EVI1 oncoprotein expression and CtBP1-association oscillate through the cell cycle.

Aberrantly high expression of EVI1 in acute myeloid leukaemia (AML) is associated with poor prognosis. For targeted treatment of EVI1 overexpressing AML a more detailed understanding of aspects of spatiotemporal interaction dynamics of the EVI1 protein is important. EVI1 overexpressing SB1690CB AML cells were used for quantification and protein interaction studies of EVI1 and ΔEVI1. Cells were cell cycle-synchronised by mimosine and nocodazole treatment and expression of EVI1 and related proteins assessed by western blot, immunoprecipitation and immunofluorescence. EVI1 protein levels oscillate through the cell cycle, and EVI1 is degraded partly by the proteasome complex. Both EVI1 and ΔEVI1 interact with the co-repressor CtBP1 but dissociate from CtBP1 complexes during mitosis. Furthermore, a large fraction of EVI1, but not ΔEVI1 or CtBP1, resides in the nuclear matrix. In conclusion, EVI1- protein levels and EVI1-CtBP1 interaction dynamics vary though the cell cycle and differ between EVI1 and ΔEVI1. These data ad to the functional characterisation of the EVI1 protein in AML and will be important for the development of targeted therapeutic approaches for EVI1-driven AML.

Atypical 3q26/MECOM rearrangements genocopy inv(3)/t(3;3) in acute myeloid leukemia.

Acute myeloid leukemia (AML) with inv(3)/t(3;3)(q21q26) is a distinct World Health Organization recognized entity, characterized by its aggressive course and poor prognosis. In this subtype of AML, the translocation of a GATA2 enhancer (3q21) to MECOM (3q26) results in overexpression of the MECOM isoform EVI1 and monoallelic expression of GATA2 from the unaffected allele. The full-length MECOM transcript, MDS1-EVI1, is not expressed as the result of the 3q26 rearrangement. Besides the classical inv(3)/t(3;3), a number of other 3q26/MECOM rearrangements with poor treatment response have been reported in AML. Here, we demonstrate, in a group of 33 AML patients with atypical 3q26 rearrangements, MECOM involvement with EVI1 overexpression but no or low MDS1-EVI1 levels. Moreover, the 3q26 translocations in these AML patients often involve superenhancers of genes active in myeloid development (eg, CD164, PROM1, CDK6, or MYC). In >50% of these cases, allele-specific GATA2 expression was observed, either by copy-number loss or by an unexplained allelic imbalance. Altogether, atypical 3q26 recapitulate the main leukemic mechanism of inv(3)/t(3;3) AML, namely EVI1 overexpression driven by enhancer hijacking, absent MDS1-EVI1 expression and potential GATA2 involvement. Therefore, we conclude that both atypical 3q26/MECOM and inv(3)/t(3;3) can be classified as a single entity of 3q26-rearranged AMLs. Routine analyses determining MECOM rearrangements and EVI1 and MDS1-EVI1 expression are required to recognize 3q-rearranged AML cases.

Prognostic significance of the EVI1 gene expression in patients with acute myeloid leukemia: a meta-analysis.

Ecotropic virus integration site-1 (EVI1) is frequently expressed in patients with acute myeloid leukemia (AML). Many studies have reported the potential poor prognostic impact of EVI1 higher expression (EVI1H) in the AML patients; however, the conclusions previously reported have not been fully assessed and are still controversial. Therefore, we performed a meta-analysis to evaluate the prognostic significance of EVI1H in patients with AML. The primary endpoint was overall survival (OS), and the event-free survival (EFS) was selected as the secondary endpoint. We extracted the hazard ratio (HR) and their 95% confidence interval (CI) for the OS and EFS from the multivariate COX proportional hazard models. A total of 4767 AML patients from 11 studies up to 23 February 2019 were subjected to our meta-analysis. Pooled HRs suggested that EVI1H had an adverse impact on OS (HR = 1.52, 95%CI 1.24-1.86) and EFS (HR = 1.41, 95%CI 1.14-1.74) in AML patients. EVI1H was also associated with a shorter OS (HR = 1.73, 95%CI 1.43-2.11) and EFS (HR = 1.17, 95%CI 1.05-1.31) in AML patients with the intermediate cytogenetic risk (ICR) according to the National Comprehensive Cancer Network (NCCN), European leukemia network (ELN), or International System for Human Cytogenetic Nomenclature (ISCN). Furthermore, EVI1H appeared to be a poor prognosis indicator in patients with normal cytogenetics (NC) (HR for OS:2.01, 95%CI 1.32-3.05; HR for EFS 1.54, 95%CI 1.09-2.17) and young patients (HR for OS 1.30, 95%CI 1.09-1.55), respectively. This meta-analysis indicates EVI1H has an independent and significantly adverse prognostic impact on AML patients in the entire population, and this conclusion same applies to some subgroups like AML patients with ICR, NC, and young AML patients.

