Acute myeloid leukemia with inv(8)(p11q13)

Transcription factor Oct1 protects against hematopoietic stress and promotes acute myeloid leukemia

A better understanding of the development and progression of acute myelogenous leukemia (AML) is necessary to improve patient outcome. Here we define roles for the transcription factor Oct1/Pou2f1 in AML and normal hematopoiesis. Inappropriate reactivation of the CDX2 gene is widely observed in leukemia patients and in leukemia mouse models. We show that Oct1 associates with the CDX2 promoter in both normal and AML primary patient samples, but recruits the histone demethylase Jmjd1a/Kdm3a to remove the repressive H3K9me2 mark only in malignant specimens. The CpG DNA immediately adjacent to the Oct1 binding site within the CDX2 promoter exhibits variable DNA methylation in healthy control blood and bone marrow samples, but complete demethylation in AML samples. In MLL-AF9-driven mouse models, partial loss of Oct1 protects from myeloid leukemia. Complete Oct1 loss completely suppresses leukemia but results in lethality from bone marrow failure. Loss of Oct1 in normal hematopoietic transplants results in superficially normal long-term reconstitution; however, animals become acutely sensitive to 5-fluorouracil, indicating that Oct1 is dispensable for normal hematopoiesis but protects blood progenitor cells against external chemotoxic stress. These findings elucidate a novel and important role for Oct1 in AML.

Cytogenetic and Cytogenomic Microarray Characterization of Chromothripsis in Chromosome 8 Affecting MOZ/NCOA2 (TIF2), FGFR1, RUNX1T1, and RUNX1 in a Pediatric Acute Myeloid Leukemia

Concurrent perturbations in different driver genes have been reported primarily in lymphoma. In acute myeloid leukemia (AML), cases with concurrent alterations in 2 driver genes are infrequently reported. In contrast to pathogenetic pathways in lymphoma with concurrently perturbed genes, the initial gene alteration in AML arrests maturation and the alteration in the second gene promote self-renewal of the blasts. Here, we report a unique case of infantile leukemia in which chromothripsis in chromosome 8 completely altered the G-band structure and resulted in concurrent changes in MOZ/NCOA2, FGFR1, RUNX1T1, and RUNX1. These multiple-hit abnormalities in AML have not been reported previously.

Acute myeloid leukemia with translocation (8;16)(p11;p13) and MYST3-CREBBP rearrangement harbors a distinctive microRNA signature targeting RET proto-oncogene

Acute myeloid leukemia (AML) with t(8;16)(p11;p13) (t(8;16) AML) has unique clinico-biological characteristics, but its microRNA pattern is unknown. We analyzed 670 microRNAs in seven patients with t(8;16) AML and 113 with other AML subtypes. Hierarchical cluster analysis showed that all t(8;16) AML patients grouped in an independent cluster. Supervised analysis revealed a distinctive signature of 94-microRNAs, most of which were downregulated, including miR-21 and cluster miR-17-92. The mRNA expression analysis of two known transcription factors of these microRNAs (STAT3 and c-Myc, respectively) showed significant downregulation of STAT3 (P=0.04). A bioinformatic analysis showed that 29 of the downregulated microRNAs might be regulated by methylation; we treated a t(8;16) AML sample with 5-aza-2'-deoxycytidine (5-AZA-dC) and trichostatin A and found that 27 microRNAs were re-expressed after treatment. However, there was no difference in methylation status between t(8;16) and other AML subtypes, either overall or in the microRNA promoter. Cross-correlation of mRNA and microRNA expression identified RET as a potential target of several microRNAs. A Renilla-luciferase assay and flow cytometry after transfection with pre-microRNAs confirmed that RET is regulated by miR-218, miR-128, miR-27b, miR-15a and miR-195. In conclusion, t(8;16) AML harbors a specific microRNA signature that is partially epigenetically regulated and targets RET proto-oncogene.

