Nucleoporin Gene NUP98 Research Articles

Loss of p53 accelerates the complications of myelodysplastic syndrome in a NUP98-HOXD13–driven mouse model

AbstractThe nucleoporin gene NUP98 is fused to several genes including HOXD13 in patients with myelodysplastic syndromes (MDS), acute myeloid leukemia, and chronic myeloid leukemia, blast crisis. Genetically engineered mice that express a NUP98-HOXD13 (NHD13) transgene (Tg) display the phenotypic features of MDS, including cytopenias, bone marrow dysplasia, and transformation to acute leukemia. Here we show that short-term treatment with the p53 inhibitor Pifithrin-α partially and transiently rescued the myeloid and lymphoid abnormalities found in NHD13+ Tg mice, with no improvement in the anemia, while the genetic deletion of 2 alleles of p53 rescued both the myeloid progenitor cell and long-term hematopoietic stem cell compartments. Nonetheless, loss of one or both alleles of p53 did not rescue the MDS phenotype, but instead exacerbated the MDS phenotype and accelerated the development of acute myeloid leukemia. Our studies suggest that while targeting p53 may transiently improve hematopoiesis in MDS, over the long-term, it has detrimental effects, raising caution about abrogating its function to treat the cytopenias that accompany this disease.

Loss of p53 Accelerates the Complications of Myelodysplastic Syndromes (MDS) In the NUP98-HOXD13 Transgenic Mouse Model

Abstract 2804The myelodysplastic syndromes (MDS) are clonal stem cell disorders characterized by ineffective hematopoiesis leading to blood cytopenias and a high rate of progression to acute myelogenous leukemia (AML) (Nimer, 2008). Recent studies implicated an important role for p53 in 5q−MDS, a subtype where haploinsufficiency of the RPS14 ribosomal protein drives the anemia that accompanies this disease (Ebert et al., 2008; Barlow et al., 2010 and Dutt et al., 2011). The elevated level of p53 activity apparently triggers the excessive apoptosis and the dysplastic morphology seen in the erythroid cells of the “5q-mice” that lack one copy of the chromosomal region syntenic to the human 5q region that contains the RPS14 gene (Barlow et al., 2010). Thus, the cytopenias in some patients with MDS may be the result of defective ribosomal biosynthesis, leading to activation of p53 and excessive apoptosis. The nucleoporin gene NUP98 is fused to a number of different genes including HOXD13 by chromosomal translocations that are found in patients with MDS, AML and CML, blast crisis. Genetically engineered mice that express a NUP98-HOXD13 (NHD13) transgene (Tg) display the phenotypic features of MDS, including cytopenias, bone marrow dysplasia, and transformation to acute leukemia (Lin et al., 2005). We obtained these mice and analyzed the hematopoietic stem cells (HSC) and the erythroid compartment and found significantly decreased rps14 mRNA expression in the NHD13+ CD71+Ter119+ cells compared to the WT controls. Furthermore, flow cytometry analysis revealed increased intracellular p53 levels in the NHD13+ Lin−Sca-1+ c-Kit+ (LSK) and CD71+Ter119+ cells. These data suggest that defective rps14 ribosomal protein production and an increased p53 level may contribute to the anemic phenotype in NHD13+ Tg mice. To examine whether inhibition of p53 function can improve the cytopenias of NHD13+ Tg mice, mice were injected with Pifithrin-α (a reversible inhibitor of p53-mediated apoptosis and p53-dependent gene transcription, 2 mg/kg body weight) daily for five weeks. We observed partial rescue of the myeloid and lymphoid lineage differentiation defects, with no improvement in the hemoglobin level. To further investigate whether the presence or absence of p53 affects the MDS or AML phase of NHD13 driven disease, we generated NHD13+p53+/− and NHD13+p53−/− mice. Deletion of one allele of p53 rescues the myeloid progenitor cell compartment, while deletion of both alleles reversed the deficit in both the LSK and the MPP populations that was observed in the NHD13+ Tg mice. The clinically healthy NHD13+p53−/− mice (aged 3 to 5 months) and the NHD13+p53+/− mice (aged from 3 to 7 months) both had more severe leukopenia and anemia than the NHD13+ Tg mice or the WT controls (aged 4 to 7 months). 60% of the NHD13+p53−/− mice and the NHD13+p53+/− mice developed MDS with a median survival of 138 d and 190 d respectively; in contrast 30% of the NHD13+ Tg mice had MDS with a median survival of 236 d. These data indicate that the relative or absolute lack of p53 hastens the development of MDS, and shortens the median survival. Lack of one or two p53 alleles significantly accelerated the development of AML, which in NHD13+p53+/− mice resulting in a median survival of 278 d. However, AML in the NHD13+p53−/− mice is more undifferentiated with a median survival of 133 d, and the NHD13+ Tg mice showed AML with a median survival of 324 d. Taken together, these data demonstrated that the chronic loss one allele or two alleles of p53 does not rescue the MDS phenotype induced by NHD13 fusion gene. Rather it accelerates the development of NHD13 driven MDS and leukemia. Our studies suggest that targeting p53 transiently may temporally improve hematopoiesis in MDS, but over the long term has detrimental effects on hematopoiesis. Disclosures:No relevant conflicts of interest to declare.

