Biological and functional characterization of the fusion gene NUP98-HOXA9 in Acute myeloid leukemia: new therapeutic approaches

• Autores: Ana del Río Machín
• Directores de la Tesis: Juan Cruz Cigudosa García (dir. tes.)
• Lectura: En la Universidad Autónoma de Madrid ( España ) en 2014
• Idioma: inglés
• Tribunal Calificador de la Tesis: Antonia Fernández Peralta (presid.), Margarita Sanchez Beato Gomez (secret.), Francesc Solé Ristol (voc.), María Jose Calasanz Abínzano (voc.), Javier Benítez Ortiz (voc.)
• Materias:
  • Química
    • Bioquímica
      • Biología molecular
  • Ciencias médicas
    • Ciencias clínicas
      • Oncología
• Enlaces
  • Tesis en acceso abierto en: Biblos-e Archivo
• Resumen

  • The chromosomal translocation t(7;11)(p15, p15), which results in the oncogenic fusion protein NUP98-HOXA9 (NH), is a rare but recurrent oncogenic event in AML that is associated with very poor prognosis and short overall survival. The molecular processes triggered by NH are poorly understood, even though a potential role as an aberrant transcription factor has been proposed. Moreover, there is no specific therapy for these patients; they are treated with ineffective standard chemotherapy regimens. Therefore, our main objective has been to generate human cellular models that constitutively express the chimera protein, to study its role in leukemic transformation and expand the search for new therapeutic targets that enable the treatment of the patients with this chromosomal translocation in a targeted manner. Using these models, we have described for the first time the DNA binding sites of NH, most of which are enhancers that regulate the expression of genes involved in the development of AML. In particular, we have shown that the direct overexpression of the complex MEIS1-HOXA9-PBX3, a key element in the onset of leukemia that is driven by other chromosome rearrangements in AML, is also one of the actionable pathogenic mechanisms induced by NH. We have demonstrated that the peptide HXR9, an inhibitor of the interaction HOXA9-PBX3, was indeed able of selectively kill cells expressing NH. Furthermore, we have observed that, in a model of human hematopoietic progenitors expressing NH, and also in patients with the chromosomal translocation, the fusion protein was able to activate and repress the expression of their target genes. We have also shown that the interaction of NH with p300 (transcriptional activator) and HDAC1 (transcriptional inhibitor), could explain this activator-repressor role of the fusion protein. Supporting this hypothesis, we have found a dramatic inhibitory effect on hHP-NH viability after the treatment with LBH589 (an HDAC inhibitor) which allowed us to consider its therapeutic potential for patients carrying the translocation. Finally, in an attempt to understand the contribution of each of the two NH moieties to the regulation of gene expression, we found that a third of the target genes of NH are common to HOXA9 wt. In addition, ChIP-seq results for NUP98 wt revealed the potential role of this nucleoporin in regulating hematopoietic differentiation. This newly role of NUP98 is likely to contribute to a better understanding of how NH, as well as other leukemic fusion proteins in which NUP98 is involved, works.

    To summarize, these results have allowed us to characterize some of the most relevant pathogenic mechanisms induced by NH and to identify new therapeutic targets that have been studied in our model, yielding very promising results.