Bone Marrow Of Healthy Individuals Research Articles

Comparison of Gene Expression Levels in the p53 Pathway in Blood and Bone Marrow of Healthy Individuals

Comparison of Gene Expression Levels in the p53 Pathway in Blood and Bone Marrow of Healthy Individuals

Evidence for EpCAM and Cytokeratin Expressing Epithelial Cells in Normal Human and Murine Blood and Bone Marrow.

Epithelial cells have been identified in the blood and bone marrow of patients with cancer and other diseases. However, the presence of normal epithelial cells in the blood and bone marrow of healthy individuals has yet to be identified in a consistent way. Presented here is a reproducible method for isolating epithelial cells from healthy human and murine blood and bone marrow (BM) using flow cytometry and immunofluorescence (IF) microscopy. Epithelial cells in healthy individuals were first identified and isolated via flow cytometry using epithelial cell adhesion molecule (EpCAM). These EpCAM+ cells were confirmed to express keratin using immunofluorescence microscopy in Krt1-14;mTmG transgenic mice. Human blood samples had 0.18% ± 0.0004 EpCAM+ cells (SEM; n=7 biological replicates, 4 experimental replicates). In human BM, 3.53% ± 0.006 (SEM; n=3 biological replicates, 4 experimental replicates) of mononuclear cells were EpCAM+. In mouse blood, EpCAM+ cells constituted 0.45% ± 0.0006 (SEM; n=2 biological replicates, 4 experimental replicates), and in mouse BM, 5.17% ± 0.001 (SEM; n=3 biological replicates, 4 experimental replicates) were EpCAM+. In mice, all the EpCAM+ cells were immunoreactive to pan-cytokeratin, as determined by IF microscopy. Results were confirmed using Krt1-14;mTmG transgenic mice, with low (8.6 native GFP+ cells per 106 cells analyzed; 0.085% of viable cells), but significant numbers (p < 0.0005) of GFP+ cells present in normal murine BM, that were not the result of randomness compared with multiple negative controls. Further, EpCAM+ cells in mouse blood were more heterogeneous than CD45+ cells (0.58% in BM; 0.13% in blood). These observations conclude that cells expressing cytokeratin proteins are reproducibly detectable among mononuclear cells from human and murine blood and BM. We demonstrate a method of tissue harvesting, flow cytometry, and immunostaining that can be used to identify and determine the function of these pan-cytokeratin epithelial cells in healthy individuals.

Comprehensive Transcriptomic Analysis of VISTA in Acute Myeloid Leukemia: Insights into Its Prognostic Value.

The V-domain Ig suppressor of T-cell activation (VISTA) has been recognized as a critical negative regulator of antitumor immune response and is gaining growing interest as a potential pharmacological target in immunotherapy. This molecule is highly expressed in hematopoietic stem cells and myeloid compartment, and it has been found upmodulated in acute myeloid leukemia (AML). However, VISTA-associated immune features are relatively unexplored in myeloid malignancies. Herein, we aimed to explore whether this immune checkpoint regulator could play a role in the generation of an immune escape environment in AML patients. We characterized VISTA mRNA expression levels in leukemia cell lines and in large publicly available cohorts of specimens from bone marrow of healthy individuals and AML patients at diagnosis by deploying bulk and single-cell RNA sequencing. We also defined the correlations with leukemia-associated burden using results of whole-exome sequencing of AML samples at disease onset. We showed that VISTA expression linearly increased across the myeloid differentiation tree in normal hematopoiesis. Accordingly, its transcript was highly enriched in AML cell lines as well as in AML patients at diagnosis presenting with myelomonocytic and monocytic differentiation. A strong correlation was seen with NPM1 mutations regardless of the presence of FLT3 lesions. Furthermore, VISTA expression levels at baseline correlated with disease recurrence in patients with normal karyotype and NPM1 mutations, a subgroup traditionally considered as favorable according to current diagnostic schemes. Indeed, when compared to patients with long-term remission (&gt;5 years after standard chemotherapy regimens), cases relapsing within 2 years from diagnosis had increased VISTA expression in both leukemia and T cells. Our results suggest a rationale for developing VISTA-targeted therapeutic strategies to treat molecularly defined subgroups of AML patients to prevent disease recurrence and treatment resistance.

Analysis of COVID-19-Associated Proteins Identifies TANK-Binding Kinase 1 As an Immunotherapeutic Target in Multiple Myeloma

Background and Rationale. Patients with multiple myeloma (MM) are at a higher risk of viral infection due to immune deficiency, as recently highlighted by the severity of COVID-19 in MM patients. However, the mechanism(s) underlying the lack of anti-viral immune response in MM are unclear. We have previously shown that there are more plasmacytoid dendritic cells (pDCs) in the bone marrow of MM patients than in the bone marrow of healthy individuals and that these dysfunctional patient pDCs suppress T and NK cell-mediated immunity. Importantly, pDCs play a key role in both recognizing viral nucleic acid and initiating anti-viral immunity via type 1 interferon (IFN) response signaling. Therefore, we analyzed the immune-pathway proteins implicated in COVID-19-host interactions [COVID-19 protein interaction map, Gordon et al, Nature 2020; 583, 459-568] to assess whether pDC-MM interactions modulate these pathways to confer immune suppression and susceptibility to COVID-19. Results. We first assessed whether the expression of human genes involved in the COVID-19-host interaction changes when ex vivo MM cells are co-cultured with patient pDCs (compared to MM cells alone). We found that 41 of these genes were differentially expressed in MM cells when exposed to pDCs (log2Fold change: ± 3.5-fold; p < 0.00001), and this expression varied widely (median (log10): -0.13 to 4.5; adj p < 0.001). Three of these genes are linked to innate immunity and are essential for IFN production in MM cells - TBK1, IRF3 (Interferon regulatory factor 3), and RAE1 (interferon-inducible mRNA nuclear export factor). Importantly, pDCs downregulated the expression of TBK1 (Log2FC: -0.5) and RAE1 (Log2FC: -0.3) and upregulated the expression of IRF3 (Log2FC: 1.5) in MM cells after coculture (compared to MM cells alone, p < 0.0001). Concordantly, analysis of publicly available gene profiling datasets on relapsed MM patients showed low levels of TBK1 and RAE1 and higher levels of IRF3 (n = 50) (Log2FC: TBK1: -0.208; RAE1: -0.286; IRF3: 0.273; vs normal; p < 0.05). Of note, TBK1 expression was positively correlated with prognosis (n = 350, p = 0.026). We found that most of the 41 genes were also expressed in pDCs (NCBI GEO Datasets based on pDC cell line CAL1 and human peripheral blood pDCs). In unstimulated pDCs, TBK1 expression was significantly lower than IRF3 and RAE1 expression (2-3-fold, p < 0.05). Yet treating pDCs with CpG-ODN type-A, which induces IFN-α expression, increased both TBK1 (adj P = 0.004) and RAE1 (adj P = 0.043) expression, without significantly altering IRF3 expression. Finally, COVID-19 relies on the host ubiquitin-proteasome system for propagation, and we found that targeting ubiquitin receptor Rpn13 with the specific inhibitor RA190 restored TBK1 expression in MM cell lines, indicating the potential clinical use of targeting Rpn13 in restoring anti-viral immune responses in MM. Conclusion. Taken together, we show that TBK1 is downregulated in pDCs, and pDCs interacting with MM cells further decrease TBK1 expression in MM cells, thereby attenuating IFN-mediated anti-viral immune response signaling. Our findings suggest that: 1) low levels of TBK1 may confer increased susceptibility of MM patients to COVID-19 and 2) targeting TBK1 may restore the anti-viral immune response and reduce COVID-19 severity in MM.

