Gerhard Behre

Dominant-negative mutations of CEBPA , encoding CCAAT/enhancer binding protein-α (C/EBPα), in acute myeloid leukemia

The transcription factor C/EBPα (for CCAAT/enhancer binding protein-α; encoded by the gene CEBPA) is crucial for the differentiation of granulocytes. Conditional expression of C/EBPα triggers neutrophilic differentiation, and no mature granulocytes are observed in Cebpa-mutant mice. Here we identify heterozygous mutations in CEBPA in ten patients with acute myeloid leukemia (AML). We found that five mutations in the amino terminus truncate the full-length protein, but did not affect a 30-kD protein initiated further downstream. The mutant proteins block wild-type C/EBPα DNA binding and transactivation of granulocyte target genes in a dominant-negative manner, and fails to induce granulocytic differentiation. Ours is the first report of CEBPA mutations in human neoplasia, and such mutations are likely to induce the differentiation block found in AML.

AML1-ETO downregulates the granulocytic differentiation factor C/EBPalpha in t (8;21) myeloid leukemia

The transcription factor CCAAT/enhancer binding protein α, or C/EBPα, encoded by the CEBPA gene, is crucial for the differentiation of granulocytes. Conditional expression of C/EBPα triggers neutrophilic differentiation, and Cebpa knockout mice exhibit an early block in maturation. Dominant-negative mutations of CEBPA have been found in some patients with acute myeloid leukemia (AML), but not in AML with the t(8;21) translocation which gives rise to the fusion gene RUNX1–CBF2T1 (also known as AML1–ETO) encoding the AML1–ETO fusion protein. RUNX1–CBF2T1 positive-AML blasts had eight-fold lower CEBPA RNA levels and undetectable C/EBPα protein levels compared with other subgroups of AML patients. Conditional expression of RUNX1–CBF2T1 in U937 cells downregulated CEBPA mRNA, protein and DNA binding activity. AML1–ETO appears to suppress C/EBPα expression indirectly by inhibiting positive autoregulation of the CEBPA promoter. Conditional expression of C/EBPα in AML1–ETO-positive Kasumi-1 cells results in neutrophilic differentiation. We suggest that restoring C/EBPα expression will have therapeutic implications in RUNX1–CBF2T1-positive leukemias.

Cell-cycle regulator E2F1 and microRNA-223 comprise an autoregulatory negative feedback loop in acute myeloid leukemia

Transcription factor CCAAT enhancer binding protein alpha (C/EBPalpha) is essential for granulopoiesis and its function is deregulated in leukemia. Inhibition of E2F1, the master regulator of cell-cycle progression, by C/EBPalpha is pivotal for granulopoiesis. Recent studies show microRNA-223 (miR-223), a transcriptional target of C/EBPalpha, as a critical player during granulopoiesis. In this report, we demonstrate that during granulopoiesis microRNA-223 targets E2F1. E2F1 protein was up-regulated in miR-223 null mice. We show that miR-223 blocks cell-cycle progression in myeloid cells. miR-223 is down-regulated in different subtypes of acute myeloid leukemia (AML). We further show that E2F1 binds to the miR-223 promoter in AML blast cells and inhibits miR-223 transcription, suggesting that E2F1 is a transcriptional repressor of the miR-223 gene in AML. Our study supports a molecular network involving miR-223, C/EBPalpha, and E2F1 as major components of the granulocyte differentiation program, which is deregulated in AML.

c-Jun Is a JNK-independent Coactivator of the PU.1 Transcription Factor

The ETS domain transcription factor PU.1 is necessary for the development of monocytes and regulates, in particular, the expression of the monocyte-specific macrophage colony-stimulating factor (M-CSF) receptor, which is critical for monocytic cell survival, proliferation, and differentiation. The bZIP transcription factor c-Jun, which is part of the AP-1 transcription factor complex, is also important for monocytic differentiation, but the monocyte-specific M-CSF receptor promoter has no AP-1 consensus binding sites. We asked the question of whether c-Jun could promote the induction of the M-CSF receptor by collaborating with PU.1. We demonstrate that c-Jun enhances the ability of PU.1 to transactivate the M-CSF receptor promoter as well as a minimal thymidine kinase promoter containing only PU.1 DNA binding sites. c-Jun does not directly bind to the M-CSF receptor promoter but associates via its basic domain with the ETS domain of PU.1. Consistent with our observation that AP-1 binding does not contribute to c-Jun coactivation is the observation that the activation of PU.1 by c-Jun is blocked by overexpression of c-Fos. Phosphorylation of c-Jun by c-Jun NH2-terminal kinase on Ser-63 and -73 does not alter the ability of c-Jun to enhance PU.1 transactivation. Activated Ras enhances the transcriptional activity of PU.1 by up-regulating c-Jun expression without changing the phosphorylation pattern of PU.1. The activation of PU.1 by Ras is blocked by a mutant c-Jun protein lacking the basic domain. The expression of this mutant form of c-Jun also completely blocks 12-O-tetradecanoylphorbol-13-acetate-induced M-CSF receptor promoter activity during monocytic differentiation. We propose therefore that c-Jun acts as a c-Jun NH2-terminal kinase-independent coactivator of PU.1, resulting in M-CSF receptor expression and development of the monocytic lineage.

