Blood
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Induction of red blood cell (RBC) fetal hemoglobin (HbF; α2γ2) ameliorates the pathophysiology of sickle cell disease (SCD) by reducing the concentration of sickle hemoglobin (HbS; α2βS2) to inhibit its polymerization. Hydroxyurea (HU), the only US Food and Drug Administration (FDA)-approved drug for SCD, acts in part by inducing HbF; however, it is not fully effective, reflecting the need for new therapies. Whole-exome sequence analysis of rare genetic variants in SCD patients identified FOXO3 as a candidate regulator of RBC HbF. ⋯ Combined HU and metformin treatment induced HbF additively and reversed the arrest in erythroid maturation caused by HU treatment alone. HbF induction by metformin in erythroid precursors was dependent on FOXO3 expression and did not alter expression of BCL11A, MYB, or KLF1. Collectively, our data implicate FOXO3 as a positive regulator of γ-globin expression and identify metformin as a potential therapeutic agent for SCD.
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Previous studies have suggested that longer donor leukocyte telomere length (TL) is associated with improved survival after hematopoietic cell transplantation (HCT) in severe aplastic anemia (SAA). This study aimed to determine whether cell-specific lymphocyte TL is associated with certain post-HCT causes of death. We used flow cytometry and fluorescence in situ hybridization to measure TL in donor total lymphocytes and subsets: naïve enriched T cells (CD45RA+CD20-), memory enriched T cells (CD45RA-CD20-), natural killer (NK) fully differentiated T cells (CD45RA+CD57+), and B cells (CD45RA+CD20+). ⋯ Donor TL in other tested lymphocyte subsets was not statistically significantly associated with death resulting from graft-versus-host disease or graft failure (P > .05). However, a trend toward excess risk of graft-versus-host mortality was noted (HR for total lymphocyte TL, 1.26; P = .15). In conclusion, longer donor TL was associated with reduced rate of infection-related deaths after HCT for SAA.
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Induction of fetal hemoglobin synthesis by CRISPR/Cas9-mediated editing of the human β-globin locus.
Naturally occurring, large deletions in the β-globin locus result in hereditary persistence of fetal hemoglobin, a condition that mitigates the clinical severity of sickle cell disease (SCD) and β-thalassemia. We designed a clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 9 (Cas9) (CRISPR/Cas9) strategy to disrupt a 13.6-kb genomic region encompassing the δ- and β-globin genes and a putative γ-δ intergenic fetal hemoglobin (HbF) silencer. ⋯ In primary SCD patient-derived hematopoietic stem/progenitor cells, targeting the 13.6-kb region results in a high proportion of γ-globin expression in erythroblasts, increased HbF synthesis, and amelioration of the sickling cell phenotype. Overall, this study provides clues for a potential CRISPR/Cas9 genome editing approach to the therapy of β-hemoglobinopathies.
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Clinical Trial
Effect of nonpermissive HLA-DPB1 mismatches after unrelated allogeneic transplantation with in vivo T-cell depletion.
We investigated the impact of donor-recipient HLA-DPB1 matching on outcomes of allogeneic hematopoietic stem cell transplantation with in vivo T-cell depletion using antithymocyte globulin (ATG) for patients with hematological malignancies. All donor-recipient pairs had high-resolution typing for HLA-A, HLA-B, HLA-C, HLA-DRB1, HLA-DQB1, HLA-DPB1, and HLA-DRB3/4/5 and were matched at HLA-A, HLA-B, HLA-C, and HLA-DRB1. HLA-DPB1 mismatches were categorized by immunogenicity of the DPB1 matching using the DPB T-cell epitope tool. ⋯ However, the favorable prognosis of HLA-DPB1 mismatches on disease progression was observed only in peripheral blood stem cell recipients who were in the intermediate-risk group by the Disease Risk Index (HR, 0.4; P = .001) but no other risk groups. Our results suggest avoidance of nonpermissive GVH HLA-DPB1 mismatches for lowering the risk for grade II to IV and III to IV aGVHD. Permissive or nonpermissive HVG HLA-DPB1 mismatches may be preferred over HLA-DPB1 matches in the intermediate-risk patients to decrease the risk for disease progression.