Comprehensive phenotyping of erythropoiesis in human bone marrow: Evaluation of normal and ineffective erythropoiesis.

Identification of stage-specific erythroid cells is critical for studies of normal and disordered human erythropoiesis. While immunophenotypic strategies have previously been developed to identify cells at each stage of terminal erythroid differentiation, erythroid progenitors are currently defined very broadly. Refined strategies to identify and characterize BFU-E and CFU-E subsets are critically needed. To address this unmet need, a flow cytometry-based technique was developed that combines the established surface markers CD34 and CD36 with CD117, CD71, and CD105. This combination allowed for the separation of erythroid progenitor cells into four discrete populations along a continuum of progressive maturation, with increasing cell size and decreasing nuclear/cytoplasmic ratio, proliferative capacity and stem cell factor responsiveness. This strategy was validated in uncultured, primary erythroid cells isolated from bone marrow of healthy individuals. Functional colony assays of these progenitor populations revealed enrichment of BFU-E only in the earliest population, transitioning to cells yielding BFU-E and CFU-E, then CFU-E only. Utilizing CD34/CD105 and GPA/CD105 profiles, all four progenitor stages and all five stages of terminal erythroid differentiation could be identified. Applying this immunophenotyping strategy to primary bone marrow cells from patients with myelodysplastic syndrome, identified defects in erythroid progenitors and in terminal erythroid differentiation. This novel immunophenotyping technique will be a valuable tool for studies of normal and perturbed human erythropoiesis. It will allow for the discovery of stage-specific molecular and functional insights into normal erythropoiesis as well as for identification and characterization of stage-specific defects in inherited and acquired disorders of erythropoiesis.

Chemokine SDF1 Mediated Bone Regeneration Using Biodegradable Poly(D,L-lactide-co-glycolide) 3D Scaffolds and Bone Marrow-Derived Mesenchymal Stem Cells: Implication for the Development of an "Off-the-Shelf" Pharmacologically Active Construct.

There is an increasing need for bone substitutes for reconstructive orthopedic surgery following removal of bone tumors. Despite the advances in bone regeneration, the use of autologous mesenchymal stem cells (MSC) presents a significant challenge, particularly for the treatment of large bone defects in cancer patients. This study aims at developing new chemokine-based technology to generate biodegradable scaffolds that bind pharmacologically active proteins for regeneration/repair of target injured tissues in patients. Primary MSC were cultured from the uninvolved bone marrow (BM) of cancer patients and further characterized for "stemness". Their ability to differentiate into an osteogenic lineage was studied in 2D cultures as well as on 3D macroporous PLGA scaffolds incorporated with biomacromolecules bFGF and homing factor chemokine stromal-cell derived factor-1 (SDF1). MSC from the uninvolved BM of cancer patients exhibited properties similar to that reported for MSC from BM of healthy individuals. Macroporous PLGA discs were prepared and characterized for pore size, architecture, functional groups, thermostability, and cytocompatibility by ESEM, FTIR, DSC, and CCK-8 dye proliferation assay, respectively. It was observed that the MSC+PLGA+bFGF+SDF1 construct cultured for 14 days supported significant cell growth, osteo-lineage differentiation with increased osteocalcin expression, alkaline phosphatase secretion, calcium mineralization, bone volume, and soluble IL6 compared to unseeded PLGA and PLGA+MSC, as analyzed by confocal microscopy, biochemistry, ESEM, microCT imaging, flow cytometry, and EDS. Thus, chemotactic biomacromolecule SDF1-guided tissue repair/regeneration ability of MSC from cancer patients opens up the avenues for development of "off-the-shelf" pharmacologically active construct for optimal repair of the target injured tissue in postsurgery cancer patients, bone defects, damaged bladder tissue, and radiation-induced skin/mucosal lesions.

Abstract 3311: B cell like neutrophil found in peripheral blood of melanoma patients

Abstract An expansion of neutrophils often marks cancer. To date, neutrophils are assumed to be a relatively homogenous population, but recent studies describe both pro- and anti-tumor functions in neutrophils. This suggests there is more heterogeneity in neutrophils than previously appreciated. To better understand and target neutrophil functions in cancer, we must dissect neutrophil heterogeneity and how it changes from health to disease. To this end, we employed single-cell transcriptome technology to profile immature neutrophils from bone marrow of healthy individuals. Intriguingly, we identified a new neutrophil subset that expresses several B cell markers, including CD79a/b, components of the B cell receptors and PAX5, a lineage-specific transcriptional factor. We termed this population the BNeut. Using flow cytometry, we found that BNeuts are confined to the bone marrow of healthy individuals but expand into the blood of melanoma patients at an early stage, suggesting BNeuts might be a biomarker for disease. Additionally, we find BNeuts in the mouse models of different cancer types, including breast and lung carcinoma. The BNeut appears and functions more similar to a neutrophil than a B cell. BNeuts possess a neutrophil-like transcriptional profile, large cytoplasm with segmented nucleus, and produce ROS and NETs. Using imaging, we show that the BNeuts are single cells co-expressing both CD66b and CD79b, and lack the B cell surface marker CD19. To understand why neutrophils might use a B cell program, we explored different B cell functions including antigen presentation, a function that is usually absent from neutrophils. We show BNeuts are excellent at phagocytosis, including uptake of tumor cells. Further, BNeuts have increased expression of antigen presentation-related genes compared to other neutrophils and can modulate CD4+ T cell responses. Together, we have identified a novel neutrophil subset expressing B cell markers that is preferentially expanded in the blood of melanoma patients and poised to control T cell responses during disease. Citation Format: Melissa A. Meyer, Huy Q. Dinh, Yanfang Zhu, Shu Liang, Gregory Seumois, Pandurangan Vijayanand, Sergio D. Catz, Catherine C. Hedrick. B cell like neutrophil found in peripheral blood of melanoma patients [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3311.

