2021 Update on MRD in acute myeloid leukemia: a consensus document from the European LeukemiaNet MRD Working Party.

Measurable residual disease (MRD) is an important biomarker in acute myeloid leukemia (AML) that is used for prognostic, predictive, monitoring, and efficacy-response assessments. The European LeukemiaNet (ELN) MRD Working Party evaluated standardization and harmonization of MRD in an ongoing manner and has updated the 2018 ELN MRD recommendations based on significant developments in the field. New and revised recommendations were established during in-person and online meetings, and a 2-stage Delphi poll was conducted to optimize consensus. All recommendations are graded by levels of evidence and agreement. Major changes include technical specifications for next-generation sequencing-based MRD testing and integrative assessments of MRD irrespective of technology. Other topics include use of MRD as a prognostic and surrogate end point for drug testing; selection of the technique, material, and appropriate time points for MRD assessment; and clinical implications of MRD assessment. In addition to technical recommendations for flow- and molecular-MRD analysis, we provide MRD thresholds and define MRD response, and detail how MRD results should be reported and combined if several techniques are used. MRD assessment in AML is complex and clinically relevant, and standardized approaches to application, interpretation, technical conduct, and reporting are of critical importance.

PET-guided eBEACOPP treatment of advanced-stage Hodgkin lymphoma (HD18): follow-up analysis of an international, open-label, randomised, phase 3 trial.

BACKGROUND: The German Hodgkin Study Group's HD18 trial established the safety and efficacy of PET-guided eBEACOPP (bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone in escalated doses) for the treatment of advanced-stage Hodgkin lymphoma. However, because of a protocol amendment during the enrolment period (June 1, 2011) that changed standard treatment from eight to six cycles, the results of the HD18 trial have been partially immature. We report a prespecified 5-year follow-up analysis of the completed HD18 trial. METHODS: HD18 was an international, open-label, randomised, phase 3 trial done in 301 hospitals and private practices in five European countries. Patients aged 18-60 years with newly diagnosed, advanced-stage Hodgkin lymphoma and an Eastern Cooperative Oncology Group performance status of 0-2 were recruited. After receiving an initial two cycles of eBEACOPP (1250 mg/m2 intravenous cyclophosphamide [day 1], 35 mg/m2 intravenous doxorubicin [day 1], 200 mg/m2 intravenous etoposide [day 1-3], 100 mg/m2 oral procarbazine [day 1-7], 40 mg/m2 oral prednisone [day 1-14], 1·4 mg/m2 intravenous vincristine [day 8], and 10 mg/m2 intravenous bleomycin [day 8]), patients underwent a contrast-enhanced CT and PET scan (PET-2). Patients with positive PET-2 were randomly assigned to receive standard therapy (an additional six cycles of eBEACOPP; ie, eight cycles in total) or experimental therapy (an additional six cycles of eBEACOPP plus 375 mg/m2 intravenous rituximab; ie, eight cycles in total) until June 1, 2011. After June 1, 2011, all patients with positive PET-2 were assigned to the updated standard therapy with an additional four cycles of eBEACOPP (ie, six cycles in total). Patients with negative PET-2 were randomly assigned (1:1) to receive standard therapy (an additional six cycles of eBEACOPP [ie, eight cycles in total] until June 1, 2011; an additional four cycles of eBEACOPP [ie, six cycles in total] after June 1, 2011) or experimental therapy (an additional two cycles of eBEACOPP; ie, four cycles in total). Randomisation was done centrally with the minimisation method, including a random component, stratified by centre, age, stage, international prognostic score, and sex. The primary endpoint was progression-free survival. HD18 aimed to improve 5-year progression-free survival by 15% in the PET-2-positive intention-to-treat cohort and to exclude inferiority of 6% or more in 5-year progression-free survival in the PET-2-negative per-protocol population. This study is registered with ClinicalTrials.gov, NCT00515554, and is completed. FINDINGS: Between May 14, 2008, and July 18, 2014, 2101 patients were enrolled and 1945 were assigned to a treatment group according to their PET-2 result. In the PET-2-positive cohort, with a median follow-up of 73 months (IQR 59 to 94), 5-year progression-free survival was 89·9% (95% CI 85·7 to 94·1) in 217 patients assigned to eight cycles of eBEACOPP before the protocol amendment and 87·7% (83·1 to 92·4) in 217 patients assigned to eight cycles of rituximab plus eBEACOPP (p=0·40). Among 506 patients who received six cycles of eBEACOPP after the protocol amendment, 5-year progression-free survival was 90·1% (95% CI 87·2 to 92·9), with a median follow-up of 58 months (IQR 39 to 66). In the PET-2-negative cohort, with a median follow-up of 66 months (IQR 54 to 85) in the combined pre-amendment and post-amendment groups, 5-year progression-free survival was 91·2% (95% CI 88·4 to 93·9) in 446 patients who received eight or six cycles of eBEACOPP and 93·0% (90·6 to 95·4) in 474 patients who received four cycles of eBEACOPP (difference 1·9% [95% CI -1·8 to 5·5]). In the subgroup of PET-2-negative patients randomly assigned after protocol amendment, 5-year progression-free survival was 90·9% (95% CI 86·8 to 95·1) in 202 patients assigned to receive six cycles of eBEACOPP and 91·0% (86·6 to 95·5) in 200 patients assigned to receive four cycles of eBEACOPP (difference 0·1% [-5·9 to 6·2]). INTERPRETATION: Long-term follow-up confirms the efficacy and safety of PET-2-guided eBEACOPP in patients with advanced-stage Hodgkin lymphoma. The reduction from eight to four cycles of eBEACOPP represents a benchmark in the treatment of early-responding patients, who can now be potentially cured with a short and safe treatment approach. FUNDING: Deutsche Krebshilfe, Swiss State Secretariat for Education, Research and Innovation SERI (Switzerland), and Roche Pharma. TRANSLATION: For the German translation of the abstract see Supplementary Materials section.

