Medicine JournalFeeds

Calcium blockers decrease the bortezomib resistance in mantle cell lymphoma (MCL) via manipulation of tissue transglutaminase activities.

Blood. 2012 Jan 31;

Authors: Jung HJ, Chen Z, Wang M, Fayad L, Romaguera J, Kwak LW, McCarty N

Abstract

Although bortezomib is clinically approved for the treatment of Mantle Cell Lymphoma (MCL), only limited effects have been demonstrated. To improve survival for bortezomib-resistant patients it is necessary to develop new therapeutic strategies. In this report, we utilized biochemical and molecular methodologies to demonstrate tissue transglutaminase (TG) activates downstream NF-KB signaling pathways. The signaling axis from TG to NF-κB could be a new therapeutic target to overcome bortezomib resistance in MCL. TG2 is a calcium-dependent protein crosslinking enzyme, and was reported to over-expressed in various cancer cells. MCL expressed elevated levels of TG2, and the modification of TG2 activities altered NF-κB expression and downstream signaling in MCL cells. When the TG2 signaling was inhibited via calcium blockers, the combination of a calcium blocker perillyl alcohol (POH) with bortezomib suppressed NF-κB expression and improved the cytotoxicity of bortezomib in MCL cells. Our study is the first to show the expression of TG2 and the contribution of TG2 to NF-κB signaling in MCL. TG2 inhibition can be an alternative target as anti-MCL therapy, and calcium blockers may be effective combinatory drugs with bortezomib to overcome the bortezomib resistance of MCL.

PMID: 22294726 [PubMed - as supplied by publisher]

In vivo effects of eltrombopag on platelet function in immune thrombocytopenia: no evidence of platelet activation.

Blood. 2012 Jan 31;

Authors: Psaila B, Bussel JB, Linden MD, Babula B, Li Y, Barnard MR, Tate C, Mathur K, Frelinger AL, Michelson AD

Abstract

The effects of eltrombopag, a thrombopoietin-receptor agonist, on platelet function in ITP are not fully characterized. This study used whole blood flow cytometry to examine platelet function in 20 patients receiving eltrombopag treatment at days 0, 7 and 28. Platelet surface expression of activated GPIIb/IIIa, P-selectin and GPIb was measured with and without low and high ADP and TRAP concentrations. Prior to eltrombopag treatment with no ex vivo agonist, platelet activation was higher in ITP patients than controls. A decrease in GPIb and activated GPIIb/IIIa without added agonist was observed in eltrombopag responders, resulting in similar levels to healthy controls. Expression of P-selectin and activated GPIIb/IIIa in response to high-dose ADP was lower during eltrombopag treatment than at baseline and lower than controls; TRAP-induced GPIb expression also decreased. Eltrombopag led to a slight increase in platelet reactivity to TRAP only in responders to eltrombopag but not to levels above those in controls; whole blood experiments demonstrated that this increase was likely due to higher platelet counts rather than higher platelet reactivity. In conclusion, although thrombocytopenic ITP patients have higher baseline platelet activation than controls, eltrombopag did not cause platelet activation or hyper-reactivity, irrespective of whether the platelet count increased.

PMID: 22294727 [PubMed - as supplied by publisher]

Identification of TRIB1 R107L gain-of-function mutation in human acute megakaryocytic leukemia.

Blood. 2012 Jan 31;

Authors: Yokoyama T, Toki T, Aoki Y, Kanezaki R, Park MJ, Kanno Y, Takahara T, Yamazaki Y, Ito E, Hayashi Y, Nakamura T

Abstract

Trib1 has been identified as a myeloid oncogene in a murine leukemia model. Here we identified a TRIB1 somatic mutation in a human case of Down syndrome-related acute megakaryocytic leukemia (DS-AMKL). The mutation was observed at well conserved arginine 107 residue in the pseudokinase domain. This R107L mutation remained in leukocytes of the remission stage in which GATA1 mutation disappeared, suggesting the TRIB1 mutation is an earlier genetic event in leukemogenesis. The bone marrow transfer experiment showed that AML development was accelerated by transducing murine bone marrow cells with the R107L mutant in which enhancement of ERK phosphorylation and C/EBPα degradation by Trib1 expression was even greater than in those expressing wild type. These results suggest that TRIB1 may be a novel important oncogene for DS-AMKL.

PMID: 22294728 [PubMed - as supplied by publisher]

Caspase-9 mediates the apoptotic death of megakaryocytes and platelets, but is dispensable for their generation and function.

