Wei-Na Zhang

DNMT3A Arg882 mutation drives chronic myelomonocytic leukemia through disturbing gene expression/DNA methylation in hematopoietic cells

Significance Epigenetic modifications are required for the regulation of hematopoiesis. DNA methyltransferase 3A (DNMT3A), a critical epigenetic modifier responsible for de novo DNA methylation, was reported recently to be a frequently mutated gene in hematopoietic malignancies. However, the role of mutated DNMT3A in hematopoiesis remains largely unknown. Here we show that the Arg882 (R882) mutation of DNMT3A disrupts the normal function of this enzyme and results in chronic myelomonocytic leukemia (CMML) in mice. Meanwhile, the gene expression, DNA methylation, and protein–protein interaction assays suggest that DNMT3A R882 mutation drives CMML by disturbing the transcriptional expression/DNA methylation program and cell-cycle regulation of hematopoietic cells. This study may shed light on the function of DNMT3A mutant in myeloid leukemogenesis. The gene encoding DNA methyltransferase 3A (DNMT3A) is mutated in ∼20% of acute myeloid leukemia cases, with Arg882 (R882) as the hotspot. Here, we addressed the transformation ability of the DNMT3A-Arg882His (R882H) mutant by using a retroviral transduction and bone marrow transplantation (BMT) approach and found that the mutant gene can induce aberrant proliferation of hematopoietic stem/progenitor cells. At 12 mo post-BMT, all mice developed chronic myelomonocytic leukemia with thrombocytosis. RNA microarray analysis revealed abnormal expressions of some hematopoiesis-related genes, and the DNA methylation assay identified corresponding changes in methylation patterns in gene body regions. Moreover, DNMT3A-R882H increased the CDK1 protein level and enhanced cell-cycle activity, thereby contributing to leukemogenesis.

Targeting of AML1-ETO in t(8;21) Leukemia by Oridonin Generates a Tumor Suppressor–Like Protein

Oridonin treats AML by generating a truncated version of the AML1-ETO oncoprotein that functions as a tumor suppressor. Herbal Fusion High-tech gadgets and designer medicines increasingly drive medical treatment. But newer isn’t always better, and there has been a revitalized push for “natural” and “herbal” remedies. Although evidence supporting some of these therapies is shaky at best, researchers have found solid scientific bases for others—isolating active compounds with well-established biological function. One such compound is oridonin. Originally identified as a component of the herb Isodon rubescens, oridonin selectively kills leukemic cells that express a particular oncoprotein. Now, Zhen et al. show us exactly how compound works. Acute myeloid leukemia (AML) is a cancer of myeloid cells in the blood and bone marrow. The AML1-ETO fusion protein—an oncoprotein that results from a chromosomal translocation found in a subset of AML patients—is cleaved as a result of oridonin exposure. In the current study, the authors demonstrated that oridonin has two functions within AML1-ETO+ AML cells. The drug bound and blocked components of the oxidative damage prevention system, glutathione and thioredoxin/thioredoxin reductase, which resulted in increased amounts of reactive oxygen species and activated caspase-3. Oridonin also specifically bound to AML1-ETO, causing it to be cleaved into a truncated version that acted as a tumor suppressor in the AML cells. These data show how a simple herb can contribute a lead compound for personalized therapy in AML1-ETO+ AML patients. Nearly 60% of acute myeloid leukemia (AML) patients with the t(8;21)(q22;q22) translocation fail to achieve long-term disease-free survival. Our previous studies demonstrated that oridonin selectively induces apoptosis of t(8;21) leukemia cells and causes cleavage of AML1-ETO oncoprotein resulting from t(8;21), but the underlying mechanisms remain unclear. We show that oridonin interacted with glutathione and thioredoxin/thioredoxin reductase to increase intracellular reactive oxygen species, which in turn activated caspase-3 in t(8;21) cells. Moreover, oridonin bound AML1-ETO, directing the enzymatic cleavage at aspartic acid 188 via caspase-3 to generate a truncated AML1-ETO (ΔAML1-ETO) and preventing the protein from further proteolysis. ΔAML1-ETO interacted with AML1-ETO and interfered with the trans-regulatory functions of remaining AML1-ETO oncoprotein, thus acting as a tumor suppressor that mediates the anti-leukemia effect of oridonin. Furthermore, oridonin inhibited the activity of c-Kit+ leukemia-initiating cells. Therefore, oridonin is a potential lead compound for molecular target–based therapy of leukemia.

Genomic Profiling of Adult and Pediatric B-cell Acute Lymphoblastic Leukemia.

