The N-terminal domain of human GATA1 prevents dyserythropoietic anemia and megakaryocyte dysplasia in vivo

We describe a child with dyserythropoietic anemia, thrombocytosis, functional platelet defect, and megakaryocyte dysplasia. We show that (i) this constellation of hematopoietic abnormalities was due to a germline mutation within the 5′ untranslated region (5′UTR) of globin transcription factor 1 (GATA1); (ii) the mutation impaired a 5′UTR GATA1 splicing site, with promoted production of the shortened GATA1 isoform lacking the N-terminus; and (iii) expression of the GATA1 N-terminus is restricted to erythroblasts and megakaryocytes in normal marrow, consistent with the patient's abnormal erythropoiesis and megakaryopoiesis. Our findings provide insights into the clinically relevant in vivo function of the N-terminal domain of GATA1 in human hematopoiesis

Burkitt lymphoma presenting as multifocal doughnut-shaped masses in the stomach of a patient with AIDS

https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0034-136581

Successful Modified Therapy in a Patient With Probable Infection-Associated Hemophagocytic Lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a rare, hyperinflammatory syndrome characterized by clinical signs and symptoms of extreme inflammation. In adults, HLH is typically a complication of infections, autoimmune diseases, and malignancies. While the disease is often fatal, classic management of HLH revolves around early diagnosis and initiation of protocolized therapy. We present a case of a previously healthy 56-year-old female who developed distributive shock requiring intubation, vasopressors, and continuous venovenous hemofiltration. In the setting of multiple infectious syndromes, severe cytopenias, and rising direct hyperbilirubinemia, her diagnosis of HLH was confirmed. Therapy was initiated with dexamethasone and two doses of reduced-intensity etoposide based on the patient's clinical course. Over the next few weeks, she continued to improve on dexamethasone monotherapy and has maintained remission up to the present with complete resolution of her cytopenias and return of baseline renal function. Our case highlights the variability in the management of probable infection-associated HLH (IHLH) with a good patient outcome. We demonstrate the potential to treat IHLH with partial protocols and minimal chemotherapeutics

Thrombocytopenia and disseminated histoplasmosis in immunocompetent adults

Disseminated histoplasmosis among immunocompetent patients is rare, but may be associated with clinically significant refractory thrombocytopenia. Platelet counts often return to normal levels following antifungal therapy. Therefore, the most important management of this refractory thrombocytopenia is the recognition and treatment of histoplasmosis infection

Ref-1/APE1 as Transcriptional Regulator and Novel Therapeutic Target in Pediatric T-cell Leukemia

The increasing characterization of childhood acute lymphoblastic leukemia (ALL) has led to the identification of multiple molecular targets, but have yet to translate into more effective targeted therapies, particularly for high-risk, relapsed T-cell ALL. Searching for master regulators controlling multiple signaling pathways in T-ALL, we investigated the multi-functional protein redox factor-1 (Ref-1/APE1), which acts as a signaling "node" by exerting redox regulatory control of transcription factors important in leukemia. Leukemia patients' transcriptome databases showed increased expression in T-ALL of Ref-1 and other genes of the Ref-1/SET interactome. Validation studies demonstrated that Ref-1 is expressed in high-risk leukemia T-cells, including in patient biopsies. Ref-1 redox function is active in leukemia T-cells, regulating the Ref-1 target NF-kB, and inhibited by the redox-selective Ref-1 inhibitor E3330. Ref-1 expression is not regulated by Notch signaling, but is upregulated by glucocorticoid treatment. E3330 disrupted Ref-1 redox activity in functional studies and resulted in marked inhibition of leukemia cell viability, including T-ALL lines representing different genotypes and risk groups. Potent leukemia cell inhibition was seen in primary cells from ALL patients, relapsed and glucocorticoid-resistant T-ALL cells, and cells from a murine model of Notch-induced leukemia. Ref-1 redox inhibition triggered leukemia cell apoptosis and down-regulation of survival genes regulated by Ref-1 targets. For the first time, this work identifies Ref-1 as a novel molecular effector in T-ALL and demonstrates that Ref-1 redox inhibition results in potent inhibition of leukemia T-cells, including relapsed T-ALL. These data also support E3330 as a specific Ref-1 small molecule inhibitor for leukemia

