NUP98 is fused to HOXA9 in a variant complex t(7;11;13;17) in a patient with AML-M2

Acute Myelogenous Leukemia with the t(7;7)(p15;p22) Translocation, a Novel Simple Variant of t(7;11)(p15;p15) Translocation: First Description

The t(7;11)(p15;p15) translocation is a recurrent genetic abnormality associated with acute myelogenous leukemia (AML). The translocation results in a fusion between the nucleoporin 98 and homeobox genes. We describe a case of AML with t(7; 7)(p15;p22) translocation, which is a novel simple variant of the t(7;11)(p15;p15) translocation. A 66-year-old woman presented with subcutaneous hemorrhage in both forearms. Laboratory test revealed hyperleukocytosis (white blood cell count: 97,800 cells/µL (blasts, 51.0%)), anemia (hemoglobin level: 7.6 g/dL), thrombocytopenia (platelet count: 6.5 × 10⁴/μL), and hyperfibrinolysis (elevated d-dimer level: 12.4 µg/mL; fibrin/fibrinogen degradation products: 26.9 µg/mL). The patient was diagnosed with AML; the blast morphology was unclassifiable according to the French-American-British classification. Flow cytometry CD45 gating revealed that the blasts expressed CD34, CD13, CD33, and CD117. G-banding of tumor cells revealed the t(7;7)(p15;p22) translocation [20/20]. The patient underwent chemotherapy. At 48 days of admission, the patient died of multiple organ failure. The t(7;7)(p15;p22) translocation involved chromosome 7p15, indicating its association with the homeobox genes. To the best of our knowledge, this is the first report of a patient with AML with the t(7;7)(p15;p22) translocation, which is a simple novel variant of the t(7;11)(p15;p15) translocation.

NUP98-HOXA9 bearing therapy-related myeloid neoplasm involves myeloid-committed cell and induces HOXA5, EVI1, FLT3, and MEIS1 expression

INTRODUCTION

Chromosomal rearrangements involving NUP98 gene have been associated with human leukemias such as de novo AML, therapy-related AML (t-AML), myelodysplastic syndrome (MDS), and chronic myeloid leukemia (CML). Genetic fusion NUP98-HOXA9, caused by t(7;11)(p15;p15), is a recurrent cytogenetic alteration in de novo acute myeloid leukemia (AML) usually found in young Asian patients and its description in therapy-related myeloid neoplasms (t-MN) is rare. Only one Asian case with molecular demonstration of the NUP98-HOXA9 fusion has been reported in therapy-related leukemia. NUP98-HOXA9 leukemogenic mechanism is derived from the transcription factor activity of the chimeric protein, which enhances the expression of genes related to cellular differentiation arrest and proliferation.

PATIENTS AND METHODS

We studied a Caucasian woman with a therapy-related acute myeloid leukemia after Ewing's sarcoma. Molecular demonstration of the genetic fusion NUP98-HOXA9 was performed by RT-PCR, and gene expression was analyzed by real-time PCR, including four AML patients with MLL rearrangements for comparative analysis. Cytologic and flow cytometric analysis was also carried out.

RESULTS

After cytologic and flow cytometric analysis diagnostics was therapy-related myeloid neoplasm (t-MN). The major component of blasts in the acute leukemia was with neutrophilic differentiation, but 13% erythroid lineage blasts were also found. Cytogenetic and FISH analysis revealed t(7;11)(p15;p15) and NUP98-HOXA9 fusion gene was demonstrated. Gene expression analysis showed upregulation of EVI1 and MEIS1 in the index patient, both of them previously related to a worst outcome.

CONCLUSION

In this work, we include a detailed molecular, clinical, cytological, and cytometric study of the second t-AML bearing NUP98-HOXA9 genetic fusion.

Up-regulation of homeodomain genes, DLX1 and DLX2, by FLT3 signaling

BACKGROUND

Activating mutations in fms-like tyrosine kinase-3 (FLT3) are frequent in acute myeloid leukemia and represent both a poor prognostic feature and a therapeutic target. We have identified a previously unrecognized downstream effect of FLT3 activation, namely up-regulation of the homeodomain genes, DLX1 and DLX2.