Genomic landscapes of 92 adult and 111 pediatric patients with B-cell acute lymphoblastic leukemia (B-ALL) were investigated using next-generation sequencing and copy number alteration analysis. Recurrent gene mutations and fusions were tested in an additional 87 adult and 93 pediatric patients. Among the 29 newly identified in-frame gene fusions, those involving MEF2D and ZNF384 were clinically relevant and were demonstrated to perturb B-cell differentiation, with EP300-ZNF384 inducing leukemia in mice. Eight gene expression subgroups associated with characteristic genetic abnormalities were identified, including leukemia with MEF2D and ZNF384 fusions in two distinct clusters. In subgroup G4 which was characterized by ERG deletion, DUX4-IGH fusion was detected in most cases. This comprehensive dataset allowed us to compare the features of molecular pathogenesis between adult and pediatric B-ALL and to identify signatures possibly related to the inferior outcome of adults to that of children. We found that, besides the known discrepancies in frequencies of prognostic markers, adult patients had more cooperative mutations and greater enrichment for alterations of epigenetic modifiers and genes linked to B-cell development, suggesting difference in the target cells of transformation between adult and pediatric patients and may explain in part the disparity in their responses to treatment.

Rapid Diagnosis and Prognosis of de novo Acute Myeloid Leukemia by Serum Metabonomic Analysis

Acute myeloid leukemia (AML) is a life-threatening hematological disease. Novel diagnostic and prognostic markers will be essential for new therapeutics and for significantly improving the disease prognosis. To characterize the metabolic features associated with AML and search for potential diagnostic and prognostic methods, here we analyzed the phenotypic characteristics of serum metabolite composition (metabonome) in a cohort of 183 patients with de novo acute myeloid leukemia together with 232 age- and gender-matched healthy controls using (1)H NMR spectroscopy in conjunction with multivariate data analysis. We observed significant serum metabonomic differences between AML patients and healthy controls and between AML patients with favorable and intermediate cytogenetic risks. Such differences were highlighted by systems differentiations in multiple metabolic pathways including glycolysis/gluconeogenesis, TCA cycle, biosynthesis of proteins and lipoproteins, and metabolism of fatty acids and cell membrane components, especially choline and its phosphorylated derivatives. This demonstrated the NMR-based metabonomics as a rapid and less invasive method for potential AML diagnosis and prognosis. The serum metabolic phenotypes observed here indicated that integration of metabonomics with other techniques will be useful for better understanding the biochemistry of pathogenesis and progression of leukemia.

Functional features of RUNX1 mutants in acute transformation of chronic myeloid leukemia and their contribution to inducing murine full-blown leukemia

The BCR-ABL fusion protein generated by t(9;22)(q34;q11) in chronic myeloid leukemia (CML) plays an essential role in the pathogenesis of the myeloproliferative disorder status at the chronic phase of the disease, but progression from the chronic phase to blast crisis (BC) is believed to require additional mutations. To explore the underlying mechanisms for BC, which is characterized by a blockage of blood cell differentiation, we screened several genes crucial to hematopoiesis and identified 10 types of mutations in RUNX1 among 11 of 85 (12.9%) patients with acute transformation of CML. Most of the mutations occurred in the runt homology domain, including H78Q, W79C, R139G, D171G, R174Q, L71fs-ter94, and V91fs-ter94. Further studies indicated that RUNX1 mutants not only exhibited decreased transactivation activity but also had an inhibitory effect on the WT RUNX1. To investigate the leukemogenic effect of mutated RUNX1, H78Q and V91fs-ter94 were transduced into 32D cells or BCR-ABL-harboring murine cells, respectively. Consistent with the myeloblastic features of advanced CML patients with RUNX1 mutations, H78Q and V91fs-ter94 disturbed myeloid differentiation and induced a BC or accelerated phase-like phenotype in mice. These results suggest that RUNX1 abnormalities may promote acute myeloid leukemic transformation in a subset of CML patients.

Vibsanin B Preferentially Targets HSP90β, Inhibits Interstitial Leukocyte Migration, and Ameliorates Experimental Autoimmune Encephalomyelitis

Interstitial leukocyte migration plays a critical role in inflammation and offers a therapeutic target for treating inflammation-associated diseases such as multiple sclerosis. Identifying small molecules to inhibit undesired leukocyte migration provides promise for the treatment of these disorders. In this study, we identified vibsanin B, a novel macrocyclic diterpenoid isolated from Viburnum odoratissimum Ker-Gawl, that inhibited zebrafish interstitial leukocyte migration using a transgenic zebrafish line (TG:zlyz–enhanced GFP). We found that vibsanin B preferentially binds to heat shock protein (HSP)90β. At the molecular level, inactivation of HSP90 can mimic vibsanin B’s effect of inhibiting interstitial leukocyte migration. Furthermore, we demonstrated that vibsanin B ameliorates experimental autoimmune encephalomyelitis in mice with pathological manifestation of decreased leukocyte infiltration into their CNS. In summary, vibsanin B is a novel lead compound that preferentially targets HSP90β and inhibits interstitial leukocyte migration, offering a promising drug lead for treating inflammation-associated diseases.

