Chemogenomic Landscape of RUNX1-mutated AML Reveals Importance of RUNX1 Allele Dosage in Genetics and Glucocorticoid Sensitivity

Immunotherapeutic targeting of surfaceome heterogeneity in AML

Immunotherapy remains underexploited in acute myeloid leukemia (AML) compared to other hematological malignancies. Currently, gemtuzumab ozogamicin is the only therapeutic antibody approved for this disease. Here, to identify potential targets for immunotherapeutic intervention, we analyze the surface proteome of 100 genetically diverse primary human AML specimens for the identification of cell surface proteins and conduct single-cell transcriptome analyses on a subset of these specimens to assess antigen expression at the sub-population level. Through this comprehensive effort, we successfully identify numerous antigens and markers preferentially expressed by primitive AML cells. Many identified antigens are targeted by therapeutic antibodies currently under clinical evaluation for various cancer types, highlighting the potential therapeutic value of the approach. Importantly, this initiative uncovers AML heterogeneity at the surfaceome level, identifies several antigens and potential primitive cell markers characterizing AML subgroups, and positions immunotherapy as a promising approach to target AML subgroup specificities.

Mathematical modelling of clonal reduction therapeutic strategies in acute myeloid leukemia

Over the years, the overall survival of older patients diagnosed with acute myeloid leukemia (AML) has not significantly increased. Although standard cytotoxic therapies that rapidly eliminate dividing myeloblasts are used to induce remission, relapse can occur due to surviving therapy-resistant leukemic stem cells (LSCs). Hence, anti-LSC strategies have become a key target to cure AML. We have recently shown that previously approved cardiac glycosides and glucocorticoids target LSC-enriched CD34+ cells in the primary human AML 8227 model with more efficacy than normal hematopoietic stem cells (HSCs). To translate these in vitro findings into humans, we developed a mathematical model of stem cell dynamics that describes the stochastic evolution of LSCs in AML post-standard-of-care. To this, we integrated population pharmacokinetic-pharmacodynamic (PKPD) models to investigate the clonal reduction potential of several promising candidate drugs in comparison to cytarabine, which is commonly used in high doses for consolidation therapy in AML patients. Our results suggest that cardiac glycosides (proscillaridin A, digoxin and ouabain) and glucocorticoids (budesonide and mometasone) reduce the expansion of LSCs through a decrease in their viability. While our model predicts that effective doses of cardiac glycosides are potentially too toxic to use in patients, simulations show the possibility of mometasone to prevent relapse through the glucocorticoid's ability to drastically reduce LSC population size. This work therefore highlights the prospect of these treatments for anti-LSC strategies and underlines the use of quantitative approaches to preclinical drug translation in AML.

SIOP PODC adapted risk stratification and treatment guidelines: Recommendations for acute myeloid leukemia in resource-limited settings

In low- and middle-income countries (LMICs), limited resources, suboptimal risk stratification, and disproportionate patient-to-infrastructure ratio result in low survival of patients with acute myeloid leukemia (AML). A high incidence of relapse, inherent to the biology, renders management arduous. The challenge of treating AML in LMICs is of balancing the intensity of myelosuppressive chemotherapy, which appears necessary for cure, with available supportive care, which influences treatment-related mortality. The recommendations outlined in this paper are based on published evidence and expert opinion. The principle of this adapted protocol is to tailor treatment to available resources, reduce preventable toxic death, and direct limited resources toward those children who are most likely to be cured.

Dexamethasone enhances venetoclax-induced apoptosis in acute myeloid leukemia cells

Acute myeloid leukemia (AML) therapies have been significantly improved by the development of medicines that can target BCL-2. On the other hand, non-recurrent alterations in oncogenic pathways and gene expression patterns have already been linked to therapeutic resistance to venetoclax therapy. Bone marrow mesenchymal stromal cells (BM-MSCs) support leukemic cells in preventing chemotherapy-induced apoptosis by mitochondrial transfer in leukemic microenvironment. In this study, we investigated the enhancement of the antitumor effect of BCL-2 inhibitor venetoclax by dexamethasone. In particular, dexamethasone had no significant effect on the viability of AML cells, but dexamethasone combined with venetoclax could significantly increase the apoptosis of AML cells induced by venetoclax. When AML cells were co-cultured with BM-MSCs, dexamethasone combined with venetoclax showed additional anti-tumor effect compared to venetoclax alone. Venetoclax increased reactive oxygen species level in co-cultured AML cells, contributed to transfer more mitochondria from BM-MSCs to AML cells and protect AML cells from apoptosis. Dexamethasone combined with venetoclax induced more apoptosis, but dexamethasone reduced the venetoclax-induced reactive oxygen species level in AML cells and reduced the transfer of mitochondria from BM-MSCs to AML cells. This may lead to a diminished protective effect of BM-MSCs on AML cells. Together, our findings indicated that venetoclax in combination with dexamethasone could be a promising therapy in AML.

