FLT3 Splice Variant (FLT3Va) As a Potential Immunotherapeutic Target in Patients with Acute Myeloid Leukemia (AML)

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1681-1681
Author(s):  
Sophia Adamia ◽  
Jeffrey Nemeth ◽  
Shruti Bhatt ◽  
Sarah R Walker ◽  
Natalie I Voeks ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Cell Surface ◽  
Board Of Directors ◽  
Research Funding ◽  
Leukemic Cells ◽  
Advisory Committees ◽  
Gm Csf ◽  
Nsg Mice ◽  
Blocking Antibodies ◽  
Pdx Models

Abstract Alternative pre-mRNA splicing (AS) is a normal epigenetic phenomenon, a key regulator of gene expression, yields multiple transcripts and thus a variety of proteins from a single gene. Mutations in the spliceosome components resulting in aberrant splicing isoforms are common in AML, and other myeloid neoplasms, and may generate leukemia-specific neoantigens targetable with an antibody-drug conjugates (ADCs) or blocking antibodies. Our previous studies revealed that the FLT3 cell surface receptor is one of the most commonly misspliced genes in AML (54-63% of ~400 AML patients). We conducted cloning and sequencing analyses in AML cells and identified multiple aberrant splice-variants of FLT3 that resulted from either skipping of one or more exons or activation of cryptic splicing sites. Transfection of cDNA with three of these variants in TF-1 (AML cell line) cells resulted in expression of Flt3 variant proteins on the cell surface. We successfully generated rabbit polyclonal antiserum against a unique peptide sequence present in the most commonly expressed abnormal splice variant, which we termed Flt3Va. Immunoblots performed with the polyclonal antibody identified a ~160 kDa protein expressed by TF-1 cells transfected with FLT3Va, and the antibody did not react with untransfected TF-1 cell lysate. Using standard techniques, we generated rabbit hybridomas and evaluated the clones by flow cytometry and western blotting experiments. Based on these data, we selected one antibody clone (15-7) for further experiments. The 15-7 anti-Flt3Va rabbit monoclonal antibody identified Flt3Va protein expressed on the cell surface and within the cytoplasm of transfected TF-1 cells by flow cytometry and western blotting. However, no Flt3Va protein was detected in untransfected TF-1 cells or normal CD34+ bone marrow cells. The 15-7 antibody bound to 26 of 52 primary AML samples and 5 of 10 primagraft samples (PDX models) of human AML. Immunoblotting analyses of PDX models and patient samples confirmed binding to a protein of the expected size (130-160 kDa). Additionally, multi-parameter flow cytometry in 10 PDX models and 52 primary demonstrated that putative AML stem cells (as defined by the CD45dim, CD34, CD38, CD33, c-Kit cell surface expression) co-expressed Flt3Va antigen in 50% samples evaluated. An analysis of Flt3Va protein localization by live cell imaging showed a punctate distribution of Flt3Va on the cell surface. Furthermore, we observed that overexpression of Flt3Va in TF-1 cells led to GM-CSF growth factor independence. Analysis of TF-1 cells in the absence of GM-CSF and Flt3 ligand demonstrated constitutive activation of STAT5, an important mediator of Flt3 signaling, in Flt3Va overexpressing cells. In addition, Erk1/2 phosphorylation was also increased in Flt3Va overexpressing cells, another downstream effector of Flt3. In an effort to determine if Flt3Va+ cells had tumor repopulating ability, we sorted 0.3X10^6 Flt3Va+ and Flt3Va- cells from a PDX sample and injected the sorted populations or unsorted bulk tumor cells into NSG mice. The human cell engraftment in the mice was detected by the expression of human CD45, CD33, CD34, CD38, and c-kit antigens in the peripheral blood. In two experiments, mice injected with Flt3Va+ cells had detectable circulating leukemic cells by ~18 days after injection, while those injected with Flt3Va- cells had detectable circulating leukemic cells after the 4th week. These results suggest both Flt3Va+ and Flt3Va- cell populations are able to reconstitute leukemia after transplantation in NSG mice. However, Flt3Va+ may be expressed by an aggressive AML clone that facilitate early tumor engraftment. Overall, these studies suggest that Flt3Va is a leukemia-specific neoantigen and is an attractive potential immunotherapeutic target in AML. Proteins such as Flt3Va generated by alternative splicing are common in AML and may be targets for of novel blocking antibodies or ADCs, minimizing effects on normal tissues. Disclosures Adamia: Janssen: Research Funding. Nemeth:Janssen: Employment. Attar:Janssen: Employment. Letai:AbbVie: Consultancy, Research Funding; Tetralogic: Consultancy, Research Funding; Astra-Zeneca: Consultancy, Research Funding. Steensma:Millenium/Takeda: Consultancy; Celgene: Consultancy; Amgen: Consultancy; Janssen: Consultancy; Ariad: Equity Ownership; Genoptix: Consultancy. Weinstock:Novartis: Consultancy, Research Funding. DeAngelo:Novartis: Consultancy; Ariad: Consultancy; Pfizer: Consultancy; Baxter: Consultancy; Celgene: Consultancy; Incyte: Consultancy; Amgen: Consultancy. Stone:Agios: Consultancy; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celator: Consultancy; Juno Therapeutics: Consultancy; Roche: Consultancy; Jansen: Consultancy; Pfizer: Consultancy; ONO: Consultancy; Sunesis Pharmaceuticals: Consultancy; Merck: Consultancy; Xenetic Biosciences: Consultancy; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy; Amgen: Consultancy; Karyopharm: Consultancy; Seattle Genetics: Consultancy. Griffin:Janssen: Research Funding; Novartis: Consultancy, Research Funding.

Enhanced and Accelerated Repopulation of Mutant C-Kit Immunodeficient Mice By Transplants of Primary Chronic and Acute Myeloid Leukemic Human Cells

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 4537-4537 ◽  
Author(s):  
Naoto Nakamichi ◽  
Colin A. Hammond ◽  
Paul H. Miller ◽  
Katharina Rothe ◽  
Philip A Beer ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Research Funding ◽  
Hematopoietic Cells ◽  
Leukemic Cells ◽  
Advisory Committees ◽  
Immunodeficient Mice ◽  
Gm Csf ◽  
Nsg Mice ◽  
Cd34 Cells ◽  
Normal Human

