RalB uncoupled exocyst mediates endothelial Weibel-Palade body exocytosis.

Ras-like (Ral) GTPases play essential regulatory roles in many cellular processes, including exocytosis. Cycling between GDP- and GTP-bound states, Ral GTPases function as molecular switches and regulate effectors, specifically the multi-subunit tethering complex exocyst. Here, we show that Ral isoform RalB controls regulated exocytosis of Weibel-Palade bodies (WPBs), the specialized endothelial secretory granules that store hemostatic protein von Willebrand factor.

Spectrum From Clonal Hematopoiesis to Myelodysplastic Neoplasm/Syndromes and Other Myeloid Neoplasms.

Clonal hematopoiesis (CH) confers a high risk of aging-related diseases and hematologic malignancy. There are still significant knowledge gaps in identifying high-risk patients with CH and managing such patients. In this review, we focus on 3 areas: (1) the natural history of CH; (2) the risks of progression of CH, including CH of indeterminate potential, clonal cytopenia of undetermined significance, and therapy-related CH, to myeloid malignancy; and (3) the challenges and unmet needs of CH management and research.

Clonal Hematopoiesis: Origins and determinants of evolution.

The accrual of somatic mutations is a byproduct of aging. When a clone bearing a somatic genetic alteration, conferring comparative competitive advantage, displays sufficient outgrowth to become detectable amongst an otherwise polyclonal background in the hematopoietic system, this is called clonal hematopoiesis (CH). Somatic genetic alterations observed in CH include point mutations in cancer related genes, mosaic chromosomal alterations or a combination of these.

Older patients with chronic myeloid leukemia face suboptimal molecular testing and tyrosine kinase inhibitor adherence.

Tyrosine kinase inhibitor (TKI) use is critical in the care of patients with chronic myeloid leukemia (CML). Quantitative polymerase chain reaction (qPCR) testing for BCR-ABL1 every 3 months during the first year of TKI treatment is recommended to assure achievement of milestone response goals. Real-world evidence for the patterns of qPCR monitoring and TKI adherence in the older patient population is lacking.

Ipilimumab plus decitabine for patients with MDS or AML in posttransplant or transplant-naïve settings.

Two articles in this week’s issue focus on the use of ipilimumab and decitabine for patients with myelodysplasia (MDS) and acute myeloid leukemia (AML) before and after hematopoietic stem cell transplantation (HSCT) for high-risk disease. In the first article, Garcia et al report on the results of a phase 1 trial of the combination in 54 patients, demonstrating overall response rate of 52% in patients who are HSCT-naïve and 20% in patients post-HSCT; responses are usually short-lived. In the second article, Penter and colleagues characterize gene expression responses to therapy and conclude that decitabine acts directly to clear leukemic cells while ipilimumab acts on infiltrating lymphocytes in marrow and extramedullary sites.

Therapeutic Potential of Targeting the SUMO Pathway in Cancer.

SUMOylation is a dynamic and reversible post-translational modification, characterized more than 20 years ago, that regulates protein function at multiple levels. Key oncoproteins and tumor suppressors are SUMO substrates. In addition to alterations in SUMO pathway activity due to conditions typically present in cancer, such as hypoxia, the SUMO machinery components are deregulated at the genomic level in cancer.

Circulating Protein Disulfide Isomerase Is Associated with Increased Risk of Thrombosis in -Mutated Myeloproliferative Neoplasms.

Purpose: Thromboembolic events (TE) are the most common complications of myeloproliferative neoplasms (MPN). Clinical parameters, including patient age and mutation status, are used to risk-stratify patients with MPN, but a true biomarker of TE risk is lacking. Protein disulfide isomerase (PDI), an endoplasmic reticulum protein vital for protein folding, also possesses essential extracellular functions, including regulation of thrombus formation.

VWF maturation and release are controlled by 2 regulators of Weibel-Palade body biogenesis: exocyst and BLOC-2.

von Willebrand factor (VWF) is an essential hemostatic protein that is synthesized in endothelial cells and stored in Weibel-Palade bodies (WPBs). Understanding the mechanisms underlying WPB biogenesis and exocytosis could enable therapeutic modulation of endogenous VWF, yet optimal targets for modulating VWF release have not been established. Because biogenesis of lysosomal related organelle-2 (BLOC-2) functions in the biogenesis of platelet dense granules and melanosomes, which like WPBs are lysosome-related organelles, we hypothesized that BLOC-2-dependent endolysosomal trafficking is essential for WPB biogenesis and sought to identify BLOC-2-interacting proteins.

Alisertib plus induction chemotherapy in previously untreated patients with high-risk, acute myeloid leukaemia: a single-arm, phase 2 trial.

Background: Increased aurora A kinase (AAK) expression occurs in acute myeloid leukaemia; AAK inhibition is a promising therapeutic target in this disease. We therefore aimed to assess the activity of alisertib combined with 7 + 3 induction chemotherapy in previously untreated patients with high-risk acute myeloid leukaemia.

Methods: We did a single-arm, phase 2 trial of patients recruited from the Dana-Farber/Harvard Cancer Center in the USA.

The Interplay Between the Genetic and Immune Landscapes of AML: Mechanisms and Implications for Risk Stratification and Therapy.

AML holds a unique place in the history of immunotherapy by virtue of being among the first malignancies in which durable remissions were achieved with "adoptive immunotherapy," now known as allogeneic stem cell transplantation. The successful deployment of unselected adoptive cell therapy established AML as a disease responsive to immunomodulation. Classification systems for AML have been refined and expanded over the years in an effort to capture the variability of this heterogeneous disease and risk-stratify patients.

Germline NPM1 mutations lead to altered rRNA 2'-O-methylation and cause dyskeratosis congenita.

RNA modifications are emerging as key determinants of gene expression. However, compelling genetic demonstrations of their relevance to human disease are lacking. Here, we link ribosomal RNA 2'-O-methylation (2'-O-Me) to the etiology of dyskeratosis congenita.

A non-cell-autonomous role for Pml in the maintenance of leukemia from the niche.

Disease recurrence after therapy, due to the persistence of resistant leukemic cells, represents a fundamental problem in the treatment of leukemia. Elucidating the mechanisms responsible for the maintenance of leukemic cells, before and after treatment, is therefore critical to identify curative modalities. It has become increasingly clear that cell-autonomous mechanisms are not solely responsible for leukemia maintenance.

CtBP is an essential corepressor for BCL6 autoregulation.

The transcription repressor BCL6 plays an essential role in the formation and function of germinal centers (GCs). While normal B cells promptly shut off BCL6 when they exit the GC, many GC-derived B-cell lymphomas sustain BCL6 expression through chromosomal translocations and activating mutations. We have previously shown that a common effect of lymphoma-associated BCL6 gene alterations is to bypass a negative autoregulatory loop that controls its transcription.

Constitutively activated STAT3 promotes cell proliferation and survival in the activated B-cell subtype of diffuse large B-cell lymphomas.

Diffuse large B-cell lymphoma (DLBCL) consists of at least 2 phenotypic subtypes; that is, the germinal center B-cell-like (GCB-DLBCL) and the activated B-cell-like (ABC-DLBCL) groups. It has been shown that GCB-DLBCL responds favorably to chemotherapy and expresses high levels of BCL6, a transcription repressor known to play a causative role in lymphomagenesis. In comparison, ABC-DLBCL has lower levels of BCL6, constitutively activated nuclear factor-kappaB, and tends to be refractory to chemotherapy.