RUNX1-EVI1 induces dysplastic hematopoiesis and acute leukemia of the megakaryocytic lineage in mice.

The RUNX1-EVI1 gene generated by the t(3;21) translocation encodes a chimeric transcription factor and is a causative gene in the development of de novo acute megakaryoblastic leukemia and leukemic transformation of hematopoietic stem cell tumors. Heterozygous RUNX1-EVI1 knock-in mice die in utero due to hemorrhage in the central nervous system and spinal cord and complete abolishment of definitive hematopoiesis in the fetal liver. On the other hand, the chimeric knock-in mouse develops acute megakaryoblastic leukemia. We created another mouse model of RUNX1-EVI1 using transplantation of retrovirus-infected bone marrow cells. Some mice transplanted with RUNX1-EVI1-expressing bone marrow cells developed acute megakaryoblastic leukemia within eight months, and the other non-leukemic mice showed thrombocytosis at around a year. In the non-leukemic mice, dysplastic megakaryocytes proliferated in the bone marrow and frequently infiltrated into the spleen, which was not associated with marrow fibrosis. In the leukemic mice, their tumor cells were positive for c-kit and CD41, and negative for TER119. Although they were negative for platelet peroxidase in the electron microscopic analysis, they had multiple centrioles in the cytoplasm, which are characteristic of megakaryocytes that undergo endomitosis. The leukemic cells were serially transplantable, and gene-expression analyses using quantitative RT-PCR arrays revealed that they showed significantly elevated expression of stem cell, primitive hematopoietic cell and endothelial cell-related genes compared with normal bone marrow cells. All these data suggested that RUNX1-EVI1 caused dysplastic hematopoiesis or leukemia of the megakaryocytic lineage and endowed gene expression profiles distinctive of immature hematopoietic cells.

Acute Myeloid Leukemia (AML): Upregulation of BAALC/MN1/MLLT11/EVI1 Gene Cluster Relate With Poor Overall Survival and a Possible Linkage With Coexpression of MYC/BCL2 Proteins.

BACKGROUND: Molecular heterogeneity accounts for the variable and often poor prognosis in acute myeloid leukemia (AML). The current risk stratification strategy in clinical practice is limited to karyotyping and limited molecular studies screening for genetic mutations such as FLT-3 and NPM1. There is opportunity to identify further molecular prognostic markers, which may also lay the groundwork for the development of novel targeted therapies. Complex molecular technologies require transition into widely available laboratory platforms, for better integration into routine clinical practice. METHOD: In a defined subset (MYC/BCL2 or MYC/BCL2) of AML patients (n=20), we examined expression signature of several genes (n=12) of established prognostic value in AML. RNA expression and MYC/BCL2 protein pattern was correlated with 3 cytogenetic risk groups and overall survival. RESULTS: K-means++ unsupervised clustering defined 2 distinct groups with high and low transcript levels of BAALC/MN1/MLLT11/EVI1/SOCS2 genes (>2.5-fold difference; P<0.001). This mRNA signature trended with higher prevalence of MYC/BCL2 coexpression (P<0.057) and poor overall survival (P<0.036), but did not correlate with conventional cytogenetic risk groups (P<0.084). CONCLUSIONS: This pilot study provides useful data, which may help further refine the prognostic scheme of AML patients outside conventional cytogenetic risk groups. It also presents some biological rationale for future studies to explore the use of novel agents targeting MYC and/or BCL2 genes in combination with conventional chemotherapy protocols for AML.

Imbalanced expression of polycistronic miRNA in acute myeloid leukemia.

miR-1 and miR-133 are clustered on the same chromosomal loci and are transcribed together as a single transcript that is positively regulated by ecotropic virus integration site-1 (EVI1). Previously, we described how miR-133 has anti-tumorigenic potential through repression of EVI1 expression. It has also been reported that miR-1 is oncogenic in the case of acute myeloid leukemia (AML). Here, we show that expression of miR-1 and miR-133, which have distinct functions, is differentially regulated between AML cell lines. Interestingly, the expression of miR-1 and EVI1, which binds to the promoter of the miR-1/miR-133 cluster, is correlative. The expression levels of TDP-43, an RNA-binding protein that has been reported to increase the expression, but inhibits the activity, of miR-1, were not correlated with expression levels of miR-1 in AML cells. Taken together, our observations raise the possibility that the balance of polycistronic miRNAs is regulated post-transcriptionally in a hierarchical manner possibly involving EVI1, suggesting that the deregulation of this balance may play some role in AML cells with high EVI1 expression.