Abstract Background: Assessment of the growth and differentiation of human hematopoietic cells transplanted into immunodeficient mice has become an important method for evaluating the numbers and properties of cells with engraftment potential and the progeny they can generate in an in vivo setting. Such xenograft models have undergone numerous modifications and have also been applied with increasing success to primary sources of many types of malignant as well as normal human hematopoietic cells. These advances include the incorporation of cDNAs encoding various human-specific growth factor genes into the genomes of the widely used and long-lived NOD-scid-IL2Rγcnull (NSG) mouse, the creation of regenerated human bone ossicles within the mice to more closely mimic the human marrow microenvironment, recognition of the superior supportive activity of female mice, and more recently of NSG mice additionally compromised by their genetic acquisition of a c-kit deficiency. Exploitation of these modifications to recipients of human hematopoietic cells has greatly increased our understanding of the complex composition of both normal and leukemic populations and their responses to various treatments. Nevertheless, many examples remain of both acute and chronic human myeloid leukemias that do not engraft or engraft very poorly, even in the most permissive mice thus far tested. These include samples of many cases of chronic phase chronic myeloid leukemia (CP-CML), myelodysplastic syndromes (MDS), and approximately one third of all cases of acute myeloid leukemia (AML). We have now created 2 new strains of immunodeficient mice that have the B, T, NK immunodeficiency determined by a SirpαNOD-Rag1-/--IL2Rγc-/- genotype (which is equivalent to that of NSG mice) and a c-kit deficiency obtained by replacement of the wild-type c-kit gene with a homozygous W41/W41genotype (SRG-W41 mice). The second strain has the same SRG-W41 genotype but is also transgenic for human IL3, GM-CSF, and SCF production (SRG-W41-3GS). NRG/SRG mice were chosen as the parental strain because they support similar levels of chimerism as NSG mice when given a radiobiologically equivalent dose of radiation, but can benefit from split or low dose rate irradiation protocols. Results: We first showed that leukemic cells from patients with AML and CP-CML produce progeny more rapidly in sub-lethally irradiated parental SRG-3GS mice than in SRG mice, and that SRG-W41 mice can support higher levels of human myeloid and B-lymphoid chimerism by normal human CD34+ cord blood (CB) and adult bone marrow (BM) cells than similarly suppressed or non-irradiated SRG controls. We then compared the chimerism obtained in different strains of mice transplanted each with 6x106 CD34+ cells from 1 CP-CML patient or ~106 CD34+ cells from 5 different AML patients pre-selected for their previously demonstrated poor or inability to engraft NSG-3GS mice. Within a few weeks, the level of the predominantly myeloid chimerism in 2 non-irradiated male SRG-W41-3GS mice and 2 sub-lethally irradiated female SRG-3GS recipients became equivalent and this equivalence was sustained for over a year. Only 3 of 5 AML samples tested engrafted either sex of sub-lethally irradiated SRG-W41-3GS or SRG-3GS mice, and in each case, the speed and level of engraftment was greatly enhanced in the SRG-W41-3GS mice as compared to sex-matched SRG-3GS hosts (with 20-30-fold and 2-3-fold higher levels at week 6 and 10 respectively in female as compared to male recipients of either strain). All the engrafted SRG-W41-3GS female hosts became moribund within 20 weeks post-transplant with a predominance of human leukemic cells in their BM and enlarged spleens filled with leukemic cells. In contrast, the SRG-3GS recipients of the same AML cells survived more than 20 weeks with a more delayed appearance of leukemic cells. Sublethally irradiated female SRG-W41-3GS recipients of 0.1-0.2x106 CD34+ cells from 3 of 3 chronic myelomonocytic leukemia (CMML) patients tested to date have also shown engraftment at either week 3 or 11 and, in one case, up to 17 weeks post-transplant. Conclusion: The introduction of a c-kit deficiency into highly immunodeficient SRG mice producing human IL3, GM-CSF and SCF transgenically offers new opportunities for examining the growth potential and sensitivity to treatment of a broader spectrum of primary human leukemias and neoplastic conditions than has been previously possible. Disclosures Deininger: Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; CTI BioPharma Corp.: Membership on an entity's Board of Directors or advisory committees; Gilead: Research Funding; BMS: Consultancy, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Ariad: Consultancy, Membership on an entity's Board of Directors or advisory committees.

scholarly journals Secreted Mutant Calreticulins As Rogue Cytokines Trigger Thrombopoietin Receptor Activation Specifically in CALR Mutated Cells: Perspectives for MPN Therapy

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 4-4 ◽  
Author(s):  
Christian Pecquet ◽  
Thomas Balligand ◽  
Ilyas Chachoua ◽  
Anita Roy ◽  
Gaelle Vertenoeil ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Flow Cytometry ◽  
Cell Surface ◽  
Board Of Directors ◽  
Research Funding ◽  
Advisory Committees ◽  
Allele Burden ◽  
In Trans ◽  
Equity Ownership ◽  
In Cells

Abstract Background Mutant calreticulins carrying the sequence translated after a +1 frameshift at the C-terminus are major drivers of myeloproliferative neoplasms (MPNs). These mutant CALRs bind and activate TpoR/MPL in cells co-expressing TpoR and mutant CALRs, resulting in persistent JAK2-STAT5 signaling. Whether mutant CALR proteins are secreted, thus acting in trans on other cells, is not known. Aims Our objectives were to: 1) assess the direct TpoR-mutant CALR interaction both when expressed in the same or in different cells; 2) determine whether mutant CALRs are secreted; and 3) determine whether mutant CALR can act as extracellular cytokines. Methods Engineered CALR and TpoR mutants were analyzed by a combination of biochemical approaches (bioluminescence resonance energy transfer, recombinant protein production), functional assays (cell growth and transcriptional assays, flow cytometry, primary megakaryocytic clonogenic assay, analysis of CALR del52 knock-in mice) and cell imaging (confocal microscopy, flow cytometry and immuno-gold electron microscopy). Secreted CALRs were determined by ELISA using mutant specific antibodies. Results 1) Two systems provided evidence that mutant CALRs and TpoR directly interact. First, using Nano-BRET in cells co-expressing N-terminally fused TpoR or EpoR with Nano-luciferase and mutant or WT CALR C-terminally tagged with HaloTag that is bound to the 618-ligand fluorophore, we show that TpoR and mutant CALRs interact in a complex whether the two proteins are within 10 nm. The interaction does not occur between TpoR and WT CALR, or between EpoR and mutant or WT CALRs. Second, expressing mutant CALR and TpoR extracellular domain in S2 Drosophila Schneider cells showed that stable complex formation requires immature high mannose structure on TpoR. Lastly, we could detect surface expression of the TpoR/CALRdel52 complex using proximity ligation assay with anti-TpoR and anti-mutant CALR antibodies in CRISPR/Cas9 engineered UT7/Tpo cells that express endogenous mutant CALR and TpoR levels. 2) We used flow cytometry, confocal immunofluorescence and immunogold electron microscopy and could show that mutant CALRs are trafficking via cis-, medial- and trans-Golgi to the cell-surface and are secreted, independently from TpoR expression. Importantly, mutant CALRs are also secreted in CALR mutated MPN patients as determined by mutant CALR-specific ELISA assay in patient plasma (mean plasma level 24.6 ng/ml, range 0-156.5 ng/ml). In the 113 evaluated CALR mutated patients from different centers the plasma mutant CALR levels correlated with CALR mutant allele burden (P<0.001). Secreted mutant CALR can also be found in plasma from knock-in CALR del52 mice. 3) We show that recombinant mutant CALR can act as a cytokine and specifically stimulate JAK2-STAT5 pathway in cells that carry the TpoR at the surface. Using Nano-BRET, we could demonstrate that extracellular mutant Halo-tagged CALR can specifically bind in trans to the cell-surface TpoR fused with Nano-luciferase, but not to EpoR fused with Nano-luciferase. This binding and the subsequent JAK2 activation were obtained at levels of around 100-150 ng/ml only in cells exposing at the cell-surface TpoR with at least one immature N-linked sugar. This can be accomplished by co-expressing in the reporter cells non-tagged mutant CALR, which will promote cell-surface localization of partially immature TpoR. The effect of exogenous mutant CALR could involve both stabilization of the endogenous cell-surface mutant CALR-TpoR complexes and binding to unoccupied immature TpoRs. Conclusion We show that mutant CALRs directly interact with TpoR and also are secreted and can act as rogue cytokines, leading to activation of cells carrying TpoR. Activation of TpoR in trans is efficient at mutant CALR levels similar to those detected in patients when target cells co-express heterozygous mutant CALR and TpoR, where endogenous mutant CALR transports to the surface TpoR with immature glycosylation. Thus, secreted mutant CALRs is predicted to expand the MPN clone. Given that cell-surface mutant CALR in TpoR expressing cells is crucial for oncogenicity, and that mutant CALRs are also secreted correlating with allele burden, we discuss how antibodies and other immunotherapy approaches could specifically target the mutant CALR MPN clone. Disclosures Xu: MyeloPro Research and Diagnostics GmBH: Employment. Hug:MyeloPro Diagnostics and Research GmbH: Employment. Gisslinger:Janssen: Consultancy, Honoraria; AOP Orphan: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Shire: Honoraria; Novartis: Consultancy, Honoraria, Research Funding. Kralovics:MyeloPro Diagnostics and Research GmbH: Equity Ownership. Constantinescu:Personal Genetics: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy; Novartis: Membership on an entity's Board of Directors or advisory committees; AlsaTECH: Equity Ownership; Novartis: Honoraria; MyeloPro Research and Diagnostics GmbH: Equity Ownership.