Marked improvement of severe progressive systemic sclerosis after transplantation of mesenchymal stem cells from an allogeneic haploidentical-related donor mediated by ligation of CD137L

Marked improvement of severe progressive systemic sclerosis after transplantation of mesenchymal stem cells from an allogeneic haploidentical-related donor mediated by ligation of CD137L

C/EBPα regulated microRNA-34a targets E2F3 during granulopoiesis and is down-regulated in AML with CEBPA mutations

The transcription factor, CCAAT enhancer binding protein alpha (C/EBPα), is crucial for granulopoiesis and is deregulated by various mechanisms in acute myeloid leukemia (AML). Mutations in the CEBPA gene are reported in 10% of human patients with AML. Even though the C/EBPα mutants are known to display distinct biologic function during leukemogenesis, the molecular basis for this subtype of AML remains elusive. We have recently showed the significance of deregulation of C/EBPα-regulated microRNA (miR) in AML. In this study, we report that miR-34a is a novel target of C/EBPα in granulopoiesis. During granulopoiesis, miR-34a targets E2F3 and blocks myeloid cell proliferation. Analysis of AML samples with CEBPA mutations revealed a lower expression of miR-34a and elevated levels of E2F3 as well as E2F1, a transcriptional target of E2F3. Manipulation of miR-34a reprograms granulocytic differentiation of AML blast cells with CEBPA mutations. These results define miR-34a as a novel therapeutic target in AML with CEBPA mutations.

Allogeneic hematopoietic cell transplantation for myelofibrosis in patients pretreated with the JAK1 and JAK2 inhibitor ruxolitinib

The Janus-activated kinase 1 (JAK1) and JAK2 inhibitor ruxolitinib is effective in decreasing symptomatic splenomegaly and myelofibrosis (MF)-related symptoms. However, allogeneic hematopoietic cell transplantation (HCT) remains the only curative option. We evaluated the impact of ruxolitinib on the outcome after HCT. A cohort of 14 patients (median age 58 years) received a subsequent graft from related (n=3) and unrelated (n=11) donors after a median exposure of 6.5 months to ruxolitinib. At HCT, MF risk for survival according to the International Prognostic Scoring System was intermediate-2 or high risk in 86% of patients. Under ruxolitinib, MF-related symptoms were ameliorated in 10 (71.4%) patients and the palpable spleen reduced by a median of 41% in 7 (64%) of 11 patients with splenomegaly. Engraftment occurred in 13 (93%) patients. Acute GvHD grade-III occurred in 2 (14%) patients. Median follow-up was 9 months. Survival, EFS and treatment-related mortality were 78.6, 64 and 7%, respectively. Through the anti-JAK-mediated reduction in both cytokines and splenomegaly as well as improvement in performance status, ruxolitinib might improve outcome after allogeneic HCT in patients with MF. The downregulation of inflammatory cytokines might have a beneficial impact on graft failure and acute GvHD.

Haploidentical allogeneic hematopoietic cell transplantation in adults using CD3/CD19 depletion and reduced intensity conditioning: a phase II study