Role of Gene Mutations in Acute Myeloid Leukemia: A Review Article

Acute myeloid leukemia (AML) is an immensely heterogeneous disease characterized by the clonal growth of promyelocytes or myeloblasts in bone marrow as well as in peripheral blood or tissue. Enhancement in the knowledge of the molecular biology of cancer and recognition of intermittent mutations in AML contribute to favorable circumstances to establish targeted therapies and enhance the clinical outcome. There is high interest in the development of therapies that target definitive abnormalities in AML while eradicating leukemia-initiating cells. In recent years, there has been a better knowledge of the molecular abnormalities that lead to the progression of AML, and the application of new methods in molecular biology techniques has increased that facilitating the advancement of investigational drugs. In this review, literature or information on various gene mutations for AML is discussed. English language articles were scrutinized in plentiful directories or databases like PubMed, Science Direct, Web of Sciences, Google Scholar, and Scopus. The important keywords used for searching databases is "Acute myeloid leukemia", "Gene mutation in Acute myeloid leukemia", "Genetic alteration in Acute myeloid leukemia," and "Genetic abnormalities in Acute myeloid leukemia."

Plasmacytoid Dendritic Cells, a Novel Target in Myeloid Neoplasms

Plasmacytoid dendritic cells (pDC) are the main type I interferon producing cells in humans and are able to modulate innate and adaptive immune responses. Tumor infiltration by plasmacytoid dendritic cells is already well described and is associated with poor outcomes in cancers due to the tolerogenic activity of pDC. In hematological diseases, Blastic Plasmacytoid Dendritic Cells Neoplasm (BPDCN), aggressive leukemia derived from pDCs, is well described, but little is known about tumor infiltration by mature pDC described in Myeloid Neoplasms (MN). Recently, mature pDC proliferation (MPDCP) has been described as a differential diagnosis of BPDCN associated with acute myeloid leukemia (pDC-AML), myelodysplastic syndrome (pDC-MDS) and chronic myelomonocytic leukemia (pDC-CMML). Tumor cells are myeloid blasts and/or mature myeloid cells from related myeloid disorders and pDC derived from a clonal proliferation. The poor prognosis associated with MPDCP requires a better understanding of pDC biology, MN oncogenesis and immune response. This review provides a comprehensive overview about the biological aspects of pDCs, the description of pDC proliferation in MN, and an insight into putative therapies in pDC-AML regarding personalized medicine.

Molecular Basis of Hematological Disease Caused by Inherited or Acquired RUNX1 Mutations

The transcription factor RUNX1 is essential for correct hematopoietic development; in its absence in the germ line, blood stem cells are not formed. RUNX1 orchestrates dramatic changes in the chromatin landscape at the onset of stem cell formation, which set the stage for both stem self-renewal and further differentiation. However, once blood stem cells are formed, the mutation of the RUNX1 gene is not lethal but can lead to various hematopoietic defects and a predisposition to cancer. Here we summarize the current literature on inherited and acquired RUNX1 mutations, with a particular emphasis on mutations that alter the structure of the RUNX1 protein itself, and place these changes in the context of what is known about RUNX1 function. We also summarize which mutant RUNX1 proteins are actually expressed in cells and discuss the molecular mechanism underlying how such variants reprogram the epigenome setting stem cells on the path to malignancy.

Enrichment of Double RUNX1 Mutations in Acute Leukemias of Ambiguous Lineage

Acute leukemia of ambiguous lineage (ALAL) is a rare type of leukemia and represents an unmet clinical need. In fact, due to heterogeneity, substantial rarity and absence of clinical trials, there are no therapeutic guidelines available. We investigated the genetic basis of 10 cases of ALAL diagnosed at our centre from 2008 and 2020, through a targeted myeloid and lymphoid sequencing approach. We show that this rare group of acute leukemias is enriched in myeloid-gene mutations. In particular we found that RUNX1 mutations, which have been found double mutated in 40% of patients and tend to involve both alleles, are associated with an undifferentiated phenotype and with lineage ambiguity. Furthermore, because this feature is typical of acute myeloid leukemia with minimal differentiation, we believe that our data strengthen the idea that acute leukemia with ambiguous lineage, especially those with an undifferentiated phenotype, might be genetically more closer to acute myeloid leukemia rather than acute lymphoblastic leukemia. These data enrich the knowledge on the genetic basis of ALAL and could have clinical implications as an acute myeloid leukemia (AML) - oriented chemotherapeutic approach might be more appropriate.

