Expression and prognostic significance of different mRNA 5'-end variants of the oncogene EVI1 in 266 patients with de novo AML: EVI1 and MDS1/EVI1 overexpression both predict short remission duration

Rare Hematologic Malignancies and Pre-Leukemic Entities in Children and Adolescents Young Adults

There are a variety of rare hematologic malignancies and germline predispositions syndromes that occur in children and adolescent young adults (AYAs). These entities are important to recognize, as an accurate diagnosis is essential for risk assessment, prognostication, and treatment. This descriptive review summarizes rare hematologic malignancies, myelodysplastic neoplasms, and germline predispositions syndromes that occur in children and AYAs. We discuss the unique biology, characteristic genomic aberrations, rare presentations, diagnostic challenges, novel treatments, and outcomes associated with these rare entities.

EVI1-mediated Programming of Normal and Malignant Hematopoiesis

Ecotropic viral integration site 1 (EVI1), encoded at the MECOM locus, is an oncogenic zinc finger transcription factor with diverse roles in normal and malignant cells, most extensively studied in the context of hematopoiesis. EVI1 interacts with other transcription factors in a context-dependent manner and regulates transcription and chromatin remodeling, thereby influencing the proliferation, differentiation, and survival of cells. Interestingly, it can act both as a transcriptional activator as well as a transcriptional repressor. EVI1 is expressed, and fulfills important functions, during the development of different tissues, including the nervous system and hematopoiesis, demonstrating a rigid spatial and temporal expression pattern. However, EVI1 is regularly overexpressed in a variety of cancer entities, including epithelial cancers such as ovarian and pancreatic cancer, as well as in hematologic malignancies like myeloid leukemias. Importantly, EVI1 overexpression is generally associated with a very poor clinical outcome and therapy-resistance. Thus, EVI1 is an interesting candidate to study to improve the prognosis and treatment of high-risk patients with "EVI1high" hematopoietic malignancies.

The adverse impact of ecotropic viral integration site-1 (EVI1) overexpression on the prognosis of acute myeloid leukemia with KMT2A gene rearrangement in different risk stratification subtypes

INTRODUCTION

AML patients with KMT2A-MLLT3 and other 11q23 abnormalities belong to the intermediate and high-risk level groups, respectively. Whether the poor prognostic value of Ecotropic Viral Integration site-1 (EVI1) overexpression suits either the subtypes of KMT2A-MLLT3 or Non-KMT2A-MLLT3 AML patients (intermediate and high risk group) needs to be further investigated.

METHODS

We retrospectively analyzed the clinical characteristics of 166 KMT2A-r and KMT2A-PTD AML patients.

RESULTS

For the Non-KMT2A-MLLT3 group, patients in the EVI1-high subgroup had shorter OS and DFS and higher CIR than those in the EVI1-low subgroup (p = .027, p = .018, and p = .020, respectively). Additionally, both KMT2A-MLLT3 and Non-KMT2A-MLLT3 patients who received chemotherapy alone had poorer prognosis than patients who also received allogeneic hematopoietic stem cell transplant (allo-HSCT) regardless of their EVI1 expression level (all p < .001). For transplanted patients with KMT2A-MLLT3 or Non-KMT2A-MLLT3 rearrangement, the EVI1-high subgroup had worse prognosis than the EVI1-low subgroup (all p < .05). The 2-year CIR of the KMT2A-MLLT3 and Non-KMT2A-MLLT3 groups with high EVI1 expression was high (52% and 49.6%, respectively). However, for patients with low EVI1 expression, the 2-year CIR of transplanted patients with KMT2A-MLLT3 and Non-KMT2A-MLLT3 was relatively low.

CONCLUSIONS

Our study showed that for the Non-KMT2A-MLLT3 group, the EVI1-high group had shorter OS and DFS than the EVI1-low group. High EVI1 expression showed an adverse effect in AML with KMT2A rearrangement in different risk stratification subtypes. For the EVI1-high patients with non-KMT2A-MLLT3 rearrangement, other novel regimens towards relapse should be taken into consideration.

Clinical significance of EVI-1 gene expression and aberrations in patient with de-novo acute myeloid and acute lymphoid leukemia

BACKGROUND

Acute leukemia is a common health problem in adults and children, however its exact molecular etiology is still unclear.

METHODS

The expression of EVI-1 was assessed in the bone marrow of 178 de-novo acute leukemia patients (101 AML, 71 ALL and 6 MPAL), compared to 40 control subjects. EVI-1 gene aberrations were also assessed in 69 AML patients using Fluorescence in situ hybridization (FISH) technique.

RESULTS

The expression of EVI-1 was significantly lower in ALL patients compared to control [0.177 (0.002-15.189) vs 0.953 (0.179-1.68); respectively, P = 0.009]. There was no significant difference between AML patients and control group [0.150 (0.0-641) vs 0.953 (0.179-1.68); respectively, P = 0.082]. The sensitivity, specificity, AUC of EVI-1 in ALL were (80.3 %, 60 % and 0.778; respectively, P = 0.009), and (67.3 %, 60 %, 0.667; respectively P = 0.082) in AML patients. One patient showed EVI-1 gene rearrangement in a complex karyotype and four patients showed EVI-1 amplification in hyperdiploid karyotypes. All patients with BCR-ABL fusion were EVI-1 over-expressers (P = 0.010). AML patients with EVI-1 low expression were positively associated with t(8;21)(q22;q22)RUNX1:RUNX1T1 fusion, favorable recurrent translocation, and low genetic risk (P = 0.037, P = 0.023, and P = 0.013; respectively). There was a significant association between low EVI-1 expression and prolonged overall survival (OS) in AML patients, while there was no significant association with the disease-free survival (DFS) (P = 0.048 and P = 0.419). There was no significant impact of EVI-1 expression on OS and DFS rates in ALL patients.

CONCLUSION

EVI-1 expression could be a helpful diagnostic, prognostic, and predictive biomarker for acute leukemia especially in AML.

Clinical features and prognostic implications of ecotropic viral integration site 1 (EVI1) in childhood acute lymphoblastic leukemia

In contrast to the extensive knowledge on EVI1 in myeloid malignancies, few data are available on the EVI1 transcript in pediatric ALL. The purpose of this study was to examine the clinical and biological significance of EVI1 and validate its prognostic significance in pediatric patients with ALL. Here, we examined the clinical and biological significance of EVI1 expression, as measured by real-time polymerase chain reaction (PCR) in 837 children with newly diagnosed ALL treated on the National Protocol of Childhood Leukemia in China (NPCLC)-ALL-2008 protocol, and aimed to explore their prognostic significance in pediatric ALL patients. The EVI1 expression was detected in 27 of 837 (3.2%) patients. No statistically significant differences in prednisone response, complete remission (CR) rates and relapse rates were found between EVI1 overexpression (EVI1⁺) group and EVI1^- group. Moreover, we found no significant difference in event-free survival (EFS) and overall survival (OS) between these two groups, also multivariate analysis did not identify EVI1⁺ as an independent prognostic factor. In the subgroup analysis, there was no difference in clinical outcome between EVI1⁺ and EVI1^- patients in standard‑risk (SR), intermediate-risk (IR) and high-risk (HR) groups. In the minimal residual disease (MRD)<10^-4 group, EVI1⁺ patients have significantly lower EFS and OS rates compared to EVI1^- patients. Further large‑scale and well‑designed prospective studies are required to confirm the results in the future.

MECOM gene overexpression in pediatric patients with acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) is characterized by blocked or aberrant differentiation of hematopoietic stem cells. The MECOM gene overexpression in hematopoietic progenitors induces myeloid differentiation block, resulting in increased self-renewal and survival of these transformed progenitors. However, its exact role in AML remains unclear. We aimed to estimate the prevalence of MECOM overexpression among pediatric AML patients, and assess its impact on clinical outcome.

PATIENTS AND METHODS

Real-time quantitative polymerase chain reaction and Livak method (2^ΔΔCt) were used to determine relative MECOM expression level among 243 pediatric patients with AML. MECOM overexpression was considered if the cumulative relative expression was above 1 (2^-ΔΔCt) and was designated as MECOM^pos.

