EVI1 controls proliferation in acute myeloid leukaemia through modulation of miR-1-2.

BACKGROUND: The EVI1(ecotropic virus integration site 1) gene codes for a zinc-finger transcription factor, whose transcriptional activation leads to a particularly aggressive form of acute myeloid leukaemia (AML). Although, EVI1 interactions with key proteins in hematopoiesis have been previously described, the precise role of this transcription factor in promoting leukaemic transformation is not completely understood. Recent works have identified specific microRNA (miRNA) signatures in different AML subgroups. However, there is no analysis of miRNAs profiles associated with EVI1 overexpression in humans. METHODS: We performed QT-RT-PCR to assess the expression of 250 miRNAs in cell lines with or without EVI1 overexpression and in patient samples. We used ChIP assays to evaluated the possible binding of EVI1 binding to the putative miRNA promoter. Proliferation of the different cell lines transfected with the anti- or pre-miRs was quantified by MTT. RESULTS: Our data showed that EVI1 expression was significantly correlated with the expression of miR-1-2 and miR-133-a-1 in established cell lines and in patient samples. ChIP assays confirmed that EVI1 binds directly to the promoter of these two miRNAs. However, only miR-1-2 was involved in abnormal proliferation in EVI1 expressing cell lines. CONCLUSIONS: Our data showed that EVI1 controls proliferation in AML through modulation of miR-1-2. This study contributes to further understand the transcriptional networks involving transcription factors and miRNAs in AML.

DNA profiling analysis of 100 consecutive de novo acute myeloid leukemia cases reveals patterns of genomic instability that affect all cytogenetic risk groups.

We have carried out a high-resolution whole genome DNA profiling analysis on 100 bone marrow samples from a consecutive series of de novo acute myeloid leukemia (AML) cases. After discarding copy number changes that are known to be genetic polymorphisms, we found that genomic aberrations (GA) in the form of gains or losses of genetic material were present in 74% of the samples, with a median of 2 GA per case (range 0-35). In addition to the cytogenetically detected aberration, GA were present in cases from all cytogenetic prognostic groups: 79% in the favorable group, 60% in the intermediate group (including 59% of cases with normal karyotype) and 83% in the adverse group. Five aberrant deleted regions were recurrently associated with cases with a highly aberrant genome (e.g., a 1.5 Mb deletion at 17q11.2 and a 750 kb deletion at 5q31.1). Different degrees of genomic instability showed a statistically significant impact on survival curves, even within the normal karyotype cases. This association was independent of other clinical and genetic parameters. Our study provides, for the first time, a detailed picture of the nature and frequency of DNA copy number aberrations in de novo AML.

Disruption and aberrant expression of HMGA2 as a consequence of diverse chromosomal translocations in myeloid malignancies.

Chromosomal translocations that target HMGA2 at chromosome band 12q14 are seen in a variety of malignancies, notably lipoma, pleomorphic salivary adenoma and uterine leiomyoma. Although some HMGA2 fusion genes have been reported, several lines of evidence suggest that the critical pathogenic event is the expression of truncated HMGA2 isoforms. We report here the involvement of HMGA2 in six patients with myeloid neoplasia, dysplastic features and translocations or an inversion involving chromosome bands 12q13-15 and either 7p12, 8q22, 11q23, 12p11, 14q31 or 20q11. Breaks within or very close to HMGA2 were found in all six cases by molecular cytogenetic analysis, leading to overexpression of this gene as assessed by RT-PCR. Truncated transcripts consisting of HMGA2 exons 1-2 or exons 1-3 spliced to intron-derived sequences were identified in two patients, but were not seen in controls. These findings suggest that abnormalities of HMGA2 play an important and previously unsuspected role in myelodysplasia.

Abnormalities on 1q and 7q are associated with poor outcome in sporadic Burkitt's lymphoma. A cytogenetic and comparative genomic hybridization study.

Comparative genomic hybridization (CGH) studies have demonstrated a high incidence of chromosomal imbalances in non-Hodgkin's lymphoma. However, the information on the genomic imbalances in Burkitt's Lymphoma (BL) is scanty. Conventional cytogenetics was performed in 34 cases, and long-distance PCR for t(8;14) was performed in 18 cases. A total of 170 changes were present with a median of four changes per case (range 1-22). Gains of chromosomal material (143) were more frequent than amplifications (5) or losses (22). The most frequent aberrations were gains on chromosomes 12q (26%), Xq (22%), 22q (20%), 20q (17%) and 9q (15%). Losses predominantly involved chromosomes 13q (17%) and 4q (9%). High-level amplifications were present in the regions 1q23-31 (three cases), 6p12-p25 and 8p22-p23. Upon comparing BL vs Burkitt's cell leukemia (BCL), the latter had more changes (mean 4.3 +/- 2.2) than BL (mean 2.7 +/- 3.2). In addition, BCL cases showed more frequently gains on 8q, 9q, 14q, 20q, and 20q, 9q, 8q and 14q, as well as losses on 13q and 4q. Concerning outcome, the presence of abnormalities on 1q (ascertained either by cytogenetics or by CGH), and imbalances on 7q (P=0.01) were associated with a short survival.