TET1 promotes growth of T-cell acute lymphoblastic leukemia and can be antagonized via PARP inhibition.

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological cancer characterized by skewed epigenetic patterns, raising the possibility of therapeutically targeting epigenetic factors in this disease. Here we report that among different cancer types, epigenetic factor TET1 is highly expressed in T-ALL and is crucial for human T-ALL cell growth in vivo. Knockout of TET1 in mice and knockdown in human T cell did not perturb normal T-cell proliferation, indicating that TET1 expression is dispensable for normal T-cell growth. The promotion of leukemic growth by TET1 was dependent on its catalytic property to maintain global 5-hydroxymethylcytosine (5hmC) marks, thereby regulate cell cycle, DNA repair genes, and T-ALL associated oncogenes. Furthermore, overexpression of the Tet1-catalytic domain was sufficient to augment global 5hmC levels and leukemic growth of T-ALL cells in vivo. We demonstrate that PARP enzymes, which are highly expressed in T-ALL patients, participate in establishing H3K4me3 marks at the TET1 promoter and that PARP1 interacts with the TET1 protein. Importantly, the growth related role of TET1 in T-ALL could be antagonized by the clinically approved PARP inhibitor Olaparib, which abrogated TET1 expression, induced loss of 5hmC marks, and antagonized leukemic growth of T-ALL cells, opening a therapeutic avenue for this disease.

Applicability and reproducibility of acute myeloid leukaemia stem cell assessment in a multi-centre setting.

Leukaemic stem cells (LSC) have been experimentally defined as the leukaemia-propagating population and are thought to be the cellular reservoir of relapse in acute myeloid leukaemia (AML). Therefore, LSC measurements are warranted to facilitate accurate risk stratification. Previously, we published the composition of a one-tube flow cytometric assay, characterised by the presence of 13 important membrane markers for LSC detection. Here we present the validation experiments of the assay in several large AML research centres, both in Europe and the United States. Variability within instruments and sample processing showed high correlations between different instruments (Rpearson  > 0·91, P < 0·001). Multi-centre testing introduced variation in reported LSC percentages but was found to be below the clinical relevant threshold. Clear gating protocols resulted in all laboratories being able to perform LSC assessment of the validation set. Participating centres were nearly unanimously able to distinguish LSChigh (>0·03% LSC) from LSClow (<0·03% LSC) despite inter-laboratory variation in reported LSC percentages. This study proves that the LSC assay is highly reproducible. These results together with the high prognostic impact of LSC load at diagnosis in AML patients render the one-tube LSC assessment a good marker for future risk classification.