RESULTS

Of 243 AML patients tested 57(23.5%) demonstrated MECOM^pos. Patients with MECOM^pos had significantly lower median age. The frequency of MECOM^pos was significantly higher among AML patients with 11q23 abnormalities, complex karyotypes and among high- and intermediate-risk groups compared to low-risk group (p = .014). MECOM^pos patients had significantly lower overall survival (OS) (38.7 vs. 78.9%, p < .001), event-free survival (EFS) (37.3% vs. 68.4%, p < .001), and had higher cumulative incidence of relapse (49.5% vs. 23.5%, p = .002) at 36 months compared to MECOM^neg patients. Multivariate analysis revealed that MECOM^pos was an adverse prognostic factor for OS (hazards ratio (HR) = 2.11, 95% confidence interval (CI) 1.24-3.60, p = .006) and EFS (HR= 1.71, 95% CI 1.07-2.75, p = .025). The logistic regression model showed that MECOM^pos was an independent prognostic factor regardless of minimal residual disease status post first induction therapy in the intermediate-risk group (odds ratio 2.89; 95% CI 1.19-6.57, p = .018).

CONCLUSION

The aberrant MECOM gene expression is an adverse prognostic factor, especially in patients without previously known cytogenetic risk factors. Our results suggest the potential benefit from pretreatment screening for MECOM gene overexpression in newly diagnosed AML patients for better risk stratification and treatment adjustment.

EVI1 Promotes the Proliferation and Invasive Properties of Human Head and Neck Squamous Cell Carcinoma Cells

Head and neck squamous cell carcinoma (HNSCC) is a frequent malignancy with a poor prognosis. So far, the EGFR inhibitor cetuximab is the only approved targeted therapy. A deeper understanding of the molecular and genetic basis of HNSCC is needed to identify additional targets for rationally designed, personalized therapeutics. The transcription factor EVI1, the major product of the MECOM locus, is an oncoprotein with roles in both hematological and solid tumors. In HNSCC, high EVI1 expression was associated with an increased propensity to form lymph node metastases, but its effects in this tumor entity have not yet been determined experimentally. We therefore overexpressed or knocked down EVI1 in several HNSCC cell lines and determined the impact of these manipulations on parameters relevant to tumor growth and invasiveness, and on gene expression patterns. Our results revealed that EVI1 promoted the proliferation and migration of HNSCC cells. Furthermore, it augmented tumor spheroid formation and the ability of tumor spheroids to displace an endothelial cell layer. Finally, EVI1 altered the expression of numerous genes in HNSCC cells, which were enriched for Gene Ontology terms related to its cellular functions. In summary, EVI1 represents a novel oncogene in HNSCC that contributes to cellular proliferation and invasiveness.

Therapeutic Use of Valproic Acid and All-Trans Retinoic Acid in Acute Myeloid Leukemia-Literature Review and Discussion of Possible Use in Relapse after Allogeneic Stem Cell Transplantation

Even though allogeneic stem cell transplantation is the most intensive treatment for acute myeloid leukemia (AML), chemo-resistant leukemia relapse is still one of the most common causes of death for these patients, as is transplant-related mortality, i.e., graft versus host disease, infections, and organ damage. These relapse patients are not always candidates for additional intensive therapy or re-transplantation, and many of them have decreased quality of life and shortened expected survival. The efficiency of azacitidine for treatment of posttransplant AML relapse has been documented in several clinical trials. Valproic acid is an antiepileptic fatty acid that exerts antileukemic activity through histone deacetylase inhibition. The combination of valproic acid and all-trans retinoic acid (ATRA) is well tolerated even by unfit or elderly AML patients, and low-toxicity chemotherapy (e.g., azacitidine) can be added to this combination. The triple combination of azacitidine, valproic acid, and ATRA may therefore represent a low-intensity and low-toxicity alternative for these patients. In the present review, we review and discuss the general experience with valproic acid/ATRA in AML therapy and we discuss its possible use in low-intensity/toxicity treatment of post-allotransplant AML relapse. Our discussion is further illustrated by four case reports where combined treatments with sequential azacitidine/hydroxyurea, valproic acid, and ATRA were used.

Evi1 Counteracts Anti-Leukemic and Stem Cell Inhibitory Effects of All-Trans Retinoic Acid on Flt3-ITD/Npm1c-Driven Acute Myeloid Leukemia Cells

All-trans retinoic acid (atRA) has a dramatic impact on the survival of patients with acute promyelocytic leukemia, but its therapeutic value in other types of acute myeloid leukemia (AML) has so far remained unclear. Given that AML is a stem cell-driven disease, recent studies have addressed the effects of atRA on leukemic stem cells (LSCs). atRA promoted stemness of MLL-AF9-driven AML in an Evi1-dependent manner but had the opposite effect in Flt3-ITD/Nup98-Hoxd13-driven AML. Overexpression of the stem cell-associated transcription factor EVI1 predicts a poor prognosis in AML, and is observed in different genetic subtypes, including cytogenetically normal AML. Here, we therefore investigated the effects of Evi1 in a mouse model for cytogenetically normal AML, which rests on the combined activity of Flt3-ITD and Npm1c mutations. Experimental expression of Evi1 on this background strongly promoted disease aggressiveness. atRA inhibited leukemia cell viability and stem cell-related properties, and these effects were counteracted by overexpression of Evi1. These data further underscore the complexity of the responsiveness of AML LSCs to atRA and point out the need for additional investigations which may lay a foundation for a precision medicine-based use of retinoids in AML.

EVI1 in Leukemia and Solid Tumors

Simple Summary

Ecotropic viral integration site 1 (EVI1) is transcriptionally activated in a subset of myeloid leukemias. Since its discovery, other isoforms of EVI1 have been identified. It has been shown that EVI1 and its isoforms mainly function as transcription factors and to play important roles not only in leukemia but also in a variety of solid tumors. To provide a comprehensive understanding of this family of proteins, we summarize the currently available knowledge of expression and function of EVI1 and its isoforms in leukemia and solid tumors and provide insights of future studies.

Abstract

The EVI1 gene encodes for a transcription factor with two zinc finger domains and is transcriptionally activated in a subset of myeloid leukemias. In leukemia, the transcriptional activation of EVI1 usually results from chromosomal rearrangements. Besides leukemia, EVI1 has also been linked to solid tumors including breast cancer, lung cancer, ovarian cancer and colon cancer. The MDS1/EVI1 gene is encoded by the same locus as EVI1. While EVI1 functions as a transcription repressor, MDS1/EVI1 acts as a transcription activator. The fusion protein encoded by the AML1/MDS1/EVI1 chimeric gene, resulting from chromosomal translocations in a subset of chronic myeloid leukemia, exhibits a similar function to EVI1. EVI1 has been shown to regulate cell proliferation, differentiation and apoptosis, whereas the functions of MDS1/EVI1 and AML1/MDS1/EVI1 remain elusive. In this review, we summarize the genetic structures, biochemical properties and biological functions of these proteins in cancer.

All-trans retinoic acid in non-promyelocytic acute myeloid leukemia: driver lesion dependent effects on leukemic stem cells

Acute myeloid leukemia (AML) is an aggressive, often fatal hematopoietic malignancy. All-trans retinoic acid (atRA), one of the first molecularly targeted drugs in oncology, has greatly improved the outcome of a subtype of AML, acute promyelocytic leukemia (APL). In contrast, atRA has so far provided little therapeutic benefit in the much larger group of patients with non-APL AML. Attempts to identify genetically or molecularly defined subgroups of patients that may respond to atRA have not yielded consistent results. Since AML is a stem cell-driven disease, understanding the effectiveness of atRA may require an appreciation of its impact on AML stem cells. Recent studies reported that atRA decreased stemness of AML with an FLT3-ITD mutation, yet increased it in AML1-ETO driven or EVI1-overexpressing AML. This review summarizes the role of atRA in normal hematopoiesis and in AML, focusing on its impact on AML stem cells.

