In Vitro Megakaryocyte Differentiation and Proplatelet Formation in Ph-Negative Classical Myeloproliferative Neoplasms: Distinct Patterns in the Different Clinical Phenotypes

Background: Ph-negative myeloproliferative neoplasms (MPNs) are clonal disorders that include primary myelofibrosis (PMF), polycythemia vera (PV) and essential thrombocythemia (ET). Although the pathogenesis of MPNs is still incompletely understood, an involvement of the megakaryocyte lineage is a distinctive feature. Methodology/Principal Findings: We analyzed the in vitro megakaryocyte differentiation and proplatelet formation in 30 PMF, 8 ET, 8 PV patients, and 17 healthy controls (CTRL). Megakaryocytes were differentiated from peripheral blood CD34+ or CD45+ cells in the presence of thrombopoietin. Megakaryocyte output was higher in MPN patients than in CTRL with no correlation with the JAK2 V617F mutation. PMF-derived megakaryocytes displayed nuclei with a bulbous appearance, were smaller than ET- or PV-derived megakaryocytes and formed proplatelets that presented several structural alterations. In contrast, ET- and PV-derived megakaryocytes produced more proplatelets with a striking increase in bifurcations and tips compared to both control and PMF. Proplatelets formation was correlated with platelet counts in patient peripheral blood. Patients with pre-fibrotic PMF had a pattern of megakaryocyte proliferation and proplatelet formation that was similar to that of fibrotic PMF and different from that of ET. Conclusions/Significance: In conclusion, MPNs are associated with high megakaryocyte proliferative potential. Profound differences in megakaryocyte morphology and proplatelet formation distinguish PMF, both fibrotic and prefibrotic, from ET and PV

The BH3-mimetic ABT-737 effectively kills acute myeloid leukemia initiating cells

The anti-apoptotic proteins Bcl-XL and Bcl-2 are abundantly expressed in hematopoietic stem cells and/or progenitor cells. Furthermore, leukemic cells expressing these proteins are enriched in minimal residual disease cell populations. This prompted us to test the BH3-mimetic compound ABT-737 for its ability to eradicate putative leukemic stem cells. ABT-737 demonstrated potent cytotoxic effects in all patient samples tested. The efficacy of ABT-737 against AML blasts and the primitive CD34+/CD38− population was equal and independent of sensitivity to cytarabine/daunorubicin. These results, together with previously reported synergistic effects of ABT-737 with chemotherapeutics make BH3-mimetics promising candidates for future AML treatment regimens

VS411 reduced immune activation and HIV-1 RNA levels in 28 days: randomized proof-of-concept study for antiviral-hyperactivation limiting therapeutics.

A new class of antiretrovirals, AntiViral-HyperActivation Limiting Therapeutics (AV-HALTs), has been proposed as a disease-modifying therapy to both reduce Human Immunodeficiency Virus Type 1 (HIV-1) RNA levels and the excessive immune activation now recognized as the major driver of not only the continual loss of CD4(+) T cells and progression to Acquired Immunodeficiency Syndrome (AIDS), but also of the emergence of both AIDS-defining and non-AIDS events that negatively impact upon morbidity and mortality despite successful (ie, fully suppressive) therapy. VS411, the first-in-class AV-HALT, combined low-dose, slow-release didanosine with low-dose hydroxycarbamide to accomplish both objectives with a favorable toxicity profile during short-term administration. Five dose combinations were administered as VS411 to test the AV-HALT Proof-of-Concept in HIV-1-infected subjects.Multinational, double-blind, 28-day Phase 2a dose-ranging Proof-of-Concept study of antiviral activity, immunological parameters, safety, and genotypic resistance in 58 evaluable antiretroviral-naïve HIV-1-infected adults. Randomization and allocation to study arms were carried out by a central computer system. Results were analyzed by ANOVA, Kruskal-Wallis, ANCOVA, and two-tailed paired t tests.VS411 was well-tolerated, produced significant reductions of HIV-1 RNA levels, increased CD4(+) T cell counts, and led to significant, rapid, unprecedented reductions of immune activation markers after 28 days despite incomplete viral suppression and without inhibiting HIV-1-specific immune responses. The didanosine 200 mg/HC 900 mg once-daily formulation demonstrated the greatest antiviral efficacy (HIV-1 RNA: -1.47 log(10) copies/mL; CD4(+) T cell count: +135 cells/mm(3)) and fewest adverse events.VS411 successfully established the Proof-of-Concept that AV-HALTs can combine antiviral efficacy with rapid, potentially beneficial reductions in the excessive immune system activation associated with HIV-1 disease. Rapid reductions in markers of immune system hyperactivation and cellular proliferation were obtained despite the fact that VS411 did not attain maximal suppression of HIV RNA, suggesting this effect was due to the HALT component.ITEudraCT 2007-002460-98

Analysis of proplatelet architecture.

<p>(A) Representative picture of differently organized proplatelet revealed by alpha tubulin staining (green) of controls (I), PMF (II–III), ET (IV) and PV (V). Nuclei are counterstained with Hoechst 33258 (blu). Scale bars are 15 µm. (B) Proplatelet bifurcations (means ± SD), which were identified upon immunostaining with an antibody against alpha tubulin. (C) Proplatelet tips (means ± SD), which were identified as coiled coil formations localized at the end of proplatelet branches. *p<0.05.</p

Box-and-whisker plots of megakaryocyte output in suspension cultures.

<p>CD45⁺ (A) and CD34⁺ (B) cells from peripheral blood were sorted as described in Methods and cultured for 14 days. At the end of the cultures, the yield of megakaryocyte was calculated as output of CD41⁺ cells with megakaryocyte morphology. CTRL: healthy controls; PMF: primary myeolofibrosis; ET: essential thrombocytemia; PV polycytemia vera. *p<0.01.</p

Epidemiological and clinical data of patient and control populations^*.

<p>*Age, Hb, Hct, WBC, and Plt counts are expressed as median (range). Diagnosis was made according to WHO criteria (see text for details). Values reported in the table are those at the moment in which blood was drawn for experiments. PMF and ET patients were at diagnosis or before the beginning of any cytoreductive therapy. Patients with PV were all under treatment with phlebotomy (but not with cytostatic therapy) in order to try to lower their Hct below 45% (males) or 42% (females). Healthy CTRLs hematological values were assessed before treatment with G-CSF (see text for details).</p