Somatostatin receptor mediated targeting of acute myeloid leukemia by photodynamic metal complexes for light induced apoptosis.

Acute myeloid leukemia (AML) is characterized by relapse and treatment resistance in a major fraction of patients, underlining the need of innovative AML targeting therapies. Here we analysed the therapeutic potential of an innovative biohybrid consisting of the tumor-associated peptide somatostatin and the photosensitizer ruthenium in AML cell lines and primary AML patient samples. Selective toxicity was analyzed by using CD34 enriched cord blood cells as control. Treatment of OCI AML3, HL60 and THP1 resulted in a 92, and 99 and 97% decrease in clonogenic growth compared to the controls. Primary AML cells demonstrated a major response with a 74 to 99% reduction in clonogenicity in 5 of 6 patient samples. In contrast, treatment of CD34+ CB cells resulted in substantially less reduction in colony numbers. Subcellular localization assays of RU-SST in OCI-AML3 cells confirmed strong co-localization of RU-SST in the lysosomes compared to the other cellular organelles. Our data demonstrate that conjugation of a Ruthenium complex with somatostatin is efficiently eradicating LSC candidates of patients with AML. This indicates that receptor mediated lysosomal accumulation of photodynamic metal complexes is a highly attractive approach for targeting AML cells.

Differences in expression and function of LEF1 isoforms in normal versus leukemic hematopoiesis.

Acute myeloid leukemia (AML) is the most common acute leukemia in adults and is propagated by leukemic stem cells (LSCs), often characterized by deregulated Wnt signaling. We previously showed that the central transcriptional mediator of Wnt signaling LEF1 is able to cause AML in mice and acts as an independent prognostic factor in normal karyotype AML. Here, we show that treatment naïve normal karyotype AML as well as samples AML LSCs predominantly express the long ß-catenin-binding isoform of LEF1 in sharp contrast to normal human hematopoietic stem cells, which lack expression of the long isoform, but express the short N-terminally truncated isoform with loss of the ß-catenin-binding site. Gene expression and ChiP-Seq analyses in mice linked the long isoform to Wnt-ß-catenin signaling and oncogenic pathways, the N-terminally truncated isoform to stemness associated genes. Approaches impairing binding of LEF1 to ß-catenin significantly impaired AML growth, but spared normal hematopoietic stem cells. This report now demonstrates a striking difference of LEF1 isoform expression between normal and AML cells, contributing to higher vulnerability of leukemic cells to approaches targeting ß-catenin/LEF1 interaction.

The ParaHox gene Cdx4 induces acute erythroid leukemia in mice.

Acute erythroid leukemia (AEL) is a rare and aggressive form of acute leukemia, the biology of which remains poorly understood. Here we demonstrate that the ParaHox gene CDX4 is expressed in patients with acute erythroid leukemia, and that aberrant expression of Cdx4 induced homogenously a transplantable acute erythroid leukemia in mice. Gene expression analyses demonstrated upregulation of genes involved in stemness and leukemogenesis, with parallel downregulation of target genes of Gata1 and Gata2 responsible for erythroid differentiation. Cdx4 induced a proteomic profile that overlapped with a cluster of proteins previously defined to represent the most primitive human erythroid progenitors. Whole-exome sequencing of diseased mice identified recurrent mutations significantly enriched for transcription factors involved in erythroid lineage specification, as well as TP53 target genes partly identical to the ones reported in patients with AEL. In summary, our data indicate that Cdx4 is able to induce stemness and inhibit terminal erythroid differentiation, leading to the development of AEL in association with co-occurring mutations.