scholarly journals B-Cell Maturation Antigen (BCMA) in Systemic Light-Chain Amyloidosis (AL): Association with Disease Activity and Its Modulation with Gamma-Secretase Inhibition

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4409-4409 ◽  
Author(s):  
Amandeep Godara ◽  
Ping Zhou ◽  
Benjamin Rosenthal ◽  
Adin Kugelmass ◽  
Denis Toskic ◽  
...  
Keyword(s):  
Cell Surface ◽  
Disease Activity ◽  
Board Of Directors ◽  
Plasma Cell ◽  
Light Chain ◽  
Research Funding ◽  
San Diego ◽  
Plasma Cells ◽  
Advisory Committees ◽  
Nsg Mice

Introduction: Systemic light-chain (AL) amyloidosis results from clonal plasma cells that secrete toxic fibril-forming free light chains. Therapies directed at the plasma cell clone form the backbone of its management. Identification of cell-surface receptors on the clonal cells can provide targets for therapy. BCMA is one such cell-surface glycoprotein; it is principally expressed on plasma cells and supports their long-term survival (J Exp Med. 2004;199:91-98). Anti-BCMA immunotherapies are currently being studied in multiple myeloma (N Engl J Med. 2019;380:1726-1737). Membrane-bound BCMA (mBCMA) is also shed as a soluble form, sBCMA, due to γ-secretase activity that can be inhibited by a small molecule (GSI, LY-411575) (Nat Commun. 2015;6:7333; J Immunol. 2017;198(8):3081-3088). We report on mBCMA on the clonal plasma cells of AL patients and its modulation by GSI in vitro, and on sBCMA in the blood of AL patients and of mice xenografted with an AL cell line, demonstrating its correlations in vivo with free light chain (FLC) levels and plasma cell tumor burden. Methods: We analyzed mBCMA and sBCMA levels in marrow aspirate and peripheral blood samples from AL patients under an IRB approved protocol. We isolated mononuclear cells (MNC) from patient marrow aspirates with anti-CD138 microbeads (Miltenyi Biotec, Auburn, CA), and used the CD138-selected cells in culture with LY-411575 (Sigma Aldrich, St Louis, MO). We analyzed mBCMA expression by flow cytometry using APC conjugated anti-CD269 (BCMA) antibody (Biolegend, San Diego, CA, USA) and CD138 expression by PE-conjugated anti-CD138 antibody (Biolegend, San Diego, CA, USA), along with appropriate isotype controls. We injected 107 ALMC-1 reporter cells in the flanks of NOD scid gamma (NSG) mice to create a xenograft model of AL clonal plasma cell disease (Jackson Laboratories, Bar Harbor, ME). sBCMA in patients and mice and FLC in mice were measured by ELISA (R&D Systems, Minneapolis, MN; Bethyl lab Montgomery, TX respectively). Pearson and Spearman correlation analysis was used to examine associations of sBCMA and clinical disease parameters. Paired t-test was applied to compare BCMA expression before and after treatment with GSI. Results: Marrow and blood were obtained from 20 AL patients, 8 newly diagnosed, 4 with progression of disease, and 8 after treatment with >VGPR. Their median age was 65 years (range, 48-77) and 50% were female. Median plasma cells in the marrow aspirates and involved FLC levels were 5% (1-20%) and 33 mg/L (6.6-2220mg/L) respectively. Median mBCMA expression on CD138+ marrow MNC and sBCMA levels in plasma were 39% (4-83) and 28.5 ng/ml (6.6-100.3) respectively (Figure 1A-B). sBCMA levels correlated with bone marrow plasma cell percentage and iFLC (both p<0.001, Figure 1C-D). In culture with LY-411575, the percentages of CD138 cells positive for mBCMA increased from 85% to 100% with ALMC-1 cells and from 36% to 68% (p < 0.01) with patient CD138-selected cells while the sBCMA levels in culture supernatant decreased by over 50%. In NSG mice with ALMC-1 reporter cell xenografts, medians of luciferin-based bioluminescence FLUX (photons/s), λ FLC and sBCMA were 3.9x1010 (2.02x109-1.2x1011), 949.1 mg/L (868.8-23629.2), and 3.8 ng/ml (0.9-23.6) respectively. sBCMA levels correlated with FLC (Pearson r= 0.99, p<0.0001) and with FLUX (Pearson r=0.61, p=0.07). Conclusions: BCMA is expressed on AL plasma cells and sBCMA is detected in the blood of all AL patients. In this light chain disease, sBCMA may be useful as a marker of disease activity even in patients with low FLC. Furthermore, expression of mBCMA can be manipulated by treatment with a GSI, an approach which may be useful therapeutically in AL. These results provide the basis for applying anti-BCMA immunotherapies in clinical trials in relapsed refractory AL patients. Disclosures Comenzo: Sanofi-Aventis: Membership on an entity's Board of Directors or advisory committees; Unum: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Research Funding; Caelum: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Research Funding; Prothena Biosciences: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Myself: Patents & Royalties: Patent 9593332, Pending 20170008966.