DESIGN AND METHODS

MV4;11 cells with FLT3-internal tandem duplication mutation, RS4;11 cells with wild-type FLT3 and blasts from patients with acute myeloid leukemia were used to pursue the relation between FLT3, DLX1/2 and transforming growth factor-β (TGFβ). Real-time quantitative reverse transcriptase polymerase chain reaction, western blot and reverse-phase protein array were performed to detect changes in gene and protein expression. RNA interference and MTS assays were used to study the interaction of PKC412, FLT3 inhibitor and TGFβ1.

RESULTS

A direct relationship between FLT3 activity and DLX1/2 expression was revealed by both inhibition and up-regulation of FLT3 signaling in MV4;11 and RS4;11 cell lines, respectively, in isolated blast cells from patients with acute myeloid leukemia, and in reverse-phase protein array assays of samples from patients with acute myeloid leukemia. Mechanistically, the link between FLT3 and DLX1 expression appears to involve MAPK signaling through the ERK and JNK pathways. To determine whether elevated DLX1 had a functional consequence, we explored the reported inhibition by DLX1 on TGFβ/Smad signaling. Indeed, TGFβ responses were blunted by FLT3 activation in a DLX1-dependent manner and FLT3 inhibition resulted in a time-dependent increase in nuclear phospho-Smad2.

CONCLUSIONS

These findings suggest that alterations in DLX1/2 contribute to the biological consequences of FLT3 activation.

The vitamin D3/Hox-A10 pathway supports MafB function during the monocyte differentiation of human CD34+ hemopoietic progenitors

Although a considerable number of reports indicate an involvement of the Hox-A10 gene in the molecular control of hemopoiesis, the conclusions of such studies are quite controversial given that they support, in some cases, a role in the stimulation of stem cell self-renewal and myeloid progenitor expansion, whereas in others they implicate this transcription factor in the induction of monocyte-macrophage differentiation. To clarify this issue, we analyzed the biological effects and the transcriptome changes determined in human primary CD34(+) hemopoietic progenitors by retroviral transduction of a full-length Hox-A10 cDNA. The results obtained clearly indicated that this homeogene is an inducer of monocyte differentiation, at least partly acting through the up-regulation of the MafB gene, recently identified as the master regulator of such a maturation pathway. By using a combined approach based on computational analysis, EMSA experiments, and luciferase assays, we were able to demonstrate the presence of a Hox-A10-binding site in the promoter region of the MafB gene, which suggested the likely molecular mechanism underlying the observed effect. Stimulation of the same cells with the vitamin D(3) monocyte differentiation inducer resulted in a clear increase of Hox-A10 and MafB transcripts, indicating the existence of a precise transactivation cascade involving vitamin D(3) receptor, Hox-A10, and MafB transcription factors. Altogether, these data allow one to conclude that the vitamin D(3)/Hox-A10 pathway supports MafB function during the induction of monocyte differentiation.

NUP98 rearrangements in hematopoietic malignancies: a study of the Groupe Francophone de Cytogénétique Hématologique

The NUP98 gene is fused with 19 different partner genes in various human hematopoietic malignancies. In order to gain additional clinico-hematological data and to identify new partners of NUP98, the Groupe Francophone de Cytogénétique Hématologique (GFCH) collected cases of hematological malignancies where a 11p15 rearrangement was detected. Fluorescence in situ hybridization (FISH) analysis showed that 35% of these patients (23/66) carried a rearrangement of the NUP98 locus. Genes of the HOXA cluster and the nuclear-receptor set domain (NSD) genes were frequently fused to NUP98, mainly in de novo myeloid malignancies whereas the DDX10 and TOP1 genes were equally rearranged in de novo and in therapy-related myeloid proliferations. Involvement of ADD3 and C6ORF80 genes were detected, respectively, in myeloid disorders and in T-cell acute lymphoblastic leukemia (T-ALL), whereas the RAP1GDS1 gene was fused to NUP98 in T-ALL. Three new chromosomal breakpoints: 3q22.1, 7p15 (in a localization distinct from the HOXA locus) and Xq28 were detected in rearrangements with the NUP98 gene locus. The present study as well as a review of the 73 cases previously reported in the literature allowed us to delineate some chromosomal, clinical and molecular features of patients carrying a NUP98 gene rearrangements.