this patient population. Further studies to include this agent in combination with rituximab or bortezomib are being evaluated. Disclosures: Ghobrial: Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Anderson:Millennium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Richardson:Keryx Biopharmaceuticals: Honoraria. Treon:Millennium Pharmaceuticals, Genentech BiOncology, Biogen IDEC, Celgene, Novartis, Cephalon: Consultancy, Honoraria, Research Funding; Celgene Corporation: Research Funding; Novartis Corporation: Research Funding; Genentech: Consultancy, Research Funding.

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COMPARISON Among Citology, Histology, and FLOW Cytometry IN Evaluating Blast VALUES IN Myelodysplatic Syndromes (MDS). Survey FROM the Italian “PIEMONTE MDS REGISTRY”

Blood ◽

10.1182/blood.v116.21.4028.4028 ◽

2010 ◽

Vol 116 (21) ◽

pp. 4028-4028

Author(s):

Alessandro Levis ◽

Daniela Maria Gioia ◽

Laura Godio ◽

Mauro Girotto ◽

Bernardino Allione ◽

...

Keyword(s):

Bone Marrow ◽

Flow Cytometry ◽

Board Of Directors ◽

Research Funding ◽

Prognostic Value ◽

Univariate Analysis ◽

Laboratory Data ◽

Prognostic Impact ◽

Advisory Committees ◽

Blast Count

Abstract Abstract 4028 BACKGROUND. The corner stone of the WHO classification and prognostic scores of myelodysplastic syndromes (MDS) is the blast count in bone marrow. The standard cytology evaluation of at least 500 bone marrow cells is easy to perform, but some concerns arise about reproducibility of this method. Nowadays bone marrow trephine biopsy and flow cytometry are frequently considered for the diagnosis of MDS. However there is so far paucity of data comparing cytology, histology and flow cytometry in quantifying bone marrow blasts in order to differentiate non RAEB from BAEB-I and RAEB-II cases. AIM OF THE WORK. The Aim of the work was to analyse the differences and the prognostic impact of cytology, histology and flow cytometry in differentiating non RAEB from BAEB-I and RAEB-II. PATIENTS AND METHODS. Since 1999, clinical and laboratory data from 1256 new cases of MDS were prospectively recorded into the Piemonte MDS Registry. Blast count could be performed with the three different methods: BMC (bone marrow cytology) has been performed in 844 cases, BMH (bone marrow histology) in 874 cases, and BMF (bone marrow flow cytometry) in 636. In order to quantify blasts, immune-histochemistry evaluation of CD34+ cells was used in BMH, while both CD34+ and CD117+ cells were considered in BMF. Out of the total of the 636 patients analysed by BMF only 420 had an accurate and complete registration of CD34 and CD117 positivity and were considered for the present analysis. In two hundred and thirty six cases all three evaluations were contemporary available. The concordance of each diagnostic method with the others and their prognostic value were evaluated in both univariate and multivariate analyses. A comparison between BMC and BMH was available in 571 cases, between BMC and BMF in 228 cases, and between BMH and BMF in 279 cases. RESULTS. The disagreement in classifying patients as non-RAEB or RAEB-I or RAEB-II between BMC and BMH was 156/571 (27%), with BMH over-evaluating blasts in 114/571 cases (20%) and under-evaluating blasts in 42/571 cases (7%). The disagreement between BMC and BMF was 80/228 (35%), with BMF over-evaluating and under-evaluating blast percentage in comparison to BMC in 53/228 (23%) and in 27/228 (12%) cases respectively. The disagreement between BMH and BMF was present in 113/279 (41%), with BMF over-evaluating and under-evaluating blast percentage in comparison to BMH in 44/279 (16%) and in 69/279 (25%) cases respectively. In univariate analysis all three methods of quantifing blasts and differentiating non-RAEB from RAEB-I and RAEB-II retained an important prognostic value for both leukemic evolution and survival. However when the three models were tested in multivariate analysis in order to define the best predictor of leukemic evolution, BMC retained the best predictive value. CONCLUSIONS. When BMH or BMF are used instead of BMC in order differentiate non-RAEB from RAEB-I and RAEB-II, the shift to a different WHO category is evident in at least 30% of patients and BMH and BMF do not play the same role as BMC. BMC still remain the standard method to quantify blasts for classification and prognostic evaluation of MDS. Disclosures: Off Label Use: Lenalidomide in Mantle Cell Lymphoma. Boccadoro:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen-Cilag: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Saglio:Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

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Dynamic Stromal Changes in Myelofibrosis Patients Pre/Post JAK Inhibition Is Revealed in Clinically Archived Bone Marrow Biopsies By Smooth Muscle Actin (SMA)-CD34 Dual Immunohistochemistry

Blood ◽

10.1182/blood-2021-151458 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 3286-3286

Author(s):

Katelyn Wang ◽

Iran Rashedi ◽

James T. England ◽

Rashmi S. Goswami ◽

Larissa Liontos ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Research Funding ◽