A GPI-Anchored Protein, CD109, Protects Hematopoietic Progenitor Cells from Erythroid Differentiation Induced By TGF-β

[Background] Glycosylphosphatidylinositol-anchored proteins (GPI-APs) on hematopoietic stem progenitor cells (HSPCs) may have some roles in the negative regulation of the HSPC commitment induced by inflammatory cytokines given the fact that progenies of GPI(-) HSPC are often detected in patients with immune-mediated bone marrow (BM) failure. CD109, one of the GPI-APs expressed by keratinocytes and HSPCs in humans, serves as a TGF-β co-receptor and is reported to inhibit TGF-β signaling in keratinocytes; however, the role of CD109 on HSPCs remains unknown. We previously demonstrated that TGF-β induced erythroid differentiation of TF-1 cells, a myeloid leukemia cell line that expresses CD109, in a dose-dependent manner and that knockout of the CD109 gene resulted in erythroid differentiation of TF-1 cells cultured in fetal bovine serum-containing medium, suggesting an inhibitory role of CD109 in the erythroid differentiation of HSPCs induced by low levels of TGF-β (Blood, 2018. 132 (Suppl.1) :3874). However, as most CD109 KO TF-1 cells changed into erythroid cells, they were unsuitable for investigating the role of CD109 in the erythroid differentiation induced by TGF-β. To overcome this issue, we prepared TF-1 cells and cord blood (CB) HSPCs in which the CD109 expression was transiently downregulated, and attempted to further clarify the role of CD109. [Methods] TF-1 cells and CD34+ cells isolated from CB mononuclear cells were treated with siRNA that was complementary to CD109 mRNA. CD109 knockdown cells were cultured for 4 days in serum-free medium supplemented with stem cell factor, thrombopoietin, and erythropoietin with or without TGF-β. In separate experiments, TF-1 cells were treated with phosphatidylinositol-specific phospholipase C (PIPL-C) treatment for 1 hour and were incubated in the presence or absence of TGF-β. CD109 KO TF-1 cells were incubated in serum-free medium (StemPro-34 SFM) for 14 days and their phenotype was determined using flow cytometry (FCM). The erythroid differentiation of the cells was assessed by testing the expression of glycophorin A (GPA) and iron staining. [Results] The down-regulation of CD109 in TF-1 cells by the siRNA treatment increased GPA expression in response to 12 ng/ml of TGF-β from 1.77% to 35.6%. The transient depletion of GPI-APs by PIPL-C also augmented the GPA expression induced by TGF-β from 1.27% to 6.77%. In both BM of healthy individuals and CB, CD109 was more abundantly expressed in Lin-CD34+CD38-CD90+CD45RA- hematopoietic stem cells (HSCs) than in Lin-CD34+CD38-CD90-CD45RA- multipotent progenitors (MPPs) and Lin-CD34+CD38+ HSPCs (Fig. 1). The treatment of CB cells with siRNA reduced the CD109 expression in Lin-CD34+CD38+ cells from 55.9% to 23.1%. TGF-β induced the expression of GPA in Lin-CD34+CD38+CD123-CD45RA- megakaryocyte-erythrocyte progenitor cells (MEPs) of CD109 knockdown cells to a greater degree than the control counterpart (Fig. 2). During 14-day serum-free culture, GPA-positive CD109 KO TF-1 cells died, and similarly to WT TF-1 cells, most surviving CD109 KO TF-1 cells were GPA-negative. TGF-β treatment induced erythroid differentiation in CD109 KO TF-1 cells to a greater degree than in WT TF-1 cells. [Conclusions] CD109 plays a key role in the inhibition of TF-1 erythroid differentiation in response to TGF-β. CD109 may suppress TGF-β signaling, and the lack of CD109 may make PIGA-mutated HSPCs more sensitive to TGF-β, thus leading to the preferential commitment of the mutant erythroid progenitor cells to mature red blood cells in immune-mediated BM failure. Disclosures Yamazaki: Novartis Pharma K.K.: Honoraria; Sanofi K.K.: Honoraria; Nippon Shinyaku Co., Ltd.: Honoraria. Nakao:Novartis Pharma K.K: Honoraria; Bristol-Myers Squibb: Honoraria; Takeda Pharmaceutical Company Limited: Honoraria; Celgene: Honoraria; Ono Pharmaceutical: Honoraria; Chugai Pharmaceutical Co.,Ltd: Honoraria; Kyowa Kirin: Honoraria; Alaxion Pharmaceuticals: Honoraria; Ohtsuka Pharmaceutical: Honoraria; Daiichi-Sankyo Company, Limited: Honoraria; Janssen Pharmaceutical K.K.: Honoraria; SynBio Pharmaceuticals: Consultancy.