The role of EVI1 gene quantification in AML patients with 11q23/MLL rearrangement after allogeneic hematopoietic stem cell transplantation

It remains unclear about the role of the EVI1 gene in AML patients with 11q23/MLL rearrangement (MLL-r AML) undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). We analyzed the clinical value of EVI1 gene quantification in 96 MLL-r AML patients. High EVI1 expression was found in 73% (70/96) of MLL-r AML patients, and EVI1-high MLL-r AML patients were characterized by high WBC counts (P = 0.046) and low platelet counts (P < 0.001) and commonly had t(6;11) (P = 0.032). In addition, a significant difference was observed in the SETD2 gene mutation between the EVI1 high and low groups (0% vs. 50%, P < 0.001). EVI1-high MLL-r AML patients had worse 2-year OS (49.8% vs. 79.7%, P = 0.01) and 2-year PFS (40.2% vs. 68.1%, P = 0.014) than EVI1-low patients. In 57 MLL-r AML patients undergoing allo-HSCT, poorer 2-year PFS (48.6% vs. 72.4%, P = 0.039) and higher CIR (33.2% vs. 11.1%, P = 0.035) were observed in the EVI1-high patients. Multivariate analysis revealed that pre-EVI1⁺ was the sole independent factor of high CIR (P = 0.035, HR = 4.97, 95% CI: 1.12-22.04). EVI1⁺ at 100 days post allo-HSCT was associated with a significantly higher 2-year CIR (P = 0.017). The quantification of the EVI1 gene could be used as an additional marker for early predicting relapse in allo-HSCT MLL-r AML patients.

Role of miR-96/EVI1/miR-449a Axis in the Nasopharyngeal Carcinoma Cell Migration and Tumor Sphere Formation

The Wnt signaling pathway is one of the major signaling pathways used by cancer stem cells (CSC). Ecotropic Viral Integration Site 1 (EVI1) has recently been shown to regulate oncogenic development of tumor cells by interacting with multiple signaling pathways, including the Wnt signaling. In the present study, we found that the Wnt modulator ICG-001 could inhibit the expression of EVI1 in nasopharyngeal carcinoma (NPC) cells. Results from loss-of-function and gain-of-function studies revealed that EVI1 expression positively regulated both NPC cell migration and growth of CSC-enriched tumor spheres. Subsequent studies indicated ICG-001 inhibited EVI1 expression via upregulated expression of miR-96. Results from EVI1 3′UTR luciferase reporter assay confirmed that EVI1 is a direct target of miR-96. Further mechanistic studies revealed that ICG-001, overexpression of miR-96, or knockdown of EVI1 expression could restore the expression of miR-449a. The suppressive effect of miR-449a on the cell migration and tumor sphere formation was confirmed in NPC cells. Taken together, the miR-96/EVI1/miR-449a axis is a novel pathway involved in ICG-001-mediated inhibition of NPC cell migration and growth of the tumor spheres.

MECOM rearrangement involving the MYC locus: Two additional patients with the rare translocation, t(3;8)(q26.2;q24), and molecular review

A relatively small subset of myeloid neoplasms involve rearrangements of cytoband 3q26.2. Such rearrangements are often in response to therapy and carry a poor prognosis. The ectopic expression of MECOM is the result of such translocations. To date, thirty-three t(3;8)(q26.2;q24) cases have been reported; we contribute two patients with confirmed MECOM and MYC rearrangements. Both patients presented with pancytopenia and were diagnosed with myelodysplastic/myeloproliferative disorders. In addition to translocation t(3;8), Patient 1 possessed a derivative chromosome 5, while Patient 2 possessed monosomy 7; neither patient's clonal abnormalities resolved in follow-up studies. Of the previous 33 cases, one exhibited 5q loss, while monosomy 7 was found in fifteen. These findings contribute to the small number of reported cases with t(3;8) translocations. We also speculate about the molecular mechanisms associated with this translocation.

All-trans retinoic acid enhances, and a pan-RAR antagonist counteracts, the stem cell promoting activity of EVI1 in acute myeloid leukemia

Ecotropic virus integration site 1 (EVI1), whose overexpression characterizes a particularly aggressive subtype of acute myeloid leukemia (AML), enhanced anti-leukemic activities of all-trans retinoic acid (atRA) in cell lines and patient samples. However, the drivers of leukemia formation, therapy resistance, and relapse are leukemic stem cells (LSCs), whose properties were hardly reflected in these experimental setups. The present study was designed to address the effects of, and interactions between, EVI1 and retinoids in AML LSCs. We report that Evi1 reduced the maturation of leukemic cells and promoted the abundance, quiescence, and activity of LSCs in an MLL-AF9-driven mouse model of AML. atRA further augmented these effects in an Evi1 dependent manner. EVI1 also strongly enhanced atRA regulated gene transcription in LSC enriched cells. One of their jointly regulated targets, Notch4, was an important mediator of their effects on leukemic stemness. In vitro exposure of leukemic cells to a pan-RAR antagonist caused effects opposite to those of atRA. In vivo antagonist treatment delayed leukemogenesis and reduced LSC abundance, quiescence, and activity in Evi1^high AML. Key results were confirmed in human myeloid cell lines retaining some stem cell characteristics as well as in primary human AML samples. In summary, our study is the first to report the importance of EVI1 for key properties of AML LSCs. Furthermore, it shows that atRA enhances, and a pan-RAR antagonist counteracts, the effects of EVI1 on AML stemness, thus raising the possibility of using RAR antagonists in the therapy of EVI1^high AML.

Expression Pattern and Prognostic Significance of EVI1 Gene in Adult Acute Myeloid Leukemia Patients with Normal Karyotype

According to current criteria, patients with acute myeloid leukemia with normal karyotype (AML-NK) are classified as intermediate risk patients. There is a constant need for additional molecular markers that will help in substratification into more precise prognostic groups. One of the potential new markers is Ecotropic viral integration 1 site (EVI1) transcriptional factor, whose expression is dissregulated in abnormal hematopoietic process. The purpose of this study was to examine EVI1 gene expression in 104 adult AML-NK patients and on 10 healthy bone marrow donors using real-time polymerase chain reaction method, and to evaluate association between EVI1 expression level and other molecular and clinical features, and to examine its potential influence on the prognosis of the disease. Overexpression of EVI1 gene (EVI1 ⁺ status) was present in 17% of patients. Increased EVI1 expression was predominantly found in patients with lower WBC count (P = 0.003) and lower bone marrow blast percentage (P = 0.005). EVI1 ⁺ patients had lower WT1 expression level (P = 0.041), and were negative for FLT3-ITD and NPM1 mutations (P = 0.036 and P = 0.003). Patients with EVI1 ⁺ status had higher complete remission rate (P = 0.047), but EVI1 expression didn't influence overall and disease free survival. EVI1 expression status alone, cannot be used as a new marker for more precise substratification of AML-NK patients. Further investigations conducted on larger number of patients may indicate how EVI1 expression could influence the prognosis and outcome of AML-NK patients, by itself, or in the context of other molecular and clinical parameters.

Direct interaction between the PRDM3 and PRDM16 tumor suppressors and the NuRD chromatin remodeling complex

Aberrant isoform expression of chromatin-associated proteins can induce epigenetic programs related to disease. The MDS1 and EVI1 complex locus (MECOM) encodes PRDM3, a protein with an N-terminal PR-SET domain, as well as a shorter isoform, EVI1, lacking the N-terminus containing the PR-SET domain (ΔPR). Imbalanced expression of MECOM isoforms is observed in multiple malignancies, implicating EVI1 as an oncogene, while PRDM3 has been suggested to function as a tumor suppressor through an unknown mechanism. To elucidate functional characteristics of these N-terminal residues, we compared the protein interactomes of the full-length and ΔPR isoforms of PRDM3 and its closely related paralog, PRDM16. Unlike the ΔPR isoforms, both full-length isoforms exhibited a significantly enriched association with components of the NuRD chromatin remodeling complex, especially RBBP4. Typically, RBBP4 facilitates chromatin association of the NuRD complex by binding to histone H3 tails. We show that RBBP4 binds to the N-terminal amino acid residues of PRDM3 and PRDM16, with a dissociation constant of 3.0 μM, as measured by isothermal titration calorimetry. Furthermore, high-resolution X-ray crystal structures of PRDM3 and PRDM16 N-terminal peptides in complex with RBBP4 revealed binding to RBBP4 within the conserved histone H3-binding groove. These data support a mechanism of isoform-specific interaction of PRDM3 and PRDM16 with the NuRD chromatin remodeling complex.