Doxorubicin, vinblastine, dacarbazine and lenalidomide for older Hodgkin lymphoma patients: final results of a German Hodgkin Study Group (GHSG) phase-I trial.

About 30% of all Hodgkin lymphoma (HL) patients are ≥60 years old. As lenalidomide has promising single agent activity in multiple relapsed HL, we replaced bleomycin in ABVD with lenalidomide in this phase-I trial. Patients aged ≥60 years with early-unfavourable- or advanced-stage HL (Eastern Cooperative Oncology Group performance status ≤2, Cumulative Illness Rating Scale for Geriatrics score 0-7) received 4-8 cycles of AVD (doxorubicin, vinblastine, dacarbazine) and lenalidomide in escalation with overdose control. Dose-limiting toxicities (DLTs) included thromboembolism ≥grade 2, severe haematological toxicity, neutropenic fever and prolonged therapy delay. Twenty-five patients with a median age of 68 years were included, 68% had advanced-stage HL. A pre-defined stopping criterion for dose escalation after DLT evaluation of 20/24 patients suggested a recommended phase II dose (RPTD) of 20 mg. DLTs occurred in 10/24 evaluable patients, all treated with ≥20 mg, however, median relative dose intensity was 97% (interquartile range 49-104%). Grade 3 or higher toxicities occurred in all 22 patients at ≥20 mg lenalidomide but no treatment-related deaths occurred. Overall response rate was 80% for all patients (20/25) and 86% (19/22) at ≥20 mg lenalidomide. Three-year estimates for progression-free survival and OS were 69·7% (95% CI: 50·3-89·1%) and 83·8% (95%-CI: 69·3-98·4%), respectively. In conclusion, AVD with lenalidomide 20 mg is feasible and highly effective in older HL patients.

PET-guided treatment in patients with advanced-stage Hodgkin's lymphoma (HD18): final results of an open-label, international, randomised phase 3 trial by the German Hodgkin Study Group.