The Depletion of TGF-β Co-Receptor CD109 Induces Erythroid Differentiation of TF-1 Cells: A Model of Preferential Commitment of PIGA-Mutated Hematopoietic Stem Cells in Immune-Mediated Bone Marrow Failure

[Background] Glycosylphosphatidylinositol-anchored proteins (GPI-APs) on hematopoietic stem progenitor cells (HSPCs) may play an important role in the regulation of the HSPC commitment, given the fact that a lack of GPI-APs due to PIGA mutations allows HSPCs to preferentially undergo commitment into mature blood cells under immune pressure against HSPCs in patients with acquired aplastic anemia. CD109, one of the GPI-APs expressed by keratinocytes and HSPCs in humans, serves as a TGF-β co-receptor and is reported to inhibit TGF-β signaling in keratinocytes; however, the role of CD109 on HSPCs has not been clarified. TF-1 is one of a few myeloid leukemia cell lines that express CD109, the proliferation of which is dependent on GM-CSF. Since TF-1 undergoes erythroid differentiation in response to δ-5-aminolevulinic acid (δ-ALA), and its differentiation is reportedly inhibited by TGF-β, a lack of GPI-APs due to PIGA mutation and/or the knockout (KO) of CD109 may affect the differentiation of TF-1 cells. [Objectives/Methods] To gain insights into the role of GPI-APs on HSPCs, we established a PIGA-mutated TF-1 cell line by culturing TF-1 in the presence of α-toxin for several months, and a CD109 KO TF-1 cell line using a CRISPR-Cas 9 system. The erythroid differentiation of the cells was assessed by testing the expression of glycophorin A (GPA) on TF-1 cells using flow cytometry (FCM) and iron staining. We also determined the CD109 expression by HSPCs from healthy individuals and C57BL/6 mice using FCM and a quantitative PCR. [Results] Both GPI-AP-deficient TF-1 cells that had a PIGA mutation (7 nucleotide deletion at position 291-297 [TTGTCAC] in exon 2) and CD109 KO TF-1 cells showed slower proliferation than wild-type (WT) TF-1 cells. Similarly to TF-1 cells treated with δ-ALA, both mutant cells expressed GPA, exhibited erythroid morphology, and were positive for iron granules, suggesting that GPI-APs inhibited the erythroid differentiation of WT TF-1 cells that were cultured in RPMI1640 containing 10% fetal bovine serum (FBS), and that the GPI-AP that plays a key role in the inhibition of erythroid differentiation is CD109. Since low levels (1-2 ng/ml) of TGF-β in the serum-containing culture medium were suspected to inhibit the erythroid differentiation of WT TF-1 through its binding to CD109, WT TF-1 cells were cultured in a serum-free medium Expi293 Expression Medium for 10 days. While control TF-1 cells cultured in the serum-containing RPMI1640 were negative for the expression of GPA, 77.0-84.5% of the cultured TF-1 cells expressed GPA and exhibited erythroid morphology. CD109 was expressed by 12.1-18.3% of CD34+CD38- cells, 4.5-7.4% of common myeloid progenitor cells (CMPs), 20.8-42.4% of megakaryocyte-erythrocyte progenitor cells (MEPs), and 14.2-22.0% of granulocyte macrophage progenitor cells (GMPs) in the bone marrow of healthy individuals, while murine CD48-CD150+CD34- LSK cells were negative for either CD109 protein or mRNA. [Conclusions] CD109 protects TF-1 cells from differentiating into erythroid cells in serum-containing culture. In contrast to keratinocytes, the CD109 on TF-1 cells, and possibly on HSPCs, may enhance TGF-β signaling, and the lack of the GPI-AP might make PIGA-mutated HSPCs insensitive to TGF-β, leading to the preferential commitment of mutant HSPCs to mature blood cells in immune-mediated bone marrow failure. [Display omitted] DisclosuresNakao:Kyowa Hakko Kirin Co., Ltd.: Honoraria; Novartis: Honoraria; Alexion Pharmaceuticals, Inc.: Consultancy, Honoraria.

Minimal Residual Disease (MRD) Analysis Using Multiparametric Flow Cytometry (MFC) and Identification of Differences in Subpopulations Using Next Generation Sequencing (NGS) in the Bone Marrow (BM) of Multiple Myeloma (MM) Patients (pts)

Introduction: MM is characterized by the accumulation of aberrant BM plasma cells (aPCs). The use of novel agents for anti-MM treatment has enabled the achievement of deeper responses and prolonged progression free survival (PFS) and overall survival (OS). These advances have created the need for sensitive means to detect residual PCs. MFC allows aPC detection with high sensitivity and is used with NGS in clinical trials (CTs) (Paiva, 2015-2018). It allows the detection of residual cells after anti-MM therapies and is a risk denominator of pt subgroups and post-therapeutic outcome. The incorporation of cost-effective, readily available and standardized MRD tools into CTs and clinical practice seems a key requisite. It may allow the improvement of clinical decisions: 1) timing of stem cell transplantation (SCT), 2) need for consolidation, 3) duration of maintenance, 4) therapy modulations and 5) early relapse detection. Since MRD gains importance for novel agents' potency to achieve MRD negativity, including FDA/EMA-approvals, we assessed MFC for detection of aPCs, their change to treatment and over time.Methods: We systematically validated a 6-, 8- and 10-color panel using CD38, CD138, CD19, CD45, CD27, CD56, CD28, CD81, CD117, CD200 and kappa/lambda (k/l) in 9 different MM cell lines (MMCLs) and 213 BM, PB, leukapheresis (LA), extramedullary (EM) samples of 122 different MM pts and 14 healthy individuals (HI). These were immediately analyzed after sampling, using a bulk-lysis protocol. To reach a high sensitivity, >3x106 viable nucleated cells were analyzed. MFC validation included fluorescence-minus-one-(FMO), isotype- and spike-in-controls to evaluate the reliability and sensitivity of our panels. Spike-in controls were performed using a dilution assay to recover defined MMCL cells in the PB of HI. Data analysis was accomplished using the BeckmanCoulter software Kaluza®. We compared MFC using BM and PB samples of HI, MM pts at initial diagnosis (ID) or with progression (PD), after standard therapy (ST) and SCT. Additionally, BM samples at ID were sorted into each 4 aPC- and normal PC- (nPC) subpopulations for DNA and RNA sequencing and follow-up. The study was performed with written consent of all pts and HIs and approval of the ethics committee.Results: The antigen expression levels in 9 MMCLs using our 6-, 8- and 10-color panel could be confirmed as reported. The expression levels of antigens included in all panels were similar in all MMCLs (RPMI 8226; U266; IM-9; MM1.S; MM1.R; L363; Karpas620; NCI-H929; OPM-2). For all panels, we established easy to adapt gating strategies, using commercially available software to identify aPCs vs. nPCs in all analyzed samples. Using the 6-color panel, differentiation into up to 4 phenotypic subpopulations of aPCs and nPCs in MM pts and up to 4 subpopulations of nPCs in HI was achieved, depending on the heterogeneous phenotype the individual was expressing. Moreover, both DNA and RNA of obtained subpopulations were collected and analyzed via sequencing. Since in 1% of our samples, aPCs remained undetected via 6-color panel using surface antigens exclusively, we added k/l and did detect aPCs in all pts. The 10-color panel identified aPC- and nPC-subpopulations in even more detail. We determined a MRD sensitivity of 10-5, confirmed via independent dilution assays. In 48% of BM and PB samples, aPCs were determined at ID and PD; 52% were assessed for MRD after ST and SCT. Of the latter, 55% were BM samples, of which 5% showed MRD negativity of <0.001%. The median time from ST- or SCT-treatment to 1rst MRD evaluation was 44 days; this being assessed at subsequent time points currently. These data will be shown at the meeting.Conclusion: Our 6-, 8-, and 10-color panels allow highly sensitive detection of aPCs vs. nPCs in MM samples. These panels have been validated using various controls, dilution assays, 9 MMCLs, MM pt samples and HI and can be implemented into routine diagnostics. The analysis of DNA and RNA expression patterns in distinct subpopulations will generate relevant insight, which subclones contribute to response vs. resistance mechanisms. The EuroFlow Consortium have established a two 8-color tubes test for identification of aPCs, which - albeit used worldwide - may not be applicable for every center and every pt outside CTs. Therefore, meticulously validated alternatives as shown here are of interest. Our 8-color panel has been included into our CT portfolio. DisclosuresAzab:Cellatrix LLC: Equity Ownership, Other: Founder and owner; Targeted Therapeutics LLC: Equity Ownership, Other: Founder and owner; Ach Oncology: Research Funding; Glycomimetics: Research Funding. Zeiser:Jazz Pharmaceuticals: Research Funding. Wäsch:Pfizer: Honoraria.