Myeloid leukemia with high EVI1 expression is sensitive to 5-aza-2'-deoxycytidine by targeting miR-9

PURPOSE

High expression of ecotropic viral integration site 1 (EVI1) has been associated with a poor prognosis in leukemia patients, but the underlying mechanism remains unclear. Aberrant expression of microRNAs plays critical roles in leukemia development. MiR-9 is a putative potential target of EVI1. We have investigated the regulating mechanism of miR-9 by EVI1 in leukemia cells.

METHODS

We first examined the relationship between miR-9 and EVI1 expression levels in nine leukemia cell lines by RT-PCR. Then we forced high expression of EVI1 in UoCM1 and K562 cells to confirm the downregulation of miR-9 by EVI1. Methylation of the miR-9 promoter region was detected by DNA bisulfite sequencing. We treated the EVI1-overexpressing cells with the hypomethylating agent 5-aza-2'-deoxycytidine (5-AZA) to reverse EVI1-induced hypermethylation of miR-9.

RESULTS

EVI1 and miR-9 expression was negative related. Forced expression of EVI1 downregulated miR-9 by inducing hypermethylation of the miR-9 promoter. 5-AZA reversed high EVI1-induced hypermethylation of the miR-9 promoter and restored the expression of miR-9. 5-AZA induced extensive apoptosis and inhibited proliferation through cell cycle arrest in EVI1-overexpressing leukemia cells.

CONCLUSIONS

Our results suggest that EVI1 may be involved in leukemia cell proliferation and apoptosis via the regulation of miR-9 promoter methylation. 5-AZA may represent a promising therapeutic option for EVI1-high leukemia patients.

Molecular and pathologic characterization of AML with double Inv(3)(q21q26.2)

The inv(3)(q21q26.2) altering a single chromosome 3 homolog is an established myeloid malignancy-associated entity. Comparatively, double inv(3) cases involving both homologs are exceedingly rare with 13 reports across AML, CML and MDS. This scarcity was confirmed by finding only 2 new cases out of 34,898 bone marrows collected during a 55 year period at a large medical center (0.0005%). The double inv(3) was detected by karyotype and confirmed by FISH on both homologs in a 41 year old female and a 72 year old male with AML. In the latter case, a 2.26-fold increase in MECOM RNA level was found using an NGS myeloid gene panel. Chromosomal microarray analysis identified segmental copy-neutral loss-of-heterozygosity (CN-LOH) at 3q21 extending to near the q-arm terminus. This is the third report of distal 3q CN-LOH, substantiating that the double inv(3) arises through somatic repair of acquired segmental LOH. Long term clinical and genetic evaluation revealed no discernible morphologic difference between single and double inv(3) cases, conventional chemotherapy resistance and rapid dominance of the double inv(3) clone. The two new cases are consistent with relatively longer survival of double inv(3) patients in the absence of concurrent chromosome 7 loss compared to those with both abnormalities. Importantly, the first known outcome data of bone marrow transplantation in double inv(3) AML is also presented.

A new adult AML case with an extremely complex karyotype, remission and relapse combined with high hyperdiploidy of a normal chromosome set in secondary AML

BACKGROUND

Chromosomal abnormalities are diagnostic and prognostic key factors in acute myeloid leukemia (AML) patients, as they play a central role for risk stratification algorithms. High hyperdiploidy (HH), a rare cytogenetic abnormality seen commonly in elder male AML patients, is normally categorized under AML with complex karyotype (CK). Accordingly, patients with HH generally are associated with low remission rates and a short overall survival.

CASE PRESENTATION

Here we report a case of 21-year-old female, diagnosed with a de novo AML-M1 according to WHO classification and a CK at diagnosis. Cytogenetic, molecular cytogenetic approaches (standard fluorescence in situ hybridization (FISH), array-proven multicolor banding (aMCB)) and high resolution array comparative genomic hybridization (aCGH) analyses revealed a unique complex but still near diploid karyotype involving eleven chromosomes was identified. It included pentasomy 4, three yet unreported chromosomal aberrations t(1;2)(p35;p22), t(1;3)(p36.2;p26.2), and t(10;12)(p15.2;q24.11), and a combination of two cytogenetic events, yet unreported to appear in together, i.e. a reciprocal translocation t(1;3)(p36.2;p26.2) leading to EVI1/PRDM16 gene fusion, and monoallelic loss of tumor suppressor gene TP53. After successful chemotherapeutic treatment the patient experienced a relapse to AML-M1, and she developed secondary AML-M6 with tetraploidy and HH. Unfortunately, the young woman died 8.5 months after initial diagnosis.

CONCLUSIONS

To the best of our knowledge, a comparable adult AML associated with such a CK, coexistence of 3q rearrangements with loss of TP53 at diagnosis, and HH in secondary AML were not previously reported. Thus, the combination of the here seen chromosomal aberrations in adult primary AML seems to indicate for an adverse prognosis.

High EVI1 Expression Predicts Poor Outcomes in Adult Acute Myeloid Leukemia Patients with Intermediate Cytogenetic Risk Receiving Chemotherapy

BACKGROUND Acute myeloid leukemia with intermediate cytogenetic risk (ICR-AML) needs to be stratified. The abnormal gene expression might be prognostic, and its cutoff value for patient grouping is pivotal. MATERIAL AND METHODS Ecotropic viral integration site 1 (EVI1) transcripts were assessed in 191 adult ICR-AML patients at diagnosis who received chemotherapy only. MLL-PTD, WT1 transcript levels, FLT3-ITD, and NPM1 mutations were simultaneously evaluated, and 27 normal bone marrow samples were tested to define normal threshold. RESULTS The normal upper limit of EVI1 transcript levels was 8.0%. Receiver operating characteristic curve analysis showed that 1.0% (a 0.9-log reduction from the normal limit) was the EVI1 optimal cutoff value for significantly differentiating relapse (P=0.049). A total of 23 patients (12%) had EVI1 levels ≥1.0%. EVI1 ≥1.0% had no effect on CR achievement, whereas it was significantly associated with lower 2-year relapse-free survival (RFS), disease-free survival (DFS), and overall survival (OS) rates in the entire cohort (P=0.0003, 0.0017, and 0.0009, respectively), patients with normal karyotypes (P=0.0032, 0.0047, and 0.0007, respectively), and FLT3-ITD (-) patients (all P<0.0001). Multivariate analysis showed that EVI1 ≥1.0% was an independent adverse prognostic factor for RFS, DFS, and OS in the entire cohort. In addition, patients with EVI1 transcript levels between 1.0% and 8.0% had 2-year RFS rates similar to those with EVI1 ≥8.0%, and they both had significantly lower RFS rates than those with EVI1 <1.0% (P=0.0005 and 0.027). CONCLUSIONS High EVI1 expression predicts poor outcome in ICR-AML patients receiving chemotherapy. The optimal cutoff value for patient stratification is different from the normal limit.

Suppression of Transposable Elements in Leukemic Stem Cells

Genomic transposable elements (TEs) comprise nearly half of the human genome. The expression of TEs is considered potentially hazardous, as it can lead to insertional mutagenesis and genomic instability. However, recent studies have revealed that TEs are involved in immune-mediated cell clearance. Hypomethylating agents can increase the expression of TEs in cancer cells, inducing ‘viral mimicry’, causing interferon signalling and cancer cell killing. To investigate the role of TEs in the pathogenesis of acute myeloid leukaemia (AML), we studied TE expression in several cell fractions of AML while tracking its development (pre-leukemic haematopoietic stem cells, leukemic stem cells [LSCs], and leukemic blasts). LSCs, which are resistant to chemotherapy and serve as reservoirs for relapse, showed significant suppression of TEs and interferon pathways. Similarly, high-risk cases of myelodysplastic syndrome (MDS) showed far greater suppression of TEs than low-risk cases. We propose TE suppression as a mechanism for immune escape in AML and MDS. Repression of TEs co-occurred with the upregulation of several genes known to modulate TE expression, such as RNA helicases and autophagy genes. Thus, we have identified potential pathways that can be targeted to activate cancer immunogenicity via TEs in AML and MDS.