BACKGROUND: The intensive polychemotherapy regimen eBEACOPP (bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone in escalated doses) is very active in patients with advanced-stage Hodgkin's lymphoma, albeit at the expense of severe toxicities. Individual patients might be cured with less burdensome therapy. We investigated whether metabolic response determined by PET after two cycles of standard regimen eBEACOPP (PET-2) would allow adaption of treatment intensity, increasing it for PET-2-positive patients and reducing it for PET-2-negative patients. METHODS: In this open-label, randomised, parallel-group phase 3 trial, we recruited patients aged 18-60 years with newly diagnosed, advanced-stage Hodgkin's lymphoma in 301 hospitals and private practices in Germany, Switzerland, Austria, the Netherlands, and the Czech Republic. After central review of PET-2, patients were assigned (1:1) to one of two parallel treatment groups on the basis of their PET-2 result. Patients with positive PET-2 were randomised to receive six additional cycles of either standard eBEACOPP (8 × eBEACOPP in total) or eBEACOPP with rituximab (8 × R-eBEACOPP). Those with negative PET-2 were randomised between standard treatment with six additional cycles of eBEACOPP (8 × eBEACOPP) or experimental treatment with two additional cycles (4 × eBEACOPP). A protocol amendment in June, 2011, introduced a reduction of standard therapy to 6 × eBEACOPP; after this point, patients with positive PET-2 were no longer randomised and were all assigned to receive 6 × eBEACOPP and patients with negative PET-2 were randomly assigned to 6 × eBEACOPP (standard) or 4 × eBEACOPP (experimental). Randomisation was done centrally using the minimisation method including a random component, stratified according to centre, age (<45 vs ≥45 years), stage (IIB, IIIA vs IIIB, IV), international prognostic score (0-2 vs 3-7), and sex. eBEACOPP was given as previously described; rituximab was given intravenously at a dose of 375 mg/m2 (maximum total dose 700 mg). The primary objectives were to show superiority of the experimental treatment in the PET-2-positive cohort, and to show non-inferiority of the experimental treatment in the PET-2-negative cohort in terms of the primary endpoint, progression-free survival. We defined non-inferiority as an absolute difference of 6% in the 5-year progression-free survival estimates. Primary analyses in the PET-2-negative cohort were per protocol; all other analyses were by intention to treat. This trial was registered with ClinicalTrials.gov, number NCT00515554. FINDINGS: Between May 14, 2008, and July 18, 2014, we recruited 2101 patients, of whom 137 were found ineligible before randomisation and a further 19 were found ineligible after randomisation. Among 434 randomised patients (217 per arm) with positive PET-2, 5-year progression-free survival was 89·7% (95% CI 85·4-94·0) with eBEACOPP and 88·1% (83·5-92·7) with R-eBEACOPP (log-rank p=0·46). Patients with negative PET-2 randomly assigned to either 8 × eBEACOPP or 6 × eBEACOPP (n=504) or 4 × eBEACOPP (n=501) had 5-year progression-free survival of 90·8% (95% CI 87·9-93·7) and 92·2% (89·4-95·0), respectively (difference 1·4%, 95% CI -2·7 to 5·4). 4 × eBEACOPP was associated with fewer severe infections (40 [8%] of 498 vs 75 [15%] of 502) and organ toxicities (38 [8%] of 498 vs 91 [18%] of 502) than were 8 × eBEACOPP or 6 × eBEACOPP in PET-2-negative patients. Ten treatment-related deaths occurred: four in the PET-2-positive cohort (one [<1%] in the 8 × eBEACOPP group, three [1%] in the 8 × R-eBEACOPP group) and six in the PET-2-negative group (six [1%] in the 8 × eBEACOPP or 6 × eBEACOPP group). INTERPRETATION: The favourable outcome of patients treated with eBEACOPP could not be improved by adding rituximab after positive PET-2. PET-2 negativity allows reduction to only four cycles of eBEACOPP without loss of tumour control. PET-2-guided eBEACOPP provides outstanding efficacy for all patients and increases overall survival by reducing treatment-related risks for patients with negative PET-2. We recommend this PET-2-guided treatment strategy for patients with advanced-stage Hodgkin's lymphoma. FUNDING: Deutsche Krebshilfe, Swiss State Secretariat for Education and Research, and Roche Pharma AG.

Progression-free survival of early interim PET-positive patients with advanced stage Hodgkin's lymphoma treated with BEACOPPescalated alone or in combination with rituximab (HD18): an open-label, international, randomised phase 3 study by the German Hodgkin Study Group.