Plasmacytoid dendritic cell expansion defines a distinct subset of RUNX1-mutated acute myeloid leukemia

Plasmacytoid dendritic cells (pDCs) are the principal natural type I interferon-producing dendritic cells. Neoplastic expansion of pDCs and pDC precursors leads to blastic plasmacytoid dendritic cell neoplasm (BPDCN), and clonal expansion of mature pDCs has been described in chronic myelomonocytic leukemia. The role of pDC expansion in acute myeloid leukemia (AML) is poorly studied. Here, we characterize patients with AML with pDC expansion (pDC-AML), which we observe in ∼5% of AML cases. pDC-AMLs often possess cross-lineage antigen expression and have adverse risk stratification with poor outcome. RUNX1 mutations are the most common somatic alterations in pDC-AML (>70%) and are much more common than in AML without pDC expansion and BPDCN. We demonstrate that pDCs are clonally related to, as well as originate from, leukemic blasts in pDC-AML. We further demonstrate that leukemic blasts from RUNX1-mutated AML upregulate a pDC transcriptional program, poising the cells toward pDC differentiation and expansion. Finally, tagraxofusp, a targeted therapy directed to CD123, reduces leukemic burden and eliminates pDCs in a patient-derived xenograft model. In conclusion, pDC-AML is characterized by a high frequency of RUNX1 mutations and increased expression of a pDC transcriptional program. CD123 targeting represents a potential treatment approach for pDC-AML.

RUNX1-mutated families show phenotype heterogeneity and a somatic mutation profile unique to germline predisposed AML

First reported in 1999, germline runt-related transcription factor 1 (RUNX1) mutations are a well-established cause of familial platelet disorder with predisposition to myeloid malignancy (FPD-MM). We present the clinical phenotypes and genetic mutations detected in 10 novel RUNX1-mutated FPD-MM families. Genomic analyses on these families detected 2 partial gene deletions, 3 novel mutations, and 5 recurrent mutations as the germline RUNX1 alterations leading to FPD-MM. Combining genomic data from the families reported herein with aggregated published data sets resulted in 130 germline RUNX1 families, which allowed us to investigate whether specific germline mutation characteristics (type, location) could explain the large phenotypic heterogeneity between patients with familial platelet disorder and different HMs. Comparing the somatic mutational signatures between the available familial (n = 35) and published sporadic (n = 137) RUNX1-mutated AML patients showed enrichment for somatic mutations affecting the second RUNX1 allele and GATA2. Conversely, we observed a decreased number of somatic mutations affecting NRAS, SRSF2, and DNMT3A and the collective genes associated with CHIP and epigenetic regulation. This is the largest aggregation and analysis of germline RUNX1 mutations performed to date, providing a unique opportunity to examine the factors underlying phenotypic differences and disease progression from FPD to MM.

Mutational landscape of chronic myeloid leukemia: more than a single oncogene leukemia

The BCR-ABL1 fusion gene, which causes aberrant kinase activity and uncontrolled cell proliferation, is the hallmark of chronic myeloid leukemia (CML). The development of tyrosine kinase inhibitors (TKI) that target the BCR-ABL oncoprotein has led to dramatic improvement in CML management. However, some challenges remain to be addressed in the TKI era, including patient stratification and the selection of frontline TKIs and CML progression. Additionally, with the emerging goal of treatment-free remission (TFR) in CML management, biomarkers that predict the outcomes of stopping TKI remain to be identified. Notably, recent reports have revealed the power of genome screening in understanding the role of genome aberrations other than BCR-ABL1 in CML pathogenesis. These studies have discovered the presence of disease-phase specific mutations and linked certain mutations to inferior responses to TKI treatment and CML progression. A personalized approach that incorporates genetic data in tailoring treatment strategies has been successfully implemented in acute leukemia, and it represents a promising approach for the management of high-risk CML patients. In this article, we will review current knowledge about the mutational profile in different phases of CML as well as patterns of mutational dynamics in patients having different outcomes. We highlight the effects of somatic mutations involving certain genes (e.g. epigenetic modifiers) on the outcomes of TKI treatment. We also discuss the potential value of incorporating genetic data in treatment decisions and the routine care of CML patients as a future direction for optimizing CML management.

Targeting RUNX1 in acute myeloid leukemia: preclinical innovations and therapeutic implications

Introduction: RUNX1 is an essential transcription factor for normal and malignant hematopoiesis. RUNX1 forms a heterodimeric complex with CBFB. Germline mutations and somatic alterations (i.e. translocations, mutations and abnormal expression) are frequently associated with acute myeloid leukemia (AML) with RUNX1 mutations conferring unfavorable prognosis. Therefore, RUNX1 constitutes a potential innovative and interesting therapeutic target. In this review, we discuss recent therapeutic advances of RUNX1 targeting in AML.Areas covered: Firstly, we cover the clinical basis for RUNX1 targeting. We have subdivided recent therapeutic approaches either by common biochemical pathways or by similar pharmacological targets. Genome editing of RUNX1 induces anti-leukemic effects; however, off-target events prohibit clinical use. Several molecules inhibit the interaction between RUNX1/CBFB and control AML development and progression. BET protein antagonists target RUNX1 (i.e. specific BET inhibitors, BRD4 shRNRA, proteolysis targeting chimeras (PROTAC) or expression-mimickers). All these molecules improve survival in mutant RUNX1 AML preclinical models.Expert opinion: Some of these novel molecules have shown encouraging anti-leukemic potency at the preclinical stage. A better understanding of RUNX1 function in AML development and progression and its key downstream pathways, may result in more precise and more efficient RUNX1 targeting therapies.