scholarly journals Myeloproliferative Neoplasm (MPN) Blastic Transformation Occurs at the Level of Hematopoietic Stem Cells

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 101-101
Author(s):  
Xiaoli Wang ◽  
Cing Siang Hu ◽  
Joseph Tripodi ◽  
Vesna Najfeld ◽  
Bruce Petersen ◽  
...  
Keyword(s):  
T Cells ◽  
Stem Cell ◽  
Board Of Directors ◽  
Research Funding ◽  
Chromosomal Abnormalities ◽  
Myeloproliferative Neoplasm ◽  
Leukemic Cells ◽  
Advisory Committees ◽  
Hematopoietic Stem ◽  
Nsg Mice

Abstract Myeloproliferative neoplasm-blast phase (MPN-BP) and de novo acute myeloid leukemia (AML) each have distinct mutational patterns and clinical courses. MPN-BP patients have a particularly dismal prognosis with a median survival of less than 6 months with currently available therapies. So far, the cellular hierarchy that characterizes MPN-BP and the evolution of various leukemia-initiating clones (LIC) in MPN-BP have not been well delineated. We therefore established an in vivo MPN-BP xenograft model to address these questions. Among the 22 patients with MPN-BP studied 11 were cytogenetically normal while the remainder had multiple chromosomal abnormalities including del(5), del(20q), del(14), +1q, del(17p). 86% of the patients had at least 2 myeloid malignancy gene mutations including JAK2, ASXL1,TET2, MPL, SF3B1, RUNX1, U2AF1, PTPN11, IDH1/2, SRSF2 and TP53. These findings indicate that MPN-BP is characterized by multiple mutational events and cytogenetic abnormalities. T cell-depleted mononuclear cells from 8 of 14 patients engrafted in NSG mice {>0.5% hCD45+ cells in bone marrow (BM)}. Among them, samples from 6 patients resulted in a high degree of hCD45+ cell chimerism (34.6±6.4% in BM) and recapitulated numerous aspects of MPN-BP within 4 months, including the presence of at least 20% hCD45dimCD33+ cells or hCD34+ cells, or at least 20% blasts as detected by morphological examination of the marrow and leukemia cell dissemination to the spleen and PB. These mice had a 2.8±0.6- fold increase in splenic weight as compared to mice receiving PBS alone. The leukemic mice were characterized by reduced blood counts, suggesting that MPN-BP cells suppressed normal murine hematopoiesis, or led to cytopenias due to hyper-splenism. Moreover, the greater degrees of blast cell chimerism and the higher frequency of leukemia initiating cells as determined by limiting dilution analyses correlated with a shorter time to leukemia initiation and an inferior clinical outcome of the transplanted NSG mice. Grafts from each of these 6 MPN-BP patients produced a large number of donor-derived myeloid cells and a smaller number of lymphoid cells (mostly CD3+ and few CD19+). Cells belonging to each of these lineages and leukemic cells in primary recipients produced from Pts 4, 5, 6 and 11 had an identical proportion of chromosomally abnormal and mutated cells as primary cells [Pt 4: JAK2V617F, TET2 and PHF6; Pt 5 and 11: Del (20q), +8; Pt 6: +1q, del(17p)], except that a small proportion of T cells from Pts 5 and 11 lacked chromosomal abnormalities. Furthermore, the degree of MPN-BP engraftment and leukemic cell burden increased with the subsequent 3 serial transplantations even when the recipients received progressively smaller numbers of MPN-BP cells from the prior recipient. Primary Pt 6 originally had a JAK2V617F+ PV but lost JAK2V617F at the time the MPN-BP occurred at which time there were two clonal cell populations, one with +1q (12%) and the other del(17p) (80%), the site of the TP53 gene, as well as normal cells (8%). In the primary recipient NSG the donor derived cells were JAK2V617F- but contained +1q (1%) and del(17p) (98.5%) and cytogenetically normal (0.5%). +1q and JAK2V617F were not observed, while cells containing the TP53 deletion alone were detected in donor derived leukemic cells, mature myeloid and T cells in the secondary and subsequent serial recipients. Furthermore, del(17p) was found in phenotypically isolated HSCs, MPPs, MLPs, CMPs, GMPs, MEPs, and mature T cells within the CD33- cell fraction as well as CD45dimCD33+ AML blasts selected from primary MPN-BP cells from Pt6. However, +1q was found exclusively in purified MLPs and MEP. These observations establish that cytogenetic and mutational events that lead to MPN-BP occur at different stages along the developmental HSC hierarchy and that a small population of normal HSCs persist. Furthermore, in JAK2V617F+ MPNs that develop MPN-BP and lose JAK2V617F, additional cytogenetic events occur at different stages along the JAK2V617F- MPN-BP-stem cell hierarchy. Our ability to serially transplant the LIC from these patients has allowed us to create the first MPN-BP PDX model that will not only extend our understanding of MPN-BP stem cell biology but might also prove useful for screening drugs to treat MPN-BP. Disclosures Rampal: Jazz: Consultancy, Honoraria; Incyte: Honoraria, Research Funding; Stemline: Research Funding; Constellation: Research Funding; Celgene: Honoraria. Mascarenhas:Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; CTI Biopharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding; Roche: Research Funding; Novartis: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Promedior: Research Funding; Janssen: Research Funding. Hoffman:Formation Biologics: Research Funding; Summer Road: Research Funding; Merus: Research Funding; Incyte: Research Funding; Janssen: Research Funding.

scholarly journals Leukemic Cell Expressed CTLA-4 Suppresses T Cells Via Down-Modulation of CD80 By Trans-Endocytosis

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3221-3221 ◽  
Author(s):  
Priscilla Do ◽  
Kyle A. Beckwith ◽  
Larry Beaver ◽  
Brittany G. Griffin ◽  
Xiaokui Mo ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
T Cells ◽  
T Cell ◽  
B Cells ◽  
Cell Surface ◽  
Board Of Directors ◽  
Tumor Cells ◽  
Research Funding ◽  
Leukemic Cell ◽  
Advisory Committees