Molecular and genetic alterations associated with therapy resistance and relapse of acute myeloid leukemia

BACKGROUND

The majority of individuals with acute myeloid leukemia (AML) respond to initial chemotherapy and achieve a complete remission, yet only a minority experience long-term survival because a large proportion of patients eventually relapse with therapy-resistant disease. Relapse therefore represents a central problem in the treatment of AML. Despite this, and in contrast to the extensive knowledge about the molecular events underlying the process of leukemogenesis, information about the mechanisms leading to therapy resistance and relapse is still limited.

PURPOSE AND CONTENT OF REVIEW

Recently, a number of studies have aimed to fill this gap and provided valuable information about the clonal composition and evolution of leukemic cell populations during the course of disease, and about genetic, epigenetic, and gene expression changes associated with relapse. In this review, these studies are summarized and discussed, and the data reported in them are compiled in order to provide a resource for the identification of molecular aberrations recurrently acquired at, and thus potentially contributing to, disease recurrence and the associated therapy resistance. This survey indeed uncovered genetic aberrations with known associations with therapy resistance that were newly gained at relapse in a subset of patients. Furthermore, the expression of a number of protein coding and microRNA genes was reported to change between diagnosis and relapse in a statistically significant manner.

CONCLUSIONS

Together, these findings foster the expectation that future studies on larger and more homogeneous patient cohorts will uncover pathways that are robustly associated with relapse, thus representing potential targets for rationally designed therapies that may improve the treatment of patients with relapsed AML, or even facilitate the prevention of relapse in the first place.

[EVI1 expression, clinical and cytogenetical characteristics in 447 patients with acute myeloid leukemia]

Objective: To investigate EVI1 expression and its associated clinical and cytogenetic characteristics in 447 acute myeloid leukemia (AML) patients. Methods: EVI1 expressions were measured in 447 AML cases from Jan. 2007 to Apr. 2015 to couple with clinical, cytogenetic and mutations' characteristics to summarize the features of AMLs with high EVI1 expression. Results: 17.9% of AML were high EVI1 expression (EVI1 +), and the remainder low EVI1 expression (EVI1-). No significant differences between the two groups in terms of age, sex, hemoglobin level, white blood cell count and platelet count were observed. More M0, M5 and M6 subtypes were observed in EVI1+ group (P= 0.027, 0.004 and 0.011, respectively). Cytogenetic abnormalities of 11q15, 11q23/MLL, 3q26, -7/7q- and t (9;11) were observed more frequently in EVI1 + group (P<0.001, <0.001, <0.001, <0.001, =0.014, respectively). Normal karyotype, inv (16), t (8;21) were observed more frequent in EVI1- group (P=0.001, 0.009, 0.002, respectively). EVI1 + was more observed in high risk cytogenetics. Mutation of NPM1 was more observed in EVI1- group (P <0.001). Remission rate in EVI1 + group was significantly lower than EVI1- group (P<0.001). Leukemia-free survival was improved in EVI1 + AML patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). Conclusions: High EVI1 expression was more observed in FAB subgroup M5, harbored more cytogenetic abnormalities of 11p15, 11q23/MLL, 3q26 rearrangement, -7/7q- and t (9;11). Remission rate of high EVI1 expression AML was lower, which could be improved by allo-HSCT.

The New Clinicopathologic and Molecular Findings in Myeloid Neoplasms With inv(3)(q21q26)/t(3;3)(q21;q26.2)

Context.—

Inv(3)(q21q26)/t(3;3)(q21;q26.2) is the most common form of genetic abnormality of the so-called 3q21q26 syndrome. Myeloid neoplasms with 3q21q26 aberrancies include acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and blast crisis of myeloproliferative neoplasms. Recent advances on myeloid neoplasms with inv(3)/t(3;3) with regard to clinicopathologic features and novel molecular or genomic findings warrant a comprehensive review on this topic.

Objective.—

To review the clinicopathologic features and molecular as well as genomic alterations in myeloid neoplasms with inv(3)/t(3;3).

Data Sources.—

The data came from published articles in English-language literature.

Conclusions.—

At the clinicopathologic front, recent studies on MDS with inv(3)/t(3;3) have highlighted their overlapping clinicopathologic features with and similar overall survival to that of inv(3)/t(3;3)-harboring AML regardless of the percentage of myeloid blasts. On the molecular front, AML and MDS with inv(3)/t(3;3) exhibit gene mutations, which affect the RAS/receptor tyrosine kinase pathway. Furthermore, functional genomic studies using genomic editing and genome engineering have shown that the reallocation of the GATA2 distal hematopoietic enhancer to the proximity of the promoter of ectopic virus integration site 1 (EVI1) without the formation of a new oncogenic fusion transcript is the molecular mechanism underlying these inv(3)/t(3;3) myeloid neoplasms. Although the AML and MDS with inv(3)/t(3;3) are listed as a separate category of myeloid malignancies in the 2008 World Health Organization classification, the overlapping clinicopathologic features, similar overall survival, and identical patterns at the molecular and genomic levels between AML and MDS patients with inv(3)/t(3;3) may collectively favor a unification of AML and MDS with inv(3)/t(3;3) as AML or myeloid neoplasms with inv(3)/t(3;3) regardless of the blast count.

Predictive value of high EVI1 expression in AML patients undergoing myeloablative allogeneic hematopoietic stem cell transplantation in first CR

The EVI1 gene is a transcriptional regulator of hematopoietic stem cell self renewal and its overexpression is associated with adverse prognosis in de novo AML. Whether the overexpression of EVI1 also predicts poor outcome of AML patients undergoing myeloablative allogeneic hematopoietic stem cell transplantation (allo-HSCT) in first CR (CR1) is still unclear. Thirty-two (21.2%) out of 151 patients were categorized as high EVI1 expression (EVI1+), and 119 (78.8%) patients were categorized as low EVI1 expression (EVI1-). The frequency of EVI1+ was much higher in the adverse-risk group than the intermediate-risk group (53% vs 19%, P=0.005). EVI1+ patients were significantly likely to harbor with translocations involving the MLL gene on 11q23 (8/9). Significantly poor results were observed in the EVI1+ cohort in terms of leukemia-free survival (LFS) (in 24 months 52.6 vs 71.0%, P=0.027), overall survival (OS) (in 24 months 52.8 vs 72.4%, P=0.012), and cumulative incidence of relapse (in 24 months 39.5 vs 22.5%, P=0.013). Multivariable analysis revealed that low EVI1 expression as an independent prognostic factor favoring LFS (hazards ratio=0.47, 95% confidence interval 0.26-0.86, P=0.01) but not OS. Our results indicate high EVI1 expression might predict high risk of relapse in AML patients undergoing myeloablative allo-HSCT in CR1.

The oncogene EVI1 enhances transcriptional and biological responses of human myeloid cells to all-trans retinoic acid

The product of the ecotropic virus integration site 1 (EVI1) gene, whose overexpression is associated with a poor prognosis in myeloid leukemias and some epithelial tumors, regulates gene transcription both through direct DNA binding and through modulation of the activity of other sequence specific transcription factors. Previous results from our laboratory have shown that EVI1 influenced transcription regulation in response to the myeloid differentiation inducing agent, all-trans retinoic acid (ATRA), in a dual manner: it enhanced ATRA induced transcription of the RARβ gene, but repressed the ATRA induction of the EVI1 gene itself. In the present study, we asked whether EVI1 would modulate the ATRA regulation of a larger number of genes, as well as biological responses to this agent, in human myeloid cells. U937 and HL-60 cells ectopically expressing EVI1 through retroviral transduction were subjected to microarray based gene expression analysis, and to assays measuring cellular proliferation, differentiation, and apoptosis. These experiments showed that EVI1 modulated the ATRA response of several dozens of genes, and in fact reinforced it in the vast majority of cases. A particularly strong synergy between EVI1 and ATRA was observed for GDF15, which codes for a member of the TGF-β superfamily of cytokines. In line with the gene expression results, EVI1 enhanced cell cycle arrest, differentiation, and apoptosis in response to ATRA, and knockdown of GDF15 counteracted some of these effects. The potential clinical implications of these findings are discussed.