RIZ1 is potential CML tumor suppressor that is down-regulated during disease progression

BACKGROUND: RIZ1 expression and activity are reduced in many cancers. In AML cell lines and patient material, RIZ1 expression is reduced relative to normal bone marrow. In chronic myelogenous leukemia (CML), blastic transformation is associated with loss of heterozygosity in the region where RIZ1 is located. RIZ1 is a PR domain methyltransferase that methylates histone H3 lysine 9, a modification important for transcriptional repression. In CML blast crisis cell lines RIZ1 represses insulin-like growth factor-1 expression and autocrine signaling. Together these observations suggest that RIZ1 may have a role in the chronic phase to blast crisis transition in CML. RESULTS: In CML patient material, we observed that RIZ1 expression was decreased during progression from chronic phase to blast crisis. RIZ1 was expressed in mature myeloid and CD34(+ )cells demonstrating that decreased RIZ1 expression in blast crisis is not due to an increased immature cell population. Expression of RIZ1 CML blast crisis cell lines decreased proliferation, increased apoptosis, and enhanced differentiation. CONCLUSION: RIZ1 is a candidate tumor suppressor gene whose expression is decreased in blast crisis. Loss of RIZ1 activity results in decreased apoptosis and differentiation and enhanced proliferation. Together these results suggest that loss of RIZ1 expression will lead to an increase in myeloid blast cell population resulting in CML progression

Mitotic Errors Promote Genomic Instability and Leukemia in a Novel Mouse Model of Fanconi Anemia

© 2021 Edwards, Mitchell, Abdul-Sater, Chan, Sun, Sheth, He, Jiang, Yuan, Sharma, Czader, Chin, Liu, de Cárcer, Nalepa, Broxmeyer, Clapp and Sierra Potchanant.Fanconi anemia (FA) is a disease of genomic instability and cancer. In addition to DNA damage repair, FA pathway proteins are now known to be critical for maintaining faithful chromosome segregation during mitosis. While impaired DNA damage repair has been studied extensively in FA-associated carcinogenesis in vivo, the oncogenic contribution of mitotic abnormalities secondary to FA pathway deficiency remains incompletely understood. To examine the role of mitotic dysregulation in FA pathway deficient malignancies, we genetically exacerbated the baseline mitotic defect in Fancc-/- mice by introducing heterozygosity of the key spindle assembly checkpoint regulator Mad2. Fancc-/-;Mad2+/- mice were viable, but died from acute myeloid leukemia (AML), thus recapitulating the high risk of myeloid malignancies in FA patients better than Fancc-/-mice. We utilized hematopoietic stem cell transplantation to propagate Fancc-/-; Mad2+/- AML in irradiated healthy mice to model FANCC-deficient AMLs arising in the non-FA population. Compared to cells from Fancc-/- mice, those from Fancc-/-;Mad2+/- mice demonstrated an increase in mitotic errors but equivalent DNA cross-linker hypersensitivity, indicating that the cancer phenotype of Fancc-/-;Mad2+/- mice results from error-prone cell division and not exacerbation of the DNA damage repair defect. We found that FANCC enhances targeting of endogenous MAD2 to prometaphase kinetochores, suggesting a mechanism for how FANCC-dependent regulation of the spindle assembly checkpoint prevents chromosome mis-segregation. Whole-exome sequencing revealed similarities between human FA-associated myelodysplastic syndrome (MDS)/AML and the AML that developed in Fancc-/-; Mad2+/- mice. Together, these data illuminate the role of mitotic dysregulation in FA-pathway deficient malignancies in vivo, show how FANCC adjusts the spindle assembly checkpoint rheostat by regulating MAD2 kinetochore targeting in cell cycle-dependent manner, and establish two new mouse models for preclinical studies of AML.This work was supported by the NIH R01-HL132921-01A1 award (DWC), St. Baldrick’s Foundation Scholar award (GN), Heroes Foundation (GN), the Bone Marrow Failure Research Fund at Riley Children’s Foundation (GN), NIH T32 HL007910 “Basic Science Studies on Gene Therapy of Blood Diseases” grant (ES), NIH Diversity Supplement 3R01HL132921-03S1 (ES), and NCI 1F30CA200227-01A1 fellowship (DE)