Smooth Muscle Actin ◽

Muscle Actin ◽

Analysis Pipeline ◽

Bone Marrow Fibrosis ◽

Advisory Committees ◽

Bone Marrow Biopsies ◽

Marrow Fibrosis

Abstract The natural history of BCR-ABL1 negative myeloproliferative neoplasms (MPNs) is progression towards an overt myelofibrotic (MF) phase with variable risk to develop secondary acute myeloid leukemia. Current treatments include Janus kinase inhibitors (JAKi) which can temporarily alleviate MF-related symptoms but are non-curative and most patients eventually progress to a more advanced stage. Given the negative prognostic impact of bone marrow fibrosis in MPNs and generally poor outcome post JAKi failure, it would be important to identify in situ biomarkers that address the initiation, perpetuation and early reversal of the fibrotic reaction. The current clinical standard for bone marrow fibrosis assessment involves reticulin/trichrome stains that detect relatively static extracellular matrix products rather than the fibrosis driving cells directly. To address this, we have developed a smooth muscle actin stromal-vascular (SMA-CD34) dual immunohistochemical (IHC) technique amenable to morphologic scoring and complemented with a CellProfiler image analysis pipeline. SMA was prioritized over other validated stromal IHC markers given work by others in experimental models demonstrating SMA+ myofibroblasts to be the differentiated output of critical fibrosis inducing Gli1+ 'driver' mesenchymal stem/progenitor cells in MPN. Herein, we demonstrate the feasibility of our translational approach using a clinically annotated cohort of MF patients from the Princess Margaret Cancer Centre MPN Registry. After selecting for high quality (>1.0 cm) paired pre and post JAKi biopsies amenable to image and transcriptome-based analysis, the pilot cohort was comprised of 13 cases with 38% high-risk, 54% intermediate-2 and 8% intermediate-1 risk by DIPSS. Driver mutations were JAK2 V617F (77%), CALR (15%) and other (8%). JAKi therapies included ruxolitinib (31%) + pelabresib (23%), momelotinib (15%), itacitinib (15%) and pacritinib (8%). The SMA-CD34 stromal assessment at baseline revealed distinct interstitial myofibroblast patterns and vascular perturbations not captured by conventional clinical hematopathology assessment (e.g. SMA+ dilated sinusoids). A SMA-CD34 scoring system was developed using a 4-point scale representing normal (0 pts), increased vascularity (1 pt), focal interstitial SMA (2 pts), multifocal interstitial SMA (3 pts) and diffuse SMA (4 pts). Scoring was then performed by blinded hematopathologists. A trend towards JAK2 mutated MF cases demonstrating higher SMA grade at baseline was noted. Interestingly, variable trajectories in SMA scores emerged following treatment with JAKi. Specifically, SMA signals had increased in 15%, decreased in 46% and were stable in 38% post-JAKi when using a morphologic SMA grading scheme. When compared to reticulin fibrosis, the severity of SMA signals had diverged in 1/3 of the cases (e.g. SMA grade decreased, reticulin grade stable). To further complement the SMA-CD34 morphologic grading, a CellProfiler image analysis pipeline was developed yielding a non-vessel associated normalized SMA area metric as a supervised correlate of the clinical SMA scoring system (R 2 = 0.68). Additional supervised and unsupervised bioinformatic approaches for clustering of relevant SMA-CD34 features including an algorithm that informs SMA spatial patterns with respect to niche elements such as arterioles (CD34+SMA+), sinusoids (CD34+) and adipocytes is in development. Lastly, Nanostring Fibrosis V2 panel was employed on a subset that met RNA concentration and quality metrics. Exploratory interpretation showed significant differentially expressed genes in pre vs. post JAKi specimens related to lipid metabolism such as ADIPOR1, SCD, ELOVL6 as well as the chemokine CXCL16. This may suggest a link between fatty acid metabolism and inflammatory differentiation along the SMA-vascular axis in the bone marrow modulated by JAKi treatment. SMA-CD34 IHC stratifies MF bone marrow biopsies differentially from standard WHO reticulin/trichome grading providing a practical formalin-fixed paraffin embedded (FFPE) tissue-based biomarker for assessing fibrosis related bone marrow niche elements from archived clinical samples. While our pilot numbers precluded statistical evaluation by JAKi-type, clinical response and NGS mutational profile at this time, further studies are underway to validate the SMA-CD34 signature on a larger MF cohort. Figure 1 Figure 1. Disclosures Gupta: Sierra Oncology: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS-Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy; Incyte: Honoraria, Research Funding; Constellation Pharma: Consultancy, Honoraria; Pfizer: Consultancy.

