Volume 129, Issue 26

Cover Figure: Pembrolizumab for relapsed CLL with and without Richter transformation. See the article by Ding et al.

WASHINGTON, June 29, 2017 – Welcome to “This Week in Blood,” a weekly snapshot of the hottest studies from each week’s issue of Blood, the official journal of the American Society of Hematology (ASH), hand-picked by Blood Editor-in-Chief Bob Löwenberg, MD, PhD, and Deputy Editor Nancy Berliner, MD.

Midostaurin approved for FLT3-mutated AML
Mark Levis presents a timely Spotlight review of the FLT3 inhibitor midostaurin, the first new agent approved for the treatment of acute myeloid leukemia (AML) in over 15 years.

Pembrolizumab in patients with CLL and Richter transformation or with relapsed CLL
Richter transformation (RT) occurs in ~15% of chronic lymphocytic leukemia (CLL) patients, is associated with p53 mutations, and responds poorly to all therapy, including Bruton tyrosine kinase inhibitors. Ding and colleagues report the first sustained responses to pembrolizumab in four out of nine of patients with RT, in contrast to no sustained responses in 16 relapsed CLL patients without RT.

Human CD62Ldim neutrophils identified as a separate subset by proteome profiling and in vivo pulse-chase labeling
Tak and colleagues study the proteome of a subset of neutrophils that downregulate CD62L, the L-selectin ligand, and demonstrate that these cells are distinct from classical segmented neutrophils and bands. This is a novel observation, countering the conception that these cells are derived from mature neutrophils that downmodulate CD62L as they age.

Platelet factor 4/heparin complexes present epitopes differently on solid-phase vs platelet surfaces
In a Letter to Blood, Nguyen and Greinacher report striking differences between reactivity of platelet factor 4/heparin complexes on solid-phase vs platelet surfaces, raising the important point that the degree of reactivity in standard enzyme-linked immunosorbent assay testing for heparin-induced thrombocytopenia (HIT) is not a good predictor of the severity of the potential in vivo HIT response.

FLI1 level during megakaryopoiesis affects thrombopoiesis and platelet biology
Paris-Trousseau syndrome is a platelet disorder associated with Jacobsen syndrome, caused by a partial deletion of chromosome 11q that deletes both FLI1 and ETS1, 2 transcription factors implicated in megakaryopoiesis. Vo et al use induced-pluripotent stem cells to demonstrate that the platelet defect is caused solely by FLI1 hemizygosity, despite concomitant deletion of ETS1.

ITIM receptors: more than just inhibitors of platelet activation
Coxon and colleagues provide a detailed review of the complex role of immunoreceptor tyrosine-based inhibition motif (ITIM)–containing receptors. Originally proposed as inhibitors of platelet activation, evidence from mouse models suggest that ITIM-containing receptors play both positive and negative roles in orchestrating the level of platelet activation.

Aryl hydrocarbon receptor inhibition promotes hematolymphoid development from human pluripotent stem cells
Angelos et al demonstrate that inhibiting the aryl hydrocarbon receptor (AHR) increases cytokine-induced human CD34+ hematopoietic stem cell expansion. Using human embryonic stem cells, they demonstrate that AHR regulates pluripotent stem cells (PSCs), suggesting that downmodulation of AHR can increase both hematopoietic and lymphoid subset development from PSCs.


This week's complete table of contents

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