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Baseline cytogenetic studies at diagnosis remain the single most important determinant of outcome in patients with acute myeloid leukemia (AML). However, the prognostic role of the complete gamut of cytogenetic aberrations in AML patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) is currently undefined. In addition, their significance in conjunction with FLT3-ITD status has not been addressed thus far. Using the ALWP/EBMT registry we conducted a retrospective analysis to determine the clinical outcomes of AML patients undergoing allo-HSCT with respect to specific recurring cytogenetic abnormalities complemented with FLT3-ITD status. We analyzed a cohort consisting of 8558 adult AML patients who underwent allo-HSCT from either a matched sibling or a matched unrelated donor. Patients with inv(3)(q21q26)/t(3;3)(q21;q26), del(5q), monosomy 7, chromosome 17p abnormalities, t(10;11)(p11-14;q13-23), t(6;11)(q27;q23), as well as those patients with a monosomal or complex karyotype experienced significantly inferior leukemia-free survival (LFS) compared to patients with a normal karyotype. Trisomy 14, del(9q), and loss of chromosome X were associated with improved LFS rates. A novel prognostic model delineating 5 distinct groups incorporating cytogenetic complexity and FLT3-ITD status was constructed with significant prognostic implications. Our analysis supports the added prognostic significance of FLT3-ITD to baseline cytogenetics in patients undergoing allo-HSCT.

Acute leukemia is an aggressive blood malignancy with low survival rates. A high expression of stem-like programs in leukemias predicts poor prognosis and is assumed to act in an aberrant fashion in the phenotypically heterogeneous leukemia stem cell (LSC) population. A lack of suitable genome engineering tools that can isolate LSCs based on their stemness precludes their comprehensive examination and full characterization. We hypothesized that tagging endogenous stemness-regulatory regions could generate a genome reporter for the putative leukemia stemness-state. Our analysis revealed that the ERG  + 85 enhancer region can serve as a marker for stemness-state and a fluorescent lentiviral reporter was developed that can accurately recapitulate the endogenous activity. Using our novel reporter, we revealed cellular heterogeneity in several leukemia cell lines and patient-derived samples. Alterations in reporter activity were associated with transcriptomic and functional changes that were closely related to the hematopoietic stem cell (HSC) identity. Notably, the differentiation potential was skewed towards the erythro-megakaryocytic lineage. Moreover, an ERG  + 85 High fraction of AML cells could regenerate the original cellular heterogeneity and was enriched for LSCs. RNA-seq analysis coupled with in silico drug-screen analysis identified 4HPR as an effective inhibitor of ERG  + 85 High leukemia growth. We propose that further utilization of our novel molecular tool will identify crucial determinants of LSCs, thus providing a rationale for their therapeutic targeting.

The role of corticosterone (Cort), the immune system's major stress hormone, in the regulation of hematopoietic stem and progenitor cells (HSPCs) and their dynamic bone marrow (BM) microenvironment is currently unknown. We report that corticotropin-releasing factor receptor 1 (CRFR1) mutant mice with chronically low Cort levels showed aberrant HSPC regulation, having higher HSPC numbers and upregulation of the chemokine CXCL12, phenotypes that were restored by Cort supplementation. Expanded stromal progenitors known to support HSPCs were also observed in these low-Cort-containing mice. A similar phenotype was induced in wild-type (WT) mice by Metyrapone, a Cort synthesis inhibitor. Conversely, high Cort exposure induced HSPC apoptosis, reduced long-term BM repopulation and decreased stromal progenitor cell numbers. We documented circadian oscillations of Cort in WT BM but not in CRFR1 mutant mice, leading to diminished circadian BM CXCL12 fluctuations and increased number of circulating HSPCs in these mice. Finally, low Cort induced expansion of stromal progenitors, CXCL12 expression, HSPC proliferation and BM repopulation capacity, involving Notch1 signaling. This was associated with upregulation of the Notch ligand, Jagged1, in BM myeloid cells. Our results suggest that daily physiologic Cort oscillations are critical for balanced HSPC proliferation and function involving Notch1 signaling and their supportive BM microenvironment.