A murine model of acute myeloid leukemia with Evi1 overexpression and autocrine stimulation by an intracellular form of GM-CSF in DA-3 cells

The poor treatment response of acute myeloid leukemia (AML) overexpressing high-risk oncogenes such as EVI1, demands specific animal models for new treatment evaluations. Evi1 is a common site of activating integrations in murine leukemia virus (MLV)-induced AML and in retroviral and lentiviral gene-modified HCS. Still, a model of overt AML induced by Evi1 has not been generated. Cell lines from MLV-induced AML are growth factor-dependent and non-transplantable. Hence, for the leukemia maintenance in the infected animals, a growth factor source such as chronic immune response has been suggested. We have investigated whether these leukemias are transplantable if provided with growth factors. We show that the Evi1(+)DA-3 cells modified to express an intracellular form of GM-CSF, acquired growth factor independence and transplantability and caused an overt leukemia in syngeneic hosts, without increasing serum GM-CSF levels. We propose this as a general approach for modeling different forms of high-risk human AML using similar cell lines.

EVI1 promotes tumor growth via transcriptional repression of MS4A3

BACKGROUND

The transcription factor Ecotropic Virus Integration site 1 (EVI1) regulates cellular proliferation, differentiation, and apoptosis, and its overexpression contributes to an aggressive course of disease in myeloid leukemias and other malignancies. Notwithstanding, knowledge about the target genes mediating its biological and pathological functions remains limited. We therefore aimed to identify and characterize novel EVI1 target genes in human myeloid cells.

METHODS

U937T_EVI1, a human myeloid cell line expressing EVI1 in a tetracycline regulable manner, was subjected to gene expression profiling. qRT-PCR was used to confirm the regulation of membrane-spanning-4-domains subfamily-A member-3 (MS4A3) by EVI1. Reporter constructs containing various parts of the MS4A3 upstream region were employed in luciferase assays, and binding of EVI1 to the MS4A3 promoter was investigated by chromatin immunoprecipitation. U937 derivative cell lines experimentally expressing EVI1 and/or MS4A3 were generated by retroviral transduction, and tested for their tumorigenicity by subcutaneous injection into severe combined immunodeficient mice.

RESULTS

Gene expression microarray analysis identified 27 unique genes that were up-regulated, and 29 unique genes that were down-regulated, in response to EVI1 induction in the human myeloid cell line U937T. The most strongly repressed gene was MS4A3, and its down-regulation by EVI1 was confirmed by qRT-PCR in additional, independent experimental model systems. MS4A3 mRNA levels were also negatively correlated with those of EVI1 in several published AML data sets. Reporter gene assays and chromatin immunoprecipitation showed that EVI1 regulated MS4A3 via direct binding to a promoter proximal region. Experimental re-expression of MS4A3 in an EVI1 overexpressing cell line counteracted the tumor promoting effect of EVI1 in a murine xenograft model by increasing the rate of apoptosis.

CONCLUSIONS

Our data reveal MS4A3 as a novel direct target of EVI1 in human myeloid cells, and show that its repression plays a role in EVI1 mediated tumor aggressiveness.

Induction of the proapoptotic tumor suppressor gene Cell Adhesion Molecule 1 by chemotherapeutic agents is repressed in therapy resistant acute myeloid leukemia

Even though a large proportion of patients with acute myeloid leukemia (AML) achieve a complete remission upon initial therapy, the majority of them eventually relapse with resistant disease. Overexpression of the gene coding for the transcription factor Ecotropic Virus Integration site 1 (EVI1) is associated with rapid disease recurrence and shortened survival. We therefore sought to identify EVI1 target genes that may play a role in chemotherapy resistance using a previously established in vitro model system for EVI1 positive myeloid malignancies. Gene expression microarray analyses uncovered the Cell Adhesion Molecule 1 (CADM1) gene as a candidate whose deregulation by EVI1 may contribute to drug refractoriness. CADM1 is an apoptosis inducing tumor suppressor gene that is inactivated by methylation in a variety of tumor types. In the present study we provide evidence that it may play a role in chemotherapy induced cell death in AML: CADM1 was induced by drugs used in the treatment of AML in a human myeloid cell line and in primary diagnostic AML samples, and its experimental expression in a cell line model increased the proportion of apoptotic cells. CADM1 up-regulation was abolished by ectopic expression of EVI1, and EVI1 expression correlated with increased CADM1 promoter methylation both in a cell line model and in primary AML cells. Finally, CADM1 induction was repressed in primary samples from AML patients at relapse. In summary, these data suggest that failure to up-regulate CADM1 in response to chemotherapeutic drugs may contribute to therapy resistance in AML.

EVI1 inhibits apoptosis induced by antileukemic drugs via upregulation of CDKN1A/p21/WAF in human myeloid cells

Overexpression of ecotropic viral integration site 1 (EVI1) is associated with aggressive disease in acute myeloid leukemia (AML). Despite of its clinical importance, little is known about the mechanism through which EVI1 confers resistance to antileukemic drugs. Here, we show that a human myeloid cell line constitutively overexpressing EVI1 after infection with a retroviral vector (U937_EVI1) was partially resistant to etoposide and daunorubicin as compared to empty vector infected control cells (U937_vec). Similarly, inducible expression of EVI1 in HL-60 cells decreased their sensitivity to daunorubicin. Gene expression microarray analyses of U937_EVI1 and U937_vec cells cultured in the absence or presence of etoposide showed that 77 and 419 genes were regulated by EVI1 and etoposide, respectively. Notably, mRNA levels of 26 of these genes were altered by both stimuli, indicating that EVI1 regulated genes were strongly enriched among etoposide regulated genes and vice versa. One of the genes that were induced by both EVI1 and etoposide was CDKN1A/p21/WAF, which in addition to its function as a cell cycle regulator plays an important role in conferring chemotherapy resistance in various tumor types. Indeed, overexpression of CDKN1A in U937 cells mimicked the phenotype of EVI1 overexpression, similarly conferring partial resistance to antileukemic drugs.

Cell of origin determines clinically relevant subtypes of MLL-rearranged AML

Mixed lineage leukemia (MLL)-fusion proteins can induce acute myeloid leukemias (AMLs) from either hematopoietic stem cells (HSCs) or granulocyte-macrophage progenitors (GMPs), but it remains unclear whether the cell of origin influences the biology of the resultant leukemia. MLL-AF9-transduced single HSCs or GMPs could be continuously replated, but HSC-derived clones were more likely than GMP-derived clones to initiate AML in mice. Leukemia stem cells derived from either HSCs or GMPs had a similar immunophenotype consistent with a maturing myeloid cell (LGMP). Gene expression analyses demonstrated that LGMP inherited gene expression programs from the cell of origin including high-level Evi-1 expression in HSC-derived LGMP. The gene expression signature of LGMP derived from HSCs was enriched in poor prognosis human MLL-rearranged AML in three independent data sets. Moreover, global 5'-mC levels were elevated in HSC-derived leukemias as compared with GMP-derived leukemias. This mirrored a difference seen in 5'-mC between MLL-rearranged human leukemias that are either EVI1 positive or EVI1 negative. Finally, HSC-derived leukemias were more resistant to chemotherapy than GMP-derived leukemias. These data demonstrate that the cell of origin influences the gene expression profile, the epigenetic state and the drug response in AML, and that these differences can account for clinical heterogeneity within a molecularly defined group of leukemias.