Functional analysis of the NUP98-CCDC28A fusion protein

The nucleoporin gene NUP98 is rearranged in more than 27 chromosomal abnormalities observed in childhood and adult, de novo and therapy-related acute leukemias of myeloid and T-lymphoid origins, resulting in the creation of fusion genes and the expression of chimeric proteins. We report here the functional analysis of the NUP98-coiled-coil domain-containing protein 28A (NUP98-CCDC28A) fusion protein, expressed as the consequence of a recurrent t(6;11)(q24.1;p15.5) translocation. To gain insight into the function of the native CCDC28A gene, we collected information on any differential expression of CCDC28A among normal hematologic cell types and within subgroups of acute leukemia. To assess the in vivo effects of the NUP98-CCDC28A fusion, NUP98-CCDC28A or full length CCDC28A were retrovirally transduced into primary murine bone marrow cells and transduced cells were next transplanted into sub-lethally irradiated recipient mice. Our in silico analyses supported a contribution of CCDC28A to discrete stages of murine hematopoietic development. They also suggested selective enrichment of CCDC28A in the French-American-British M6 class of human acute leukemia. Primary murine hematopoietic progenitor cells transduced with NUP98-CCDC28A generated a fully penetrant and transplantable myeloproliferative neoplasm-like myeloid leukemia and induced selective expansion of granulocyte/macrophage progenitors in the bone marrow of transplanted recipients, showing that NUP98-CCDC28A promotes the proliferative capacity and self-renewal potential of myeloid progenitors. In addition, the transformation mediated by NUP98-CCDC28A was not associated with deregulation of the Hoxa-Meis1 pathway, a feature shared by a diverse set of NUP98 fusions. Our results demonstrate that the recurrent NUP98-CCDC28A is an oncogene that induces a rapid and transplantable myeloid neoplasm in recipient mice. They also provide additional evidence for an alternative leukemogenic mechanism for NUP98 oncogenes.

Candidate Genes for Expansion and Transformation of Hematopoietic Stem Cells by NUP98-HOX Fusion Genes