Bacterial profiling of healthy bone marrow using polymerase chain reaction technique

Background: The bone marrow of healthy individuals is conventionally considered sterile like other body fluids, but recently the scientists found genetic material from the bacteria inside their stem cells. The findings raise the possibility that other infectious agents may also reside in the bone marrow. Objectives: The study was planned to look for the presence of all type of bacteria by amplifying 16S rDNA sequences using eubacterial universal primers. Materials and Methods: A total of 18 bone marrow samples of apparently healthy individuals were collected from patients admitted having closed bone fractures. The DNA was isolated and was subjected to nested polymerase chain reaction (PCR) using Universal eubacterial 16S rDNA primers. The samples positive by universal PCR was further checked for the presence of Salmonella Typhi, Salmonella Paratyphi A, and/or Mycobacterium tuberculosis (Mtb) if any using a second nested PCR reaction. Results: A total of 16 (89%) samples could yield the desired amplicon through universal PCR. The secondary PCR of 16 samples, the desired amplicons were detected 3 (18.8%) for Mtb, 4 (25%) for S. Typhi, and 1 (6.2%) for S. Paratyphi A. Conclusions: Even in asymptomatic cases, other infectious agents such as Mtb, Salmonella spp., and many other microorganisms may be present as commensal.

Deregulated Genes in Hematopoietic Stem Cells Isolated from Spleen of Patients with Myelofibrosis

An important issue in myeloproliferative diseases research is to test the hypothesis that in the neo-angiogenesis, which is observed in the spleen and bone marrow of patients, involves endothelial cells derived from the neoplastic clone. In this study we analyzed the gene expression profile of 138 genes in CD34+ hematopoietic cells from the spleen and peripheral blood of patients with myelofibrosis (MF) and healthy individuals (HI). These genes have been selected among those that characterize the neoangiogenic gene signature or belonging to deregulated expression pathways in MF, and are listed in Table1.By using quantitative reverse transcription-PCR (RT-qPCR), we measured the expression levels of 141 targets and 5 reference genes in CD34+ cells isolated by immunomagnetic method from the spleen and peripheral blood of 4 patients and 3 HI. For calculation of the statistical significance of the differences we used the t-test for unpaired samples. A p<0.05 was considered to be statistically significant. All data analyses were performed with GenEx (version 6.1, MultiD).To characterize the differentially expressed genes obtained in each comparison, the lists of genes were analyzed through several tools, i.e. String, Enrichr and GSEA analysis. The comparison between spleen CD34+ cells and circulating CD34+ cells reveal a group of common genes in both patients and heathy donors. Those genes are significantly overexpressed in spleen. Some of the common genes are involved in the regulation of cell migration and in the development of blood vessels were significantly overexpressed in splenic CD34+ cells compared to circulating CD34+ cells. However, we observed that many of the genes implicated in the development of the vessels were under-expressed in CD34+ cells isolated from the spleen of patients compared to those of HI. The most significant upregulated genes in CD34+ splenic cells from patients included transcripts (GATA1, HBB, TAL1, GATA2, PTGS1) belonging to the molecular signature of CD34+ cells isolated from the bone marrow (BM) of patients with chronic myeloid leukemia (Diaz-Blanco E. et al., Leukemia 2007). Another group of upregulated genes (GATA1, TAL1, ITGB3, GATA2, PF4) are also identified in a study designed to characterize the genes essential to the development of megakaryocytes (Tenedini et al. Blood 2004). These two groups of genes are part of an expression pattern characteristic for immature stem cells as well as megakaryocyte-erythrocyte progenitor cells. Another group of genes overexpressed in patients spleens (CD34, ANGPT1, PF4, GATA2, PTGS1), which includes some of the above mentioned genes, has been observed in a comparison between circulating CD34+ cells from patients with myelofibrosis, and CD34 + cells isolated from the bone marrow of HI (Guglielmelli P. et al. Stem Cells 2007). Among the underexpressed genes in the spleen of patients we mention CXCR4, in keeping with previous observations. Interestingly, among the aforementioned genes, GATA1 and GATA2 genes are overexpressed in granulocytes of patients with MPNs regardless of the JAK2/CALR mutational status whereas PTGS1 is overexpressed in the JAK2-V617F homozygous and CALR-mutated granulocytes (Rampal et al. Blood 2014).We focused our attention on PTGS1 because its well-known activity in regulating angiogenesis, which can be inhibited in vitro by treatment with aspirin (Tsujii, M. et al. Cell 1998). To explain the mechanism of action of low-doses aspirin in this context, it has been proposed a model that involves permanent inactivation of PTGS1 in platelets. Indeed, PTGS1 is the only cyclooxygenase isoenzyme present in platelets. Moreover, Dixon and colleagues (Dixon, D.A. et al. JCI 2006), demonstrated that activated platelets induced the expression of PTGS2 in monocytes. It is believed that the synthesis of prostaglandin E2 by PTGS2 in tissues, is linked to an increment of angiogenesis and cell proliferation, and to a reduction of apoptosis. According to this concept, our data point toward a model in which, in the spleen of patients with MF, an altered hematopoietic stem cell differentiation could induce an inflammation-mediated angiogenesis through the overexpression of PTGS1 and a consequent induction of PTGS2 in cells of the splenic microenvironment. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Epigenetic Priming Confers Direct Cell Trans-Differentiation From Adipocyte to Osteoblast in a Transgene-Free State