BACKGROUND: Advanced stage Hodgkin's lymphoma represents a heterogeneous group of patients with different risk profiles. Data suggests that interim PET assessment during chemotherapy is superior to baseline international prognostic scoring in terms of predicting long-term treatment outcome in patients with Hodgkin's lymphoma. We therefore hypothesised that early interim PET-imaging after two courses of bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone (BEACOPP) might be suitable for guiding treatment in patients with advanced stage Hodgkin's lymphoma. We aimed to assess whether intensifying standard chemotherapy (BEACOPPescalated) by adding rituximab would improve progression-free survival in patients with positive PET after two courses of chemotherapy. METHODS: In this open-label, international, randomised, phase 3 study, we recruited patients aged 18-60 years with newly diagnosed, advanced stage Hodgkin's lymphoma from 160 hospitals and 77 private practices in Germany, Switzerland, Austria, the Netherlands, and the Czech Republic. Interim PET-imaging was done after two cycles of BEACOPPescalated and centrally assessed by an expert panel. Patients with a positive PET after 2 cycles of BEACOPPescalated chemotherapy (PET-2) were randomly assigned (1:1) to receive six additional courses of either BEACOPPescalated (BEACOPPescalated group) or BEACOPPescalated plus rituximab (R-BEACOPPescalated group). PET-2 was assessed using a 5-point scale with 18FDG uptake higher than the mediastinal blood pool (corresponding to Deauville scale 3) defined as positive. BEACOPPescalated was given as previously described; rituximab was given intravenously at a dose of 375 mg/m2 (maximum total dose 700 mg), the first administration starting 24 h before starting the fourth cycle of BEACOPPescalated (day 0 and day 3 in cycle 4, day 1 in cycles 5-8). Randomisation was done centrally and used the minimisation method including a random component, stratified according to centre, age, stage, international prognostic score, and sex. The primary efficacy endpoint was 5 year progression-free survival, analysed in the intention-to-treat population. We are reporting this second planned interim analysis as the final report of the trial. The trial is registered with ClinicalTrials.gov, number NCT00515554. FINDINGS: Between May 14, 2008, and May 31, 2011, we enrolled 1100 patients. 440 patients had a positive PET-2 and were randomly assigned to either the BEACOPPescalated group (n=220) or the R-BEACOPPescalated group (n=220). With a median follow-up of 33 months (IQR 25-42) for progression-free survival, estimated 3 year progression-free survival was 91·4% (95% CI 87·0-95·7) for patients in the BEACOPPescalated group and 93·0% (89·4-96·6) for those in the R-BEACOPPescalated group (difference 1·6%, 95% CI -4·0 to 7·3; log rank p=0·99). Common grade 3-4 adverse events were leucopenia (207 [95%] of 218 patients in the BEACOPPescalated group vs 211 [96%] of 220 patients in the R-BEACOPPescalated group), and severe infections (51 [23%] vs 43 [20%] patients). Based on a futility analysis, the independent data monitoring committee recommended publication of this second planned interim analysis as the final result. Six (3%) of 219 patients in the BEACOPPescalated group and ten (5%) of 220 in the R-BEACOPPescalated group died; fatal treatment-related toxic effects occurred in one (<1%) patient in the BEACOPPescalated group and three (1%) in the R-BEACOPPescalated group, all of them due to infection. INTERPRETATION: The addition of rituximab to BEACOPPescalated did not improve the progression-free survival of PET-2 positive patients with advanced stage Hodgkin's lymphoma. However, progression-free survival for PET-2 positive patients was much better than expected, exceeding even the outcome of PET-2-unselected patients in the previous HD15 trial. Thus, PET-2 cannot identify patients at high-risk for treatment failure in the context of the very effective German Hodgkin Study Group standard treatment for advanced stage Hodgkin's lymphoma. FUNDING: Deutsche Krebshilfe; Swiss State Secretariat for Education, Research and Innovation (SERI); and Roche Pharma.

Mitochondria Targeted Protein-Ruthenium Photosensitizer for Efficient Photodynamic Applications.

Organelle-targeted photosensitization represents a promising approach in photodynamic therapy where the design of the active photosensitizer (PS) is very crucial. In this work, we developed a macromolecular PS with multiple copies of mitochondria-targeting groups and ruthenium complexes that displays highest phototoxicity toward several cancerous cell lines. In particular, enhanced anticancer activity was demonstrated in acute myeloid leukemia cell lines, where significant impairment of proliferation and clonogenicity occurs. Finally, attractive two-photon absorbing properties further underlined the great significance of this PS for mitochondria targeted PDT applications in deep tissue cancer therapy.

Controlled stem cell amplification by HOXB4 depends on its unique proline-rich region near the N terminus.

There is high interest in understanding the mechanisms that drive self-renewal of stem cells. HOXB4 is one of the few transcription factors that can amplify long-term repopulating hematopoietic stem cells in a controlled way. Here we show in mice that this characteristic of HOXB4 depends on a proline-rich sequence near the N terminus, which is unique among HOX genes and highly conserved in higher mammals. Deletion of this domain substantially enhanced the oncogenicity of HOXB4, inducing acute leukemia in mice. Conversely, insertion of the domain into Hoxa9 impaired leukemogenicity of this homeobox gene. These results indicate that proline-rich stretches attenuate the potential of stem cell active homeobox genes to acquire oncogenic properties.

VENTX induces expansion of primitive erythroid cells and contributes to the development of acute myeloid leukemia in mice.