BackgroundHox genes are implicated in hematopoietic stem cell (HSC) regulation as well as in leukemia development through translocation with the nucleoporin gene NUP98. Interestingly, an engineered NUP98-HOXA10 (NA10) fusion can induce a several hundred-fold expansion of HSCs in vitro and NA10 and the AML-associated fusion gene NUP98-HOXD13 (ND13) have a virtually indistinguishable ability to transform myeloid progenitor cells in vitro and to induce leukemia in collaboration with MEIS1 in vivo.Methodology/Principal FindingsThese findings provided a potentially powerful approach to identify key pathways mediating Hox-induced expansion and transformation of HSCs by identifying gene expression changes commonly induced by ND13 and NA10 but not by a NUP98-Hox fusion with a non-DNA binding homedomain mutation (N51S). The gene expression repertoire of purified murine bone marrow Sca-1+Lin- cells transduced with retroviral vectors encoding for these genes was established using the Affymetrix GeneChip MOE430A. Approximately seventy genes were differentially expressed in ND13 and NA10 cells that were significantly changed by both compared to the ND13(N51S) mutant. Intriguingly, several of these potential Hox target genes have been implicated in HSC expansion and self-renewal, including the tyrosine kinase receptor Flt3, the prion protein, Prnp, hepatic leukemia factor, Hlf and Jagged-2, Jag2. Consistent with these results, FLT3, HLF and JAG2 expression correlated with HOX A cluster gene expression in human leukemia samples.ConclusionsIn conclusion this study has identified several novel Hox downstream target genes and provides important new leads to key regulators of the expansion and transformation of hematopoietic stem cells by Hox.

Transplantable cell lines generated with NUP98–Hox fusion genes undergo leukemic progression by Meis1 independent of its binding to DNA

Hox genes have been identified in chromosomal translocations involving the nucleoporin gene NUP98. Though the resulting chimeric proteins directly participate in the development of leukemia, the long latency and monoclonal nature of the disease support the requirement for secondary mutation(s), such as those leading to overexpression of Meis1. Models to identify such events and to study leukemic progression are rare and labor intensive. Herein, we took advantage of the strong transforming potential of NUP98-HOXD13 or NUP98-HOXA10 to establish preleukemic myeloid lines from bone marrow cells that faithfully replicate the first step of Hox-induced leukemogenesis. These lines contain early granulomonocytic progenitors with extensive in vitro self-renewal capacity, short-term myeloid repopulating activity and low propensity for spontaneous leukemic conversion. We exploit such lines to show that Meis1 efficiently induces their leukemic progression and demonstrate a high frequency of preleukemic cells in the cultures. Furthermore, we document that the leukemogenic potential of Meis1 is independent of its direct binding to DNA and likely reflects its ability to increase the repopulating capacity of the preleukemic cells by increasing their self-renewal/proliferative capacity. The availability of lines with repopulating potential and capacity for leukemic conversion should open new avenues for understanding progression of Hox-mediated acute myeloid leukemia.

Redundant Leukemogenicity of NUP98-HOX Fusion Genes in Primary Murine Bone Marrow Cells Correlates with Gene Expression Changes Consistent with Common Key Target Genes.

Several Abd-B HOX genes have been found in translocations with the nucleoporin gene NUP98 in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). We have previously tested both known and engineered NUP98-HOX fusions in the murine bone marrow transplantation model (N. Pineault et al., MCB 24:1907, 2004). Strikingly, an engineered NUP98-HOXA10 (NA10) fusion, not observed in patients, and the AML-associated fusion gene NUP98-HOXD13 (ND13) have a virtually indistinguishable ability to transform myeloid progenitor cells and to induce leukemia in collaboration with MEIS1. Importantly, their transforming ability is lost when the DNA-binding homeodomain is mutated. This functional overlap provides a potentially powerful strategy to identify key genes/pathways mediating HOX-induced leukemias by looking for overlapping gene expression changes induced by different NUP98-HOX fusion genes. 5-FU bone marrow cells were transduced with retroviral vectors encoding for the leukemogenic ND13 or NA10 fusion genes or a non-leukemogenic ND13 gene with a N51S homeodomain mutation or the empty MIG vector. RNA was extracted from transduced GFP+ Sca1+ Lin- cells and linear RNA amplification was performed before the analysis on the Affymetrix GeneChip MOE430. Three independent experiments were conducted and analyzed. Correlation analysis showed a high degree of similarity between ND13 and NA10 in their overall gene expression profiles, compared to the N51S mutant or the MIG control. Validation with real-time quantitative RT-PCR on non-amplified RNA revealed good agreement between the gene array and the PCR, with a tendency for bigger fold-changes with the PCR method. Close to 500 genes were found differentially expressed (changed ≥2-fold vs. MIG ctrl and t-test p-value <0.05) and some 100 of these were changed by both ND13 and NA10 but not by the N51S homeodomain mutant. These genes are strong candidates as direct and/or immediate downstream targets involved in leukemic transformation. Remarkably, among these were genes previously identified as a NUP98 fusion partner in human leukemia (DEAD-box protein, Ddx10), or part of the same family of genes found in NUP98-fusions (Ddx4 and the paired mesoderm homeobox gene, Pmx2). This suggests a possible molecular link in leukemogenicity between HOX- and non-HOX-NUP98 fusions. Other interesting genes that were induced by ND13 and NA10, but not by the N51S homeodomain mutant, were genes previously implicated in leukemia (e.g. Flt3, Evi1) as well as Hox-related genes, such as the Hox cofactor Pbx3 and several Hox A cluster members. Furthermore, approximately one third were ESTs or genes with unknown function. In conclusion, our results document similar changes in gene expression induced by functionally redundant but different NUP98-HOX fusions and should facilitate the identification of common target genes involved in leukemic transformation.