Lipid Nanosystems Enhance the Bioavailability and the Therapeutic Efficacy of FTY720 in Acute Myeloid Leukemia.

Protein phosphatase 2A (PP2A) is a serin-threonin phosphatase that regulates many proteins critical for malignant cell behavior; therefore, PP2A is considered to be a human tumor suppressor. In this study, we assessed the pharmacokinetic profile and the antileukemic effects of the PP2A activator FTY720, free or encapsulated in lipid nanoparticles, in in vitro and in vivo models of acute myeloid leukemia. FTY720 lipid nanoparticles presented diameters around 210 nm, with an encapsulation efficiency up to 75% and significantly increased FTY720 oral bioavailability. In addition, FTY720 restores PP2A phosphatase activity and decreases phosphorylation of PP2A and its targets Akt, ERK1/2 and STAT5, all implicated in the pathogenesis of acute myeloid leukemia. Moreover, FTY720 exerts an additive anti-leukemic effect in combination with drugs used in standard induction therapy. Importantly, FTY720 lipid nanoparticles were more efficient at inducing cell growth arrest and apoptosis than FTY720 solution. Finally, oral administration of FTY720 lipid nanoparticles to mice every three days was as effective in reducing acute myeloid leukemia xenograft tumor growth as daily oral administration of FTY720. These results provide the first evidence for the potential use of FTY720 lipid nanoparticles as an oral therapeutic agent in acute myeloid leukemia.

A recurrent translocation, t(3;11)(q21;q13), found in two distinct cases of acute myeloid leukemia.

We report two cases of acute myeloid leukemia (M1 and M5B subtypes) with a similar translocation, t(3;11)(q21;q13). We discuss the involvement of these breakpoints in acute leukemia and their putative clinical implications.

A variant t(14;17) in acute promyelocytic leukemia. Positive response to retinoic acid treatment.

We present a case of acute promyelocytic leukemia (APL) carrying an atypical translocation involving chromosomes 14 and 17. This translocation could be considered a variant of the APL-specific t(15;17). Positive response to retinoic acid treatment suggests molecular rearrangement of retinoic acid receptor alpha.

Cytogenetic data in 41 patients with multiple myeloma. Karyotype and other clinical parameters.

Cytogenetic data of 41 patients diagnosed with multiple myeloma (MM) are reported. In all samples, cytogenetic studies were made of short-term and B-cell-stimulated culture: 20 cases (48.8%) showed chromosome abnormalities; 14 karyotypes were hypo- or pseudodiploid, and six were hyperdiploid. The most frequent numerical changes affected chromosomes 7, 11, 5 (gains), 14, 20, and Y (losses). Chromosome structural rearrangements of 22q were noted in six patients. Other and recurrent cytogenetic abnormalities were changes involving chromosomes 1, 14, and 17. A significant relation was observed between presence of chromosome abnormalities and the following hematologic parameters: clinical stage III (p = 0.0212), bone marrow (BM) plasma cell infiltration greater than 30% (p = 0.0379), presence of bone lesions (p = 0.0051), and beta 2-microglobulin levels greater than 4,000 md/dl (p = 0.0194).

Comparative genomic hybridization and amplotyping by arbitrarily primed PCR in stage A B-CLL.

Cytogenetic analysis is useful in the diagnosis and to assess prognosis of B-cell chronic lymphocytic leukemia (B-CLL). However, successful cytogenetics by standard techniques has been hindered by the low in vitro mitotic activity of the malignant B-cell population. Fluorescence in situ hybridization (FISH) has become a useful tool, but it does not provide an overall view of the aberrations. To overcome this hurdle, two DNA-based techniques have been tested in the present study: comparative genomic hybridization (CGH) and amplotyping by arbitrarily primed PCR (AP-PCR). Comparative genomic hybridization resolution depends upon the 400-bands of the human standard karyotype. AP-PCR allows detection of allelic losses and gains in tumor cells by PCR fingerprinting, thus its resolution is at the molecular level. Both techniques were performed in 23 patients with stage A B-CLL at diagnosis. The results were compared with FISH. The sensitivity of AP-PCR was greater than CGH (62% vs. 43%). The use of CGH combined with AP-PCR allowed to detect genetic abnormalities in 79% (15/19) of patients in whom G-banding was not informative, providing a global view of the aberrations in a sole experiment. This study shows that combining these two methods with FISH, makes possible a more precise genetic characterization of patients with B-CLL.

