ALBERT

Description: The majority of patients diagnosed with Philadelphia negative (Ph-) myeloproliferative neoplasms (MPNs) harbor somatic, gain-of-function mutations in JAK2, CALR or MPL. All of these mutations are associated with constitutive JAK/STAT signaling which confers a proliferative advantage to MPN cells and leads to malignant myeloid expansion at the expense of normal hematopoiesis. The bone marrow (BM) microenvironment in MPNs, particularly myelofibrosis (MF), is characterized by high concentrations of inflammatory cytokines, and we have previously shown that MF cells generate tumor necrosis factor alpha (TNF) in a JAK2-dependent manner. Elevated TNF promotes the survival of JAK2V617F mutant cells over their JAK2WT counterparts, creating a feedback loop in which the mutant cells enhance the inflammatory environment that supports their survival and expansion (Fleischman et al. Blood. 2011 Dec 8;118(24):6392-8). To determine which hematopoietic lineages contribute to increased levels of TNF in MPN, we measured intracellular TNF expression in immunophenotypically defined white blood or BM cells from MF patients and normal controls. TNF expression was relatively low in unstimulated cells. However, lipopolysaccharide (LPS) treatment induced a 16-fold greater increase of TNF expression in hematopoietic stem cells (HSCs) from MF patients relative to normal controls (p

Description: Molecular and cytogenetic alterations are involved in virtually every facet of acute myeloid leukemia (AML), including dysregulation of major signal-transduction pathways. The present study examines 5 phosphoproteins (pErk, pAkt, pS6, pStat3, and pStat5) in response to 5 cytokine/growth factors (stem cell factor [SCF], Flt-3/Flk-2 ligand [FL], granulocyte/macrophage-colony stimulating factor [GM-CSF], interleukin-3 [IL-3], and granulocyte-CSF [G-CSF]) within 7 immunophenotypically defined populations, spanning progenitor to mature myeloid/myelomonocytic cells in normal bone marrows with further comparison to AML samples. The normal cohort showed pathway-specific responses related to lineage, maturation, and stimulus. Heterogeneous-signaling responses were seen in homogeneous immunophenotypic subsets emphasizing the additive information of signaling. These profiles provided a critical baseline for detection of dysregulated signaling in AML falling into 4 broad categories, viz lack of response, increased activation, altered constitutive expression, and dysregulated response kinetics, easily identified in 10 of 12 AMLs. These studies clearly show robust and reproducible flow cytometry phosphoprotein analyses capable of detecting abnormal signal-transduction responses in AML potentially contributing to definitive reliable identification of abnormal cells. As functional correlates of underlying genetic abnormalities, signal-transduction abnormalities may provide more stable indicators of abnormal cells than immunophenotyping which frequently changes after therapy and disease recurrence.

Description: Activation of JAK2, frequently as a result of the JAK2V617F mutation, is a characteristic feature of the classical myeloproliferative neoplasms (MPN) polycythemia vera, essential thrombocythemia and myelofibrosis and thought to be responsible for the constitutional symptoms associated with these diseases. BMS-911543 is a JAK2 selective inhibitor that induces apoptosis in JAK2-dependent cell lines and inhibits the growth of CD34+ progenitor cells from patients with V617F+ MPN. To explore the clinical potential of this inhibitor, we tested BMS-911543 in a murine retroviral transduction – transplantation model of JAK2V617F MPN. Treatment was initiated at two dose levels (3 mg/kg and 10 mg/kg) when the hematocrit exceeded 70%. Following the first week, white blood cell counts were reduced to normal in the high dose group and were maintained well below the vehicle-treated mice throughout the study. However, BMS-911543 had no effect on red cell parameters. After 42 days of treatment, the proportion of JAK2V617F - positive cells in hematopoietic tissues was identical to controls or slightly increased compared to controls. Plasma concentrations of IL-6, IL-15, and TNFα were elevated in MPN mice and reduced in the high dose treatment group, while other cytokines were unchanged. Collectively, these results show that BMS-911543 has limited activity in this murine model of JAK2V617F – driven MPN and suggest that targeting JAK2 alone may be insufficient to achieve effective disease control. Disclosures Deininger: BMS, Novartis, Celgene, Genzyme, Gilead: Research Funding; BMA, ARIAD, Novartis, Incyte, Pfizer: Advisory Board, Advisory Board Other; BMS, ARIAD, Novartis, Incyte, Pfizer: Consultancy.