Three novel cytogenetically cryptic EVI1 rearrangements associated with increased EVI1 expression and poor prognosis identified in 27 acute myeloid leukemia cases

In acute myeloid leukemia (AML), increased ecotropic virus integration site 1 protein homolog (EVI1) gene expression is prognostically unfavorable. Subsets of cases show 3q26 rearrangements, such as inv(3)(q21q26)/t(3;3)(q21;q26), frequently accompanied by chromosome 7 abnormalities. We investigated whether cytogenetically cryptic EVI1 rearrangements may cause EVI1 overexpression in myeloid malignancies without 3q26 abnormalities and investigated 983 patients with AML (n = 606) or myelodysplastic syndromes (MDS; n = 377) with normal karyotype (CN-AML/CN-MDS, n = 594) or chromosome 7 abnormalities (n = 389) for EVI1 rearrangements using interphase FISH. We identified cytogenetically cryptic EVI1 rearrangements in 27 patients (19 AML, 8 MDS): inv(3)(p24q26) [n = 10]; t(3;21)(q26;q11) [n = 9]; and der(7)t(3;7)(q26;q21) [n = 8]. Elevated EVI1 expression was detected in nearly all cases with cryptic EVI1 rearrangements: Median %EVI1/ABL1 was 92.8 (range: 29.8-146.1) in inv(3)(p24q26), 104.9 (41.4-176.3) in t(3;21)(q26;q11), and 101.8 (4.4-210.4) in der(7)t(3;7)(q26;q21). This was similar to median %EVI1/ABL1 of 73.9 (range: 7.3-585.6) in an independent cohort of inv(3)(q21q26)/t(3;3)(q21;q26) and 67.1 (2.3-410.7) in other 3q26/EVI1 rearrangements. Healthy controls showed median EVI1 expression of 0.5 (range: 0.0-5.8). Using SNP microarray and sequencing analyses, the breakpoints of der(7)t(3;7)(q26;q21) were assigned to CDK6 and centromeric of EVI1, and of t(3;21)(q26;q11) to be within EVI1 and NRIP1. Median overall survival in patients with cryptic EVI1 rearrangements was short, comparable to patients with inv(3)(q21q26)/t(3;3)(q21;q26) or other EVI1 rearrangements. Cryptic EVI1 rearrangements contribute to explain the clinical heterogeneity of CN-AML and are associated with elevated EVI1 expression and an unfavorable prognosis. Screening for cryptic EVI1 rearrangements by FISH may be particularly appropriate in CN-AML with elevated EVI1 expression or in AML/MDS patients with chromosome 7 abnormalities.

Functional characterization of the promoter region of the human EVI1 gene in acute myeloid leukemia: RUNX1 and ELK1 directly regulate its transcription

The EVI1 gene (3q26) codes for a transcription factor with important roles in normal hematopoiesis and leukemogenesis. High expression of EVI1 is a negative prognostic indicator of survival in acute myeloid leukemia (AML) irrespective of the presence of 3q26 rearrangements. However, the only known mechanisms that lead to EVI1 overexpression are 3q aberrations, and the MLL-ENL oncoprotein, which activates the transcription of EVI1 in hematopoietic stem cells. Our aim was to characterize the functional promoter region of EVI1, and to identify transcription factors involved in the regulation of this gene. Generation of seven truncated constructs and luciferase reporter assays allowed us to determine a 318-bp region as the minimal promoter region of EVI1. Site-directed mutagenesis and chromatin immunoprecipitation (ChIP) assays identified RUNX1 and ELK1 as putative transcription factors of EVI1. Furthermore, knockdown of RUNX1 and ELK1 led to EVI1 downregulation, and their overexpression to upregulation of EVI1. Interestingly, in a series of patient samples with AML at diagnosis, we found a significant positive correlation between EVI1 and RUNX1 at protein level. Moreover, we identified one of the roles of RUNX1 in the activation of EVI1 during megakaryocytic differentiation. EVI1 knockdown significantly inhibited the expression of megakaryocytic markers after treating K562 cells with TPA, as happens when knocking down RUNX1. In conclusion, we define the minimal promoter region of EVI1 and demonstrate that RUNX1 and ELK1, two proteins with essential functions in hematopoiesis, regulate EVI1 in AML. Furthermore, our results show that one of the mechanisms by which RUNX1 regulates the transcription of EVI1 is by acetylation of the histone H3 on its promoter region. This study opens new directions to further understand the mechanisms of EVI1 overexpressing leukemias.

EVI1 is critical for the pathogenesis of a subset of MLL-AF9-rearranged AMLs

The proto-oncogene EVI1 (ecotropic viral integration site-1), located on chromosome band 3q26, is aberrantly expressed in human acute myeloid leukemia (AML) with 3q26 rearrangements. In the current study, we showed, in a large AML cohort carrying 11q23 translocations, that ∼ 43% of all mixed lineage leukemia (MLL)-rearranged leukemias are EVI1(pos). High EVI1 expression occurs in AMLs expressing the MLL-AF6, -AF9, -AF10, -ENL, or -ELL fusion genes. In addition, we present evidence that EVI1(pos) MLL-rearranged AMLs differ molecularly, morphologically, and immunophenotypically from EVI1(neg) MLL-rearranged leukemias. In mouse bone marrow cells transduced with MLL-AF9, we show that MLL-AF9 fusion protein maintains Evi1 expression on transformation of Evi1(pos) HSCs. MLL-AF9 does not activate Evi1 expression in MLL-AF9-transformed granulocyte macrophage progenitors (GMPs) that were initially Evi1(neg). Moreover, shRNA-mediated knockdown of Evi1 in an Evi1(pos) MLL-AF9 mouse model inhibits leukemia growth both in vitro and in vivo, suggesting that Evi1 provides a growth-promoting signal. Using the Evi1(pos) MLL-AF9 mouse leukemia model, we demonstrate increased sensitivity to chemotherapeutic agents on reduction of Evi1 expression. We conclude that EVI1 is a critical player in tumor growth in a subset of MLL-rearranged AMLs.

Epigenetic regulation of miRNA genes in acute leukemia

MicroRNAs (miRNAs) are small non-coding RNA molecules that can negatively regulate gene expression at the post-transcriptional level. miRNA expression patterns are regulated during development and differentiation of the hematopoietic system and have an important role in cell processes such as proliferation, apoptosis, differentiation or even in tumorigenesis of human tumors and in particular of hematological malignancies such as acute leukemias. Various miRNAs and their functions have been intensively studied in acute leukemias but the mechanisms that control their expression are largely unknown for the majority of aberrantly expressed miRNAs. miRNA expression can be regulated by the same genetic mechanism that modulate protein coding genes such as mutation, deletion, amplification, loss of heterozygosity and translocations. In this review we focus on the regulation of miRNAs in acute leukemias mediated by alterations in epigenetic mechanisms such as DNA methylation and histone code, describing the role of these alterations in the pathogenesis, diagnosis and prognosis of acute leukemias and their possible use as new therapeutic targets and biomarkers.

Down-regulation of EVI1 is associated with epigenetic alterations and good prognosis in patients with acute myeloid leukemia

BACKGROUND

The EVI1 gene (3q26) codes for a zinc finger transcription factor with important roles in both mammalian development and leukemogenesis. Over-expression of EVI1 through either 3q26 rearrangements, MLL fusions, or other unknown mechanisms confers a poor prognosis in acute myeloid leukemia.

DESIGN AND METHODS

We analyzed the prevalence and prognostic impact of EVI1 over-expression in a series of 476 patients with acute myeloid leukemia, and investigated the epigenetic modifications of the EVI1 locus which could be involved in the transcriptional regulation of this gene.

RESULTS

Our data provide further evidence that EVI1 over-expression is a poor prognostic marker in acute myeloid leukemia patients less than 65 years old. Moreover, we found that patients with no basal expression of EVI1 had a better prognosis than patients with expression/over-expression (P=0.036). We also showed that cell lines with over-expression of EVI1 had no DNA methylation in the promoter region of the EVI1 locus, and had marks of active histone modifications: H3 and H4 acetylation, and trimethylation of histone H3 lysine 4. Conversely, cell lines with no expression of EVI1 have DNA hypermethylation and are marked by repressive trimethylation of histone H3 lysine 27 at the EVI1 promoter.

