MiR-27a downregulates 14-3-3θ, RUNX1, AF4, and MLL-AF4, crucial drivers of blast transformation in t(4;11) leukemia cells

Cell Biochem Funct. 2022 Oct;40(7):706-717. doi: 10.1002/cbf.3736. Epub 2022 Aug 18.


The chromosomal translocation t(4;11)(q21;q23), a hallmark of an aggressive form of acute lymphoblastic leukemia (ALL), encodes mixed-lineage leukemia (MLL)-AF4 oncogenic chimera that triggers aberrant transcription of genes involved in lymphocyte differentiation, including HOXA9 and MEIS1. The scaffold protein 14-3-3θ, which promotes the binding of MLL-AF4 to the HOXA9 promoter, is a target of MiR-27a, a tumor suppressor in different human leukemia cell types. We herein study the role of MiR-27a in the pathogenesis of t(4;11) ALL. Reverse transcription quantitative PCR (qPCR) reveals that MiR-27a and 14-3-3θ expression is inversely correlated in t(4;11) ALL cell lines; interestingly, MiR-27a relative expression is significantly lower in patients affected by t(4;11) ALL than in patients affected by the less severe t(12;21) leukemia. In t(4;11) leukemia cells, ectopic expression of MiR-27a decreases protein level of 14-3-3θ and of the key transcription factor RUNX1. We show for the first time that MiR-27a also targets AF4 and MLL-AF4; in agreement, MiR-27a overexpression strongly reduces AF4 and MLL-AF4 protein levels in RS4;11 cells. Consequent to AF4 and MLL-AF4 downregulation, MiR-27a overexpression negatively affects transcription of HOXA9 and MEIS1 in different t(4;11) leukemia cell lines. In agreement, we show through chromatin immunoprecipitation experiments that MiR-27a overexpression impairs the binding of MLL-AF4 to the HOXA9 promoter. Lastly, we found that MiR-27a overexpression decreases viability, proliferation, and clonogenicity of t(4;11) cells, whereas it enhances their apoptotic rate. Overall, our study identifies the first microRNAthat strikes in one hit four crucial drivers of blast transformation in t(4;11) leukemia. Therefore, MiR-27a emerges as a new promising therapeutic target for this aggressive and poorly curable form of leukemia.

Keywords: 14-3-3θ; AF4; MLL; MiR-27a; microRNA; t(4;11) acute leukemia; target therapy.

MeSH terms

  • Core Binding Factor Alpha 2 Subunit
  • Humans
  • Lymphocyte Activation
  • MicroRNAs* / genetics
  • MicroRNAs* / metabolism
  • Myeloid-Lymphoid Leukemia Protein / genetics
  • Myeloid-Lymphoid Leukemia Protein / metabolism
  • Oncogene Proteins, Fusion / genetics
  • Oncogene Proteins, Fusion / metabolism
  • Precursor Cell Lymphoblastic Leukemia-Lymphoma* / genetics
  • Precursor Cell Lymphoblastic Leukemia-Lymphoma* / pathology


  • Core Binding Factor Alpha 2 Subunit
  • MLL-AF4 fusion protein, human
  • MicroRNAs
  • Oncogene Proteins, Fusion
  • RUNX1 protein, human
  • Myeloid-Lymphoid Leukemia Protein