Background We report a prospective multicenter phase II study of haploidentical hematopoietic stem cell transplantation using CD3/CD19-depleted grafts after reduced intensity conditioning with fludarabine, thiotepa, melphalan and OKT-3. Design and Methods Sixty-one adults with a median age of 46 years (range 19-65 years) have been enrolled. Diagnoses were acute myeloid leukemia (n=38), acute lymphoblastic leukemia (n=8), non-Hodgkins lymphoma (n=6), myeloma (n=4), chronic myeloid leukemia (n=3), chronic lymphatic leukemia (n=1) and myelodysplastic syndrome (n=1). Patients were considered high risk because of refractory disease (n=18), cytogenetics (n=6), complete remission (≥2) (n=9), chemosensitive relapse in partial remission (n=4) or relapse after prior hematopoietic stem cell transplantation (n=15 allogeneic, n=8 autologous, n=1 both). At haploidentical hematopoietic stem cell transplantation, 30 patients were in complete remission and 31 in partial remission. Grafts contained a median of 7.0×106 (range 3.2-22) CD34+ cells/kg, 4.2×104 (range 0.6-44) CD3+ T cells/kg and 2.7×107 (range 0.00-37.3) CD56+ cells/kg. Results Engraftment was rapid with a median of 12 days to granulocytes more than 0.5×109/L (range 9-50 days) and 11 days to platelets more than 20×109 (range 7-38 days). Incidence of grade IIIV acute graft-versus-host-disease and chronic graft-versus-host-disease was 46% and 18%, respectively. Non-relapse mortality on Day 100 was 23% and 42% at two years. Cumulative incidence of relapse/progression at two years was 31%. Kaplan-Meier estimated 1-year and 2-year overall survival with median follow up of 869 days (range 181-1932) is 41% and 28%, respectively. Conclusions This regimen allows successful haploidentical hematopoietic stem cell transplantation with reduced intensity conditioning in high-risk patients lacking a suitable donor. (clinicaltrials.gov identifier:NCT00202917).

Downregulation of c-Jun Expression by Transcription Factor C/EBPα Is Critical for Granulocytic Lineage Commitment

ABSTRACT The transcription factor C/EBPα is crucial for the differentiation of granulocytes. Conditional expression of C/EBPα triggers neutrophilic differentiation, and C/EBPα can block 12-O-tetradecanoylphorbol-13-acetate-induced monocytic differentiation of bipotential myeloid cells. In C/EBPα knockout mice, no mature granulocytes are present. A dramatic increase of c-Jun mRNA in C/EBPα knockout mouse fetal liver was observed. c-Jun, a component of the AP-1 transcription factor complex and a coactivator of the transcription factor PU.1, is important for monocytic differentiation. Here we report that C/EBPα downregulates c-Jun expression to drive granulocytic differentiation. An ectopic increase of C/EBPα expression decreases the c-Jun mRNA level, and the human c-Jun promoter activity is downregulated eightfold in the presence of C/EBPα. C/EBPα and c-Jun interact through their leucine zipper domains, and this interaction prevents c-Jun from binding to DNA. This results in downregulation of c-Juns capacity to autoregulate its own promoter through the proximal AP-1 site. Overexpression of c-Jun prevents C/EBPα-induced granulocytic differentiation. Thus, we propose a model in which C/EBPα needs to downregulate c-Jun expression and transactivation capacity for promoting granulocytic differentiation.

IgMA-enriched immunoglobulin in neutropenic patients with sepsis syndrome and septic shock: a randomized, controlled, multiple-center trial.

Objective:To evaluate the effect of intravenous IgMA-enriched immunoglobulin (ivIGMA) therapy on mortality in neutropenic patients with hematologic malignancies and sepsis syndrome or septic shock. Design:Multiple-center, prospective randomized, controlled study. Setting:Six university hospitals in Germany. Patients:Patients were 211 neutropenic patients with sepsis syndrome or septic shock after chemotherapy for severe hematologic disorders between 1992 and 1999. Interventions:Patients received 1300 mL of ivIGMA (7.8 g IgM, 7.8 g IgA, and 49.4 g IgG) infused intravenously within a period of 72 hrs or human albumin according to the same schedule as ivIGMA. Measurements and Main Results:All-cause mortality at 28 days, sepsis-related mortality at 28 days, all-cause mortality at 60 days, mortality from septic shock, and mortality from microbiologically proven Gram-negative sepsis and septic shock were recorded. Immunoglobulin had no benefit over human albumin. The 28-day mortality rate was 26.2% and 28.2% in the ivIGMA and control patients, respectively (difference, 2.0% [95% confidence interval, −10.2 to 14.2 percentage points]). Likewise, the 60-day mortality rate did not differ between both arms (29.6% vs. 34.7% in the ivIGMA and control patients, respectively). Mortality rates in patients with sepsis syndrome (17.1% vs. 16.7%) and septic shock (51.9% vs. 54.8%) were also found to be similar between both groups. Conclusions:Intravenous ivIGMA had no beneficial effects in neutropenic patients with hematologic malignancies and sepsis syndrome and septic shock.