The bone marrow of healthy individuals is primarily composed of osteoblasts and hematopoietic cells, while that of osteoporosis patients has a larger portion of adipocytes. There is evidence that the epigenetic landscape can strongly influence cell differentiation. We have shown that it is possible to direct the trans-differentiation of adipocytes to osteoblasts by modifying the epigenetic landscape with a DNA methyltransferase inhibitor (DNMTi), 5'-aza-dC, followed by Wnt3a treatment to signal osteogenesis. Treating 3T3-L1 adipocytes with 5'-aza-dC induced demethylation in the hypermethylated CpG regions of bone marker genes; subsequent Wnt3a treatment drove the cells to osteogenic differentiation. When old mice with predominantly adipose marrow were treated with both 5'-aza-dC and Wnt3a, decreased fatty tissue and increased bone volume were observed. Together, our results indicate that epigenetic modification permits direct programming of adipocytes into osteoblasts in a mouse model of osteoporosis, suggesting that this approach could be useful in bone tissue-engineering applications.

Abstract 5020: Neutrophils in the bone marrow niche promote multiple myeloma chemoresistance

Abstract Purpose: The bone marrow (BM) niche provides a sanctuary for multiple myeloma (MM) cells, allowing them to escape chemotherapy. Previous in vitro studies have implicated some BM cell populations, including stromal cells, macrophages, osteoclasts and plasmacytoid dendritic cells, in MM chemoresistance. However, the role of the major cellular component of BM represented by immature and mature neutrophils (polymorphonuclear cells, PMNs) in MM survival from chemotherapy remains unknown. We therefore evaluated the role of PMNs in MM cell chemoresistance within the BM niche. Methods: We employed in vivo mouse models to modulate the number of myeloid cells in the BM of MM-bearing mice. To deplete CD11b+ myeloid cells, we generated CD11b-DTR BM chimeras and injected diphtheria toxin (DT) or a control toxin every 4 days after MM cell injection. To expand CD11b+ cells we overexpressed GM-CSF by hydrodynamic transfection of a GM-CSF expression plasmid 2 days before MM cell injection. Mice were then treated with doxorubicin or vehicle control and their survival was evaluated. For in vitro studies, Gr-1+CD11b+ mouse PMNs and PMN-myeloid derived suppressor cells (PMN-MDSCs) were isolated from the BM of tumor-free or MM-bearing mice respectively. CD33+CD14-CD11b+ human PMNs and PMN-MDSCs were FACS sorted from the BM of healthy individuals or MM patients, respectively. Results: Depletion of myeloid CD11b-expressing cells led to a significant reduction of MM tumor growth in these mice and improved antitumor effect of doxorubicin. Conversely, GM-CSF-induced expansion of myeloid cells in the BM of MM-bearing mice resulted in reduced survival and increased resistance to chemotherapy. Both mouse and human PMNs and PMN-MDSCs were able to protect mouse and human MM cells, respectively, from doxorubicin and melphalan-induced apoptosis in vitro. The addition of supernatant collected from these myeloid cells to MM cells was sufficient to provide tumor cell chemoprotection. In vitro, mouse MM cells induced PMNs to release DNA in the form of neutrophil extracellular traps (NETs). These NETs were efficiently taken up by tumor cells and contributed to PMN-induced chemoresistance in vitro, as addition of DNAse I cancelled this effect. No other myeloid cells, stromal cells or MM tumor cells were able to release DNA. In vivo, we observed a significant increase in circulating cell-free DNA in the blood plasma and BM plasma of MM-bearing mice, and in the BM plasma of MM patients compared to healthy individuals. Coculture of MM cells with PMNs or PMN-derived DNA induced the expression of the survival factor sXBP-1. Knockdown of sXBP-1 was sufficient to block the chemoprotective effect of DNA on MM cells. Conclusion: Our data demonstrate that PMNs contribute to MM chemoresistance by releasing their DNA, resulting in induction of sXBP-1 in tumor cells. Thus, targeting cell free DNA or sXBP-1 induction in conjunction with chemotherapy is a promising strategy for overcoming MM chemoresistance. Citation Format: Indu Ramachandran, Cindy Lin, Thomas Condamine, Maria Ozerova, Alfred Garfall, Dan Vogl, Dmitry Gabrilovich, Yulia Nefedova. Neutrophils in the bone marrow niche promote multiple myeloma chemoresistance. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5020. doi:10.1158/1538-7445.AM2015-5020

Recovery of the Normal B-Cell Compartment in Children Treated for B-Cell Precursor Acute Lymphoblastic Leukemia