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Development and Exploitation of a Fully Human and Modular Organotypic Bone Marrow Niche Model to Study the Role of Stroma-Produced Factors in Human MDS

Blood ◽

10.1182/blood-2020-142782 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 23-23

Author(s):

Alexander Schaeffer ◽

Ewelina Czlonka ◽

Irene Tirado-González ◽

Thomas Böse ◽

Jennifer Beauvarlet ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Research Funding ◽

Ex Vivo ◽

Standard Of Care ◽

Bone Marrow Niche ◽

Advisory Committees ◽

Bone Marrow Biopsies ◽

Primary Bone ◽

Primary Bone Marrow

Background: Myelodysplastic syndromes (MDS) are a heterogenous group of stem cell driven disorders primarily affecting the elderly and characterized by inefficient production of mature blood cells and a high risk (30%) of evolution to secondary acute myeloid leukemia. Despite tremendous progress in the past decade, treatment options for MDS patients remain limited, and primarily address disease symptoms, rather than altering disease course. This points to the urgent need to better understand the pathogenesis of this heterogenous group of syndromes to develop new therapies that address disease vulnerabilities. However, this effort has been largely hampered by the limited availability of model systems that allow the exploration of MDS biology in a fully humanized setting. In recent years, studies from our lab and others, have highlighted the crucial role niche cells play in human MDS, hence reinforcing the notion that MDS is a disease of a tissue rather than hematopoietic cells alone. Therefore, exploration of MDS biology requires the further development of fully human MDS models in which both constituents of the disease, namely hematopoietic and niche cells, are present. Methods: To address this issue we successfully isolated endothelial cells (ECs) and mesenchymal stromal cells (MSC) from bone marrow biopsies obtained from MDS patients or healthy age matched controls, and subsequently utilized them to develop fully human 2D and 3D organotypic niche models, which were successfully used to support normal and MDS HSPCs expansion ex-vivo. The 3D system makes use of a collagen scaffold, as this protein makes up for 90% of the matrix proteins in the bone. Importantly, MSC and EC cultures could be successfully established from several independent donors and immortalized to generate primary cell lines that can be used to reproducibly establish these ex-vivo systems in a robust manner. Moreover, we could show that these niche cells were easily amenable to genetic editing using CRISPR-Cas9 technology as well as modified to carry fluorescent reporter proteins for tracking cellular interactions using live cell imaging and confocal microscopy. Results: In this work, we successfully isolated human mesenchymal and endothelial cells, from primary bone marrow biopsies (MDS and healthy) and established fully human 2D and 3D organotypic co-cultures ex-vivo. Of note, although bone marrow ECs represent an essential component of the hematopoietic niche, they have so far been omitted in previously described human bone marrow niche models, owing to the notorious difficulties in isolating and expanding this cell type from primary bone marrow biopsies. Therefore, we established immortalized EC lines (iECs) that faithfully recapitulate the morphological, phenotypic and functional features of primary bone marrow ECs. When cultured at defined ratios and under defined conditions, MSCs instructed ECs and iECs to form of vessel-like structures that mimic the meshwork observed in vivo and are typically escheated by aSMA positive cells that stabilize the structures. Genetic manipulation of the cellular components of the niche also allowed to explore the functional relevance of a specific ECM protein, which we previously identified to be significantly upregulated in MSCs isolated from MDS patients, namely the Secreted Protein Acidic and Rich in Cysteine (SPARC). SPARC ablation triggered enhanced proliferation of MDS derived HSPCs and sensitized them treatment with 5-Azacytidine, a standard of care hypomethylating agent used for the treatment of MDS patients. Additional studies are underway to further understand the underlying molecular mechanisms and define a potential druggable target that could sensitize MDS cells to standard of care treatment. Besides gene targeting studies, these organotypic models are also being used to evaluate the relative fitness of MDS and healthy stem/progenitor cells in healthy versus patient derived niches, to explore the contribution of niche components to the establishment of the progressive clonal dominance observed in MDS. Disclosures Bönig: Terumo BCT: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kiadis: Honoraria; Bayer: Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Fresenius: Honoraria; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Uniqure: Research Funding; medac: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties; Genzyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; Healthineers: Current equity holder in publicly-traded company; Chugai: Honoraria, Research Funding; Erydel: Research Funding; Miltenyi: Honoraria, Research Funding; Polyphor: Research Funding; Sandor-Hexal: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Stage: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Platzbecker:Amgen: Honoraria, Research Funding; Geron: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding. Götze:Celgene: Research Funding. Medyouf:Bergenbio: Consultancy, Research Funding.

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Dramatic Resolution of HLH after Treatment with the JAK 1/2 Inhibitor, Ruxolitinib

Blood ◽

10.1182/blood-2019-124176 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 2325-2325

Author(s):