AML with translocation t(8;16)(p11;p13) demonstrates unique cytomorphological, cytogenetic, molecular and prognostic features

Balanced chromosomal rearrangements define distinct entities in acute myeloid leukemia (AML). Here, we present 13 AML cases with t(8;16)(p11;p13) with observed low incidence (13/6124 patients), but more frequent presentation in therapy-related AML than in de novo AML (7/438 versus 6/5686, P=0.00001). Prognosis was poor with median overall survival of 4.7 months. Cytomorphology was characterized by parallel positive myeloperoxidase and non-specific esterase staining, therefore, French-American-British (FAB)-classification was impossible and origin of the AML with t(8;16) from an early stem cell with myeloid and monoblastic potential is hypothesized. Erythrophagocytosis was observed in 7/13 cases. Using gene expression profiling on 407 cases, patients with t(8;16) were compared to AML FAB subtypes with normal karyotype. Principal component analyses demonstrated that AML with t(8;16) were distinct from FAB subtypes M1, M4, M5a/b. When further compared to AML showing balanced rearrangements, that is, current WHO categories t(15;17), t(8;21), inv(16) and t(11q23)/MLL, AML with t(8;16) cases were clustered close to t(11q23)/MLL sharing commonly expressed genes. Subsequently, a pairwise comparison discriminated AML with t(8;16) from AML with t(11q23)/MLL, thus defining a highly unique signature for AML with t(8;16). In conclusion, AML with t(8;16) demonstrates unique cytomorphological, cytogenetic, molecular and prognostic features and is a specific subtype of AML.

Acute myeloid leukaemia with 8p11 (MYST3) rearrangement: an integrated cytologic, cytogenetic and molecular study by the groupe francophone de cytogénétique hématologique

Thirty cases of acute myeloid leukaemia (AML) with MYST histone acetyltransferase 3 (MYST3) rearrangement were collected in a retrospective study from 14 centres in France and Belgium. The mean age at diagnosis was 59.4 years and 67% of the patients were females. Most cases (77%) were secondary to solid cancer (57%), haematological malignancy (35%) or both (8%), and appeared 25 months after the primary disease. Clinically, cutaneous localization and disseminated intravascular coagulation were present in 30 and 40% of the cases, respectively. AMLs were myelomonocytic (7%) or monocytic (93%), with erythrophagocytosis (75%) and cytoplasmic vacuoles (75%). Immunophenotype showed no particularity compared with monocytic leukaemia without MYST3 abnormality. Twenty-eight cases carried t(8;16)(p11;p13) with MYST3-CREBBP fusion, one case carried a variant t(8;22)(p11;q13) and one case carried a t(8;19)(p11;q13). Type I (MYST3 exon 16-CREBBP exon 3) was the most frequent MYST3-CREBBP fusion transcript (65%). MYST3 rearrangement was associated with a poor prognosis, as 50% of patients deceased during the first 10 months. All those particular clinical, cytologic, cytogenetic, molecular and prognostic characteristics of AML with MYST3 rearrangement may have allowed an individualization into the World Health Organization classification.

A role for the transcription intermediary factor 2 in zebrafish myelopoiesis

OBJECTIVE

TIF2 is fused with MOZ in the inv(8)(p11q13) acute myeloid leukemia. TIF2, member of the p160 family, is a histone acetyl transferase (HAT). Deletion of p160 genes were performed in mice. Some observations suggest that p160 family members may perform overlapping functions in mice. Therefore, we decided to choose the zebrafish model to study TIF2. The aim of this study was to characterize the role of this HAT during embryonic development.

MATERIAL AND METHODS

We use antisense, morpholino-modified oligomers to transiently knockdown tif2 gene, thus determining whether TIF2 plays a role in zebrafish early development.

RESULTS

We show that tif2 is involved in embryogenesis and in primitive hematopoiesis. tif2-knockdown zebrafish embryos are smaller than controls, they demonstrate shorter tails, they display notochord deformation and they exhibit U-shaped tail somites. A synthetic RNA encoding human TIF2 rescues the tif2-knockdown phenotype. Analysis of fli1 expression by whole-mount in situ hybridization indicates normal angioblast specification, but altered localization of intersomitic vessels. The posterior intermediate cell mass, in which a part of primitive hematopoiesis occurs, is altered in tif2 morphants and whole-mount in situ hybridization analyses of l-plastin and mpx expression suggest a specific inhibition of granulocytic and macrophagic differentiation at late stages.