NUP98 Is Fused to PRRX2, a New Homeobox Partner Gene in t(9;11)(q34;p15), in a Therapy-Related Acute Myeloid Leukemia.

The nucleoporin gene NUP98 is known to be rearranged in several recurrent translocations occurring in de novo and therapy-related myelodysplastic syndrome and acute leukemia, in children or adults. All these abnormalities seem to have bad prognosis, thus, it is important to identify NUP98 rearrangements. As other genes (MLL, ETV6, RUNX1, ...), NUP98 may fuse to different partners, often homeobox genes such as HOXA, HOXC, HOXD, PMX1, but also non homeobox genes such as RAP1GSD1, NSD1, NSD3, LEDGF, ADD3, DDX10, and TOP1. The fusion transcript always juxtapose the N-terminal FG repeats of NUP98, required for its docking function, to the C-terminus of the partner gene, which contains the homeodomain in the case of a homeobox partner gene. We identified a t(9;11)(q34.1;p15.5) by conventional cytogenetic analysis, in a 65 years old Caucasian female who developed a t-AML four years after lymphoma treatment. The involvement of NUP98 gene was confirmed by FISH analysis using BAC RP11-120E20 and PAC RP11-1173K1. 3′RACE analysis allowed to identified a novel partner gene, the class II homeobox gene PRRX2 (Paired Related homeobox 2), located on 9q34. The breakpoint occurred in an infrequent breaking region in exon 11 of NUP98, and in exon 2 of PRRX2. The NUP98-PRRX2 fusion transcript was cloned and sequenced, and confirmed by RT-PCR. As its homologue PRRX1 (PMX1), PRRX2 is a DNA-binding transcription factor that is essential for fetal development. PRRX1 has been described to be fused with NUP98 in t(1;11)(q23;p15), but it is the first time PRRX2 is implicated in leukemia, and even in malignancy. Further studies are necessary to confirm the recurrence of this translocation and its prognosis. Furthermore, transformation assays in cells lines and transgenic mice studies would be interesting to understand the leukemogenicity induced by the NUP98-PRRX2 fusion transcript.

NUP98-Topoisomerase I acute myeloid leukemia-associated fusion gene has potent leukemogenic activities independent of an engineered catalytic site mutation