Conditional knockin of Dnmt3a R878H initiates acute myeloid leukemia with mTOR pathway involvement

Significance DNMT3A is a critical epigenetic modifier and tumor suppressor in the hematopoietic system. This gene is frequently mutated in hematopoietic malignancies, including acute myeloid leukemia (AML), with Dnmt3a R878H being the most common mutant. By using a conditional knockin approach, this study shows that Dnmt3a R878H is sufficient to initiate AML and recapitulate human leukemic features in mice. The leukemia-initiating cells are enriched in hematopoietic stem/progenitor cells. Through gene expression profiling, DNA methylation and histone modification analysis, and functional tests on important regulators for cell proliferation and differentiation in an animal model, this study has not only discovered mTOR pathway activation as a key player in the disease mechanism but also revealed the potential therapeutic effects of mTOR inhibition on DNMT3A mutation-related leukemia. DNMT3A is frequently mutated in acute myeloid leukemia (AML). To explore the features of human AML with the hotspot DNMT3A R882H mutation, we generated Dnmt3a R878H conditional knockin mice, which developed AML with enlarged Lin−Sca1+cKit+ cell compartments. The transcriptome and DNA methylation profiling of bulk leukemic cells and the single-cell RNA sequencing of leukemic stem/progenitor cells revealed significant changes in gene expression and epigenetic regulatory patterns that cause differentiation arrest and growth advantage. Consistent with leukemic cell accumulation in G2/M phase, CDK1 was up-regulated due to mTOR activation associated with DNA hypomethylation. Overexpressed CDK1-mediated EZH2 phosphorylation resulted in an abnormal trimethylation of H3K27 profile. The mTOR inhibitor rapamycin elicited a significant therapeutic response in Dnmt3aR878H/WT mice.

Identification of fusion genes and characterization of transcriptome features in T-cell acute lymphoblastic leukemia

Significance To get more insights into the disease mechanism of T-cell acute lymphoblastic leukemia (T-ALL), particularly in an adult group, we addressed the genomic landscape in 130 patients, including 61 cases of adult T-ALL. A number of new genetic aberrations were identified using integrated transcriptome and genomic analysis. Distinct T-ALL subgroups were defined according to the interplay among different genetic abnormalities and gene transcription patterns. Characterization of genomic features of T-ALL is valuable not only for a better understanding of leukemogenesis, but also for patient stratification and tailored therapy. T-cell acute lymphoblastic leukemia (T-ALL) is a clonal malignancy of immature T cells. Recently, the next-generation sequencing approach has allowed systematic identification of molecular features in pediatric T-ALL. Here, by performing RNA-sequencing and other genomewide analysis, we investigated the genomic landscape in 61 adult and 69 pediatric T-ALL cases. Thirty-six distinct gene fusion transcripts were identified, with SET-NUP214 being highly related to adult cases. Among 18 previously unknown fusions, ZBTB16-ABL1, TRA-SALL2, and involvement of NKX2-1 were recurrent events. ZBTB16-ABL1 functioned as a leukemogenic driver and responded to the effect of tyrosine kinase inhibitors. Among 48 genes with mutation rates >3%, 6 were newly found in T-ALL. An aberrantly overexpressed short mRNA transcript of the SLC17A9 gene was revealed in most cases with overexpressed TAL1, which predicted a poor prognosis in the adult group. Up-regulation of HOXA, MEF2C, and LYL1 was often present in adult cases, while TAL1 overexpression was detected mainly in the pediatric group. Although most gene fusions were mutually exclusive, they coexisted with gene mutations. These genetic abnormalities were correlated with deregulated gene expression markers in three subgroups. This study may further enrich the current knowledge of T-ALL molecular pathogenesis.

Homoharringtonine synergy with oridonin in treatment of t(8; 21) acute myeloid leukemia

Collaboration of c-KIT mutations with AML1–ETO (AE) has been demonstrated to induce t(8; 21) acute myeloid leukemia (AML). Targeted therapies designed to eliminate AE and c-KIT oncoproteins may facilitate effective treatment of t(8; 21) AML. Homoharringtonine (HHT) features activity against tumor cells harboring c-KIT mutations, whereas oridonin can induce t(8; 21) AML cell apoptosis and AE cleavage. Therefore, studies should explore the efficacy of combination therapy with oridonin and HHT in t(8; 21) AML. In this study, we investigated the synergistic effects and mechanism of oridonin combined with HHT in t(8; 21) AML cell line and mouse model. The two drugs synergistically inhibited cell viability and induced significant mitochondrial membrane potential loss and apoptosis. Oridonin and HHT induced significant downregulation of c-KIT and its downstream signaling pathways and promoted AE cleavage. HHT increased intracellular oridonin concentration by modulating the expressions of MRP1 and MDR1, thus enhancing the effects of oridonin. The combination of oridonin and HHT prolonged t(8; 21) leukemia mouse survival. In conclusion, oridonin and HHTexert synergistic effects against t(8; 21) leukemia in vivo and in vitro, thereby indicating that their combination may be an effective therapy for t(8; 21) leukemia.