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Epigenetic silencing of microRNA-193a contributes to leukemogenesis in t(8;21) acute myeloid leukemia by activating the PTEN/PI3K signal pathway

t(8;21) is one of the most frequent chromosomal translocations occurring in acute myeloid leukemia (AML) and is considered the leukemia-initiating event. The biologic and clinical significance of microRNA dysregulation associated with AML1/ETO expressed in t(8;21) AML is unknown. Here, we show that AML1/ETO triggers the heterochromatic silencing of microRNA-193a (miR-193a) by binding at AML1-binding sites and recruiting chromatin-remodeling enzymes. Suppression of miR-193a expands the oncogenic activity of the fusion protein AML-ETO, because miR-193a represses the expression of multiple target genes, such as AML1/ETO, DNMT3a, HDAC3, KIT, CCND1, and MDM2 directly, and increases PTEN indirectly. Enhanced miR-193a levels induce G(1) arrest, apoptosis, and restore leukemic cell differentiation. Our study identifies miR-193a and PTEN as targets for AML1/ETO and provides evidence that links the epigenetic silencing of tumor suppressor genes miR-193a and PTEN to differentiation block of myeloid precursors. Our results indicated a feedback circuitry involving miR-193a and AML1/ETO/DNMTs/HDACs, cooperating with the PTEN/PI3K signaling pathway and contributing to leukemogenesis in vitro and in vivo, which can be successfully targeted by pharmacologic disruption of the AML1/ETO/DNMTs/HDACs complex or enhancement of miR-193a in t(8;21)-leukemias.

BCR-ABL/GATA1/miR-138 mini circuitry contributes to the leukemogenesis of chronic myeloid leukemia

Abnormal expression of microRNAs (miRNAs) has been implicated in carcinogenesis. Here we report a novel BCR (breakpoint cluster region)-ABL (c-abl oncogene 1, non-receptor tyrosine kinase)/GATA1/microRNA-138 (miR-138) circuitry in chronic myeloid leukemia (CML). miR-138 expression is downregulated in K562 cells and primary CML samples, which is restored after imatinib treatment. The tumor suppressor activity of miR-138 is demonstrated by the induction of cell cycle arrest at G0/G1, inhibition of cell proliferation and colony forming unit granulocyte-macrophage colony formation and enhanced imatinib-induced apoptosis in K562 and Ku812 cells overexpressing miR-138. Moreover, overexpression of miR-138 led to the downregulation of BCR-ABL. Based on luciferase assay, ABL and BCR-ABL are shown to be the target genes regulated by miR-138. Furthermore, miR-138 binding to ABL was shown to localize to the coding region instead of 3′-untranslated regions (3′-UTR) of ABL mRNA. In addition, CCND3 is another target of miR-138, which represses CCND3 expression by binding to its 3′-UTR. Finally, upregulation of miR-138 upon imatinib treatment is associated with the enhancement of GATA1 activity, which binds to the miR-138 promoter. In conclusion, miR-138 is a tumor suppressor miRNA underexpressed in CML. miR-138 represses expression of both BCR-ABL and CCND3 via binding to the coding region and 3′-UTR, respectively. miR-138 expression is activated by GATA1, which in turn is repressed by BCR-ABL. Therefore, miR-138, by virtue of a BCR-ABL/GATA1/miR-138 circuitry, is a tumor suppressor miRNA implicated in the pathogenesis of CML and its clinical response to imatinib.

Methylation-mediated repression of microRNA-143 enhances MLL-AF4 oncogene expression.

Fusion proteins containing the amino terminus of mixed lineage leukemia (MLL) are common in acute lymphoblastic leukemia (ALL) due to translocations. The MLL–AF4 fusion protein is generated by the translocation t(4;11)(q21;q23), and t(4;11)-positive ALL patients (MLL–AF4 ALL), have a notoriously poorer prognosis compared with patients with other MLL-associated leukemias. The detailed role of this fusion protein in leukemogenesis is not well understood. MicroRNAs (miRNAs) targeting the AF4 3′ untranslated regions may modulate MLL–AF4 fusion protein levels, raising the question of whether regulation of these miRNAs are involved in the progression of MLL–AF4 ALL. In this study, we show that miR-143 was identified as a regulator of MLL–AF4 expression in MLL–AF4 ALL samples. Restoration of miR-143 in MLL–AF4-positive RS4;11 and MV4-11 cells induced apoptosis, negatively contributing to leukemia cell growth by reducing MLL–AF4 fusion protein levels. Furthermore, miR-143 was epigenetically repressed by promoter hypermethylation in MLL–AF4-positive primary blasts and cell lines, but not in normal bone marrow cells and MLL–AF4-negative primary blasts, which was directly associated with expression of the MLL–AF4 oncogene. This is the first study to show that miR-143 functions as a tumor suppressor in MLL–AF4 B-cell ALL. These data reveal the therapeutic promise of upregulating miR-143 expression for MLL–AF4 B-cell ALL.