Cryopreservation Preserves Cell-Type Composition and Gene Expression Profiles in Bone Marrow Aspirates From Multiple Myeloma Patients

Single-cell RNA sequencing reveals gene expression differences between individual cells and also identifies different cell populations that are present in the bulk starting material. To obtain an accurate assessment of patient samples, single-cell suspensions need to be generated as soon as possible once the tissue or sample has been collected. However, this requirement poses logistical challenges for experimental designs involving multiple samples from the same subject since these samples would ideally be processed at the same time to minimize technical variation in data analysis. Although cryopreservation has been shown to largely preserve the transcriptome, it is unclear whether the freeze-thaw process might alter gene expression profiles in a cell-type specific manner or whether changes in cell-type proportions might also occur. To address these questions in the context of multiple myeloma clinical studies, we performed single-cell RNA sequencing (scRNA-seq) to compare fresh and frozen cells isolated from bone marrow aspirates of six multiple myeloma patients, analyzing both myeloma cells (CD138+) and cells constituting the microenvironment (CD138-). We found that cryopreservation using 90% fetal calf serum and 10% dimethyl sulfoxide resulted in highly consistent gene expression profiles when comparing fresh and frozen samples from the same patient for both CD138+ myeloma cells (R ≥ 0.96) and for CD138- cells (R ≥ 0.9). We also demonstrate that CD138- cell-type proportions showed minimal alterations, which were mainly related to small differences in immune cell subtype sensitivity to the freeze-thaw procedures. Therefore, when processing fresh multiple myeloma samples is not feasible, cryopreservation is a useful option in single-cell profiling studies

Differential Stem and Progenitor Cell Trafficking by Prostaglandin E2

SUMMARY To maintain lifelong production of blood cells, hematopoietic stem cells (HSC) are tightly regulated by inherent programs and extrinsic regulatory signals received from their microenvironmental niche. Long-term repopulating HSC (LT-HSC) reside in several, perhaps overlapping, niches that produce regulatory molecules/signals necessary for homeostasis and increased output following stress/injury 1–5. Despite significant advances in specific cellular or molecular mechanisms governing HSC/niche interactions, little is understood about regulatory function within the intact mammalian hematopoietic niche. Recently, we and others described a positive regulatory role for Prostaglandin E2 (PGE2) on HSC function ex vivo 6,7. While exploring the role of endogenous PGE2 we unexpectedly observed hematopoietic egress after nonsteroidal anti-inflammatory drug (NSAID) treatment. Surprisingly, this was independent of the SDF-1/CXCR4 axis. Stem and progenitor cells were found to have differing mechanisms of egress, with HSC transit to the periphery dependent on niche attenuation and reduction in the retentive molecule osteopontin (OPN). Hematopoietic grafts mobilized with NSAIDs had superior repopulating ability and long-term engraftment. Treatment of non-human primates and healthy human volunteers confirmed NSAID-mediated egress in higher species. PGE2 receptor knockout mice demonstrated that progenitor expansion and stem/progenitor egress resulted from reduced EP4 receptor signaling. These results not only uncover unique regulatory roles for EP4 signaling in HSC retention in the niche but also define a rapidly translatable strategy to therapeutically enhance transplantation