Blood. 2012 Jan 31;

Authors: White MJ, Schoenwaelder SM, Josefsson EC, Jarman KE, Henley KJ, James C, Debrincat MA, Jackson SP, Huang DC, Kile BT

Abstract

Apoptotic caspases, including Caspase-9, are thought to facilitate platelet shedding by megakaryocytes. They are known to be activated during platelet apoptosis, and have also been implicated in platelet hemostatic responses. However, the precise requirement for, and the regulation of, apoptotic caspases have never been defined in either megakaryocytes or platelets. To establish the role of caspases in platelet production and function, we generated mice lacking Caspase 9 in their hematopoietic system. We demonstrate that both megakaryocytes and platelets possess a functional apoptotic caspase cascade downstream of Bcl-2 family-mediated mitochondrial damage. Caspase-9 is the initiator caspase, and its loss blocks effector caspase activation. Surprisingly, steady state thrombopoiesis is unperturbed in the absence of Caspase-9, indicating that the apoptotic caspase cascade is not required for platelet production. In platelets, loss of Caspase-9 confers resistance to the BH3 mimetic ABT-737, blocking PS exposure and delaying ABT-737-induced thrombocytopenia in vivo. Despite this, steady state platelet life span is normal. Casp9(-/-) platelets are fully capable of physiological hemostatic responses and functional regulation of adhesive integrins in response to agonist. These studies demonstrate that the apoptotic caspase cascade is required for the efficient death of megakaryocytes and platelets, but is dispensable for their generation and function.

PMID: 22294729 [PubMed - as supplied by publisher]

Oligodeoxynucleotides stabilize Helios-expressing Foxp3+ human T regulatory cells during in vitro expansion.

Blood. 2012 Jan 31;

Authors: Kim YC, Bhairavabhotla R, Yoon J, Golding A, Thornton AM, Tran DQ, Shevach EM

Abstract

Foxp3(+) regulatory T cells (Tregs) maintain self-tolerance and adoptive therapy utilizing Foxp3(+) Treg has been proposed as treatment for autoimmune diseases. The clinical use of Tregs will require large numbers of cells and methods for in vitro expansion of Treg are being developed. Foxp3(+) Tregs can be divided into two subpopulations based on expression of the transcription factor, Helios. Foxp3(+)Helios(+) Tregs (70%) are thymic-derived, while Foxp3(+)Helios(-) Tregs (30%) are induced in the periphery. Foxp3(+)Helios(+) Tregs differ from Foxp3(+)Helios(-) Tregs in terms of epigenetic changes at the Foxp3 locus, their capacity to produce effector cytokines, and their stability of Foxp3 expression upon days to weeks of expansion in vitro. Addition of a 25mer DNA oligonucleotide of random composition for a short period during the expansion of Foxp3(+) Tregs in vitro results in prolonged stabilization of the Foxp3(+)Helios(+) subpopulation and yields an optimal population for use in cellular biotherapy.

PMID: 22294730 [PubMed - as supplied by publisher]

A prospective evaluation of degranulation assays in the rapid diagnosis of familial hemophagocytic syndromes.

Blood. 2012 Jan 31;

Authors: Bryceson YT, Pende D, Maul-Pavicic A, Gilmour KC, Ufheil H, Vraetz T, Chiang SC, Marcenaro S, Meazza R, Bondzio I, Walshe D, Janka G, Lehmberg K, Beutel K, Zur Stadt U, Binder N, Arico M, Moretta L, Henter JI, Ehl S

Abstract

Familial hemophagocytic lymphohistocytosis (FHL) is a life-threatening disorder of immune regulation caused by defects in lymphocyte cytotoxicity. Rapid differentiation of primary, genetic forms from secondary forms of hemophagocytic lymphohistiocytosis (HLH) is crucial for treatment decisions. We prospectively evaluated the performance of degranulation assays based on surface upregulation of CD107a on NK cells and CTL in a cohort of 494 patients referred for evaluation for suspected HLH. Seventy-five of 77 patients (97%) with FHL3-5 and 11/13 patients (85%) with Griscelli syndrome type 2 or Chediak-Higashi syndrome had abnormal resting NK cell degranulation. In contrast, NK cell degranulation was normal in 14/16 patients (88%) with X-linked lymphoproliferative disease and in 8/14 patients (57%) with FHL2, who were identified by diminished intracellular SAP, XIAP, and perforin expression, respectively. Among 66 patients with a clinical diagnosis of secondary HLH, 13/59 (22%) had abnormal resting NK degranulation, while 0/43 had abnormal degranulation using IL-2 activated NK cells. Active disease or immunosuppressive therapy did not impair the assay performance. Overall, resting NK cell degranulation below 5% provided a sensitivity for a genetic degranulation disorder of 96% and a specificity of 88%. Thus, degranulation assays allowed a rapid and reliable classification of patients, benefitting treatment decisions.

PMID: 22294731 [PubMed - as supplied by publisher]

The phenotype of human STK4 deficiency.

Blood. 2012 Jan 31;

Authors: Abdollahpour H, Appaswamy G, Kotlarz D, Diestelhorst J, Beier R, Schäffer AA, Gertz EM, Schambach A, Kreipe HH, Pfeifer D, Engelhardt KR, Rezaei N, Grimbacher B, Lohrmann S, Sherkat R, Klein C

Abstract

We describe a novel clinical phenotype associating T- and B-cell lymphopenia, intermittent neutropenia, and atrial septal defects in three members of a consanguineous kindred. Their clinical histories included recurrent bacterial infections, viral infections, mucocutaneous candidiasis, cutaneous warts and skin abscesses. Homozygosity mapping and candidate gene sequencing revealed a homozygous premature termination mutation in the gene STK4 (serine threonine kinase 4, formerly having the symbol MST1). STK4 is the human ortholog of Drosophila Hippo, the central constituent of a highly conserved pathway controlling cell growth and apoptosis. STK4-deficient lymphocytes and neutrophils exhibit enhanced loss of mitochondrial membrane potential and increased susceptibility to apoptosis. STK4 deficiency is a novel human primary immunodeficiency syndrome.