Explainable artificial intelligence in high-throughput drug repositioning for subgroup stratifications with interventionable potential

Enabling precision medicine requires developing robust patient stratification methods as well as drugs tailored to homogeneous subgroups of patients from a heterogeneous population. Developing de novo drugs is expensive and time consuming with an ultimately low FDA approval rate. These limitations make developing new drugs for a small portion of a disease population unfeasible. Therefore, drug repositioning is an essential alternative for developing new drugs for a disease subpopulation. This shows the importance of developing data-driven approaches that find druggable homogeneous subgroups within the disease population and reposition the drugs for these subgroups. In this study, we developed an explainable AI approach for patient stratification and drug repositioning. Contrast pattern mining and network analysis were used to discover homogeneous subgroups within a disease population. For each subgroup, a biomedical network analysis was done to find the drugs that are most relevant to a given subgroup of patients. The set of candidate drugs for each subgroup was ranked using an aggregated drug score assigned to each drug. The proposed method represents a human-in-the-loop framework, where medical experts use the data-driven results to generate hypotheses and obtain insights into potential therapeutic candidates for patients who belong to a subgroup. Colorectal cancer (CRC) was used as a case study. Patients' phenotypic and genotypic data was utilized with a heterogeneous knowledge base because it gives a multi-view perspective for finding new indications for drugs outside of their original use. Our analysis of the top candidate drugs for the subgroups identified by medical experts showed that most of these drugs are cancer-related, and most of them have the potential to be a CRC regimen based on studies in the literature.

Glucocorticoids enhance the antileukemic activity of FLT3 inhibitors in FLT3-mutant acute myeloid leukemia

FLT3 is a frequently mutated gene that is highly associated with a poor prognosis in acute myeloid leukemia (AML). Despite initially responding to FLT3 inhibitors, most patients eventually relapse with drug resistance. The mechanism by which resistance arises and the initial response to drug treatment that promotes cell survival is unknown. Recent studies show that a transiently maintained subpopulation of drug-sensitive cells, so-called drug-tolerant "persisters" (DTPs), can survive cytotoxic drug exposure despite lacking resistance-conferring mutations. Using RNA sequencing and drug screening, we find that treatment of FLT3 internal tandem duplication AML cells with quizartinib, a selective FLT3 inhibitor, upregulates inflammatory genes in DTPs and thereby confers susceptibility to anti-inflammatory glucocorticoids (GCs). Mechanistically, the combination of FLT3 inhibitors and GCs enhances cell death of FLT3 mutant, but not wild-type, cells through GC-receptor-dependent upregulation of the proapoptotic protein BIM and proteasomal degradation of the antiapoptotic protein MCL-1. Moreover, the enhanced antileukemic activity by quizartinib and dexamethasone combination has been validated using primary AML patient samples and xenograft mouse models. Collectively, our study indicates that the combination of FLT3 inhibitors and GCs has the potential to eliminate DTPs and therefore prevent minimal residual disease, mutational drug resistance, and relapse in FLT3-mutant AML.

Clinical Implications of Inflammation in Acute Myeloid Leukemia

Recent advances in the description of the tumor microenvironment of acute myeloid leukemia, including the comprehensive analysis of the leukemic stem cell niche and clonal evolution, indicate that inflammation may play a major role in many aspects of acute myeloid leukemia (AML) such as disease progression, chemoresistance, and myelosuppression. Studies on the mechanisms of resistance to chemotherapy or tyrosine kinase inhibitors along with high-throughput drug screening have underpinned the potential role of glucocorticoids in this disease classically described as steroid-resistant in contrast to acute lymphoblastic leukemia. Moreover, some mutated oncogenes such as RUNX1, NPM1, or SRSF2 transcriptionally modulate cell state in a manner that primes leukemic cells for glucocorticoid sensitivity. In clinical practice, inflammatory markers such as serum ferritin or IL-6 have a strong prognostic impact and may directly affect disease progression, whereas interesting preliminary data suggested that dexamethasone may improve the outcome for AML patients with a high white blood cell count, which paves the way to develop prospective clinical trials that evaluate the role of glucocorticoids in AML.