CONCLUSION

These data indicate an important role for TIF2 in zebrafish primitive myelopoiesis.

Childhood acute myeloid leukemia with hemophagocytosis by the blasts and inv(8)(p11q13) with MOZ-TIF2 fusion transcripts

We describe a unique case of de novo childhood acute myeloid leukemia in which the blasts showed evidence of hemophagocytosis and harbored inv(8) (p11q13) chromosomal abnormality. Reverse-transcription polymerase chain reaction showed the presence of 2 MOZ-TIF2 fusion transcripts. To our knowledge, this is the eighth overall and the fourth childhood case of acute myeloid leukemia with inv(8) (p11q13) with MOZ-TIF2 fusion.

Translocation (8;18;16)(p11;q21;p13). A new variant of t(8;16)(p11;p13) in acute monoblastic leukemia: case report and review of the literature

A complex three-way t(8;18;16)(p11;q21;p13) was detected in a 15-month-old patient with acute myeloid leukemia (AML). The patient had typical clinical manifestation and bone marrow features of AML subtype M5b associated with t(8;16)(p11;p13). Therefore, we believe that the t(8;18;16) is a new variant of t(8;16) related to AML M4/M5. We also review other t(8;16)(p11;p13) variants reported in the literature.

Chromatin modifier enzymes, the histone code and cancer

In all organisms, cell proliferation is orchestrated by coordinated patterns of gene expression. Transcription results from the activity of the RNA polymerase machinery and depends on the ability of transcription activators and repressors to access chromatin at specific promoters. During the last decades, increasing evidence supports aberrant transcription regulation as contributing to the development of human cancers. In fact, transcription regulatory proteins are often identified in oncogenic chromosomal rearrangements and are overexpressed in a variety of malignancies. Most transcription regulators are large proteins, containing multiple structural and functional domains some with enzymatic activity. These activities modify the structure of the chromatin, occluding certain DNA regions and exposing others for interaction with the transcription machinery. Thus, chromatin modifiers represent an additional level of transcription regulation. In this review we focus on several families of transcription activators and repressors that catalyse histone post-translational modifications (acetylation, methylation, phosphorylation, ubiquitination and SUMOylation); and how these enzymatic activities might alter the correct cell proliferation program, leading to cancer.

MOZ-TIF2 inhibits transcription by nuclear receptors and p53 by impairment of CBP function

Chromosomal rearrangements associated with acute myeloid leukemia (AML) include fusions of the genes encoding the acetyltransferase MOZ or MORF with genes encoding the nuclear receptor coactivator TIF2, p300, or CBP. Here we show that MOZ-TIF2 acts as a dominant inhibitor of the transcriptional activities of CBP-dependent activators such as nuclear receptors and p53. The dominant negative property of MOZ-TIF2 requires the CBP-binding domain (activation domain 1 [AD1]), and coimmunoprecipitation and fluorescent resonance energy transfer experiments show that MOZ-TIF2 interacts with CBP directly in vivo. The CBP-binding domain is also required for the ability of MOZ-TIF2 to extend the proliferative potential of murine bone marrow lineage-negative cells in vitro. We show that MOZ-TIF2 displays an aberrant nuclear distribution and that cells expressing this protein have reduced levels of cellular CBP, leading to depletion of CBP from PML bodies. In summary, our results indicate that disruption of the normal function of CBP and CBP-dependent activators is an important feature of MOZ-TIF2 action in AML.

Pericentric chromosome 8 inversion associated with the 5?RUNX1/3?CBFA2T1 gene in acute myeloid leukemia cases

In the present paper we report pericentric chromosome 8 inversions in two (2.4%) of 82 acute myeloid leukemia (AML) cases characterized by the 5'RUNX1/3'CBFA2T1 fusion gene. Molecular cytogenetic characterization was achieved using appropriate bacterial artificial chromosome (BAC) and P1 artificial chromosome (PAC) probes in fluorescence in situ hybridization (FISH) experiments. In these two cases the fusion gene was detected on the der(8) short arm, resulting from a pericentric chromosome 8 inversion followed by a t(8;21) rearrangement. These results suggest that heterogeneous mechanisms can lead to the generation of the 5'RUNX1/3'CBFA2T1chimeric gene.