Scott R. Goldsmith ◽

Sana Saif Ur Rehman ◽

Cara Lunn Shirai ◽

Ravi Vij ◽

John F. DiPersio

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Bone Marrow Biopsy ◽

Salvage Therapy ◽

Hemophagocytic Lymphohistiocytosis ◽

Research Funding ◽

Acute Hepatitis C ◽

Advisory Committees ◽

Equity Ownership ◽

Ifn Γ

Introduction: Preclincal murine models of primary and secondary hemophagocytic lymphohistiocytosis (HLH) have demonstrated the role of JAK/STAT signaling in propagating the cytokine-mediated hyperinflammatory state. Das et al. (Blood 2016) demonstrated that ruxolitinib (rux) effectively attenuates murine HLH, and Albeituni et al. (Blood 2019) found it superior to IFN-γ inhibition (the target of emapalumab-lzsg). A few single case reports exist in which rux was used for salvage therapy, however they report only limited clinical success and/or were used as a bridge to allogeneic stem cell transplantation. Here we present a series of three consecutive cases in which rux was employed as either salvage therapy for relapsed/refractory secondary HLH or front-line for moderate HLH manifestations. Importantly, each patient was maintained on a taper of rux which prevented recurrence and obviated the need for allogeneic transplantation. Two of the three patients have been tapered completely off rux without recurrence of either laboratory or clinical manifestations of HLH at the time of this submission. Case 1: Patient 1 is a 24 yo woman who had initially presented to an outside hospital with jaundice and was found to have a warm AIHA. She was initially started on steroids, but developed worsening anemia, fever, splenomegaly, and encephalopathy. On transfer to us she had ferritin of 58,505 ng/ml. Her bone marrow biopsy demonstrated abundant hemophagocytosis (Fig. 1B,C). She met HLH criteria and was started on HLH-94 protocol; however, her total and direct bilirubin climbed dramatically, peaking at 95.2 and 82.0 mg/dl, respectively. Rux 5mg BID was initiated as salvage therapy, and within 48 hours, her labs significantly improved, her fevers resolved, and she became responsive to blood transfusions (Fig. 1A). After two weeks on rux, she developed recurrent hemolysis. Her dose was increased to 20mg BID, resulting in a complete resolution of her hemolysis, fevers, transaminitis and hyperbilirubinemia. After 3 months of clinical stability, rux was tapered. She has been off rux now for three months. Case 2: Patient 2 is a 26 yo woman who presented with unremitting fevers and myalgias, and was found to have an acute hepatitis C infection. Her ferritin was 24,023ng/ml, and a bone marrow biopsy demonstrated abundant hemophagocytosis. She initially responded to the HLH-94 protocol; however, attempts to hold treatment following induction were met with recurrent fevers, encephalopathy, and hyperferritinemia. She transferred to us, and a repeat bone marrow biopsy demonstrated persistent hemophagocytosis (Fig. 2B,C), while her ferritin was 15,073 ng/ml. We initiated salvage treatment with rux 10mg BID. Her fevers, encephalopathy, and lab abnormalities quickly improved; her ferritin fell to 2,973ng/ml within 3 days (Fig. 2A). A small subsequent elevation in her ferritin prompted an increase of the rux to 20mg BID. She improved and was discharged on rux maintenance at 20mg BID. Since discharge, she remains asymptomatic with mildly elevated ferritin levels, mild pancytopenia, and is tolerating a slow wean of rux without incident. Case 3: Patient 3 is a 40 yo man with a diagnosis of hairy cell leukemia who received 5 days of cladribine. He developed febrile neutropenia 2 days following the end of chemotherapy. His infectious workup was negative with the exception of a positive peripheral blood EBV DNA PCR. He developed a mononucleosis-like syndrome, with persistent high fevers, splenomegaly, and hyperferritinemia to 6684 ng/ml. He also developed hepatic dysfunction with a direct hyperbilirubinemia peaking at 14.1 mg/dl and coagulopathy. He was treated initially with dexamethasone without resolution. A bone marrow biopsy demonstrated abundant hemophagocytosis (Fig. 3B,C). Given modest manifestations and concern that chemotherapy would exacerbate his immunosuppression, rux was initiated at 10mg BID. The liver dysfunction rapidly improved, and fevers resolved within 3 days (Fig. 3A). All other manifestations resolved within 1 week, and he was able to taper and discontinue rux within 2 months. Conclusions: The preclinical data by Albeituni et al. coupled with our clinical observations suggest that ruxolitinib may be a viable alternative to aggressive chemotherapy regimens such as HLH-94 or anti-IFN-γ (emapalumab-lzsg) therapy for HLH, and clinical trials should be considered. Disclosures DiPersio: Karyopharm Therapeutics: Consultancy; Cellworks Group, Inc.: Membership on an entity's Board of Directors or advisory committees; NeoImmune Tech: Research Funding; Macrogenics: Research Funding, Speakers Bureau; Bioline Rx: Research Funding, Speakers Bureau; RiverVest Venture Partners Arch Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Magenta Therapeutics: Equity Ownership; WUGEN: Equity Ownership, Patents & Royalties, Research Funding; Amphivena Therapeutics: Consultancy, Research Funding; Incyte: Consultancy, Research Funding; Celgene: Consultancy. OffLabel Disclosure: Ruxolitinib was used off-label for the treatment of Hemophagocytic Lymphohistiocytosis (HLH) in the relapsed/refractory setting and in a patient who was unable to tolerate standard therapy. This was not in a clinical trial, but reported as a case series

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Final Results of the Phase II Trial of Single Agent Panobinostat (LBH589) in Relapsed or Relapsed/Refractory Waldenstrom Macroglobulinemia