Homeobox genes are key regulators in normal and malignant hematopoiesis. The human Vent-like homeobox gene VENTX, a putative homolog of the Xenopus laevis Xvent-2 gene, was shown to be highly expressed in normal myeloid cells and in patients with acute myeloid leukemia. We now demonstrate that constitutive expression of VENTX suppresses expression of genes responsible for terminal erythroid differentiation in normal CD34+ stem and progenitor cells. Transplantation of bone marrow progenitor cells retrovirally engineered to express VENTX caused massive expansion of primitive erythroid cells and partly acute erythroleukemia in transplanted mice. The leukemogenic potential of VENTX was confirmed in the AML1-ETO transplantation model, as in contrast to AML1-ETO alone co-expression of AML1-ETO and VENTX induced acute myeloid leukemia, partly expressing erythroid markers, in all transplanted mice. VENTX was highly expressed in patients with primary human erythroleukemias and knockdown of VENTX in the erythroleukemic HEL cell line significantly blocked cell growth. In summary, these data indicate that VENTX is able to perturb erythroid differentiation and to contribute to myeloid leukemogenesis when co-expressed with appropriate AML oncogenes and point to its potential significance as a novel therapeutic target in AML.

DNA Damage-Induced HSPC Malfunction Depends on ROS Accumulation Downstream of IFN-1 Signaling and Bid Mobilization.

Mouse mutants with an impaired DNA damage response frequently exhibit a set of remarkably similar defects in the HSPC compartment that are of largely unknown molecular basis. Using Mixed-Lineage-Leukemia-5 (Mll5)-deficient mice as prototypical examples, we have identified a mechanistic pathway linking DNA damage and HSPC malfunction. We show that Mll5 deficiency results in accumulation of DNA damage and reactive oxygen species (ROS) in HSPCs. Reduction of ROS efficiently reverses hematopoietic defects, establishing ROS as a major cause of impaired HSPC function. The Ink4a/Arf locus also contributes to HSPC phenotypes, at least in part via promotion of ROS. Strikingly, toxic ROS levels in Mll5-/- mice are critically dependent on type 1 interferon (IFN-1) signaling, which triggers mitochondrial accumulation of full-length Bid. Genetic inactivation of Bid diminishes ROS levels and reverses HSPC defects in Mll5-/- mice. Overall, therefore, our findings highlight an unexpected IFN-1 > Bid > ROS pathway underlying DNA damage-associated HSPC malfunction.

MEIS2 Is an Oncogenic Partner in AML1-ETO-Positive AML.

Homeobox genes are known to be key factors in leukemogenesis. Although the TALE family homeodomain factor Meis1 has been linked to malignancy, a role for MEIS2 is less clear. Here, we demonstrate that MEIS2 is expressed at high levels in patients with AML1-ETO-positive acute myeloid leukemia and that growth of AML1-ETO-positive leukemia depends on MEIS2 expression. In mice, MEIS2 collaborates with AML1-ETO to induce acute myeloid leukemia. MEIS2 binds strongly to the Runt domain of AML1-ETO, indicating a direct interaction between these transcription factors. High expression of MEIS2 impairs repressive DNA binding of AML1-ETO, inducing increased expression of genes such as the druggable proto-oncogene YES1. Collectively, these data describe a pivotal role for MEIS2 in AML1-ETO-induced leukemia.

Leukemic progenitor cells are susceptible to targeting by stimulated cytotoxic T cells against immunogenic leukemia-associated antigens.