Abstract The function of CTLA-4 on non-T cells is largely ignored and currently ill defined despite rapidly growing interest in targeting this immune checkpoint protein in several cancers. While anti-CTLA-4 therapy is proposed to work through inhibition of the immunosuppressive effect of CTLA-4 on T cells, multiple examples of non-T cell expressed CTLA-4 have been reported. These cells include tumor cells of hematological and non-hematological origin and normal B cells. In this study, we have defined a novel immune suppressive role for non-T cell, tumor expressed CTLA-4 in Chronic Lymphocytic Leukemia (CLL). We have detected by microarray that CTLA-4 is in the top 5 most differentially expressed genes between pooled samples of healthy donor normal B cells (N=6) and pooled CLL leukemic B cells (N=5). Upregulation of CTLA-4 by CLL B cells compared to normal B cells was validated by RT-qPCR and flow cytometry. CTLA-4 was predominantly intracellular (42/46 CTLA-4+) and not on the cell surface (2/48 CTLA-4+) in primary CLL samples. B cell activating factors (CD40L, PMA/Ionomycin, LPS, IL4, LPS+IL4, CD40L+IL4, CpG, and anti-IgM) could not induce surface expression of CTLA-4; however, co-culture with anti-CD3/anti-CD28 or ConA activated T cells (autologous or allogeneic) resulted in detectable CTLA-4 on the cell surface of leukemic B cells. This induction did not occur with resting T cells. This finding suggests a role for CTLA-4+ tumor cells in sites of T cell activation, such as the lymph node, a site of leukemic cell proliferation in CLL. To mechanistically study leukemic B cell expressed CTLA-4, we generated CLL-derived Mec1 and OSU-CLL that inducibly express CTLA-4 upon doxycycline (dox) treatment. Mec1 and OSU-CLL cells highly express the ligands for CTLA-4, CD80 and CD86. Dox-induction of CTLA-4 resulted in decreased expression of Mec1 and OSU-CLL expressed CD80, a critical T cell co-stimulatory protein (N=3). Blockade of CTLA-4 using the anti-CTLA-4 therapeutic antibody, Ipilimumab, could restore CD80 on Mec1 and OSU-CLL cells (N=3). Because T cell-expressed CTLA-4 has been previously shown by others to down-modulate CD80 via trans-endocytosis, we co-cultured CTLA-4+ Mec1 and CTLA-4+ primary CLL cells with stably transfected CD80-GFP or CD86-GFP Hek293 cell lines to assess uptake of CD80/CD86 into CTLA-4 expressing tumor cells as the mechanism of CD80 down-modulation. Transfer of CD80-GFP and CD86-GFP was detected by flow cytometry in primary CLL cells and the Mec1 cell line, consistent with the ability of T cell expressed CTLA-4 to trans-endocytose CD80 and CD86. Furthermore, uptake of CD80-GFP or CD86-GFP by primary tumor cells was CTLA-4 dependent, demonstrated by inhibition of GFP uptake in the presence of Ipilimumab. Following determination of decreased CD80, we found that co-culture of primary T cells with Mec1 CTLA-4+ cells resulted in decreased IL2 production measured by Cytokine Bead Array. The loss of IL2 signified decreased co-stimulation as a result of tumor expressed CTLA-4. Studies are ongoing regarding dependence on CD80 or CD86. A minor subset of T cells, Tregs, are known to exert profound immunosuppressive effects through their expression of CTLA-4. Due to our results, tumor expressed CTLA-4 has an overlapping function with Treg CTLA-4, and it is imperative that we define the immunosuppressive effects as, in patients, the leukemic cells may comprise a much larger proportion of white blood cells than T cells. Efforts are now underway to address the effect of tumor expressed CTLA-4 in suppressing anti-tumor immunity in vivo utilizing a novel mouse model. Suppression of T cells by tumor expressed CTLA-4 is a novel finding that is broadly applicable to fields within and outside of cancer research as the pathway and mechanism described here are potentially applicable to CTLA-4 in diverse disease contexts and to the general biology of CTLA-4. [Funding: This work was supported by P01 CA95426. PD received the Pelotonia Graduate Fellowship. Any opinions, findings, and conclusions expressed in this material are those of the author(s) and do not necessarily reflect those of the Pelotonia Fellowship Program] Disclosures Jones: AbbVie: 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, Research Funding; Pharmacyclics, LLC, an AbbVie Company: Membership on an entity's Board of Directors or advisory committees, Research Funding.

scholarly journals CD79b Expression in Richter's Transformation

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4279-4279 ◽  
Author(s):  
John N. Allan ◽  
Erica B Bhavsar ◽  
Tiziana Vaisitti ◽  
Vincent Sarno ◽  
Yifang Liu ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
B Cell ◽  
Board Of Directors ◽  
Splice Variant ◽  
Research Funding ◽  
Surface Expression ◽  
Rna Seq ◽  
Advisory Committees ◽  
Richter's Transformation ◽  
Pdx Models

Background The B cell receptor (BCR) is a signaling complex composed of surface immunoglobulin and heterodimer subunits, Igα (CD79a) and Igβ (CD79b) (Sanchez, et al. 1993). Chronic lymphocytic leukemia (CLL) demonstrates dim surface staining of CD79b compared to normal B cells or other B cell malignancies, in part due to overexpression of a splice variant that lacks coding for the extracellular domain (Alfarano, et al. 1999; Cabezudo, et al. 1999). Aggressive lymphomas, like diffuse large B cell lymphomas of non-germinal center origin (DLBCL-ABC), overexpress surface CD79b and can harbor gain of function mutations (Schmitz, et al. 2018). Richter's transformation (RT), a complication of CLL is defined by transformation to a DLBCL-ABC subtype most commonly. Upon transformation outcomes are poor and survival is short with standard therapeutic approaches. Polatuzumab vedotin (Pv), an antibody drug conjugate, targets CD79b on the surface and has obtained FDA approval for relapsed DLBCL in combination with bendamustine and rituximab. Targeting CD79b may represent an attractive therapeutic strategy for patients (pts) with RT. To this end we sought to characterize CD79b expression in RT. Methods Pts with CLL or RT and available paraffin embedded tissue blocks were identified in coordination with Weill Cornell Medicine's (WCM) pathology department. Clone AT107-2 (Bio-Rad, USA) which targets an intracellular epitope was used to stain for CD79b in formalin fixed paraffin embedded (FFPE) tissue sections after optimization following institutional staining procedures. CD79b was classified as either positive (pos) or negative (neg) based on staining pattern and intensity as deemed by a board certified hematopathologist. RT pt derived xenografts (RT-PDXs) were assessed for surface expression of CD79b via flow cytometry. Nonpermabilized cells derived from RT-PDXs were stained using an anti-human CD79b-FITC conjugated antibody (clone CD3-1, Southern Biotech, USA). Mean fluorescence intensity (MFI) was established. RNA seq data was obtained from 2 of 3 RT-PDX models and has been reported previously (Vaisitti, et al. 2018). CD79b transcripts per million (TPM) were analyzed and compared to that of normal lymph node (LN) tissue deposited in the Human Protein Atlas RNA Seq database (HPA-RNA Seq). GraphPad Prism 8.0 was used to perform statistical analysis. Results Nineteen pts with RT and 5 pts with CLL were identified for the study. Median age at diagnosis of the 19 RT pts was 71 years compared to 67 years for the 5 CLL pts. Five RT pts (26%) were treatment naïve (TN) at time of RT. Ten (53%) RT pts transformed on targeted therapy, 6 on BTK inhibitors, 2 on IMiD based therapy, 2 on venetoclax. CD79b stained pos for 16 RT pts (84%) and all 5 (100%) CLL pts. We were not able to identify any correlations between CD79b expression due to low numbers of neg cases. Surface expression of CD79b was evaluated on RT-PDX models from different passages and found to be pos in all 3 models with a median percentage of CD79b+ cells of 45.9% (range 34.6-76%). The median MFI was 2028.5 (range MFI 860-4289). Two of the 3 three models had bimodal populations of cells (pos and neg) whereas the third model was more uniformly pos. RNA seq data from 2 RT-PDX models was available and compared to RNA-seq data from normal LN tissue deposited in the HPA-RNA Seq database. The mean TPM of CD79b for RT-PDX cases was 837.5 compared to 311.5 for normal LN tissue, p=0.028. Conclusion CD79b expression was pos in 84% of FFPE primary RT specimens evaluated. We were able to confirm extracellular CD79b expression with flow cytometry in all 3 RT-PDX models with a median MFI of 2028.5. Surface expression was found to be bimodal in 2 models and uniformly pos in 1 model suggesting tumor heterogeneity. Rna-seq data from RT-PDX models demonstrated higher TPM values in RT-PDX samples compared to normal LN tissue. We conclude that RT expresses CD79b at sufficient levels despite deriving from a CLL cell that historically has demonstrated low surface CD79b expression. Further studies will be undertaken characterizing pos and neg cellular populations focusing on mechanisms of expression and potential differences in splice variant expression. Disclosures Allan: Pharmacyclics LLC, an AbbVie company: Consultancy; Verastem Oncology, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy; Sunesis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Acerta Pharma: Consultancy; Janssen: Consultancy, Honoraria; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees. Vaisitti:Verastem Inc: Research Funding; VelosBio Inc.: Research Funding. Joyce:Genentech: Employment. Schulz:Genentech, Inc.: Employment; Roche: Equity Ownership. Deaglio:Verastem Inc: Research Funding; iTeos Therapeutics: Research Funding; VelosBio Inc.: Research Funding. Furman:Genentech: Consultancy.