BACKGROUNDCytotoxic treatment in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) patients induces a dramatic decrease in B-cell precursor (BCP) and mature B-cell numbers, followed by regeneration of BCPs in the bone marrow (BM) and subsequent replenishment of mature B-cells in the peripheral blood (PB) in between treatment blocks and after stop of treatment. To understand the degree of B-cell recovery after such dramatic changes, we first evaluated the composition of the B-cell population in the BM and PB of pediatric BCP-ALL patients during and after therapy. Secondly, we investigated whether the immunophenotypic maturation of BCPs in regenerating BM is similar to normal BCP development or whether such regeneration induces immunophenotypic aberrancies, which could potentially hamper minimal residual disease (MRD) detection. Finally, we assessed whether compensatory proliferation plays a role during B-cell regeneration, since enhanced proliferation might limit the B-cell receptor diversity and consequently may affect susceptibility to infections during and after therapy.METHODSFor immunophenotypic characterization of different B-cell subsets, 8-color flow cytometry was performed on fresh BM and PB samples at different time points after start of therapy (DCOG ALL11-protocol). To study BCP maturation, a multidimensional maturation pathway based on 5 backbone markers was designed and the expression pattern of several differentiation markers during this maturation pathway was evaluated. To assess proliferation in BCP subsets, BM samples were stained with subset-specific antibodies and DRAQ5 for cell cycle analysis. The proliferation history of sorted pre-B-II-small and immature subsets in BM and sorted mature B-cell subsets in PB was assessed by performing a kappa-deleting recombination excision circle (KREC)-assay.RESULTSBCP regeneration occurred mainly at day 78, month 5 and after stop of therapy. The BCP compartment in regenerating BM at time points during therapy showed a shift towards the most immature stages. In PB, mature B-cell numbers decreased after start of therapy and newly generated mature B-cells subsets reappeared at month 5 and after stop of therapy.Importantly, the BCP maturation pathway with its expression patterns of CD10, CD34, CD58, CD66c, CD38, CD123, CD9, CD81, CD24, TdT, Igκ and Igλ was comparable between regenerating BM and BM of healthy individuals, albeit that a shift in the relative BCP subset distribution was observed in regenerating BM.As expected, most proliferation in BM of healthy controls occurred in the pre-B-II-large subset (68% ±11% (mean ±SD) proliferating cells). Comparable percentages of proliferating pre-B-II-large cells were found in regenerating BM: 74%±10% at day 78, 72%±10% at month 5 and 63% (preliminary data, n=1) at one year after stop of therapy (month 36). Also pre-B-I cells showed some proliferation, with no significant differences between normal and regenerating BM (Figure 1). If present, the pre-B-II-small and immature BCP subsets showed no proliferation in regenerating and normal BM. KREC-analysis of sorted pre-B-II-small and immature subsets confirmed that no cell divisions had occurred after IGK-rearrangement in normal BM as well as regenerating BM at month 5 and month 36. Low numbers of pre-B-II-small and immature cells precluded KREC-analysis at day 78.KREC-analysis of the various mature B-cell subsets in PB showed no significant difference in proliferation history between PB of patients at different time points during or after therapy and PB of healthy controls.CONCLUSIONSIn BCP-ALL patients, the B-cell compartment is drastically affected during treatment. Subsequent regeneration of BCPs and mature B-cells occurs at different time points during therapy and after stop of therapy. Immunophenotypically, BCP maturation in regenerating BM is similar to normal B-cell differentiation, indicating that MRD detection will not be hampered by aberrant immunophenotypes of regenerating BCPs. Importantly, no enhanced proliferation is observed in BCP subsets in BM and mature B-cells subsets in PB of patients during and after therapy. The lack of compensatory proliferation suggests that B-cell regeneration is due to a larger influx of non-committed stem cells into the B-cell lineage and indicates that a diverse immune repertoire will most likely be restored during recovery of the B-cell compartment. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Chemosensitizing Leukemia By Targeting the Leukemia Microenvironment with Vascular Disrupting Combretastatins

Background: Refractory disease is the greatest challenge in treating leukemia. We recently discovered that blood vessels serve as a protective sanctuary for acute myeloid leukemia (AML) and developed a novel combretastatin, OXi4503, to disrupt this vascular niche. We translated our findings into a phase I clinical study for patients with refractory AML (ClinicalTrials.gov NCT01085656). An interim analysis of this trial suggested that optimal treatment of AML will likely require more than a single microenvironment targeting agent. Other AML trials, such as those with single agent sunitinib, bevacizumab, or pazopanib also support this concept. Therefore, we examined the effects of combining microenvironment targeting agents with cytotoxic chemotherapy.Methods: Bone marrow endothelial cells (BMECs) were isolated from bone marrow of healthy individuals. In vitro co-cultures of human AML (KG1) and BMECs were used to examine various treatments with cytarabine (Ara-C), azacitidine, and vascular disrupting combretastatins (CA1 and CA4). Cell death was analyzed by PI staining and flow cytometry. Cell cycle distribution was analyzed using 7-AADand BrdU staining. Given that combretastatins bind reversibly to B-tubulin, immunostaining of treated cells was performed using antibodies to B-tubulin and VCAM-1 and analyzed by fluorescence microscopy. Finally, the drug combinations with optimal in vitro effects were then tested in vivo using a xenograft model of human AML.Results: Co-culturing AML cells with BMECs afforded the leukemia cells a protective survival advantage despite treatments with Ara-C or azacitidine, further supporting the evolving understanding that leukemia cells located in or near the vascular niche may be a source of refractory disease. BMECs treated with combretastatins showed distinct degradation and disruption of microtubule cytoskeleton as well as an internalization of the adhesion molecule VCAM-1 one hour after combretastatin treatment. The combretastatin-treated BMECs were still viable but showed dramatic reduction in migratory function and adhesion molecule expression. When AML cells were co-cultured on combretastatin-treated BMECs, leukemia cell adhesion was significantly reduced. Treatment with chemotherapy agents, Ara-C or azacitidine, in co-cultures of AML + combretastatin-treated BMECs showed significant reductions in AML cell viability (Ara-C: 71.4% (Vehicle) vs 54.4% (CA1) and 59% (CA4), p < .001; azacitidine: 73.5% (Vehicle) vs 56.7% (CA1) and 59.2% (CA4), p < .001), suggesting that combretastatin pre-treatment reverses EC protection of AML cells. Furthermore, treatment of leukemia cells with combretastatins induced a bottleneck at the G2/M checkpoint, resulting in increased proportion of leukemia cells at the S phase (39.1% (CA1) and 38.4% (CA4) vs. 29%, p < .001) and at the G2/M phase (48.2% (CA1) and 45.9% (CA4) vs. 10.4%, p < .0005), suggesting that combretastatins sensitize AML cells against cell-cycle cytotoxic agents. Finally, human AML xenograft experiments showed a complete clearance of AML cells in the bone marrow after combination treatment with low dose CA1P (OXi4503) and Ara-C or azacitidine; whereas Ara-C or azacitidine alone showed limited effect on AML engraftment in the bone marrow.Conclusion: BMECs protect AML cells from conventional cytotoxic chemotherapy partly through adhesion factors. However, this protection can be removed by pretreating the leukemia microenvironment with vascular disrupting combretastatins. Combination combretastatin + cytotoxic chemotherapy sensitizes AML cells and leads to improved leukemia regression. Results of this study support a phase IB study of OXi4503 and chemotherapy in patients with AML and advanced myelodysplastic syndrome. DisclosuresNo relevant conflicts of interest to declare.