Blood ◽

10.1182/blood.v118.21.2706.2706 ◽

2011 ◽

Vol 118 (21) ◽

pp. 2706-2706 ◽

Cited By ~ 1

Author(s):

Irene M. Ghobrial ◽

Ranjit Banwait ◽

Tiffany Poon ◽

Federico Campigotto ◽

Erica N Boswell ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Stable Disease ◽

Research Funding ◽

Bone Marrow Involvement ◽

Ct Scans ◽

Advisory Committees ◽

Bone Marrow Biopsies ◽

Grade 3

Abstract Abstract 2706 INTRODUCTION: This study aimed to determine the safety and activity of panobinostat (LBH589) in patients with relapsed or relapsed/refractory Waldenstrom Macroglobulinemia (WM). This was based on our preclinical studies showing that panobinostat induces significant activity in cell lines and patient samples. METHODS: Eligibility criteria include: 1) patients with relapsed or relapsed/refractory WM with any number of prior lines of therapy, 2) measurable disease and symptomatic disease, 3) Not receiving chemotherapy > 3 weeks, or biological/novel therapy for WM > 2 weeks. Patients received panobinostat initially at 30 mg three times a week (Mondays, Wednesdays and Fridays). Patients were assessed after every cycle for the first 6 cycles and then every 3 months thereafter. Subjects who had response or stable disease were allowed to continue on therapy until disease progression or unacceptable toxicity. A planned restaging was performed at the end of cycle 6 including CT scans and bone marrow biopsies. RESULTS: Thirty eight patients have been enrolled on this study from August 2009 to March 2011. Two patients withdrew prior to receiving treatment. Out of the 36 patients that received treatment, 35 patients were evaluable for response. The median age is 62 years (range, 47–67) and the median lines of prior therapy is 2 (range, 1–7). All of the patients had received prior rituximab. The median hemoglobin at screening is 10.7 g/dL, the median IgM M spike by protein electropheresis at study entry is 1.96 g/dL (range, 0.63–5.1), and median serum IgM at baseline is 3610 mg/dL (range, 804–10, 300mg/dL). The median bone marrow involvement at enrollment was high for patients with WM 48% (range, 5–95%), with 14 patients having 70% or higher bone marrow involvement at baseline. The median number of cycles on therapy is 3 (range, 1–12). Minimal response (MR) or better has been achieved in 49% of patients (17/35), with 6/35 PR and 11/35 MR. In addition, 16/35 (46%) patients achieved stable disease and 2/35 (6%) showed progression within the first 60 days of therapy. The median decrease in IgM is 760 mg/dL (range, 0–3970mg/dL decrease in IgM), which is a median decrease in IgM of 32% (range, 0–79%). The median time to first response was 2 cycles (range, 2–4). At 6 months on therapy, bone marrow biopsies are available on 9 patients, of which 5 show a significant decrease in bone marrow involvement, 3 are stable, and 1 show increase in bone marrow involvement. Of the 8 patients showing a decrease or stable bone marrow involvement from baseline, 4 are in PR and 4 are in MR by IgM level. Grade 3 and 4 toxicities include anemia (22%) including 1 case of hemolytic anemia, leukopenia (11%), neutropenia (33%), thrombocytopenia (61%), hypophosphatemia (3%), fatigue (11%), nausea (3%), 1 grade 3 GI bleed, and 2 grade 3 syncope. The most common grade 2 toxicities were anemia, leukopenia, neutropenia, fatigue and GI symptoms. There were 4 cases of asymptomatic pulmonary infiltrates of ground glass opacity observed on routine CT scans in follow up consistent with idiopathic pneumonia/pneumonitis. Of these, 4 came off study and 1 received corticosteroids while on therapy and had improvement in the infiltrates on further follow up. Subsequently, the protocol was amended to allow a starting dose of 25 mg, which proved to be better tolerated than 30 mg in this patient population with less fatigue and cytopenias;14/36 (39%) patients were enrolled on the 25 mg dose. CONCLUSIONS: Panobinostat is an active therapeutic agent in patients with relapsed or refractory WM, with an overall response rate of 49% in patients showing MR or better, and a clinical benefit rate of 95% of stable disease or better. The drug was generally well tolerated but the observation of pulomanary toxicity in some patients warrants further evaluation. The dose schedule of 25 mg three times a week is better tolerated than 30 mg dosing in this patient population. Further studies to include this agent in combination with rituximab and/or bortezomib warrant further evaluation. Disclosures: Ghobrial: Celgene: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees, Research Funding; Noxxon: Membership on an entity's Board of Directors or advisory committees, Research Funding; Millennium: Research Funding; Bristol-Myers Squibb: Research Funding; Noxxon: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees. Off Label Use: panobinostat in WM. Anderson:Millennium: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: 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; Acetylon: Equity Ownership. Richardson:Millennium: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Matous:Celgene: Speakers Bureau; Millenium: Speakers Bureau; Cephalon: Speakers Bureau.