High frequency of germline RUNX1 mutations in patients with RUNX1-mutated AML

RUNX1 is mutated in ∼10% of adult acute myeloid leukemia (AML). Although most RUNX1 mutations in this disease are believed to be acquired, they can also be germline. Indeed, germline RUNX1 mutations result in the well-described autosomal-dominant familial platelet disorder with predisposition to hematologic malignancies (RUNX1-FPD, FPD/AML, FPDMM); ∼44% of affected individuals progress to AML or myelodysplastic syndromes. Using the Leucegene RUNX1 AML patient group, we sought to investigate the proportion of germline vs acquired RUNX1 mutations in this cohort. Our results showed that 30% of RUNX1 mutations in our AML cohort are germline. Molecular profiling revealed higher frequencies of NRAS mutations and other mutations known to activate various signaling pathways in these patients with RUNX1 germline-mutated AML. Moreover, 2 patients (mother and son) had co-occurrence of RUNX1 and CEBPA germline mutations, with variable AML disease onset at 59 and 27 years, respectively. Together, these data suggest a higher than anticipated frequency of germline RUNX1 mutations in the Leucegene cohort and further highlight the importance of testing for RUNX1 mutations in instances in which allogeneic stem cell transplantation using a related donor is envisioned.

RUNX1 mutations in blast-phase chronic myeloid leukemia associate with distinct phenotypes, transcriptional profiles, and drug responses

Blast-phase chronic myeloid leukemia (BP-CML) is associated with additional chromosomal aberrations, RUNX1 mutations being one of the most common. Tyrosine kinase inhibitor therapy has only limited efficacy in BP-CML, and characterization of more defined molecular subtypes is warranted in order to design better treatment modalities for this poor prognosis patient group. Using whole-exome and RNA sequencing we demonstrate that PHF6 and BCORL1 mutations, IKZF1 deletions, and AID/RAG-mediated rearrangements are enriched in RUNX1^mut BP-CML leading to typical mutational signature. On transcriptional level interferon and TNF signaling were deregulated in primary RUNX1^mut CML cells and stem cell and B-lymphoid factors upregulated giving a rise to distinct phenotype. This was accompanied with the sensitivity of RUNX1^mut blasts to CD19-CAR T cells in ex vivo assays. High-throughput drug sensitivity and resistance testing revealed leukemia cells from RUNX1^mut patients to be highly responsive for mTOR-, BCL2-, and VEGFR inhibitors and glucocorticoids. These findings were further investigated and confirmed in CRISPR/Cas9-edited homozygous RUNX1^−/− and heterozygous RUNX1^−/mut BCR-ABL positive cell lines. Overall, our study provides insights into the pathogenic role of RUNX1 mutations and highlights personalized targeted therapy and CAR T-cell immunotherapy as potentially promising strategies for treating RUNX1^mut BP-CML patients.

A transcriptomic continuum of differentiation arrest identifies myeloid interface acute leukemias with poor prognosis

Classification of acute lymphoblastic and myeloid leukemias (ALL and AML) remains heavily based on phenotypic resemblance to normal hematopoietic precursors. This framework can provide diagnostic challenges for immunophenotypically heterogeneous immature leukemias, and ignores recent advances in understanding of developmental multipotency of diverse normal hematopoietic progenitor populations that are identified by transcriptional signatures. We performed transcriptional analyses of a large series of acute myeloid and lymphoid leukemias and detected significant overlap in gene expression between cases in different diagnostic categories. Bioinformatic classification of leukemias along a continuum of hematopoietic differentiation identified leukemias at the myeloid/T-lymphoid interface, which shared gene expression programs with a series of multi or oligopotent hematopoietic progenitor populations, including the most immature CD34+CD1a−CD7− subset of early thymic precursors. Within these interface acute leukemias (IALs), transcriptional resemblance to early lymphoid progenitor populations and biphenotypic leukemias was more evident in cases originally diagnosed as AML, rather than T-ALL. Further prognostic analyses revealed that expression of IAL transcriptional programs significantly correlated with poor outcome in independent AML patient cohorts. Our results suggest that traditional binary approaches to acute leukemia categorization are reductive, and that identification of IALs could allow better treatment allocation and evaluation of therapeutic options.