Loss of heterozygosity and internal tandem duplication mutations of the CBP gene are frequent events in human esophageal squamous cell carcinoma

PURPOSE

Cyclic AMP response element binding protein binding protein (CBP), a nuclear transcriptional coactivator protein, is an important component of the cAMP signal transduction pathway. In this study, we systematically analyzed the pattern and frequency of CBP gene alterations in esophageal squamous cell carcinoma (ESCC) samples from Linzhou (Linxian), China.

EXPERIMENTAL DESIGN

Using microsatellite markers D16S475, D16S2622, and D16S523 within the chromosome 16p13.3 locus flanking the CBP gene, we observed loss of heterozygosity (LOH), microsatellite instability (MSI), or homozygous deletion in 16 of 26 ESCC samples. Additional ESCC samples were analyzed using different sets of microsatellite markers (CS1-CS5) within the introns or in close proximity to the 3' end of the CBP gene.

RESULTS

The data showed that CBP gene LOH or MSI occurred in 9 of 19 ESCC samples. A detailed genetic alteration map of the CBP gene showed that an LOH or MSI hot spot occurred within intron 2 of the CBP gene. Furthermore, ESCC samples were investigated for CBP gene mutation by conformation sensitive gel electrophoresis and DNA sequencing. These results revealed that most of the shifted fragments contained internal tandem duplication (ITD), frequently in the regions encoding the histone acetyltransferase domain and COOH-terminal transactivating domain one of the CBP gene. The presence of ITD within the CBP gene was additionally confirmed by Southern blot analysis and sequencing.

CONCLUSIONS

These studies show that LOH and ITD of the CBP gene are frequent genetic events in human ESCC. These alterations may have functional importance in the development of human ESCC.

t(10;16)(q22;p13) and MORF-CREBBP fusion is a recurrent event in acute myeloid leukemia

Recently, it was shown that t(10;16)(q22;p13) fuses the MORF and CREBBP genes in a case of childhood acute myeloid leukemia (AML) M5a, with a complex karyotype containing other rearrangements. Here, we report a new case with the MORF-CREBBP fusion in an 84-year-old patient diagnosed with AML M5b, in which the t(10;16)(q22;p13) was the only cytogenetic aberration. This supports that this is a recurrent pathogenic translocation in AML.

Genomic characterization of MOZ/CBP and CBP/MOZ chimeras in acute myeloid leukemia suggests the involvement of a damage-repair mechanism in the origin of the t(8;16)(p11;p13)

The t(8;16)(p11;p13), which is strongly associated with acute myeloid leukemia (AML) displaying monocytic differentiation, erythrophagocytosis by the leukemic cells, and a poor response to chemotherapy, fuses the MOZ gene (8p11) with the CBP gene (16p13). Although genomic rearrangements of MOZ and CBP have been detected using fluorescence in situ hybridization and Southern blot analyses, characterization of the breakpoints at the sequence level has never been performed. We have sequenced the breakpoints in four t(8;16)-positive AML cases with the aim to identify molecular genetic mechanisms underlying the origin of this translocation. In addition, an exon/intron map of the MOZ gene was constructed, which was found to be composed of 17 exons. Long-range-PCR with CBP forward primers in exon 2 and MOZ reverse primers in exon 17 as well as with a MOZ forward primer in exon 16 and a CBP reverse primer in intron 2 successfully amplified CBP/MOZ and MOZ/CBP hybrid genomic DNA fragments in all four AMLs. The breaks clustered in both CBP intron 2 and MOZ intron 16, and were close to repetitive elements, and in one case an Alu-Alu junction for the CBP/MOZ hybrid was identified. Additional genomic events (i.e., deletions, duplications, and insertions) in the breakpoint regions in both the MOZ and CBP genes were found in all four cases. Thus, the t(8;16) does not originate through a simple end-to-end fusion. The findings of multiple breaks and rearrangements rather suggest the involvement of a damage-repair mechanism in the origin of this translocation.