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Natural-Killer Cell Cytotoxicity Is a Diagnostic and Prognostic Marker in Adult Patients with Secondary Hemophagocytic Lymphohistiocytosis: Results from a Prospective Phase II Observational Study

Blood ◽

10.1182/blood-2019-129676 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 2331-2331

Author(s):

Han Bi Lee ◽

Jae-Ho Yoon ◽

Gi June Min ◽

Sung-Soo Park ◽

Silvia Park ◽

...

Keyword(s):

Natural Killer Cell ◽

Natural Killer ◽

Board Of Directors ◽

Hemophagocytic Lymphohistiocytosis ◽

Research Funding ◽

Killer Cell ◽

Adult Patients ◽

Survival Outcomes ◽

Advisory Committees ◽

Nk Cytotoxicity

Background: Hemophagocytic lymphohistiocytosis (HLH) can be life-threatening if not detected and treated appropriately. Diagnosing HLH can be confusing due to other similar febrile diseases that present with cytopenia. Although a decrease in natural-killer cell (NK)-cytotoxicity is an important diagnostic parameter for primary HLH, the role in adult HLH has not been well-defined. Aim: To identify the diagnostic relevance and the significant cut-off values for NK cytotoxic function, we focused on patients that presented with fever with either cytopenia or evidence of hemophagocytosis. NK cytotoxicity was calculated at the time of diagnosis and we tried to identify significant differences between the causes of disease. Finally, the overall treatment response and survival outcomes were also evaluated based on the level of NK cytotoxicity in several subgroup analyses. Methods: We prospectively enrolled 123 adult patients that presented with fever accompanied by either cytopenia in at least two lineages or marrow hemophagocytosis. A diagnosis of HLH was based on HLH-2004 criteria and treated based on HLH-94 protocol. HLH-suspected patients were initially treated with 10mg/BSA of dexamethasone, and etoposide was considered if clinical improvement was not observed within 7 days after dexamethasone. Patients other than HLH were treated with disease-specified therapy. NK-cytotoxicity was calculated at diagnosis by K562-cell direct lysis using flow-cytometry. Results: HLH (n=60) was determined to be caused by Epstein-Barr virus (EBV, n=11), infection other than EBV (n=16), malignancies (n=19), and unknown (n=14). Febrile diseases other than HLH (n=63) were diagnosed as rheumatologic disease (n=22), malignancies (n=21), infection (n=12), non-malignant hematological diseases (n=6), and unknown (n=2). The results revealed that an HLH diagnosis was significantly correlated with lower NK-cytotoxicity, compared to other diseases (12.1% vs. 26.2%, p<0.001), and a value less than 22% was a relevant cut-off for diagnosing HLH. Additionally, lower NK-cytotoxicity showed inferior 2-year overall survival in the non-malignancy subgroup (72.2% vs. 88.8%, p=0.038). Multivariate analysis showed that low NK-cytotoxicity, splenomegaly, and marrow hemophagocytosis were independent diagnostic parameters for HLH, and low NK-cytotoxicity and EBV-association were related with poor survival outcomes in non-malignant febrile diseases. Conclusion: We determined that decreased NK-cytotoxicity is a relevant marker that can be used for diagnosis of adult HLH compared with several similar febrile diseases and is also related to poor OS in non-malignant febrile diseases. Based on these results and other prospective studies, we hope that additional relevant diagnostic criteria for adult HLH can be identified in the near future. Disclosures Kim: Celgene: Consultancy, Honoraria; Astellas: Consultancy, Honoraria; Hanmi: Consultancy, Honoraria; AGP: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; SL VaxiGen: Consultancy, Honoraria; Novartis: Consultancy; Amgen: Honoraria; Chugai: Honoraria; Yuhan: Honoraria; Sanofi-Genzyme: Honoraria, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Handok: Honoraria; Janssen: Honoraria; Daiichi Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Otsuka: Honoraria; BL & H: Research Funding. Lee:Alexion: Consultancy, Honoraria, Research Funding; Achillion: Research Funding.

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The Metabolomic Status of the Differentiating Myeloid Lineage in MDS with Low and High Bone Marrow Blast Counts

Blood ◽

10.1182/blood-2020-140468 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 32-33

Author(s):

Aikaterini Poulaki ◽

Theodora Katsila ◽

Ioanna E Stergiou ◽

Stavroula Giannouli ◽

Jose Carlos Gόmez Tamayo ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Warburg Effect ◽