A comprehensive review of genetic alterations and molecular targeted therapies for the implementation of personalized medicine in acute myeloid leukemia

Acute myeloid leukemia (AML) is an extremely heterogeneous disease defined by the clonal growth of myeloblasts/promyelocytes not only in the bone marrow but also in peripheral blood and/or tissues. Gene mutations and chromosomal abnormalities are usually associated with aberrant proliferation and/or block in the normal differentiation of hematopoietic cells. So far, the combination of cytogenetic profiling and molecular and gene mutation analyses remains an essential tool for the classification, diagnosis, prognosis, and treatment for AML. This review gives an overview on how the development of novel innovative technologies has allowed us not only to detect the genetic alterations as early as possible but also to understand the molecular pathogenesis of AML to develop novel targeted therapies. We also discuss the remarkable advances made during the last decade to understand the AML genome both at primary and relapse diseases and how genetic alterations might influence the distinct biological groups as well as the clonal evolution of disease during the diagnosis and relapse. Also, the review focuses on how the persistence of epigenetic gene mutations during morphological remission is associated with relapse. It is suggested that along with the prognostic and therapeutic mutations, the novel molecular targeted therapies either approved by FDA or those under clinical trials including CART-cell therapy would be of immense importance in the effective management of AML.

Secondary leukemia in patients with germline transcription factor mutations (RUNX1, GATA2, CEBPA)

Recognition that germline mutations can predispose individuals to blood cancers, often presenting as secondary leukemias, has largely been driven in the last 20 years by studies of families with inherited mutations in the myeloid transcription factors (TFs) RUNX1, GATA2, and CEBPA. As a result, in 2016, classification of myeloid neoplasms with germline predisposition for each of these and other genes was added to the World Health Organization guidelines. The incidence of germline mutation carriers in the general population or in various clinically presenting patient groups remains poorly defined for reasons including that somatic mutations in these genes are common in blood cancers, and our ability to distinguish germline (inherited or de novo) and somatic mutations is often limited by the laboratory analyses. Knowledge of the regulation of these TFs and their mutant alleles, their interaction with other genes and proteins and the environment, and how these alter the clinical presentation of patients and their leukemias is also incomplete. Outstanding questions that remain for patients with these germline mutations or their treating clinicians include: What is the natural course of the disease? What other symptoms may I develop and when? Can you predict them? Can I prevent them? and What is the best treatment? The resolution of many of the remaining clinical and biological questions and effective evidence-based treatment of patients with these inherited mutations will depend on worldwide partnerships among patients, clinicians, diagnosticians, and researchers to aggregate sufficient longitudinal clinical and laboratory data and integrate these data with model systems.

Harnessing Gene Expression Profiles for the Identification of Ex Vivo Drug Response Genes in Pediatric Acute Myeloid Leukemia

Novel treatment strategies are of paramount importance to improve clinical outcomes in pediatric AML. Since chemotherapy is likely to remain the cornerstone of curative treatment of AML, insights in the molecular mechanisms that determine its cytotoxic effects could aid further treatment optimization. To assess which genes and pathways are implicated in tumor drug resistance, we correlated ex vivo drug response data to genome-wide gene expression profiles of 73 primary pediatric AML samples obtained at initial diagnosis. Ex vivo response of primary AML blasts towards cytarabine (Ara C), daunorubicin (DNR), etoposide (VP16), and cladribine (2-CdA) was associated with the expression of 101, 345, 206, and 599 genes, respectively (p < 0.001, FDR 0.004–0.416). Microarray based expression of multiple genes was technically validated using qRT-PCR for a selection of genes. Moreover, expression levels of BRE, HIF1A, and CLEC7A were confirmed to be significantly (p < 0.05) associated with ex vivo drug response in an independent set of 48 primary pediatric AML patients. We present unique data that addresses transcriptomic analyses of the mechanisms underlying ex vivo drug response of primary tumor samples. Our data suggest that distinct gene expression profiles are associated with ex vivo drug response, and may confer a priori drug resistance in leukemic cells. The described associations represent a fundament for the development of interventions to overcome drug resistance in AML, and maximize the benefits of current chemotherapy for sensitive patients.

Clinical implications of recurrent gene mutations in acute myeloid leukemia

Acute myeloid leukemia (AML) is a genetically heterogeneous clonal malignancy characterized by recurrent gene mutations. Genomic heterogeneity, patients’ individual variability, and recurrent gene mutations are the major obstacles among many factors that impact treatment efficacy of the AML patients. With the application of cost- and time-effective next-generation sequencing (NGS) technologies, an enormous diversity of genetic mutations has been identified. The recurrent gene mutations and their important roles in acute myeloid leukemia (AML) pathogenesis have been studied extensively. In this review, we summarize the recent development on the gene mutation in patients with AML.