Insertion (22;9)(q11;q34q21) in a patient with chronic myeloid leukemia characterized by fluorescence in situ hybridization.

An unusual cytogenetic rearrangement, described as ins(22;9)(q11;q34q21), was detected in a 49-year-old male patient diagnosed with chronic myeloid leukemia (CML). Reverse transcriptase polymerase chain reaction (RT-PCR) revealed a b3a2 fusion transcript. In order to confirm the cytogenetic findings and fully characterize the inverted insertion, we performed fluorescence in situ hybridization (FISH) assays using locus-specific and whole chromosome painting probes. Our FISH analysis showed the presence of the BCR/ABL fusion gene, verified the insertion and determined that the breakpoint on chromosome 22 where the insertion took place was located proximal to the BCR gene and distal to the TUPLE1 gene on 22q11.

[New cytogenetic prognostic markers in breast cancer]. / Identificación de nuevos marcadores citogenéticos con valor pronóstico en cáncer de mama.

BACKGROUND: The aim of this study was to identify chromosomal imbalances in a series of invasive ductal carcinomas. In order to characterize the prognostic value of the chromosomal aberrations, we determined the association between genetic changes, overall survival, recurrences and some well-known prognostic and diagnostic parameters. MATERIAL AND METHODS: We included in this study 70 ductal invasive carcinomas diagnosed at the Hospital of Navarra during 1991-1994. We used the Comparative Genomic Hybridization Technique (CGH) for the molecular cytogenetic analysis of formalin-fixed, paraffin embedded specimens. RESULTS: We obtained successful results in 57 out of 70 cases (81.4%). The most frequent recurring findings were DNA gains on 8q, 17q, 1q, 20q, 11q and 6q and losses on 16q, Xp, Xq, 13q, 11q and 8p. In the survival study, gains on 1q and 11q13 were more frequent in patients with recurrence (41.3% vs. 18.5% and 50% vs. 23.7%). Loss of 16q appears as a prognostic factor of good outcome because of its association with good pathological prognostic features: 100% of tumors with this aberration showed overexpression of Bcl-2, and 75% of them were node negative. Besides, 46.7% of the positive cases for the expression of estrogen receptors also showed this imbalance. CONCLUSIONS: The CGH is a useful technique for the study of paraffin embedded tumors. Our results confirm that the cytogenetic aberrations of tumors could be considered as prognostic factors contributing to a better knowledge of tumor outcome.

Importance of genetics in acute myeloid leukemia.

Acute myeloid leukemia (AML) comprises a biologically and clinically heterogeneous group of aggressive disorders that occur as a consequence of a wide variety of genetic and epigenetic abnormalities in hematopoietic progenitors. Despite significant advances in the understanding of the biology of AML, most patients will die from relapsed disease. Whole-genome studies have identified novel recurrent gene mutations with prognostic impact in AML; furthermore, it is likely that in the near future genome-wide sequencing will become a routine for newly diagnosed patients with AML. Therefore, future clinical trials should aim to identify genetically defined high-risk patients, and further research is necessary to identify effective agents and develop new individualized therapeutic strategies for the treatment of this deadly disease.

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.

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.

PP2A impaired activity is a common event in acute myeloid leukemia and its activation by forskolin has a potent anti-leukemic effect.

Protein phosphatase 2A (PP2A) is a human tumor suppressor that inhibits cellular transformation by regulating the activity of several signaling proteins critical for malignant cell behavior. PP2A has been described as a potential therapeutic target in chronic myeloid leukemia, Philadelphia chromosome-positive acute lymphoblastic leukemia and B-cell chronic lymphocytic leukemia. Here, we show that PP2A inactivation is a recurrent event in acute myeloid leukemia (AML), and that restoration of PP2A phosphatase activity by treatment with forskolin in AML cells blocks proliferation, induces caspase-dependent apoptosis and affects AKT and ERK1/2 activity. Moreover, treatment with forskolin had an additive effect with Idarubicin and Ara-c, drugs used in standard induction therapy in AML patients. Analysis at protein level of the PP2A activation status in a series of patients with AML at diagnosis showed PP2A hyperphosphorylation in 78% of cases (29/37). In addition, we found that either deregulated expression of the endogenous PP2A inhibitors SET or CIP2A, overexpression of SETBP1, or downregulation of some PP2A subunits, might be contributing to PP2A inhibition in AML. In conclusion, our results show that PP2A inhibition is a common event in AML cells and that PP2A activators, such as forskolin or FTY720, could represent potential novel therapeutic targets in AML.