Primary cutaneous CD20-positive T-cell lymphoma

CD20 is a transmembrane protein that is expressed by B cells during their development and is, therefore, commonly used to label cells of B lineage in lymphoid infiltrates. CD20-positive T-cell lymphoma is infrequent but well recognized. Cases reported in the literature show a variety of clinical and histoimmunochemical profiles. Primary cutaneous CD20-positive T-cell lymphoma is vanishingly rare; only eight cases have been previously reported. We present two new cases of this entity and describe their clinical, histological and immunohistochemical features. CD20 is a highly specific B-cell marker. However, it has been reported in a subset of normal T-cells in peripheral blood and bone marrow of healthy individuals. This subset of T-cells also expresses more often CD8 and g/d than the CD20-negative T-cells. Two main theories have been postulated to explain the expression of CD20 by neoplastic T-cells. The first possibility is that these lymphomas develop from the CD20-positive subset of normal T-cells. The second theory regards CD20 as an activation marker. Prognostic implications and therapeutic options of T-cell lymphomas with positivity for CD20 remain to be elucidated.

Differential gene expression in human hematopoietic stem cells specified toward erythroid, megakaryocytic, and granulocytic lineage

To better understand the transcriptional program that accompanies orderly lineage-specific hematopoietic differentiation, we analyzed expression changes during the lineage-specific differentiation of human hematopoietic stem cells (HSC; CD34+/CD38-/CD33-); HSC and multipotent myeloid progenitors (MMP; CD34+/CD38-/CD33+) were isolated from the bone marrow of healthy individuals by MACS. CD34+ cells in semi-solid culture were stimulated with the cytokines erythropoietin, IL-6, and G-CSF to promote differentiation to committed erythroid, megakaryocytic, and granulocytic clones, respectively. Differential display RT-PCR analysis was performed to compare the mRNA transcripts in HSC, MMP, and the committed lineage-specific clones derived from these committed lineage-specific progenitors. Expressed sequence tags (n=256), which were differentially expressed, were identified. One hundred ninety-four were homologous to known genes, and some were associated with hematopoiesis. These known genes were classified as involved in transcription/translation, signal transduction, cell surface receptors/ligands, cell signaling, cell metabolism, cell cycle, cell apoptosis, and oncogenesis. We identified genes, which were up- or down-regulated specifically in the lineage-committed clones compared with HSC or/and MMP, suggesting that specific gene activation and repression might be necessary for specific lineage commitment and differentiation. Our data provide an extensive transcriptional profile of human hematopoiesis during in vitro, lineage-specific differentiation.

Hyaluronan in the Bone Marrow of Healthy Individuals and Patients with Acute Myeloid Leukaemia.

In the connective tissues the two major structural components are collagens and glycosaminoglycans (GAGs). When assessing pathological processes in the extracellular matrix, e.g. fibrosis, attention is primarily directed to the collagens. Hyaluronan (HYA) is a GAG of great interest not only as a tentative marker of early fibrosis but also of importance for the disease process in various malignancies.Acute myeloid leukaemia (AML) is a clonal disorder characterised by abnormal proliferation of myeloid cell precursors. Research has mainly focused on the cellular events but the bone marrow matrix has attracted minor interest.In this study bone marrow biopsies were obtained from 35 newly diagnosed AML patients and 30 healthy individuals. The bone marrow sections were analysed histochemically for HYA and reticulin (type III collagen).The HYA staining was significantly stronger, p=0.003, in the AML patients compared to the healthy controls. Only one patient demonstrated abnormal reticulin staining score, but in the group of 8 patients with antecedent myelodysplastic syndrome (MDS), the reticulin staining score was significantly higher, p=0.003, compared to the patients with de novo AML. There was a significant correlation between the HYA and reticulin staining scores, p=0.005, in the AML patients as was seen in the control group, p=0.0005, indicating that the variables HYA and reticulin are not independent. No correlation was found between HYA grading and lactate dehydrogenase (LDH), number of blast cells, sex, age or antecedent blood disease before AML diagnosis. In the control group there was a significant correlation, p=0.042, between HYA and age.Our findings establish that there is a deposition of HYA in bone marrow in healthy individuals and that HYA is increased in AML patients. It is discussed whether HYA could be an early marker of impending fibrosis and also exert important effects on cellular events in the disease process.

Prevalence of parvovirus B19 and parvovirus V9 DNA and antibodies in paired bone marrow and serum samples from healthy individuals.

Parvovirus B19 (hereafter referred to as B19) exhibits a marked tropism to human bone marrow (BM), and infection may lead to erythema infectiosum, arthropathy, hydrops fetalis, and various hematologic disorders. Recently, a distinct parvovirus isolate termed V9 with an unknown clinical spectrum was discovered. In contrast to the many studies of B19 serology and viremia, valid information on the frequency of B19 or V9 DNA in the BM of healthy individuals is limited. To develop a reference value, paired BM and serum samples from healthy subjects were tested for the presence of B19 and V9 DNA and specific antibodies. Immunoglobulin M (IgM) was not found in any of the serum samples. The prevalence of IgG showed a gradual and steady increase from 37% in children aged 1 to 5 years to 87% in people aged >50 years. When 190 well-characterized subjects were examined, B19 DNA was detected in the BM of 4 individuals (2.1%; 95% confidence interval, 0.58 to 5.3%) while none of the paired serum samples showed evidence of circulating viral DNA. V9 DNA was not found in any of the BM or serum samples. The finding of B19 DNA probably indicated a primary infection in one 7-year-old individual and reinfection or reactivation of persistent infection in the remaining three persons, aged 47 to 58 years. Serving as a benchmark for future studies, these findings are useful when interpreting epidemiologic data, performing BM transplantation, or considering clinical implications of parvovirus infection.