RUNX1 mutations enhance self-renewal and block granulocytic differentiation in human in vitro models and primary AMLs

To unravel molecular mechanisms by which Runt-related transcription factor 1 (RUNX1) mutations contribute to leukemic transformation, we introduced the RUNX1-S291fs300X mutation in human CD34⁺ stem/progenitor cells and in human induced pluripotent stem cells (iPSCs). In both models, RUNX1mut overexpression strongly impaired myeloid commitment. Instead, self-renewal was enhanced, as shown, by increased long-term culture-initiating cell frequencies and enhanced colony-forming cell replating capacity. Long-term suspension cultures with RUNX1mut-transduced cord blood (CB) CD34⁺ cells continued for more than 100 days, during which the cells displayed an immature granulocyte-macrophage progenitor-like CD34⁺/CD123⁺/CD45RA⁺ phenotype. The CD34⁺/CD38^- hematopoietic stem cell (HSC) population most likely acted as cell of origin, as HSCs provided the best long-term proliferative potential on overexpression of RUNX1mut. CEBPA expression was reduced in RUNX1mut cells, and reexpression of CEBPA partly restored differentiation. RNA-seq analysis on CB/iPSC systems and on primary patient samples confirmed that RUNX1 mutations induce a myeloid differentiation block, and that a common set of RUNX1mut-upregulated target genes was strongly enriched for gene ontology terms associated with nucleosome assembly and chromatin structure. Interestingly, in comparison with AML1-ETO binding in acute myeloid leukemias (AMLs), we found significantly distinct genomic distribution and differential expression for RUNX1mut of genes such as TCF4, MEIS1, and HMGA2 that may potentially contribute to the underlying difference in clinical outcomes between RUNX1mut and AML1-ETO patients. In conclusion, RUNX1mut appears to induce a specific transcriptional program that contributes to leukemic transformation.

UM171 induces a homeostatic inflammatory-detoxification response supporting human HSC self-renewal

Elucidation of the molecular cues required to balance adult stem cell self-renewal and differentiation is critical for advancing cellular therapies. Herein, we report that the hematopoietic stem cell (HSC) self-renewal agonist UM171 triggers a balanced pro- and anti-inflammatory/detoxification network that relies on NFKB activation and protein C receptor-dependent ROS detoxification, respectively. We demonstrate that within this network, EPCR serves as a critical protective component as its deletion hypersensitizes primitive hematopoietic cells to pro-inflammatory signals and ROS accumulation resulting in compromised stem cell function. Conversely, abrogation of the pro-inflammatory activity of UM171 through treatment with dexamethasone, cAMP elevating agents or NFkB inhibitors abolishes EPCR upregulation and HSC expansion. Together, these results show that UM171 stimulates ex vivo HSC expansion by establishing a critical balance between key pro- and anti-inflammatory mediators of self-renewal.

Influence of DNMT3A R882 mutations on AML prognosis determined by the allele ratio in Chinese patients

Background

The influence of DNMT3A R882 mutations on adult acute myeloid leukemia (AML) prognosis is still controversial presently. The influence of R882 allele ratio on drug response and prognosis of AML is unknown yet. Besides, it is obscure whether anthracyclines are involved in chemoresistance resulted from R882 mutations.

Methods

DNMT3A R882 mutations in 870 adult AML patients receiving standard induction therapy were detected by pyrosequencing. Associations of the mutants with responses to induction therapy and disease prognosis were analyzed.

Results

DNMT3A R882 mutations were detected in 74 (8.51%) patients and allele ratio of the mutations ranged from 6 to 50% in the cohort. After the first and second courses of induction therapy including aclarubicin, complete remission rates were significantly lower in carriers of the DNMT3A R882 mutants as compared with R882 wildtype patients (P = 0.022 and P = 0.038, respectively). Compared with R882 wild-type patients, those with the R882 mutations showed significantly shorter overall survival (OS) and disease-free survival (DFS) (P = 1.92 × 10⁻⁴ and P = 0.004, respectively). Patients with higher allele ratio of R882 mutations showed a significantly shorter OS as compared with the lower allele ratio group (P = 0.035).

Conclusion

Our results indicate that the impact of DNMT3A R882 mutations on AML prognosis was determined by the mutant-allele ratio and higher allele ratio could predict a worse prognosis, which might improve AML risk stratification. In addition, DNMT3A R882 mutations were associated with an inferior response to induction therapy with aclarubicin in Chinese AML patients.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1959-3) contains supplementary material, which is available to authorized users.

Mubritinib Targets the Electron Transport Chain Complex I and Reveals the Landscape of OXPHOS Dependency in Acute Myeloid Leukemia

To identify therapeutic targets in acute myeloid leukemia (AML), we chemically interrogated 200 sequenced primary specimens. Mubritinib, a known ERBB2 inhibitor, elicited strong anti-leukemic effects in vitro and in vivo. In the context of AML, mubritinib functions through ubiquinone-dependent inhibition of electron transport chain (ETC) complex I activity. Resistance to mubritinib characterized normal CD34⁺ hematopoietic cells and chemotherapy-sensitive AMLs, which displayed transcriptomic hallmarks of hypoxia. Conversely, sensitivity correlated with mitochondrial function-related gene expression levels and characterized a large subset of chemotherapy-resistant AMLs with oxidative phosphorylation (OXPHOS) hyperactivity. Altogether, our work thus identifies an ETC complex I inhibitor and reveals the genetic landscape of OXPHOS dependency in AML.