Unmanipulated HLA-mismatched/haploidentical peripheral blood stem cell transplantation for high-risk hematologic malignancies.

BACKGROUND: Haploidentical hematopoietic stem cell transplantation (HSCT) has been increasingly applied in high‐risk hematologic patients due to the absence of HLA‐matched donors. The aim of this study was to investigate the efficacy and safety of unmanipulated haploidentical allogeneic peripheral blood stem cells transplantation (PBSCT) for hematologic malignancies.

The epigenetically-regulated miR-663 targets H-ras in K-562 cells.

miR‐663 is a tumour suppressor that is potentially regulated by modification of CpG islands. Whether aberrant methylation is one of the reasons for miR‐663 down‐regulation in some malignant cells and whether miR‐663 targets oncogenes warrants further research. In the present study, we report that the CpG islands in the upstream region of pre‐miR‐663 are aberrantly methylated in the k‐562 cell line and in the white blood cells of some chronic myelogenous leukaemia patients, and also that H‐ras is one of the genes targeted by miR‐663. Over‐expression of miR‐663 may suppress proliferation of the k‐562 cell line in part by enhancing cell apoptosis.

MicroRNA-142-3p inhibits cell proliferation in human acute lymphoblastic leukemia by targeting the MLL-AF4 oncogene

The mixed-lineage leukemia (MLL)-AF4 fusion protein encoded by the chromosomal translocation t(4;11) predicts a poorer prognosis in acute lymphoblastic leukemia (ALL) than in other MLL-associated leukemias. However, the detailed mechanism underlying regulation of MLL-AF4 expression remains largely unknown. In this study, we showed that microRNA (miR)-142-3p was significantly downregulated in ALL patients expressing MLL-AF4. Upregulation of miR-142-3p decreased MLL-AF4 expression in the RS4;11 leukemic cell line, which suggests that MLL-AF4 is a direct target of miR-142-3p. Ectopic expression of miR-142-3p remarkably suppressed cell proliferation and induced apoptosis in RS4;11 cells expressing the MLL-AF4 fusion protein. We also found that exogenous expression of miR-142-3p strongly reduced the expression of MLL-AF4 target genes such as homeobox A (HOXA)9, HOXA7, and HOXA10 in RS4;11 cells. Taken together, our results indicate that miR-142-3p functions as a growth suppressor in MLL-AF4+ ALL, and its suppressive effects are mediated primarily through repression of MLL-AF4 expression.

Mutational spectrum and risk stratification of intermediate-risk acute myeloid leukemia patients based on next-generation sequencing

Intermediate-risk acute myeloid leukemia (IR-AML), which accounts for a substantial number of AML cases, is highly heterogeneous. Although several mutations have been identified, the heterogeneity of AML is uncertain because novel mutations have yet to be discovered. Here we applied next generation sequencing (NGS) platform to screen mutational hotspots in 410 genes relevant to hematological malignancy. IR-AML samples (N=95) were sequenced by Illumina Hiseq and mutations in 101 genes were identified. Only seven genes (CEBPA, NPM1, DNMT3A, FLT3-ITD, NRAS, IDH2 and WT1) were mutated in more than 10% of patients. Genetic interaction analysis identified several cooperative and exclusive patterns of overlapping mutations. Mutational analysis indicated some correlation between genotype and phenotype. FLT3-ITD mutations were identified as independent factors of poor prognosis, while CEBPA mutations were independent favorable factors. Co-occurrence of FLT3-ITD, NPM1 and DNMT3A mutations was identified with associated with specific clinical AML features and poor outcomes. Furthermore, by integrating multiple mutations in the survival analysis, 95 IR-AML patients could be stratified into three distinct risk groups allowing reductions in IR-AML by one-third. Our study offers deep insights into the molecular pathogenesis and biology of AML and indicated that the prognosis of IR-AML could be further stratified by different mutation combinations which may direct future treatment intervention.

AML1-ETO triggers epigenetic activation of early growth response gene l, inducing apoptosis in t(8;21) acute myeloid leukemia