scholarly journals Rare Germline Mutations in Complement Regulatory Genes Make the Antiphospholipid Syndrome Catastrophic

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4-4 ◽  
Author(s):  
Shruti Chaturvedi ◽  
Evan M Braunstein ◽  
Xuan Yuan ◽  
Hang Chen ◽  
Ravi Kumar Alluri ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Cell Surface ◽  
Board Of Directors ◽  
Complement Activation ◽  
Research Funding ◽  
Germline Mutations ◽  
Functional Assay ◽  
Advisory Committees ◽  
Surface Deposition

Introduction: The antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity along with persistent antiphospholipid antibodies (aPL). Despite adequate anticoagulation, 10-30% of patients have recurrent thrombosis. Catastrophic APS (CAPS) is associated with approximately 40% mortality despite treatment. The pathogenesis of APS complications is incompletely understood. Recent animal studies indicate that complement is required for aPL-associated thrombosis, and complement has emerged as an attractive therapeutic target for refractory thrombotic APS and CAPS. Methods: We first evaluated complement activation in sera of patients with thrombotic APS by ISTH criteria (N=53), catastrophic APS (CAPS; N=8, sera available for 6), and systemic lupus erythematosus (SLE; N=74) who presented to our institution from June 2015 to June 2019 (and four patients with CAPS from other institutions). We used the modified Ham (mHam) test, a functional assay for complement activation as described previously (Gavriilaki et al. Blood 2015). The mHam assay is based on the principle that a PNH cell line (PIGA-null TF-1 cells) lacking the cell surface complement regulators CD55 and CD59 undergoes lysis in serum containing activated complement. Cell death (measured by a cell viability assay) is a measure of complement activation. Cell surface deposition of complement products (C3c, C5b-9) is also detected by flow cytometry. We then evaluated whether adding purified patient-derived aPL (anti-β2 glycoprotein IgG) to normal serum induced complement activation. Finally, we performed targeted sequencing of 15 complement genes in the study subjects, as well as 22 patients with aHUS and 36 healthy individuals as positive and negative controls, respectively. Results: (A) Complement activation is associated with thrombotic APS. A positive mHam assay (&gt;20% cell killing) was detected in 32.1% (17 of 53) patients with thrombotic APS and 100% (6 of 6 with available sera) of CAPS compared with 6.8% (5 of 74) with SLE, (P &lt;0.001) (Fig. 1A). A history of thrombosis was present in 79.3% patients with a positive mHam and 38.4% with a negative mHam test. Among APS patients, mHam positivity was associated with triple positivity (lupus anticoagulant, anti-β2-glycoprotein-1 Ab and anti-cardiolipin Ab), which is associated with higher thrombotic risk (60%), than double (23%) or single positivity (10%) (P = 0.002) (Fig. 1B). APS patients were more likely to have a positive mHam closer to a thrombotic event (Fig. 1C). (B) aPL from patients activate complement in vitro. Patient-derived anti- β2 glycoprotein IgG from all four patients induced complement activation in the mHam assay (Fig 2A). Flow cytometry confirmed cell surface deposition of complement activation products (C4d, C5b-9), which was inhibited by adding anti-C5 monoclonal Ab or a factor D inhibitor (representative sample in fig. 1B). (C) Catastrophic APS is associated with complement mutations. Rare (minor allele frequency &lt;0.01) germline mutations in complement genes were present in 62.5% (5 of 8) patients with CAPS, 22.6% (12 of 53) patients with thrombotic APS, and 23.8% (5 of 21) of SLE compared with 50% (11 of 22) of aHUS, and 19.4% (7 of 36) of normal individuals. The mutation rate in CAPS was significantly higher than in APS (P=0.019), SLE (P=0.051), and normal controls and similar to that seen in aHUS (P=0.36). Rare variants in CAPS included: (i) homozygous CFHR1-CFHR3 deletion, (ii) THBD P501L, (iii) CR1 S1982G and homozygous CFHR1-CFHR3 deletion, (iv) CFHR4 R287H, and (v) CR1 V2125L. Conclusions: APS serum activates complement in vitro shown by a functional assay (mHam) and increased C5b-9 deposition on the cell surface. A positive mHam test strongly associates with both recent thrombosis and triple positive APS. Purified human anti-B2GPI antibody from APS patients activates complement when added to normal human serum, suggesting that complement activation plays a pathophysiologic role in APS associated thrombosis. Finally, CAPS patients have a high rate of mutations in complement genes, which likely serves as a 'second-hit' (in addition to aPL) leading to uncontrolled complement activation and a more severe phenotype (Figure 3). Taken together, our results provide a rationale for complement inhibition as a therapeutic strategy in patients with CAPS and refractory thrombotic APS. Disclosures Chaturvedi: Shire/Takeda: Research Funding; Sanofi: Consultancy; Alexion: Consultancy. Streiff:Pfizer: Consultancy, Honoraria; Bayer: Consultancy, Honoraria; Portola: Consultancy, Honoraria; Roche: Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Daiichi-Sankyo: Consultancy, Honoraria. Petri:Astellas: Consultancy; Novartis: Consultancy; Exagen: Consultancy, Research Funding; Glenmark Pharmaceuticals: Consultancy; EMD Serono: Consultancy; Bristol-Myers Squibb: Consultancy; IQVIA: Consultancy; Janssen Pharmaceuticals: Consultancy; Aleon Pharmaceuticals: Consultancy; Momenta Pharmaceuticals: Consultancy; Blackrock Pharmaceuticals: Consultancy; Astrazeneca: Consultancy, Research Funding; UCB Pharmaceuticals: Consultancy; GSK: Consultancy; Qiagen: Consultancy; Abbive: Consultancy; Amgen: Consultancy; Decision Resources: Consultancy; Principia Biopharma: Consultancy; Eli Lilly: Consultancy; Kezaar Life Sciences: Consultancy. McCrae:Dova Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Pfizer Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; Rigel Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; Sanofi Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Brodsky:Alexion: Membership on an entity's Board of Directors or advisory committees, Other: Grant funding; Achillion: Research Funding.