AbstractChromosomal rearrangements of the 11p15 locus have been identified in hematopoietic malignancies, resulting in translocations involving the N-terminal portion of the nucleoporin gene NUP98. Fifteen different fusion partner genes have been identified for NUP98, and more than one half of these are homeobox transcription factors. By contrast, the NUP98 fusion partner in t(11;20) is Topoisomerase I (TOP1), a catalytic enzyme recognized for its key role in relaxing supercoiled DNA. We now show that retrovirally engineered expression of NUP98-TOP1 in murine bone marrow confers a potent in vitro growth advantage and a block in differentiation in hematopoietic precursors, evidenced by a competitive growth advantage in liquid culture, increased replating efficient of colony-forming cells (CFCs), and a marked increase in spleen colony-forming cell output. Moreover, in a murine bone marrow transplantation model, NUP98-TOP1 expression led to a lethal, transplantable leukemia characterized by extremely high white cell counts, splenomegaly, and mild anemia. Strikingly, a mutation to a TOP1 site to inactivate the isomerase activity essentially left unaltered the growth-promoting and leukemogenic effects of NUP98-TOP1. These findings, together with similar biologic effects reported for NUP98-HOX fusions, suggest unexpected, overlapping functions of NUP98 fusion genes, perhaps related to common DNA binding properties. (Blood. 2004;104:1127-1136)

The chromosome translocation t(7;11)(p15;p15) in acute myeloid leukemia results in fusion of the NUP98 gene with a HOXA cluster gene, HOXA13, but not HOXA9.

The nucleoporin gene NUP98 has been reported to be fused to 9 partner genes in hematologic malignancies with 11p15 translocations. The NUP98-HOXA9 fusion gene has been identified in acute myeloid leukemia (AML) and chronic myelogenous leukemia with t(7;11)(p15;p15). We report here a novel NUP98 partner gene, HOXA13, in a patient with de novo AML having t(7;11)(p15;p15). The HOXA13 gene is part of the HOXA cluster genes and contains 2 exons, encoding a protein of 338 amino acids with a homeodomain. The NUP98-HOXA13 fusion protein consists of the N-terminal phenylalanine-glycine repeat motif of NUP98 and the C-terminal homeodomain of HOXA13, similar to the NUP98-HOXA9 fusion protein. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis in various leukemic cell lines showed that the HOXA13 gene was expressed significantly more frequently in acute monocytic leukemic cell lines than in other leukemic cell lines (P = 0.039). HOXA13 and three HOXA cluster genes (A9, A10, A11) located at the 5' end of the HOXA9 gene were frequently expressed in myeloid leukemic cell lines. Our results revealed that t(7;11)(p15;p15) was not a single chromosomal abnormality at the molecular level. The protein encoded by the NUP98-HOXA13 fusion gene is similar to that encoded by NUP98-HOXA9, and the expression pattern of the HOXA13 gene in leukemic cell lines is similar to that of the HOXA9 gene, suggesting that the NUP98-HOXA13 fusion protein may play a role in leukemogenesis through a mechanism similar to that of the NUP98-HOXA9 fusion protein.

The NUP98-HOXD13 fusion gene implicated in human leukemia induces myeloproliferation and blocks early b cell development in murine hematopoiesis

The nucleoporin gene NUP98 (11p15) has been reported to be fused to a number of genes including the homeobox HOX genes A9 and D13 in therapy-related AML. To investigate the role and effects that the fusion gene may have on hematopoiesis and in the development of leukemia, we used the MSCV retrovirus (GFP as a selectable marker) to express the NUP98-HOXD13 cDNA in murine bone marrow (BM). NUP98-HOXD13 (GFP+) transduced BM cells had a 1.8 fold increase (n = 5) in clonogenic colony forming cell numbers in vitro, compared to control GFP+ BM cells. Moreover, they yielded a 20 fold increase in day 12 CFU-S following 1 week in liquid culture. To assess the effect on hematopoiesis in vivo, mice were transplanted (TX) with transduced BM cells (n = 9). BM biopsy and peripheral blood analysis (PB) 12 weeks post-TX revealed a reduced level of circulating B220+ B cells (0.72 vs 2.47 × 106/ml) and a 25 fold reduction in B cell clonogenic progenitors in the BM. Two NUP98-HOXD13 mice sacrificed 18 weeks post-TX for further analysis manifested varying degrees of increased myelopoiesis. One mouse had clear signs of early myeloproliferative syndrome (MPS), including a marked increase in splenic CFC-GM (65 fold) and Gr-1+ cells (4 fold). The myeloproliferation was transplantable and progressive with 2 of 5 secondary mice becoming moribund by 10 weeks post-TX and MPS, as shown by increased PB counts, splenomegaly and myeloid cell infiltration in multiple organs. These results provide direct evidence of the potential of NUP98-HOXD13 to grossly perturb hematopoiesis.