PMID: 22294732 [PubMed - as supplied by publisher]

How I anticoagulate in 2012, new and old anticoagulant agents, and when and how to switch.

Blood. 2012 Feb 1;

Authors: Schulman S, Crowther MA

Abstract

Two novel oral anticoagulants, dabigatran and rivaroxaban, have recently been approved. They differ in many ways from warfarin, including rapid onset of action, shorter half-life, fewer drug-drug interactions, lack of need for monitoring and no need for titration or dose adjustments. These novel agents represent a landmark shift in anticoagulant care, however, many aspects of their use will be unfamiliar to practicing clinicians, despite the imminent widespread use of these agents in the community. The management of these anticoagulants when transitioning from or back to warfarin, around surgery or in case of major hemorrhage requires knowledge of their pharmacokinetics and mechanism of action. Unfortunately there is a limited evidence base to inform decisions around management of these agents. We present our practice in these settings supported, where available, with literature evidence.

PMID: 22302737 [PubMed - as supplied by publisher]

Human CD300a binds to phosphatidylethanolamine and phosphatidylserine and modulates the phagocytosis of dead cells.

Blood. 2012 Feb 1;

Authors: Simhadri VR, Andersen JF, Calvo E, Choi SC, Coligan JE, Borrego F

Abstract

CD300a is an immunoreceptor tyrosine-based inhibitory motif (ITIM) containing molecule that belongs to the CD300 family of paired activating/inhibitory receptors. It has been shown that its ligation inhibits activation signals on cells of both myeloid and lymphoid lineages. The ligands for CD300a have not been identified. Here, we show that a CD300a-Ig fusion protein specifically binds to apoptotic cells that are evolutionary apart, such as human and insect cells, suggesting that the ligand has to be conserved. Using surface plasmon resonance, ultracentrifugation, ELISA and reporter cell assays we identified phosphatidylethanolamine (PE) and phosphatidylserine (PS), two phospholipids that translocate to the outer leaflet of the plasma membrane of dead cells, as the ligands for CD300a. Mutational and structural modeling studies identified residues that are involved in the binding of CD300a to PE and PS and that form a cavity where the hydrophilic heads of PE and PS can penetrate. CD300a down-regulates the uptake of apoptotic cells by macrophages and its ectopic expression in CD300a negative cell lines also decreased the engulfment of dead cells. Collectively, our results indicate that PE and PS are ligands for CD300a and that this interaction plays an important role in regulating the removal of dead cells.

PMID: 22302738 [PubMed - as supplied by publisher]

B cell-intrinsic deficiency of the Wiskott-Aldrich syndrome protein causes severe abnormalities of the peripheral B-cell compartment in mice.

Blood. 2012 Feb 1;

Authors: Recher M, Burns SO, de la Fuente MA, Volpi S, Dahlberg C, Walter JE, Moffitt K, Mathew D, Honke N, Lang PA, Patrizi L, Falet H, Keszei M, Mizui M, Csizmadia E, Candotti F, Nadeau K, Bouma G, Delmonte OM, Frugoni F, Fomin AB, Buchbinder D, Lundequist EM, Massaad MJ, Tsokos GC, Hartwig J, Manis J, Terhorst C, Geha RS, Snapper S, Lang KS, Malley R, Westerberg L, Thrasher AJ, Notarangelo LD

Abstract

The Wiskott Aldrich syndrome (WAS) is caused by mutations in the WAS gene that encodes for a protein (WASp) involved in cytoskeleton organization in hematopoietic cells. Several distinctive abnormalities of T, B and NK lymphocytes, dendritic cells (DCs) and phagocytes have been demonstrated in WASp-deficient patients and mice, however the in vivo consequence of WASp deficiency within individual blood cell lineages has not been definitively evaluated. By conditional gene deletion we have generated mice with selective deficiency of WASp in the B cell lineage (B/WcKO mice). We show that this is sufficient to cause a severe reduction of marginal zone B cells and inability to respond to type II T-independent antigens thereby recapitulating phenotypic features of complete WASp deficiency. In addition, B/WcKO mice demonstrate prominent signs of B cell dysregulation, as indicated by an increase in serum IgM levels, expansion of germinal center B cells and plasma cells, and elevated autoantibody production. These findings are accompanied by hyperproliferation of WASp-deficient follicular and germinal center B cells in heterozygous B/WcKO mice in vivo and excessive differentiation of WASp-deficient B cells into class-switched plasmablasts in vitro, suggesting that WASp-dependent B cell-intrinsic mechanisms critically contribute to WAS-associated autoimmunity.

PMID: 22302739 [PubMed - as supplied by publisher]