Leukemic stem cell signatures identify novel therapeutics targeting acute myeloid leukemia

Therapy for acute myeloid leukemia (AML) involves intense cytotoxic treatment and yet approximately 70% of AML are refractory to initial therapy or eventually relapse. This is at least partially driven by the chemo-resistant nature of the leukemic stem cells (LSCs) that sustain the disease, and therefore novel anti-LSC therapies could decrease relapses and improve survival. We performed in silico analysis of highly prognostic human AML LSC gene expression signatures using existing datasets of drug–gene interactions to identify compounds predicted to target LSC gene programs. Filtering against compounds that would inhibit a hematopoietic stem cell (HSC) gene signature resulted in a list of 151 anti-LSC candidates. Using a novel in vitro LSC assay, we screened 84 candidate compounds at multiple doses and confirmed 14 drugs that effectively eliminate human AML LSCs. Three drug families presenting with multiple hits, namely antihistamines (astemizole and terfenadine), cardiac glycosides (strophanthidin, digoxin and ouabain) and glucocorticoids (budesonide, halcinonide and mometasone), were validated for their activity against human primary AML samples. Our study demonstrates the efficacy of combining computational analysis of stem cell gene expression signatures with in vitro screening to identify novel compounds that target the therapy-resistant LSC at the root of relapse in AML.

Dexamethasone in hyperleukocytic acute myeloid leukemia

Patients with acute myeloid leukemia and a high white blood cell count are at increased risk of early death and relapse. Because mediators of inflammation contribute to leukostasis and chemoresistance, dexamethasone added to chemotherapy could improve outcomes. This retrospective study evaluated the impact of adding or not adding dexamethasone to chemotherapy in a cohort of 160 patients with at least 50×10⁹ white blood cells. In silico studies, primary samples, leukemic cell lines, and xenograft mouse models were used to explore the antileukemic activity of dexamethasone. There was no difference with respect to induction death rate, response, and infections between the 60 patients in the dexamethasone group and the 100 patients in the no dexamethasone group. Multivariate analysis showed that dexamethasone was significantly associated with improved relapse incidence (adjusted sub-HR: 0.30; 95% CI: 0.14–0.62; P=0.001), disease-free survival (adjusted HR: 0.50; 95% CI: 0.29–0.84; P=0.010), event-free survival (adjusted HR: 0.35; 95% CI: 0.21–0.58; P<0.001), and overall survival (adjusted HR: 0.41; 95% CI: 0.22–0.79; P=0.007). In a co-culture system, dexamethasone reduced the frequency of leukemic long-term culture initiating cells by 38% and enhanced the cytotoxicity of doxorubicin and cytarabine. In a patient-derived xenograft model treated with cytarabine, chemoresistant cells were enriched in genes of the inflammatory response modulated by dexamethasone. Dexamethasone also demonstrated antileukemic activity in NPM1-mutated samples. Dexamethasone may improve the outcome of acute myeloid leukemia patients receiving intensive chemotherapy. This effect could be due to the modulation of inflammatory chemoresistance pathways and to a specific activity in acute myeloid leukemia with NPM1 mutation.

Drug Repurposing for the Treatment of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a heterogeneous disease characterized by the accumulation of immature myeloid progenitor cells in the bone marrow, compromising of normal blood cell production and ultimately resulting in bone marrow failure. With a 20% overall survival rate at 5 years and 50% in the 18- to 65-year-old age group, new medicines are needed. It is proposed that development of repurposed drugs may be a part of the new therapy needed. AML is subdivided into recurrent molecular entities based on molecular genetics increasingly accessible for precision medicine. Novel therapy developments form a basis for novel multimodality therapy and include liposomal daunorubicin/cytarabine, broad or FLT3-specific tyrosine kinase inhibitors, Bcl-2 family inhibitors, selective inhibitors of nuclear export, metabolic inhibitors, and demethylating agents. The use of non-transplant immunotherapy is in early development in AML with the exceptional re-approval of a toxin-conjugated anti-CD33. However, the full potential of small molecule inhibitors and modalities like immunological checkpoint inhibitors, immunostimulatory small molecules, and CAR-T cell therapy is unknown. Some novel therapeutics will certainly benefit AML patient subgroups; however, due to high cost, more affordable alternatives are needed globally. Also the heterogeneity of AML will likely demand a broader repertoire of therapeutic molecules. Drug repurposing or repositioning represent a source for potential therapeutics with well-known toxicity profiles and reasonable prices. This implies that biomarkers of response need to accompany the development of antileukemic therapies for sharply defined patient subgroups. We will illustrate repurposing in AML with selected examples and discuss some experimental and regulatory limitations that may obstruct this development.