Search

A bstract Here we characterize the molecular and biological requirements for OCT4 plasticity induction in human skin derived fibroblasts (hFibs) that allows direct conversion of cell fate without iPSC formation. Our results indicate that adult hFibs not only require OCT4 but also short-term exposure to reprogramming media (RM) to successfully undergo direct conversion to early hematopoietic and neural progenitor fates. RM was found to be essential in this process and allowed for unique changes in global gene expression specific to the combined effects of OCT4 and treatment with reprogramming media to establish a plastic state. This molecular state of hFib plasticity was distinct from transient expression of a full complement of iPSC reprogramming factors consistent with a lack in molecular hallmarks of iPSC formation. Human Fib-derived OCT4 plastic cells display elevated levels of developmentally related genes associated with multiple lineages, but not those associated with pluripotency. In response to changes in the extracellular environment, plastic OCT4-expressing hFibs further activate genes involved in hematopoietic as well as tripotent neural progenitor biology that allow cell fate conversion. Our study provides a working definition of hFib-induced plasticity using OCT4 and a deconvoluted system to elucidate the process of direct cell fate reprogramming. S tem C ells 2014;32:2178-2187 [ABSTRACT FROM AUTHOR]

Histone variants (HVs) are a subfamily of epigenetic regulators implicated in embryonic development, but their role in human stem cell fate remains unclear. Here, we reveal that the phosphorylation state of the HV H2A.X (γH2A.X) regulates self-renewal and differentiation of human pluripotent stem cells (hPSCs) and leukemic progenitors. As demonstrated by CRISPR-Cas deletion, H2A.X is essential in maintaining normal hPSC behavior. However, reduced levels of γH2A.X enhances hPSC differentiation toward the hematopoietic lineage with concomitant inhibition of neural development. In contrast, activation and sustained levels of phosphorylated H2A.X enhance hPSC neural fate while suppressing hematopoiesis. This controlled lineage bias correlates to occupancy of γH2A.X at genomic loci associated with ectoderm versus mesoderm specification. Finally, drug modulation of H2A.X phosphorylation overcomes differentiation block of patient-derived leukemic progenitors. Our study demonstrates HVs may serve to regulate pluripotent cell fate and that this biology could be extended to somatic cancer stem cell control., Competing Interests: Declaration of interests The authors declare no competing financial interests, (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Despite successful remission induction, recurrence of acute myeloid leukemia (AML) remains a clinical obstacle thought to be caused by the retention of dormant leukemic stem cells (LSCs). Using chemotherapy-treated AML xenografts and patient samples, we have modeled patient remission and relapse kinetics to reveal that LSCs are effectively depleted via cell-cycle recruitment, leaving the origins of relapse unclear. Post-chemotherapy, in vivo characterization at the onset of disease relapse revealed a unique molecular state of leukemic-regenerating cells (LRCs) responsible for disease re-growth. LRCs are transient, can only be detected in vivo, and are molecularly distinct from therapy-naive LSCs. We demonstrate that LRC features can be used as markers of relapse and are therapeutically targetable to prevent disease recurrence., (Copyright © 2018 Elsevier Inc. All rights reserved.)

We completed a phase 1 dose-escalation trial to evaluate the safety of a dopamine receptor D2 (DRD2) antagonist thioridazine (TDZ), in combination with cytarabine. Thirteen patients 55 years and older with relapsed or refractory acute myeloid leukemia (AML) were enrolled. Oral TDZ was administered at 3 dose levels: 25 mg (n = 6), 50 mg (n = 4), or 100 mg (n = 3) every 6 hours for 21 days. Intermediate-dose cytarabine was administered on days 6 to 10. Dose-limiting toxicities (DLTs) included grade 3 QTc interval prolongation in 1 patient at 25 mg TDZ and neurological events in 2 patients at 100 mg TDZ (gait disturbance, depressed consciousness, and dizziness). At the 50-mg TDZ dose, the sum of circulating DRD2 antagonist levels approached a concentration of 10 μM, a level noted to be selectively active against human AML in vitro. Eleven of 13 patients completed a 5-day lead-in with TDZ, of which 6 received TDZ with hydroxyurea and 5 received TDZ alone. During this period, 8 patients demonstrated a 19% to 55% reduction in blast levels, whereas 3 patients displayed progressive disease. The extent of blast reduction during this 5-day interval was associated with the expression of the putative TDZ target receptor DRD2 on leukemic cells. These preliminary results suggest that DRD2 represents a potential therapeutic target for AML disease. Future studies are required to corroborate these observations, including the use of modified DRD2 antagonists with improved tolerability in AML patients. This trial was registered at www.clinicaltrials.gov as #NCT02096289., (© 2018 by The American Society of Hematology.)

Acute myeloid leukaemia (AML) is distinguished by the generation of dysfunctional leukaemic blasts, and patients characteristically suffer from fatal infections and anaemia due to insufficient normal myelo-erythropoiesis. Direct physical crowding of bone marrow (BM) by accumulating leukaemic cells does not fully account for this haematopoietic failure. Here, analyses from AML patients were applied to both in vitro co-culture platforms and in vivo xenograft modelling, revealing that human AML disease specifically disrupts the adipocytic niche in BM. Leukaemic suppression of BM adipocytes led to imbalanced regulation of endogenous haematopoietic stem and progenitor cells, resulting in impaired myelo-erythroid maturation. In vivo administration of PPARγ agonists induced BM adipogenesis, which rescued healthy haematopoietic maturation while repressing leukaemic growth. Our study identifies a previously unappreciated axis between BM adipogenesis and normal myelo-erythroid maturation that is therapeutically accessible to improve symptoms of BM failure in AML via non-cell autonomous targeting of the niche.