The t(8;21)(q22;q22) translocation is the most common chromosomal translocation in acute myeloid leukemia (AML), and it gives rise to acute myeloid gene 1 (AML1)–myeloid transforming gene 8 (ETO)‐positive AML, which has a relatively favorable prognosis. However, the molecular mechanism related to a favorable prognosis in AML1–ETO‐positive AML is still not fully understood. Our results show that the AML1–ETO fusion protein triggered activation of early growth response gene l (EGR1) by binding at AML1‐binding sites on the EGR1 promoter and, subsequently, recruiting acetyltransferase P300, which is known to acetylate histones. However, AML1–ETO could not recruit DNA methyltransferases and histone deacetylases; therefore, EGR1 expression was affected by histone acetylation but not by DNA methylation. Both transcription and translation of EGR1 were higher in AML1–ETO‐positive AML cell lines than in AML1–ETO‐negative AML cell lines, owing to acetylation. Furthermore, when AML1–ETO‐positive AML cell lines were treated with C646 (P300 inhibitor) and trichostatin A (histone deacetylase inhibitor), EGR1 expression was significantly decreased and increased, respectively. In addition, treatment with 5‐azacytidine (methyltransferase inhibitor) did not cause any significant change in EGR1 expression. Overexpression of EGR1 inhibited cell proliferation and promoted apoptosis, and EGR1 knockout promoted cell proliferation. Thus, EGR1 could be a novel prognostic factor for a favorable outcome in AML1–ETO‐positive AML. The results of our study may explain the molecular mechanisms underlying the favorable prognosis in AML1–ETO‐positive AML.

Efficacy of Allogeneic Hematopoietic Stem Cell Transplantation in Intermediate-Risk Acute Myeloid Leukemia Adult Patients in First Complete Remission: A Meta-Analysis of Prospective Studies

Hematopoietic stem cell transplantation (HSCT) and consolidation chemotherapy have been used to treat intermediate-risk acute myeloid leukemia (AML) patients in first complete remission (CR1). However, it is still unclear which treatments are most effective for these patients. The aim of our study was to analyze the relapse-free survival (RFS) and overall survival (OS) benefit of allogeneic HSCT (alloHSCT) for intermediate-risk AML patients in CR1. A meta-analysis of prospective trials comparing alloHSCT to non-alloHSCT (autologous HSCT [autoHSCT] and/or chemotherapy) was undertaken. We systematically searched PubMed, Embase, and the Cochrane Library though October 2014, using keywords and relative MeSH or Emtree terms, ‘allogeneic’; ‘acut*’ and ‘leukem*/aml/leukaem*/leucem*/leucaem*’; and ‘nonlympho*’ or ‘myelo*’. A total of 7053 articles were accessed. The primary outcomes were RFS and OS, while the secondary outcomes were treatment-related mortality (TRM) and relapse rate (RR). Hazard ratios (HR) and 95% confidence intervals (CI) were calculated for each outcome. The primary outcomes were RFS and OS, while the secondary outcomes were TRM and RR. We included 9 prospective controlled studies including 1950 adult patients. Patients with intermediate-risk AML in CR1 who received either alloHSCT or non-alloHSCT were considered eligible. AlloHSCT was found to be associated with significantly better RFS, OS, and RR than non-alloHSCT (HR, 0.684 [95% CI: 0.48, 0.95]; HR, 0.76 [95% CI: 0.61, 0.95]; and HR, 0.58 [95% CI: 0.45, 0.75], respectively). TRM was significantly higher following alloHSCT than non-alloHSCT (HR, 3.09 [95% CI: 1.38, 6.92]). However, subgroup analysis showed no OS benefit for alloHSCT over autoHSCT (HR, 0.99 [95% CI: 0.70, 1.39]). In conclusion, alloHSCT is associated with more favorable RFS, OS, and RR benefits (but not TRM outcomes) than non-alloHSCT generally, but does not have an OS advantage over autoHSCT specifically, in patients with intermediate-risk AML in CR1.

Similar incidence of severe acute GVHD and less severe chronic GVHD in PBSCT from unmanipulated, haploidentical donors compared with that from matched sibling donors for patients with haematological malignancies

The features of graft‐versus‐host disease (GVHD) were compared between patients who underwent myeloablative conditioning and received a peripheral blood stem cell transplant (PBSCT) from either a haploidentical donor (HID) or a matched sibling donor (MSD) during the same period of time. The HID group included more patients with advanced disease. Both groups received the same GVHD prophylaxis with the addition of antithymoglobulin (ATG) in HID group. Higher cumulative incidences (CI) of acute GVHD grade 2–4 (35·1% vs. 13·9%, P = 0·003), similar CI of grade 3–4 (14·5% vs. 9·8%, P = 0·595), less 3‐year CI of extensive chronic GVHD (17·1% vs. 41·5%, P = 0·017) and less severe chronic GVHD (5·8% vs. 21·2%, P = 0·049) occurred in the HID group compared with the MSD group. There was no difference in the sites of the involved organs between these two groups. Higher 3‐year CI of non‐relapse mortality (24·0% vs. 10·2%, P = 0·014), relapse (39·0% vs. 22·6%, P = 0·032) and inferior disease‐free survival (45·7% vs. 78·9%, P = 0·000) were recorded in the HID cohort compared with the MSD group. More HID patients had Karnofsky scores above 90 than those in MSD group (P = 0·016). In conclusion, ATG plays a key role in the unmanipulated HID PBSCT protocol, producing better quality of life in survivors.