Description: The JAK2V617F mutation is a unifying feature in the majority of patients with myeloproliferative neoplasms (MPNs). The presence of JAK2V617 in a hematopoietic stem (HSC) or progenitor cell confers a proliferative advantage over native JAK2 counterparts. Several inflammatory cytokines are elevated in MPN patients and in murine models of JAK2V617F-driven MPN. In particular, expression of tumor necrosis factor alpha (TNF-α) is increased by constitutive JAK2 kinase activity and imparts a competitive advantage on JAK2V617Fexpressing cells. To identify cell types responsible for increased levels of TNF-α we performed intracellular cytokine staining in leukocytes from myelofibrosis (MF) patients and normal controls. Using a panel of markers to define cellular subsets we found expression of TNF-α was uniformly low in unstimulated cells. However, when cells were treated with lipopolysaccharide (LPS), TNF-α expression was 16-fold higher in HSCs of MF patients compared to normal controls (p

Description: B-cell chronic lymphocytic leukemia (CLL) is a malignancy of mature B-cells with a variable clinical course. Given the heterogeneity of disease course, identification of prognostic factors is imperative. One recently identified negative prognostic indicator in CLL is the T-cell tyrosine kinase ZAP70. ZAP70 is analogous to, and can functionally substitute for, the B-cell tyrosine kinase Syk and is activated following B cell receptor (BCR) crosslinking in CLL cells. However, the role of ZAP70 expression in CLL remains elusive. Utilizing flow cytometric analyses of signal transduction molecules, this study examined if ZAP70 expression affects signal transduction in CLL. Peripheral blood samples from ZAP70+ and ZAP70− CLL patients were analyzed. The levels of phosphorylated ERK, STAT5, and S6 (p-ERK, p-STAT5, p-S6) were measured by flow cytometry with and without BCR stimulation. Kinase inhibitors were used to verify the measured phosphorlyated protein levels. Increased constitutive levels of p-ERK, p-STAT5, and p-S6 were seen in ZAP70+ CLL cells as compared to ZAP70− CLL cells. BCR crosslinking gave variable responses in both ZAP70+ and ZAP70− CLL. The majority of ZAP70− cases showed no significant activation or a predominant activation of ERK with rare p-S6 activation. ZAP70+ cells showed activation of either, or both, ERK and S6 pathways and fewer showing no activation. In summary, though the role of ZAP70 in B cell signaling is poorly understood, expression of ZAP70 in CLL correlates with a constitutively active phenotype. Additionally, differential response in ZAP70+ versus ZAP70− cases following BCR crosslinking suggests a possible modulatory role of the BCR pathway. Current studies are underway to determine if these measures carry prognostic information and if the varying signal responses to BCR stimulation correlate with reported differences in apoptotic versus proliferative response.

Description: Abstract 5174 Background: Thrombosis is a well recognized complication in the myeloproliferative neoplasms (MPN), essential thrombocytosis (ET), polycythemia vera (PV), and primary myelofibrosis (PMF). The mechanism for thrombosis is not well-established, nor are there relevant biomarkers to predict risk and/or recurrence. Circulating cellular microparticles (MP) containing procoagulant tissue factor (TF) have been shown to correlate with thrombotic risk in many forms of cancer and cardiovascular diseases. To investigate the role of MP in the MPN, we studied 16 patients (ET=5; PV=6; PMF=2; post-ETMF=1, and MPN NOS=2) and compared results to 15 healthy subjects. Methods: Citrated blood samples were collected from the 16 MPN patients and 15 controls. Platelet poor plasma (PPP) was obtained by centrifuging at 1,500 G for 20 minutes. 50 μL of PPP was added to 200 μL PBS (without Mg/Ca) and centrifuged at 20,000 G for 10 minutes. The sediment containing MP was resuspended in 100μL of buffer for labeling with TF, CD41a (platelets), CD14 (monocytes), CD66b (neutrophils), and CD33 (myeloid lineage). Following incubation, PBS was added to the suspension to a volume of 1ml for flow cytometric analysis (LSR Fortessa, FlowJo software). Electronic triggering was done on side-scatter, and acquisition regions were defined based on sizing beads (0.3 to 1.0 micron) along with annexin A5 positivity. Using MP sediment, TF activity was measured using chromogenic assays (Actichrome TF ELISA, American Diagnostica,) and thrombin generation (TGT) was assayed (Technothrombin TGA, diaPharma), with results expressed as lag phase, velocity-index, peak thrombin, and area under the curve (AUC). The Wilcoxon-Rank Sum test was used to compare group differences (MPN vs. control) in median values. Results: Among the MPN patients, 7(44%) were male, and the median age was 60 years. 11 (69%) were JAK2 V617F positive, and 3 (19%) had a prior history of thrombosis (2 hepatic vein thromboses, 1 myocardial infarction). At the time of collection, 14 (93%) were on aspirin, 1 (6%) was on Coumadin, and 5 (31%) were on Hydroxyurea. The median total MP number was increased in MPN patients vs. controls (243580 vs. 83120; p=0.0057). The median percentage of TF-bearing MP's was also significantly greater in MPN patients compared to controls (35.5% vs. 12%; p=0.0003). When comparing MPN patients to controls, these TF-bearing MP were derived from CD14 (31.5% vs. 2%; p