Research Funding ◽

Metabolic Reprogramming ◽

Negative Ion ◽

Advisory Committees ◽

Myeloid Lineage ◽

Epigenetic Modifier ◽

Cellular Fate

Despite its major role in cellular biology, metabolism has only recently acquired a principal role in the research of the most profound cellular cycle disturbance, cancerous transformation. Myelodysplastic syndromes (MDS), a massively heterogeneous group of Hematopoietic Stem/ Progenitor Cell (HSC/HPC) disorders lie at the interface of normal differentiation and malignant transformation and have thus drew great attention due to their polymorphic presentation and elusive pathophysiology. Failure to establish a direct etiopathogenic relationship with specific genetic aberrations, along with the novel finding of a highly deregulated HIF1 activity by several unrelated research groups worldwide, including ours, urged us to investigate the metabolomic status of human bone marrow derived differentiating myeloid lineage in comparison with one another as well as with control samples. BM aspiration samples collected from 14 previously untreated MDS patients (10 patients with <5% (1 SLD, 8MLD, 1del5q, group 1- G1) and 4 with >5% BM blasts (2 EB1, 2 EB2group 2 - G2)) and 5 age matched controls. Myeloid lineage cells were isolated through ficoll bilayer protocol. All samples contained homogenous myeloid lineage subpopulations, assessedthrough optical microscopy. Two different metabolite extraction protocols were applied. The one with the best metabolites yield (50% MeOH, 30% ACN, 20% H2O) was chosen. LC-MS/MS analysis was performed using UPLC 1290 system (Agilent Technologies) coupled to a TripleTOF 5600+ mass spectrometer (SCIEX) equipped with SWATH acquisition, SelexION technology and an electrospray ionization source (ESI). A threshold of a minimum of three samples expressing a given metabolite was set against data sparsity. Data tables were scaled by data centering and setting unit variance. Log2 Foldcalculation and PLS analysis were performed for the two datasets (positive and negative ion-modes). R2 and Q2 for positive ion-mode and negative-ion mode analyses were determined. Both datasets were merged in a unique data table by taking into account maximum absolute log2 foldvalues, when a metabolite was found in both datasets. Warburg effect was evidently present in both the G1 and G2 vs control comparisons, yet the role of this stem like aerobic glycolysis seems markedly different in the two groups. While in the G2 group it serves to rescue glucose from complete burn in the mitochondrion and thus shuts it towards nucleotide synthesis (Pentose Phosphate Pathway found upregulated) with the added benefit of increased reduced Glutathione synthesis and improved redox state, in the G1 group proves detrimental. This greatly variable effect of the same phenomenon in the cellular fate lies upon the quality and functionality of the cellular mitochondrial content. G2 precursors presented functional mitochondrial (decreased NAD/NADH and FAD/FADH2) contrary to the G1 ones (Table). Failing TCA cycle, with increased NAD/NADH and FAD/FADH2 ratios and markedly increased ADP/ATP levels leads to FAs accumulation due to failure of effective adequate β oxidation. The uncontrolled increase in the NAD/NADH ratio stimulates upper glycolysis into a turbo mode further increasing the ADP/ATP, depleting cellular energy contents, engaging it to a never-ending deadly metabolism. The enormous abundance of upper glycolytic intermediates is relieved through phospholipid and ceramide synthesis, all found massively upregulated in both the MDS vs control yet also in the G1 vs G2 comparisons. FAs, mostly phospholipid and ceramide accumulation, interrupt the mitochondrial membrane lipidome further incapacitating metabolic integrity and inducing their autophagic degradation which further stimulates the Warburg effect. This type of metabolic reprogramming is eventually targeted to epigenetic modifier production, increased S-adenosyl-methionine, the major methyl group donor, 2-HydroxyGlutarate, a potent epigenetic modifier and notorious oncometabolite, Acetyl-Lysine, the major acetyl- group donor, even glutathione. We therefore present a model of an uncontrolled Warburg effect which in the G1 group confers premature death of the hematopoietic precursors, the ineffective hematopoiesis of MDS. Yet, under the pressure of the vastly upregulated epigenetic modifiers cellular fate changes, the G1 precursors adapt and transform to the G2 ones yet eventually to Acute Myeloid Leukemia blasts. Table Disclosures Vassilopoulos: Genesis pharma SA: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Gilead: Research Funding; Abbvie: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees.

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p53 Mediated Bone Marrow Mesenchymal Stem Cell Expansion Supports Acute Myeloid Leukemia Development

Blood ◽

10.1182/blood-2019-127245 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 523-523

Author(s):

Rasoul Pourebrahimabadi ◽

Zoe Alaniz ◽

Lauren B Ostermann ◽

Hung Alex Luong ◽

Rafael Heinz Montoya ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Myeloid Leukemia ◽