Leukemic stem cells (LSC) might be the source for leukemic disease self-renewal and account for disease relapse after treatment, which makes them a critical target for further therapeutic options. We investigated the role of cytotoxic T-lymphocytes (CTL) counteracting and recognizing LSC. Leukemia-associated antigens (LAA) represent immunogenic structures to target LSC. We enriched the LSC-containing fraction of 20 AML patients and hematopoietic stem cells (HSC) of healthy volunteers. Using microarray analysis and qRT-PCR we detected high expression of several LAA in AML cells but also in LSC. PRAME (p = 0.0085), RHAMM (p = 0.03), WT1 (p = 0.04) and Proteinase 3 (p = 0.04) showed significant differential expression in LSC compared with HSC. PRAME, RHAMM and WT1 are furthermore also lower expressed on leukemic bulk. In contrast, Proteinase 3 indicates a higher expression on leukemic bulk than on LSC. In colony forming unit (CFU) immunoassays, T cells stimulated against various LAA indicated a significant inhibition of CFUs in AML patient samples. The LAA PRAME, RHAMM and WT1 showed highest immunogenic responses with a range up to 58-83%. In a proof of principle xenotransplant mouse model, PRAME-stimulated CTL targeted AML stem cells, reflected by a delayed engraftment of leukemia (p = 0.0159). Taken together, we demonstrated the expression of several LAA in LSC. LAA-specific T cells are able to hamper LSC in immunoassays and in a mouse model, which suggests that immunotherapeutic approaches have the potential to target malignant stem cells.

Combined molecular and clinical prognostic index for relapse and survival in cytogenetically normal acute myeloid leukemia.

PURPOSE: Cytogenetically normal (CN) acute myeloid leukemia (AML) is the largest and most heterogeneous cytogenetic AML subgroup. For the practicing clinician, it is difficult to summarize the prognostic information of the growing number of clinical and molecular markers. Our purpose was to develop a widely applicable prognostic model by combining well-established pretreatment patient and disease characteristics. PATIENTS AND METHODS: Two prognostic indices for CN-AML (PINA), one regarding overall survival (OS; PINAOS) and the other regarding relapse-free survival (RFS; PINARFS), were derived from data of 572 patients with CN-AML treated within the AML Cooperative Group 99 study (www.aml-score.org). RESULTS: On the basis of age (median, 60 years; range, 17 to 85 years), performance status, WBC count, and mutation status of NPM1, CEBPA, and FLT3-internal tandem duplication, patients were classified into the following three risk groups according to PINAOS and PINARFS: 29% of all patients and 32% of 381 responding patients had low-risk disease (5-year OS, 74%; 5-year RFS, 55%); 56% of all patients and 39% of responding patients had intermediate-risk disease (5-year OS, 28%; 5-year RFS, 27%), and 15% of all patients and 29% of responding patients had high-risk disease (5-year OS, 3%; 5-year RFS, 5%), respectively. PINAOS and PINARFS stratified outcome within European LeukemiaNet genetic groups. Both indices were confirmed on independent data from Cancer and Leukemia Group B/Alliance trials. CONCLUSION: We have developed and validated, to our knowledge, the first prognostic indices specifically designed for adult patients of all ages with CN-AML that combine well-established molecular and clinical variables and that are easily applicable in routine clinical care. The integration of both clinical and molecular markers could provide a basis for individualized patient care through risk-adapted therapy of CN-AML.

A core-shell albumin copolymer nanotransporter for high capacity loading and two-step release of doxorubicin with enhanced anti-leukemia activity.

The native transportation protein serum albumin represents an attractive nano-sized transporter for drug delivery applications due to its beneficial safety profile. Existing albumin-based drug delivery systems are often limited by their low drug loading capacity as well as noticeable drug leakage into the blood circulation. Therefore, a unique albumin-derived core-shell doxorubicin (DOX) delivery system based on the protein denaturing-backfolding strategy was developed. 28 DOX molecules were covalently conjugated to the albumin polypeptide backbone via an acid sensitive hydrazone linker. Polycationic and pegylated human serum albumin formed two non-toxic and enzymatically degradable protection shells around the encapsulated DOX molecules. This core-shell delivery system possesses notable advantages, including a high drug loading capacity critical for low administration doses, a two-step drug release mechanism based on pH and the presence of proteases, an attractive biocompatibility and narrow size distribution inherited from the albumin backbone, as well as fast cellular uptake and masking of epitopes due to a high degree of pegylation. The IC50 of these nanoscopic onion-type micelles was found in the low nanomolar range for Hela cells as well as leukemia cell lines. In vivo data indicate its attractive potential as anti-leukemia treatment suggesting its promising profile as nanomedicine drug delivery system.