Molecular heterogeneity of the NUP98/HOXA9 fusion transcript in myelodysplastic syndromes associated with t(7;11)(p15;p15)

The reciprocal translocation t(7;11)(p15;p15) has been reported as occurring mainly in acute myelogenous leukaemia (AML) and the acute phase of chronic myelogenous leukaemia (CML). This translocation in AML involves both the nucleoporin gene NUP98 on 11p15 and the homeobox gene HOXA9 on 7p15. The invariant chimaeric NUP98/HOXA9 transcripts are a result of the fact that each breakpoint of the NUP98 and the corresponding breakpoint of the HOXA9 gene cluster occur within the same intron. Only one patient with myelodysplastic syndromes (MDS) carrying this chromosome aberration has been reported, but this study did not involve molecular analysis. We describe two patients with MDS associated with t(7;11): patient 1 was a Japanese man diagnosed with chronic myelomonocytic leukaemia; patient 2 was a Japanese woman with refractory anaemia with excess of blasts in transformation. Within a year both patients developed AML and showed multidrug resistance to chemotherapy. Southern blot analysis showed rearrangements of the NUP98 gene of the two patients and the HOXA9 gene of patient 2. Patient 1 had two types of the novel NUP98/HOXA9 fusion transcripts. Each of them lacked the common 141 bp NUP98 exon which was contained in the NUP98/HOXA9 fusion transcripts detected in patient 2 and the reported AML cases. These data indicated that t(7;11) could determine the development of various myeloid leukaemias and that the resultant chimaeric transcripts are heterogenous.

NUP98 Is Fused to PMX1 Homeobox Gene in Human Acute Myelogenous Leukemia With Chromosome Translocation t(1;11)(q23;p15)

The nucleoporin gene NUP98 was found fused to theHOXA9, HOXD13, or DDX10 genes in human acute myelogenous leukemia (AML) with chromosome translocations t(7;11)(p15;p15), t(2;11)(q35;p15), or inv(11)(p15;q22), respectively. We report here the fusion between the NUP98 gene and another homeobox gene PMX1 in a case of human AML with a t(1;11)(q23;p15) translocation. The chimeric NUP98-PMX1transcript was detected; however, there was no reciprocalPMX1-NUP98 fusion transcript. Like the NUP98-HOXA9fusion, NUP98 and PMX1 were fused in frame and the N-terminal GLFG-rich docking region of the NUP98 and the PMX1 homeodomain were conserved in the NUP98-PMX1 fusion, suggesting that PMX1 homeodomain expression is upregulated and that the fusion protein may act as an oncogenic transcription factor. The fusion to NUP98 results in the addition of the strong transcriptional activation domain located in the N-terminal region of NUP98 to PMX1. These findings suggest that constitutive expression and alteration of the transcriptional activity of the PMX1 homeodomain protein may be critical for myeloid leukemogenesis.

NUP98 Is Fused to PMX1 Homeobox Gene in Human Acute Myelogenous Leukemia With Chromosome Translocation t(1;11)(q23;p15)

AbstractThe nucleoporin gene NUP98 was found fused to theHOXA9, HOXD13, or DDX10 genes in human acute myelogenous leukemia (AML) with chromosome translocations t(7;11)(p15;p15), t(2;11)(q35;p15), or inv(11)(p15;q22), respectively. We report here the fusion between the NUP98 gene and another homeobox gene PMX1 in a case of human AML with a t(1;11)(q23;p15) translocation. The chimeric NUP98-PMX1transcript was detected; however, there was no reciprocalPMX1-NUP98 fusion transcript. Like the NUP98-HOXA9fusion, NUP98 and PMX1 were fused in frame and the N-terminal GLFG-rich docking region of the NUP98 and the PMX1 homeodomain were conserved in the NUP98-PMX1 fusion, suggesting that PMX1 homeodomain expression is upregulated and that the fusion protein may act as an oncogenic transcription factor. The fusion to NUP98 results in the addition of the strong transcriptional activation domain located in the N-terminal region of NUP98 to PMX1. These findings suggest that constitutive expression and alteration of the transcriptional activity of the PMX1 homeodomain protein may be critical for myeloid leukemogenesis.