Description: Abstract 3346 Abnormal hemostatic function in acute promyelocytic leukemia (APL) contributes to the bleeding and thrombotic complications, which account for much of the morbidity and mortality. Increased procoagulants (tissue factor (TF) and cancer procoagulant) and increased fibrinolytic components (annexin A2 and tPA) have been found in the blood of APL patients and in APL cell line NB4. However, their role in the pathogenesis of these complications is not clear. In recent years, increased numbers of circulating microparticles (MP) containing tissue factor have been observed in many cancer patients. This abstract describes the first study of MP in APL. Plasma samples were collected from 23 APL patients with 37 age-matched controls from healthy subjects. The APL patients were treated with a regimen of ATRA and anthracyclin according to the protocol of the International Consortium for APL (Sem. Thromb. Hemost. 2010, 369:17–924).The first sample was collected at diagnosis and second after induction therapy when molecular remission was obtained in all patients in this study. Platelet poor plasma (PPP) was obtained by centrifuging at 1,500 G for 20 minutes. 250 μL of PPP was centrifuged at 20,000 G for 10 minutes. The sediment containing MP was resuspended in 100μL of trisHCL buffer for fluorochrome-labelling with antibodies respectively against (1) human TF, (2) human annexin A2, (3) CD33, (4) human tPA, (5) human PAI-1 and (6) human annexin A5. Following incubation for 45 min, buffer was added to the suspension to a volume of 0.5 ml for FAC analysis using Coulter CyAn with Summit software. Electronic triggering was done on side-scatter, and samples were gated for size using enumeration beads (0.3 to 1.0 micron) and for annexin A5 positivity. Using MP sediment, the activities of TF, tPA and PAI-1 were respectively measured using chromogenic assays (Actichrome™ TF ELISA, American Diagnostica),(Spectrolyze™ tPA) and (Spectrolyze™ PAI-1). At diagnosis, FAC analysis showed tissue factor, PAI-1 and tPA in the MPs were significantly higher than controls with respective P values of 0.008, 0.0001 and 0.002. MPs with annexin A2 and CD33 in APL samples were not different from controls. After achieving molecular remission, the levels of tissue factor, CD33, and annexin A2 were significantly reduced with respective P values of 0.0001, 0.0007 and 0.05, while those of PAI-1 and tPA were not. Of the MP bearing tissue factor, 83% were associated with MP with CD33. This fraction was high at diagnosis and significantly reduced at remission (P=0.016). On the other hand, when assayed for activity, the TF was functional in all samples, but elevated in only one patient at diagnosis. Likewise, PAI-1 and tPA were functional but their respective activities were not elevated. Western blot showed formation of tPA/PAI-1 complex. These results showed that the increased number of TF-bearing MPs in APL plasma must be viewed with caution. Although the TF was functional, but its activity was not higher than in the controls. The same is true with PAI-1 and tPA. We hypothesize that inhibitors of TF, such as tissue factor pathway inhibitor, are present in APL patients mitigating the hypercoagulability, and that PAI-1 is complexed with tPA, reducing both their activities. Further studies testing this hypothesis are in progress. Disclosures: No relevant conflicts of interest to declare.