Research Funding ◽

Osteoblast Differentiation ◽

Hematopoietic Cells ◽

Advisory Committees ◽

Equity Ownership ◽

Mdm2 Inhibitor ◽

Acute Myeloid

Acute myeloid leukemia (AML) is a heterogeneous disease that develops within a complex microenvironment. Reciprocal interactions between the bone marrow mesenchymal stem/stromal cells (BM-MSCs) and AML cells can promote AML progression and resistance to chemotherapy (Jacamo et al., 2014). We have recently reported that BM-MSCs derived from AML patients (n=103) highly express p53 and p21 compared to their normal counterparts (n=73 p<0.0001) (Hematologica, 2018). To assess the function of p53 in BM-MSCs, we generated traceable lineage specific mouse models targeting Mdm2 or Trp53 alleles in MSCs (Osx-Cre;mTmG;p53fl/fl and Osx-Cre;mTmG;Mdm2fl/+) or hematopoietic cells (Vav-Cre;mTmG;p53fl/fl and Vav-Cre;mTmG;Mdm2fl/+). Homozygote deletion of Mdm2 (Osx-Cre;Mdm2fl/fl) resulted in death at birth and displayed skeletal defects as well as lack of intramedullary hematopoiesis. Heterozygote deletion of Mdm2 in MSCs was dispensable for normal hematopoiesis in adult mice, however, resulted in bone marrow failure and thrombocytopenia after irradiation. Homozygote deletion of Mdm2 in hematopoietic cells (Vav-Cre;Mdm2fl/fl) was embryonically lethal but the heterozygotes were radiosensitive. We next sought to examine if p53 levels in BM-MSCs change after cellular stress imposed by AML. We generated a traceable syngeneic AML model using AML-ETO leukemia cells transplanted into Osx-Cre;mTmG mice. We found that p53 was highly induced in BM-MSCs of AML mice, further confirming our findings in primary patient samples. The population of BM-MSCs was significantly increased in bone marrow Osx-Cre;mTmG transplanted with syngeneic AML cells. Tunnel staining of bone marrow samples in this traceable syngeneic AML model showed a block in apoptosis of BM-MSCs suggesting that the expansion of BM-MSCs in AML is partly due to inhibition of apoptosis. As the leukemia progressed the number of Td-Tomato positive cells which represents hematopoietic lineage and endothelial cells were significantly decreased indicating failure of normal hematopoiesis induced by leukemia. SA-β-gal activity was significantly induced in osteoblasts derived from leukemia mice in comparison to normal mice further supporting our observation in human leukemia samples that AML induces senescence of BM-MSCs. To examine the effect of p53 on the senescence associated secretory profile (SASP) of BM-MSCs, we measured fifteen SASP cytokines by qPCR and found significant decrease in Ccl4, Cxcl12, S100a8, Il6 and Il1b upon p53 deletion in BM-MSCs (Osx-Cre;mTmG;p53fl/fl) compared to p53 wildtype mice. To functionally evaluate the effects of p53 in BM-MSCs on AML, we deleted p53 in BM-MSCs (Osx-Cre;mTmG;p53fl/fl) and transplanted them with syngeneic AML-ETO-Turquoise AML cells. Deletion of p53 in BM-MSCs strongly inhibited the expansion of BM-MSCs in AML and resulted in osteoblast differentiation. This suggests that expansion of BM-MSCs in AML is dependent on p53 and that deletion of p53 results in osteoblast differentiation of BM-MSCs. Importantly, deletion of p53 in BM-MSCs significantly increased the survival of AML mice. We further evaluated the effect of a Mdm2 inhibitor, DS-5272, on BM-MSCs in our traceable mouse models. DS-5272 treatment of Osx-cre;Mdm2fl/+ mice resulted in complete loss of normal hematopoietic cells indicating a non-cell autonomous regulation of apoptosis of hematopoietic cells mediated by p53 in BM-MSCs. Loss of p53 in BM-MSCs (Osx-Cre;p53fl/fl) completely rescued hematopoietic failure following Mdm2 inhibitor treatment. In conclusion, we identified p53 activation as a novel mechanism by which BM-MSCs regulate proliferation and apoptosis of hematopoietic cells. This knowledge highlights a new mechanism of hematopoietic failure after AML therapy and informs new therapeutic strategies to eliminate AML. Disclosures Khoury: Angle: Research Funding; Stemline Therapeutics: Research Funding; Kiromic: Research Funding. Bueso-Ramos:Incyte: Consultancy. Andreeff:BiolineRx: Membership on an entity's Board of Directors or advisory committees; CLL Foundation: Membership on an entity's Board of Directors or advisory committees; NCI-RDCRN (Rare Disease Cliln Network): Membership on an entity's Board of Directors or advisory committees; Leukemia Lymphoma Society: Membership on an entity's Board of Directors or advisory committees; German Research Council: Membership on an entity's Board of Directors or advisory committees; NCI-CTEP: Membership on an entity's Board of Directors or advisory committees; Cancer UK: Membership on an entity's Board of Directors or advisory committees; Center for Drug Research & Development: Membership on an entity's Board of Directors or advisory committees; NIH/NCI: Research Funding; CPRIT: Research Funding; Breast Cancer Research Foundation: Research Funding; Oncolyze: Equity Ownership; Oncoceutics: Equity Ownership; Senti Bio: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Eutropics: Equity Ownership; Aptose: Equity Ownership; Reata: Equity Ownership; 6 Dimensions Capital: Consultancy; AstaZeneca: Consultancy; Amgen: Consultancy; Daiichi Sankyo, Inc.: Consultancy, Patents & Royalties: Patents licensed, royalty bearing, Research Funding; Jazz Pharmaceuticals: Consultancy; Celgene: Consultancy. OffLabel Disclosure: Mdm2 inhibitor-DS 5272

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