scholarly journals Risk Factors Associated with the Development of Infusion-Related Reactions in Patients with Chronic Lymphocytic Leukaemia Treated with Anti-CD20 Monoclonal Antibodies: Analysis of the CLL11 Study Dataset

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 3339-3339 ◽  
Author(s):  
Ciara Louise Freeman ◽  
Mark Dixon ◽  
Richard Houghton ◽  
Kathryn Humphrey ◽  
Gunter Fingerle-Rowson ◽  
...  
Keyword(s):  
Risk Factors ◽  
Monoclonal Antibodies ◽  
Board Of Directors ◽  
Research Funding ◽  
Lymphocytic Leukaemia ◽  
Signs And Symptoms ◽  
Leukemic Cells ◽  
Tumour Burden ◽  
Advisory Committees ◽  
Anti Cd20

Abstract Background: The administration of anti-CD20 monoclonal antibodies (mAb) in patients with B-cell lympho-proliferative disorders is frequently accompanied by a constellation of signs and symptoms that have been labelled as infusion-related reactions (IRR). The pathophysiology of IRR remains poorly understood as do predictors of risk, which may relate to the mechanism of action of the anti-CD20, disease-related factors such as tumour burden or host factors such as polymorphisms of Fc gamma receptor 3A (FcγRIIIA). In the CLL11 trial (NCT01010061), patients with previously untreated chronic lymphocytic leukaemia and comorbidities were randomised to receive either rituximab (type I anti-CD20 mAb) or obinutuzumab (type II and glycoengineered anti-CD20 mAb) in combination with chlorambucil for six cycles. Obinutuzumab led to faster depletion of B cells and achieved an improvement in outcome parameters such as response and progression-free survival compared with the rituximab arm, but was also associated with a higher rate and increased severity of IRR. To better understand the profile of risk for IRR in patients with CLL, we performed an exploratory analysis on data obtained from patients treated with either one of the two antibodies given in combination with chlorambucil. Methods: Patients from the prospective, randomized Phase III CLL11 study who received a first infusion of obinutuzumab (N=331) or rituximab (N=326) were included. Baseline pre-treatment risk factors thought to play a possible role in the development of IRR were identified a priori and included patient demographics, concurrent conditions and premedications, parameters of disease burden, prognostic factors, laboratory variables and FcγR genotype. Baseline values for mean fluorescence intensity (MFI) of CD20, gated on the circulating CLL clone, and MFI of CD16, gated on the natural killer (NK) cell population (CD56+16+) in peripheral blood were also available for N=510 patients. The primary outcome, development of an IRR with the first infusion, was defined as the occurrence of related signs and symptoms during or within 24 hours of administration of antibody. Due to the short-term nature of the initial IRR a multivariate logistical regression analysis was performed rather than a time to event analysis. Internal validation of this model, derived from a single dataset, was conducted using the established resampling technique of bootstrapping. This assessed the proportion of times each variable retained significance at α=0.10 when the model was fitted to bootstrapped samples of the dataset. Results: Patients that appeared to be at greater risk of developing any grade of IRR with the first infusion of rituximab or obinutuzumab were those treated with obinutuzumab, those with higher surface expression CD20 on CLL cells (MFI CD20) and greater FcγRIIIA (MFI CD16) on NK cells in peripheral blood, those with higher affinity FcγRIIIA genotype (VV), more pronounced neutropenia and splenomegaly at baseline (Table 1). Higher baseline absolute lymphocyte count and the presence of respiratory comorbidity also appeared to increase risk. All variables significant for inclusion in the model are shown in Table 1. Looking at those patients treated with obinutuzumab only, the most important determinant of risk was MFI CD20 (OR 3.6 95% CI 1.6-7.9). The impact of glucocorticoid premedication in reducing risk in obinutuzumab treated patients was not sufficient to reach significance, however, patients were not randomised to this intervention. Conclusion: This work identifies novel disease- and patient-specific biological variables that appear to play a role in the development of IRR in patients with CLL treated with anti-CD20 mAb, although the treatment received (obinutuzumab >rituximab) confers greatest risk. In addition to parameters of tumour burden, target antigen expression and gene polymorphisms of FcγR also appear to contribute to the risk of developing an IRR. Our results support the hypothesis that higher rates of IRR seen with the administration of obinutuzumab may result from stronger activation upon binding to CD20 on leukemic cells and subsequent enhanced cross-linking between CD20 expressing leukemic cells and FcγRIIIA bearing effector cells. Further studies involving obinutuzumab in this patient population will be needed to externally validate the results of this exploratory analysis. Disclosures Freeman: Roche Pharmaceuticals: clinical research fellowship supported by Roche Pharmaceuticals (secondment from Bart's) Other. Dixon:Roche Pharmaceuticals: Employment. Houghton:Roche Pharmaceuticals: Employment. Humphrey:Roche: Employment. Fingerle-Rowson:Roche Pharmaceuticals: Employment. Kreuzer:Roche Pharmaceuticals: Research Funding. Engelke:Roche: Travel grants Other. Hallek:Roche Pharmaceuticals: Consultancy, Research Funding, Speakers Bureau. Goede:Bristol Myers Squibb: Honoraria; Mundipharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Travel grants Other.