CONCLUSIONS

Our results identify EVI1 over-expression as a poor prognostic marker in a large, independent cohort of acute myeloid leukemia patients less than 65 years old, and show that the total absence of EVI1 expression has a prognostic impact on the outcome of such patients. Furthermore, we demonstrated for the first time that an aberrant epigenetic pattern involving DNA methylation, H3 and H4 acetylation, and trimethylation of histone H3 lysine 4 and histone H3 lysine 27 might play a role in the transcriptional regulation of EVI1 in acute myeloid leukemia. This study opens new avenues for a better understanding of the regulation of EVI1 expression at a transcriptional level.

Evi-1 as a critical regulator of leukemic cells

Ecotropic viral integration site-1 (EVI-1) has been recognized as one of the dominant oncogenes associated with murine and human myeloid leukemia. Recent clinical studies demonstrated that high EVI-1 expression was an independent negative prognostic indicator of survival in leukemia patients. In addition, gene-targeting studies in mice reveal that Evi-1 is preferentially expressed in hematopoietic stem cells (HSCs) and plays an essential role in proliferation/maintenance of HSCs. Proteins associated with EVI-1, signaling pathways regulated by EVI-1, and downstream mediators of EVI-1 transcriptional regulation have been described and characterized. In this study, we summarize current knowledge regarding biochemical properties and biological functions of EVI-1, which provides a foundation for the development of novel therapeutic strategies.

HighEVI1Expression Predicts Outcome in Younger Adult Patients With Acute Myeloid Leukemia and Is Associated With Distinct Cytogenetic Abnormalities

Purpose

The purpose of this study was to investigate frequency and prognostic significance of high EVI1 expression in acute myeloid leukemia (AML).

Patients and Methods

A diagnostic assay detecting multiple EVI1 splice variants was developed to determine the relative EVI1 expression by single real-time quantitative polymerase chain reaction in 1,382 newly diagnosed adult patients with AML younger than 60 years. Patients were treated on four Dutch-Belgian HOVON (n = 458) and two German-Austrian AML Study Group protocols (n = 924).

Results

The EVI1 assay was tested in the HOVON cohort and validated in the AMLSG cohort. High EVI1 levels (EVI1+) were found with similar frequencies in both cohorts combined, with a 10.7% incidence (148 of 1,382). EVI1+independently predicted low complete remission (CR) rate (odds ratio, 0.54; P = .002), adverse relapse-free survival (RFS; hazard ratio [HR], 1.32; P = .05), and event-free survival (EFS; HR, 1.46; P < .001). This adverse prognostic impact was more pronounced in the intermediate cytogenetic risk group (EFS; HR, 1.64; P < .001; and RFS; HR, 1.55; P = .02), and was also apparent in cytogenetically normal AML (EFS; HR, 1.67; P = .008). Besides inv(3)/t(3;3), EVI1+was significantly associated with chromosome abnormalities monosomy 7 and t(11q23), conferring prognostic impact within these two cytogenetic subsets. EVI1+was virtually absent in favorable-risk AML and AML with NPM1 mutations. Patients with EVI1+AML (n = 28) who received allogeneic stem cell transplantation in first CR had significantly better 5-year RFS (33% ± 10% v 0%).

Conclusion

EVI1 expression in AML is unequally distributed in cytogenetic subtypes. It predicts poor outcome, particularly among intermediate cytogenetic risk AML. Patients with EVI1+AML may benefit from allogeneic transplantation in first CR. Pretreatment EVI1 screening should be included in risk stratification.

Zinc finger transcription factor ecotropic viral integration site 1 is induced by all-trans retinoic acid (ATRA) and acts as a dual modulator of the ATRA response

Ecotropic viral integration site 1 (EVI1) plays important roles in leukaemia and development, and its expression is temporally and spatially highly restricted during the latter process. Nevertheless, the only physiological agent that to date has been shown to regulate transcription of this gene in mammalian cells is all-trans retinoic acid. Here we describe the identification of a retinoic acid response element that was located in the most distal of several alternative first exons of the human EVI1 gene and was constitutively bound by canonical retinoid receptors in NTERA-2 teratocarcinoma cells. Furthermore, it was the target of negative feedback by EVI1 on the induction of its own promoter by retinoic acid. This process required a previously described transcription repression domain of EVI1. Extending its role as a modulator of the retinoic acid response, EVI1 had the opposite effect on the RARβ retinoic acid response element, whose induction by all-trans retinoic acid it enhanced through a mechanism that involved almost all of its known functional domains. Augmentation of the retinoic acid response by EVI1 was also observed for the endogenous RARβ gene. Thus, we have established EVI1 as a novel type of modulator of the retinoic acid response, which can both enhance and repress induction by this agent in a promoter-specific manner.

Inducible expression of EVI1 in human myeloid cells causes phenotypes consistent with its role in myelodysplastic syndromes

The oncogene EVI1 has been implicated in the etiology of AML and MDS. Although AML cells are characterized by accelerated proliferation and differentiation arrest, MDS cells hyperproliferate when immature but fail to differentiate later and die instead. In agreement with its roles in AML and in immature MDS cells, EVI1 was found to stimulate cell proliferation and inhibit differentiation in several experimental systems. In contrast, the variant protein MDS1/EVI1 caused the opposite effect in some of these assays. In the present study, we expressed EVI1 and MDS1/EVI1 in a tetracycline-regulable manner in the human myeloid cell line U937. Induction of either of these proteins caused cells to accumulate in the G₀/G₁-phase of the cell cycle and moderately increased the rate of spontaneous apoptosis. However, when EVI1- or MDS1/EVI1-expressing cells were induced to differentiate, they massively succumbed to apoptosis, as reflected by the accumulation of phosphatidylserine in the outer leaflet of the plasma membrane and increased rates of DNA fragmentation. In summary, these data show that inducible expression of EVI1 in U937 cells causes phenotypes that may be relevant for its role in MDS and provides a basis for further investigation of its contribution to this fatal disease.

Pathogenetic significance of ecotropic viral integration site-1 in hematological malignancies

The ecotropic viral integration site-1 (Evi-1) gene was first identified as a common locus of retroviral integration in murine leukemia models. In humans, EVI-1 is located on chromosome 3q26, and rearrangements on chromosome 3q26 often activate EVI-1 expression in hematological malignancies. Overexpression of EVI-1 also occurs with high frequency in leukemia patients without 3q26 abnormalities, and importantly, high EVI-1 expression is an independent negative prognostic indicator irrespective of the presence of 3q26 rearrangements. Recent gene targeting studies in mice revealed that Evi-1 is preferentially expressed in hematopoietic stem cells and plays an essential role in proliferation and maintenance of hematopoietic stem cells. In addition, intense attention has been focused on the EVI-1 gene complex as retrovirus integration sites because transcription-activating integrations into the EVI-1 locus confer survival and self-renewing ability to hematopoietic cells. The experimental results using animal models suggest that activation of Evi-1 in hematopoietic cells leads to clonal expansion or dysplastic hematopoiesis, whereas onset of full-blown leukemia requires cooperative genetic events. EVI-1 possesses diverse functions as an oncoprotein, including suppression of transforming growth factor-beta-mediated growth inhibition, upregulation of GATA2, inhibition of the Jun kinase pathway, and stimulation of cell growth via activator protein-1. In this article, we summarize current knowledge regarding the biochemical properties and biological functions of EVI-1 in normal and malignant hematopoiesis, with specific focus on its pathogenetic significance in hematological malignancies.

Clinical implications of molecular genetic aberrations in acute myeloid leukemia

The role of different cytogenetic changes has been extensively evaluated in patients with acute myeloid leukemia (AML), and cytogenetic analysis of AML blasts is essential to form prognostic subgroups in order to stratify for the extent of therapy. Nevertheless, 40-45% of AML patients lack such cytogenetic markers, i.e., cytogenetically normal AML (CN-AML). In the past decade, different molecular aberrations were identified in AML and especially CN-AML can now be discriminated into certain prognostic subgroups. This review considers the latest advances to define the prognostic impact of molecular aberrations in AML and gives insights how such molecular markers can be applied for analysis of minimal residual disease. Furthermore, therapeutic implications as well as the potential role of new methodological techniques in analyzing expression patterns of AML blasts are discussed.