Low frequency of rearrangements of the homeobox geneHOXA9/t(7;11) in adult acute myeloid leukemia

Translocation (7;11)(p15;p15) is uncommon in acute myeloid leukemia (AML) and may have a predilection to occur in Asian patients. It results in a reciprocal fusion of the homeobox gene HOXA9 and the nucleoporin gene NUP98. To ascertain the molecular features and the clinicopathological and prognostic significance of t(7;11)(p15;p15), 208 adult Chinese patients with AML were screened by Southern blot analysis with an HOXA9 cDNA probe and reverse transcription-polymerase chain reaction for NUP98/HOXA9. Three cases were found to have rearrangement of the HOXA9 gene. Two cases were found to have an NUP98/HOXA9 fusion transcript, with a breakpoint at NUP98 different from that previously described. The remaining case had no rearrangement of NUP98, nor was NUP98/HOXA9 detected. All positive cases had refractory AML with poor treatment outcome. In conclusion, t(7;11)/HOXA9 rearrangement was a rare event (3/208, 1.5%) in AML, even in a population where it was considered to be more prevalent. Two breakpoints in NUP98 may occur, and this is of importance in the design of primers to amplify t(7;11).

Low frequency of rearrangements of the homeobox gene HOXA9/t(7;11) in adult acute myeloid leukemia

Translocation (7;11)(p15;p15) is uncommon in acute myeloid leukemia (AML) and may have a predilection to occur in Asian patients. It results in a reciprocal fusion of the homeobox gene HOXA9 and the nucleoporin gene NUP98. To ascertain the molecular features and the clinicopathological and prognostic significance of t(7;11)(p15;p15), 208 adult Chinese patients with AML were screened by Southern blot analysis with an HOXA9 cDNA probe and reverse transcription–polymerase chain reaction for NUP98/HOXA9. Three cases were found to have rearrangement of the HOXA9 gene. Two cases were found to have an NUP98/HOXA9 fusion transcript, with a breakpoint at NUP98 different from that previously described. The remaining case had no rearrangement of NUP98, nor was NUP98/HOXA9 detected. All positive cases had refractory AML with poor treatment outcome. In conclusion, t(7;11)/HOXA9 rearrangement was a rare event (3/208, 1.5%) in AML, even in a population where it was considered to be more prevalent. Two breakpoints in NUP98 may occur, and this is of importance in the design of primers to amplify t(7;11). Genes Chromosomes Cancer 25:70–74, 1999. © 1999 Wiley-Liss, Inc.

Fusion of the nucleoporin gene NUP98 to HOXA9 by the chromosome translocation t(7;11)(p15;p15) in human myeloid leukaemia.

Expression of Hoxa7 and Hoxa9 is activated by proviral integration in BXH2 murine myeloid leukaemias. This result, combined with the mapping of the HOXA locus to human chromosome 7p15, suggested that one of the HOXA genes might be involved in the t(7;11)(p15;p15) translocation found in some human myeloid leukaemia patients. Here we show that in three patients with t(7;11), the chromosome rearrangement creates a genomic fusion between the HOXA9 gene and the nucleoporin gene NUP98 on chromosome 11p15. The translocation produces an invariant chimaeric NUP98/HOXA9 transcript containing the amino terminal half of NUP98 fused in frame to HOXA9. These studies identify HOXA9 as an important human myeloid leukaemia gene and suggest an important role for nucleoporins in human myeloid leukaemia given that a second nucleoporin, NUP214, has also been implicated in human myeloid leukaemia.