Iron Overload Diminishes the Effectiveness of the Innate Immune Response in Thalassemia Major: a Possible Mechanism for Increased Infection Risk.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4071-4071
Author(s):  
Patrick B Walter ◽  
Paul R Harmatz ◽  
Annie Higa ◽  
David Killilea ◽  
Nancy Sweeters ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Immune Response ◽  
Iron Overload ◽  
Board Of Directors ◽  
Innate Immune Response ◽  
Research Funding ◽  
Innate Immune ◽  
Healthy Controls ◽  
Advisory Committees ◽  
Fluorescent Intensity

Abstract Abstract 4071 Poster Board III-1006 Introduction Infection is the second most common cause of death in thalassemia. The innate immune system provides a first line of defense against infection and specificity depends on pattern recognition receptors (PRRs) specific to microbial pathogens. One class of PRR called the toll-like receptors (TLRs) are important for transducing the signal for bacterial Lipopolysaccharide (LPS), resulting not only in cytokine production, but also in the control of extracellular iron levels through production of neutrophil gelatinase associated Lipocalin (NGAL). However, the exact role that NGAL plays and the expression level of PRRs are unknown in thalassemia. Thus, the goal in these studies is to investigate the relationship of iron overload to the innate immune cell expression of PRRs and NGAL in thalassemia. Patients and Methods Fifteen transfusion dependent thalassemia patients (11 – 29 yrs old) participating in the combination trial of deferasirox (an oral iron chelator) and deferoxamine were enrolled (Novartis sponsored CICL670AUS24T). Fasting blood samples were obtained i) at baseline after a 72 hr washout of chelator, and ii) at 6 and 12 months on study. Five healthy controls (13 - 18 yrs old) were also enrolled. Fresh monocytes were isolated using antibody-linked magnetic microbeads (Miltenyi Biotec Inc). Highly enriched populations of CD14+ monocytes were verified by flow cytometry. The expression of TLR4, also examined by flow cytometry is reported as the mean fluorescent intensity (MFI). In patients with thalassemia, liver iron concentration (LIC) was analyzed by biomagnetic susceptibility (“SQUID”, Ferritometer®). The plasma levels of NGAL were analyzed by ELISA. Results At baseline the expression of monocyte TLR4 (mean 18.8 ± 3.5 MFI) was reduced 30% compared to the healthy controls (mean 26.9 ± 7.6 MFI, p<0.05). The expression of TLR4 over the follow-up period of 52 weeks in patients receiving intensive combination chelator therapy significantly increased 27% / year (7 MFI / year, p=0.005). Interestingly the expression of monocyte TLR4 was negatively correlated with LIC (r=-0.6, p=0.04). Finally, thalassemia patients at baseline have significantly higher levels of NGAL (80 ± 20 ng/ml) compared to controls (42 ± 15 ng/ml, p=0.01). Conclusions These preliminary studies support the hypothesis that iron burden has a negative impact on the innate immune response in thalassemia as demonstrated by the decreased expression of TLR4. After intensive chelation, the levels of TLR4 increased, indicating that decreased iron overload with chelation may improve innate immune responsiveness. Finally, the iron transport protein NGAL is significantly elevated in thalassemia possibly acting to prevent essential iron uptake by pathogenic bacteria. Disclosures: Harmatz: Novartis: Research Funding; Apotex : Membership on an entity's Board of Directors or advisory committees; Ferrokin: Membership on an entity's Board of Directors or advisory committees. Vichinsky:Novartis: Consultancy, Research Funding.

IGHV Unmutated Chronic Lymphocytic Leukemia (CLL) B Cells Are More Susceptible to Spontaneous Apoptosis Than Mutated CLL B Cells and Are Subject to the Anti-Apoptotic Effect of Environmental Signals

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2431-2431
Author(s):  
Marta Coscia ◽  
Francesca Pantaleoni ◽  
Chiara Riganti ◽  
Candida Vitale ◽  
Micol Rigoni ◽  
...  
Keyword(s):  
T Cells ◽  
B Cells ◽  
Board Of Directors ◽  
Stromal Cells ◽  
Peripheral Blood ◽  
Research Funding ◽  
Lymphocytic Leukemia ◽  
Leukemic Cells ◽  
Spontaneous Apoptosis ◽  
Advisory Committees

Abstract Abstract 2431 Chronic lymphocytic leukemia (CLL) is a clinically heterogeneous disease. A very reliable prognosticator is the mutational status of the tumor immunoglobulin heavy chain variable region (IGHV): patients with unmutated (UM) IGHV have a worse prognosis than patients with mutated (M) IGHV. Soluble factors (i.e. IL-4 and CD40L) and cellular components of the local microenvironment [i.e. bone marrow stromal cells (BMSC) and nurse-like cells (NLCs)] are important survival factors for CLL B cells. It is currently unknown to what extent UM and M CLL cells depend on the local microenvironment for their survival. We have evaluated the spontaneous apoptotic rate of tumor cells isolated by immunomagnetic selection from the peripheral blood (PB) of M and UM CLL patients. Both M and UM CLL B cells underwent spontaneous apoptosis throughout the culture period. However, the UM CLL B cells showed a significantly higher degree of apoptosis in 7-day cultures as compared to M CLL B cells. In both M and UM CLL B cells, high basal levels of Bcl-2 expression and NF-kB activity were detected. On day 7, the percentage of Bcl-2+ leukemic cells was significantly lower in UM than in M CLL B cells. EMSA test showed that NF-kB was totally inactivated in UM CLL B cells and only partially reduced in M CLL B cells. Quantitative analysis of RelA and RelB subunits showed that NF-kB inactivation in UM CLL B cells consisted in a strong reduction of both RelA and RelB nuclear expression. CD40L, IL-4 and stromal cells significantly improved UM CLL B cells viability and significantly recovered Bcl-2 expression. The protective effect exerted by these stimuli was totally independent from the recovery of NF-kB expression. Indeed, after 7 days of culture, the UM CLL B cells had completely lost the nuclear form of NF-kB, and none of the stimuli was capable of restoring it. We observed that UM CLL cells were less susceptible to spontaneous apoptosis when cultured as unfractionated peripheral blood mononuclear cells (M or UM PBMC) as compared to purified leukemic cells (M and UM CLL B cells). The reduced apoptosis detected in UM PBMC was accompanied by a retained expression of Bcl-2 and by a restored activity of NF-kB and suggested the presence of a pro-survival element in the peripheral blood of these patients. To investigate the role of NLC in rescuing UM CLL B cells from apoptosis we first evaluated whether M and UM PBMC generated NLC with the same efficiency. Unexpectedly, the former generated significantly higher numbers of NLC than UM PBMC. Despite the lack of generation of NLC, CLL B cells viability was very similar in the non-adherent fraction of M and UM PBMC on day 7 and 14 of culture. This observation ruled out a role for NLC in supporting UM CLL B cells survival. Conversely, a pro-survival effect on UM CLL B cells was exerted by autologous T cells. Indeed, a significant reduction in the apoptotic rate of leukemic cells was observed when purified UM CLL B cells were cultured in the presence of autologous peripheral blood T cells (UM CLL B cell/T cell co-cultures). NF-kB activity was completely lost in UM CLL B cells cultured for 7 days in medium alone whereas it was restored in UM CLL B cells / T cells co-cultures. The prosurvival effect of circulating T cells was exerted both in cell-to-cell contact and in trans-well condition and was associated to increased secretions of tumor necrosis factor-alpha (TNF-α), platelet-derived growth factor (PDGF)-BB and interleukin-8 (IL-8) as detected by analyses of supernatants through a Multiplex system. These data indicate that despite their more aggressive features, UM CLL B cells are more susceptible to spontaneous apoptosis and depend from environmental prosurvival signals. This vulnerability of UM CLL B cells can be exploited as a selective target of therapeutic interventions. Disclosures: 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. Massaia: Novartis: Honoraria, Research Funding.

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